alternate test procedure (atp) validation study report for

Alternate Test Procedure (ATP) Validation Study Report

For

The Measurement of Drinking Water Turbidity up to 10

NTU Using the Candidate Lovibond Turbidity Methods,

Represented by the PTV 1000, PTV 2000, and PTV 6000

Turbidimeters

Candidate ATP Turbidity Methods:

1. The Continuous Measurement of Drinking Water Turbidity using the

Lovibond White Light LED Method


Lovibond 660-nm LED Method


Lovibond 6000 Laser Method

December 20, 2016

Tintometer Incorporated

6456 Parkland Drive

Sarasota, FL 34243

All Correspondence Should be Directed to:

Michael Sadar


2108 Midpoint Drive, STE 1

Fort Collins, CO 80525

970-682-8148

[email protected]

mailto:[email protected]

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Table of Contents

1.0 Background ................................................................................................................................... 2

1.1 Method Justification .................................................................................................................. 3

1.2 Method Equivalency ................................................................................................................. 5

1.3 Analytes .................................................................................................................................... 7

2.0 Study Implementation .................................................................................................................. 7

2.1 Study Schedule .......................................................................................................................... 9

2.2 Sample Collection ..................................................................................................................... 9

2.3 Types of Analysis Performed .................................................................................................. 10

2.4 Study Plan Deviations ............................................................................................................. 10

3.0 Method Procedure and Data ........................................................................................................ 11

3.1 Validation Study Demonstration Data .................................................................................... 14

3.1.1 Calibration ........................................................................................................................ 15

3.1.2 Initial Demonstration of Capability ................................................................................. 16

The Fort Collins Test Site ..................................................................................................... 16

Precision and Accuracy Data for the Three Candidates and Reference Methods ................. 19

Accuracy (Bias) of the Lovibond WL Led Method. ............................................................. 22

Accuracy (Bias) of the Lovibond 660-nm LED Method ...................................................... 24

Accuracy (Bias) of the Lovibond 6000 Laser Method .......................................................... 25

The Binney South Platte Comparability Test Site ................................................................ 26

The San Patricio MWD Comparability Test Site .................................................................. 31

Limit of Detection (LOD) ..................................................................................................... 36

3.1.3 Quality Controls ............................................................................................................... 37

3.1.4 Precision and Accuracy .................................................................................................... 40

3.2 Holding Time / Storage Stability ............................................................................................ 40

4.0 Data Analysis and Discussion ..................................................................................................... 40

Data Analysis ........................................................................................................................ 41

Data comparison between the Lovibond 660-nm LED method and the EPA approved

Method 10133 ....................................................................................................................... 44

Data comparison between the Lovibond 6000 Laser Method and the EPA approved

Method 10133 ....................................................................................................................... 45

5.0 Conclusions ................................................................................................................................. 48

Appendix A Validation Study Plan……………………………………………………..……...49-69

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Appendix B.1 Lovibond White Light LED Turbidimeter Method………………………..…70-82

Appendix B.2 Lovibond 660-nm LED Method………………………………………………83-94

Appendix B.3 Lovibond 6000 Laser Method……………………………………..….……..95-107

1.0 Background

These three candidate methods are for the on-line (continuous) measurement of turbidity. Specifically, these

methods have been designed to measure low-level turbidity in water, between 0.01 and 10 NTU. The methods are

designed to measure the turbidity of the sample either in a static state or within a defined sample flow rate between

30 and 150 ml/minute. These candidate methods address the common interferences in turbidity, which included

stray light, bubbles, optical surface condensation, and particle settling; accomplished through the designed

instrumentation described in the candidate methods.

Tintometer Incorporated is a water analytics company that operates under the brand Lovibond. Tintometer

developed new on-line turbidimeters with the specific application to deliver accurate turbidity measurements in the

area of drinking water production, and more specifically filtration performance within a drinking water plant.

Specifically, the turbidimeters were designed for the monitoring of waters with turbidity less than 10 Nephelometric

Turbidity Units (NTU’s). Tintometer has worked diligently to ensure that these turbidimeters will reliably deliver

accurate turbidity assays over time.

This ATP validation study covered three new candidate methods for low level turbidity measurement.

1. The Continuous Measurement of Drinking Water Turbidity using the Lovibond White Light LED

Method. The representative instrument discussed herein is the PTV 1000 Turbidimeter.

2. The Continuous Measurement of Drinking Water Turbidity using the Lovibond 660-nm LED Method.

The representative instrument discussed herein is the PTV 2000 Turbidimeter.

3. The Continuous Measurement of Drinking Water Turbidity using the Lovibond 6000 Laser Method.

The representative instrument discussed herein is the PTV 6000 Turbidimeter.

The candidate methods are listed separately, and differ only with respect to the incident light source. This is noted

in the title of each candidate method. These three methods use solid state light sources, two of which are light

emitting diode (LED) sources and the third which is a laser diode light source. These light sources have extended

lifetimes and provide optical stability when compared to historical methods (e.g. USEPA Method 180.1) that use

incandescent light sources. This translates into improved measurement reliability and reduced instrument

maintenance over the lifetime of the instrument.

All other aspects of these three candidate methods and their representative instrumentation are identical. This

includes measurement geometry (detector angle, detector view angle), sample volume, sample flow rates, sample

transport through the instrument, measurement view volume, calibration, quality control verification, turbidity

measurement determination (i.e. measurement algorithms), and data handling. Denoted collectively (where

appropriate), they are referred to as the PTV 1000/2000/6000. This helps to simplify the understanding of the

differences between these technologies and other approved historical turbidity methods.

The ATP study involved the comparison of measurements between the three candidate PTV 1000/2000/6000

instruments and the EPA approved Method 10133. Method 10133 is a laser-based turbidity method, designed for

measurements between 0.010 and 5.00 NTU. The fully compliant instrument to Method 10133 is the Hach

FilterTrak 660 Laser Nephelometer. This is referred to herein as the reference instrument and the Method 10133 is

referred to as the reference method.

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The study involved the measurement of three different waters with the candidates and reference instruments. Two

of the waters were filter effluent waters. A third water was tap water that was filtered to remove any residual

particles above 0.05 micron. The two effluent waters were monitored by the candidate methods and test instruments

to collect data to for method comparability. The filtered tap water was spiked with formazin to generate several

defined turbidity levels that covered the range of turbidity in this ATP. This spike data was used to determine the

precision, bias and linearity for the candidate and reference methods over the denoted range from about 0.01 up to

10 NTU.

1.1 Method Justification

The candidate ATP turbidity methods were compared to the approved Hach Method 10133, which is also known as

the FilterTrak 660 method (denoted herein as Method 10133). The Hach Filtertrak 660 laser nephelometer is cited

as the instrument in full compliance with Method 10133 and is the reference method throughout this study.

These candidate turbidimeters utilize numerous state-of-the art technological advancements coupled with proven

design criteria that have been utilized by the Drinking Water Plant (DWP) community and its regulatory partners

over the past several decades. Ultimately, these technologies provide the ability to rapidly interpret turbidity

measurement data which is critical to the mitigation of any risks associated with the breakdown in the water

treatment process.

As noted above, the turbidimeter versions are identical in their design with the exception of the light source. One

version, the PTV 1000 utilizes a white light (WL) LED, a source that is essentially the same as the incident light

source used in the EPA approved Swan Turbidiwell Method and is designed to mimic the light source used in

Method 180.1 with respect to spectral output. The second version, the PTV 2000 contains a red light emitting LED

that emits light at peak intensity within the visible spectrum at a wavelength between 650 and 670nm, (typically at

660 nm). The spectral output from this source is comparable to the Mitchell Method M5271 and Hach Method

10133. The third light source is a 685-nm laser diode source with a spectral output that is comparable to Hach

method 10133. These three light sources provide several advantages over the historical tungsten filament light

sources used in Method 180.1, which are discussed in detail later in this document.

Table 1 provides a summary of the advantages these candidate methods have with respect to the reference method,

and also EPA Method 180.1. When comparing to Method 180.1, this is with respect to the light source only and was

included in this table because is the most common monitoring method in drinking water. Additional candidate

methods’ (and instruments) advantages separate from the incident light sources are expressed at the bottom part of

the table and are compared to the reference method to support their respective justification.

Table 1 – Summary of the design features for the proposed EPA methods on turbidity and the advantages over the

reference Method 10133 and EPA Method 180.1

Feature Advantage over Method 10133 Advantage over Method 180.1

White Light (WL)

LED (Incident Light

Optics) and the

660-nm Red LED

WL LED is more sensitive to small particles than

the reference - Peak response between 400-600

nm; Source was sensitive to a broad range of

particle sizes.

Solid State – Low drift; low output temperature

dependence of LED light source. Source will last

life of the instrument

Long Life (10 years life expectancy). 180.1

sources last 1-2 years and will have spectral shifts

as they age.

Heated optics for all light sources in the

candidate methods. Eliminates instability and

erroneous measurements due to condensation.

Solid state light sources such as LED’s and laser

diodes do not generate heat and are more

susceptible to condensation effects. Reference

was susceptible to condensation effects on the

180.1 beam was divergent and results in higher

stray light.

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incident light optics, thereby increasing chance

of measurement error.

Sensitivity was near equivalence to 180.1. Peak

response between 400-600 nm; sensitive to a broad

range of particle sizes.

Heated optics; Eliminates instability and erroneous

measurements due to condensation. Some 180.1

designs generate heat that was sufficient to prevent

condensation effects on the incident light optics.

Others designs can experience condensation

problems.

Incident light source monitor detector;

compensates for LED drift over time and

temperature. Reference instrument has no known

drift compensation for its light source.

Incident light source monitor detector;

Compensates for LED drift over time and

temperature. Existing Method 180.1 instruments

have no known drift compensation.

The peak response of the 660-nm reduces

interference due to dissolved organics and sample

color.

The 660-nm spectral bandwidth was narrowed,

thereby reducing stray light and improving the

limit of detection.

The 660-nm LED spectral bandwidth was narrowed

when compared to Method 180.1, thereby reducing

stray light and improving the limit of detection of

the candidate method.

685-nm Laser

The incident light is a highly collimated beam of

high energy light and its small diameter reduces

stray light and improves the limit of detection when

compared to Method 180.1.

The small diameter incident light beam in the

candidate method was sensitive to individual

particles that may penetrate a filter as its run time

progresses toward backwash.

Advantages of the PTV 1000/2000/6000 over the Reference Turbidimeter (Method 10133)

Beam Dump

A stray light trap that absorbs incident beam energy after passing through measurement

chamber and reduces stray light. The beam dump of this design is not a feature in the

reference method.

Scattered Light Detector

The candidate methods detector incorporates a controlled aperture angle. This improves

intra-instrument consistency in detection. The reference method does not have this feature.

The candidate detector was heated and does not have air spaces between the sample and

detector surface. This eliminated instability and error due to condensation. The reference

instrument does not have this feature.

Short total path length of 5.5 cm yields a highly linear response over the regulatory range of

interest (0-10 NTU) and simplifies the calibration protocols. This allows the calibration to

be performed using a turbidity standard that is higher in value (e.g. 5.0 NTU) and thus,

easier to prepare and administer. The reference method requires the preparation of a lower

turbidity standard (0.80 NTU) which is more difficult to prepare and administer. The

published range of the candidate’s methods was up to 10 NTU and up to 5 NTU for the

reference method.

Large collection angle; improves the limit of detection. The candidate’s methods have a

large defined collection angle. The reference instrument does not have this feature.

The Turbidimeter body

Reduced Volume – The candidate instruments have a volume of 275 ml versus the

reference instrument’s volume of 1100 ml. This improves response time to a turbidity

event, reduces the possibility of sample settling within the instrument, minimizes sample

usage and minimizes calibrant usage. The reduced volume of the candidate’s instruments

allow for a reduction in the volume of calibrant and verification standards required by a

factor of at least 3. This reduces the amount of cost to calibrate, verify and with any

associated disposal fees.

Integrated bubble trap – The candidate instruments has an integrated bubble trap that is

removable without tools, is front accessible, is easy to clean (less time and no special

cleaning tools) and has low sample retention. The reference instrument has a larger bubble

trap with numerous tight corners, making it difficult and time consuming to clean.

The candidate turbidimeter body is designed not to have any tight corners. This facilitates

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efficient draining of the body and bubble trap and allows for more rapid cleaning of the

instrument. The reference instrument has many tight corners, takes a long time to drain and

is difficult to clean. Poorly cleaned instruments will lead to calibration, verification, and

measurement error.

The candidate instrument bodies have polished fluid handling surfaces which are designed

to reduce scale, fouling and bubble formation. The reference instrument does not have this

feature.

The candidate measurement chamber has a “V” shaped form factor that is designed to direct

light reflections away from the detector, thereby reducing stray light. This shape also

reduces particle settling that could result in positive measurement interference. The

reference instrument does not have this “V” shaped feature.

The candidate instrument has an integrated sample flow indicator. The indicator confirms

sample flow through the measurement chamber of the instrument. Alarms and warnings

can be set for either high or low flow conditions. The reference instrument does not have

this feature.

The candidate’s instruments contain multiple internal weirs. These ensure consistent

sample throughput and homogeneity and increased instrument robustness. The reference

instrument has a single overflow weir.

The candidate’s measurement chamber was designed for optimized sample handling. The

sample temperature does not change as it passes through the instrument, thereby

minimizing the chance that the sample composition changes and this reduces bubble

formation.

Complete Measurement System

(Body and Measurement

module)

The linear response of the candidate instruments covers the range of 0-10 NTU. The

published linear response range of the reference instrument is 0-5000 mNTU (0 -5 NTU).

This linear range allows for robust calibration protocols.

The candidate instruments have a self-alignment feature comprised of a magnetic

positioning system that ensures proper alignment of the measurement module onto the flow

body. The reference instrument does not have this feature and can easily become

misaligned, thereby causing a non-measurement condition or erroneous measurements.

The candidate instruments contain redundant user interfaces (smart device and

touchscreen). This accelerates the ability of an operator to respond to a turbidity event and

facilitated the ability to perform maintenance and quality control. The reference instrument

can only be interfaced using a controller that was directly connected to the instrument.

The candidate instruments contain both redundant data and meta data storage. The

reference instrument does not have meta-data storage capability.

The candidate instruments contained both wired (USB) and secure wireless (Bluetooth)

communication for operation of the instrument (User interface) and data transmission. The

reference instrument does not have these features.

The candidate instruments possess multiple outputs for both digital and analog

communication streams (i.e. Modbus, 4-20) mA). The reference instrument requires the

use of a controller to perform communications.

The candidate instruments utilize the latest available component technologies that increase

reliability and robustness when compared to aged technologies such as the reference

instrument.

1.2 Method Equivalency

The approved reference Method 10133 quality control (QC) acceptance criteria was only defined in the linear

calibration range (section 9.2.2) in which two calibration verification standards were prepared and measured. The

criteria were for the instrument to measure within ±0.025 NTU of each of these standards. One standard was in the

0.050 to 0.200 NTU range and the other was in the 0.700 to 0.900 NTU range. Although the range of the method

extends to 5.00 NTU, no other QC data was provided in Method 10133. The candidate methods required the

measurement of a QCS standard in the measurement range of interest. The pass/fail criteria were to measure within

10 percent of the theoretical value of the QCS or within 0.04 NTU for the Lovibond White Light LED Method or

0.030 for the Lovibond 660-nm LED or 6000 Laser Methods.

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The pass/fail criteria for the candidate methods are based on the capability to prepare a calibration or verification

standard at an assigned value below 1 NTU. Below this turbidity level, it is typical for the manufacturer of

calibration standards to assign error as a fixed value. This error value is typically ± of 0.03 NTU to ± 0.04 NTU.

For example, a standard that is commercially prepared to 0.30 NTU nominal can have an accuracy spec of ± 0.03

NTU (which is ±10% in this example). In the range below 1 NTU, the combination of preparing a standard and then

administrating that standard in a calibration or verification can be very difficult. This is due to the impact of

interferences that result from the turbidity of the dilution water, particle contamination, bubble interferences, the

stability over time, and the technique of preparation of the standard for measurement, which can propagate together.

This is why most manufacturers who prepare standards will express the uncertainty of a given standard using a fixed

error value at turbidities below 1 NTU. Further, the preparation of standards below the value of about 0.10 NTU

should be avoided due to the increasing magnitudes of these interferences. Turbidity standards above the value of

about 1 NTU have better stability and the interferences are not as severe and therefore will have an uncertainty that

is typically a percentage of the stated value and is usually in the range of ±2 to ±10 percent of the nominal value of

the standard.

When performing QC on a method, the challenge is to be able to accurately prepare the standards. The error of the

standard typically dictates the pass/fail criteria for a given instrument, which was the case in the demonstration of

capability of these methods. Using the 0.025 NTU criteria from the reference method, the demonstration of linearity,

and ultimately the linear calibration range was assessed. The candidate methods delivered results on 8 turbidities in

the range of 0 to 1.00 NTU and for all candidate instruments, the difference between the delivered results and the

theoretical values were less than the ±0.025 criteria stated by the reference method. Above 1 NTU, a comparison

between the reference and candidate instruments showed differences that exceeded the ±0.025 NTU criteria for both,

but none of these instruments showed a difference that was greater than 7 percent versus the theoretical value of the

turbidity level. If using a percentage based pass/fail criteria of 10%, which is common practice for regulatory

verifications and is applicable above 1 NTU, the instruments passed the verification criteria. Additional linearity

discussions that support method equivalency are in the data and results sections of this report.

In the method performance section of Method 10133, percent recovery and precision data was provided on six

different turbidity levels that covered the range of 0 to 1.00 NTU. The percent recoveries ranged from 98 to 125

percent. The three candidate instruments were each tested on 8 different turbidities that covered this 0 to 1 NTU

range. Their combined percent recoveries ranged from 99 to 104 percent over this same range (Note all information

in this section data was separated out with respect to each method, which was contained in the data and results

sections). Between 1 and 10 NTU, the percent recoveries for the three candidate instruments ranged from 93 to 100

percent and the reference instrument ranged from 97 to 101 percent. Analysis of variance (ANOVA) statistics were

run on the percent recovery data between the three candidates and reference instruments for all the formazin spikes

used for precision and bias. These statistics showed F values were less than the F-critical values, indicating

statistically that the differences in the percent recoveries were not statistically significant.

In the method performance section of Method 10133, the precision was measured on water samples at 0.108, 0.027

and 0.0213 NTU and delivered standard deviations that were 0.025, 0.0011, and 0.0056 NTU respectively. It was

not known if these statistics were derived under flowing conditions. This ATP study derived standard deviations for

the spiked turbidity levels using the on-line or flowing condition, which arguably was a more valid approach. In this

ATP study, standard deviations for the candidate and reference instruments were derived and averaged within the

ranges of 0 to 0.100 NTU, 0.100 to 1.00 NTU and 1.00 to 10 NTU. The 0 to 0.100 NTU range reported standard

deviations that were below 0.001 NTU for both the candidate and reference methods. The 0.10 to 1.0 NTU range

reported standard deviations that were between 0.004 and 0.005 NTU for the candidate methods and 0.003 NTU for

the reference instruments. Above 1.0 NTU, the candidate methods delivered higher standard deviations that ranged

between 0.016 and 0.048 NTU and the reference instrument delivered an averaged standard deviation of 0.014 NTU.

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Quality control samples were run on prior to and at the completion of data collection for the precision and bias data.

All instruments passed the QC criteria, which was based on QCS samples with theoretical turbidities of 0.31 and 1.0

NTU.

In summary the three candidate methods showed equivalency to the approved reference Method 10133 over the

range of 0.00 to 1.0 NTU, which was supported by the passing of the QCS samples and the ANOVA statistics on the

percent recovery data. The reference method does not contain performance data above 1 NTU, but this ATP study

did collect additional data on all methods up to 10 NTU.

1.3 Analytes

Turbidity is essentially the measurement of aggregate light scatter that was caused by all materials within a sample

that are capable of scattering light in a direction that reached the 90-degree detector. The nature of this “analyte”

turbidity does not lend itself to the CAS registry. However, turbidity calibrations are all traced to formazin

standards which have proved to be universally accepted standards across the world for many decades. Historically,

formazin has been used as the accepted surrogate for turbidity, and historically used to derive performance

specifications for instruments and to evaluate method performance. Formazin was used in this study to derive

precision, bias, and linearity data for the three candidates and reference methods. The formazin polymer itself does

not have a CAS registration number, but the components that are used to synthesize formazin stock standards do.

These components are listed below:

• Hydrazine Sulfate – CAS 10034-93-2

• Hexamethylenetetramine CAS 100-97-0

• Water, Filtered and Deionized CAS 7732-18-5

2.0 Study Implementation

This ATP study was conducted at three different test sites. The study was organized and managed by Tintometer

Incorporated’s research and development center that was located in Fort Collins, Colorado. The coordinator of the

study was Mike Sadar. He was assisted by the Tintometer R&D staff and by staff at the different drinking water test

sites in setting up the test sites and with data collection activities.

The test sites involved two drinking water plants (DWP) and the Fort Collins R&D facility. These sites are referred

to herein as the Fort Collins Filtered Tap Water Site (Fort Collins), the Aurora Binney South Platte Site (Binney

South Platte), and the San Patricio Municipal Water District (San Pat MWD) site. The source water from all three

sites was surface water that was treated by a variety of techniques prior to the filtration step. These details of each

were described separately.

The Fort Collins site was at the Tintometer Inc. R&D facility and it had access to city tap water. The tap water was

produced by the City of Fort Collins Water Treatment Plant. The surface water source originates from mountain

snowmelt runoff and was stored in a nearby reservoir (Horsetooth Reservoir). This raw water was treated using a

conventional treatment train that included flocculation, sedimentation, and dual-media anthracite/sand filtration.

This tap water at the Fort Collins site was further filtered through a size exclusion membrane with nominal pore size

of 0.05 um prior to entering the test panel. The purpose of this secondary filtration step was to ensure the removal

of all particulate materials and ensure a consistent particle-free baseline that would be suitable for multiple spikes.

This allowed the precision and bias (spike recovery) data to be collected at this site. The details the test setup is

provided in Section 6 of the appended study plan (Appendix A).

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The Fort Collins site was selected to perform the precision and bias for the ATP study for several reasons. The three

candidate methods were continuous analysis methods and required adequate sample flow and pressure to ensure

consistent flow rates for the duration of the study. The tap water provided the required flow and pressures to ensure

all turbidity spikes would be accurate and consistent over the duration of the testing. In addition to the candidate and

reference instrumentation, a high precision peristaltic pump and an analytical balance were needed to carry out the

spikes (please refer to the appended study plan). NIST traceable weights were used to validate the accuracy of the

balance. The theoretical values of each spike ultimately trace to the accuracy of this balance. The testing was

conducted by the coordinator of the study, and assisted by other Tintometer R&D personnel.

The Binney South Platte site was located southeast of the Denver, Colorado metropolitan area. The raw water was

surface water from the South Platte River drainage and was characterized with high levels of total dissolved solids

and micro-pollutants such as pharmaceutical residuals. The raw water was treated through a multibarrier process that

included riverbank filtration, aquifer recharge and recovery, precipitative softening, ultraviolet light coupled with

advanced peroxide oxidation, biological activated carbon filtration and activated carbon adsorption. The filtration

step was through dual media filtration and the sample tap for this study was on the filter effluent water. The water

plant was commissioned in 2010 and had a treatment capacity of 50 million gallons per day. Mr. Kevin Linder,

Supervisor of Operations and Maintenance for the Binney water plant was the main contact person at this plant. Mr.

Linder delegated his instrumentation engineer to assist Tintometer in setting up the test site. This included

providing the sample taps and drains, power and the work area for the study. Tintometer also signed a memorandum

of understanding with the Binney facility that there would be no financial gain or loss to either entity as a result of

this testing. Thus, no compensation was paid to the Binney facility in relation to this ATP. Tintometer promised to

deliver a copy of the study results to Binney for their review.

The Binney South Platte site was selected for several reasons. First, the raw water was highly compromised with

high total dissolved solids. A large percentage of the raw water was made up of discharge from a permitted

wastewater plant upstream of its intakes. Second, the plant was a member of the Partnership for Safe Drinking

Water and the plant’s management consistently evaluates new technologies. This provided the basis for the

invitation to test at this facility. Last, the treatment train had been offline for several months to install two new filter

units. The plant had recently come on-line but was not in an optimized state of operation. The plant contacts

encouraged the study coordinator to move up the test timeline for the method comparison evaluation to ensure

observance of changes in the filter effluent turbidity levels. Study data covered more than three compete filtration

cycles (ripening, run and backwash), and variation in the filter effluent turbidity levels were observed.

The San Pat MWD site was located on the Southeast Texas coast north of Corpus Christi, Texas. The raw water was

surface water from the Nueces River Basin. The water was treated with flocculation and followed by sedimentation.

The settled water was then forced through Pall Microza™ membranes, which served as physical barrier to particles,

with a nominal pore size less than 0.1 micron. The membrane effluent was subject to regulatory monitoring for

turbidity.

The San Pat MWD site was selected primarily because it would subject the candidate and reference methods to

challenging environmental and measurement conditions. At the time this study was conducted, the raw water

temperature was 32 C (90F). The humidity was 100 percent which were prime conditions for condensation

formation. The membrane filtration process involves the use of pressure to force the water through the membrane.

Sample that passed through the membrane was subject to a significant decrease in pressure that resulted in

outgassing. This challenged the ability of the candidate turbidimeters to remove bubbles from the samples.

The primary contact at San Pat MWD was Mr. Jake Krumnow, who is supervisor of operations and maintenance.

Mr. Krumnow delegated resources to help set up the test site, they provided the sample tap and drain, power and

space for the equipment. The staff oversaw the study and San Pat MWD management has requested a copy of the

study data after the completion of this study. Participation in the study by San Pat MWD was wholly voluntary and

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Tintometer Inc. was able to provide the staff with a detailed overview of the three candidate instruments. No

compensation was provided to the San Pat MWD facility for hosting this portion of the study.

The membrane effluent from each membrane rack was collected into a combined effluent line. This line was tapped

and served as the sample line for the three candidates and reference instruments in this study. Because the sample

was membrane effluent, there were no expected turbidity excursions. To generate some movement in the turbidity,

the study plan called for the injection of settled water into the filtrate water for a defined period of time. This

required the precision peristaltic pump (used at the Fort Collins site) to inject the sample. The turbidity of the settled

water was about 5 NTU, which was measured on a 2100AN turbidimeter. Two different injection rates were

performed to generate two turbidity spikes. The spikes were of a short duration, but long enough to provide

evidence of response and comparability by the three candidate and reference instruments.

The two drinking water plant matrices were used to provide comparability with respect to each of the candidate

instrument’s ability to track the reference turbidimeter. The goal of each site was to collect at least 8 hours of

continuous run time, which was exceeded. Data from these sites was broken down into approximately 8-hour blocks

of time and also into a separate data block that was dedicated to evaluate the injected turbidity spikes. Last, the

entire data set was analyzed and was ultimately reported with respect to comparability. The comparability between

each of the candidate instruments to the reference instrument was expressed as the net difference in turbidity

between each. This was discussed in detail in the data and results sections.

2.1 Study Schedule

The study plan commenced in April 2016 with an initial visit to EPA office of water ATP group to better understand

the ATP process. This was followed by method and study plan development. The data collection study took place

between July 15 and July 28, 2016. A breakdown of this phase was provided in Table 2.

Table 2 – The Lovibond Turbidity ATP – Details on Data Collection at the Different Study Sites

Dates Location Details

July 15-18, 2016 Binney South Platte

Site

July 15: Set up the instruments, calibrate, run QC. July 15-18 – Data

collection. July 18: Run short term spikes, final QC, take down instruments.

July 18-20, 2016 Fort Collins Site July 18: Set Up Instruments and allow to run. July19: calibrate and run QC.

July 19: Run 10 spikes to collect precision, bias, and linearity data. This

cumulated with final QC after all spikes were complete.

July 26-28, 2016 San Pat MWD Site July 26 – Travel and set up instruments and allow to run overnight. July 27:

Calibrate and run QC. July 27-28 collect data and run short term spikes. July

28: Final QC and take down instruments.

