低溶解氧胁迫下生物膜-颗粒污泥anammox工艺生物富集特性及脱氮功能菌群和基因的演变研究

Bioaccumulation characteristics and the evolution of nitrogen removal related functional bacteria and genes in biofilm-granular sludge anammox process under low dissolved oxygen stress

为探究低溶解氧(DO<0.5 mg·L^(-1))条件对厌氧氨氧化(anammox)工艺脱氮性能、生物膜及颗粒污泥特性、菌群结构及其功能基因的影响,试验构建了试验室规模的上流式载体生物膜-颗粒污泥anammox系统.结果表明,反应器在长达175 d的运行过程中脱氮性能良好且运行十分稳定,系统平均NH_(4)^(+)-N、NO_(2)^(-)-N和TN去除率分别为95.0%±2.1%、99.0%±1.0%和87.0%±2.1%.在紧密结合型EPS(TB-EPS)中,颗粒污泥与载体生物膜的蛋白(PN)/多糖(PS)值分别为0.094和0.048,有利于颗粒污泥和生物膜的形成.粒径大于0.5 mm的anammox颗粒污泥占比达到72.0%,有利于系统持留脱氮菌群.菌群结构分析中发现,生物膜的优势菌门分别为变形菌门(29.6%)、浮霉菌门(10.7%)和绿弯菌门(10.7%),颗粒污泥具有相似的优势菌门,对应相对丰度(RA)分别为25.6%、24.3%和7.6%.生物膜和颗粒污泥的优势AnAOB属均为Candidatus Brocadia,但其在颗粒污泥中的相对丰度为14.3%,是生物膜中的3.4倍.在颗粒污泥与载体生物膜中均存在与脱氮相关的功能基因nirS、nirK、nirB、hdh、hzo和hzs,由于低DO(0.11~0.13 mg·L^(-1))的存在还发现了与硝化相关的功能基因,包括氨单加氧酶(amoA/B/C)、羟胺氧化还原酶(hao)和亚硝酸盐氧化还原酶(nxrA/B).基于此,低DO条件反应器取得了较高的anammox脱氮性能,并有可能发生了硝化反应和内源反硝化反应,从而减小了anammox反应的化学计量比.

A lab-scale upflow biofilm-granular sludge anammox system was developed to explore the effects of low dissolved oxygen(DO<0.5 mg·L^(-1))on the nitrogen removal performance,characteristics of biofilm and granular sludge,and nitrogen removal related functional bacteria and genes of anammox process. Experimental results showed that the nitrogen removal performance of the reactor was efficient and stable during the 175 day’operation with the average NH;-N,NO;-N and TN removal efficiencies of 95.0%±2.1%,99.0%±1.0% and 87.0%±2.1%,respectively. The protein(PN)/polysaccharide(PS)values of tightly bound extracellular polymeric substances(TB-EPS)were 0.094 and 0.048 found in granular sludge and biofilm,respectively. These values were favored to the formation of granular sludge and biofilm. The proportion of anammox granular sludge with particle size of greater than 0.5 mm reached 72.0%,which was conducive to the retention of nitrogen removal bacteria in the system. Metagenomic sequencing results demonstrated that the phyla Proteobacteria(29.6%),Planctomycetes(10.7%)and Chloroflexi(10.7%)were dominant at phylum level in biofilms,and similar dominant phyla were observed in granular sludge with corresponding relative abundances(RA)of 25.6%,24.3% and7.6%. The main AnAOB of Candidatus Brocadia in granular sludge(14.3%)was 3.4 times higher than that in biofilm. Nitrogen removal related genes nir S,nir K,nir B,hdh,hzo and hzs enriched in both granular sludge and biofilms. Due to the low DO levels(0.11~0.13 mg·L^(-1))in reactor,functional genes associated with nitrification were found,including ammonia monooxygenase amo A/B/C,hydroxylamine oxidoreductase(hao),and nitrite oxidoreductase(nxr A/B). Thus,effective anammox performance was obtained at low DO circumstance,and nitrification and endogenous denitrification might occur under such conditions,which decreased the stoichiometric ratios of anammox reaction.