HRT对城市污水厂尾水反硝化深度脱氮的影响

摘要

污水厂尾水回用作为水源时,其ρ(TN)较高是亟待解决的问题.在调研污水厂尾水水质的基础上,利用MBBR(移动床生物膜反应器)对其进行深度脱氮,并考察HRT(水力停留时间)对不同填料(聚乙烯和陶粒)的MBBR运行效果的影响.结果表明,NO3--N是尾水中氮的主要形态,其质量浓度约占ρ(TN)的80.8％±8.4％.HRT分别为12、8和4h时,对NO3--N去除率影响不大,均能达到90％以上,但反硝化能力随着HRT的缩短而成倍增加;HRT为4h时各反应器的反硝化能力最大,聚乙烯和陶粒MBBR中分别为(28.4±14.5)和(27.4±14.3)mg/(L·d)(以NO3--N计).随着HRT的减少,CODCr去除率呈降低趋势.三维荧光分析表明,进、出水中均含有类富里酸和类蛋白质等DOM物质.HRT为8h时MBBR对DOM的去除率最高,聚乙烯填料MBBR对有机污染物的去除效果略优于陶粒填料.综合考虑氮和有机污染物去除效能,聚乙烯和陶粒填料MBBR优化HRT均为8h.%High total nitrogen content is an urgent issue when wastewater treatment plant (WWTP) effluent is used as a water source.Based on a long-term investigation of WWTP effluent quality,MBBR was selected for advanced denitrification of WWTP effluent,and the influence of Hydraulic Retention Time (HRT) on the performance of MBBR filled with different carriers was studied.The results showed that NO3--N was the predominant nitrogen in the WWTP effluent,accounting for 80.8％ ± 8.4％.In the range of 4 to 12 h,HRT slightly affected the NO3--N removal rate,which was higher than 90％.However,the denitrification rate increased considerably with HRT decrease,and the maximum denitrification,which was (28.4-± 14.5) and (27.4 ± 14.3) mg/(L· d) (in NO3--N) for MBBR filled with polyethylene and haydate,respectively,occurred at 4 h HRT.Chemical Oxygen Demand (CODCr) removal efficiency decreased with HRT decrease.Three-dimensional fluorescence spectra showed that both the influent and effluent contained dissolved organic matter (DOM) as fulvic acid and protein-like substance,and the maximum DOM removal occurred at 8 h HRT.Organic pollutants removal efficiency of MBBR filled with polyethylene was slightly higher than that filled with haydate.Integratively considering the nitrogen and organic pollutants removal efficiency,8 h HRT was optimum for MBBR filled with polyethylene and haydate.