In Section 4 of the study plan (Appendix A) the initial schedule was to collect the precision and bias data first.

However a pump failure near the beginning of the spiking occurred and several of the spikes had to be terminated.

It was decided that this test would have to be repeated after the Binney South Platte site testing was completed. In

order to meet the Binney South Platte scheduled plan to host their portion of this ATP comparability study, we

moved to this site which became the first site of data collection. At the completion of this study, the instrumentation

was promptly relocated back to the Fort Collins Site and the formazin turbidity spike study was performed. This

was then followed by testing at the San Pat MWD site, the final site for this study.

2.2 Sample Collection

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This ATP study was for on-line turbidity instrumentation. Therefore, samples continuously flow through the

instruments and do not require collection or holding times in the traditional sense. However, sampling was a very

important part of the study to ensure representative tracking and response times between the three candidate and

reference instruments. To ensure this was correct, the sample flowed from its tap to a manifold that split it into

equal streams, with one stream leading to each instrument in the study. The length of each sample line from the

manifold to each instrument was the same. Sample flow rates were then set to the middle of the manufacturer’s

suggested sample flow range. The candidate’s flow rates were about 70 ml/minute and the reference’s flow rate was

about 330 ml/minute. The overall flow rate to all the instruments had to exceed the sum of the flow rates to

individual instruments to ensure no instrument was starved of sample. The study plan contains renderings of the test

setup for all the sites, which included the splitting of the sample to the test instruments.

Prior to the study, testing was successfully performed on both the candidate and reference instruments to confirm

that variations in flow did not have an impact on the turbidity results. Both designs measure at atmosphere and are

of an overflow weir design. The overflow weir design compensates for any fluctuations or changes in flow, as it

continuously maintains the same volume of sample within the measurement chamber.

2.3 Types of Analysis Performed

The analysis of turbidity was continuously performed by the candidate and reference instruments, of which all were

on-line turbidity instruments. The turbidity data was collected concurrently for all instruments, which included the

three candidate method instruments and the reference method instrument. All instruments were capable of

performing their measurements at a frequency of once per second. However, this could challenge the data logging

capabilities of the reference instrument, so the data logging frequency was set to once every 15 seconds.

Turbidity data was collected on three waters. The study plan required a minimum of 8-hours of data collection at

each DWP site. The two DWP sites primarily had data collected for much longer than this period and the data was

statistically analyzed to 8-hour segments, and the entire data set.

The Fort Collins site included a shorter period of data collection time. The analysis started with the defining of the

baseline for the filtered tap water, which was the blank, since the tap water was pushed through a filter was through

a pore size smaller than 0.05-micron, essentially producing particle free water. This baseline establishment was

followed by ten successive spikes of turbidity using formazin. Formazin was the primary standard for all turbidity

methods and was generally used in the industry and in the regulatory community as the standard to calibrate and

evaluate method performance. The entire time to perform the baseline and all spikes was 7 hours.

The candidate turbidimeters were identical with the exception of the light source. Their operation, maintenance,

calibration and QC protocols were identical throughout this study. This presented uniqueness of the study overall

because the same sample was simultaneously analyzed by four different light sources. The differences in response

with respect to these light sources could be scrutinized with respect of their ability to detect and quantify turbidity

levels in the range of 0-10 NTU and more specifically, at turbidity levels below 1 NTU.

2.4 Study Plan Deviations

The intent of the data collection phase of this ATP was to follow the validation plan and for the majority of this plan,

it was extensively followed. There were three exceptions of deviations from the validation plan. The first deviation

was during the spike study at the Fort Collins Site. When the first spike was initiated, we noticed that the

characteristic ramp up to the theoretical value was very slow and unstable. The cause was traced to the wrong

connection to the injection port for the spiking of the turbidity standards. In order to generate accurate turbidities of

11

spikes; the entire filtered flow stream must be injected with the prepared turbidity standard. The test stand had two

injection ports. One injection port impacted only a portion of the sample stream. If this port was used, there was no

means available to accurately measure the flow through that portion of the system. The correct port injected the

entire filtered water stream and it could be measured accurately, which was necessary to be able to calculate the

theoretical value of the formazin spikes. This error was immediately noticed and was corrected. The data, which

was for a very short span of time (July 20, 2016 from 950-1011) was identified and then ignored. It was called out

in Figure 1. The spike data, which was graphed, contained a section that was circled and was omitted from

calculations. Upon correction, the first spike was repeated. Subsequent spikes beyond this were as per the

validation plan.

The validation plan called for the use of the FilterTrak 660 as the reference instrument. At the Binney South Platte

Site, we also had installed a 1720E as an additional sensor on the water. Data from that instrument was also logged

and was plotted graphically in Figures 3 and 4. However, the data was not used for any of the calculations or

analysis and was included in these two graphs to illustrate its comparative response to the three candidates and

reference instruments in this study. The installation of this instrument at the Binney South Platte Site had no impact

on the results that were generated at this site.

The timeline with respect to the order of the validation plan changed. The plan had the precision and bias data being

collected first, followed by the Binney South Platte and then the San Pat MWD sites. However, the Binney South

Platte was moved to the front of the schedule at their request. The change in the schedule was within a few days of

the original plan and thus, the impact from environmental conditions was minimal; and likely had no impact on the

overall scope or outcome of this ATP validation study.

Last, the validation plan called for the use of one QCS sample after calibration and at the end of data collection and

its value would be 1.0 NTU. Instead two QCS samples were prepared and run after each calibration and at the end

of data collection at each test site. One QCS sample was at 1.0 NTU and the other was either at 0.3 or 0.6 NTU. This

had no impact on the overall scope or outcome of this ATP validation study.

3.0 Method Procedure and Data

The Lovibond Process Turbidity ATP validation plan was designed to concurrently collect comparability data for

the three candidate turbidity methods and compare to the approved reference method (Method 10133). It was

mentioned that the difference in the three candidate methods was only with the type of light source used and all

other sections of these methods (and their representative instruments) was identical, with one exception. That was

with respect to the data in the method performance section (Section 13). The three candidate methods are appended

in this report as Appendix B.1, B.2 and B.3; for the Lovibond White Light LED Method first, followed by the

Lovibond 660-nm LED Method, and ending Lovibond 6000 Laser Method respectively. The data that was collected

from this validation study was implemented into these three proposed methods. All data was highlighted in purple

text and was primarily located in Section 13.

Section 1.1 of this report, Method Justification, provided comparison and contrasts between each of the candidate

methods (and representative instrumentation) and reference Method 10133 (and the FilterTrak 660). The comparison

was from a component and feature perspective, and included the mandated design criteria. This is summarized in

Table 1 of this report. It was important to note that some of the comparisons utilize certain technologies that

ultimately become features that may have otherwise been restricted in previous instrument designs. For example,

when a collimated light source such as an LED or laser was used, its characteristics allowed for a reduction in

sample measurement space because it required less optics to retain beam columniation through the measurement

12

cell. This for example, can lead to smaller sample volumes, which translates to reduced sample usage, reduced

calibrant usage and reduced generated reagent waste. It was common to see secondary and tertiary impacts from a

simple difference in between methods. Table 3 separately compares each of the three candidate and reference

methods to each other section by section. For each section, a brief comparison and contrast to the reference method

was provided. If the cells are merged, this indicated the comparability was across all of the candidate methods. The

most significant differences between the methods will be with respect to Section 6, Equipment.

Table 3 – Compare and Contrast Between the Candidate and Reference Methods in this Turbidity ATP.

Section Reference Description (or

specification)

Lovibond White

Light LED

Method

Lovibond 660 nm

LED Method

Lovibond 6000 Laser

Method

1.0 Scope and

Application

Range was 0-5.0 NTU Range was 0-10 NTU

2.0 Summary of

Method

Method was based on light scattered by the sample under defined conditions to intensity of light scattered

by a reference standard solution. The reference standards are formazin or a stabilized version of formazin

for calibration and verification.

2.0 Summary of

Method – Dry

Verification

Modules

A dry verification device,

specific for the instrument

was cited in the method.

The candidate methods do not reference a dry verification device for

verification. However, such devices are available and have been tested.

3.0 Definitions

Definitions were the same for all three candidate methods. Definitions were essentially the same for both

the reference and the candidate methods except for the terms Calibration Verification Standards

(CALVER) and MSDS, both in the reference are synonymous to the Secondary Calibration Standards

(SCAL) and SDS respectively in the candidate methods.

4.0 Interferences. The candidate methods incorporate all the stated interferences in the reference method, plus the candidate

methods include the interference from internal surface reflections (i.e. stray light).

5.0 Safety The candidate methods incorporate all the stated safety concerns that are in the reference method, plus

additional safety concerns on Hydrazine sulfate.

6.0 Equipment

The Turbidimeter shall consist of a nephelometer with a light source for illuminating the sample and one or

more photo-detectors to measure the amount of scattered light at a right angle to the incident beam. This

was the same for the three candidate and the reference methods.

All methods correlate scattered light signal, detected at a 90-degree angle, to turbidity, which was defined

by standard reference turbidity suspensions.

6. Optics – Incident

Light Source

Laser diode Operated at

660±30 nm. This will

provide sensitivity to the

presence of individual

particles that flow within

the analysis volume of the

instrument.

LED emitting white

light in the visible

spectrum between 380

and 780-nm. This

method may show

enhanced sensitivity to

the smallest particle

size when compared to

other methods.

LED with a peak

emitting wavelength

between 650 and

670-nm. This

method has the most

stringent

wavelength criteria,

which can be

reflected in intra-

instrument

comparability.

Laser Diode with a peak

emitting center wavelength

between 650 and 690-nm.

Like the reference method,

this method will provide

sensitivity to the presence

of individual particles that

flow with the analysis

volume of the instrument.

6. Peak spectral

Response of System

The detector must

encompass the entire

spectral output of the

incident light source,

which is optimally at 660-

nm

The spectral peak

response shall be

between 400 and 600

nm.

The spectral peak

response shall be

between 600 and

700 nm.

The spectral peak response

shall be between 600 and

700 nm.

6. Distance

traversed by the

incident and

scattered light

This distance was not to exceed 10-cm in all methods.

6. Parallelism of

incident light path

within the

measurement

volume.

No divergence in

parallelism and

convergence must not

exceed 1.5 degrees.

No divergence in parallelism and divergence was not to exceed 1 degree

13

6. Detector position

Centered at 90 and not to

exceed ±2.5 degrees from

90.

Centered at 90 degrees ± 1.5 degrees relative to the incident light beam.

6. Detector receive

angle

None was specified in the

reference method.

Scattered light detector/receiver shall be at a subtended angle between 20 and

30 degrees from the center point of the measurement volume. The provided a

defined view volume for the detector.

6. Detector type

Shall be a photomultiplier

tube, which is very

expensive.

Detector is a silicone photodiode with a spectral sensitivity that encompasses

the spectral output of the incident light source. The detector signal is

amplified and converted to a turbidity signal. Only the performance

characteristics that include: 1) no airgap between the sample and the surface

of the detector, which minimizes stray light; 2) spectral sensitivity must

encompass the spectral output of the incident light source.

6. Stray Light

Design

All the methods essentially state that the overall optical/instrument design shall be to minimize stray light

so it will not cause significant error in the determination of turbidity in the sample.

6. Stray Light Trap None was specified in the

reference method

All candidate methods state that un-scattered incident shall pass into a light

trap that encompasses the entire diameter of this incident light beam.

6. Fiber Optic

Cables

Method allows the use of

fiber optic cables to

transport scattered light.

There was not a reference to fiber optic cables in this method.

6. Algorithm Usage

No algorithm type is

specified in the reference

method.

All candidate methods require the algorithm that converts light scatter signal

to turbidity readings to be a linear-based algorithm (e.g. y=mx+b). This

guarantees a linear calibration range for the instrument, which was possible

by the incorporation of the optical configuration of the instrument.

6. Sample deaerator No aerator is specified in

the reference method

The candidate methods incorporate the required use of a sample deaerator to

remove entrained air from the system.

6. Instrument Drift

All methods include a specification that the turbidimeter shall be free from significant drift after a short

warm-up period. The use of solid state light sources help to reduce drift. The candidate instruments all use

a monitor detector and feedback mechanism to correct for any drift that would occur over time.

6. Instrument

Sensitivity

Capable of detecting

turbidity difference of

0.001 NTU or less.



0.010 NTU or less.


turbidity difference

of 0.010 NTU or

less.



0.005 NTU or less.

6. Instrument

Specification

The FT660 is an

instrument that meets the

criteria of Method 10133

the reference method.

The Lovibond PTV

1000 is an instrument

that meets the criteria

of the Lovibond White

Light LED Method

The Lovibond PTV

2000 is an

instrument that

meets the criteria of

the Lovibond 660-

nm LED Method

The Lovibond PTV 6000 is

an instrument that meets the

criteria of the Lovibond

6600 Laser Method

7.0 Reagents and

Standards

Instructions were provided to produce reagent water that would have a residual turbidity less than 0.03

NTU.

7.2 Stock Standard

Suspension

The reference method

prepares 400 NTU

formazin Solution

The three candidate methods prepare a 4000 NTU formazin stock solution.

This method of preparation was in alignment with the methods used in the

preparation of commercially available formazin stock solutions.

Gravimetrically, the masses of the raw materials used to prepare the stock

suspensions are equivalent for the candidate and reference methods.

7.3 Instrument

calibration

Standards


provides instructions on

the preparation of

dilutions to prepare the

calibration standard. The

reference method

recommends the use of

stabilized formazin

standards.

The candidate methods provide instructions to prepare a working stock

solution at 40 NTU. The methods then instruct to dilute this solution with

Class A glassware and reagent turbidity free water to the final standard

value(S). The candidate methods also recommend the use of stabilized

formazin standards

Section 8.1 Sample

Collection

All methods state that the methods for on-line analysis and sample collection, cooling, and preservation

does not apply.

Section 8.2

Instrument Setup


references the

manufacturer’s

installation manual. It

provides some additional

The candidate methods reference the manufacturer’s instructions for

installation and startup. This was kept open in case new technologies or

techniques can be implemented over time.

14

guidance that pertains to

individual instrument

features.

Section 9 Quality

Control

The reference and candidate methods have very similar quality control programs. They have the same

introductory section and very similar initial demonstration of performance. The reference the use of quality

control samples (QCS) to verify the linear calibration range (LCR). The reference method instructs to

prepare two standards and have 0.025 NTU criteria as pass/fail. The candidate methods have a requirement

to use a blank and three standards for the LCR determination, with a pass/fail criterion of ±10 percent.

Section 9.2.3

Quality Control

Sample

The reference and candidate methods are very similar. Both use a single QCS to confirm the LCR on at

least a quarterly basis. The pass fail criteria on the candidate methods are stated at ±10% or ±0.040 NTU.

There was no pass fail criteria statement for the QCS in the reference method.

Section 10

Calibration

The reference methods

state to calibrate

according to the

manufacturer’s

instructions.

The candidate methods state to calibrate according to the manufacturer’s

instructions. In addition, these methods require cleaning and maintenance

prior to calibration. These methods require calibration under the same

ambient conditions as measurement. The instructions also require calibration

in the instrument itself (no calibration cylinders), which insures proper

maintenance of the instrument.

Section 10

Calibration

Verification

The candidate and reference methods instruct to perform verification in the measurement range of interest.

The candidate and reference methods reference wet or solid standards (dry verification standards) for use in

verification.

Section 11

Procedure


references the instrument

manual with emphasis to

maintain consistent

sample flow.

The candidate methods reference the manufacturer’s instructions and

emphasize the importance to maintain consistent sample flow. These

methods recommended the installation of a rotometer to eliminate

fluctuations in sample flow rate. The candidate methods also emphasize the

need to maintain constant sample temperature.

Section 12 Data

Analysis and

Calculations

The reference and candidate methods instruct to report to the nearest 0.01 NTU or 10 mNTU. Above 1

NTU, the candidate methods provide additional reporting criteria.

Section 13 Method

Performance


reports precision and bias

on 5 spike levels between

0 and 0.65 NTU.

The candidate methods provide precision and bias on 10 spike levels between

0 and 10 NTU, with 8 of the spikes below 1 NTU. The results in section 13

for each of the candidate methods are discussed in the Data Analysis section

of this report. The candidate methods also have a final section to check the

precision and bias on a routine basis at the frequency required for regulatory

compliance. The reference method does not include this section.

Section 14 Pollution

Prevention

The reference and candidate methods are the same. In addition, the reference method includes a citation on

waste reduction.

Section 15 Waste

Management

The reference and candidate methods essentially have the same section with regards to waste management.

Section 16

References

The reference method has

its own set of references.

The candidate methods have the same set of references that are different from

the reference method.

Section 17 Tables

and Validation Data

This section does not exist

in the reference method.

The validation data

wholly contained in

section 13.

The candidate methods contain their unique precision and percent recovery

tables for each method.

3.1 Validation Study Demonstration Data

This validation study was designed to concurrently demonstrate the performance of the three candidate methods to

the reference method. This performance was in concurrence across the three study sites. The study called for

precision and bias determination to be performed at the Fort Collins site and this will be discussed first. The other

two waters, the Binney South Platte and the San Patricio MWD site will follow respectively.

For each test site, a graph of the data was presented. These graphs represented all data from the start to the stop

times of the study. No points were excluded from any graphs. The two drinking water plant studies also had a short

15

spiking session, in which water upstream from the filtration step was spiked to into the effluent to generate turbidity

movement. For these spiking sessions, a second graph was generated that zoomed in on the spikes.

The data presented in this section will be summary data copied from Microsoft Office Excel (Excel) workbooks. All

the calculations are found in worksheets (spreadsheets) that are part of a given workbook. Each test site has a

dedicated workbook and an explanation for each spreadsheet inside a respective workbook was provided. The

explanation of each spreadsheet was intended to provide the needed guidance to navigate through the calculations

that were applied to deliver the final results for each test site. These explanations will be further explained in the

discussion of each demonstration data section (sections 3.1.2 through 3.1.4).

In order to maintain consistency within this section, the validation demonstration data was presented in tables, along

with a discussion of that table. The demonstration data was ordered accordingly.

1. Presentation of the data graphically, that represented the three candidate methods and the reference

method.

2. Reference to the spreadsheets in the Excel workbook used to generate the precision, bias and linearity data.

(Table 4)

3. Summary of the spike response data for all the methods in this validation study. (Table 5)

4. Summary of the precision for all the methods in this validation study (Table 6).

5. Data and respective summary on the accuracy or bias (Percent Recovery) for the Lovibond White Light

LED Method (Table 7).

6. Data and summary on the accuracy or bias (Percent Recovery) for the Lovibond 660-nm LED Method

(Table 8)

7. Data and summary on the accuracy or bias (Percent Recovery) for the Lovibond 6000 Laser Method (Table

9).

8. Comparability results for the three candidate methods and the reference method at the Binney South Platte

test site (Table11)

9. Comparability results for the different candidate methods and the reference method at the San Pat MWD

membrane test site (Table13)

10. Limit of Detection discussion and analysis (Table 14).

3.1.1 Calibration

Calibration was performed at each test site after the instruments were installed and running for several hours. The

same procedures were performed for calibration at each site. Calibration was performed using the instructions

provided by the instrument manuals for the three candidates and the reference methods. An overview of each is

provided herein.

The calibration procedure for the three candidate methods required the preparation of a 5.01 NTU calibration

standard. The standard was set to this value because of the turbidity of the dilution water (water filtered through a

0.02 um filter yields a turbidity of about 0.01 NTU). A 1-liter volume of standard was prepared by diluting 1.25 ml

of a 4000 NTU standard to 1.00 liters total, using a Class A glass volumetric flask. The 1-liter volume was

sufficient to calibrate the three candidate instruments concurrently.

The 1.25 ml pipette was a high resolution micro-pipette with manufacturer-certified calibration accuracy to within

0.5%. The dispensation volume of the pipette was further checked by pipetting 1.25 ml of water onto a high

resolution balance (measured to the nearest 0.0001 g). The temperature correction for the density of water was

applied. The approach balance confirmed the accuracy of the pipette’s dispensation.

16

Once prepared, a small aliquot of sample was taken from the flask and measured on the laboratory turbidimeter, a

2100AN. This instrument had been calibrated prior to the study. The sample measurement had to be within 2

percent of the theoretical value, which was the error budget for the laboratory turbidimeter.

Immediately prior to calibration each candidate instrument was drained and then rinsed with a liter of turbidity free

water. It was then allowed to drain before commencing with the calibration. The standard was directly introduced

into the body of each of the candidate instruments. After introduction of the standard, the measurement module was

then replaced onto the respective turbidimeter. The instruments then counted down one minute to allow for any

bubbles to dissipate from the standard. The live measurements were displayed during this time, which became

stable as the time passed. Once the displayed values were stable, the calibration was confirmed and written into the

firmware of each (candidate) instrument.

The calibration of the reference instrument was performed according to the instructions in the reference instrument

manual. The calibration standard was an 810 mNTU standard, prepared by diluting 200-ul of 4000 NTU stock

standard solution to a final volume of 1.00 Liter in a Class A volumetric flask. Consistent with the preparation the

calibration standards for the candidate instruments, the pipet accuracy was certified to 0.5 percent and was

confirmed through the dispensation of water at that volume onto a high resolution balance. In addition, a small

aliquot of the standard was taken and measured the same 2100AN turbidimeter used to measure the other calibration

standards. The standard measured within 2% of the theoretical value of 810 mNTU.

The calibration was then performed on the reference turbidimeter according to the manufacturer’s instructions. We

did make an effort to thoroughly clean the instrument and then rinse it was several liters of turbidity free water prior

to the calibration. The calibrated instrument gain was within pre-established limits for the reference instrument (this

was controlled by its software).

To confirm calibration accuracy, two QCS standards were prepared and run on the three candidates and the

reference instruments. The standards were prepared at 1.0 NTU and 0.31 NTU for two of the test sites and a 0.61

NTU standard was prepared instead of the 0.3 NTU at one site (Binney South Platte Site). Taking into the account

of the dilution water, the standard was adjusted accordingly, making the 1.0 standard a 1.01 and the 0.3 standard a

theoretical value of 0.31 NTU. The instruments must measure within 10% or 0.030 NTU of the theoretical value of

each standard to pass QC for the PTV 2000 and 6000 turbidimeters and within 0.040 NTU for the PTV 1000

turbidimeter. These QCS standards were prepared before and at the conclusion of data collection at each site.

Each Excel workbook contains a spreadsheet titled “Quality Assurance”. The information on the preparation and

measurement of calibration standards and QCS standards and the results respectively was included on the “Quality

Assurance” page.

3.1.2 Initial Demonstration of Capability

The Fort Collins Test Site

The initial demonstration of capability, in terms of precision, bias, and linearity was performed at the Fort Collins

site. The validation plan was designed to test the three candidates and the reference methods concurrently on

surrogate turbidity spikes of formazin. The study plan was designed to perform all spikes in an on-line condition so

the demonstration of capability was under realistic operating conditions. Figure 1 was a summary graph of the

spikes involved in this study.

17

Figure 1- Spike response graph for the three candidate method technologies and the reference method over the turbidity

range of 0-10 NTU.

In Figure 1 the legend is at the bottom of the graph, and it identifies the reference and candidate turbidimeters. The

response to each spike is represented on the y-axis and was a log scale. The log scale is used because the spikes

cover three decades of measurement. The time scale is on the x-axis and as the study plan describes, the study starts

with an establishment of the turbidity free baseline, which is then followed by 10 successive spikes of increasing

turbidity. The portion of the data run that was subject to having the wrong injection port is circled and this data was

omitted from the study (please see section 2.4 Study Plan Deviations). Figure 1 provides an overview demonstrating

the instruments, at their set flow rates respond with near equivalence to the reference on each of the spikes. This is

consistent across all of the turbidity spikes at this site.

Figure 2 is a summary graph for all of the spike responses for the three candidate and reference instruments. The

legend at the bottom identifies the candidate and reference instruments. The y-axis is the theoretical turbidity of

each spike. The x-axis is the instrument response to each spike. Both axes cover three decades of turbidity response

and are on a log-log scale to best illustrate the comparability at each turbidity level. The importance of this graph

was that it summarizes the responses over the entire test range of 0-10 NTU for the three candidate and reference

instruments and it illustrates the impact of stray light at the lowest turbidity levels tested. It is a visual comparison

of the significance of stray light at these low levels.

18

Figure 2 - Spike Response charts, on log-log scale for the candidate and reference technologies. The deviation from

linearity at the lower part of the range is the stray light of each technology.

In reference to Figure 2, the stray light was indicated by a positive deviation from linearity at the bottom of the

measurement range. The reference instrument had very little stray light. The PTV 1000, which was the White Light

LED method had the highest stray light, which would be expected since it was the polychromatic light source. The

PTV 2000 and PTV 6000, which had near monochromatic light sources that have very low stray light, which were

within 2-3 mNTU of the reference instrument.

To address the high stray light of the PTV 1000 white light method, this method has a procedure that will allow the

subtraction of the blank value for the turbidity free sample water, which will be applicable for the measurement of

samples below 0.10 NTU.

The Excel workbook that contain the precision and bias data is titled “Ft Collins Filt Tap P&B Test Site.xlsx”. This

workbook is used to deliver the precision and bias tables that are listed later in this section. The derivation of all the

data is through the formulas contained in the spreadsheets from this workbook. A breakdown of the Excel

workbook is for each spreadsheet. From left to right, the spreadsheets are sorted as follows: Exec Summary,

Reporting, Checklist, Quality Assurance, Injection Summary, Raw Data, Fzn Spike Resp & Recovery Data, Spike

Response Graph, Response Summary Graph, ANOVA Single Factor, and Photos. Table 4 contains a description of

each of these spreadsheets and how they were related to the data in this validation report. Note: with respect to these

workbooks, a spreadsheet, worksheet or page is synonymous.

19

Table 4 – A Description of the Excel Workbook From the Fort Collins Test Site for Precision and Bias

Determination

Excel Page

Description

Exec Summary This is the Executive Summary of the Study. It briefly describes the study, the results and the

conclusions. The results and conclusions are mirrored into this validation report.

Reporting The reporting page contains the final tables that provide the side-by-side comparison between each

of the three candidate methods and the reference method. The data in these tables originate in the

Fzn Spike Resp & Recovery Data spreadsheet. The active cells on this spreadsheet are at the

bottom to categorize the data into specific turbidity ranges (e.g. 0 to 0.100 NTU, 0.100 to 1.00 NTU,

and 1.00 to 10 NTU). At the bottom of this page is a summary that includes a description on how

the tables are generated. The limit of detection calculations are on the reporting page.

Checklist This is a checklist to help the site coordinators insure all the details that pertain to the setup,

collection of data and QC are performed. Most of the details are discussed in Section 7 of the

validation plan.

Quality

Assurance

This spreadsheet contains information and data that pertains to the calibration and QC for the study

site.

Injection

Summary

This spreadsheet contains the details that relate to each injection. It includes the start and stop times

of the injection, the beginning and end masses of the standards that were injected, and flow volume

measurements. This sheet contains the calculations that are used to derive the theoretical turbidities

for each of the spikes, which are used for percent recovery (accuracy) calculations.

Raw Data Raw Data – This spreadsheet contains the original raw data from the study. The date/time are in the

first column, followed by the data from the reference instrument in column B, the PTV 2000 Red

LED in Column C, the PTV 1000 WL LED in Column D, followed by the PTV 6000 Laser in

Column E. This raw data overlap the actual study data from a time perspective in that it contains

data prior to calibration.

