微污染氨氮对游离氯稳定性的影响及其控制措施

针对南方某湖泊水源净水厂原水氨氮在0. 25-1.00 mg/L的微污染状态下时出厂水中游离氯不稳定的问题,结合水厂处理工艺进行了不同浓度氨氮对游离氯稳定性影响的试验研究。结果表明,当原水氨氮<0.20 mg/L时,不影响出厂水游离氯的稳定;采用常规处理工艺、原水氨氮浓度在0.20-0.45 mg/L之间时,或采用常规处理+臭氧/活性炭深度处理工艺、原水氨氮在0.20-0.71 mg/L之间时,可在混凝沉淀前投加次氯酸钠,利用折点前加氯提高氨氮去除效果,使出厂水中游离氯保持稳定;采用常规处理工艺、原水氨氮>0.45 mg/L时,或采用常规处理+臭氧/活性炭深度处理工艺、原水氨氮>0.71 mg/L时,不能完全通过折点前加氯的方法降低滤后氨氮,滤后会有氯胺生成,可利用氯胺的消毒能力,以总氯控制消毒效果。

Effect and Control of Micro-polluted Ammonia Nitrogen on Stability of Free Chlorine

A waterworks in the south took source water from a lake, in which the ammonia nitrogen was about 0.25 mg/L-1.00 mg/L and caused the fluctuation of free chlorine in the effluent. The effect of ammonia nitrogen on the stability of the free chlorine was studied. The results showed that when the ammonia nitrogen of raw water was less than 0.20 mg/L, the impact on the stability of free chlorine in the effluent was minimal. When the ammonia nitrogen in raw water was between 0.20 mg/L and 0.45 mg/L or between 0.20 mg/L and 0.71 mg/L in the waterworks without or with ozone- activated carbon advanced treatment process, the removal efficiency of ammonia nitrogen was improved by adding sodium hypochlorite before coagulation and sedimentation, and the free chlorine in the effluent was stable. When the ammonia nitrogen of raw water was beyond 0.45 mg/L or 0.71 mg/L in the waterworks without or with ozone-activated carbon advanced treatment process, the ammonia nitrogen of raw water could not be completely removed by adding chlorine before coagulation and sedimentation. After the filtration, chloramine was generated, and the disinfection effect could be achieved by total chlorine including the disinfection ability of chloramine.