Polyacrylamide-based polymers are commonly used as coagulant aids in water treatment, but there is some concern about their potential toxicity. This work investigated a novel alternative, HydrexTM 3841 activated starch polymer, as a coagulant aid for alum to treat low turbidity source water at pilot scale using in-line filtration. Compared to two typical polyacrylamide-based polymers, Magnafloc® LT22S and Superfloc® A-100, at an alum dose of 0.95 mg Al/L, activated starch could reach a similarly optimal unit filter run volume (∼116 m3/m2), while the required dose (0.48 mg/L) was approximately 2–10 times higher than those for the other two types of polymers. Since polymer cost has been reported to be a minimal proportion of the total chemical cost at a water treatment plant, activated starch may be a promising alternative to polyacrylamide.

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