Fzn Spike Resp &

Recovery Data

This is the most important spreadsheet in the Excel workbook with respect to the precision

and bias derivations. Raw data that is from the applicable blocks of time that is logged from the

background and spikes is copied into this page (Columns A-E are the same headings). This data is

then segmented into each spike, which is statistically analyzed to generate the average, standard

deviation and RSD. These statistics are highlighted in green. Simply scroll down Columns A-E to

see the segments from where these statistical operations are applied. These calculated values are

then copied and pasted(as values) into the tables that are just to the right of column E (Columns H-

O, Rows 4-38) The tables on this page are labelled as follows: Table 1 contains the averaged value

of the response for each instrument on each spike. The bottom of Table 1 contains the least squares

analysis for linearity and the assessment of accuracy over the turbidity range for the three candidate

and reference instruments. Table 2 contains the precision data for each of the spikes. Tables 3

through 7 contain the percent recovery calculations for the reference instrument (Table 3), the PTV

2000 Red LED (Table 4), the PTV 1000 WL LED (Table 5), and the PTV 6000 Laser (Table 6).

Tables 4-7 contain both blank corrected and non-blank corrected percent recovery tables. The data

in Tables 4-7 is the data that are in the tables on the Reporting spreadsheet.

Spike Response

Graph

This is the summary graph that covers the initial baseline (blank) derivation and the responses to

each of the ten spikes. It is pasted into the validation report as Figure 1.

Response

Summary Graph

This summary graph is derived from Table 1 on the “Fzn Spike Resp & Recovery Data” page and is

pasted into the validation report as Figure 2.

ANOVA Single

Factor

This page contains the ANOVA analysis of the different spike recovery tables that are generated on

the “Fzn Spike Resp & Recovery Data” page. The ANOVA analysis is based on columns of data.

The ANOVA calculations are on this page.

Photos This page contains embedded photographs that were taken during this portion of the study. Most of

the photographs are with respect to the calibration and QC portion of the validation study.

Precision and Accuracy Data for the Three Candidates and Reference Methods

For each instrument in this study, the accuracy data was generated through a calculation of the instrument turbidity

response relative to the theoretical turbidity for a given spike. The theoretical value of the spike takes into the

account the combination of molecular scatter (turbidity) and fluorescence effects of the blank solution, so all data

was blank corrected.

20

The data collection started with the determination of the turbidity free baseline (the blank) and followed with

collection of data from each of the turbidity spikes over the test range of 0-10 NTU. A total of 10 spikes were

performed, from the lowest turbidity to the highest turbidity. A total of 3 spikes were in the range of 0 to 0.100

NTU, 4 spikes between 0.100 and 1.00 NTU, and three spikes between 1.00 and 10.0 NTU. For each spike, the

instruments were first allowed to respond to the increase in turbidity until a stabilized condition was observed. Once

stabilized, the instruments continued to collect measurement data on that spike until a total of 60 consecutive

measurements were logged. Statistics were then performed on these 60 measurements for each instrument, which

included the average, standard deviation and relative standard deviation. The averages are provided in Table 5 and

the standard deviations are provided in Table 6. The data from Table 5 was used to generate the percent recoveries

for each of the three candidate methods and the reference method. The data in Table 6, the precision data, was used

to provide the summarized precision statements that were provided in each of the three candidates and reference

methods.

The baseline collection was performed after the QC when the instruments became stable, which indicated that all the

QC standards were completely flushed from the instruments. The instruments then ran until a minimum of 60

measurements were collected, and actually 80 measurements were collected and used to determine the baseline

values. In process analytics, baseline establishment is extremely important that it is determined accurately, so

additional values improves the probability that this is correct. During the spikes, we set a more rigorous collection

protocol in which the last 60 measurements of a given spike were used to determine the average response for each

instrument.

At the bottom of Table 5 least squares correlations are performed between the theoretical turbidity and the given

instrument response for each of the instruments in this study. A perfect correlation, characterized with a slope and r-

squared value equal to exactly 1.000 would result when all the measured values are equal to their corresponding

theoretical values for each data pair. The slopes for the three candidate methods are all within 1.5 % of this

theoretical value of 1.000 and are also within 2 percent of the slope from the reference instrument. The correlation

coefficients are derived between the measured and theoretical responses for each of the three candidates and the

reference instrument. In all cases, the r-squared values are better than 0.999. This demonstrated high and

acceptable linearity over the turbidity test range of 0 to 10 NTU.

This analysis of the slope and correlation coefficient for each instrument is important as it demonstrates the

calibration for each candidate method is to adjust a linear based algorithm. This confirms that a 1-point calibration

is valid over the stated measurement range of 0 -10 NTU. Further, this demonstrates the high linearity of the three

candidates’ methods (and instruments) allows for QC validation using a single standard within this stated range of

measurement. Note that the three candidate methods still utilized two QCS standards (instead of one) to validate the

linear calibration range (LCR) of the method as insurance for data validity.

Data from Table 5 is used to generate the percent recoveries for the candidate methods separately. This data is

contained in Tables 7-9.

Table 5: Averaged Response for Each Turbidity Spike and the Analysis of Linearity for the Three Candidates and Reference

Methods

Spike

Description

Stable

Measurement

Time Range

Theoretical

Turbidity

in Sample

in NTU

Theoretical

Turbidity of

Spike in NTU

FT660

Reference -

in NTU

PTV2000

Red 660 Test

- NTU

PTV 1000

WL Test -

NTU

PTV 6000 685

Laser Test -

NTU

Initial

Baseline 911 - 947 0.007 0.000 0.010 0.013 0.024 0.012

2.01 NTU at

4 RPM 948 - 1033 0.021 0.014 0.025 0.027 0.040 0.027

21

2.01 NTU at

8 RPM 1034 - 1111 0.035 0.028 0.039 0.042 0.054 0.041

2.01 NTU at

16 RPM 1112 - 1146 0.067 0.060 0.070 0.074 0.086 0.072

16.0 NTU at

4 RPM 1147- 1218 0.117 0.110 0.123 0.124 0.138 0.123

16.0 NTU at

8 RPM 1219 - 1251 0.232 0.225 0.243 0.245 0.259 0.242

134 NTU at

2 RPM 1252 - 1324 0.561 0.554 0.569 0.565 0.588 0.566

134 NTU at

4 RPM 1325 - 1411 0.928 0.921 0.941 0.931 0.964 0.927

134 NTU at

8 RPM 1412 - 1455 1.902 1.895 1.938 1.870 1.953 1.897

800 NTU at

2 RPM 1456 - 1530 3.575 3.568 3.473 3.356 3.468 3.378

800 NTU at

6 RPM 1531 - 1602 9.383 9.376 9.482 9.317 9.460 9.431

Slope vs

Theoretical 0.9933 1.0129 0.9974 1.0006

% Accuracy -0.6723 1.2893 -0.2567 0.0624

Correlation

Coefficient 0.99972 0.99969 0.99963 0.99963

% Linearity

(100% is

Perfect) 99.97 99.97 99.96 99.96

In turbidity it is common to determine accuracy over a stated range using the approach provided in Table 5. The

reason is that the chance of a given standard being prepared with a significant level of uncertainty is high at low

turbidity levels (<1.0 NTU). This becomes more significant at even lower levels. Using a least squares fit between

theoretical and measured, an accuracy value over a given range can be provided. This approach works if it is known

that the measurement algorithm is linear based. In technologies where the algorithm is not linear based, there may

be a better approach to estimate accuracy.

Table 6 contains the precision data that was generated at the Fort Collins test site. All precision values in Table 6

are as the standard deviations and the units are in NTU. The table contains the precision for each instrument that

represents its respective candidate method and also contains the precision for the for the reference method

instrument. The precision was calculated from the same 60 measurements collected on each turbidity spike that was

used to generate the averaged response.

The bottom of Table 6 categorizes the precision data into specific turbidity ranges. These ranges are 0-0.100, 0.100-

1.00, and 1.00 to 10.0 NTU. The spikes that fell into a range for a given method are averaged together to deliver the

stated precision for the given range. These stated precision values for each given range are reported into Section 13

22

of the respective candidate method. Below 1 NTU, the averaged precision for each candidate method is within

0.002 NTU of the precision reported by the reference instrument. Between 1.0-10 NTU, the precision for each of

the candidate methods is within 0.034 NTU of the precision for the reference instrument. This demonstrates

comparability with respect to precision between each of the candidate methods and the reference method.

It is important to note that a decrease in precision was observed in the Lovibond 6000 Laser instrument. Precision is

normally expected to increase in comparison to other methods because of the narrow view volume of the laser

instrument. Similar to a particle counter, the passing of an individual particle into and out of the view volume can

lead to this higher variation. Published literature has shown this is useful information with respect to the

optimization of filter performance.

Table 6 - Precision for Each Spike (Standard Deviation) for Each of the Candidate and Reference methods

Spike

Stable

Measuremen

t Time

Range

Theoretical

Turbidity in

Sample in

NTU

Theoretical

Turbidity of

Spike in

NTU

FT660

Reference -

in NTU

PTV2000

Red 660 Test

- NTU

PTV 1000

WL Test -

NTU

PTV 6000

685 Laser

Test - NTU

Baseline

(Blank) 911 - 947 0.007 0.000 0.0000 0.0002 0.0008 0.0002

2.01 NTU

at 4 RPM 948 - 1033 0.021 0.014 0.0001 0.0002 0.0009 0.0002

2.01 NTU

at 8 RPM 1034 - 1111 0.035 0.028 0.0002 0.0003 0.0002 0.0002

2.01 NTU

at 16 RPM 1112 - 1146 0.067 0.060 0.0002 0.0003 0.0007 0.0008

16.0 NTU

at 4 RPM 1147- 1218 0.117 0.110 0.0005 0.0012 0.0014 0.0007

16.0 NTU

at 8 RPM 1219 - 1251 0.232 0.225 0.0014 0.0020 0.0021 0.0015

134 NTU

at 2 RPM 1252 - 1324 0.561 0.554 0.0036 0.0040 0.0051 0.0055

134 NTU

at 4 RPM 1325 - 1411 0.928 0.921 0.0079 0.0088 0.0094 0.0100

134 NTU

at 8 RPM 1412 - 1455 1.902 1.895 0.0069 0.0077 0.0081 0.0070

800 NTU

at 2 RPM 1456 - 1530 3.575 3.568 0.0077 0.0140 0.0267 0.0566

800 NTU

at 6 RPM 1531 - 1602 9.383 9.376 0.0277 0.0251 0.0313 0.0804

Averaged precision for each range (in bold

text) to be reported in the respective

candidate method.

Average 0-

0.100

0.0002 0.0003 0.0006 0.0004

Average

0.101 - 1.00

0.0034 0.0040 0.0045 0.0044

Average 1.01

to 10

0.0141 0.0156 0.0220 0.0480

Average 0-10

0.0056 0.0064 0.0086 0.0163

Accuracy (Bias) of the Lovibond WL LED Method.

Table 7 contains the calculated percent recoveries for each instrument regarding each turbidity spike. Table 7 is

split into two sections, with the left section containing the percent recovery data for the candidate Lovibond White

Light LED method and the right side of the table containing the percent recovery data for the reference method. The

data is generated from the last 60 measurements of a given spike, which is stated in the far right column of Table 7.

23

The percent recovery data is blank corrected for the highly filtered particle-free water. Both the reference and the

candidate technologies offer this blank subtraction feature in their respective instruments. The candidate instrument

will allow for a blank correction up to 0.05 NTU. The blank correction value for the PTV 1000 was 0.024 NTU in

this study. Historically, the estimated turbidity of turbidity free water was approximately 0.012 NTU when using a

polychromatic “white light” source, thus delivering the stray light error (which includes the combination of

molecular scattering and stray light) of approximately 0.012 NTU for the candidate method. The technical

specification on accuracy for the PTV 1000 instrument was up to 0.015 NTU for any measurement below 0.5 NTU.

In turbidity measurement, there is no true theoretical means to determine the true turbidity of a particle free sample.

Historically, only estimates have been made, much of which was from empirical measurements. True turbidity is a

function of the light source used, and with white light, that has been around 0.012 NTU. However, observations

with 660-nm wavelengths have seen turbidity measurements as low as 0.007 NTU when a linear algorithm is used

(this is the “b” value for a linear curve). This is what was used as the theoretical turbidity of the water in this

validation study. If using the same approach for a linear algorithm, it is probably not possible for a white light LED

system to read that low without some additional subtraction that would have to be applied.

The value for turbidity free water, when measured on the reference instrument is also 0.007 NTU, and the blank

value measured 0.010 NTU. The difference, of these two values was 0.003 NTU, which was the estimated stray

light of FilterTrak 660 Laser nephelometer.

The percent recovery data for each turbidity spike for this candidate instrument range between 96 and 111 percent,

with an average recovery being 99.6 percent over the 0-10 NTU test range. The reference instrument deliver a

slightly tighter recovery range of 97 and 103 percent, with an average recovery of 101 percent. The difference

between the two instruments fall within the accuracy specification for the candidate and the reference instrument.

This is further supported by an ANOVA analysis, which deliver an F value that is less than the F-critical value,

indicating there is no statistical significant difference between the two data sets. The percent recovery data summary

and same percent recovery data that is in Table 7 is presented in sections 13 and 17, respectively, of the candidate

Lovibond White Light LED method.

Table 7 – Results Table for the Percent Recovery and Precision with Respect to Turbidity Spikes for the PTV1000 WL LED

Turbidimeter

PTV 1000 WL Reading (NTU) Reference Turbidimeter Reading (EPA approved

Method 10133)

Spike

#

Baseline

(Blank) in

NTU

Theoretical

Value of

Spike in

NTU

Response

(blank

Corrected)

in NTU

Recovery

(%)

Baseline

(Blank) in

NTU

Theoretical

Value of

Spike in

NTU

Response

(blank

Corrected)

in NTU

Recovery

(%) N

1 0.024 0.014 0.016 110.8 0.010 0.014 0.014 102.3 60

2 0.024 0.028 0.030 104.9 0.010 0.028 0.029 102.6 60

3 0.024 0.060 0.062 102.4 0.010 0.060 0.060 99.4 60

4 0.024 0.110 0.114 103.4 0.010 0.110 0.112 102.0 60

5 0.024 0.225 0.235 104.5 0.010 0.225 0.232 103.3 60

6 0.024 0.554 0.564 101.7 0.010 0.554 0.559 100.8 60

7 0.024 0.921 0.940 102.1 0.010 0.921 0.930 101.0 60

8 0.024 1.895 1.929 101.8 0.010 1.895 1.928 101.8 60

9 0.024 3.568 3.444 96.5 0.010 3.568 3.463 97.1 60

10 0.024 9.376 9.437 100.6 0.010 9.376 9.472 101.0 60

24

Accuracy Results - PTV 1000 Test Accuracy Results - FT660 Reference

Average Recovery Entire Range (0-10

NTU)

102.87

Average Recovery Entire Range (0-

10 NTU) 101.13

Average Percent Recovery up to 0.10 NTU

Range

106.01

Average Percent Recovery up to

0.10 NTU Range 101.46

Average Percent Recovery 0.1 to 1.0 NTU

Range

102.93

Average Percent Recovery 0.1 to

1.0 NTU Range 101.77


range

99.65


10.0 NTU range 99.94

Accuracy (Bias) of the Lovibond 660-nm LED Method

Table 8 contains the calculated percent recovery data for each instrument regarding each turbidity spike. Table 8 is

split into two sections, with the left section containing the percent recovery data for the candidate Lovibond 660-nm

LED method and the right side of the table containing the percent recovery data for the reference method. The data

for each spike is generated from the last 60 measurements of a given spike, which is stated in the far right column of

Table 8.

The percent recovery data is blank corrected for turbidity free water. Both the reference and the candidate

instruments offer the instrument feature for blank correction. The candidate instrument will allow for a blank

correction up to 0.05 NTU. The blank correction value for the PTV 2000 was 0.013 NTU in this study. Using the

value of 0.007 NTU as the turbidity of the blank (the Fort Collins filtered water), the difference between this

turbidity and the PTV 2000 measurement of 0.013 NTU can be attributed to primarily to stray light. This would

calculate to be 0.006 NTU. Thus, the blank value is the sum of the molecular scatter caused turbidity (0.007 NTU)

plus the stray light (0.006) NTU to generate a total measurement value of 0.013 NTU. In summary, the blank

subtraction does not subtract out the instrument stray light, but only the amount of theoretical turbidity in the particle

free blank.

The value for turbidity free water, when measured on the reference instrument was also 0.007 NTU, and the blank

value measured 0.010 NTU. The difference, of these two values was 0.003 NTU, which was the estimated stray

light of FilterTrak 660 Laser nephelometer.

The percent recovery data for each spike for the candidate instrument range between 93.7 and 104 percent among

the 10 different turbidity spikes, with an average recovery being 101 percent over the 0-10 NTU test range. The

reference instrument delivers a slightly tighter recovery range of 97 and 103 percent over the same ten turbidity

spikes, with an average recovery of 101 percent. The difference between the two instruments falls within the

accuracy specifications for both the candidate and reference instrument (2 percent of reading or 0.010 NTU for both

the candidate and the reference instrument). This minor difference is further supported by an ANOVA analysis,

which delivers an F value that is less than the F-critical value, indicating there is no statistical significant difference

between the two data sets. The percent recovery data summary and the data for the candidate method that is in Table

8 is presented in sections 13 and 17, respectively in the candidate Lovibond 660-nm LED method as the bias data.

Table 8 – Results Table for the Percent Recovery to Turbidity Spikes for the PTV2000 660-nm LED Turbidimeter

PTV 2000 660-nm LED Reading (NTU) Reference Turbidimeter Reading (EPA approved

Method 10133)

Spike #

Baseline

(Blank) in

NTU

Theoretical

Value of

Spike in

NTU

Response

(blank

Corrected)

in NTU

%

Recovery

Baseline

(Blank) in

NTU

Theoretical

Value of

Spike in

NTU

Response

(blank

Corrected)

in NTU

%

Recovery N

25

1 0.013 0.014 0.015 104.5 0.010 0.014 0.014 102.3 60

2 0.013 0.028 0.029 104.3

0.010 0.028 0.029 102.6 60

3 0.013 0.060 0.061 101.6 0.010 0.060 0.060 99.4 60

4 0.013 0.110 0.112 101.4 0.010 0.110 0.112 102.0 60

5 0.013 0.225 0.232 103.3 0.010 0.225 0.232 103.3 60

6 0.013 0.554 0.553 99.7 0.010 0.554 0.559 100.8 60

7 0.013 0.921 0.918 99.7 0.010 0.921 0.930 101.0 60

8 0.013 1.895 1.858 98.1 0.010 1.895 1.928 101.8 60

9 0.013 3.568 3.344 93.7 0.010 3.568 3.463 97.1 60

10 0.013 9.376 9.304 99.2 0.010 9.376 9.472 101.0 60

Accuracy Results - PTV 2000 660-nm Test Accuracy Results - FT660 Reference


NTU)

100.55


10 NTU)

101.13


Range

103.47

Average Percent Recovery up to 0.10

NTU Range

101.46


Range

101.03

Average Percent Recovery 0.1 to 1.0

NTU Range

101.77


range

97.00


10.0 NTU range

99.94

Accuracy (Bias) of the Lovibond 6000 Laser Method

Table 9 contains the calculated percent recoveries for each instrument regarding each turbidity spike. Table 9 is

split into two sections, with the left section containing the percent recovery data for the candidate Lovibond 6000

Laser method, which is denoted as the PTV6000 685-nm Laser turbidimeter in this table. The right side of this table

contains the percent recovery data for the reference method. The data for each spike is generated from the last 60

measurements of a given turbidity spike, which is stated in the far right column of Table 9.

The percent recovery data is blank corrected for turbidity free water. Both the reference and the candidate

instruments have a blank correction feature. The candidate instrument will allow for a blank correction up to 0.05

NTU. The blank value for the PTV 6000 was 0.012 NTU in this study. Historically, the estimated turbidity of

turbidity free water was approximately 0.007 NTU when using a 660-nm monochromatic source, thus delivering the

stray light error of approximately 0.005 NTU for this candidate method. The technical specification of this PTV

6000 instrument was up to within 0.010 NTU for any measurement below 0.5 NTU.

The value for turbidity free water, when measured on the reference instrument was also 0.007 NTU, and the blank

value measured 0.010 NTU. The difference, of these two values was 0.003 NTU, which is the estimated stray light

of FilterTrak 660 Laser nephelometer.

This information helps explain how the different candidate instruments compare at the bottom end of the turbidity

range as well as provide for a comparison to the reference instrument. As can be seen with the comparison between

the PTV 6000 and the FilterTrak 660 is 0.002 NTU at the bottom of the range. From a practicality perspective, this

value is so small it is very difficult to quantify and essentially provides equivalency to each between these two

instruments.

The percent recovery data for each spike for the candidate instrument range between 94.3 and 103 percent among

the 10 different turbidity spikes, with an average recovery being 100 percent over the 0-10 NTU test range. The

reference instrument deliver a slightly tighter recovery range of 97 and 103 percent over the same ten turbidity

26

spikes, with an average recovery of 101 percent. The difference between the two instruments falls within the

accuracy specifications for both the candidate and reference instrument (2 percent of reading or 0.010 NTU for both

the candidate and the reference instrument). This minor difference is further supported by an ANOVA analysis,

which delivers an F value that is less than the F-critical value, indicating there is no statistical significant difference

between the two data sets. The percent recovery data summary and the percent recovery data for the candidate

method found in Table 9 is presented in sections 13 and 17, respectively in the Lovibond 6000 Laser candidate

method as the percent recovery data.

Table 9 – Results Table for the Percent Recovery to Turbidity Spikes for the PTV6000 685-nm Laser Turbidimeter

PTV 6000 685-nm Laser Reading (NTU) Reference Turbidimeter Reading (EPA approved

Method 10133)

Spike #

Baseline

(Blank) in

NTU

Theoretical

Value of

Spike in

NTU

Response

(blank

Corrected)

in NTU

%

Recovery

Baseline

(Blank) in

NTU

Theoretical

Value of

Spike in NTU

Response

(blank

Corrected)

in NTU

%

Recovery N

1 0.012 0.014 0.015 103.4

0.010 0.014 0.014 102.3 60

2 0.012 0.028 0.029 101.8

0.010 0.028 0.029 102.6 60

3 0.012 0.060 0.060 99.2

0.010 0.060 0.060 99.4 60

4 0.012 0.1100 0.111 100.6

0.010 0.110 0.112 102.0 60

5 0.012 0.225 0.230 102.3

0.010 0.225 0.232 103.3 60

6 0.012 0.554 0.554 99.9

0.010 0.554 0.559 100.8 60

7 0.012 0.921 0.915 99.4

0.010 0.921 0.930 101.0 60

8 0.012 1.895 1.885 99.5

0.010 1.895 1.928 101.8 60

9 0.012 3.568 3.366 94.3

0.010 3.568 3.463 97.1 60

10 .012 9,377 9.419 100.4 .010 9.376 9.472 101.0 60

Accuracy Results - PTV 6000 685-nm Laser Test Accuracy Results - FT660 Reference


NTU)

100.08


10 NTU)

101.13


Range

101.43

Average Percent Recovery up to

0.10 NTU Range

101.46


Range

100.55


1.0 NTU Range

101.77


range

98.09


10.0 NTU range

99.94

Tables 5 through 9 contain data that demonstrate initial comparability between each of the three candidate test

methods and the reference method with respect to precision and accuracy on defined turbidity spikes that were

derived at the Fort Collins site. The other two sites will demonstrate comparability with respect to filter runs at the

Binney South Platte and the San Patricio MWD test sites.

The Binney South Platte Comparability Test Site

The purpose of this portion of the study was to collect EPA comparability data for three candidate turbidity methods

on three different waters. The Binney South Platte site represents the second water type. The three candidate

methods were identical with the exception of the incident light source. The reference method was Hach Method

27

10133, which offers the FilterTrack 660 sc laser nephelometer as an instrument that is fully compliant to this test

method. This study compared newly developed Lovibond PTV 1000/2000/6000 turbidimeters that were

representative of the proposed turbidity methods to the EPA accepted reference method. A detailed description of

the test setup is found in the document "Alternative Test Procedure Method and Validation Plan, Revision 1.0", for

the PTV Series of turbidimeters evaluation. The validation plan is identified as Appendix A of this validation report.

This study plan required the collection of a sample from a common tap of filter effluent water. Sample was split

into five parallel streams at a manifold that fed a total of five instruments involved in this study. The fifth

instrument was added to the test panel and as a second EPA approved instrument that was very popular throughout

the drinking water industry. This instrument was compliant to EPA Method 180.1 and was known as the 1720E

turbidimeter. Due to its popularity in filter effluent monitoring, the 1720E was included in the monitoring and any

information presented herein is simply for additional information. Data collected from this instrument is completely

excluded from all calculations that are used in this ATP study.

The length for each sample line was the same for each instrument. The flow rate of sample to each candidate

instrument was the same, at about 70 ml/minute. This was within the manufacture's recommendations. The flow

rate for the reference instrument was about 350-ml/minute, which was within that manufacturer's recommendations.

After calibration and QC was performed, the instruments measured the turbidity of the sample for approximately 3

days. Data was automatically logged from each instrument at 15-second intervals into a common data logger for all

the instruments. This data is contained in a Microsoft Excel Workbook titled Aurora Binney Filtration SP Treat

Train Test Site.xls, which was provided external of this validation report. This workbook contains several

worksheets and graphs which are described in Table 10. Note: spreadsheets, pages, and worksheets were

synonymous with respect to the workbook discussion in Table 10.

Table 10 – A Description of the Excel Workbook for the Aurora Binney South Platte Phase of this Method

Comparability Study

Excel Page

Description

Exec Summary This is the Executive Summary for the test site. It briefly describes the study, the results and the

conclusions. The results and conclusions are mirrored into this validation report.

Reporting The reporting spreadsheet contains the final tables that directly compare the three candidate

methods to the reference method. The basis for the comparison is on the average value and standard

deviation for each of the methods for a given block of data. A final table at the bottom of this

spreadsheet lists the net difference in turbidity between each of the candidate methods and the

reference for each of the data blocks and the data over the entire study.

Checklist This is a checklist to help the site coordinators insure that all the details that pertain to the setup,

collection of data and QC are addressed. Most of the details are discussed in Section 7 of the

validation plan.

Quality

Assurance

This spreadsheet contains information that pertains to the calibration and QC for the study site.

Raw Data Raw Data – This worksheet contains the original raw data from the study. The date/time is in the

first column, followed by the data from the 1720E turbidimeter in column B, reference FT660

instrument data in mNTU in column C, rescaled reference FT660 instrument data in NTU in column

D, the PTV 2000 Red LED in Column F, the PTV 1000 WL LED in Column G, followed by the

PTV 6000 Laser in Column H. This raw data overlaps the actual study data from a time perspective

in that it contains data prior to calibration.

Data EPA This is the most important page of the Excel spreadsheet with respect to the calculations. The

Raw Data columns are resorted, with columns A-F containing: Date and Time, FT660 in NTU, PTV

2000 Red LED in NTU, PTV 1000 WL LED in NTU, PTV 6000 Laser in NTU and the 1720E in

NTU respectively. To the right of this data are the tables that contain the summarized average and

standard deviations for these instruments. Measurement data is separated into 8-hour blocks with

the exception of the last block of data which contain the remaining measurements. There is also a

data table that contains all the data from the study and another data table that incorporates the small

spike of turbidity that took place near the end of the study. The final table on this spreadsheet is a

compilation of the net differences in the averages between different instruments for each of the data

28

blocks.

Turbidity Plot This is the summary graph that shows the start and stop times of valid data that was collected and

analyzed. It is pasted into this validation report as Figure 3.

Graph of

Turbidity Spike

This graph is generated to cover the spiking of raw water into the sample prior to the manifold that

split and fed it to the test instruments. The graph illustrates instrument responses and subsequent

recoveries relative to these spikes. This is pasted into this validation report at Figure 4.

Photos This page contains the photographs that were taken during this portion of the study. Most of the

photographs are with respect to the calibration and QC portion of the validation study.

Figure 3 provides a graphical illustration of all the data logged at this test site. The instrument response to turbidity

is on the y-axis and the date and time is on the x-axis. The y-axis is scaled to a maximum of 0.3 NTU, which is the

reporting limit for filter effluent turbidity. The legend for this graph is at the bottom and contains traces for the three

candidate methods, the FT660 reference and the 1720E instrument. The 1720E trace was only provided for

empirical informational purposes only and was not included in any data or calculations. The start and stop times of

data collection is identified by two vertical red lines on the graph. Data outside of these lines is not part of the

comparability analysis.

