南通污水排海工程排放点比选的数值模拟

A Modeling Study on Selecting the Effluent Discharge Points of the Nantong Seawage Discharging Project

采用数值模拟的方法,计算和分析了南通污水排海工程排放点位于-4m、-7m和-9m三个水深位置的污染物扩散影响,结果表明,在海域水动力条件下,-4m点高质量浓度COD水体面积最大,排放口污染最重,又位于浅海区,对海洋养殖极为不利,不宜选择;-7m点排放口和-9m点排放口均没有出现超过三类水质标准的区域,-7m点排放口影响水域COD质量浓度大部分为二类水质标准区域,只有面积很小甚至可以忽略不计的小范围三类水质标准区域,满足排海要求;-9m点排放口虽然对海域影响最小,但因其离岸距离过远,将大幅增加工程的施工及运营难度,为此,在能够保障COD排海条件的情况下,同时结合各方案管线长度带来的施工难度以及造价费用,采取-7m点为最佳排海口方案。

The Influence of pollutant diffusion at the effluent discharge points of the Nantong Seawage Discharging Project,which are located at water depth-4 m,-7 m and-9 m respectively,was calculated and analyzed by means of numerical simulation.The results have indicated that under the hydrodynamic conditions in the area studied,point-4 m is not suitable to choose,because at this point the area of water with high COD mass concentration is the largest,the pollution is the heaviest,and the water depth is so shallow that the marine aquaculture has been endangered extremely.At both points-7 m and-9 m,no areas in which the third order of water quality standard is exceeded are present.At point-7 m the level of COD mass concentration in most of the area falls to the second order of water quality standard and only a very small-scaled area that can be neglected belongs to the third order of water quality standard.Therefore,this point can be satisfied for the requirements of the seawage discharging.At point-9 m,however,the COD mass concentration has a small impact to the sea water,but the distance of the point away from the coast is so far that both the construction and operation are difficult.On the premise of guaranteeing the COD discharge and taking the difficulties induced by the pipeline length of different projects and the cost into account,it could better to choose point-7 m as the best seawage discharging point.