Too much polymer? Signs of overdosing and how to fix it
More polyelectrolyte is not always better. How to spot an overdose in the clarifier and on the press, and how to bring the dose back.
Why plants overdose
When the clarifier looks poor, the first instinct is to turn up the polymer pump. Sometimes the real cause lies elsewhere, such as pH, coagulant or mixing, and extra polymer only adds cost and new problems.
Signs in the clarifier
The water above the flocs turns cloudy again after first improving. Fine particles carry over even though the flocs look large. The treated water feels slippery or viscous. With cationic grades, too much can reverse the charge on particles so that they push apart again.
Signs on the press or filter
Sludge turns sticky and smears on the belt, filter cloths blind quickly, and filtrate turns slimy. Downstream sand filters and membranes may foul faster.
Find the right point
Run a jar test across a range of doses, from below today's setting to above it. Results improve as the dose rises, level off, and then get worse. The best dose sits at the start of that flat part, not at the top.
Bring it back in steps
Lower the dose by about 10 to 20 percent at a time and give the plant a few hours to settle between changes. Check the coagulant dose and pH at the same time; they are often the real cause.
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Read →Not sure which grade suits your water?
Send us a one-litre sample or describe your process. We test it in our lab free of charge and recommend a grade and starting dose, and quote within 1 business hour.