optical brightener testing in mill creek, the dalles, orhanson, deq laboratory volunteer monitoring...

Oregon Department of Environmental Quality

Optical Brightener Testing in Mill Creek, The Dalles, OR

By: Steve Hanson November 2013

Last Updated: 10/01/13

By: Jane Doe

DEQ 03-??-###

Laboratory & Environmental Assessment Division, Water Quality Monitoring Section 3150 NW 229th Ave, # 150

Hillsboro, OR 97124

Phone: (503) 693-5700

(800) 452-4011

Fax: (503) 693-4999

Contact: Steve Hanson

www.oregon.gov/DEQ

DEQ is a leader in

restoring, maintaining and

enhancing the quality of

Oregon’s air, land and

water.

State of Oregon Department of Environmental Quality ii

This report prepared by:

Oregon Department of Environmental Quality

811 SW 6th Avenue

Portland, OR 97204

1-800-452-4011

www.oregon.gov/deq

Contact:

Steve Hanson

503-693-5737

Alternative formats (Braille, large type) of this document can be made available.

Contact DEQ’s Office of Communications & Outreach, Portland, at

503-229-5696, or toll-free in Oregon at 1-800-452-4011, ext. 5696.

State of Oregon Department of Environmental Quality iii

Optical Brightener Testing in Mill Creek

Table of Contents Executive Summary .................................................................................................................................... 1

Background ................................................................................................................................................. 1

Optical Brighteners ................................................................................................................................. 2

Methods....................................................................................................................................................... 3

Optical Brightener Cotton Absorption Method ...................................................................................... 3 Absorbent Pads ................................................................................................................................... 3

Deployment ........................................................................................................................................ 3

Split Sample Comparisons...................................................................................................................... 4 Locations ............................................................................................................................................ 4

Retrieval and Post Deployment Processing ........................................................................................ 6

Split Sampling ........................................................................................................................................ 7

Results ......................................................................................................................................................... 8

Initial Deployment .................................................................................................................................. 8 Pipe Discharge .................................................................................................................................... 8

Mill Cr. Above Pipe Discharge .......................................................................................................... 8

Drain Pipe ........................................................................................................................................... 9

Wetland .............................................................................................................................................. 9

Initial Optical Brightener Results ..........................................................................................................10

Follow Up Deployment .........................................................................................................................12 Pipe Discharge ...................................................................................................................................12

Mill Cr. Above Pipe Discharge .........................................................................................................12

Mill Cr. Above Skyline (Below Pipe Discharge) ..............................................................................13

Skyline Cr. Above Storm Drain ........................................................................................................13

Skyline Cr at Mouth ..........................................................................................................................14

Mill Cr Below Skyline ......................................................................................................................15

Whiskey Gulch at Mouth ..................................................................................................................15

Follow Up Deployment Results ............................................................................................................16

Split Sample Results ..............................................................................................................................17

Discussion ..................................................................................................................................................18 Result Implications ............................................................................................................................18

Optical Brightener Cotton Absorption Method Performance ...........................................................19

Split Sample Recommendations ........................................................................................................19

Works Cited ...............................................................................................................................................19

State of Oregon Department of Environmental Quality 1


Executive Summary In the summer of 2013, the DEQ Laboratory worked with The Dalles Watershed Council and City of The

Dalles to investigate the source of unusually high counts of the fecal bacteria indicator Escherichia coli

in Mill Creek, which flows through the city. This report details the methods used to determine a source of

the high E. coli levels was likely domestic wastewater. The work also allowed DEQ to gain a better

understanding of the effectiveness of using an optical brightener survey to detect for E. coli in water

bodies and to see if this method could be used in other areas of the state.

During the summers of 2011 and 2012, the watershed council had collected data showing high E. coli

readings in the vicinity of a pipe entering the creek near Wright Street and W. 23rd Street in The Dalles.

DEQ and its partners employed the use of optical brightener absorbent pads to screen for the presence of

domestic wastewater and conducted side-by-side sampling for E. coli and conductivity with the

watershed council.

Optical brighteners are a common additive to laundry detergents. The brighteners adhere to cotton and

fluoresce when viewed under ultraviolet light. Deploying cotton pads at a site and then viewing them

under ultraviolet light provides a simple and low-cost way to screen for the presence of domestic

wastewater.

