城镇污水处理厂活性污泥反硝化速率的影响因素及优化运行研究

INFLUENCING FACTORS AND OPTIMIZATION ANALYSIS OF DENITRIFICATION RATE IN URBAN WASTEWATER TREATMENT PLANTS

反硝化过程是影响污水处理厂出水总氮达标排放的重要环节之一,进水碳源、回流比、溶解氧(DO)和搅拌方式等均为影响活性污泥反硝化性能的重要因素。通过对太湖流域58座污水处理厂提标改造的运行效果进行评估分析,并对水质波动规律、工艺设计及设备设施等方面进行调研及优化分析,研究了不同条件对活性污泥反硝化速率的影响,探讨了污水处理厂在实际生产运行中反硝化脱氮过程主要存在的问题及对策。结果表明:各厂反硝化速率在0~5.18 mg NO3^--N/(g VSS·h)时,平均反硝化速率为1.40 mg NO3^--N/(g VSS·h),进水碳源浓度较低为各个污水处理厂反硝化速率较低的主要原因。其中外加碳源的种类、投加点位对反硝化脱氮具有较大的影响,在各厂进水中投加易降解碳源并保持较高的搅拌速率后,发现反硝化潜力为1.16~20.80 mg NO3^--N/(g VSS·h),表明改善进水水质并创造较好的反硝化条件,有利于整体反硝化水平的提升。此外,充分的搅拌条件也可增强污泥的反硝化性能。另外,选择合适的内回流比可以有效强化生物反硝化脱氮性能,但内回流中高DO对反硝化影响较大,降低回流DO可以有效提高NO3--N去除量。

Denitrification is one of the important processes of wastewater treatment plant (WWTP). The carbon source,reflux ratio,DO and agitation method are all important factors affecting the denitrification. Fifty-eight WWTPs in Taihu Lake Basin were evaluated for upgrading operation,and the law of water quality fluctuation,process design and equipments were investigated and analyzed to explore the impact of different conditions on the denitrification rate of activated sludge,so as to provide basic data for the operation and management of high standard WWTPs in the future. The results showed that the denitrification rate was in the range of 0 ~ 5. 18 mg NO3--N/ (g VSS·h),among which the average denitrification rate was 1. 40 mg NO3--N/ (g VSS·h). The main reason for the low denitrification rate was the low concentration of carbon source in the influent. Among them,the type and location of the added carbon source had greater impact on nitrification and denitrification.It could also enhance the denitrification performance of sludge through adding appropriate carbon source and sufficient stirring conditions. When adding easily degradable carbon source in the influent of each WWTP and maintaining a relatively low concentration of carbon source in the influent,the denitrification potential was found to be 1. 16 ~ 20. 80 mg NO3--N/g VSS·h at a high agitation rate,which indicated that improving the quality of influent water and creating better denitrification conditions were conducive to the improvement of the overall denitrification level. Setting proper internal reflux ratio could effectively enhance the biological denitrification performance,however,high dissolved oxygen in internal reflux had greater effect on denitrification,and reducing the reflux dissolved oxygen could effectively promote the NO3--N removal.