Visit Our Website At : www.burtprocess.com

pH Systems Selection and Design Considerations

Presented By: Jim PearsonBurt Process Equipment404 Middlesex RoadTyngsboro, MA 01879(978) 649-9660 Fax 978 649 7430Jimpearson@burtprocess.com

October 12, 2007

pH TheorypH (H+) (OH-)0 1.0 0.00000000000001

1 0.1 0.0000000000001

2 0.01 0.000000000001

3 0.001 0.00000000001

4 0.0001 0.0000000001

5 0.00001 0.000000001

6 0.000001 0.00000001

7 0.0000001 0.0000001

8 0.00000001 0.000001

9 0.000000001 0.00001

10 0.0000000001 0.0001

11 0.00000000001 0.001

12 0.000000000001 0.01

13 0.0000000000001 0.1

14 0.00000000000001 1.0

Ion Concentration, Mol/L

•At pH 7.0, the concentration of H+ equals the concentration of OH-, both 10 –7

•pH 6.0 has 10x the concentration of H+ as pH 7.0

•pH 5.0 has 100x the concentration of H+ as pH 7.0

•pH 4 has 1000x the concentration of H+ as ph 7.0

•Acids are characterized by excess H+, pH 0 - <7

•Caustics are characterized by excess OH-, pH >7 – 14

•Neutral water pH = 7

pH Theory

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14+413 +354 +295 +236 +177 +118 +59 00 -59 -118 -177 -236 -295 -354 -413

Acids Bases

Chart shows mV values generated by a glass measuring electrode at 25° C

Beware of HF Acid!

•Hydrofluoric Acid will quickly destroy a pH electrode.

•pH affects the aggressiveness of the Fluoride.

•In very acidic solutions, only a few ppm will quickly attack the glass.

•In high pH solutions (pH 10-11), Fluoride in low concentrations can be

handled.

Beware of DI Water!

•Deionized water acts as a vacuum against the high concentration of ions in the electrode. This

causes rapid depletion – short lifespan of the electrode.

•In addition, high velocity of DI water across the glass membrane will cause a static charge on the

surface, resulting in an erroneous low pH reading.

•DI water has poor buffering capabilities therefore, small doses of acids or caustics can

result in large swings in the pH.

System Components

pH Probe Care

Clean with a dilute solution of HCL or with NAOH

Calibrate monthly to determine depletion of reference solution

Use HF resistant pH electrodes when applicable

Proportional Control

Advantages:

•More precise pH adjustment control

•Reduction in reagent costs

•Avoids set-point overshoots

1 2 3 4 5 6 7 8 9 10 11 12 13 14

NAOH Pump Speed

H2SO4 Pump

Speed

pH Units

Limestone Chip Vs. Reagent Chemical Systems

ADVANTAGES• Inexpensive Capital Cost

• Low Maintenance

• May Be Suitable For Multiple Drains At Low Volume

DISADVANTAGES• Only One-way pH Adjustment

(to raise pH)• Failure To Adjust pH Without

Notice When Chips Are Exhausted

• Failure To Adjust pH Of Concentrated Dumps

• May Clog Due To Debris Entrapment

• May Generate Bacterial Growth, Odor, And Health Risk

• Chip Maintenance And Disposal Is Costly Requiring System Shutdown

• High Risk Of Non-compliance

Reagent Treatment System

Single Stage

Adjust pH in either direction reducing non-compliance risk

Improved odor control

Less retention time required resulting in smaller treatment tanks

System shutdown is generally not required for maintenance

System Type SelectionBatch Vs. Continuous

Why Select Batch over Continuous?

•pH of effluent should never be out of discharge permit compliance! Batch systems are best for this.

•Batch systems are practical when entire waste stream can be collected in holding tank for treatment.

•Most batch systems utilize two tanks so that when one tank is being treated the other is collecting effluent from processes.

Considerations

•Batch systems require an operator to monitor the neutralization and dump process unless fully automated.

•Not a good choice for large flows.

Why Select Continuous over Batch?

•Waste stream volume is large enough to require oversized holding tanks.

Considerations

•Possible discharge that is out of spec with permit levels.

•Safeguards are required to monitor system condition.

