污水处理厂尾水排放形式对河流水质的影响研究

Influence of discharge mode of tail water from municipal sewage plant on urban river's water quality

城市污水处理厂排放的尾水对城市河流水质产生一定的影响,尤其是对排放口附近的区域。当前主要有集中排放和分散排放两种形式。模拟研究了污水处理厂6种尾水排放工况下河流COD浓度场的分布情况,包括尾水150 m生态拦截系统的岸边单孔(S1)、5孔(S2)、均匀溢流(S3)排放和河中单孔(M1)、5孔(M2)、均匀溢流(M3)排放。结果表明,下游河流的COD的相对浓度(C/C0)大小的排序为S1,S2,S3和M1,M2,M3,且排放口区域分散排放的C/C0远低于集中排放;在不同工况下,河中排放均比岸边排放的COD浓度低。分散排放形式有利于污染物的扩散,显著降低了污水处理厂尾水排放口附近污染物的浓度。在条件允许的情况下,污水处理厂尾水排放可采取河中均匀溢流排放形式(M3)。

The tail water from municipal sewage plants has a certain impact on urban river＇s water quality,especially on the field near the sewage outlet.Currently,there are two main discharge modes of the tail water,namely centralized and decentralized discharges.In this study,the COD concentration fields are simulated in near-field of sewage outlet under six discharge modes,including tail water release by single-outlet（S1）,five-outlets（S2）,uniform overflow（S3） by outlets along river bank and tail water release by single-outlet（M1）,five-outlets（M2）,and uniform overflow（M3） by outlet in river center of 150 m ecological interception system.The results show that the relative COD concentrations（C/C0） are in descending order of S1,S2,S3 and M1,M2,M3 at the downstream sections;furthermore,the C/C0 of the decentralized discharges is far lower than the centralized discharges in the outfall area;comparing with the different discharge modes,COD concentrations of the tail water by outlet in river center are lower than that by outlets along river bank in each working condition.Decentralized discharge mode can speed up the diffusion of pollutants and decrease the concentration of the water zone near sewage outlet significantly.Under a certain permitted condition,the uniform overflow（M3） of the tail water by outlet in river center would be an advantageous discharge mode.