污水厂各处理单元对全氟辛酸浓度的影响

Effects of Various Treatment Units in Sewage Plants on the Concentration of Perfluorooctanoic Acid

全氟辛酸(PFOA)是一种持久性有机污染物,现有的生活污水处理厂没有针对其设置特定的处理单元,并且时常会有最终出水比进水浓度高的情况,为了明确生活污水处理厂中各处理单元对PFOA浓度的影响,该研究选取重庆市2座典型的生活污水处理厂,分别针对其完整流程中预处理、生化处理、深度处理及消毒等单元的进出水PFOA浓度进行分析,结果表明:2座生活污水处理厂对PFOA整体去除率为14.81%~18.76%和-38.71%~-21.99%,生化处理单元对PFOA浓度的影响最大,这可能是由于生化处理阶段的微生物对PFOA有吸附降解功能,是污水处理工艺中去除PFOA的关键,其去除率为-97.20%~25.55%,去除率的波动可能与工艺构造、参数设置影响污泥吸附有关;其次是消毒单元,去除率为-45.48%~-7.89%,这主要是由于次氯酸的强氧化性氧化了PFOA的前体物质,使PFOA浓度增高;预处理单元由于可以通过对吸附有PFOA的悬浮物、胶体颗粒进行有效的拦截和沉降,对PFOA表现出一定的去除效果,去除率为10.58%~37.42%;深度处理单元对PFOA浓度影响不显著,去除率为-2.91%~17.91%。

Perfluorooctanoic acid(PFOA)is a sustained organic contaminant.The existing domestic sewage treatment plants do not set specific treatment units for it,and there often exists that the final water outlet concentration is higher than the water inlet concentration.In order to clarify the impact of each treatment unit in the domestic sewage treatment plant on the concentration of perfluorooctanoic acid,this study selected two typical domestic sewage treatment plants in Chongqing,and analyzed the concentration of perfluorooctanoic acid in the inlet and outlet water of pretreatment,biochemical treatment,advanced treatment and disinfection units in the complete process.The results show that the overall removal rates of perfluorooctanoic acid by the two domestic sewage treatment plants are 14.81%~18.76%and-38.71%~-21.99%.The biochemical treatment unit has the greatest impact on the concentration of perfluorooctanoic acid,which may be due to the adsorption and degradation function of microorganisms in the biochemical treatment stage,which is the key to the removal of perfluorooctanoic acid in the sewage treatment process,and its removal rate is-97.20%~25.55%.The fluctuation of removal rate may be related to the process structure and parameter setting affecting sludge adsorption.For the disinfection unit,the removal rate is-45.48%~-7.89%,which is mainly due to the strong oxidation of hypochlorous acid,which oxidizes the precursor of PFOA and increases the concentration of PFOA.Because the pretreatment unit can effectively intercept and settle the suspended solids and colloidal particles adsorbed with PFOA,it shows a certain removal effect on perfluorooctanoic acid,with a removal rate of 10.58%~37.42%.The advanced treatment unit hadn’t affect the concentration of perfluorooctanoic acid observably,with a removal rate of-2.91%to 17.91%.