失稳硝化膜生物反应器的性能恢复研究

Study on the recovery of a failed nitrifying MBR system

对高水力负荷条件下丧失硝化功能的膜生物反应器进行恢复实验,将水力停留时间(HRT)从原来的5h延长到正常条件下可以实现完全硝化的10h后,在进水NH4+-N浓度为500mg.L-1的条件下反应器可去除99%的NH4+-N,但NO2--N出现严重积累,在60d的实验过程中NO2--N平均出水浓度为425mg.L-1.荧光原位杂交分析结果表明,氨氧化菌(AOBs)在总菌中的比例与恢复实验前没有变化,分别为12.9%(恢复实验期)和9.75%(恢复实验前),但氨氧化杆菌(Nitrosomonas)在AOBs中的比例从80%降低到40%;亚硝酸盐氧化细菌(NOBs)在总菌中的比例下降一半(从5.64%下降至2.84%),并以慢生型的Nitrospira为主.高NO2-含量和高胞外物浓度(497.1mg.L-1)可能是导致亚硝酸盐氧化功能难以恢复的主要原因.

In this study,we investigated the recovery process of a nitrifying membrane bio-reactor（MBR） system,which failed to achieve complete nitrification under the stress of high hydraulic loading（HRT）（5 h）.When the HRT was increased from 5 h to 10 h（the condition permitting complete nitrification previously） at an influent NH＋4-N concentration of 500 mg · L-1,an NH＋4-N removal of 99% was achieved.However,serious NO-2-N accumulation occurred,and the average NO-2-N concentration in the effluent was 425 mg · L-1 during the experimental period（60 days）.Fluorescence in situ hybridization（FISH） analysis showed that while the percentage of ammonia-oxidizing bacteria（AOBs） in total bacteria did not change（12.9% in this study compared to 9.75% at the HRT of 5 h in previous study）,the percentage of fast-growing Nitrosomonas sp.in AOBs decreased from 80% to 40%.The percentage of nitrite-oxidizing bacteria（NOBs） was only half of that at 5 h HRT（from 5.64% to 2.84%）,and the slow-growing Nitrospira sp.remained as the dominant nitrite oxidizing population.It is possibly the high NO-2 and extracellular（497 · 1 mg · L-1） concentrations in the reactor that made the nitrate oxidizing function difficult to recover.