高锰酸钾与氯胺联合预氧化强化低温低浊水处理

Treatment of low temperature and low turbidity raw water enhanced by combined preoxidation process of potassium permanganate and chloramine

为了探讨对低温、低浊水更为有效的预氧化技术,通过小试考察了高锰酸钾与氯胺联合预氧化工艺在助凝、助滤、去除有机物及减少氯化消毒副产物方面的效能。结果表明:与单独氯胺预氧化工艺相比,高锰酸钾与氯胺联合预氧化具有明显的强化助凝和助滤作用,在最佳质量浓度时,可使沉后及滤后水浊度去除率分别达到94%和98%以上;并具有明显地降低沉后有机污染指标的效能,使沉后水中UV254和CODMn指标分别降低23%和32%;还能够有效地控制THMs的生成,KMnO4质量浓度为2mg/L时,THMs去除率达85.2%,同时还可去除CHBr2Cl、CHBr3两种副产物。因此高锰酸钾与氯胺联合预氧化是一种对低温低浊水十分有效的水处理技术。

Problem of low temperature and low turbidity raw water treatment is always the technical difficulty of surface water treatment plants in northern China. Several aspects of effects on enhanced coagulation, enhanced filtration, organic pollutants removal and reduction of chlorine disinfection byproducts with combined preoxidation of potassium permanganate and chloramine are investigated with experimental water sample of Yellow River during winter, in order to approach more effective preoxidation treatment techniques of low temperature and low turbidity raw water. Turbidity of raw water is 10.7 NTU, water temperature is 4 ℃, UV254 value is 0.122 units, pH value is 8.08, ammonia is 0.24 mg/L and CODMn is 4.24 mg/L during experiments. Experimental methods are as follows： Six-multiple agitator of model JJ-4 is applied during beaker mixing experiments. Water samples are moved into six beakers with 1 500 mL during experiments. A certain dosage of ammonia is dosed, and certain dosages of potassium permanganate and chlorine are dosed at same time. Reactions are carried out at mixing condition of 500 r/min for 20 min. Ferric chloride is added at mixing condition of 200 r/min for 1 min, and then at stirring condition of 100 r/min for 18 min. After settled for 30 min. Supernatant of settled water sample is taken and monitored, and water sample filtered with qualitative filter paper is monitored too. Results show that effects of enhanced coagulation and filtration are improved by the combined preoxidation process, compared with individual chloramine preoxidation process. Turbidity of settled water is reduced to 1 NTU below with turbidity removal rate of 94% above, while potassium permanganate dosage is 1.0 mg/L only. Turbidity of filtered water is reduced to 0.115 NTU with turbidity removal rate of 98.5 % above, while potassium permanganate dosage is 2.0 mg/L and chloramine dosage is 6.0 mg/L. Good efficiency on reduction of organic pollutants is obtained by the combined preoxidation process. UV254 and CODMn of settled water are decreased by 23% and 32% respectively, while potassium permanganate dosage is 2.0 mg/L and chloramine dosage is 6.0 mg/L. Trihalomathanes formation can be controlled effectively by the combined preoxidation process with 85.2% removal rate of trihalomathanes at 2.0 mg/L dosage of potassium permanganate, and byproducts of CHBr2Cl and CHBr3 can also be removed. Therefore, the combined preoxidation of potassium permanganate and chloramine is an effective treatment process for low temperature and low turbidity raw water.