Study On The Effect Of Multi-level Disinfection On DBPs And Biological Stability Of The Water In Urban-rural Integrated Water Supply Network

As of 2018,Jiangsu Province has almost achieved the overall coverage of urban and rural regional water supply towns.The traditional single-stage disinfection method cannot guarantee the continuous stability of the water quality of the town and village pipeline network under the conditions of long-distance and long-age water transmission and distribution,the residual chlorine and the appearance of microbiological examination may happened,so it is necessary to study multi-level disinfection technology to further ensure the stability of water of the urban and rural integrated regional water supply network.The goal for this research is the effect of multi-level disinfection on the generation of disinfection by-products and the biological stability of water quality in the urban-rural water distribution network has examined,by optimizing the multi-level disinfection strategy to ensure the biostability of the water quality at the end of the township water supply network.the water quality of urban and rural water supply networks in typical cities with different raw waters and different treatment processes in the province was investigated,the changes in the water quality of the network,investigate the impact of multi-level disinfection on the water quality of the network,and focus on the by-products and water quality biological stability changes was examined.Meanwhile,the multi-level disinfection optimization strategy is studied to simulate the actual water supply network based on the mathematical model of the network.In winter and summer,the water quality of the representative urban and rural water supply network of the three major river systems（Yangtze River,Huaihe River,Taihu Lake）in Jiangsu Province was followed up.The water quality of the pipe network with Yangtze River water as the raw water is better than those of Taihu Lake and Huaihe River.Among the water quality indicators of the three major river basins,the turbidity showed a tendency to increase with the extension of the pipeline.The residual chlorine in the end of the investigation pipelines in the Yangtze and Huaihe river basins did not meet the standard and the total colony inspection showed signs.Trichloromethane in the pipeline network showed a trend of rising at first,then stabilized and then decreased.In addition,the biodegradable dissolved organic carbon（BDOC）and assimitable organic carbon（AOC）of the water in the pipe network both showed a trend of increasing first and then decreasing with the extension of the pipeline.For the water purification plant,the content of dissolved organic carbon（DOC）in the factory water is substantially reduced after the advanced treatment process,and the production of disinfection by-products（DBPs）is reduced,indicating that the use of the advanced treatment process can help improve the quality of the factory water.In the township village water supply pipeline network with multi-stage disinfection,as the pipeline is extended,the COD_Mn and UV₂₅₄ in the pipeline water gradually decreased,the content of trihalomethanes（THMs）rised first and then remained stable,while the haloacetic acid（HAAs）the content increaseed first and then decreased.The BDOC and AOC in the water of the multi-stage disinfection pipeline along the pipeline network increased first and then decreased,and the content along the pipeline is higher than that of factory water.The detection frequency of microorganisms in the water along the pipeline network was low,and the residual chlorine content in the distal section water meets the standard requirements.However,there are also risks of increased disinfection by-products and deterioration of the biostability of the pipe network water.In addition,before and after multi-stage disinfection,the characteristics of organic matter in the pipe network water changed,and the proportion of small molecular organic matter（<1 k Da）increased.The proportion of small-molecule organics（<1 k Da）increased.The results of three-dimensional fluorescence spectroscopy showed that the fluorescence intensity of all five areas decreased after multi-stage disinfection.The relative fluorescence intensity of zoneⅢwith fulvic acid as the representative organic substance decreased the most,indicating that within this area.There are many active substances that can react with chlorine.Namely,this kind of organic matter substantially contributes to the generation of disinfection by-products in the multi-stage disinfection pipe network water,which needs to be controlled.Using EPANET2.0 software to establish the hydraulic water quality model of the actual water supply network in town Y,adjusted the initial Hyzen-William C value of the pipeline to check the hydraulic model,and the error between the simulated value and the measured value of the control node pressure was within 0.02 MPa.Based on accurate hydraulic model,a water quality model of residual chlorine attenuation and trihalomethane generation in the pipe network is further constructed,and the error between the simulated value and the measured value of the water quality monitoring point was controlled within 30%.By simulated the adjustment of multi-stage disinfection schemes,the goal was to ensure that the residual chlorine at the end of the pipe network meets the standard and the formation of trihalomethanes is suppressed.Optimized the location setting of multi-level disinfection and the dosage of graded disinfectant,and put forward the best multi-level disinfection scheme suitable for the water supply network of Y town.