The run time of this study incorporates three complete filter runs, which included ripening, the production run and

backwash phases. The turbidity ranged from less than 0.05 NTU up to approximately 0.1 NTU. It was worth noting

that within a given filter run, the turbidity variance for the laser instruments (both the Reference and the PTV 6000)

increased as the run progressed. This increase was thought to be caused by very low numbers of particles that

eventually pass through the filter and are detected within the small, but high incident beam density view volumes

that are characteristic with laser based turbidimeters.

Figure 3 illustrates that the three candidate instruments tracked the reference instrument throughout the study. There

are slight differences between the technologies, primarily with the Lovibond White Light LED method (represented

by the PTV 1000 WL turbidimeter, which is the green trace). The measurements are consistently between 0.01 and

0.02 NTU above the reference value, which is primarily due to the inherent stray light that is characteristic of a

polychromatic light source. The Lovibond 660-nm LED method and the Lovibond 6000 Laser methods tracked

very closely to the reference turbidimeter, but as each filter run progressed, these two instruments exhibited

increased sensitivity to turbidity. Table 11 provided a summary of the net differences between each of the candidate

methods and the reference method at this test site.

With respect to tracking the turbidity events, all instruments track each other in the detection and trending of all

events. No instrument is out of sync of the other methods by more than 1-minute. Considering the reporting

requirement of 15-minute intervals, this difference in responsiveness to turbidity changes was very minor.

29

Figure 3 - Graph of on-line turbidity data for the three candidate methods and the reference method. Data was logged at

15-second intervals. QC validated study data is between the vertical red lines.

The last day of the study involved the spiking of raw water into the effluent sample line that led to the three

candidate and reference instruments. The injection was before the manifold that splits the sample. This yielded the

turbidity spike. The spike was analyzed to insure the three candidate technologies detected the excursion and then

the recovery back to the baseline. Figure 4 provides a zoomed in portion of the on-line trending graph that

illustrates the response of the three candidates and reference instruments to this turbidity excursion. The graph

illustrates the response and recoveries of all the instruments that measured this water. The candidate PTV 6000

turbidimeter shows the greatest absolute response, which is expected from a laser based light source. This is

followed by the candidate PTV 2000 turbidimeter. The PTV 1000 WL turbidimeter shows the highest turbidity, but

it also has the highest baseline. However, the net difference is comparable to the reference instrument. The graph

also shows the 1720E instrument. This instrument measures very close to the PTV 1000 white light instrument, but

it shows a slower response time, because its flow rate was at 100-ml per minute, which was below the recommended

250 ml/minute flow range of that instrument.

30

Figure 4 - Graph of the candidate and reference method instruments’ response to a turbidity spike of raw water into the

filter effluent sample line.

Table 11 contains the net difference in turbidity between the candidate methods and the reference method

(Difference = Candidate turbidity-Reference turbidity) for each of the data sets. The greatest difference is with the

data set for the spike of turbidity, which shows an increase in the net turbidity difference for each of the candidate

methods. The differences demonstrate the sensitivity of these methods to a turbidity spike, such as the one that was

performed at this study. The other 8 data blocks display relatively small net differences relative to the reference

instrument. The entire data set, 16157 measurements is used for final comparisons between each of the three

candidate instruments and the reference instrument.

The candidate Lovibond White Light LED method instrument measured 0.019 NTU higher than the reference

method instrument over the entire study. As mentioned previously, this is primarily due to the inherent stray light of

a polychromatic light source that was in the Lovibond instrument. It could also be due to this light source having

greater sensitivity to smaller particles, since a portion of the emitted light was in the 400-600 nm range. In addition,

dissolved compounds can potentially cause fluorescence effects upon the interaction of the lower wavelengths of

light from the white light LED source. However, this candidate method still tracks the reference method throughout

the study that involved several complete filter runs and the spike of turbidity.

The candidate Lovibond 660-nm LED method measured 0.009 NTU higher than the reference method over the

16157 data points that were logged at this test site. The difference was very small and was likely attributed to stray

31

light. This candidate method tracked the reference method throughout the study that included several filter runs and

the spike of turbidity.

The candidate Lovibond 6000 Laser method measured 0.009 NTU higher than the reference method at this test site.

This instrument has essentially the same stray light, but as each filter run progressed, it showed additional response

to the trended increases in turbidity. This was further demonstrated on the turbidity spike, where the candidate

method demonstrated the greatest response to this spike. The candidate method tracked the reference method

throughout the study that included several filter runs and the spike of turbidity.

Table 11 - Net Difference Relative to the Reference (FT660) at the Binney South Platte

Treatment Train. Data in Red Was Reported in the Respective Candidate Methods.

Data Set

PTV 2000 660-

nm Test in NTU

PTV 1000

Test in NTU

PTV 6000 685

nm Laser in

NTU N

Data Block

1 0.006 0.018 0.005 1918 Data Block

2 0.016 0.023 0.018 1918 Data Block

3 0.006 0.014 0.003 1918 Data Block

4 0.010 0.017 0.009 1918 Data Block

5 0.008 0.017 0.009 1918 Data Block

6 0.010 0.020 0.009 1918 Data Block

7 0.009 0.019 0.009 1918 Data Block

8 0.010 0.021 0.009 1918 Data Block

9 0.008 0.020 0.010 802 Entire Data

Set 0.010 0.019 0.009 16157 Data from

Raw Water

Spike 0.023 0.027 0.034 143

The three Lovibond candidate methods demonstrated excellent comparability to the reference turbidimeter at the

Binney South Platte Test Site. The site provided an excellent opportunity to observe filter performance as the plant

had just come on-line after several months of construction and maintenance. The plant was not in an optimized state

at the time of data collection. The plant management is very interested in this data and understood its value to help

optimize their treatment processes.

The San Patricio MWD Comparability Test Site

The San Patricio MWD membrane facility was the third water to be analyzed by the three candidate Lovibond

turbidity test methods and the reference method. The three candidate methods were identical with the exception of

the incident light source. The reference method was Hach Method 10133, which offers the FilterTrack 660 sc laser

nephelometer as an instrument that was fully compliant to this test method. This study compared newly developed

Lovibond PTV 1000/2000/6000 turbidimeters that are representative of the proposed turbidity methods to the EPA

accepted reference method. A detailed description of the test setup is found in the document "Alternative Test

Procedure Method and Validation Plan, Revision 1.0", for the PTV Series of turbidimeters evaluation that is

appended to this validation report.

32

This study plan required the collection of a sample from a common tap of membrane effluent water. Sample was

split into four parallel streams that fed the four instruments involved in this study. The length of each sample line

was the same to each instrument. The flow rate of sample to each of the three candidate instruments was the same,

at about 70 ml/minute. This was within the manufacture's recommendations. The flow rate for the reference

instrument was about 350-ml/minute, which was within that manufacturer's recommendations.

After calibration and QC was completed, the instruments measured the turbidity of the sample for about 18 hours.

Data was automatically logged from each instrument at 15-second intervals into a common data logger for all the

instruments. This data is contained in the Microsoft Excel Workbook titled San Pat MWD Test Site.xls, which was

provided external of this validation report. This workbook contains several worksheets and graphs which are

described in Table 12. Note: spreadsheet, worksheet, and page are synonymous with respect to Table 12.

Table 12 – A Description of the Excel Workbook From the San Pat MWD Phase of this ATP

Comparability Study

Excel Page

Description

Exec Summary This is the Executive Summary of the Study. It briefly describes the study, the results and

the conclusions. The results and conclusions are mirrored into this validation report.

Reporting The reporting spreadsheet contains the final tables that directly compare the three

candidate methods to the reference method. The basis for the comparison is on the

average value and standard deviation for each of the methods for a given block of data. A

final table at the bottom of this page lists the net difference in turbidity between each of

the candidate methods and the reference method for each of the data blocks and the data

over the entire study.

Checklist This is a checklist to help the site coordinators insure tall the details that pertain to the

setup, collection of data and QC were completed. Most of the details are discussed in

Section 7 of the validation plan.

Quality

Assurance

This spreadsheet contains information that pertained to the calibration and QC for the

study site.

Raw Data Raw Data – This spreadsheet contains the original raw data from the study. The date/time

is in the first column, followed by the reference FT660 instrument data in mNTU in

column C, rescaled reference FT660 instrument data in NTU in column D, the PTV 2000

Red LED in Column F, the PTV 1000 WL LED in Column G, followed by the PTV 6000

Laser in Column H.

Data EPA This is the most important spreadsheet in the Excel workbook with respect to the

calculations. The Raw Data columns are resorted, with columns A-E containing: Date

and Time, FT660 in NTU, PTV 2000 Red LED in NTU, PTV 1000 WL LED in NTU, and

the PTV 6000 Laser in NTU respectively. To the right of this data are the tables that

contain the summarized average and standard deviations for these instruments. Data is

separated into four Tables. Tables 1 and 2 contains data from the two turbidity spikes

(settled water), Table 3 contains the first 8 hours of run time, Table 4 contains the second

8 hours of run time, Table 5 contains remaining run-time data, and Table 6 contains the

entire data run (after calibration and verification). The final table, Table 7 contains the net

difference between each of the three candidate methods and the reference method for each

of the blocks of data. The cells in these tables contain the formulas for all these results.

Graph of CFE

Turbidity

This is the summary graph that illustrates the start and stop times of data that are

analyzed. It is pasted into the Validation Report as Figure 5.

Graph of

Turbidity Spike

This graph is generated to cover the spiking of settled water into the sample prior to the

manifold that split and fed sample to the three candidate and reference instruments. The

graph illustrates the response and recoveries for these instruments relative to these spikes

of settled water. This is pasted into this validation report at Figure 6.

Photos This spreadsheet contains the photographs that were taken during this portion of the study.

Most of the photographs are with respect to the calibration and QC portion of the

validation study.

33

The data that was collected at the San Patricio MWD Site is graphically illustrated in Figure 5. The instrument

response to turbidity is on the y-axis and the date and time is on the x-axis. The y-axis is scaled to a maximum value

of 0.3 NTU, which is the reporting limit for filter effluent turbidity. The legend for this graph is at the bottom and

contains the traces for the three candidate methods and the FT660 reference instrument. The start time for data

collection is identified by the red vertical line on the left part of the graph. Data that is to the left of this line was not

part of this study.

This study included two spikes of turbidity that were conducted early in the study. A sample of settled water, that

was approximately 5 NTU was collected and injected at two different fixed rates into the sample line prior to the

manifold that split it into the parallel streams. The spikes were intended to be in the 0.1 and then 0.2 NTU range.

After the completion of the spiking, the instruments were allowed to run for another 18 additional hours before data

collection was terminated.

In figure 5, the reference trace (in blue) is overlapped by the two candidate instrument traces for the Lovibond 660-

nm LED and the Lovibond Laser LED. These two candidate instruments demonstrated comparability throughout

the entire data set, including the turbidity spikes. The candidate Lovibond White Light LED method delivered an

overall higher response throughout the study, but still correlated closely to all the turbidity events, including the

turbidity spikes. The net difference between the candidate white light LED method was greater on this water, which

was also observed when grab samples were taken and measured on a benchtop instrument that was an EPA 180.1

compliant instrument (the Hach 2100N turbidimeter). While some of the difference was likely attributed to stray

light, the additional difference may be due to some compounds in the sample that exhibit a fluorescence effect was

not detected by the other instruments in the study.

Grab samples were taken from this site and examined back at the Fort Collins R&D facility. The examination was

to determine if light in the 410-410-nm range does cause a molecular fluorescence event. The results from this test

confirmed these effects do occur on this sample. Since the white light LED does emit light as low as 400-nm, this

fluorescence effect possibly does contribute to the higher turbidity on the San Patricio membrane filtered sample.

34

.

Figure 5 - Graph of the three candidates and the reference method for on-line measurement of turbidity on membrane

effluent. Data right of the vertical red line was QC validated for this test site.

The two turbidity spike levels that were conducted at the San Pat MWD test site is the focus of Figure 6. The graph

illustrates the response times for the three candidate and reference instruments. The graph illustrates that these are

comparable with respect to both spikes and their respective recoveries. The PTV 1000 LED net response is

equivalent on the first spike, but is slightly reduced on the second (higher) spike. This decrease may be due to some

absorbance of a portion of the incident white light at the higher turbidity level. The candidate Lovibond 660-nm

LED and the candidate Lovibond 6000 laser turbidimeter methods show near equivalent response relative to the

reference method instrument on these two spikes.

35

Figure 6 - Graph of the three candidates and the reference instrument for two different levels of spiked turbidity (settled

water) into the membrane filtrate stream.

The actual comparability data from the San Pat MWD test site is summarized into Table 13. This contains the net

difference in turbidity between each of the candidate method’s respective instrument and the reference method

(Difference = Candidate turbidity-Reference turbidity) for each of the data sets. The greatest difference is with the

data set for the two turbidity spikes, which shows an increase in the net turbidity difference for each of the candidate

methods. The greatest difference was with the candidate Lovibond White Light LED Method which measured

0.045 NTU higher than the reference. This was followed by the candidate Lovibond 660-nm LED Method which

measured within 0.010 NTU for both spikes. The candidate Lovibond 6000 Laser Method compared the closest to

the reference method with an average difference of 0.007 for the two spikes. All instruments were capable of

detecting the spikes with comparable response and recovery times.

The candidate Lovibond White Light LED method measured 0.045 NTU higher than the reference method over the

entire study. As mentioned previously, this is primarily due to the inherent stray light of a polychromatic light

source as one factor. It could also be that this light source exhibited greater sensitivity to smaller particles, since a

portion of the emitted light was in the 400-600 nm range. The higher turbidity values obtained in this method were

also observed on grab samples on a 180.1 compliant benchtop turbidimeter. Thus, there could be some additional

fluorescence component in this membrane effluent that caused the increased response that a polychromatic light

source can detect but was impacted by the other methods in this study. In general, this candidate method still tracks

the reference method throughout the study that involved several filter runs and the spikes of turbidity.

36

The candidate Lovibond 660-nm LED method measured 0.002 NTU higher than the reference method over the 4692

data points that were logged at this test site. The difference is very small and was likely attributed to stray light.

This candidate method tracks the reference method throughout the study that included several filter runs and the

spike of turbidity. This candidate method demonstrated comparability to the reference method for the entire

monitoring phase at this test site.

The candidate Lovibond 6000 Laser method measured 0.0003 NTU lower than the reference method at this test site.

This instrument has essentially the same stray light as the reference, and showed a very slight heightened response

to the spikes. Overall, this method shows comparable but slightly higher sensitivity to the turbidity events on this

membrane effluent.

Table 13 - Net Difference Relative to the FT660 at the San Pat MWD Membrane Plant

Data Set PTV 2000 660-

nm Test in NTU

PTV 1000 Test in

NTU

PTV 6000 685

nm Laser in

NTU

N

Data Block 1 0.011 0.042 0.007 23

Data Block 2 0.007 0.022 0.009 59

Data Block 3 0.002 0.045 -0.001 1923

Data Block 4 0.002 0.045 -0.001 1918

Data Block 5 0.002 0.047 -0.001 358

Entire Data Set 0.002 0.045 -0.000 4692

The San Patricio MWD test site challenged the three candidate methods to collect turbidity near the bottom of their

ranges in an extreme environment that included a very warm sample. All instruments responded to the turbidity

spikes. This membrane facility uses significant quantities of air to prevent membrane fouling and it was a

challenging application to be able to eliminate any interference from entrained air. In all cases, the test methods

demonstrated the ability to eliminate this interference and deliver comparability data that correlated strongly to the

reference method.

Limit of Detection (LOD)

Turbidity methods typically do not report detection limits due to challenges associated with maintaining stable low-

level turbidity standards and the ability to separate out stray light and the turbidity of pure water from any low-level

measurement. However, the limit of detection can be estimated and was calculated for the three candidate methods

and the reference method.

The precision data from the three lowest turbidity spikes that were performed at the Fort Collins test site were used

to determine the LOD for each of the methods. The precision value was multiplied by a factor of three to deliver an

estimated LOD based on the each of the three lowest turbidity levels. These three estimated LOD calculations were

then averaged to deliver the estimated LOD for the respective method. Table 14 provided the calculated estimated

LOD for each turbidity level. The bottom line in this table provided the averaged and reported estimated LOD value

for the each of the three candidates and reference method (in bold).

Table 14 – The Estimated Limit of Detection Estimate for the Candidate and Reference methods

Theoretical

Turbidity of Spike in

NTU

FT660 Reference

3* Precision

PTV 2000 Reference

3* Precision

PTV 1000

Reference 3*

Precision

PTV6000

Reference 3*

Precision

0.0141 0.0004 0.0006 0.0028 0.0007

37

0.0282 0.0006 0.0009 0.0007 0.0007

0.0603 0.0007 0.0010 0.0020 0.0025

LOD 0.0006 0.0008 0.0018 0.0013

The estimated LOD for the candidate Lovibond White Light LED was determined to be 0.0018 NTU. This method

stated the reporting criterion to the nearest 0.010 NTU at the lowest turbidity range, which this calculation

supported.

The estimated LOD for the candidate Lovibond 660-nm LOD was determined to be 0.0008 NTU. This method

stated the reporting criterion to 0.01 NTU for the lowest turbidity range, which this calculation supported. However,

the low estimated LOD for this method provides capability to support a water plant in its optimization of its

treatment and filtration processes.

The estimated LOD for the Lovibond 6000 Laser Method was determined to be 0.0013 NTU. This method stated

the reporting criterion to the 0.01 NTU for the lowest range, which this calculation supported. The low estimated

LOD and increased sensitivity that was demonstrated at the filter plant comparability studies provides capability of

the method’s application for the optimization of the treatment and filtration processes in drinking water plants.

3.1.3 Quality Controls

The quality controls are described in Section 6 of the validation plan. The plan required the use of one quality

control sample (QCS) that was a fresh prepared formazin standard. The QCS would be run on each instrument after

calibration. A second QCS sample would be run at the completion of data collection. The QCS samples would be

checked on a benchtop turbidimeter (the Hach 2100N or 2100 AN) to insure its preparation was correct. This

approach was to be performed at each of the three test sites.

One of changes to the validation plan was to run an additional QCS sample after calibration and to run an additional

QCS sample after the data run. Thus, a total of two QCS samples were prepared and run before and after data

collection at each site. The reason for this is with the difficulty in preparing low turbidity standards. This can be

very difficult at values below about 1 NTU. Difficulties with contamination and bubbles often lead to erroneous

measurements. Thus, we opted for a higher value at 0.6 NTU thinking that this would be easier to prepare in the

field. However, once we prepared that accurately, we decided to prepare a second one at 0.3 NTU. This was

selected as it was closer to the true operational limit for regulatory. Thus, instead of eliminating the 0.6 NTU we

just added the second standard. The demonstration that we could prepare these in the field was very important to

demonstrating the method performance where it is practiced.

It was mentioned in the descriptions of the three Microsoft Excel workbooks (one for each test site); each contains a

Quality Assurance spreadsheet. The pass fail criteria for the QCS samples was either 10% of the value of the

sample or 0.04 NTU for the Candidate Lovibond White Light LED method, or 0.03 NTU for both the candidate

Lovibond 660-nm LED method and the candidate Lovibond Laser Turbidimeter Method. If the instrument does not

pass the pass/fail criteria, then the standard should be checked on a calibrated benchtop turbidimeter to insure it is

correctly prepared. If it is and it fails, then the method is unacceptable for reporting purposes. The reference method

did not state a pass fail criteria in its QCS section, but did state that the linear calibration range (LCR) standards

should read within 0.025 NTU. This was assumed to be the pass fail criteria for the reference method.

As was mentioned above, low level standards are hard to prepare and even the commercially available stabilized

versions do change after preparation. Providing absolute P/F criteria allows for prepared sealed standards to meet

such as specification at low levels up to their respective expiration date. Preparation of these standards is very

38

susceptible to technique and makes the use of a P/F percentage difficult to achieve. Because this is a continuous

monitoring method, the combination of the instrument measurement error plus the preparation techniques (in

preparing the standard itself and using the standard) result in propagated error. At low levels, these errors will

typically bias high and will exceed percentage criteria. For example, at 0.1 NTU, a 10% limit is nearly impossible

to meet because of the turbidity of the diluent, contamination, bubbles generated during transfer, when combined

will contribute to a high positive bias. Thus, the absolute criteria only apply to low level solutions. Once the value

is above the level where the percent is greater than the absolute value then the specification is exclusively as a

percentage.

The difference in the absolute values between the WL LED and the 660-nm methods was the additional stray light.

The additional stray light that is inherent in a WL instrument will have difficulty passing if this pass/fail criterial is

not opened up to a larger level. Note if a higher standard was used, such at 5 NTU, this would not be an issue

because the effects of stray light are not present.

The QC data for the test sites is on the “Quality Assurance” spreadsheet in each of the Microsoft Excel workbooks.

Table 15 provides a summary of QC data for the Fort Collins Test site. These QCS values were adjusted for the

small additional turbidity of the dilution water, which was 0.010 NTU. Thus, the pass fail was relative to this

adjusted value. All instruments passed their respective QCS criteria at this site.

Table 15 - Fort Collins Filtered Tap Water Test Site - Wet Validation QCS - 1.01 NTU Formazin - Must be less than ± 10% to

Pass or ±0.04 NTU (WL LED) or ±0.03 NTU (660 LED or Laser)

Event (date)

FT660

Ref in

NTU % Err

PTV2000

Red 660

Test -

NTU % Err

PTV

1000

WL

Test -

NTU % Err

PTV 6000

685 Laser

Test -

NTU % Err

2100AN

Reading

in NTU

7/19/16 After Calibration 1.009 -0.09 1.025 1.49 1.044 3.37 1.023 1.29 1.01

7/20/16 Before formazin

Turbidity Spikes 0.999 -1.00 1.028 1.78 1.042 3.17 1.024 1.39 1.01

7/20/2016 Conclusion of

Formazin Turbidity Spikes 0.973 -3.71 1.051 4.06 1.026 1.58 1.012 0.20 1.00

Wet Validation QCS - 0. 3 NTU Formazin - Must be less than ± 10% to Pass or ±0.04 NTU (WL LED) or ±0.03 NTU (660 LED

or Laser)

7/19/16 After Calibration 0.308 -0.73 0.317 2.26 0.33 5.81 0.309 -0.32 0.34

7/20/16 Before formazin

Turbidity Spikes 0.305 -1.56 0.315 1.62 0.33 7.10 0.317 2.26 0.33

7/20/2016 Conclusion of

Formazin Turbidity Spikes 0.315 1.58 0.352 13.55 0.34 8.71 0.321 3.55 0.33

The quality control data from the Aurora Binney South Platte site is summarized in Table 16. Two standards were

run before and after data collection. One standard was prepared at 1.02 NTU and the second standard was prepared

at 0.62 NTU. These standards were prepared with water that had sat in their glass containers for several days and

measured a slightly elevated turbidity value when measured on the same 2100AN benchtop turbidimeter. All

instruments passed their respective method’s QC criteria.

Table 16 – Binney South Plate Comparability Site - Wet Validation QCS - 1.01 NTU Formazin - Must be less than ± 10% to Pass

or ±0.04 NTU (WL LED) or ±0.03 NTU (660 LED or Laser)

39

Event (date)

FT660

Ref in

NTU % Err

PTV2000

Red 660

Test -

NTU % Err

PTV

1000

WL

Test -

NTU % Err

PTV 6000

685 Laser

Test -

NTU % Err

2100AN

Reading

in NTU

7/15/16 After Calibration,

Before Data 10.30 1.96 1.033 2.28 1.047 3.66 1.062 5.15 1.02

7/18/16 After Comparison

Run on South Platte

Treatment Train Combined

Filter Effluent 1.029 1.89 1.022 1.19 1.050 3.96 1.063 5.25 1.02


or Laser)

7/15/16 After Calibration,

Before Data 0.608 -0.30 0.648 6.23 0.645 5.74 0.642 5.25 0.626


Run on Aurora Reservoir

Treatment Train Combined

Filter Effluent 0.656 7.52 0.638 4.59 0.657 7.70 0.640 4.92 0.658

Table 17 provided a summary of the quality control data from the San Patrico MWD water sample. This QCS

samples were prepared through the dilution of stock formazin with membrane effluent water. The membrane

effluent measured 0.015 NTU on their regulatory monitoring turbidimeters, which were the FT660 laser

nephelometers. We also measured the turbidity of the QCS samples on their laboratory turbidimeter, a 2100N. The

2100N measured a higher turbidity of this water. However, this benchtop turbidimeter did not have available QC

data, so instead the reporting turbidimeter (FilterTrak 660) was used to estimate the turbidity of the water. This was

factored into the theoretical value of the of the QCS samples.

The three candidate and the reference instruments passed both QCS samples before and after the data collection at

this test site. The candidate instrumentation comply with the QCS pass/fail criteria for their respective methods.

The reference instrument did measure the QCS sample slightly lower than expected, but it was within the 10 percent

of the P/F value of the QCS.

Table 17 – San Patricio MWD Comparability Site - Wet Validation QCS - 1.01 NTU Formazin - Must be less than ± 10% to

Pass or ±0.04 NTU (WL LED) or ±0.03 NTU (660 LED or Laser)

Event (date)

FT660

Ref in

NTU % Err

PTV2000

Red 660

Test -

NTU % Err

PTV

1000

WL

Test -

NTU % Err

PTV 6000

685 Laser

Test -

NTU % Err

2100AN

Reading

in NTU

7/27/16 After Calibration 0.950 5.90 1.009 0.10 1.038 -2.77 0.998 1.19 1.08


Run on MF Treatment

Train Combined Filter

Effluent 0.992 1.77 1.012 -0.20 1.025 -1.49 0.954 5.54 1.07

40


or Laser)

7/27/16 After Calibration 0.291 6.05 0.304 1.94 0.347 -11.94 0.304 1.94 0.34


Run on MF Treatment

Train Combined Filter

Effluent 0.301 2.75 0.308 0.65 0.350 -12.90 0.308 0.650 0.35

The passing of the QCS criteria for the three candidate methods provided validity of the data that was collected at

the three different test sites. Because the measurements data was close to theoretical values across all of the testing

and the error in preparation of each standard was not considered, this further insured the QC approach was

appropriate for each of the candidate methods.

3.1.4 Precision and Accuracy

The precision and accuracy data was initially presented in Section 3.1.2 of this report. Table 5 provides the response

data to each of the 10 turbidity spikes for the three candidate methods. Least squares analysis was performed on the

linear relationship between each instrument’s response and the theoretical turbidity for each turbidity level. The

three candidate methods demonstrated high linearity with r-squared values that exceeded 0.999 over the test range of

0 to 10 NTU. The reference instrument also demonstrated comparable performance, which was indicative of a

sound test approach for precision and bias determination.

Table 6 provides a summary of the precision for the three candidate methods and the reference method. The

precision is comparable between the methods and was further summarized for each of three ranges of turbidity: 0 to

0.100 NTU, 0.100 to 1.00 NTU and 1.00 NTU to 10 NTU. This summary is at the bottom of Table 6.

Tables 7 through 9 provide a side-by-side comparison between each of the three candidate methods and the

reference method. Table 7 provides comparison data between the Lovibond White Light LED method and the

reference method. Table 8 provides comparison data between the Lovibond 660-nm LED Method and the reference

method. Table 9 provides the comparison data between the Lovibond Laser Method and the reference method.

Table 14 provides limit of detection information to further support the defined reporting limits that were stated in

Section 12 of each respective candidate method (see Appendices B.1, B.2 and B.3).

3.2 Holding Time / Storage Stability

The candidate and reference methods are on-line or continuous monitoring methods. Therefore, holding times are

not applicable. Further, turbidity samples are typically not stable and should be analyzed upon collection. With

respect to turbidity standards and QCS, they were prepared immediately before use and measured within 1 hour of

preparation to insure no degradation of the standards.

