Effect of polyaluminium chlorides overdosage on effectiveness of coagulation and filtration

PACls overdosage has negative impact on the operation and the effectiveness of coagulation and separation of post-coagulation suspensions. The results of the pilot study revealed that a sharp increase of fine particles was observed at reaching and exceeding the isoelectric point. Based on the full-scale research with PACl_1 (B = 2, 4) it was stated that these particles did not cause deterioration of standard quality parameters (turbidity, absorbance UV254, colour, TOC, CODMn) of water purified in conventional treatment. However, the particles not retained in sedimentation tanks supplied rapid filters and caused their overloading, and hence shortening of filtration cycles.