三峡水库139ｍ蓄水后排污口污染带特性分析——以云阳污水处理厂为例

通过对云阳县污水处理厂排污口污染带平水期和枯水期的水文、水质、污染负荷现场同步监测,采用二维污染带水质模型模拟计算污染带的影响范围,对岸边污染带及其污染指标CODMn、NH3-N、TP按不同水期和不同监测断面的污染带特性进行了分析,初步预测了三峡大坝在156 m和175 m蓄水后的污染带变化趋势。结果表明,三峡水库蓄水引起的水位和江段特征的变化,改变了天然河道的水流条件,流速急剧减小,污水长时间滞留在排污口附近水域,不利于污染物的稀释、扩散,由于枯水期和平水期排放污水中的CODCr、NH3-N、TP浓度和长江纳污水体中的背景浓度的差异,其岸边污染带的长、宽、面积都将发生相应的变化,在排污口附近及下游仍会出现超背景和超标污染带。

Characteristics of contamination zone around discharge outlet after water storage of Three Gorges Reservoir at water level of 139m: A case study on Yunyang sewage treatment plant

Through local synchronous monitoring of hydrology,water quality and pollution loads of pollution zone around the discharge outlet of Yunyang sewage treatment plant in normal flow and low flow period,the pollution area was calculated by using two-dimensional water quality model.The change of pollution zone after the water level rising to 156m and 175 m was predicted.The flow condition in the natural river was changed by the water storage.Water velocity decreased rapidly and the sewage was stagnated near the discharge outlet for a long time,which was unfavorable for the dilution and diffusion of pollutants.Because of different concentrations of CODCr,NH3-N and TP in the sewage and river water in low flow and normal flow period,the length,width and area of contamination zone change accordingly.The water quality near the discharge outlet and downstream will still be higher than the background value and water quality standard.