4.0 Data Analysis and Discussion

41

This section is broken down into two sections. The first section discusses how the data was analyzed and references

the tables that were provided in the demonstration of capability section. The second part discusses the comparison

between the alternate method data for each of the candidate methods to the reference method. Each candidate

method is individually compared to the reference method.

Data Analysis

The precision and bias data was analyzed from the ten different formazin turbidity levels that were generated at the

Fort Collins site. Prior to spiking the formazin, the filtered water sample was analyzed for approximately 30-

minutes prior to commencing the first spike. This baseline served as the blank for that respective instrument. The

filtered water was then spiked with known quantities of a defined formazin standard solution into a sample stream

with a known flow rate. This allowed for the calculation of the theoretical turbidity value. As each turbidity spike

was perfumed, the data was plotted (trended) graphically in real time. The initial ramp up of the turbidity

measurements (trace) was observed for each of the test instruments. Once all these traces were stable (trending

horizontally), the data collection count was noted. At this point of a stable turbidity level in the sample stream, the

injection continued at the constant rate until at least 60 measurements were logged for each of the instruments.

These 60 measurements were then used in the precision and bias calculations for each of the different turbidity

levels (i.e. spikes).

The derivation of the theoretical value for each spike was from the calculations that were provided in Section 6 of

the validation plan, under the section titled “Spike Injection Method”. This section described how a defined

turbidity standard was spiked into the flowing sample of filtered tap water. Equations 1 through 3 provide the

calculation of the dilutions that are performed on the spiked standard to ultimately yield a stable level of known

turbidity that ultimately flowed through each instrument. The Microsoft Excel workbook for the Fort Collins test

site contains a spreadsheet titled “Injection Summary” (see Table 4) that includes the embedded formulas used to

yield the theoretical turbidity of each spike.

A given spike, that was stable, contained 60 measurements. The mean, standard deviation and percent relative

standard deviation were determined from these measurements. These results were used as the reported value for the

given spike. This was performed for a total for 10 spikes (i.e. turbidities) that covered the range of 0.01 to 10 NTU.

The majority of the spikes were in the 0.010 to 1 NTU range, as that range of turbidity was most critical for

reporting and filtration optimization purposes. Each spiked turbidity level had the calculated theoretical value that

would be used for percent recovery calculations.

Percent recovery calculations were determined for each candidate and the reference instrument. The results are

provided in Tables 7, 8 and 9 for the Lovibond White light LED method, the Lovibond 660-nm LED method, and

the Lovibond Laser Method respectively. The percent recovery calculations were presented in Section 6 of the

validation plan (last paragraph). The analysis was performed by dividing the test instrument response by the

theoretical value of the response for each spike. This was performed on blank corrected and non-blank corrected

responses. However, both the candidate and test instruments have blank correction features and thus, the blank

corrected values were used in the reported percent recoveries. Percent recoveries were analyzed for discrete

turbidity ranges that were between 0.00 and 0.100 NTU, 0.100 and 1.00 NTU and between 1.0 and 10 NTU. For

each of these ranges, the averaged recovery was calculated and reported for in the respective method for each of the

three candidates.

Precision was calculated through the derivation of the standard deviation for each of the spiked turbidity levels.

Table 6 provided the calculated precision for the three candidates and reference methods. Consistent with the

percent recovery data, the precision was categorized in the ranges of 0.00 and 0.100 NTU, 0.100 and 1.00 NTU and

between 1.0 and 10 NTU. For each of these ranges, the averaged precision was calculated and reported for in the

respective method for each of the three candidates.

42

The analysis of linearity was determined for the three candidates and reference instruments (see Table 5). For each

instrument, a least squares regression line was derived between the theoretical turbidity and the averaged response

for the ten spikes. The r-squared value could then be used to determine if the respective response instrument’s

response was compliant to the linear response over the test range of 0 to 10 NTU.

In calculating the correlation coefficient from 0-1 NTU, all the instruments had a value of 0.9999 or better. The

accuracy degraded from less than 1 percent to less than 2 percent over this range on the PTV 1000. The PTV 2000

and 6000 retained accuracy that was better than 1 percent over this range, and is slightly better than the reference.

The calculations are in Table 1B on the tab “Fzn Spike and Recovery Data” that is in the Microsoft Excel Work

Book titled Ft Collins Filt Tap P&B Test Site.xls.

An additional analysis was performed on the percent recovery data. A statistical ANOVA analysis was performed

on 1) the entire averaged response data set for all instruments; 2) the blank corrected and the non-blank corrected

percent recovery data for all instruments; and 3) the separated data sets between each of the candidate and reference

instruments. With respect to the ANOVA analysis, if the F value is less than the F-critical value, the data sets are

not statistically different relative to each other. In other words, the differences between the data sets are likely to be

by chance. ANOVA results for these different groups of data were consistently the same. The F values were always

less than the respective F-critical value, indicating there was no statistical significance between any of the three

candidate methods and the reference method.

The analysis of the data from the two drinking water plants was broken down into 8-hour blocks of time (when

appropriate), which represented approximately 1920 data points per instrument per 8-hour block. Any remaining

data that did not add up to a full 8 hours were also analyzed. Additionally, any spikes of unfiltered water into the

effluent stream were analyzed separately. Finally, the entire run at the test site was analyzed as a whole. For each

data set, the average (mean), standard deviation and percent relative standard deviation was determined. This data

was then pasted into a table so the different blocks of data could be compared with respect to the average and

standard deviation. After review of the blocks of data, the means compared closely to each other for a given site.

Thus, for reporting purposes, the entire run was reported for each test site. When comparing the three candidates to

the reference methods, the net difference in turbidity between each candidate and the reference method was

calculated and reported. This analysis approach was performed for both the Binney South Platte and the San Pat

MWD waters. This data are presented in Tables 11 and 13 respectively.

Data comparison between the Lovibond White Light LED method and the EPA approved Method

10133

Table 18 provides a comparison between these two methods over the test range of the candidate method. The key

performance parameters for these methods include the range of percent recoveries for the test range of 0 to 10 NTU,

the average precision over the test range of 0-10 NTU, the linearity, limit of detection, and the reporting limit for

each method. The two right columns compare the net measurement difference between the two methods for each of

the two different drinking water plant filter effluent samples.

The range of percent recoveries is very close between the two methods with the candidate White Light LED method

exhibiting a slightly higher percent recovery at the lower turbidity spikes. The cause of this deviation is primarily

due to the additional stray light that was present in this candidate method. However, the instrument does have a

blank subtraction feature (which was not used during testing); the stray light impacts could be minimized. An

ANOVA analysis was performed between these two methods on the percent recovery data and showed there is no

statistical significance between them (F was less than F-critical). The linearity of each method was very high, with

43

correlation coefficients both exceeding 0.999. The precision of the two methods is within 0.003 NTU, with the

candidate method having slightly poorer precision.

Although not stated in the candidate or reference method, an estimated limit of detection was performed by taking

the averaged precision for the lowest three turbidity spikes for each method. This value was multiplied by a factor

of 3 to generate a conservative estimated LOD. The estimated limit of quantitation (LOQ) could be determined

using the same precision and it was below the method reporting level at its lowest turbidity range. It was calculated

as 10 times this average precision from these lowest three turbidity spikes and provides an estimated LOQ.

The robustness of the candidate and reference method was compared at the two drinking water sites. At both sites

the overall turbidity response of the approved reference method was lower than the candidate method. The

additional response by the candidate method was likely due to three factors. The first was additional stray light

exhibited in the candidate method and second, the candidate method does utilize a light source with lower-

wavelengths of light that scatter light more efficiently by small particles. Third, the lower wavelengths of incident

light may exhibit fluorescence effects from dissolved residual compounds that may be present in the sample. At the

San Patricio test site, the filtration of the sample is through an absolute barrier that passed integrity testing. The

sample has virtually no turbidity. Thus, the elevated readings that were only observed with the white light LED

instruments indicate this fluorescence effects may the major contributor to the elevated readings, along with some

elevated stray light. At the San Patricio test site, the reference instrument was measuring at approximately 10

mNTU during the studies which is indicative of no turbidity In addition, there could be some fluorescent effects

from dissolved materials that result with the with light sources at the lower wavelengths that are near 400 NTU. The

concern with the white light method is that stray light is very difficult to quantify and the contribution of stray light,

dissolved particle fluorescence, it was the combination of these factors that resulted in the slightly elevated turbidity

levels in the candidate method’s instrument. In practice, the positive bias of candidate method relative to the

reference method provided a conservative approach relative to reporting limits in that it was favorable to have a

false positive bias versus a false negative bias. The positive bias is an offset value that was not impacted by the

spike events that were directed in these studies in that the absolute response was observed for all spikes and was

comparable to the reference method.

The three test sites provided the opportunity for the methods to demonstrate their respective responsiveness to

turbidity spikes and recoveries from turbidity spikes. The candidate method detected all turbidity spikes that were

detected by the reference method, which was indicative of the robustness of the candidate method.

The quality controls that were followed in this ATP demonstrated that they were appropriate for the candidate test

method as there were no data deviations or events that could be traced to any inadequacy of the QC approach that

was utilized.

Table 18 – Summary of Method Performance between the Lovibond White Light LED and the Reference method 10133

Method % Recovery

Range (0-10

NTU)

Average

Precision (0 to

10 NTU)

Linearity

(0-10 NTU

Limit of

Detection

(Estimate)

Method

Reporting

(lowest

range)

Net

Difference

Binney (All

Data)

Net

Difference

San Pat

MWD (All

Data

Lovibond WL LED

Candidate

96.5 – 110.8 0.0086 0.99962 0.0018 0.01 +0.027 +0.045

10133 (Approved) 97.1 – 102.3 0.0056 0.99972 0.0006 0.01 -0.027 -0.045

At the time of this ATP, the reference method was commonly regarded as the state-of-the art turbidity method in the

industry. The FilterTrak 660 Laser Nephelometer was commonly used to measure low-level turbidity samples and

44

was considered to be an effective tool that could be used in the optimization of filtration processes. However, the

technology does have drawbacks that have prevented its broader use in drinking water filter effluent applications.

This was primarily due to expensive optical components (and instrumentation), difficulties in maintenance, and

difficulties in performing calibrations. These are unique challenges that do not always translate back to the

statistical analysis of the method but should be considered when a method (and its representative instrumentation)

was considered for use. The candidate Lovibond White Light LED method has been designed to deliver

representative instrumentation that resolves many of the challenges that were mentioned with the reference method’s

instrumentation. The white light source was well known and users have requested a better, more stable light source,

which candidate method provided. Although this candidate method does not statistically meet to the high level of

performance of the reference method in all statistical categories, it does deliver the combination of features and

performance that will allow users to adopt its respective instrumentation to ultimately deliver reliable turbidity

results over time.

Due to the uniqueness of the candidate method to be susceptible to the combination of: fluorescence effects from

dissolved compounds within some samples, higher scatter efficiency from small particles, and additional stray light

from a polychromatic light source, provisions have been incorporated into this method to address this interference.

These include the instructions on how to determine the blank value of the sample that can then be subtracted from

the measurements, which would be applicable to the measurement of samples below 0.100 NTU.

Data comparison between the Lovibond 660-nm LED method and the EPA approved Method 10133

Table 19 provides a comparison between these two methods over the range of the candidate method. The key

performance parameters for these methods include the range of percent recoveries for the test range of 0 to 10 NTU,

the averaged precision over the test range of 0-10 NTU, the linearity, limit of detection, and the reporting limit for

each method. The two right columns compare the net measurement difference between the two method’s

representative instrumentation for each of the two different drinking water plant filter effluent waters.

The range of percent recoveries are very close between the two methods with the candidate Lovibond 660-nm LED

method exhibiting a slightly higher (2%) percent recovery at the lower turbidity spikes. The cause of this deviation

was primarily due to the slightly higher stray light that was present in the candidate method’s instrument. However,

the candidate and reference instruments have a blank subtraction feature (which was not used during testing), and

the stray light impacts can be minimized. An ANOVA analysis was performed between these two methods on the

percent recovery data and it concluded there was no statistical significance between them (F was less than F-

critical). The linearity both the candidate and reference methods were high and essentially equivalent, with their

respective correlation coefficients exceeding 0.999. The precision of these two methods was within 0.0008 NTU

which was essentially equivalent with respect to each other.

Although not stated in either the candidate or the reference method, an estimated limit of detection was performed

by taking the averaged precision for the lowest three turbidity spikes for each method. This value was multiplied by

a factor of 3 to generate a conservative LOD. The LOD of the Lovibond 660-nm LED method was 0.0003 NTU

higher than the reference method. The limit of quantitation (LOQ) was determined using these same precision

values as the LOD. The LOQ was under the method reporting level at its lowest turbidity range.

The robustness between the candidate and reference methods was compared at the two drinking water sites. Both

sites exhibited the overall turbidity response of the approved reference method was slightly lower than the turbidity

response of the candidate method by less than 0.010 NTU. The higher response by the candidate method was likely

due to slightly elevated stray light, but this error would be captured in the instrument specification for the candidate

method’s representative instrument. In practice, the slight positive bias of candidate method over the reference

method provides a conservative approach relative to reporting limits in that it was more favorable to have a false

45

positive bias versus a false negative bias. This is because in turbidity there is always positive bias due to the

interferences discussed in this report. Some manufacturers attempt to subtract out the interference through the use of

measuring a very low turbidity calibration standard, which is both difficult to prepare measure. This approach

adjusts the calibration gain and not simply the offset. A more conservative approach which is practiced by these

methods is to design a highly linear measurement system where the dependence on the preparation of low turbidity

standards is not require to perform a successful and accurate calibration.

The three test sites provided the opportunity for these two methods to demonstrate their respective instrument’s

responsiveness to turbidity spikes and recoveries from these turbidity spikes. The candidate method’s instrument

detected all turbidity spikes that were detected by the reference method’s instrument, which was indicative of the

robustness of the method.


method as there were no data deviations or events that could be traced to any inadequacy of the QC approach that

was followed.

Table 19 – Summary of Method Performance between the Lovibond 660-nm LED and Reference method 10133

Method % Recovery

Range (0-10

NTU)

Average

Precision (0 to

10 NTU)

Linearity

(0-10 NTU

Limit of

Detection

(Estimate)

Method

Reporting

(lowest

range)

Net

Difference

Binney (All

Data)

Net

Difference

San Pat

MWD (All

Data

Lovibond 660-nm

LED (Candidate)

93.7 – 104.5 0.006 0.99970 0.0008 0.010 +0.009 +0.002

10133 (Approved) 97.1 – 102.6 0.006 0.99972 0.0006 0.010 -0.009 -0.002



was considered to be a tool that could be used in the optimization of filtration processes. However, the technology

does have drawbacks that have prevented its broader use in drinking water filter effluent applications, which was

primarily due to expensive optical components (and instrumentation), difficulties in maintenance, and difficulties in

performing calibrations. These are unique challenges that do not always translate back to the statistical analysis of

the method but should be considered when a method is considered for use. The candidate Lovibond 660-nm LED

method was designed to deliver instrumentation that resolves many of the challenges that were mentioned with the

reference method. The 660-nm LED source was very comparable to the laser nephelometer with respect to all of the

statistical evaluations in this study. This candidate method was statistically equivalent to the reference method and

can deliver a high level of measurement performance, with reduction in instrument cost, maintenance and effort to

perform calibration and QC. Ultimately, the Lovibond 660-nm LED Method delivers the combination of equivalent

performance and improved features relative to the reference instrumentation to ultimately deliver reliable turbidity

results over time.

Data comparison between the Lovibond 6000 Laser Method and the EPA approved Method 10133

Table 20 provides a comparison between these two methods over the range of the candidate method. The key

performance parameters for these methods included the range of percent recoveries for the test range of 0 to 10

NTU, the averaged precision over the test range of 0-10 NTU, the linearity, limit of detection, and the reporting limit

for each method. The two right columns compare the net measurement difference between the two methods for each

of the two different drinking water plant filter effluent waters.

46

The range of percent recoveries between these two methods was nearly equivalent. The candidate Lovibond 6000

Laser Method exhibited a slightly higher (0.6%) percent recovery at the lower turbidity spikes. The small difference

in recovery was likely due to experimental errors. An ANOVA analysis was performed between these two methods

on the percent recovery data and showed there was no statistical significance between them (F was less than F-

critical). Essentially the differences were likely due to chance. The linearity of each method was very high and

essentially equivalent, with correlation coefficients for both methods exceeding 0.999. The precision of the

Lovibond 6000 Laser Method was slightly poorer than the Reference Method. However, the higher variability could

be due to individual particle influence when in the measurement view volume. This variability can be used as an

analysis parameter when optimizing filter performance.

Although not stated in either method, an estimated limit of detection was performed by taking the averaged

precision for the lowest three spikes for each method. This value was multiplied by a factor of 3 to generate a

conservative LOD. The LOD of the Lovibond 6000 Laser Method was approximately double the LOD of the

reference instrument. This could be due to the influence of single particle variability that was better observed on

this candidate method. The limit of quantitation (LOQ) was determined using the same precision values as the

LOD and was under the method reporting level at the lowest turbidity range.

The robustness of these two methods was compared at the two drinking water sites. Both sites showed the overall

turbidity response of the approved reference method’s instrument was lower than the candidate method’s instrument

by an average of 0.009 NTU at the Binney South Platte Site, but was then higher than the candidate instrument by

0.0003 NTU at the San Pat MWD membrane site. The two water plant sites showed that the Lovibond Laser 6000

method did exhibit a higher response to turbidity spikes than the reference turbidimeter. During the filter runs at the

Binney South Platte Site (Figure 4), the two laser methods showed additional sensitivity to particle penetration

through the filter as the run progressed. This was observed as the increase in the measurement baseline as the filter

run progressed. However, the Lovibond 6000 method exhibited increased sensitivity to turbidity as the run

progressed when compared to the reference method. Both methods’ representative instruments exhibited the

enhanced sensitivity that would be expected from a laser-based method and would be ideal for reporting and process

optimization at low turbidity levels.

In Table 20, the precision is averaged across the entire range of 0 to 10 NTU tested. However, this average is biased

high from the spikes in the highest range which was from 1 to 10 NTU. For measurements below 1 NTU, the

precision was 0.0004 NTU up to 0.100 NTU and 0.0044 NTU from 0.100 to 1.00 NTU. Between 1.0 and 10 NTU,

the precision averaged 0.048 NTU. Thus, the method will have two reporting limits. Below 1 NTU, the reporting

limit will be to the nearest 0.010 NTU and at 1.0 and greater NTU it will be 0.050.


method as there were no data deviations or events could be traced to any inadequacy of the QC approach that was

followed.

Table 20 – Summary of Method Performance between the Lovibond 6000 Laser Method and Reference method 10133

Method % Recovery

Range (0-10

NTU)

Average

Precision (0 to

10 NTU)

Linearity

(0-10 NTU

Limit of

Detection

(Estimate)

Method

Reporting

(lowest

range)

Net

Difference

Binney (All

Data)

Net

Difference

San Pat

MWD (All

Data

Lovibond 685-nm

Laser (Candidate)

94.3 – 103.4 0.0163 0.99963 0.0013 0.010 +0.009 -0.0003

10133 (Approved) 97.1 – 102.6 0.0056 0.99972 0.0006 0.010 -0.009 +0.0003

47



was considered to be a tool that could be used in the optimization of filtration processes. However, the technology

does have drawbacks that have prevented its broader use in drinking water filter effluent applications, which was

primarily due to expensive optical components (and instrumentation), difficulties in maintenance, and difficulties in

performing calibrations. These are unique challenges that do not always translate back to the statistical analysis of

the method but should be considered when a method was considered for use. The candidate Lovibond 6000 Laser

Method was designed to deliver instrumentation that resolved many of the challenges that were mentioned with the

reference method’s instrument. The 685-nm Laser source was very comparable to the laser nephelometer with

respect to all of the statistical evaluations in this study. This candidate method was statistically equivalent to the

reference method and can deliver a similar high level of measurement performance as the reference method, with

reduction in instrument cost, maintenance and effort to perform calibration and QC. Ultimately, the Lovibond 6000

Laser Method delivered the combination of equivalent performance and slightly improved sensitivity to the presence

of low numbers of particles that eventually penetrate a filter as its run progressed. Similar to the reference method,

this candidate method can serve the purpose of being adequate for regulatory monitoring and as a tool for

optimization of filtration.

5.0 Conclusions

This Turbidity ATP test plan was designed for the synchronous evaluation of the three candidate test methods that

were presented by Lovibond, a Trademark of Tintometer Inc. The three methods were defined as the following in

this validation report:

1. The Continuous Measurement of Turbidity using the Lovibond White Light LED Method. The

representative instrument discussed herein was the PTV 1000 Turbidimeter. This method was successfully

tested with the other two proposed ATP methods using the appended validation plan.

2. The Continuous Measurement of Turbidity using the Lovibond 660-nm LED Method. The representative

instrument discussed herein was the PTV 2000 Turbidimeter. This method was successfully tested with the

other two proposed ATP methods using the appended validation plan.

3. The Continuous Measurement of Turbidity using the Lovibond 6000 Laser Method. The representative

instrument discussed herein was the PTV 6000 Turbidimeter. This method was successfully tested with the

other two proposed ATP methods using the appended validation plan.

This validation study had three key objectives. The objectives were to effectively demonstrate method equivalency

between the EPA approved reference Method 10133 and each of the proposed ATP candidate methods.

First was to determine comparability for each of the candidate methods to the reference Method 10133 with respect

to precision and bias in the turbidity range of about 0.010 to 10 NTU. Both precision and bias was determined for

each candidate method and for the reference method. Statistical analysis of the precision and bias data for each

candidate method confirmed equivalency of performance with respect to the reference method.

The second objective of this study was to demonstrate linearity of each candidate method over the range of 0-10

NTU. This required a carefully designed test plan that could generate on-line samples that were characterized with a

stable and known turbidity level(s) over time. This was necessary in order to collect run-time data on each turbidity

spike of a defined value, and allowed for an adequate amount of data to be collected to perform statistical analysis.

The success in testing did deliver the required stable turbidity values for each of the three candidate methods and

least squares analysis between measured and theoretical turbidities for each spike was calculated. This analysis

demonstrated high linearity for the three candidate methods with respective correlation coefficients that exceeded

0.999 over the range of the testing.

48

The last objective of this study was to derive comparison data between the candidate methods and the reference

methods at two drinking water plants. These plants treated very different source waters and used different filtration

processes. The study succeeded in procuring on-line analysis time at two different plants that allowed concurrent

collection of comparability data for the three candidate and the reference methods. All data that was collected

between an initial and a final QC (at each site) was used to demonstrate method comparability and equivalency

between the candidate and reference methods.

This ATP study exceeded the requirements and expectations of the study objectives and provided the necessary

evidence to demonstrate method comparability and equivalency between these three candidate methods and the

reference method for the measurement of turbidity between 0.010 and 10 NTU.

49

Appendix A

Confidential

Alternate Test Procedure Method Validation Plan

Revision 1.0

Proposed ATP Methods:

1. The Continuous Measurement of Turbidity using the Lovibond White Light

LED Method

2. The Continuous Measurement of Turbidity using the Lovibond 660-nm LED

Method

3. The Continuous Measurement of Turbidity using the Lovibond 6000 Laser

Method

April 22, 2016


6456 Parkland Drive

Sarasota, FL 34243

Michael Sadar


2108 Midpoint Drive, STE 1

Fort Collins, CO 80525

970-682-8148

[email protected]

mailto:[email protected]

50

Table of Contents

1.0 ..................................................................................................................................... Introduction

.......................................................................................................................................................... 51

2.0 ..................................................................................................................................... Background

.......................................................................................................................................................... 51

3.0 .................................................................................................................... Scope of this Test plan

.......................................................................................................................................................... 52

4.0 ............................................................................................................................... Study Timelines

.......................................................................................................................................................... 53

5.0 .................................................................................................................... Materials and Methods

.......................................................................................................................................................... 54

6.0 ............................................................ Test Protocols – The Technology Comparability Test Plan

.......................................................................................................................................................... 56

7.0 ................................................................................................................................ Data Collection

.......................................................................................................................................................... 59

8.0 ............................................................................................................................................. Results

.......................................................................................................................................................... 63

9.0 ..................................................................................................................................... Conclusions

.......................................................................................................................................................... 64

10.0 ..................................................................................................................................... References

.......................................................................................................................................................... 65

11.0 ........................................................................................................................................... Figures

.......................................................................................................................................................... 65

51

1.0 Introduction

This study plan was for the continuous measurement of turbidity between 0 and 10 NTU.

The study plan was designed for application of the monitoring of turbidity from drinking

water plant filter systems and from combined filter effluent systems. Specifically, this

study plan is designed to determine the precision and bias of the candidate ATP methods

over the range of turbidity up to 10 Nephelometric Turbidity Units (NTU’s).

This test plan is designed for the synchronous evaluation of the following candidate test

methods:

1. The Continuous Measurement of Turbidity using the Lovibond White Light LED

Method. The representative instrument discussed herein is the PTV 1000

Turbidimeter.

2. The Continuous Measurement of Turbidity using the Lovibond 660-nm LED


Turbidimeter.

3. The Continuous Measurement of Turbidity using the Lovibond 6000 Laser


Turbidimeter.

These three methods are identical with respect to design, fluid hydraulics, software,

operational procedures, data generation, and results reporting. The difference in the three

methods was with the type of light source used. Otherwise, the optical geometry that

includes the incident light source, the detection system, and the pathlength are identical.

The candidate methods will be compared to a reference instrument that complies with the

EPA accepted method 10133. The instrument is the Hach FilterTrak 660.

The proposed methods are listed separately, but they are discussed collectively herein to

simplify the understanding of the differences each has relative to the other methods and

to historical methods. When denoted collectively, they are referred to as the PTV

1000/2000/6000.

2.0 Background

These new methods utilize numerous state-of-the art technological advancements that

have been coupled with proven design criteria that have been utilized by the Drinking

Water Plant (DWP) community and its regulatory partners over the past several decades.

52

Ultimately, these technologies provide the generation of and rapid interpretation of

turbidity measurement data is critical to the mitigation of any risks associated with the

breakdown in the water treatment process.

The turbidimeter versions are identical in their design with the exception of the light

source. One version, the PTV 1000 utilizes a white light LED, a source that is essentially

the same as the incident light source used in the EPA approved Swan Turbidiwell1

Method. The second version, the PTV 2000 contains a red light emitting LED that emits

light at peak intensity within the visible spectrum at a wavelength between 650 and

670nm, (typically at 660 nm). The spectral output from this source is comparable to the

Mitchell Method M52712 and Hach Method 101333. The third light source is a 685-nm

laser diode source that is comparable to Hach method 10133. These three light sources

provide several advantages over the historical tungsten filament light sources which are

discussed in detail later in this document.

The sample hydraulics through these instruments is identical. This includes

manufacturer’s recommended flow rate ranges, sampling requirements and instrument

settings.

3.0 Scope of this Test plan

It is understood that technologies (i.e. new methods) that differ from EPA Method 180.1

require a performance-based approval4. This performance comparison will be using the

accepted EPA approved reference method, Hach Method 10133. This is the FilterTrak

660 measurement technology that complies with Method 10133.

This test plan is designed to collectively deliver the following data:

1. Precision and bias data at several turbidity levels up to about 10 NTU. Bias is

determined as percent recoveries to theoretical spikes of turbidity over a baseline.

2. Direction comparison between the candidate method and reference method on

real-world drinking water plant filter effluent samples.

3. Demonstration of linearity over the range of about 0.010 and 10 NTU.

The purpose of this test plan is to generate and deliver comparability data between the

PTV 1000, 2000, and 6000 with the white light LED, 660-nm red LED, and 685-nm laser

diode light sources respectively (i.e. the test instruments) and a reference instrument that

is considered to be the regulatory benchmark in the drinking water plant (DWP) industry,

the FilterTrak 660. Comparability data will be on three different water sources in which

water from the same source will flow in parallel to each of the test instruments and the

reference instrument. In addition, one of the waters will be spiked with known levels of

turbidity (i.e. formazin) across the operational range of the instrument (from 0-10 NTU)

and percent recoveries (bias) and precision data will be generated. All test instruments

53

will be set up and then calibrated according to the respective manufacturers

specifications.

