再生水厂退水对受纳水体水质和水生态的影响—以清河为例

Impact of the effluent of wastewater treatment plants on the water quality and ecology in receiving water bodies—A case study of Qing River

为明确再生水水厂退水对水体水质和水生态的影响,本研究分别于2010年和2020年对清河再生水厂退水口及其上下游开展了水质和水生态调查.实地调查结果表明,与2010年相比,2020年清河再生水厂退水口河段平均pH由6.44上升为8.38,整体呈弱碱性;水质类别从劣V3类提升至地表水IV类,水环境质量明显改善;主要阳离子由Na+为主转向以Ca^(2+)为主,阴离子Cl-、SO42-等浓度降幅分别为88.85%和93.75%;2020年该河段水化学类型为Ca-HCO_(3)型,盐渍化趋势明显.水生态状况转变与水质转变趋势一致,主要浮游植物种类由蓝藻门(Cyanophyta)向硅藻门(Bacillariophyta)转变,浮游动物以原生动物、轮虫和枝角类为主,再生水厂下游浮游生物群落多样性指数H’升高,浮游生物群落结构更为复杂.统计分析结果表明,COD、NO_(3)^(-)-N等含氮营养物和Ca^(2+)、HCO_(3)^(-)、Cl-等阴阳离子是影响清河再生水厂退水口河段浮游生物主要类群密度和群落多样性的主要因素.

To clarify the impact of wastewater treatment plants(WWTPs)effluent on water quality and ecology condition,this study investigated the water quality and aquatic ecological conditions of the Qing River WWTP effluent and its upstream and downstream in 2010 and 2020.Results showed that compared with 2010,the average of pH increased from 6.44 to 8.38,with an overall weak alkalinity in 2020.The quality of water environment was improved from Class V3 to Class IV(Surface Water Quality Standard of China(GB 3838-2002)),the water quality has improved significantly.The main cations changed from Na+to Ca^(2+),and the anions concentrations of Cl-and SO42-decreased by 88.85%and 93.75%,respectively.The water chemistry type in 2020 was Ca-HCO_(3) type with obvious salinization trend.The change of water ecological condition was consistent with the trend of water quality,the main phytoplankton community changed from Cyanophyta to Bacillariophyta,the zooplankton was dominated by protozoa,rotifers,and branchiopods.The plankton community diversity index H’increased in the downstream of the RWTP,and the community structure of plankton was more complex.Statistical analysis results indicated that COD,nitrogenous nutrients such as NO_(3)^(-)-N,anions,and cations such as Ca^(2+),HCO_(3)^(-)and Cl-were the main factors influencing the abundance and community diversity of the plankton main taxa in the river section of the Qing River WWTP.