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Visit Our Website At : WelcomeWelcome pH Systems Selection and Design Considerations Presented By: Jim Pearson Burt Process Equipment 404 Middlesex Road Tyngsboro, MA (978) Fax October 12, 2007
pH Theory pH (H+)(OH-) 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 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 NAOH Pump Speed H 2 SO 4 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 Selection Batch 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 H 2 S (hydrogen sulfide) gas. In cases where systems sit for extended periods of time, a city water flush line is recommended.
UL Listed Control 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 Estimation Assumptions: 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 = 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
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: Field Service