Analysis Of Source Water Quality In Yancheng City And Influence Of Yanlong Lake Ecological Project On Raw Water Quality

In recent years,various water source area ecological projects have been built in many cities with the deterioration of source water quality and the frequent occurrence of sudden water pollution accidents.Although a lot of studies on conventional indicators removal by water source area ecological projects have been reported,researches about influence of water source area ecological projects on disinfection by-products precursors are reported fewly.Based on the investigation of the source water quality,the changes of water quality and distribution of pollutants of the Yanlong Lake Ecological Project were analyzed.The influence of the Yanlong Lake Ecological Project on raw water quality in different seasons was studied by combining small-scale trials and actual project investigations.Furthermore,influences of the water source area ecological project system on disinfection by-products precursors in micro-polluted raw water were investigated by a bench plant.Finally,formation of disinfection by-products from the chlorination of aquatic organism metabolite was studied by single factor experiment.Main conclusions were listed as following:?1?The raw water quality of Yanlong Lake was superior to that of Tongyuhe.The characteristic qualities of Yanlong Lake and Tongyu River were serious organic pollution,higher concentrations of nitrogen and phosphorus and obvious seasonal changes.COD_Mnn exceeded Standard?of ground water criterion?GB3838-2002?in several months,and the concentrations of TN exceeded Standard?of ground water criterion for all the years.Besides,several water quality indicators in summer were generally higher than other seasons.?2?The Yanlong Lake Ecological Project was generally in good condition.Several indicators of the water came from Mangshe River were improved after pretreated by the Yanlong Lake Ecological Project.NH₄⁺-N,COD_Mn,TP,and Fe of the effluent of the Yanlong Lake Ecological Project reached Stangard III of ground water criterion.The removal rates of NH₄⁺-N,TN,and Fe in different seasons were summer>autumn>spring>winter,and the removal rates of turbidity,COD_Mn,and TP were summer>spring>autumn>winter.?3?With hydraulic retention time decreasing,pollutants removal rate of the water source area ecological project system continued to reduce.And the removal rates of pollutants were positively correlated with water temperature.It was found that the DOM of the water source area ecological project system was mainly composed by the organic fraction with a molecular weight of 3¹0 kDa and hydrophobic fraction.The concentrations of DOC,UV₂₅₄,THMFP and HAAFP of a molecular weight of<3 kDa decreased along the system while that of a molecular weight of>3 kDa increased along the system.The concentrations of DOC,UV₂₅₄,THMFP and HAAFP of hydrophobic fraction increased along the system totally while that of transphilic fraction and hydrophilic fraction had various changes in different seasons.Fuethermore,the concentrations of TTHMFP and THAAFP of effluent increased by 26.58?g/L,8.07?g/L,53.70?g/L and 32.00?g/L,10.55?g/L,80.65?g/L respectively in autumn,winter and spring comparing with influent of the system,indicating that water source area ecological engineering system led to the increase of disinfection by-product precursors.?4?Root exudates of Typha orientalis,root exudates of Zizania latifolia and faeces of silver carp reacted with chlorine to form DCAA,TCAA,TCM and DCAN during disinfection.And the four disinfection by-products concentrations increased with longer reaction time,higher chlorine dosage and higher temperature.With pH increasing,the concentrations of TCM and DCAA gradually increased while that of DCAN and TCAA initially increased and then decreased.