Water Environmental Capacity Calculation And Allocation Based On The Optimal Reduction Model Of Pollution

Urban river is an important part of urban environment.It has the function of water source,shipping,pollutants contamination and landscape entertainment.However,many urban rivers are facing serious water pollution problems.River pollution types include point and non-point sorce pollution,sendiment release,as well as the misconnection of municipal pipe network and sewage pipeline leakage and so on.Complex river pollution types bring great pressure on the water quality of urban river.Therefore,calculation based on optimal reduction of pollution sources and water environmental capacity,has been the important means of regional water environmental management and basic policy for implementation.Taking Changzhou river network in Changzhou demonstration area as an example,pollutant optimization reduction and distribution of water environment capacity were studied in this paper.According to monitoring data of river water quality over 2013-2016,water quality is becoming better but some region is still serious.During dry season,the average values of the ammonia nitrogen,total phosphorus and COD_Cr decrease from their peaks of 6.72 mg/L,0.26 mg/L and 29.64 mg/L in 2014 to 3.86 mg/L,0.21 mg/L and 16.27 mg/L in 2016,respectively.In order to make the investigation section match the?class water quality requiremets,this paper establish response relationship between pollution sources and water quality using CE-QUAL-W2 water quality model,and the optimal reduction model of pollution was applied using the optimization method combined with linear programming modeling.Taking Changzhou river network as an example,the contribution rate and the loading reduction of pollutants were calculated.Results show that the daily reduction of the total phosphorus,ammonia nitrogen,total nitrogen and COD_Cr are 20.62kg,126.20kg,320.74kg and 982.69kg,and the percentage of the corresponding reduciton were 17.17%,37.75%,33.22%and 6.79%,respectively,which ensure to meet the objective of water quality.Combining with the characteristics of river network of integrated demonstration area of Changzhou,the TMDL values of the ammonia nitrogen,total phosphorus and COD_Cr under the designed conditions of flow and water quality were calculated.Temporal and spatial distribution of pollution were analyzed and the results of optimal reduction were calculated using CE-QUAL-W2 water quality model.The water environment calculation software for TMDL of river basin was coded using Matlab GUI,which can result the allocation and calculation of TMDL.Results show that the total phosphorus,ammonia nitrogen,total nitrogen and COD_Crr of the total maximum daily load in Xinzaogang River are 21.62 kg,168.53 kg and 3692.98 kg under the upstream condition of?class water quality and flow of 510000 m3during dry season.For the upstream condition of?class water quality and flow of1080000 m3during wet season,the total phosphorus,ammonia nitrogen,total nitrogen and COD_Cr of the total maximum daily load in Xinzaogang river are44.97 kg,329.42 kg and 7158.69 kg,respectively.The method shows the advantage of balance of total capacity control and allocation.