Results showed that the pipe discharge did contain detectable concentrations of optical brighteners. This

indicates the pipe discharge likely contains domestic wastewater which could be the source for E. coli

concentrations consistently measured over 2,420 E. coli/100 mL by the watershed council. The optical

brightener results still require additional testing to identify the source for the wastewater. Systematic dye

tests in the adjacent homes provide the most definite source tracking. The best chance of determining

connectivity between a home’s wastewater and the pipe involves the use of multiple dyes paired with

charcoal adsorption packets.

Optical brighteners were not detected in any other sites. The failure of sites immediately downstream

from the pipe discharge to return positive results implies limitations on the method. Results from the

project indicate that the optical brightener method proved capable of working in small discharges from

pipes but did not prove successful in streams.

Side-by-side sampling of E. coli and conductivity between the DEQ and watershed council was

conducted at the council’s routine monitoring locations. Results from these samples indicate that The

Dalles Watershed Council data accurately represent environmental conditions.



Background In June 2013, DEQ regional water quality permit specialist Jayne West asked the DEQ Laboratory staff

to review bacteria data collected by The Dalles Watershed Council from Mill Creek in The Dalles,

Oregon. Lab staff reviewed the data to determine if there was an issue that warranted follow-up. A quick

graphing exercise demonstrated the concentrations in Mill Creek were indeed well in excess of

designated water quality standards and seemed to show a consistent sharp increase moving downstream

at specific locations.

Figure 1: Initial chart of The Dalles Watershed Council Escherichia coli data from Mill Cr during the summers of 2011 and 2012

After discussions with Jayne West, Anna Buckley (The Dalles Watershed Council coordinator) and Steve

Beyers (City of The Dalles wastewater collection) it was determined that there was a discharge from a

pipe believed to be a source of bacteria. The city of The Dalles tried to trace the pipe with limited

success. The city also conducted dye and smoke tests as well as “slip lining” a nearby wastewater

collection pipe in case bacteria concentrations could be coming from the pipe. None of these actions

identified the bacteria source in the pipe or measurably decreased the quantity of water or concentration

of bacteria in the pipe. The watershed council expressed interest in the DEQ lab conducting sample

analysis to identify potential sources for the high bacteria numbers. DEQ determined that it did not have

available funds at the time to conduct any such analysis for tracers like steroids, caffeine or common

medications.

After consulting with additional experienced water quality monitoring specialists at the DEQ lab, Steve

Hanson, DEQ Laboratory volunteer monitoring coordinator, summarized four actions the lab staff

recommended to resolve the issue of where the bacteria were coming from:

1. Optical brightener surveys

2. Upstream investigations looking at the drainage feeding the area of the pipe



3. Additional dye testing in all toilets of the home closest to the pipe discharge, and

4. Additional dye testing in nearby homes.

An optical brightener survey was chosen as a feasible next step due to its low cost and relative ease. In

addition, DEQ staff were interested in testing the usefulness of the method for potential application in

other locations around the state.

Optical Brighteners Optical brighteners are chemicals added to most laundry detergents to help increase the “whiteness” of

fabric. The brighteners are designed to adhere strongly to cotton. In the presence of UV light the adhered

brighteners give a strong fluorescing signal, as demonstrated in Figure 2 below. The widespread use of

optical brighteners and relative ease of detecting their presence has made optical brighteners a cost-

effective indicator for the presence of domestic wastewater in surface water.

Figure 2: Fluorescing signal of gauze pads exposed to serial dilutions of Tide® laundry detergent. The concentration of detergent in the bottom, brightest pads simulates concentration in a standard 10 gal/cycle clothes washer (0.15% detergent by volume).

The method does have a number of limitations. Certain scenarios could be described that could lead to

fecal contamination from domestic sources that do not contain optical brighteners, or cases where optical

brighteners may be found in runoff free from fecal contamination. Optical brighteners may be absent

from domestic wastewater, particularly if only a single residence is being tested. A number of commonly

used “free” type laundry detergents are available on the market that in addition to being fragrance free

may be free of optical brighteners. Given the limitations of the method, it is accepted that testing for

optical brighteners using cotton pads is not an absolute test for domestic wastewater contamination.



Methods

Optical Brightener Cotton Absorption Method The qualitative method DEQ used in this survey was adopted from an archived article from Nature’s

Compass newsletter from the Eight Towns and the Bay community coalition in Massachusetts (Sargent

& Castonguay, 1998). Cotton pads free of any brighteners are deployed in areas with potential domestic

wastewater contamination. In this survey the pads were deployed on site for six to seven days. The pads

are retrieved from the field then viewed under a UV lamp to check for fluorescence.