Reagent Treatment System

Dual Stage

Other Considerations

• Consider dual stage (two treatment tanks) systems for high-flow applications, when chemical concentration discharges are elevated, when effluent discharge limits are tight, and for waste streams that are predominately ultra-pure water.

• Pre-buffering ultra-pure water will aid in the neutralization process. This can be accomplished by adding limestone or metering in sodium carbonate.

• Stagnant pH systems with a pH below 7.0 have a tendency to release H2S (hydrogen sulfide) gas. In cases where systems sit for extended periods of time, a city water flush line is recommended.

UL ListedControl Panels

In July 2002 BPE received its UL 508A certification from Underwriters Laboratories. The UL 508A Standard is used to evaluate Enclosed Industrial Control Panels and certifies that the components and construction comply with the applicable NEC, ANSI/NFPA 70 guidelines. The certification insures that a panel marked with the UL label is built with UL listed or UL registered components and that the construction is compliant with the Type requirement for the enclosure.

Flow EstimationAssumptions:

Lab Sink = 1 GPM

Cup Sink = .5 GPM

Actual Usage is 25% to 35%

15 To 20 Minute Detention Time (in some cases more time is required).

Sample Calculation:

50 Lab Sinks = 50 GPM

50 Cup Sinks = 25 GPM

75 Total GPM X 30% Actual Usage = 22.5 GPM

22.5 GPM X 15 Minute Detention Time = 337.5 Gallon Treatment Tank(s) Required.

Note: Animal cage and dish washers have not be calculated into the above example. These devices should be considered when sizing the system due to their elevated instant flow.

The Batchmaster system offers an Inherently Safe feature as a hybrid continuous/batch design. A shut-off valve diverts effluent when pH is out-of-specification. The Inherently Safe feature is

available as an option on Single and Dual Stage Systems and pH Plus Modules.

Batchmaster Neutralization

Batchmaster Neutralization

CAD Drawings

Effluent Flow Meter

System Components

Typical Single Stage System control panel with circular chart recorder.

Reagent tank and metering pumps used in a Dual Stage System.

• Designed and Assembled by BPE• NEMA Rated • Digital Microprocessor Based

Controllers• Explosion Proof Rated Panels• Programmable Logic Controllers or Relay Logic• PC Interfaces

Features

• Duplex Pump Controls• pH / Flow Monitoring and Recording• Waste Treatment Systems• Automatic Process Systems

Applications

Control Panels

• Wide range of flow and head capabilities• Rugged acid, caustic, and solvent Resistant Construction• Sumps constructed of Polypropylene, polyethylene, stainless

steel, and FRP• Corrosion resistant pump – CPVC, polypropylene, stainless

steel, Teflon, and other materials• Standard models in polypropylene (PPS) and polyethylene

(PES)• Stainless steel models for use in intrinsically safe environments• Automatic pump control• Simplex and duplex design• Standard and custom sizes

Pump Transfer Stations

Pump Selection

BPE standard pump transfer stations come with vertical centrifugal pumps designed for use with corrosive chemistries. When selecting a pump consider the following:

•Required TDH

•Chemistry to be pumped

•Class1, Div. 2 requirements

•Wash-down conditions

Tank Selection

BPE fabricates standard and custom sumps out of Polypropylene, Polyethylene, FRP, and Stainless Steel.

Consider the following when selecting a sump:

•Temperature

•Chemical compatibility

•Volume

•Specific gravity

•Footprint

Burt Process Partial Customer List

Pharmaceutical /Biotech• Merck

• Pfizer

• Johnson & Johnson

• Bristol Meyers Squibb

• Smith Kline Beecham

• Bayer

• AstraZeneca

• Millenium

• Genzyme

• Genetics Institute

• Human Genome Sciences

Electronics• IBM

• Corning

• Sanmina / Hadco

• Teradyne

• Raytheon

• National Semiconductor

• Fairchild• Olin Microelectronics

Other• Tiffany

• Pratt & Whitney

• Harvard University

• Mass. General Hospital

• Ionics / Toray

• Stonyfield

• Kodak

• Polaroid

BURT PROCESS EQUIPMENT can offer service contacts on all of its manufactured products as well as provide installation and startup assistance. With 3 dedicated service vans and 4 full

time service technicians, BPE can provide the support for today’s complicated process tooling and wastewater treatment systems.

Visit our web site: www.burtprocess.com Email: info@burtprocess.com

Field Service