Study On The Influence Of Overflow Pollution And Its Control On Waterway Water Environment

Navigable waterways are an important carrier and lifeline of the shipping industry.In recent years,with the new development of the“Belt and Road”,which has boosted the vigorous development of the inland waterway shipping industry,the pollution of the waterway environment has gradually emerged.The Jialing River Channel is an important part of the Golden Waterway of the Yangtze River.The water environment pollution of the channel is mainly composed of ship sewage,channel dredging,and sewage entering the river.The highest proportion is the transportation of land-source pollutants into the river.Overflowing sewage is one such pollution source.Combining the current ecological waterway construction and the prerequisite of the protection of the Yangtze River,attention should be paid to the prevention and control of the water environment of the Jialing River channel,and the targeted prevention and control of overflow pollution along the channel can better realize the sustainable operation of the Jialing River channel.The thesis is based on the overflow port along the Jialing River in Chongqing.First,through field monitoring and sampling detection,the water quality characteristics and related laws of the overflow pollution along the channel are analyzed and discussed.Then,according to the obtained overflow sewage concentration and related water quality indicators,the hydrodynamic and water quality modules of MIKE21 are used for simulation calculation,and the pollution zone change of the coastal overflow sewage in the water environment of the channel is obtained.Finally,in view of the overflow pollution problem along the channel,a functional zoning bioretention integrated device in series with physicochemical phosphorus removal measures was designed to deal with overflow pollution.The effluent can achieve good treatment effects,which is the treatment of this type of overflow pollution in the later stage.Provide certain data support.The main conclusions are as follows（1）The overflow pollution along the channel is mainly composed of domestic sewage,rainwater and surface runoff.The change of water quality in sunny and dry currents is affected by the changes in the amount of water used in human flow,and overflow pollution on rainy days shows a certain delay.The pollution indicators of overflow water quality are mainly ammonia nitrogen,total phosphorus,chemical oxygen demand and suspended solids.Compared with the flooded sewage on a rainy day,the COD is 1.1 times that of a sunny day and the SS is 8.5 times that of a sunny day.TP and NH₃-N are 0.47 times and 0.35 times that of sunny days,respectively.With the increase of rainfall,the concentration of the three pollutants of SS,NH₃-N and TP in the spilled pollutants on rainy days increased significantly.However,the COD concentration decreased significantly with the increase of rainfall.（2）According to the MIKE21 hydrodynamic-convection diffusion water quality model established under the water environment conditions of the Jialing River channel,the attenuation coefficient K values of TP and NH₃-N in the rainy season are 0.364/d and0.108/d,respectively.After continuous input of pollutants for 1 hour,the area of the pollution zone formed by the contours of the low concentration of ammonia nitrogen and total phosphorus under the three working conditions is heavy rain>moderate rain>light rain.As the rainfall intensity increases,the time it takes for pollutants such as ammonia nitrogen and total phosphorus to diffuse in the water to the same quality control point is shortened.（3）The best operating conditions of the integrated device for overflow pollution along the channel are the hydraulic retention time of 8h,the nitrification liquid reflux ratio of 100%,and the effluent can reach a certain water quality standard.During the intermittent water intake of the integrated device,water must be filled again every 15days or so.Compared with the overflow raw water,the diffusion and decay time of pollutants such as NH₃-N and TP（heavy rain）are shortened by 19-20d and 0.56d respectively in the integrated effluent.（4）Intensified dephosphorization experiment,using polymeric polyaluminum ferric chloride as the coagulant,under the best conditions,the dosage is 60mg/L,the rapid stirring time is 2min,and the slow stirring time is 15min.The total phosphorus in the effluent reaches the later rainwater standard of Chongqing City and the third-grade surface water standard.Compared with the integrated effluent,light rain,moderate rain,heavy rain and other overflowing raw water,the total phosphorus diffusion decay time is shortened by 4.68d,4.61d,4.39d,5.25d,which has a better water quality improvement effect.