水质净化厂尾水生态补水对城市溪流水质及富营养化风险的影响OA

This study takes stream A in a southeastern coast city as an example to explore the impact of ecological water replenishment of the treated tail water on the stream's water quality and eutrophication risk in a water purifi-cation plant.The water quality indicators such as pH,temperature,salinity,dissolved oxygen,chemical oxygen demand(CODCr),5-day biochemical oxygen demand(BOD5),ammonia nitrogen,total nitrogen(TN),total phos-phorus(TP),as well as Chlorophyll a were monitored at 4 sampling points of the upstream of stream A,tail water outlet,ecological replenishment discharge outlet and the downstream of stream A,and the effects of water replen-ishment on the key water quality indicators of stream A were analyzed.Research indicates that ecological water re-plenishment has a minor impact on the pH,temperature,salinity,and dissolved oxygen levels of stream A,but can dilute all the organic matter,ammonia nitrogen,TN and TP concentration.Nevertheless,the ammonia nitrogen and TP concentration in the downstream of the replenishment section rebounds to 2.5 mg/L,0.38 mg/L,respectively,indicating a potential risk of secondary pollution.According to the Nemerow water quality index evaluation,stream A is rated as the heavily polluted level with the main restrictive indicator of TN;Stream A is in a state of mild eu-trophication by the comprehensive trophic index evaluation model,and ecological replenishment has no adverse af-fect on water quality.Therefore,measures should be taken to control the total nitrogen levels in the effluent of water purification plant to further improve the water environment and ecological conditions of stream A.