Analysis and selection of powdered zeolite dosing point in enhanced coagulation-sedimentation for treating micro ammonia polluted raw water

摘要

Ammonia pollution occurs frequently in urban water supply systems. Zeolite is a kind of promising adsorbent for ammonium removal. In an actual running water work, different zeolite dosing points should have various influences on the effluent, which, however, draws insufficient attention. This paper focuses on the analysis and selection of powdered zeolite (PZ) dosing point in enhanced coagulation-sedimentation for treating micro ammonia polluted raw water. We investigate the variations of effluent ammonium concentration, turbidity, CODMn and UV254 of the coagulation-sedimentation schemes which have different PZ dosing points and we also analyse the relevant causes. PZ dosing can induce extra turbidity and the existing turbidity can inhibit ammonium removal to certain extent. In CODMn and UV254 removal process, both synergistic effect and antagonistic effect exist, and PZ dosing point determines which effect it is. PZ dosing has a significant synergistic effect on promoting poly aluminium chloride to remove ammonium. Among the four PZ dosing points, i.e. the suction well, the pipeline mixer, the early step of coagulation and the middle step of coagulation, (1) when turbidity, CODMn and UV254 need to be removed effectively and simultaneously, the suction well is the best PZ dosing point, and the PZ dosage must exceed 1g/L for removing CODMn; (2) when it is required that ammonium be removed in priority, the early step of coagulation is the optimal point.