Absorbent Pads

The Mill Creek study used two different types of cotton absorbent pads. Sterile 2 x 2-inch medical gauze

pads from a first-aid kit were the first cotton material deployed. The second deployment used VWR

Scientific 4 x 4-inch cotton pads as described in the referenced method. Each pad type was checked for a

negative fluorescence before deployment. Performance of the materials is discussed in the results and

discussion sections.

Deployment

Because optical brighteners have a strong affinity for cotton fabric, a cotton pad exposed to flowing

water should accumulate optical brighteners and produce a fluorescing signal proportional to the total

“load” of optical brighteners. Optical brightener load increases with increased concentrations of

brighteners in the water and the volume of water to which the pad is exposed. The volume of water

flowing over a pad will depend on water velocity near the pad—the faster the water, the greater the

volume of exposure over time. Figure 3 below shows two pads exposed to the same concentration of

detergent. The pad on the left was exposed to a single 100 mL concentration; the pad on the right was

exposed to two additional 100 mL volumes of the same concentration.

Figure 3: Two cotton pads were exposed to different volumes of the same concentration of laundry detergent. The pad on the left was exposed to a single volume (approximately 100 mL) of 0.0015% detergent by volume. The pad on the right was exposed to the same concentration and volume three times.

Optical brighteners used in most detergents are somewhat sensitive to sunlight (AVM Chemical

Industries, 2008) and should therefore be protected from sunlight during deployment and after retrieval.

The pads were inserted into poly net sleeves fastened shut at the ends with zip ties. The purpose of the

poly net was to provide support to the cotton pad. The poly net was then fastened to some type of

deployment device, either in a flow-through sample bottle, fastened directly to a wire in the stream, or

inserted over deployment canisters. Photos below show the three deployment methods.



Figure 4: Deployment devices for cotton pads in Mill Creek always included placing pads in poly nets. The poly nets were then placed in flow-through cell plastic bottles, attached free in the stream to a wire, or fastened to steel flow-through canisters secured in the stream.

Side-by-Side Sample Comparisons DEQ has established data quality objectives for the parameters measured by The Dalles Watershed

Council. The equations below represent the calculations used for comparing specific conductance and E.

coli.

Specific Conductance

E. coli

The expected range for specific conductance measurements is ± 7 percent relative percent difference, and

for E. coli the range is ± 0.6 log units.

Locations

Locations for deployment were chosen based on stations with historically high bacteria concentrations or

areas that could be contributing to high bacteria concentrations. Pads were deployed twice: first from

Aug. 13 to Aug. 20, 2013; and again from Sept. 3 to Sept. 10, 2013. Aerial photos below show

deployment locations.



Figure 5: Optical brightener adsorptive pad deployment locations in the vicinity of high-bacteria concentration pipe discharge, Mill Creek drainage, The Dalles.



Figure 6: Optical brightener adsorptive pad deployment location at Whiskey Gulch location with high bacteria concentrations, Mill Creek drainage near The Dalles.

Retrieval and Post Deployment Processing

The pads were removed from the field after six to seven days in the stream. Upon retrieval the pads were

cleaned in the tested water as much as possible to remove build up of periphyton, debris and aquatic

organisms. The cleaned pads were placed directly into labeled brown 125 mL bottles to protect them

from sunlight. The pads were initially viewed and photographed under a six-watt long-wave UV (365nm)

lamp in an Idexx view box within a few hours while the pads were still wet. Upon return to the DEQ lab

pads received further cleaning using deionized water to remove additional debris that did not come off

when cleaning in the field. The pads were then stapled to cardboard sheets with the corresponding site

names written on the cardboard and allowed to dry at room temperature protected from direct light either

in the view box or under an aluminum tent vented for drying. After drying, the pads were viewed and

photographed under the same UV light in the Idexx view box. The cardboard sheets were then wrapped

in aluminum foil and labeled.



Side-by-side Sampling In addition to optical brightener deployments, a split sample was conducted on Sept. 3, 2013 to establish

comparability between samples collected and analyzed by DEQ and The Dalles Watershed Council.. The

split samples included side-by-side analysis at 13 sites (Figure 7) for conductivity and temperature as

well as collection of E. coli samples. Samples for E. coli were returned to each organization’s respective

analytical facilities and processed according to their standard procedures.

