用改性壳聚糖对城市未达标排放污水进行再处理

采用传统活性污泥法处理城市污水，其出水CODcr、色度、SS等指标往往大于一级排放标准。采用一种新型高效的天然高分子混凝剂一改性壳聚糖VCG对城市污水用于传统活性污泥法处理后的再处理，可有效地除掉余下的污染物质。结果表明，在改性壳聚糖VCG投加量为150mg/L,pH值为5．5，沉降时间为60min 的条件下，混凝效果最佳，浊度去除率可达到92％左右，色度去除率可达88％左右，CODcr去除率可达到78％左右，悬浮物SS去除率可达91％左右，水质完全可以加收利用。

Retreatment of City Sewage with Large Discharge Standard by Using Unchanged Chitosan

Using traditional activity sludge treatment,the content of COD cr ,color and SS of city sewage are often larger than discharge standard.We apply a new natural high efficiency of unchanged chitosan(VCG)to retreatment of city sewage,which was used after traditional activity sludge treatment.In this case, the city sewage can be purified effectively.The result shows that,under the condition of the addition of unchanged chitiosan(VCG) 150mg/L ,pH 5.5 and setting time 60 min,we can achieve the best outcome:the removal rate of turbidity is about 92%,the removal rate of color is about 88%,the removal rate of COD cr is about 78% and the removal rate of SS is about 91%.The water can be recovered as a byproduct.