Simulation Study Of Influence Of Reclaimed Water On Water Quality In Typical River Of Shenzhen City

This thesis investigated the variation of water quality in Shawan River and Shenzhen River,and the effects of reclaimed water on the water body of two rivers.Field investigation was in terms of the distribution and variation of turbidity,DO,organics,nitrogen,phosphorus,iron/manganese ions and typical odor compounds in the upper stream of Shenzhen River and the lower stream of Shawan River.The effects of reclaimed water on the water quality of Shawan River and Shenzhen River was assessed.Three different types of reclaimed water including fiber filteration effluent,hollow fiber membrane ultrafiltration effluent and membrane bioreactor effluent,were studied with laboratory simulation method.The interactions among water quality parameters and the complex relationship between overlying water and sediment were analyzed.These would provide the scientific basis in improving reclaimed water quality and controlling the black-odor phenomenon of river.In both Shawan River and Shenzhen River,total nitrogen reached over 12 mg/L,the concentrations of Geosmin(GSM),Dimethyltrisulfide(DMTS),2-methylisoborneol(2-MIB)and β-ionone were beyond the olfactory thresholds.Dimethyltrisulfide were more than 30 ng/L.The DO in Shawan River was 5 mg/L on average which was in aerobic condition with average DO concentration was under 2 mg/L.The water quality of both Shawan River and Shenzhen River deteriorated gradually.Related concentrations of pollutants and DO fluctuated seasonally,better water quality presented in rainy season.In the sediment of Shenzhen River or Shawan River,organic contents were 2.92%and 1.57%,respectively,TN were 0.88 g/kg and 0.67 g/kg,TP were 1.56 g/kg and 1.15g/kg.The release amounts of nitrogen,phosphorus and the oxygen consumption from sediments of Shenzhen River were about 2 times higher than Shawan River.While maintaining DO at 5 mg/L can promoted the degradation rates of organic matter and total nitrogen in water significantly.It would be beneficial to increase the concentration of DO in the water body when keeping water flowing,which can also effectively inhibit the release of pollutants from sediment.It was found that there was little difference in water quality among three types of reclaimed water.Under static condition,the DO concentrations in water reduced below2 mg/L,while the concentrations of odor compound increased significantly beyond the olfactory thresholds which would lead to black-odor phenomenon.Large amount of ammonia,phosphorus and iron ions released from sediment,which would influence the quality of overlying water significantly.Some complex dynamic reactions between iron ions and phosphate were observed,which may lead to large fluctuations in the concentration of iron ion.There were corresponding relationships between ammonia,nitrate and dissolved oxygen,which seriously affect the TN concentration.The quality of reclaimed water obtained from conventional treatment was not good enough to eliminate the black-odor phenomenon in river,sediment also had an important influence on water quality.It is important to understand the relationship between the river water and sediment to control the black and odor in river.