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 PAC1-1 (B = 2,4) it was stated that these particles did not cause deterioration of standard quality parameters (turbidity, absorbance UV₂₅₄, colour, TOC, COD_Mn) 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.