The primary parameters of concern for the split sample are specific conductance and E. coli because

these parameters respond to fecal contamination. Since wastewater will typically have high

concentrations of salts, conductivity of wastewater is expected to be higher than ambient water

conditions. Escherichia coli is the bacterium most widely used as an indicator for fecal contamination in

Oregon freshwater. The Oregon water quality standard for human contact states that no samples should

exceed 406 MPN/100mL of E. coli.

Figure 7: Split sampling locations for conductivity, temperature and E. coli side-by-side sampling.



Results Results for the optical brightener deployments and split sample are in Table 1 on page 18.

Initial Deployment Initial deployment was conducted on Aug.13, 2013 with Steve Hanson (DEQ Lab), Steve Beyers (City of

The Dalles), Anna Buckley, and Abbie Simmons (The Dalles Watershed Council). Pads were deployed

at the pipe discharge, in Mill Creek above the pipe discharge, in the city stormwater manhole in a drain

pipe that collected subsurface water from a wetland above Wright Street, and in a hole dug in the

wetland.

Pipe Discharge

The team deployed a poly net sleeve with two gauze pads in a flow-through plastic bottle secured to two

large nails. Flow from the pipe, estimated at 0.02 cfs, poured into the top of the bottle and exited a large

hole cut above the location of the poly net. To gain access, workers cleared blackberry shrubs around the

pipe discharge area. At retrieval the flow-through bottle had thick, grey algal mass and roughly 50 snails

on its exterior. There was still strong flow circulating throughout the bottle. The gauze and poly net had a

large number of worms living in and around the pads.

Figure 8: Pipe discharge pad deployment photos showing placement of flow-through cell and organic matter at retrieval in the bottle and poly net.

Mill Creek Above-Pipe Discharge

The team chose this site as a background site to see if optical brighteners were present above the pipe

discharge. They threaded two separate poly net sleeves, each with two gauze pads, through a wire

wrapped around a small boulder near the center of Mill Creek flow just upstream from the pipe

discharge. One of the poly net sleeves had an additional fiberglass screen to protect the gauze. At

retrieval, the water velocity near the boulder was 1.3 ft/sec, but the poly net was fastened under the small

boulder to protect the pads from sunlight. The measured velocity in the immediate vicinity of the poly net

was approximately 0.1 ft/sec.



Figure 9: Mill Creek above-pipe discharge deployment site Aug. 13 to 20, 2013, showing above and below the small boulder where the poly net was deployed and the two sets of gauze pads at retrieval.

Drain Pipe

The team chose this site to characterize water collected by a drain pipe that was described by Steve

Beyers as collecting water from the sloping wetland above Wright Street. The drain was accessed

through a manhole on Wright Street. Workers weighted down two gauze pads in a poly net sleeve with a

small cobble stone in the poly net and then fastened the net with zip ties to a larger cobble in order to

weigh the pads down so they could be placed in fast-flowing water in the storm drain pipe. This poly net

was then tied to a strong fishing line and lowered into the manhole and swung into place so it rested

solely in the drain pipe coming from the wetland. The fishing line was then fastened to a ladder in the

manhole. At retrieval the poly net was still in position and receiving good flow. Because the team was

not able to enter the manhole to rinse the gauze with sample water, they used a small amount of

deionized water to clean the gauze pads.

Figure 10: Drain pipe deployment photos showing weighted poly net, inflowing drain pipe location with poly net in place and the gauze pads after retrieval.

Wetland

The team also sampled the wetland above the drain pipe site to investigate the potential for contaminated

shallow groundwater that came to the surface in the area above the drain pipe. A hole was dug and two

gauze pads were placed in a poly net and secured in a vented plastic bottle to protect the pads if the hole

collapsed. The hole was 12 to 16 inches deep and approximately half full of water by the time the team

completed the deployment. By Aug. 20 the hole was full of water. Because there was very little flow

through the site, only one of the pads was retrieved on Aug. 20. Team members retrieved the second pad

on Sept. 10.



Figure 11: Wetland site photos showing the wetland, deployment hole at retrieval on Aug. 20 and vented bottle.

