污水厂尾水受纳河段沉积物磷形态及释放风险效应

2018年10月～2019年4月,在合肥市板桥河的蔡田铺污水厂尾水排放口上、下游河道4个采样点位,按照每两个月采样一次的频率采集沉积物和上覆水样,分析尾水排放对河道沉积物磷形态及磷平衡浓度(EPC_0)的影响,解析沉积物磷平衡浓度及磷释放风险的外源碳(乙酸钠)响应.结果表明,板桥河水体沉积物磷素受污水厂尾水影响较大,排放口上、下游沉积物总磷均值分别为789. 39 mg·kg~(-1)和854. 41 mg·kg~(-1),生物有效性磷均值分别为157. 19 mg·kg~(-1)和173. 37 mg·kg~(-1); 4个采样点的EPC_0值大小排序为:SP1 SP2 SP3 CP,表明尾水排入提高了河流EPC_0,致使河流沉积物磷释放风险增加;外源碳的添加明显降低沉积物的EPC_0值,特别是紧邻排放口的SP1下降最为显著,表明外源碳添加对降低沉积物磷释放风险有效.

Phosphorus Forms and Release Risk of Sediments in Urban Sewage Treatment Plant Effluent and Receiving Stream Reach

From October 2018 to April 2019, the surface sediment and overlying water samples were collected every two months from the upstream and downstream of the effluent outlet of the Caitianpu sewage treatment plant in the Banqiao River, Hefei City. The effects of the sewage treatment plant effluent on both phosphorus forms and the equilibrium phosphate concentration (EPC₀) in sediments were analyzed. The response of equilibrium phosphate concentration to external carbon (sodium acetate) and the release risk of phosphorus in sediments were investigated. Result show that the phosphorus pollution in Banqiao River was more severe. The average values of total phosphorus in the sediments at the upper and lower effluent outlet were 789.39 mg·kg^-1 and 854.41 mg·kg^-1, respectively, and the average bio-available phosphorus amounts were 157.19 mg·kg^-1 and 173.37 mg·kg^-1, respectively. The EPC₀ values of the four sampling points decreased in the order SP1 > SP2 > SP3 > CP, indicating that the sewage treatment plant effluent increased the EPC₀ level and phosphorus release risk of the stream sediments. Moreover, the addition of exogenous carbon significantly decreased the EPC₀ value of the sediment, especially in SP1, suggesting that the addition of exogenous carbon decreased the risk of phosphorus release from sediments.