Coagulation behavior and floc properties of compound bioflocculant-polyaluminum chloride dual-coagulants and polymeric aluminum in low temperature surface water treatment

Xin Huang , Shenglei Sun , Baoyu Gao , Qinyan Yue , Yan Wang , Qian Li


Received April 21, 2014,Revised July 15, 2014, Accepted , Available online April 23, 2015

Volume 27,2015,Pages 215-222

This study was intended to compare coagulation behavior and floc properties of two dualcoagulants polyaluminum chloride-compound bioflocculant (PAC-CBF) (PAC dose first) and compound bioflocculant-polyaluminum chloride (CBF-PAC) (CBF dose first) with those of PAC alone in low temperature drinking water treatment. Results showed that dualcoagulants could improve DOC removal efficiency from 30% up to 34%. Moreover, CBF contributed to the increase of floc size and growth rate, especially those of PAC-CBF were almost twice bigger than those of PAC. However, dual-coagulants formed looser and weaker flocs with lower breakage factors in which fractal dimension of PAC-CBF flocs was low which indicates a looser floc structure. The floc recovery ability was in the following order: PAC-CBF > PAC alone > CBF-PAC. The flocculation mechanism of PAC was charge neutralization and enmeshment, meanwhile the negatively charged CBF added absorption and bridging effect.

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