铁铝复配混凝剂处理低温低浊水

针对北京某水库水在冬季呈现低温低浊特性,以此为原水的某水厂在该期间常会出现出水余铝超标现象的问题,通过烧杯实验研究不同投药量下聚合氯化铝(PAC)以及它与三氯化铁(FeCl3)不同复配比形成混凝剂对冬季北京某水库水的处理效果。结果表明,复配药剂存在最佳的Fe/Al摩尔复配比为1/5,此时余铝、有机物去除效果较其他配比混凝剂高。在此配比下,当PAC投药量为0.03 mmol/L时,水中残余铝量取得最低值0.0063 mg/L。相同投药量复配药剂的浊度去除效果比单独使用PAC的浊度去除效果略弱。当投药量为0.06 mmol/L时,Fe/Al摩尔比为1/5的复配混凝剂,能使浊度降至0.4 NTU左右。此外,复配药剂的投药量小,投药范围更宽,易于实际投药操作;同时复配药剂还适于常温及偏中性水源水的处理。规模为5 m3/h中试实验也证明,采用铁铝复配混凝剂连续运行,可获得良好的浊度、余铝去除效果。

Coagulation of a low temperature and turbidity raw source water by Fe-Al composite coagulants

The water turbidity and temperature of a reservoir in Beijing are low in winter, and this results in excessive residual aluminum in finished water during this period of time. To solve this problem, the performances of polyaluminium chloride (PAC) and new coagulants consisting of PAC and ferric chloride (FeCl₃) were studied by jar tests. The results show that the best coagulation performance was achieved at a molar ratio of 1/5 for Fe/Al, with the lowest residual aluminum and the highest organic matter removal efficiencies. At this ratio, at the dosage of PAC 0.03 mmol/L, the lowest residual aluminum was at a very low concentration of 0.0063 mg/L. The turbidity removal efficiencies of iron and aluminum composite coagulants were lower than those of PAC at the same dosage. When the dosage of the composite coagulant with a Fe/Al molar ratio of 1/5 was at 0.06 mmol/L, the treated water turbidity could be decreased to 0.4 NTU. In addition, the effective dosage cover range, thus easy for coagulant control in treatment plants. It is also suitable for treating source waters with normal water temperature with a mild alkalinity. Pilot plant tests with a capacity of 5 m³/h demonstrated the effectiveness of the Fe-Al composite coagulant after long time and continuous run.