Microbial activity and community structure in two terrace-type wetlands constructed for the treatment of domestic wastewater

The aim of the current study was to investigate the assembly and function of microbial community structure two terrace-typed constructed wetlands (TCWs) designed to improve the quality of domestic wastewater in rural areas. Also, the performance of 1-year-old wetlands was investigated. The TCWs had a strong ability remove the COD, NH4+-N, TN and TP, and promotes higher pollutant removal rates relative to single stage CWs. The microbial numbers and fluorescein diacetate (FDA) hydrolysis varied among different levels in both wetlands, and associated with the category of the filter media. The microbial community composition of the biofilm formed on the surface of filter media was studied by PCR-amplified restriction fragment length polymorphism (PCR-RFLP) and sequence analysis of 16S rRNA genes. A total of eight bacterial communities were sampled from the TCWs. Clones of each library were selected randomly for PCR-RFLP analysis of rDNA fragments, and eventually 87 genotypes were identified by RFLP finger-printings. These 87 genotypes were sequenced and their respective phylotype was identified through the Blast tool of NCBI ( similarity 95-100%) and phylogenetic analyses. Among these phylotypes, Proteobacteria was the most abundant group. Sequence analyses revealed that 52.9% (46) of the clone sequences were similar to those of the uncultured bacteria in the environment. Moreover, the bacterial diversity and composition were clearly displayed in different wetland levels and filter media. The bamboo charcoal and wetland levels may be the main factors affecting the composition of the microbial community. (C) 2014 Elsevier By. All rights reserved.