Through coagulation experiments, trace phosphorus removal efficiency in water of three coagulants as poly aluminum chloride(PAC), pely ferric chloride(PFC),poly aluminum-ferric chloride(PAFC) and the variation of it with the change of pH were investigated. The effects of polyacrylamide(PAM) and permanganate composite chemicals (PPC) on improving phosphorus removal were also studied. The results showed that total phosphorus removal efficiency by PAC was evidently higher than those by the other two coagulatin...