This testing has been designed to collect data such as that which is presented in the most

recent EPA approvals for turbidimeters, i.e. the Swan Turbiwell and Mitchell Method

M5271.

4.0 Study Timelines

Once study plan approval is received, testing will commence within 30 days. The

proposed schedule is as follows:

1. Precision and bias testing to be completed first.

2. Water treatment plant comparability testing at Aurora Colorado second.

3. Water treatment plant comparability testing at San Patricio MWD, Ingleside,

Texas.

4. Validation Report to be generated within 45-days after the completion of the field

testing.

Table 1 provides the details of the proposed plants that have committed to be test sites at

the time this plan was proposed.

Table 1 – Proposed test sites for the EPA ATP involving the Lovibond PTV

1000/2000/6000Turbidimeters.

Test Site Type of Water Type of Treatment Contact Name

and Title

Status

Tintometer

Inc., Fort

Collins Co

City Tap Water

that originates as

surface water

from snowmelt in

the Colorado

Rocky Mountains.

Conventional Dual Media

Filtration to generate the “tap”

water. This is followed with

filtration through a size

exclusion membrane with

nominal pore size of 0.05 um

prior to entering the test panel.

Mike Sadar,

Manager of

Research and

Development

Confirmed

participant

San Patricio

WTP, Ingleside

Texas

Surface water

with elevated

ambient

temperatures.

Conventional

flocculation/sedimentation

followed by microfiltration

Jake Krumnow,

Supervisor of

Operations and

Maintenance

Confirmed

participant

Binney

Filtration Plant,

Aurora

Colorado (a

Partnership for

Safe Drinking

Water Plant)

South Platt River,

taken from that

includes discharge

from Denver

Metro Wastewater

Plant

Advanced UV peroxide

Oxidation, followed by Dual

Media Filtration

Kevin Linder,

Supervisor of

Operations and

Maintenance

Confirmed

participant

54

5.0 Materials and Methods

The new methods and representative instrumentation are described in full detail in the

document titled “Justification for a New ATP for the Continuous Monitoring of

Turbidity.” An abbreviated summary of this document is provided below:

Figure 1 is a Picture of the PTV 1000 Turbidimeter, along with its power supply and

sample fluidics module. As mentioned previously, the PTV 2000 and PTV 6000 are

identical in design with the exception of the incident light source. Figure 5 provides

additional detail to the features of these instruments.

The construction details and features of the turbidimeter system enable an

environmentally sound, fast and easy approach to calibration. The performance

characteristics of the turbidimeter, (the combination of low stray light and a highly linear

conversion of scattered light to turbidity over the applicable regulatory range), enable the

device to be calibrated using a single turbidity standard. The calibration standard is

easily prepared in an easy-to-use, single dose package. Exceptional linearity enables the

calibration standard can be prepared at an elevated turbidity value (such as at 5.0 NTU)

which minimizes dilution errors due to residual sample within the fluidic body. This

approach has been proven to be a key factor for reliable and accurate turbidity

measurement.

Table 2 provides a summary of the advantages that this proposed method will have over

existing methods. In addition, advantages of this design that extend beyond the actual

turbidity measurement are also included.

Table 2– Summary of the Design features for the proposed EPA methods on turbidity and the

advantages over EPA Method 180.1

Feature Advantage

White Light LED (Incident

Light Optics)

Solid State – Low drift; low output temperature dependence of LED light

source.

Long Life (10 years life expectancy)

Collimated beam– Uniform and parallel light rays as they pass through the

sample to minimize stray light

Peak response between 400-600 nm; sensitive to a broad range of particle

sizes.

Heated optics; Eliminates instability and erroneous measurements due to

condensation

ILS Monitor Detector; Compensates for LED drift over time and

temperature.

660-nm Red LED All advantages above except, the peak response is between 630 and 660

nm, which reduces interference due to dissolved organics and sample color

Reduced spectral bandwidth; reduces stray light and increases the limit of

detection.

685-nm Laser Highly collimated beam of high energy and small diameter reduces stray

light and improves the limit of detection

Narrow beam of high energy is sensitive particles in very low

55

concentrations that can be pre-cursers to a larger turbidity event.

Beam Dump Absorbs beam energy after passing through measurement chamber and

reduces stray light.

Scattered Light Detector Orthogonal to the Incident light Beam – Sensitive to scatter from a range of

particle sizes and shapes.

Controlled aperture angle – improves intra-instrument consistency in

detection.

Heated optics with no air spaces between the sample and detector –

eliminates instability due to condensation.

Responsivity overlaps the spectral output of the incident light source for

improved sensitivity.

Short total path length of 5.5 cm yields a highly linear response over the

regulatory range of interest (0-10 NTU) and simplifies the calibration

protocols.

Large collection angle; improves the limit of detection.

The turbidimeter body Reduced Volume – improves response time, reduces sample settling,

minimizes sample usage and minimizes calibrant usage.

Integrated bubble trap – removable without tools, front accessible, easy to

clean and low sample retention.

Void of tight corners – easy to clean

Polished fluid handling surfaces reduce scale, fouling and bubble

formation.

Comprised of absorptive (black) material – reduces internal light reflections

(interferences that contribute to stray light).

Measures at Atmosphere – eliminates any sensitivity to flow and pressure

changes in the sample line (i.e. water hammers).

“V” measurement chamber form factor – Prevents particulate settling and

reduces stray light.

Flow monitor – Confirms sample flow through the measurement chamber

(alarms and warnings can be set for both high and low flow conditions). To

ensure measurement integrity.

Multiple internal weirs – ensure consistent sample throughput and increases

instrument robustness

Optimized sample handling – sample temperature does not change as it

passes through the instrument, thereby minimizing changes in sample

composition and reduces bubble formation.

Complete Measurement

System (Body and

Measurement module)

Reduced stray light – leads to simplified and robust calibration protocols

Enhanced detection limit (0.002 NTU for White Light LED, 0.0005 NTU

for 660-nm Red LED, and 0.0003 NTU for the 685-nm Laser Diode)

Highly linear response over the range 0-10 NTU. This allows for robust

and simplified calibration protocols.

Elimination of common low-level interferences (bubbles, stray light,

particle settling.

Self-aligning magnetic positioning of the measurement module on the body

– ensures the proper alignment of the measurement module to the fluidic

body.

Redundant interfaces (Smart Device and Touchscreen).

Redundant data and meta data storage.

Both wired (USB) and secure wireless (Bluetooth) communication for

operation of the instrument (User interface)

Multiple outputs for both digital and analog communication streams (i.e.

Modbus, 4-20 mA)

56

6.0 Test Protocols – The Technology Comparability Test Plan

The purpose of this test plan is to generate comparability turbidity data between the

proposed PTV 1000/2000/6000 technologies and referenced approved EPA technologies.

The plan involves the testing of the PTV 1000/2000/6000 and PTV 2000 Turbidimeters,

one device equipped with a White LED, the second device equipped with a 660-nm red

LED, and the third device equipped with a 685-nm laser diode respectively. A reference

turbidimeter is used for comparability of results. The reference turbidimeter will be the

Hach FT660sc Laser Nephelometer. The reference turbidimeter was purchased directly

from Hach Company. All devices will be run on the same sample waters and exposed to

the same spiking protocols throughout the testing. This setup will be referred to as the

test panel.

The comparability testing will involve the monitoring three different waters with on-line

turbidimeters. The plan will be designed to include an alternative test site. This site will

be used in lieu of unforeseen circumstances that render a site or its data invalid. Table 1

provides a list of the proposed sites for this study. Two of the sites will be simple

measurement comparability studies on during a typical filter run. The third study will

involve the spiking of a filter effluent stream with turbidity standards to generate percent

recovery data over the specified test range.

The test panel (with two test devices and one reference device) will be installed to

monitor filter effluent water, for minimum of 24 hours at each site. The sample water

will be split into four tap streams, one feed line branching to each turbidimeter. The flow

for each stream will be adjusted to meet the manufacturer’s requirement for the

respective instrument. Ideally, this will be the middle of the flow range for each

instrument. After the sample flows through the instruments, the discharge will flow to

drain. Figure 2 shows the proposed hydraulic plumbing for the test and reference

instruments.

Calibration of each device on the test panel will take place after setup and all pluming

connections are completed at each of the respective test sites. Calibration will be

performed after each device has been cleaned according to the respective manufacturer’s

instructions. Freshly prepared, EPA approved formazin standards will be used as the

calibrant. If dilutions are needed, this will be made with filtered water that has been

processed through a 0.2 um or smaller filter. The calibrations will be performed within

the actual device bodies, i.e. no calibration cylinders will be used.

The test devices will be setup according to operating instructions per the respective

instrument manuals. The setups will include the recommended signal averaging times,

bubble rejection algorithms, and displayed measurement resolution. The measurement

(data) log rate will be set to 15-second intervals for the duration of the study. Data will

be logged into each of the respective instrument data log files until the measurement run

57

for the site has been completed. This data, along with date and time stamp (to the nearest

second) will then be exported into an Excel spreadsheet for statistical analysis.

After calibration and prior to data collection, a quality control sample (QCS) will be

prepared and run through each instrument. The QCS will be a fresh prepared formazin

standard that will be checked on a laboratory turbidimeter (e.g. a Hach 2100N). A

second QCS will be run after the completion of the data run to confirm system

performance.

The Spike Injection Method

The Fort Collins test site will be used for the turbidity spike recovery portion of this test

plan. This will quantatively generate the percent recovery (i.e. accuracy) of each

intended turbidity spike. This spike data is necessary to demonstrate performance

throughout the test range of 1 to 10 NTU. This portion of the study will also be used to

generate the precision data.

The spike injection method involves a minor modification of the test panel used for the

comparability testing at the different sites. The modification is the incorporation of a

peristaltic pump. This pump will continuously inject a prepared turbidity standard into a

flowing sample stream. The turbidity standard is a freshly prepared formazin standard

and is of a volume that will allow for an adequate stabilization of each spike that is

necessary for the percent recovery calculation.

Figure 3 is the schematic of this modified test panel for the spike injection method (SIM).

The theory of the SIM is detailed as follows. First, the incoming water (the sample

stream) flows at a constant turbidity and flow rate. This is the baseline or blank water. A

series of filters and valves are utilized to ensure the consistency of this blank over the

duration of the testing. Second, a peristaltic pump is used to inject a defined turbidity

standard at a constant flow rate into the sample stream. The flow rate of both the sample

stream and the injected, turbidity standard are known and flow at a constant rate. The

blending of this spiked standard with the sample stream results is a level of turbidity

within the sample stream. Third, the spiked turbidity sample stream flows through a

mixing coil and is then split into four branches originating from the single feed line, each

branch leading to either a device under test or the reference instrument. Excess sample

simply runs to the overflow drain.

A combination of different turbidity standards and different injection rates will deliver

stable turbidity values of different concentrations. This approach allows for the delivery

of a continuous stream of sample at varied turbidity concentrations into the devices under

test and reference instrument under normal operating conditions.

The specific details of these key elements of this spike injection methodology are

discussed in more detail.

1. The incoming tap water (the sample stream) is filtered through a set of size

exclusion filters that removes all particles of a size greater than 0.03 microns.

58

This system virtually removes all turbidity from the system but does not remove

any dissolved solids such as residual hardness. The system is sized to allow

continuous and adequate flow through all instruments on the test panel. The

turbidity level of this water is also constant and provides the baseline turbidity for

this study. The baseline turbidity is typically in the range of 0.015 to 0.020 NTU,

depending on the instrument that is used to measure it. As mentioned previously,

this is the blank.

The turbidity of the blank will be derived from the measurement of this filtered

tap water prior the start and then at the conclusion of the spike injections. It will

be derived for each instrument. Approximately 30 minutes of data will be taken

prior to the first spike. At the completion of the spikes and after the sample

stream has become stable with respect to the reference instrument, an additional

30 minutes of monitoring and data collection will occur. The combined data will

then be averaged to calculate the turbidity value of the blank. As mentioned

above, this value will be in the 0.015 to 0.020 NTU range.

2. The flow rate of the incoming sample stream (Qss) is measured prior to the point

of injection of the turbidity standard. The measurement is in grams of sample per

minute and a gravimetric balance with resolution to the nearest 0.01 grams is used

(equation 1). The measurement can be converted to ml/minute by measuring the

temperature of the sample and then adjusting for its density. It should be noted

that the density adjustment is typically negligible.

Qss = grams of sample dispensed/minute (1)

3. The injection rate of the defined turbidity standard utilizes a freshly prepared

formazin standard. The standard is prepared by gravimetric dilution and the

resultant value can also be confirmed through the measurement on a calibrated

laboratory or portable turbidimeter. The flow of the (Qstd) is calculated as the net

mass of standard delivered over a given period of time: the prepared standard is

first weighed on a gravimetric balance (M0) at the start time of the injection (T0).

After the injection is complete, the standard is re-weighed on the balance (MFinal),

and the time that the injection was also completed (TFinal) is also recorded. The

net mass of the standard injected (MFinal- M0) is divided by the net time of the

injection (TFinal - T0) to deliver the injection rate (Qstd) in g/minute is given by

equation 2.

Qstd = (MFinal- M0) / (TFinal - T0) (2)

Where:

Qstd = Injection rate of the defined turbidity standard;

M0 = the mass of the defined turbidity standard at the beginning of the

injection;

59

MFinal = the mass of the defined turbidity standard at the end of the

injection;

T0 = Time at the beginning of the injection in minutes

TFinal = Time at the end of the injection in minutes

4. The resultant spike of turbidity (NTUSpike) into the sample stream is then

calculated by multiplying the value of the turbidity standard (NTU) by the

injection rate (Qstd) and dividing this by the total flow rate (Qstd + Qss). This is the

theoretical increase in turbidity over the turbidity of the sample stream, expressed

by equation 3.

NTUSpike = NTUstd * Qstd / (Qstd + Qss) (3)

Where:

NTUspike = the spike of turbidity in NTU’s above the turbidity of the

filtered sample stream (i.e. the blank);

NTUstd = the turbidity of the formazin standard that is injected with the

peristaltic pump;

Qstd = the flow rate of the formazin standard into the sample stream;

Qss = the combined flow rate of the sample stream and the formazin

standard.

5. The response of the test instrument (s) to this theoretical increase can be measured

and calculated as a percent recovery. The measured response of the test

instrument minus the turbidity of the baseline prior to injection is first calculated.

This is then divided by the theoretical value of the spike and expressed as a

percentage (multiplied by 100%).

Percent recovery of the spike = 100*(Instrument response to the spike – blank

value of the sample stream) /Theoretical Value of the spike

7.0 Data Collection

Table 3 provides an example of the range of spikes that can be generated for the test

panel. In this table, each horizontal row contains the test parameters and conditions

collected during the test which are used to generate a stable value of turbidity. This

includes entering the overall sample flow at the beginning and end of each run, the

turbidity of the standard to be spiked, the start and end times of the injection of the

60

respective formazin standard, and the start and end mass of the formazin standard that is

spiked (via the peristaltic pump) into the sample stream. The cells that require data to be

entered are shaded in light green. The other cells are calculations (as explained in

equations 1 through 4 above). These equations are entered into an Excel spreadsheet and

will automatically calculate the theoretical turbidity value of each spike. The farthest row

to the right in the table contains the calculated theoretical turbidity value of each spike.

This value is then the basis for the percent recoveries for each spike that is generated in

this study.

Through the measurement of the sample flow at the beginning and end of each run, and

using a gravimetric balance for all mass measurements, the method accurately

compensates for any unforeseen changes in sample flow or injection flow rates over the

duration of the test. In doing so, the method has been demonstrated (internally) to

produce low experimental error (including that of particulate contamination) than

alternative methods of producing large volumes of turbidity standards at very low

turbidity values.

In Table 3, the top and bottom row are the filtered sample stream baselines (used to

determine the blank value). A baseline is run to ensure the turbidity values are stable,

which confirms the performance of the filtration system. In addition, a post spike

baseline is also run. The post spike baseline run typically takes a couple of hours for to

reach its steady state condition after high turbidity values are flowed through the devices.

This is because additional time is needed instruments on the test panel to flush out the

high levels of turbidity from the highest spike.

The second row from the top in Table 3 is the lowest turbidity spike and each progressive

row down the table, turbidity spike is of a higher turbidity value. Spikes are run from the

lowest turbidity value to the highest turbidity value and are arranged within Table 3 from

the top to the bottom of the table in the order of study. By spiking the sample stream

from low to high values the transition time from one turbidity value to the next, higher

turbidity value is fairly rapid. This allows the study to be completed in a relatively short

period of time, (approximately 8 hour’s total).

Table 3 – Sample table that presents the input information to generate the different turbidity spikes for the Spike Injection Method

Spike

Descript

ion

Turbidity

of

Formazin

Spike

standard

(NTU)

Startin

g Mass

(g)

Startin

g Time

(min)

Starting

Sample

Flow

(g/min)

End

Mass

(g)

Change

in Mass

(g)

End

Time

Chan

ge in

Time

(min)

End

Sampl

e Flow

(g/min)

Average

Sample

Flow

(g/min)

Flow

Rate of

Spike

(g/min)

Theoretica

l Turbidity

of Spike

(NTU)

Initial

Baseline (Blank)

0.00 N/A 927

881.4 N/A N/A 1017 60

881.4 881.4 0 0

2.0 NTU

at 2

RPM

2.01 2348.22

855 881.4 2158.4

8 189.74 946 51

881.4 881.4 3.720 0.008

2.0 NTU

at 4 RPM

2.01 2158.4

8 947

881.4 1863 295.48 1031 44

881.4 881.4 6.715 0.015

61

The spike injection method, as proposed, will generate at least two but as many as four

turbidity levels between 0.010 and 0.100; and between two and three turbidity levels

between 0.101 and 1.00 NTU; and between two and three turbidity levels between 1.0

and 10 NTU. The plan will be to produce at least eight different levels of spiked

turbidities, and more (up to a max of 11 spikes) if it is feasible from a time perspective.

The exact turbidity of any of the spike can be adjusted accordingly.

The accuracy of this test plan also involves several tasks that will be accomplished

throughout this testing. These include the following:

• Sample lines shall be equivalent in length, but minimal in distance from the point at

which each line branches to the individual devices under test.

• The formazin standards that are to be spiked into the sample stream shall be measured

on a benchtop turbidimeter, (a Hach® 2100N or equivalent) that has been calibrated

on formazin standards. The bench top device will be used to confirm the value of the

turbidity standard.

• QCS samples will be run at prior to and after the completion of the spiking. QCS

samples will be checked on a benchtop turbidimeter prior to use.

• The volume of the formazin standards will be in the amount which allows for

approximately one hour of injection time. In Table 4, the second to the right column

provides information on the different flow rates for the peristaltic pump that are to be

used in this study.

2.0 NTU

at 8 RPM

2.01 1863 1032

881.4 1230.5

6 632.44 1119 47

881.4 881.4 13.456 0.031

2.0 NTU at 16

RPM

2.01 1230.5

6 1120

881.4 403.58 826.98 1150 30

881.4 881.4 27.566 0.063

16 NTU

at 4

RPM

16.0 1268.44

1151 881.4

859.44 409 1252 61 881.4 881.4

6.705 0.122

16 NTU at 8

RPM

16.0 859.44 1253

881.4 271.73 587.71 1339 46

881.4 881.4 12.776 0.232

134

NTU at

2 RPM

134 1234.77

1346 881.4 1046.4

4 188.33 1435 49

881.4 881.4 3.843 0.584

134

NTU at 4 RPM

134 1046.4

1 1436

881.4 742.7 303.71 1521 45

881.4 881.4 6.749 1.026

134

NTU at

8 RPM

134 740.7 1522

881.4 368.78 371.92 1550 28

881.4 881.4 13.283 2.020

800

NTU at 3 RPM

801 1247.7

4 1551

881.4 1066.5

3 181.21 1624 33

881.4 881.4 5.491 4.991

800 NTU at

6 RPM

801 1066.5

3 1625

881.4 718.29 348.24 1657 32

881.4 881.4 10.883 9.890

Final

Baseline (Blank)

0.000 N/A 1900

881.4 NA N/A 2000 60

881.4 881.4 0.000 0

62

• All formazin standards to be spiked are continuously mixed using a magnetic stirrer

to ensure these solutions remain homogeneous throughout the duration of the test. It

has been confirmed that the magnetic stir bars does not cause measurement error

when weighed on the prescribed balance.

• The data log rates on all instruments will be exactly the same. The proposed time

interval at which data is recorded shall be 15-minutes.

• The clocks on all instruments will be synchronized to the nearest second. This will

ensure the data is consistently time-stamped for all instruments.

• The data will be exported digitally from each instrument using Modbus protocol to a

common computer. This export is in CSV format that is compatible with Microsoft

Excel.

• As a backup, each instrument has a SD card for logging data. If necessary, the data

can be copied from the respective instrument’s SD card into an Excel spreadsheet.

• Microsoft Excel will be the program that all the measurement data will be logged.

All calculations will be performed in Excel.

• After calibration, each instrument will be verified using a separate wet standard. The

value of the verification standard will be at or below 1.0 NTU.

• Prior to each spike, the injection line will be primed with the respective standard.

The injection line is primed up to the valve that allows the standard to be injected into

the sample line. This will minimize the response time to all instruments.

• All instruments will be calibrated on formazin from the same manufacture lot.

Calibration standards will be prepared with Class A glassware and dilution water that

has been filtered through a size exclusion filter with a pore size that is less than 0.2

um.

• The time between spikes will be minimized. This will allow the test and reference

instruments to respond to each increasing step in turbidity, thereby reducing the

stabilization time needed for each turbidity value.

• After the response of each device under test has become stable for a given turbidity

value, the spike will continue for a minimum of 15-minutes. This will allow for the

collection of at least 60 measurements at each turbidity level, (data logged at a rate of

one point every 15 seconds). These measurements will then be used for the statistics

evaluation of each instrument with respect to calculated turbidity.

• For each spike, the 60 measurements will be used to generate the mean, standard

deviation, and relative standard deviation for each instrument.

• For each spike, the calculated mean, based on the 60 measurements will be used in

the percent recovery calculations (accuracy). The standard deviation (SD) will be

used to derive the precision of each instrument on each turbidity level.

• All spike injections will be performed in sequential order from lowest to highest in

the course of a single day.

• All instruments will run a minimum of 8 hours before the commencement of any

portion of the study during which data is collected. This includes calibration. The

intent is to ensure all surfaces that contact the sample are adequately conditioned, (i.e.

wetted).

• At the conclusion of the spike study, the instruments will again be verified using a

wet standard.

63

8.0 Results

Turbidity Spike Results - The results from all the spikes will be provided in tabular

format. Table 4 provides each of the result elements for each spike for the PTV 1000

White Light instrument, Table 5 provides the result elements for the PTV 2000 Red 660-

nm LED, and Table 6 provides the result elements for the PTV 6000 685-nm Laser

instrument. It is expected that these Tables will become part of the study report and

become part the Method Performance section for the respective proposed methods.

Table 4 – Results Table for the Percent Recovery to Turbidity Spikes for the PTV1000 WL LED Turbidimeter

PTV 1000 WL Reading (NTU) Reference Turbidimeter Reading (EPA approved Hach Method

10133)

Spike

#

Baseline

(Blank)

Theoretical

Value

Theoretical Value (blank

Corrected)

Recovery

(%)

Precision

(SD)

Baseline

(Blank)

Theoretical

Value

Theoretical Value (blank

Corrected)

%

Recovery

Precision

(SD) N

1 2 3 4 5 6 7 8


PTV 1000 660 Reading (NTU) Reference Turbidimeter Reading (EPA approved Hach Method

10133)

Spike #

Baseline (Blank)

Theoretical Value

Theoretical

Value (blank

Corrected)

Recovery (%)

Precision (SD)

Baseline (Blank)

Theoretical Value

Theoretical

Value (blank

Corrected)

% Recovery

Precision (SD)

N

1 2 3 4 5 6 7 8


PTV 6000 660 Reading (NTU) Reference Turbidimeter Reading (EPA approved Hach Method

10133)

Spike

#

Baseline

(Blank)

Theoretical

Value

Theoretical

Value (blank Corrected)

Recovery

(%)

Precision

(SD)

Baseline

(Blank)

Theoretical

Value

Theoretical

Value (blank Corrected)

%

Recovery

Precision

(SD) N

1 2

64

3 4 5 6 7 8

Water Plant Comparability Data - The data from each water plant will be plotted for a

period of at least 8 hours. The plot will have time on the x-axis and the turbidity levels

for the test and reference instruments will be plotted on the left y-axis. PTV

1000/2000/6000 instruments will have separate plots versus the reference instrument. An

example of a plot is provided in Figure 4. Based on an 8-hour run of data collection, each

instrument will generate 1920 time stamped data points that can be used for direct

comparability on each water treatment plant sample.

During the water plant run, data that is collected during the process of filtration will be

valid for this study. Any data that is collected during backwash or when the filter is

offline will be excluded.

During the water plant data collection process, it is possible that the drinking water plant

filter will produce water with little to no turbidity excursions over the time of the study.

Under these conditions, surrogate turbidity events may be created using the pump

apparatus that is described in Figure 3. The surrogate turbidity would be to inject kaolin

into the filter effluent to generate turbidity values up to 1 NTU. This will only be used if

no normal filter excursions are observed.

9.0 Conclusions

This test plan is intended to demonstrate measurement comparability between the three

proposed ATP technologies that are presented by Lovibond Inc., and a well-established

EPA approved reference turbidimeter. The study plan has been designed to demonstrate

the comparability under operating conditions of continuous flowing sample streams for

both the direct comparability and for the spike studies.

This test plan is designed to test the three proposed technologies simultaneously in order

to provide to the EPA and to future users of the technologies a comparison of the impact

of different light sources on turbidity measurement. The authors of this test plan feel its

design is comprehensive to the scope and purpose of the application and use of this

technology in the regulatory arena and it exceeds the criteria that has been accepted by

the agency in past approval studies. However, the authors of this test plan welcome any

suggestions and changes that the agency may request.

65

10.0 References

1. SWAN Analytische Instrumente AG, “Continuous Measurement of Turbidity Using a

SWAN AMI Turbiwell Turbidimeter”, (2009)

2. Mitchell, Leck, Ph.D, “Determination of Turbidity by Laser Nephelometry, Mitchell

Method M5271”, (2009).

3. Hach Company, “Hach Method 10133, the Determination of Turbidity by Laser

Nephelometry, (2000).

4. USEPA, “Method 180.1 Determine of Turbidity by Nephelometry”, 1993.

11.0 Figures

Figure 7- The Lovibond PTV 1000 Low Range Turbidimeter

66

Figure 2 - Proposed Schematic of the test panel for the Lovibond Turbidimeter ATP. This includes the WL LED, Red

660-nm LED, and 685-nm Laser versions. The panel also includes the proposed reference turbidimeter.

67

Figure 3 - Schematic for the Spike Injection approach to generate percent recovery data to turbidity spikes for the

Lovibond PTV 1000/2000/6000 Turbidimeter ATP.

68

Figure 4 - Sample plot of the turbidity measurements of a test and reference instrument for a 24-hour period.

69

Figure 5 - Schematic of the PTV 1000/2000/6000 turbidimeter and optional fluidics module.

70

Appendix B.1

Continuous Measurement of Drinking Water

Turbidity Using a Lovibond PTV 1000 White

Light LED Turbidimeter

The Lovibond White Light LED Method

Revision 1.0

December 20, 2016

Tintometer Inc.

6456 Parkland Drive

Sarasota, FL 34243

71

Continuous Measurement of Drinking Water Turbidity Using a

Lovibond PTV 1000 White Light LED Turbidimeter

1. SCOPE AND APPLICATION

1.1 This method is applicable to any colorless drinking water samples with a turbidity

less than 10 Nephelometric Turbidity Units (NTU).

1.2 The applicable range is from 0 to 10 NTU.

1.3 The method meets the requirements for compliance monitoring and reporting as

demanded under the Safe Drinking Water Act (SDWA).