Initial Optical Brightener Results

The pipe site had a strong fluorescing signal while the site above the pipe, the drain site and the wetland

site all did not produce a visible fluorescing signal. Figure 12 below shows images of the readings both

immediately after retrieval and after deionized water cleaning. The gauze’s physical structure did

degrade during deployment at sites with stronger flow like the pipe site. The gauze at the pipe was also

disturbed by the worms entwined in the gauze strands at retrieval. The gauze’s structure was more intact

for the set that was deployed above the pipe with a protective fiberglass screen. Because both the screen

and poly net gauze pads were both negative, there was no way to determine the impact the screen may

have had on the gauze’s overall exposure to site water.



Figure 12: August 13 to 20 optical brightener pads after retrieval. Top: Prior to initial reading under ambient light; Middle: Initial reading under UV light; Bottom: Final reading after additional deionized water cleaning and drying under six-watt, 365nm UV light.



Follow-Up Deployment The team expanded monitoring for the second deployment to include more sites on Mill Creek and other

tributaries that had shown high E. coli concentrations. Steve Hanson, Anna Buckley and Abbie Simmons

deployed the pads. Localized rains occurred on Sept. 5 and 6 with a reported total rainfall of 0.49 inches

at The Dalles airport. Photos taken at deployment and retrieval indicate Mill Creek was flowing higher

on the Sept. 10 than on Sept. 3 and 4. Preliminary streamflow data from the Oregon Department of Fish

and Wildlife gage at Mill Creek at Mile 1.7 did not rise over the gage’s detection level of 2 cfs (Faber,

2013).

Pipe Discharge

The team deployed a poly net sleeve with two VWR cotton pads on Sept. 3 in a flow- through plastic

bottle secured to two large nails. Flow from the pipe was comparable to the 0.02 cfs estimated in August.

The area around the pipe discharge had a noticeable increase in thick, grey periphyton, as observed in

August at retrieval. At retrieval the flow-through bottle had a thick, grey algal mass and snails on its

exterior. There was still strong flow circulating throughout the bottle. The gauze and poly net had worms

living in and around the pads. Figure 8 photos from the August deployment are representative of the

September deployment.

Mill Creek above-Pipe Discharge

The Sept. 3 deployment of pads employed a canister to deploy two pads above the pipe. The team placed

the canister in flowing water suspended from a small log. The canister improved flow across the surface

of the pads relative to the deployment in August where the pads were under a small boulder.

Figure 13: Mill Creek above pipe discharge canister deployment location and cotton pads at retrieval.

.



Mill Creek above Skyline (Below Pipe Discharge)

On Sept. 4, the team deployed a canister with two cotton pads secured in poly net sleeves in Mill Creek

between the pipe discharge and Skyline Creek confluence. This site is approximately 150 feet

downstream of the pipe and was chosen to investigate the sensitivity of the method in detecting optical

brighteners. Unpublished data collected at the site by the Oregon Department of Fish and Wildlife and

provided to the watershed council indicate average stream discharge during the deployment of less than 2

cfs. Flow from the pipe was estimated in August as 0.02 cfs. The resulting dilution of the pipe water

would be 1:100 (pipe flow 1% of Mill Creek flow). The canister was initially deployed above a small

drop between two small boulders. At retrieval the canister had moved five feet downstream to below the

drop but still in good flow.

Figure 14: Mill Creek above Skyline tributary site at retrieval. The photo at left shows the canister (see arrow) below the small rapid. The canister was deployed just above the rapid. The photo at right shows the pads at retrieval.

Skyline Creek above Storm Drain

Skyline Creek has demonstrated high E. coli concentrations at its mouth. In August Steve Beyers of the

city of The Dalles had identified where the Wright Street storm drain discharges into the Skyline

tributary. This site is located just above where the storm drain enters Skyline. The team sampled a

tributary to the storm drain called the wetland drain in August for optical brighteners (See photo in

Figure 10). The Skyline site above the storm drain was intended to show if there were detectable optical

brighteners in this small tributary above the storm drain discharge. The team deployed a canister with

two cotton pads secured in poly net sleeves on Sept. 3 under a small drop in the creek with the pads

submerged with good flow through. Rocks were arranged around the canister to protect it from sun and

keep it less visible without obstructing flow through the canister. At retrieval, there was sediment accrual

on the canister but good flow still coming down onto the canister.



Figure 15: Skyline tributary above storm drain deployment site with canister under rocks and pads after retrieval.

