Phylogenetic characterization of microbial communities in a full-scale vermifilter treating rural domestic sewage

Abstract

A full-scale vermifilter (VF) system was conducted and applied to treat rural domestic sewage caused by water pollution in China. The performance of full-scale VF and the microbial communities were investigated. Results showed that the average removal efficiency of COD, BOD5, NH4+N, and TSS were 67.6%, 78.0%, 92.1%, and 89.8%, respectively, with low sludge production of 0.08kgSS/kg CODremoved during 17-month operation of VF, and the final effluent could meet the latest standards of irrigation water quality in China. Phylogenetic analysis of 16S rRNA gene sequences revealed that VF was dominated by Proteobacteria, especially the γ-proteobacteria, followed by Acidobacteria, Bacteroidetes, and Planctomycetes. Most of these phyla are known to utilize a wide spectrum of carbon and nitrogen sources, or to resist a high hydraulic loading rate. Numerically minor but functionally relevant community constitutes were also detected, such as Gemmatimonadetes, Verrucomicrobia, Actinobacteria, and Chloroflexi. Earthworm activity, which causes sludge reduction of the VF, had a significant impact on the microbial population because of special microbes related to earthworm gut- and cast-associated processes that were abundant in VF biofilms. These results highlight the stability and the diverse microbial communities of full-scale VF under real operating conditions. This study is an essential first step to improving the design and operation of VF systems for practical application in domestic sewage treatment.