Evaluation of coagulant/polymer combinations on VEAS wastewater

Abstract

Three coagulant/polymer combinations from two metal salts (M14, M31), two cationic polymers (A25, A27) and one anionic polymer (P6) are evaluated on VEAS wastewater for their flocculating, sedimentating and sludge characterestics. A continous, semi-pilot scale experimental apparatus is used. Cationic polymers do not significantly influence on the overflow rates. Anionic polymers increase the overflow rates by two to five times at dosages 0.3 mg/l and 1 mg/l, respectively. A flocculation period of 3 min between metal salt and cationic polymer, 4 min (and also 7 min) between cationic and anionic polymers, and 2 min between metal salt and anionic polymer are selected best among the tested conditions. The combination of M14, A27 and P6 are considered to give the best overall performance.