2. SUMMARY OF METHOD

2.1 The method is based upon a comparison of the intensity of a collimated beam of light

that is generated by a white light emitting diode (LED), that is scattered by the sample

under defined conditions with the intensity of the same white light LED scattered by a

standard reference suspension. The higher the intensity of scattered light, the higher

the turbidity. Readings, in NTU, are made in a nephelometer designed according to

specifications given in section 6.2.

2.2 Formazin, prepared under closely defined conditions, is used as a primary standard

suspension to calibrate the instrument. However, other approved primary standards

may be used with this method.

2.2.1 Examples of standards that can be used to calibrate the instrument include

dilutions from commercially available 4000 NTU formazin, stabilized versions of

formazin with preassigned turbidity values such as T-Cal™, and styrene

divinylbenzene suspensions with preassigned values for the specific make and

model of the instrument to be calibrated.

2.3 The method generates a linear response between scattered incident light that is

detected at 90-degrees over the applicable range. The method defines 0.00 NTU as no

light impinging on the 90-degree detector and requires at least one defined standard to

perform a calibration over the applicable range.

3. DEFINITIONS

3.1 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water or other

blank matrices that are treated exactly as a sample including exposure to all

glassware, equipment, solvents, reagents, internal standards, and surrogates that are

72

used with other samples. The LRB is used to determine if method analytes or other

interferences are present in the laboratory environment, the reagents, or the apparatus.

3.2 LINEAR CALIBRATION RANGE (LCR) – The concentration range over which the

instrument response is linear.

3.3 SAFETY DATA SHEET (SDS) – Written information provided by vendors

concerning a chemical/s toxicity, health hazards, physical properties, fire, and

reactivity data including storage, spill, and handling precautions.

3.4 PRIMARY CALIBRATION STANDARD (PCAL) – A suspension prepared from

the primary dilution stock standard suspension. The PCAL suspensions are used to

calibrate the instrument response with respect to analyte concentration.

3.5 QUALITY CONTROL SAMPLE (QCS) - A solution of the method analyte of known

concentrations that is used to fortify an aliquot of LRB matrix. The QCS is obtained

from a source external to the laboratory, and is used to check laboratory performance.

3.6 SECONDARY CALIBRATION STANDARDS (SCAL) – commercially prepared,

stabilized sealed liquid or gel turbidity standards, or other apparatus or mechanism

calibrated against properly prepared and diluted Formazin or styrene divinylbenzene

polymers.

3.7 STOCK STANDARD SUSPENSION (SSS) – A concentrated suspension containing

the analytic solution prepared in the laboratory using assayed reference materials or

purchased from a reputable commercial source. Stock standard suspensions are used

to prepare calibrant suspensions or other needed values of suspensions.

4. INTERFERENCES

4.1 The presence of floating debris and coarse particulate matter within the sample may

settle out of suspension resulting in low turbidity readings.

4.2 Finely divided air bubbles will cause random high spikes in readings.

4.3 The presence of dissolved, light absorbing substances or chemicals in the sample, i.e.

the presence of color, can absorb portions of the incident light spectra, resulting in

low turbidity readings, although this effect is generally not significant for drinking

water.

4.4 Light-absorbing particles in suspension within the sample, such as activated carbon of

significant concentration, can cause low readings.

4.5 Certain dissolved molecules or compounds can impart a fluorescence effect that can

result upon the interaction with shorter wavelengths from the incident light source

73

used in this method. This interference should be considered at turbidities below 0.100

NTU.

4.6 Construction materials of the nephelometric device within the measurement chamber

can result in elevated stray light due to spurious reflections of the incident beam can

cause a false positive bias at the bottom end of the range.

5. SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method has not been fully

established. Each chemical should be regarded as a potential health hazard and

exposure should be as low as reasonably achievable.

5.2 Each laboratory is responsible for maintaining a current awareness file of OSHA

regulations regarding the safe handling of the chemicals specified in this method. A

reference file of Safety Data Sheets (SDS) should be made available to all personnel

involved in the chemical analysis. The preparation of a formal safety plan is also

advisable.

5.3 Hydrazine sulfate (7.2.1) may reasonably be anticipated to be a carcinogen1.

Formazin can contain residual hydrazine sulfate. Proper protection should be

employed.

6. EQUIPMENT

6.1 The installation shall be according to the manufacturer’s instructions.

6.2 The turbidimeter shall consist of a nephelometer with a light source for illuminating

the sample, one or more photo-detectors to measure the amount of scattered light at a

right angle to the incident beam, a correlation means to relate the amount of scattered

light to a known turbidity standard, and a communication means to convey the

turbidity value to the plant operator or other responsible water authority.

6.3 Differences in the physical design of the turbidimeter will cause differences in

measured values for turbidity, even though the same suspension is used for

calibration. To minimize such differences, the following design criteria shall be

observed:

6.3.1 The light source shall be a Light Emitting Diode (LED) emitting white light in the

visible spectrum between 380 and 780 nm. The LED, all optical elements, and

detectors shall have a spectral peak response between 400 nm and 600 nm.

6.3.2 The rays comprising the incident beam shall be parallel with no divergence and

not to exceed 1 degree of convergence within the measurement volume.

74

6.3.3 Non-scattered or non-attenuated light of the incident beam after passing through

the sample shall pass into a light trap.

6.3.4 Distance traversed by incident light and scattered light not to exceed 10 cm.

6.3.5 Detector/Light Receiver shall be centered at 90º ± 1 ½ degrees to the incident

beam.

6.3.6 Scattered light shall be received by the detector/light receiver at a subtended angle

between 20 and 30 degrees from the center-point of the measurement volume.

6.3.7 The detector/light receiver shall have a spectral response that encompasses the

peak spectral output of the incident light source.

6.3.8 A linear-based algorithm shall be used to convert detector signal to NTU in

correlation to a known calibration standard.

6.3.9 The turbidimeter shall be free from significant drift after a short warm-up period.

6.3.10 The sensitivity of the instrument shall detect differences in turbidity of 0.01 NTU

below 1.0 NTU.

6.3.11 The instrument shall be capable of measuring from 0 to 10 NTU turbidity units.

Several ranges may be necessary to obtain both adequate coverage and sufficient

sensitivity for low turbidities.

6.3.12 Instrument shall incorporate a sample deaerator for the removal of entrained air

from the sample stream.

6.4 A nephelometric device that meets these specifications is a Lovibond PTV 1000

turbidimeter.

7. REAGENTS AND STANDARDS

7.1 Reagent water, turbidity-free: Pass deionized distilled water through a 0.2-µm or

smaller pore-size membrane filter if necessary. Water produced by reverse osmosis is

acceptable. Water should have a turbidity that is ≤0.030 NTU. This value should be

considered when preparing standards.

7.2 Stock standard suspension (Formazin) 4000 NTU

7.2.1 Dissolve 5.00 g hydrazine sulfate (CASRN 10034-93-2) into approximately

400 mL of reagent water contained in a cleaned 1-L Class A volumetric flask.

75

7.2.2 Dissolve 50.00 g hexamethylenetetramine (CASRN 100-97-0) in approximately

300 mL of reagent water contained in a 500-mL volumetric flask.

7.2.3 Quantitatively transfer the hexamethylenetetramine solution (7.2.2) into the 1-L

flask that contains the dissolved hydrazine sulfate solution (7.2.1).

7.2.4 Dilute the 1-L flask (7.2.3) to volume with reagent water.

7.2.5 Stopper and mix by inversion for 10 minutes.

7.2.6 Allow to stand 24 hours at 25 ± 2 °C. During this time, the formazin polymer will

develop. The turbidity of this standard is 4000 NTU.

7.2.7 Store this solution in the dark and away from a source of heat. Bring the solution

to room temperature and thoroughly mix before preparing dilutions (7.3).

7.3 Primary calibration standards: Using a pipette with accuracy to 1 percent or better,

first mix and then dilute 25.0 mL of stock standard suspension (7.2) to 0.10 L with

reagent water. The turbidity of this suspension is defined as 1000 NTU. For other

turbidity values, mix and dilute portions of this suspension as required using clean

Class A glassware.

7.3.1 A new stock standard suspension (7.2) should be prepared each quarter. Primary

calibration standards (7.3) should be prepared daily by dilution of the stock

standard suspension.

7.4 Formazin in commercially prepared, certified, concentrated stock standard suspension

(SSS) may be diluted and used as required. Dilute turbidity standards should be

prepared daily.

7.5 Stabilized formazin suspensions or styrene divinylbenzene (SDVB) polymers are

commercially prepared, certified, and ready to use dilutions. Manufacturer’s

instructions should be followed for choosing the appropriate standard values for the

instrument.

7.6 Secondary standards may be acceptable as a calibration check, but must be monitored

on a routine basis for deterioration and replaced as required.

8. SAMPLE COLLECTION AND INSTRUMENT SETUP

8.1 Online instrumentation does not require sample cooling, preservation or storage.

8.2 Install and set up the instrument according to the manufacturer’s instructions.

8.3 Determination of the sample water offset.

76

8.3.1 This step is optional and can be performed if the measured sample measures high

when compared to a EPA approved reference measurement. This can occur when

fluorescence effects are suspected (4.5).

8.3.2 This step should be applied when the expected turbidity is below 0.100 NTU.

8.3.3 Procedure

8.3.3.1 Collect approximately 25 mL of sample. Record the value of the turbidity

on the on-line instrument.

8.3.3.2 Filter the sample through 0.2-µm filter directly into a clean sample vial.

Rinse the vial at least two times with the filtered sample prior to filing

with the filtered aliquot for analysis.

8.3.3.3 Carefully prepare the sample aliquot for measurement in a calibrated

reference benchtop or portable instrument that meets the specifications

outlined in the method or any EPA approved turbidity method.

8.3.3.4 Record the turbidity value on the reference instrument.

8.3.3.5 Enter this value into the process turbidimeter as the blank value for the

sample. The maximum allowable value that should be entered into the on-

line instrument is 0.05 NTU.

8.3.4 The offset does not impact the calibration gain.

9. QUALITY CONTROL

9.1 Each laboratory using this method is required to operate a formal quality control (QC)

program. The minimum requirements of this program consist of an initial

demonstration of the process turbidimeter system’s capability and analysis of

laboratory reagent blanks and other solutions as a continuing check on performance.

The laboratory is required to maintain performance records that define the quality of

data generated.

9.2 Initial demonstration of performance

9.2.1 The initial demonstration of performance is used to characterize instrument

performance as determined by the LCR and QCS analyses.

9.2.2 Linear Calibration Range (LCR) – The LCR must be determined initially and

verified whenever a significant change in instrument response is observed or

expected. The initial demonstration of linearity must use sufficient standards to

insure that the resulting curve is linear. The verification of linearity must use a

77

minimum of a blank and three standards. For example, the standards could be

0.30 NTU, 5.0 NTU and 10.0 NTU. If any verification data exceeds the initial

values by ± 10% or exceeds the stated specifications of the turbidity standard,

whichever is greater, linearity must be reestablished. If any portion of the range is

shown to be nonlinear, sufficient standards must be used to clearly define the

nonlinear portion. The selection of standards should at least cover the range of

turbidity values that are expected from samples.

9.2.3 Quality Control Sample (QCS) – When beginning the use of this method, on a

quarterly basis or as required to meet data-quality needs, verify the calibration

standards and acceptable instrument performance with the preparation and

analysis of a QCS. If the determined concentrations are not within ± 10% or ±

0.040 NTU of the stated QCS values, performance of the determinative step of the

method is unacceptable. The source of the problem must be identified and

corrected before continuing with on-going analyses.

9.3 Accuracy and precision should be checked on a routine basis to monitor the overall

performance of the instrument. A series of reagent blanks and check standards should

be run to validate the quality of sample data. These checks should occur at a

frequency that is required for regulatory compliance.

9.3.1 A QCS sample as described in 9.2.3 must be run at least on a quarterly interval.

The instrument must be checked to insure it has been cleaned and maintained

according to the manufacturers recommendations prior to running the QCS.

9.3.2 Solid standards are an option and can only be used for verification purposes. The

instrument should be checked to insure it has been cleaned and maintained

according to the manufacturers recommendations prior to running a solid

verification standard.

10. CALIBRATION AND STANDARDIZATION

10.1 Turbidity Calibration: The manufacturer’s operating instructions should be followed

for calibration. Perform any cleaning and maintenance prior to calibration as per

manufacturer’s instructions. The turbidimeter measurement chamber should be rinsed

with at least 1 L of water that has been filtered through a 0.45-um filter or smaller

prior to calibration. Calibration should be performed under the same ambient

conditions as sample measurement.

10.2 Measure standards on the turbidimeter covering the range of interest. If the

instrument is already calibrated in standard turbidity units, this procedure will check

the accuracy of the calibration scales.

78

10.3 At least one standard should be run in each instrument range to be used. Some

instruments permit adjustments of sensitivity so that scale values will correspond to

turbidities.

10.4 Solid standards can only be used for verification purposes. If used, they must be

protected from surface scratches which may cause potential changes.

10.5 If a pre-calibrated scale is not supplied, calibration curves should be prepared for each

range of the instrument. Calibration must be performed under identical optical

conditions as operational conditions.

11. PROCEDURE

11.1 A sample from the treatment process is taken and flows through the turbidimeter for

measurement. It is then drained or recycled back into the process after the

measurement has been taken.

11.2 The sample flow rate shall be in accordance with the instrument specifications. The

sample flow to the instrument shall be constant without variations due to pressure

changes or surges. Installation of a flow control device such as a rotameter in the

sample line can eliminate fluctuations of the flow rate.

11.3 The range of the sample temperature should be in accordance with the instrument

specifications. The sample temperature within this range should be constant.

12. DATA ANALYSIS AND CALCULATIONS

12.1 Report results as follows:

NTU Record to Nearest

0.01 - 1.0 0.01

1 - 10 0.025

13. METHOD PERFORMANCE

13.1 Prior to testing, all instruments were calibrated according to manufacturer’s

instructions. This was followed by running a QCS sample to verify the determinative

step for each turbidimeter was within the specified criteria.

13.2 On-line accuracy and precision testing with turbidity spikes – The Lovibond White

LED Method was conducted in a qualified laboratory. Since the test and reference

instruments require continuous sample flow, a pump injection system was used to

introduce spikes of turbidity. Each turbidity spike was of constant and stable turbidity

79

that was generated by the addition of a defined formazin standard pumped into the

sample stream at a constant flow rate. The sample itself passed through a 0.02-µm

pore size filter prior to being spiked. After the filtered sample was spiked with the

formazin, it traveled through a mixing coil that was then split into parallel feed lines

that led to the test and reference instruments. This provided a continuous parallel feed

of sample with a stable turbidity to both the test and reference instrument.

13.2.1 Changing the injection rate of the formazin standard that was spiked into the

filtered sample or changing the actual value of the formazin standard that was

spiked into the filtered sample yielded various stable turbidity values that were

continuously delivered to the test and reference instruments.

13.2.2 The injection rate of the turbidity standard was calculated in grams per minute

and the flow of the filtered sample was measured in grams per minute. This

allowed for the theoretical calculation of each turbidity spike. The instrument

response was calculated as a percent recovery of this spike. This data is presented

in Table 1 (17.1).

13.2.3 The sequence of spikes started with a turbidity free baseline and progressed with

increasing turbidity up to the highest turbidity level.

13.2.4 The pre-filtered water supply was a blend of hot and cold tap water that is

supplied by the city of Fort Collins. The source water was from mountain snow

runoff that was treated with conventional techniques and filtered using dual media

filtration.

13.2.5 Results were used for the initial demonstration of linearity of the measurement

system.

13.3 On-Line testing at public water utilities – The PTV 1000 turbidimeter (Lovibond WL

LED Method) was tested at two public water utilities. One utility was a surface

source water treatment plant that required an additional softening step. The second

plant treated a surface source water that went through an integrated micro-filtration

membrane as the filtration step. Both utilities are members of the Partnership for Safe

Water. The PTV 1000 turbidimeter and a reference turbidimeter that was compliant

with the USEPA laser nephelometry method was connected to the same source water

line for analysis. Both turbidimeters were operated for 24 hours, collecting data once

per 15 seconds. The deviation between the two instruments was 0.019 and 0.045 NTU

for these two plants respectively. Response time to changes in turbidity differed

slightly and was a function of flow rates, but the magnitude of response was

consistent.

13.4 The instruments were calibrated according to manufacturer’s instructions. After

calibration, a QCS was run on each instrument to verify that the determinative step

for each turbidimeter was within the specified criteria.

80

13.5 Accuracy of the Lovibond WL LED Method – Accuracy (bias) was presented as

percent recoveries relative to the theoretical values for the turbidity spikes compared

to results from the reference Hach Method 101333. Refer to Table 1 in section 17 for

a summary of all spike recovery and precision data.

13.5.1 Percent Recoveries for spikes in the 0 to 0.10 NTU range:

The average percent recoveries of turbidity for turbidity spikes in the 0.014 to

0.10 NTU range were:

Lovibond WL LED Method: 106.0%

Turbidimeter reference method 10133: 101.5%.

13.5.2 Percent Recoveries for spikes in the 0.10 to 1.0 NTU range

The average percent recoveries of turbidity for the spikes in the 0.10 to 1.0 NTU

range were:




The average percent recoveries of turbidity for turbidity spikes from the 1.0 to 10

NTU range were:



13.6 Precision Lovibond WL LED Method – Precision was presented here as the standard

deviation for each of the turbidity spikes compared to results from the reference Hach

Method 101333. Refer to Table 1 in section 17 for a summary of all spike recovery

and precision data.

13.6.1 Precision for spikes in the 0 to 0.10 NTU range

The standard deviation for the turbidity for turbidity in the 0.014 to 0.10 NTU

range were:

Lovibond WL LED Method: 0.0006 NTU

Turbidimeter reference method 10133: 0.0002 NTU.

13.6.2 Precision for spikes in the 0.10 to 1.0 NTU range

The standard deviation for the turbidity spikes in the 0.10 to 1.0 NTU range were:




The standard deviation for the turbidity spikes from the 1.0 to 10 NTU range

were:



81

14. POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the

quantity or toxicity of waste as the point of generation. Numerous opportunities for

pollution prevention exist in laboratory operation. The EPA has established a

preferred hierarchy of environmental management techniques that places pollution

prevention as the management option of first choice. Whenever feasible, laboratory

personnel should use pollution-prevention techniques to address their waste

generation. When wastes cannot be feasibly reduced at the source, the Agency

recommends recycling as the next best option.

14.2 The quantity of chemicals purchased should be based on expected usage during its

shelf life and disposal cost of unused material. Actual reagent preparation volumes

should reflect anticipated usage and reagent stability.

15. WASTE MANAGEMENT

15.1 The U.S. Environmental Protection Agency requires that laboratory waste

management practices be conducted consistent with all applicable rules and

regulations. Excess reagents, samples and method process wastes should be

characterized and disposed of in an acceptable manner. The Agency urges

laboratories to protect air, water, and land by minimizing and controlling all releases

from hoods and bench operations; complying with the letter and spirit of any waste

discharge permit and regulations; and by complying with all solid hazardous waste

regulations, particularly the hazardous waste identification rules and land disposal

restrictions.

16. REFERENCES

1. Fourth Annual Report on Carcinogens (NTP85-002 1985), p115

2. USEPA. “Method 180.1 Determination of Turbidity by Nephelometry,” Revision 2.0,

(1993).

3. Hach Company, “Hach Method 10133, “Determination of Turbidity by Laser

Nephelometry”, (2000).

17. TABLES AND VALIDATION DATA

17.1 Summarized precision and bias (percent recovery) data in tabular form (Table 1).

82

Table 1 – Results Table for the Percent Recovery and Precision with Respect to Turbidity Spikes for the PTV1000 WL LED

Turbidimeter

PTV 1000 WL Reading

Reference Turbidimeter Reading (EPA approved

Method 10133)

Spike #

Baselin

e

(Blank)

Theoretic

al Value of Spike

in NTU

Response (blank

Correcte

d) in NTU

Recovery (%)

Precision (SD)

Baselin

e

(Blank)

Theoretic

al Value of Spike

in NTU

Response (blank

Correcte

d) in NTU

Recovery (%)

Precision (SD)

N (both

Test and Referenc

e)

1 0.024 0.014 0.016 110.8 0.0009

0.010 0.014 0.014 102.3 0.0001 60

2 0.024 0.028 0.030 104.9 0.0002

0.010 0.028 0.029 102.6 0.0002 60

3 0.024 0.060 0.062 102.3 0.0007

0.010 0.060 0.060 99.4 0.0002 60

4 0.024 0.110 0.114 103.4 0.0014

0.010 0.110 0.112 102.0 0.0005 60

5 0.024 0.225 0.235 104.5 0.0021

0.010 0.225 0.232 103.3 0.0014 60

6 0.024 0.554 0.564 101.7 0.0051

0.010 0.554 0.559 100.8 0.0036 60

7 0.024 0.921 0.940 102.1 0.0094

0.010 0.921 0.930 101.0 0.0079 60

8 0.024 1.895 1.929 101.8 0.0081

0.010 1.895 1.928 101.8 0.0069 60

9 0.024 3.568 3.444 96.5 0.0267

0.010 3.568 3.463 97.1 0.0077 60

10 0.024 9.376 9.437 100.6 0.0313

0.010 9.376 9.472 101.0 0.0277 60

83

Appendix B.2


Turbidity Using a Lovibond PTV 2000 660-nm

LED Turbidimeter

The Lovibond 660-nm LED Method

Revision 1.0

December 20, 2016

Tintometer Inc.

6456 Parkland Drive

Sarasota, FL 34243

84


Lovibond PTV 2000 Red LED Turbidimeter


1.1 This method is applicable to any colorless drinking water samples with a turbidity

less than 10 Nephelometric Turbidity Units (NTU).





2.1 The method is based upon a comparison of the intensity of a collimated beam of light

that is generated by a 660-nm LED, that is scattered by the sample under defined

conditions with the intensity of the same 660-nm light LED scattered by a standard

reference suspension. The higher the intensity of scattered light, the higher the

turbidity. Readings, in NTU, are made in a nephelometer designed according to

specifications given in section 6.2.

2.2 Formazin, prepared under closely defined conditions, is used as a primary standard

suspension to calibrate the instrument. However, other approved primary standards

may be used with this method.


dilutions from commercially available 4000 NTU formazin, stabilized versions of

formazin with preassigned turbidity values such as T-Cal™, and styrene

divinylbenzene suspensions with preassigned values for the specific make and

model of the instrument to be calibrated.


detected at 90-degrees over the applicable range. The method defines 0.00 NTU as no

light impinging on the 90-degree detector and requires at least one defined standard to

perform a calibration over the applicable range.

3. DEFINITIONS

3.1 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water or other

blank matrices that are treated exactly as a sample including exposure to all

glassware, equipment, solvents, reagents, internal standards, and surrogates that are

85

used with other samples. The LRB is used to determine if method analytes or other

interferences are present in the laboratory environment, the reagents, or the apparatus.

3.2 LINEAR CALIBRATION RANGE (LCR) – The concentration range over which the

instrument response is linear.




3.4 PRIMARY CALIBRATION STANDARD (PCAL) – A suspension prepared from

the primary dilution stock standard suspension. The PCAL suspensions are used to

calibrate the instrument response with respect to analyte concentration.

3.5 QUALITY CONTROL SAMPLE (QCS) - A solution of the method analyte of known

concentrations that is used to fortify an aliquot of LRB matrix. The QCS is obtained

from a source external to the laboratory, and is used to check laboratory performance.

3.6 SECONDARY CALIBRATION STANDARDS (SCAL) – commercially prepared,

stabilized sealed liquid or gel turbidity standards, or other apparatus or mechanism

calibrated against properly prepared and diluted Formazin or styrene divinylbenzene

polymers.

3.7 STOCK STANDARD SUSPENSION (SSS) – A concentrated suspension containing

the analytic solution prepared in the laboratory using assayed reference materials or

purchased from a reputable commercial source. Stock standard suspensions are used

to prepare calibrant suspensions or other needed values of suspensions.

4. INTERFERENCES

4.1 The presence of floating debris and coarse particulate matter within the sample may

settle out of suspension resulting in low turbidity readings.


4.3 The presence of dissolved, light absorbing substances or chemicals in the sample, i.e.

the presence of color, can absorb portions of the incident light spectra, resulting in

low turbidity readings, although this effect is generally not significant for drinking

water.

4.4 Light-absorbing particles in suspension within the sample, such as activated carbon of

significant concentration, can cause low readings.

86

4.5 Construction materials of the nephelometric device within the measurement chamber

can result in elevated stray light due to spurious reflections of the incident beam can

cause a false positive bias at the bottom end of the range.

5. SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method has not been fully

established. Each chemical should be regarded as a potential health hazard and

exposure should be as low as reasonably achievable.

5.2 Each laboratory is responsible for maintaining a current awareness file of OSHA

regulations regarding the safe handling of the chemicals specified in this method. A

reference file of Safety Data Sheets (SDS) should be made available to all personnel

involved in the chemical analysis. The preparation of a formal safety plan is also

advisable.

5.3 Hydrazine sulfate (7.2.1) may reasonably be anticipated to be a carcinogen1.


employed.

6. EQUIPMENT


6.2 The turbidimeter shall consist of a nephelometer with a light source for illuminating

the sample, one or more photo-detectors to measure the amount of scattered light at a

right angle to the incident beam, a correlation means to relate the amount of scattered

light to a known turbidity standard, and a communication means to convey the

turbidity value to the plant operator or other responsible water authority.




observed:

6.3.1 The light source shall be a light emitting diode (LED) with a peak emitting

wavelength between 650 and 670 nm. The optical system, including the emitter,

all optical elements and detector(s), shall have a spectral peak response between

600 nm and 700 nm.

6.3.2 The rays comprising the incident beam shall be parallel with no divergence and

not to exceed 1 degree of convergence within the measurement volume.

87

6.3.3 Non-scattered or non-attenuated light of the incident beam after passing through

the sample shall pass into a light trap.


6.3.5 Detector/Light Receiver shall be centered at 90º ± 1 ½ degrees to the incident

beam.

6.3.6 Scattered light shall be received by the detector/light receiver at a subtended angle

between 20 and 30 degrees from the center-point of the measurement volume.

6.3.7 The detector/light receiver shall have a spectral response that encompasses the

peak spectral output of the incident light source.



6.3.9 The turbidimeter shall be free from significant drift after a short warm-up period.

6.3.10 The sensitivity of the instrument shall detect differences in turbidity of 0.01 NTU.

6.3.11 The instrument shall be capable of measuring from 0 to 10 NTU turbidity units.

Several ranges may be necessary to obtain both adequate coverage and sufficient

sensitivity for low turbidities.

6.3.12 Instrument shall incorporate a sample deaerator for the removal of entrained air

from the sample stream.


turbidimeter.


7.1 Reagent water, turbidity-free: Pass deionized distilled water through a 0.2-µm or

smaller pore-size membrane filter if necessary. Water produced by reverse osmosis is

acceptable. Water should have a turbidity that is ≤0.030 NTU. This value should be

considered when preparing standards.


7.2.1 Dissolve 5.00 g hydrazine sulfate (CASRN 10034-93-2) into approximately 400

mL of reagent water contained in a cleaned 1-L Class A volumetric flask.

88

7.2.2 Dissolve 50.00 g hexamethylenetetramine (CASRN 100-97-0) in approximately

300 mL of reagent water contained in a 500-mL volumetric flask.

7.2.3 Quantitatively transfer the hexamethylenetetramine solution (7.2.2) into the 1-L

flask that contains the dissolved hydrazine sulfate solution (7.2.1).



7.2.6 Allow to stand 24 hours at 25 ± 2 °C. During this time, the formazin polymer will

develop. The turbidity of this standard is 4000 NTU.

7.2.7 Store this solution in the dark and away from a source of heat. Bring the solution

to room temperature and thoroughly mix before preparing dilutions (7.3)

7.3 Primary calibration standards: Using pipetts with an accuracy of 1 percent or better,

first mix and then dilute 25.0 mL of stock standard suspension (7.2) to 0.10 L with

reagent water. The turbidity of this suspension is defined as 1000 NTU. For other

turbidity values, mix and dilute portions of this suspension as required using clean

Class A glassware.

