好氧-低氧生物滤池对低碳氮比污水脱氮研究

Effective Nitrogen Removal in Low C/N Wastewater with Combined Aerobic-Low DO Biofilm Treatment Process

针对我国大多数城市污水低碳氮比的水质特点,提出以好氧-低氧淹没式生物滤池对其进行深度脱氮处理.试验过程中,保持好氧段DO为3.5～4.3 mg/L、低氧段DO为0.9～1.1 mg/L,通过调节2段进水分流比、水力停留时间(HRT)、进水碳氮比(C/N)实现深度脱氮效果.进行了3个阶段的试验研究:首先,以低C/N城市污水为参照,确定原水C/N=3∶1,分流比1∶1,调节HRT(好氧+低氧段)分别为(10+5)h、(8+4)h、(6+3)h、(4+2)h,考察系统脱氮效能;其次,根据第一阶段的试验结论,选定原水C/N=3∶1,HRT(好氧+低氧段)=(10+5)h,调节分流比为1∶2、1∶1、2∶1,考察系统脱氮效能;最后,根据前2个阶段试验结论,选定HRT(好氧+低氧段)=(10+5)h,分流比1∶1,分析原水C/N分别为2∶1、3∶1、5∶1、10∶1时脱氮效果的变化.结果表明,适宜的原水C/N为5∶1,好氧和低氧池分流比为1∶1,好氧和低氧池HRT分别为10 h和5 h,进水COD、氨氮和总氮浓度分别为254、37.2和48.2 mg/L时,出水COD、氨氮和总氮浓度分别达48、9.3和14.8 mg/L.试验过程中,通过好氧段强化硝化、低氧段强化反硝化,同时利用生物膜内好氧、缺氧的分区结构,达到好氧池内弥补反硝化和低氧池内弥补硝化的脱氮效能,以保证出水水质.

The municipal wastewater in China is characterized by low ratio of carbon to nitrogen,which is the key restrictive factor for effective biological removal of nitrogen.In this study,the aerobic-low DO biofilm process was used for the nitrogen removal of municipal wastewater.By means of adjusting inflow ratios of aerobic section to low-DO section,hydraulic retention time（HRT） and inflow ratio of carbon to nitrogen（C/N）,the performances of nitrification in aerobic biofilm section and denitrification in low-DO section could be improved,the good performance of nitrogen removal was achieved.In order to insure the good effluent quality,especially for ammonia nitrogen and total nitrogen indexes,the nitrification and denitrification could be made up in aerobic and low-DO biofilm section respectively due to the coexistence of aerobic and anoxic zone in biofilm.There were 3 stages for the research process.In the first stage,the original C/N,inflow ratios of aerobic section to low-DO section were chosen as 3∶1 and 1∶1 respectively,then the effects of various HRT（aerobic section ＋ low DO section） values such as（10＋5） h,（8＋4） h,（6＋3） h,（4＋2） h to nitrogen removal were analyzed.According to the conclusion in the first stage,the original C/N was kept at 3∶1,HRT（aerobic section ＋ low DO section） was（10＋5） h.Then,the effects of various inflow ratios to nitrogen removal were studied in the second stage.In the third stage,when HRT（aerobic section ＋ low DO section） was（10＋5） h and inflow ratio was 1∶1,the original C/N were adjusted from 2∶1,3∶1,5∶1 to 10∶1.To conclude,the optimal parameters for nitrogen removal in the biofilm system were as follows： original C/N=5：1,inflow ratio of aerobic to low-DO section=1∶1,HRT of aerobic and low-DO sections were 10 h and 5 h respectively.As a result,COD,ammonia nitrogen and total nitrogen could be removed from 254 mg/L to 48 mg/L,37.2 mg/L to 9.3 mg/L and 48.2 mg/L to 14.8 mg/L respectively.