壳聚糖强化絮凝对出水残余铝的控制效果

Control of Residual Aluminum in Drinking Water by Enhanced Coagulation with Chitosan

国家饮用水标准(GB 5749—2006)对残余铝浓度的限制十分严格,特别是在低温时期出厂水水质难于达标,是饮用水处理过程中十分棘手的新问题。分别采用聚合氯化铝和硫酸铝作为混凝剂处理低温和常温自配水,得出两种混凝剂的最佳投量分别为20和40 mg/L;使用壳聚糖作为助凝剂分别与聚合氯化铝和硫酸铝联合使用,发现投加壳聚糖后,对浊度和CODMn的去除率提高了2.5%～10%。由于使用铝盐作为混凝剂易造成水中残余危害人体健康的溶解铝,因而进一步比较了不投加和投加不同浓度的壳聚糖后出水中残余的溶解铝浓度,研究壳聚糖的投加与水中溶解铝的关系。结果表明,无论与聚合氯化铝联用还是与硫酸铝联用,壳聚糖助凝剂的投加都能够有效地减少混凝出水中的残余溶解铝浓度。

The residual aluminum concentration in drinking water is strictly limited by the Stand- ards for Drinking Water Quality （ GB 5749 - 2006）. The difficulty of reaching the standards in low tem- perature periods is a new problem in the drinking water treatment process. Polyaluminium chloride and a- luminum sulfate were respectively used as coagulants to treat synthetic low temperature and room tempera- ture waters. The best dosages of polyaluminium chloride and aluminum sulfate were 20 mg/L and 40 mg/L respectively. The removal rates of turbidity and CODMn were increased by 2.5% to 10% when chitosan was applied as a coagulant aid. Residual dissolved aluminum harmful to human body appeared when alu- minum salts were applied as coagulants. The residual dissolved aluminum concentration in treated water by coagulation with and without chitosan addition was compared, and the relationship between the dosage of chitosan and the residual dissolved aluminum concentration was studied. The results showed that the addition of chitosan in a polyaluminium chloride or aluminum sulfate treatment could reduce the residual dissolved aluminum concentration in treated water.