The Performance Of Enhanced Coagulation Combining Polyaluminium Chloride With Variable Charge Soil

Drinking water standard has become more and more stringent with the improving of people’s living level. Traditional coagulation has great limitations on reaction conditions, water quality requirements and coagulation efficiencies for rising the quality and safety of drinking water. An efficient, economical and safety method of water treatment is urgently needed in terms of slightly polluted raw water.The feasibility and effectiveness of treating pollutants in slightly polluted raw water by enhanced coagulation combained variable charge soil of South China with polyaluminum chloride(PAC) was investigated. The properties of flocs and removal efficiencies of turbidity, phenol, aniline, algae and heavy metals(Cu2+, Zn2+ and Pb2+) were used to evaluate the coagulation performance. The main results are as follows:(1) The effectiveness of enhanced coagulation combined variable charge soil and PAC on reducing turbidity was researched. Results showed that variable charge soil can increase the removal efficiency of turbidity. Charge-neutralization and physical entrapment of colloids effect played significant roles on PAC coagulation, increasing the density of flocs and improving the performance of floc settling. When variable charge soil was used in conjunction with PAC, the concentrations of suspended particles in water were went up, thereby the efficiencies of effective collisions between particles as well as settling rate were increased, forming bigger and denser flocs than those generated by PAC alone.(2) Effects on the removal efficiency of turbidity by enhanced coagulation were investigated. Results suggested that enhanced coagulation is more suitable for the neutral to slightly alkaline conditions. In addition, sensitivity of enhanced coagulation to initial turbidity, organic matter and hydraulic condition is less than that of coagulation by PAC alone, which reflected the superiority of the former.(3) The effectiveness of enhanced coagulation on removal of representative pollutants in water was studied. As a coagulant aid, variable charge soil has strong effect on treating aniline, and algae, whereas has weak effect on reducing phenol and heavy metal ions like Cu2+, Zn2+ and Pb2+ in water.Based on the research results above, enhance coagulation combining variable charge soil and PAC was supposed to be effectively applied for purification of slightly polluted raw water.