不同河道型微污染水源预处理工程水质净化效能及水质稳定性评价

Evaluation of water purification efficiency and stability of water quality in micro-polluted water sources pretreatment projects with different types of river

为探究兼备水质净化及应急蓄水功能的两种不同微污染饮用水源预处理工程夏季高温期水质净化效果及浮游植物水华爆发风险,于2019年高温期(7-8月)对盐龙湖工程(由预处理单元、人工湿地净化单元及深度净化单元构成)和通榆河工程(由生物接触氧化池,高密度沉淀池及蓄水库构成)各处理单元出水水质及浮游植物群落进行监测分析.结果表明:①夏季蟒蛇河及通榆河水质较差,主要表现为浊度、营养盐和有机物浓度高,DO含量低.两种预处理工程都具有较高的除浊、降低营养盐和提升DO效率,其中,通榆河工程中分别高达89.01%、95.13%和227.00%,净化效能优于盐龙湖工程(分别高达50.55%、38.33%和144.00%);②夏季高温期间,盐龙湖工程及通榆河工程蓄水单元总浮游植物及蓝藻细胞密度分别为1.71×10^6 ind·L^-1和1.28×10^6 ind·L^-1,2.23×10^6 ind·L^-1和0.96×10^6 cells·L^-1.两预处理工程蓄水单元藻类构成都以蓝藻为主,其中通榆河蓄水单元藻细胞密度较高,盐龙湖蓄水单元蓝藻细胞密度所占比例较高,结合蓄水单元水质变化(浊度降低,水下光照强度的增加),两预处理工程蓄水单元仍都具有蓝藻水华的风险;③两种预处理工程中都划分出17个FG和6个MBFG.盐龙湖工程中优势FG为:B、D、P、TC、J、Lo、W1和W2;优势MBFG为:GroupⅢ、GroupⅣ、GroupⅤ、GroupⅥ和GroupⅦ;通榆河工程中优势FG为:B、D、P、Lo、M和W1;优势MBFG为:GroupⅣ、GroupⅤ、GroupⅥ和GroupⅦ.两种功能群都能很好地响应预处理工程中水环境的变化,而MBFG的生境响应性更强,影响优势MBFG的主要环境因子为浊度、电导率、营养盐和CODMn.因此,在夏季高温期,需优化预处理工程的工艺与运行,调控关键环境因子,以期能够控制浮游植物大量繁殖和维持水质稳定.

To explore the water quality purification efficiency and algal blooms risk of two different micro-polluted drinking water source pretreatment projects(which have both water purification and emergency water storage functions) during high temperature period, the effluent water quality and phytoplankton community of each treatment unit along the Yanlong Lake Project(consisting of biological contact oxidation, high-density sedimentation and embedded reservoir) were monitored and analyzed during the high temperature period(July—August) in 2019. The results showed that: ① The water quality of both Mangshe River and Tongyu River were poor in summer with high turbidity, high density of nutrients and organic matter, and low dissolved oxygen. Both of pretreatment projects showed high efficiency in removing turbidity, reducing nutrients, and increasing dissolved oxygen content. It′s worth noting that the purification efficiency of Tongyu River Project(89.01%, 95.13% and 227.00% for removing turbidity, reducing nutrients and increasing dissolved oxygen content respectively) were higher than those in Yanlong Lake Project(50.55%, 38.33% and 144.00% for removing turbidity, reducing nutrients and increasing dissolved oxygen content respectively);② The average cells density of total phytoplankton and cyanobacteria in water storage units of Yanlong Lake Project and Tongyu River Project during summer were 1.71×10^6 ind·L^-1, 1.28×10^6 ind·L^-1, 2.23×10^6 ind·L^-1 and 0.96×10^6 cells·L^-1 respectively. Cyanobacteria were the dominant species in the water storage units of the two Projects. In addition, the cell density of phytoplankton was higher in the storage units of Tongyu River Project, while a higher proportion of cyanobacteria was observed in water storage units of Yanlong Lake Project. Combined with the water quality changes of the water storage units(turbidity decreased, underwater light intensity increased), the two pre-treatment water storage units still have the risk of cyanobacteria bloom. ③ There were 17 functional groups(FGs) and 6 morphology-based functional groups(MBFGs) in both projects. The dominant FGs in Yanlong Lake Project were: B, D, P, TC, J, Lo, W1, and W2 and the dominant MBFGs were: GroupⅢ, Ⅳ, Ⅴ, Ⅵ, and Ⅶ. The dominant FGs in Tongyu River Project were: B, D, P, Lo, M, and W1;the dominant MBFGs were: Group IV, V, VI, and Ⅶ. Both FGs could respond well to the changes of the water environment in two pretreatment projects, while the MBFGs had stronger habitat responsiveness. The main environmental factors affecting the dominant MBFGs were turbidity, conductivity, nutrients and permanganate index. Therefore, during the summer high temperature period, it is necessary to optimize the process and operation of the pretreatment project and regulate key environmental factors in order to control the reproduction r of phytoplankton and maintain stable water quality.