[Emergent treatment process for raw water polluted by heavy metal Pb (II)]

Based on two common coagulants-polyferric sulfate (PFS) and polyaluminum chloride (PACl), some measurements and processes in the background of Pb (II) concentration sudden increase in water were studied. The removal efficiency of Pb(II) was compared between PAC and diatomite absorption with coagulation. The effect of coagulant dosage, initial concentration of Pb(II), pH value and KMnO4 preoxidation on coagulation were investigated. The results showed that using PFS was better than PACl for the removal of Pb(II). The regulating pH value up to 9 could improve the removal efficiency of Pb(II) up to 95% by coagulation under the optimum dosage of coagulant PFS of 10 mg/L. KMnO4 preoxidation could improve the removal efficacy of Pb(II) by coagulation of PACl only. The Pb(II) removal efficiency of PAC and diatomite absorption with coagulation were almost equal. Pb(II) concentration could be lowered from 402 microg/L to below 10 microg/L under the condition that dosages of PAC or diatomite were 10 mg/L or 25 mg/L by using PFS. The same effect could be got under the condition that dosages of PAC or diatomite were 20 mg/L or 50 mg/L by using PACl. KMnO4 and diatomite are dosed at the same time would weaken their function each other. Therefore, diatomite adsorption coupled with coagulation is the simplest and most effective method for removing Pb(II).