Wastewater System Flocculation and Cold Weather
February 6, 2015
Once again the cold months of the heart of winter are upon us. With the cold weather comes a variety of potential problems for the wastewater treatment process. These include:
- Poor floc formation
- Slow coagulation/agglomeration in neutralization tanks
- Reduced settling time in clarifiers
Let’s look at the polymer preparation stage:
Polymers require water to “hydrolyze” the liquid concentrate (as-is shipped in the drum form). By adding water for dilution, the polymer chain(s) unwind. In the case of the emulsion polymer form, the polymer concentrate “emulsifies” in the dilution water, thereby unwinding the polymer chains. Cold make-up water slows the polymer preparation by impeding the unwinding process. In the case of very cold water (330 F to 450 F) the polymer chains will unwind very slowly, thereby creating very poor floc formation upon addition to the clarifier flash mixer.
Always be sure to have room temperature water for polymer preparation tanks. Use a hot water source or even boiler steam condensate is acceptable. If this is not possible, then a portable heater should be placed in the polymer addition tank. A dramatic improvement will be observed if room temperature water is utilized for polymer additions.
OMEGA AP-2040: Powder Anionic Polymer
Prepare a 0.12% solution by adding 1 lb per every 100 gallons of make up water.
OMEGA AP-2210: Emulsion Anionic Polymer
Prepare a 0.1% solution by adding 400 milliliters per every 100 gallons of make up water
OMEGA AP-2140: Hydrated Liquid Anionic Polymer
Can be used at any desirable dilution – in cold weather a dilution to 10% with room temperature water will provide a more effective reaction.
Process water temperature and solids neutralization:
Process water temperatures are generally room temperature or above in wastewater systems. Settling problems can be observed in the bleed-in of static batches (that have dropped to a low temperature) or flow-through systems on process start-up days (example: Monday morning on first shift). The important factor to remember is:
Solids neutralization reaction time takes 50% longer - per every 100C drop in temperature.
If the wastewater clarification system is experiencing depressed temperatures, settling problems can be serious due to the lack of adequate solids neutralization/agglomeration. To overcome this condition the coagulant and/or anionic polymer dosage should be increased. The wastewater system should also be initially operated as slowly as possible - until the operating water temperature has reached normal levels.
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