中试膜生物反应器处理奶牛养殖污水的微生物群落结构分析

Microbial community structure analysis of a pilot-scale membrane bioreactor for dairy farm wastewater

为了研究中试膜生物反应器在不同运行参数下处理高浓度奶牛养殖污水时膜生物反应器(Membrane bioreactor,MBR)内微生物群落结构的演变情况,对不同污泥龄(Sludge retention time,SRT)、水力停留时间(Hydraulic retention time,HRT)和曝气方式(连续曝气、3种间歇曝气)形成的5种工况下MBR微生物组成、多样性以及优势菌群分布进行了表征,同时对比研究了不同工况下污染物去除效果。结果表明,MBR处理高浓度奶牛养殖污水的最佳运行参数:SRT为30 d、HRT为96 h、曝15 min/停10 min,此参数条件下化学需氧量(COD)、NH_(4)^(+)-N、总氮(TN)和总磷(TP)的去除率分别为97.0%±0.5%、90.4%±1.3%、85.5%±1.8%和89.6%±5.6%,处理出水中4种水质指标浓度分别为(224±56)、(45±8)、(105±19)mg·L^(-1)和(4±2)mg·L^(-1),运行期间部分处理出水的COD浓度达到农田灌溉水质标准要求,高效稳定的有机物和氮磷去除效果依赖于MBR微生物的多样性和功能微生物的稳定性。反硝化除磷菌门的Proteobacteria(变形菌门)、Firmicutes(厚壁菌门)和Bacteroidetes(拟杆菌门)的丰度占总细菌的85.2%,污水高效脱氮除磷效率与反硝化除磷菌的种类、相对丰度密切相关;优势菌纲Gammaproteobacteria(γ-变形菌纲)、Bacteroidia(拟杆菌纲)和Clostridia(梭菌纲)的相对丰度总占比达81.2%,其中功能性除磷菌纲Gammaproteobacteria的丰度最高,达57.3%,保证了处理出水较低的TP浓度;优势反硝化菌属为Ottowia(奥托氏菌属),相对丰度占比达54.8%,可显著提高MBR脱氮效率。MBR处理高浓度奶牛养殖污水可实现良好的污染物去除效果,污染物去除效果与优势菌群密切相关,优势菌群相对丰度越高,越有利于提高污水处理效果和出水水质。

This study was conducted to explore the evolution of the microbial community structure within a pilot-scale membrane bioreactor(MBR)for treating high-strength wastewater from dairy cattle farms under different operating parameters.The microbial compositions,diversity,and distribution of dominant microbiota were characterized under five operating conditions formed by various sludge retention times(SRT),hydraulic retention times(HRT),and aeration modes(continuous aeration,three types of intermittent aeration).The pollutant removal effects under different conditions were also compared.The results showed that the optimal operating parameters for conducting MBR treatment on high-strength dairy wastewater were:SRT of 30 d,HRT of 96 h,intermittent aeration of 15 min on/10 min off,resulting in removal efficiencies of 97.0%±0.5%for chemical oxygen demand(COD),90.4%±1.3%for ammonia nitrogen(NH_(4)^(+)-N),85.5%±1.8%for total nitrogen(TN),and 89.6%±5.6%for total phosphorus(TP).In the treated effluent,the concentrations of four water quality indexes were found to be(224±56),(45±8),(105±19)mg·L^(-1),and(4±2)mg·L^(-1),respectively.The COD concentration of some of the treated effluents met the standard for irrigation water quality during the entire operation period.This highly efficient and stable removal of organic matter,nitrogen,and phosphorus was attributed to the diversity and stability of MBR microorganisms.The dominant phyla of denitrifying and phosphorus-removing bacteria,including Proteobacteria,Firmicutes,and Bacteroidetes,collectively represented 85.2%of the total bacterial community.The effectiveness of high-efficiency nitrogen and phosphorus removal in wastewater was found to be closely associated with both the species and the relative abundance of these denitrifying and phosphorus-removing bacteria.The combined relative abundance of three predominant classes,namely Gammaproteobacteria,Bacteroidia,and Clostridia,comprised 81.2%of the total,with Gammaproteobacteria demonstrating the highest relative abundance at 57.3%.This high abundance of Gammaproteobacteria,a functional phosphorus-removing bacterial class,contributed to the noteworthy reduction of TP concentration in the treated effluent.Ottowia,the dominant denitrifying bacterial genus,exhibited a relative abundance of 54.8%,leading to significant improvements in nitrogen removal efficiency.The MBR system had demonstrated considerable efficacy in the treatment of high-concentration dairy wastewater.The effectiveness of MBR in pollutant removal was intricately linked to the composition of their predominant bacterial communities.Specifically,an increased relative abundance of key bacterial taxa within these communities enhanced the overall performance of MBR and improved the quality of the treated effluent.