Skyline Creek at Mouth

The team placed a second canister with two cotton pads at the mouth of Skyline Creek below the storm

drain. This location has been an E. coli monitoring site for the watershed council with a median E. coli

concentration of 980 MPN/100mL (23 samples from 2011 and 2012, see Trib 1.78 in Figure 1). The

canister was placed in fast-flowing water with the cotton pads completely submerged.

Figure 16: Skyline Creek at mouth deployment site with canister deployed and pads at retrieval.



Mill Creek below Skyline

On Sept. 4 the team deployed a canister with two cotton pads in Mill Creek below Skyline Creek at the

site designated by the watershed council as MLC 1.71. Watershed council samples from the previous two

years at this site had median concentration of 1050 MPN/100mL (32 samples). This deployment, like the

site below the pipe, was selected to see if the method would be able to detect optical brighteners once

they were diluted in Mill Creek. The canister was deployed in a strong current and remained in place

throughout the deployment.

Figure 17: Mill Creek below Skyline Creek deployment site and pads in canister at retrieval.

Whiskey Gulch at Mouth

Whiskey Gulch is a small tributary to Mill Creek slightly over a mile upstream of the pipe discharge. The

watershed council reported high E. coli concentrations at this site although the five samples collected the

previous two years showed a median value of only 24 MPN/100mL. The creek was too small to deploy a

canister at the site so a pair of cotton pads were secured in a poly net with zip ties and attached to a nail

in the stream. There was noticeable accumulation of sediment at retrieval.

Figure 18- Whiskey Gulch deployment of poly net in stream and with pads after retrieval.



Follow-up Deployment Results The team recovered all pads on Sept. 10, including the second pad from the Aug. 13 deployment in the

wetland. The pads were initially read by selecting the pad in the best physical condition from each site

and viewing them under the UV lamp (Figure 19). The following day the pads were cleaned with

deionized water, stapled to two separate pieces of cardboard and allowed to dry while covered by vented

aluminum foil. The pads from the pipe discharge were the only pads to demonstrate a fluorescing signal.

The cotton pads did not perform as well as the gauze pads. The cotton pads lacked the physical strength

of the gauze, which made cleaning very challenging. With careful cleaning the pads did clean up to a

base white color, but the initial reading on Sept. 10 was challenging because the pads were difficult to

clean in the stream. At sites with strong flow, like the pipe discharge and the site on Mill Creek below

Skyline Creek, the pads had nearly no physical cohesiveness.

Figure 19: September 3 and 4 to Sept. 10 optical brightener pads after retrieval on Sept. 10 showed some discoloration and were very fragile physically. The upper right-hand pad is blank pad. The photos from the UV view box were divided into two photos to capture all the pads on the paper.



Figure 20: September 3 and 4 to Sept.10 optical brightener pads after deionized water cleaning and drying were distributed on two pieces of cardboard so both pads from each site could be displayed. The photos at left show the following sites from left to right : Mill Creek above pipe; Mill above Skyline Creek, Mill below Skyline, and pipe discharge. The photos on the right show the cardboard containing the following sites from left to right: wetland (only one pad); Whiskey Gulch; Skyline above storm drain; and Skyline at mouth.

Side-by side Sample Results All side-by-side sampling results compared well within the expected range of variability for the

parameters. Temperature results were all within 0.1 to 0.2 ºC. Specific conductance showed a slight

negative bias but had a maximum difference of -3 percent. The bias is acceptable and may represent a

slight difference in calibration. The E. coli results did not show a consistent bias and were all within 0.2

log difference. The results for specific conductance and E. coli are presented in Table 1 below.



Table 1: Optical brightener deployment and split sampling summary results A blank cell indicates the data was not collected. For optical brightener results a “No” means the pad did not show a visible fluorescing signal under the UV lamp and a “YES” indicates that fluorescing was visible under the UV light. Split sample results include the reported values for DEQ and watershed council as well as the calculated fields of relative percent difference of specific conductance results and the log difference of E. coli results.