7.3.1 A new stock standard suspension (7.2) should be prepared each quarter. Primary

calibration standards (7.3) should be prepared daily by dilution of the stock

standard suspension.

7.4 Formazin in commercially prepared, certified, concentrated stock standard suspension

(SSS) may be diluted and used as required. Dilute turbidity standards should be

prepared daily.

7.5 Stabilized formazin suspensions or styrene divinylbenzene (SDVB) polymers are

commercially prepared, certified, and ready to use dilutions. Manufacturer’s

instructions should be followed for choosing the appropriate standard values for the

instrument.

7.6 Secondary standards may be acceptable as a calibration check, but must be monitored

on a routine basis for deterioration and replaced as required.


8.1 Online instrumentation does not require sample cooling, preservation or storage.


89

9. QUALITY CONTROL

9.1 Each laboratory using this method is required to operate a formal quality control (QC)

program. The minimum requirements of this program consist of an initial


laboratory reagent blanks and other solutions as a continuing check on performance.

The laboratory is required to maintain performance records that define the quality of

data generated.




9.2.2 Linear Calibration Range (LCR) – The LCR must be determined initially and

verified whenever a significant change in instrument response is observed or

expected. The initial demonstration of linearity must use sufficient standards to

insure that the resulting curve is linear. The verification of linearity must use a

minimum of a blank and three standards. For example, the standards could be

0.30, 5.0 and 10.0 NTU. If any verification data exceeds the initial values by ±

10% or exceeds the stated specifications of the turbidity standard, whichever is

greater, linearity must be reestablished. If any portion of the range is shown to be

nonlinear, sufficient standards must be used to clearly define the nonlinear

portion. The selection of standards should at least cover the range of turbidity

values that are expected from samples.

9.2.3 Quality Control Sample (QCS) – When beginning the use of this method, on a

quarterly basis or as required to meet data-quality needs, verify the calibration

standards and acceptable instrument performance with the preparation and

analysis of a QCS. If the determined concentrations are not within ± 10 % or ±

0.030 NTU of the stated QCS values, performance of the determinative step of the

method is unacceptable. The source of the problem must be identified and

corrected before continuing with on-going analyses.

9.3 Accuracy and precision should be checked on a routine basis to monitor the overall

performance of the instrument. A series of reagent blanks and check standards should

be run to validate the quality of sample data. These checks should occur at a

frequency that is required for regulatory compliance.

9.3.1 A QCS sample as described in 9.2.3 must be run at least on a quarterly interval.

The instrument must be checked to insure it has been cleaned and maintained

according to the manufacturers recommendations prior to running the QCS.

9.3.2 Solid standards are an option and can only be used for verification purposes. The

instrument should be checked to insure it has been cleaned and maintained

90

according to the manufacturers recommendations prior to running a solid

verification standard.


10.1 Turbidity Calibration: The manufacturer’s operating instructions should be followed

for calibration. Perform any cleaning and maintenance prior to calibration as per

manufacturer’s instructions. The turbidimeter measurement chamber should be rinsed

with at least 1-liter of water that has been filtered through a 0.45-um filter or smaller

prior to calibration. Calibration should be performed under the same ambient

conditions as sample measurement.


instrument is already calibrated in standard turbidity units, this procedure will check

the accuracy of the calibration scales.


instruments permit adjustments of sensitivity so that scale values will correspond to

turbidities.



10.5 If a pre-calibrated scale is not supplied, calibration curves should be prepared for each

range of the instrument. Calibration must be performed under identical optical

conditions as operational conditions.

11. PROCEDURE

11.1 A sample from the treatment process is taken and flows through the turbidimeter for

measurement. It is then drained or recycled back into the process after the

measurement has been taken.

11.2 The sample flow rate shall be in accordance with the instrument specifications. The

sample flow to the instrument shall be constant without variations due to pressure

changes or surges. Installation of a flow control device such as a rotameter in the

sample line can eliminate fluctuations of the flow rate.\

11.3 The range of the sample temperature should be in accordance with the instrument

specifications. The sample temperature within this range should be constant.


91



0.01 - 1.0 0.01

1 - 10 0.1



instructions. This was followed by running a QCS sample to verify the determinative


13.2 On-line accuracy and precision testing with turbidity spikes. The Lovibond 660-nm

LED Method was conducted in a qualified laboratory. Since the test and reference

instruments require continuous sample flow, a pump injection system was used to

introduce spikes of turbidity. Each turbidity spike was of constant and stable turbidity

that was generated by the addition of a defined formazin standard pumped into the

sample stream at a constant flow rate. The sample itself passed through a 0.02-µm

pore size filter prior to being spiked. After the filtered sample was spiked with the

formazin, it traveled through a mixing coil that was then split into parallel feed lines

that led to the test and reference instruments. This provided a continuous parallel feed

of sample with a stable turbidity to both the test and reference instrument.


filtered sample or changing the actual value of the formazin standard that was

spiked into the filtered sample yielded various stable turbidity values that were

continuously delivered to the test and reference instruments.

13.2.2 The injection rate of the turbidity standard was calculated in grams per minute


allowed for the theoretical calculation of each turbidity spike. The instrument

response was calculated as a percent recovery of this spike. This data is presented

in Table 1 (17.1)

13.2.3 The sequence of spikes started with a turbidity free baseline and progressed with

increasing turbidity up to the highest turbidity level.


supplied by the city of Fort Collins. The source water was from mountain snow

runoff that was treated with conventional techniques and filtered using dual media

filtration.

13.2.5 Results were used for the initial demonstration of linearity of the measurement

system.

92

13.3 On-Line testing at public water utilities – The PTV 2000 660-nm LED Method was

tested at two public water utilities. One utility was a surface source water treatment

plant that required an additional softening step. The second plant treated a surface

source water that went through an integrated micro-filtration membrane as the

filtration step. Both utilities are members of the Partnership for Safe Water. The

Lovibond 660-nm LED turbidimeter and a reference turbidimeter that was compliant

with the USEPA laser nephelometry method was connected to the same source water

line for analysis. Both turbidimeters were operated for 24 hours, collecting data once

per 15 seconds. The deviation between the two instruments was 0.002 and 0.009 NTU

for the two plants respectively. Response time to changes in turbidity differed slightly

and was a function of flow rates, but the magnitude of response was consistent.


calibration a QCS was run on each instrument to verify that the determinative step for

each turbidimeter was within the specified criteria.

13.5 Accuracy of the Lovibond 660-nm LED Method – Accuracy (bias) was presented as

percent recoveries relative to theoretical values for the turbidity spikes compared to

results from the reference Hach Method 101333. Refer to Table 1 in Section 17 for a

summary of all spike recovery and precision data.


The average percent recoveries of turbidity for turbidity spikes in the 0.014 to


Lovibond 660-nm LED Method: 103.5 %

Turbidimeter reference method 10133: 101.5 %.


The average percent recoveries of turbidity for the spikes in the 0.10 to 1.0 NTU

range were:




The average percent recoveries of turbidity for turbidity spikes from the 1.0 to 10

NTU range were:


Turbidimeter reference method 10133: 99.9 %.

13.6 Precision Lovibond 660-nm LED Method Precision was presented here as the

standard deviation for each of the turbidity spikes compared to results from the

reference Hach Method 101333. Refer to Table 1 in Section 17 for a summary of all

spike recovery and precision data.


93

The standard deviation for the turbidity for turbidity spikes in the 0.014 to 0.10

NTU range were:

Lovibond 660-nm LED Method: 0.0003 NTU



The standard deviation for the turbidity spikes in the 0.10 to 1.0 NTU range were:




The standard deviation for the turbidity spikes from the 1.0 to 10 NTU range

were:





quantity or toxicity of waste as the point of generation. Numerous opportunities for

pollution prevention exist in laboratory operation. The EPA has established a

preferred hierarchy of environmental management techniques that places pollution

prevention as the management option of first choice. Whenever feasible, laboratory

personnel should use pollution-prevention techniques to address their waste

generation. When wastes cannot be feasibly reduced at the source, the Agency

recommends recycling as the next best option.

14.2 The quantity of chemicals purchased should be based on expected usage during its

shelf life and disposal cost of unused material. Actual reagent preparation volumes

should reflect anticipated usage and reagent stability.






laboratories to protect air, water, and land by minimizing and controlling all releases

from hoods and bench operations; complying with the letter and spirit of any waste

discharge permit and regulations; and by complying with all solid hazardous waste

regulations, particularly the hazardous waste identification rules and land disposal

restrictions.

94

16. REFERENCES

1. Fourth Annual Report on Carcinogens (NTP85-002 1985), p115

2. USEPA. “Method 180.1 Determination of Turbidity by Nephelometry,” Revision 2.0,

(1993).




17.1 Summarized precision and bias (percent recovery) data in tabular form (Table 1).


PTV 2000 660-nm LED Reading

Reference Turbidimeter Reading (EPA approved

Method 10133)

Spike #

Baselin

e (Blank)

in NTU

Theoretic

al Value of Spike

in NTU

Response

(blank Correcte

d)

Recover

y

(%)

Precision (SD)

Baselin

e (Blank)

in NTU

Theoretic

al Value of Spike

in NTU

Response

(blank Correcte

d)

Recovery (%)

Precision (SD)

N (both

Test and Referenc

e)

1 0.013 0.014 0.015 104.5 0.0002

0.010 0.014 0.014 102.3 0.0001 60

2 0.013 0.028 0.029 104.3 0.0003

0.010 0.028 0.029 102.6 0.0002 60

3 0.013 0.060 0.061 101.5 0.0003

0.010 0.060 0.060 99.4 0.0002 60

4 0.013 0.110 0.112 101.4 0.0012

0.010 0.110 0.112 102.0 0.0005 60

5 0.013 0.225 0.232 103.3 0.0020

0.010 0.225 0.232 103.3 0.0014 60

6 0.013 0.554 0.553 99.7 0.0040

0.010 0.554 0.559 100.8 0.0036 60

7 0.013 0.921 0.918 99.7 0.0088

0.010 0.921 0.930 101.0 0.0079 60

8 0.013 1.895 1.858 98.1 0.0077

0.010 1.895 1.928 101.8 0.0069 60

9 0.013 3.568 3.344 93.7 0.0140

0.010 3.568 3.463 97.1 0.0077 60

10 0.013 9.376 9.304 99.2 0.0251

0.010 9.376 9.472 101.0 0.0277 60

95

Appendix B.3


Turbidity Using a Lovibond PTV 6000 Laser

Turbidimeter

The Lovibond 6000 Laser Method

Revision 1.0

December 20, 2016

Tintometer Inc.

6456 Parkland Drive

Sarasota, FL 34243

96


Lovibond PTV 6000 Laser Turbidimeter


1.1 This method is applicable to any colorless drinking water samples with a

turbidity less than 10 Nephelometric Turbidity Units (NTU).





2.1 The method is based upon a comparison of the intensity of a collimated beam of

light that is generated by a 685-nm laser diode, that is scattered by the sample

under defined conditions with the intensity of the same laser diode light

scattered by a standard reference suspension. The higher the intensity of

scattered light, the higher the turbidity. Readings, in NTU, are made in a

nephelometer designed according to specifications given in section 6.2.

2.2 Formazin, prepared under closely defined conditions, is used as a primary

standard suspension to calibrate the instrument. However, other approved

primary standards may be used with this method.


freshly prepared dilutions from commercially available 4000 NTU

formazin, stabilized versions of formazin with preassigned turbidity values

such as T-Cal™, and styrene divinylbenzene suspensions with preassigned

values for the specific make and model of the instrument to be calibrated.


detected at 90-degrees over the applicable range. The method defines 0.00 NTU

as no light impinging on the 90-degree detector and requires at least one defined

standard to perform a calibration over the applicable range.

3. DEFINITIONS

3.1 LABORATORY REAGENT BLANK (LRB) – An aliquot of reagent water or

other blank matrices that are treated exactly as a sample including exposure to

97

all glassware, equipment, solvents, reagents, internal standards, and surrogates

that are used with other samples. The LRB is used to determine if method

analytes or other interferences are present in the laboratory environment, the

reagents, or the apparatus.

3.2 LINEAR CALIBRATION RANGE (LCR) – The concentration range over

which the instrument response is linear.




3.4 PRIMARY CALIBRATION STANDARD (PCAL) – A suspension prepared

from the primary dilution stock standard suspension. The PCAL suspensions

are used to calibrate the instrument response with respect to analyte

concentration.

3.5 QUALITY CONTROL SAMPLE (QCS) - A solution of the method analyte of

known concentrations that is used to fortify an aliquot of LRB matrix. The QCS

is obtained from a source external to the laboratory, and is used to check

laboratory performance.

3.6 SECONDARY CALIBRATION STANDARDS (SCAL) – commercially

prepared, stabilized sealed liquid or gel turbidity standards, or other apparatus

or mechanism calibrated against properly prepared and diluted Formazin or

styrene divinylbenzene polymers.

3.7 STOCK STANDARD SUSPENSION (SSS) – A concentrated suspension

containing the analytic solution prepared in the laboratory using assayed

reference materials or purchased from a reputable commercial source. Stock

standard suspensions are used to prepare calibrant suspensions or other needed

values of suspensions.

4. INTERFERENCES

4.1 The presence of floating debris and coarse particulate matter within the sample

may settle out of suspension resulting in low turbidity readings.


4.3 The presence of dissolved, light absorbing substances or chemicals in the

sample, i.e. the presence of color, can absorb portions of the incident light

spectra, resulting in low turbidity readings, although this effect is generally not

significant for drinking water.

98

4.4 Light-absorbing particles in suspension within the sample, such as activated

carbon of significant concentration, can cause low readings.

4.5 Construction materials of the nephelometric device within the measurement

chamber can result in elevated stray light due to spurious reflections of the

incident beam can cause a false positive bias at the bottom end of the range.

5. SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method has not been

fully established. Each chemical should be regarded as a potential health hazard

and exposure should be as low as reasonably achievable.

5.2 Each laboratory is responsible for maintaining a current awareness file of

OSHA regulations regarding the safe handling of the chemicals specified in this

method. A reference file of Safety Data Sheets (SDS) should be made available

to all personnel involved in the chemical analysis. The preparation of a formal

safety plan is also advisable.

5.3 Hydrazine sulfate (7.2.1) may reasonably be anticipated to be a carcinogen.


employed.

5.4 This device contains a laser diode light source. The device has been designed

with safety interlocks. Follow instructions for use and never attempt to defeat

the safety interlocks on this device.

6. EQUIPMENT


6.2 The turbidimeter shall consist of a nephelometer with a light source for

illuminating the sample, one or more photo-detectors to measure the amount of

scattered light at a right angle to the incident beam, a correlation means to relate

the amount of scattered light to a known turbidity standard, and a

communication means to convey the turbidity value to the plant operator or

other responsible water authority.




observed:

99

6.3.1 The incident light source (emitter) shall be a laser diode with a peak

emitting center wavelength between 650 and 690 nm. The optical system,

including the emitter, all optical elements and detector(s), shall have a

spectral peak response between 600 nm and 700 nm.

6.3.2 The rays comprising the incident beam shall be parallel with no divergence

and not to exceed 1 degree of convergence within the measurement volume.

6.3.3 Non-scattered or non-attenuated light of the incident beam after passing

through the sample shall pass into a light.


6.3.5 Detector/Light Receiver shall be centered at 90º ± 1 ½ degrees to the

incident beam.

6.3.6 Scattered light shall be received by the detector/light receiver at a subtended

angle between 20 and 30 degrees from the center-point of the measurement

volume.

6.3.7 The detector/light receiver shall have a spectral response that encompasses

the peak spectral output of the incident light source.



6.3.9 The turbidimeter shall be free from significant drift after a short warm-up

period.

6.3.10 The sensitivity of the instrument shall detect differences in turbidity of 0.01

NTU or less in waters less than 1 NTU.

6.3.11 The instrument shall be capable of measuring from 0 to 10 NTU turbidity

units. Several ranges may be necessary to obtain both adequate coverage

and sufficient sensitivity for low turbidities.

6.3.12 Instrument shall incorporate a sample deaerator for the removal of entrained

air from the sample stream.


turbidimeter.


100

7.1 Reagent water, turbidity-free: Pass deionized distilled water through a 0.2-µm

or smaller pore-size membrane filter if necessary. Water produced by reverse

osmosis is acceptable. Water should have a turbidity that is ≤0.030 NTU. This

value should be considered when preparing standards.


7.2.1 Dissolve 5.00 g hydrazine sulfate (CASRN 10034-93-2) into approximately

400 mL of reagent water contained in a cleaned 1-L Class A volumetric

flask.

7.2.2 Dissolve 50.00 g hexamethylenetetramine (CASRN 100-97-0) in

approximately 300 mL of reagent water contained in a 500-mL volumetric

flask.

7.2.3 Quantitatively transfer the hexamethylenetetramine solution (7.2.2) into the

1-L flask that contains the dissolved hydrazine sulfate solution (7.2.1).



7.2.6 Allow to stand 24 hours at 25 ± 2 °C. During this time, the formazin

polymer will develop. The turbidity of this standard is 4000 NTU.

7.2.7 Store this solution in the dark and away from a source of heat. Bring the

solution to room temperature and thoroughly mix before preparing dilutions

(7.3)

7.3 Primary calibration standards: Using a pipet with accuracy to 1 percent or

better, first mix and then dilute 25.0 mL of stock standard suspension (7.2) to

0.10 L with reagent water. The turbidity of this suspension is defined as 1000

NTU. For other turbidity values, mix and dilute portions of this suspension as

required using clean Class A glassware.

7.3.1 A new stock standard suspension (7.2) should be prepared each quarter.

Primary calibration standards (7.3) should be prepared daily by dilution of

the stock standard suspension.

7.4 Formazin in commercially prepared, certified, concentrated stock standard

suspension (SSS) may be diluted and used as required. Dilute turbidity

standards should be prepared daily.

101

7.5 Stabilized formazin suspensions or styrene divinylbenzene (SDVB) polymers

are commercially prepared, certified, and ready to use dilutions. Manufacturer’s

instructions should be followed for choosing the appropriate standard values for

the instrument.

7.6 Secondary standards may be acceptable as a calibration check, but must be

monitored on a routine basis for deterioration and replaced as required.


8.1 Online instrumentation does not require sample cooling, preservation or

storage.


9. QUALITY CONTROL

9.1 Each laboratory using this method is required to operate a formal quality control

(QC) program. The minimum requirements of this program consist of an initial


laboratory reagent blanks and other solutions as a continuing check on

performance. The laboratory is required to maintain performance records that

define the quality of data generated.




9.2.2 Linear Calibration Range (LCR) – The LCR must be determined initially

and verified whenever a significant change in instrument response is

observed or expected. The initial demonstration of linearity must use

sufficient standards to insure that the resulting curve is linear. The

verification of linearity must use a minimum of a blank and three standards.

For example, standards could be 0.3, 5.0 and 10.0 NTU. If any verification

data exceeds the initial values by ± 10% or exceeds the stated specifications

of the turbidity standard, whichever is greater, linearity must be

reestablished. If any portion of the range is shown to be nonlinear, sufficient

standards must be used to clearly define the nonlinear portion. The selection

of standards should at least cover the range of turbidity values that are

expected from samples.

102

9.2.3 Quality Control Sample (QCS) – When beginning the use of this method, on

a quarterly basis or as required to meet data-quality needs, verify the

calibration standards and acceptable instrument performance with the

preparation and analysis of a QCS. If the determined concentrations are not

within ± 10% or ± 0.030 NTU of the stated QCS values, performance of the

determinative step of the method is unacceptable. The source of the problem

must be identified and corrected before continuing with on-going analyses.

9.3 Accuracy and precision should be checked on a routine basis to monitor the

overall performance of the instrument. A series of reagent blanks and check

standards should be run to validate the quality of sample data. These checks

should occur at a frequency that is required for regulatory compliance.

9.3.1 A QCS sample as described in 9.2.3 must be run at least on a quarterly

interval. The instrument must be checked to insure it has been cleaned and

maintained according to the manufacturers recommendations prior to

running the QCS.

9.3.2 Solid standards are an option and can only be used for verification purposes.

The instrument should be checked to insure it has been cleaned and

maintained according to the manufacturers recommendations prior to

running a solid verification standard.


10.1 Turbidity Calibration: The manufacturer’s operating instructions should be

followed for calibration. Perform any cleaning and maintenance prior to

calibration as per manufacturer’s instructions. The turbidimeter measurement

chamber should be rinsed with at least 1 L of water that is filtered through a

0.45-um filter or smaller prior to calibration. Calibration should be performed

under the same ambient conditions as sample measurement.


instrument is already calibrated in standard turbidity units, this procedure will

check the accuracy of the calibration scales.


instruments permit adjustments of sensitivity so that scale values will

correspond to turbidities.



103

10.5 If a pre-calibrated scale is not supplied, calibration curves should be prepared

for each range of the instrument. Calibration must be performed under identical

optical conditions as operational conditions.

11. PROCEDURE

11.1 A sample from the treatment process is taken and flows through the

turbidimeter for measurement. It is then taken to drain or recycled back into the

process after the measurement has been taken.

11.2 The sample flow rate shall be in accordance with the instrument specifications.

The sample flow to the instrument shall be constant without variations due to

pressure changes or surges. Installation of a flow control device such as a

rotameter in the sample line can eliminate fluctuations of the flow rate.

11.3 The range of the sample temperature should be in accordance with the

instrument specifications. The sample temperature within this range should be

constant.




0.01 - 1.00 0.01

1 - 10 0.05



instructions. This was followed by running a QCS sample to verify the

determinative step for each turbidimeter was within the specified criteria.

13.2 On-Line Accuracy and Precision Testing with turbidity spikes – The Lovibond

6000 Laser Method was conducted in a qualified laboratory. Since the test and

reference instruments require continuous sample flow, a pump injection system

was used to introduce spikes of turbidity. Each turbidity spike was of constant

and stable turbidity that was generated by the addition of a defined formazin

standard that is pumped into the sample stream at a constant flow rate. The

sample itself passed through a 0.02 µm pore size filter prior to being spiked.

After the filtered sample was spiked with the formazin, it traveled through a

mixing coil that was then split into parallel feed lines that led to the test and

104

reference instruments. This provided a continuous parallel feed of sample with a

stable turbidity to both the test and reference instrument.


filtered sample or changing the actual value of the formazin standard that

was spiked into the filtered sample yielded various stable turbidity values

that were continuously delivered to the test and reference instruments.

13.2.2 The injection rate of the turbidity standard was calculated in grams/minute


allowed for the theoretical calculation of each turbidity spike. The

instrument response was calculated as a percent recovery of this spike. This

data is presented in Table 1 (Section 17.1).

13.2.3 The sequence of spikes started with a turbidity free baseline and progressed

with increasing turbidity up to the highest turbidity level.


supplied by the city of Fort Collins. The source water was from mountain

snow runoff that was treated with conventional techniques and filtered using

dual media filtration.

13.2.5 Results were used for provided the initial demonstration of linearity of the

measurement system.

13.3 On-Line testing at public water utilities – The PTV 6000 Laser Method was

tested at two public water utilities. One utility was a surface source water

treatment plant that required an additional softening step. The second plant

treated a surface source water that went through an integrated micro-filtration

membrane step. Both utilities are members of the Partnership for Safe Water.

The Lovibond 6000 laser turbidimeter and a reference turbidimeter that was

compliant with the USEPA laser nephelometry method was connected to the

same source water line for analysis. Both turbidimeters were operated for 24

hours, collecting data once per 15 seconds. The deviation between the two

instruments was 0.0003 and 0.009 NTU for the two plants respectively.

Response time to changes in turbidity differed slightly and was a function of

flow rates, but the magnitude of response was consistent.


calibration a QCS was run on each instrument to verify that the determinative


13.5 Accuracy of the Lovibond 6000 Laser Method – Accuracy (bias) was presented

as percent recoveries relative to theoretical values for the turbidity spikes

105

compared to results from the reference Hach Method 101333. Refer to Table 1

in Section 17 for a summary of all spike recovery and precision data.


The average percent recoveries of turbidity for turbidity spikes in the 0.014

to 0.10NTU range were:

Lovibond 6000 Laser Method: 101.4 %


13.5.2 Percent Recoveries for spikes in the 0.10 to 1.0 NTU range:

The average percent recoveries of turbidity for the spikes in the 0.10 to 1.0

NTU range were:



13.5.3 Percent Recoveries for spikes in the 1.0 to 10.0 NTU range:

The average percent recoveries of turbidity for turbidity spikes from the 1.0

to 10 NTU range were:



13.6 Precision Lovibond 6000 Laser Method. Precision was presented here as the

standard deviation for each of the turbidity spikes. Refer to Table 1 in Section

17 for a summary of all spike recovery and precision data.


The standard deviation for the turbidity for turbidity spikes in the 0.014 to


Lovibond 6000 Laser Method: 0.0004 NTU



The standard deviation for the turbidity spikes in the 0.10 to 1.0 NTU range

were:

Lovibond 6000 Laser Method: 0.0044 NTU.



The standard deviation for the turbidity spikes from the 1.0 to 10 NTU

range were:

Lovibond 6000 Laser Method: 0.0480 NTU.


106



quantity or toxicity of waste as the point of generation. Numerous opportunities

for pollution prevention exist in laboratory operation. The EPA has established

a preferred hierarchy of environmental management techniques that places

pollution prevention as the management option of first choice. Whenever

feasible, laboratory personnel should use pollution-prevention techniques to

address their waste generation. When wastes cannot be feasibly reduced at the

source, the Agency recommends recycling as the next best option.

14.2 The quantity of chemicals purchased should be based on expected usage during

its shelf life and disposal cost of unused material. Actual reagent preparation

volumes should reflect anticipated usage and reagent stability.






laboratories to protect air, water, and land by minimizing and controlling all

releases from hoods and bench operations; complying with the letter and spirit

of any waste discharge permit and regulations; and by complying with all solid

hazardous waste regulations, particularly the hazardous waste identification

rules and land disposal restrictions.

16. REFERENCES

1. Fourth Annual Report on Carcinogens (NTP85-002 1985), p115.

2. USEPA. “Method 180.1 Determination of Turbidity by Nephelometry,” Revision

2.0, (1993).




17.1 Summarized precision and bias (percent recovery) data in tabular form (Table

1).

107


PTV 6000 685-nm Laser Reading

Reference Turbidimeter Reading (EPA approved Method

10133)

Spike #

Baseline (Blank)

in NTU

Theoretical

Value of Spike in

NTU

Response (blank

Corrected)

Recovery (%)

Precision (SD)

Baseline (Blank)

in NTU

Theoretical

Value of Spike in

NTU

Response (blank

Corrected)

Recovery (%)

Precision (SD)

N (both Test and

Reference)

1 0.012 0.014 0.015 103.3 0.0002

0.010 0.014 0.014 102.3 0.0001 60

2 0.012 0.028 0.029 101.8 0.0002

0.010 0.028 0.029 102.6 0.0002 60

3 0.012 0.060 0.060 99.2 0.0008

0.010 0.060 0.060 99.4 0.0002 60

4 0.012 0.110 0.111 100.6 0.0007

0.010 0.110 0.112 102.0 0.0005 60

5 0.012 0.225 0.230 102.3 0.0015

0.010 0.225 0.232 103.3 0.0014 60

6 0.012 0.554 0.554 99.9 0.0055

0.010 0.554 0.559 100.8 0.0036 60

7 0.012 0.921 0.915 99.4 0.0100

0.010 0.921 0.930 101.0 0.0079 60

8 0.012 1.895 1.885 99.5 0.0070

0.010 1.895 1.928 101.8 0.0069 60

9 0.012 3.568 3.366 94.3 0.0566

0.010 3.568 3.463 97.1 0.0077 60

10 0.012 9.376 9.419 100.4 0.0804

0.010 9.376 9.472 101.0 0.0277 60

alternate test procedure (atp) validation study report for

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