Site Description

Optical Bright. Pad Fluoresce August (days deployed)

Optical Bright. Pad Fluoresce September (days deployed)

Specific Conductance Split Sample

E. coli Split Sample

DEQ µS/cm

WSC µS/cm

Rel.% Diff

1

DEQ MPN/ 100mL

WSC MPN/

100mL

Log Diff

2

Mill Cr at RM 0.3 327 321 -2% 1553 1203 -0.1

Mill Cr at RM 0.8 324 318 -2% 1733 1413 -0.1

Mill Cr at RM 1.1 318 311 -2% >2420 >2420 OK

Mill Cr at RM 1.71 No (6) 315 309 -2% 1986 >2420 >0.1

Skyline at Mouth No (7) 610 593 -3% 2420 1733 -0.1

Skyline abv storm drain No (7)

Mill Cr above Skyline No (6)

Pipe Discharge YES (7) YES (7) 598 591 -1% >2420 >2420 OK

Mill Cr above pipe No (7) No (7)

Wetland Drain No (7)

Wetland No (7) No (28)

Mill Cr at RM 1.9 285 277 -3% 328 326 0.0

Whiskey Gulch at mouth No (7) 635 620 -2% >2420 >2420 OK

Mill Cr at RM 3.8 167 164 -2% 921 687 -0.1

Mill Cr at RM 5.0 150 147 -2% 225 365 0.2

Mill Cr at RM 5.6 (primary)

131 130 -1% 488 435 0.0

Mill Cr at RM 5.6 (duplicate)

131 130 -1% 770 579 -0.1

N. Mill Cr at RM 0.12 131 130 -1% 93 165 0.2

S. Mill Cr at RM 0.2 87 87 0% 99 66 -0.2 1. Rel. % Diff = (WSC result – DEQ result) ÷ Average of WSC and DEQ result 2. Log Diff = log(WSC result) – log(DEQ result)

Discussion Result Implications

The optical brightener results from both deployments indicate a high likelihood that the pipe discharge

contains domestic wastewater. Possibly significant concentrations of wastewater are indicated by the

intensity of the optical brightener signal coupled with E. coli results consistently exceeding the maximum

detection for the method and levels established by the state as safe for water contact. Optical brighteners

were not observed at any of the other sites including the Mill Creek site below the pipe discharge and at

Whiskey Gulch—both sites with bacteria concentrations in excess of 2420 MPN/100mL during the split

sampling.

The results from Mill Creek above Skyline Creek demonstrate the optical brightener method may not be

sensitive enough to screen for domestic wastewater sources of bacteria in streams of this size. The lack

of sensitivity in the method means that domestic wastewater may not be excluded as a possible source for

the high E. coli results observed at many sites in Mill Creek Drainage despite the negative optical

brightener results.



Optical Brightener Cotton Absorption Method Performance

The optical brightener method proved capable of working in small discharges from pipes but did not

prove successful in streams. Failure to detect optical brighteners in the stream downstream from the pipe

discharge indicates insufficient method sensitivity in cases where domestic wastewater is not

concentrated in a point discharge. There is some concern about photo decay of the optical brighteners in

the stream, but the stream distance traveled by the water after it exited the pipe discharge seems

insufficient to provide enough time and light to significantly decay the optical brighteners. Considering

that the chemicals must maintain some photo resilience in order to function as brighteners on clothes,

insufficient method sensitivity is the most likely source for negative results at the two Mill Creek sites

below the pipe discharge.

The more rugged cotton gauze pads proved easier to work with than the cotton pads recommended in the

method referenced (Sargent & Castonguay, 1998). Perhaps another option would be to find white cotton

fabric that did not contain optical brighteners. This would be even more rugged than the gauze. For

deployment methods the poly net method worked fine and a similar physical support would certainly be

recommended if cotton pads are used for future deployments. The steel canisters were used because they

were available, but short sections of large PVC pipe would also be a viable deployment option.

Side-by-side Sample Recommendations

The Dalles Watershed Council followed the recommended field methods and lab analysis appeared to be

well done. Comparison of the results indicates the watershed council collected data representative of

environmental conditions.

Works Cited AVM Chemical Industries. (2008). Chemistry of Optical Brightener and uses in Textile Industries and its

Mechanism. Retrieved September 2013, from http://www.avmchemical.com/data/uploads/articles/article-

3chemistry-of-optical-brightener-and-uses-of-in-te.pdf

Faber, D. (2013, October 4). SFWB/Project Leader The Dalles Fish Research. The Dalles, OR: Oregon

Dept. Fish and Wildlife.

Guess, K. (2003, January). The Dalles Watershed Assessment. Retrieved September 2013, from

http://wascoswcd.org/linked/tdwsassessment.pdf

Sargent, D., & Castonguay, W. (1998). Water Quality Sampling An Optical Brightener Handbook.

Retrieved August 2013, from Eight Towns and teh Bay Nature Compass Archive:

http://nature.thecompass.com/8tb/sampling/

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