Researches On Microbial Community Structure And Diversity In Textile Wastewater Treatment Systems For High-efficiency Biodegradation Of Polyvinyl Alcohol

Based on excellent physicochemical properties, such as viscosity, film forming, and adhesive strength, PVA is widely used, especially in textile and paper manufacturing. The production of PVA peaked as the volume of synthetic, water-soluble polymers in the world in2007. More than half of2012world consumption was produced and consumed in China, and the demand is forecast to grow at an average annual rate of5.8%from2012to2017.It was estimated that1g of PVA generates0.016g5-day biochemical oxygen demand (BODs) or1.6g chemical oxygen demand (COD), BODs/COD=0.01, a low ratio indicating the poor degradability of PVA. The biodegradation of PVA has been reviewed by Chiellini et al., Matsumura, Kawai and Hu, and Amann and Minge. Biodegradability efficiency under aerobic conditions was74.5%-81.3%or in anaerobic sludge above17.2%. However, one long-term steadily running textile wastewater treatment system was found, in which PVA exhibited high-efficiency biodegradation. Therefore, it was critical and necessary to estimate microbial community structure, composition, and functional organization of the specific system.For understanding of the microbial community structure and composition of textile wastewater treatment systems for biodegradation of polyvinyl alcohol (PVA),454high-throughput pyrosequencing was applied to analyze the16S rRNA gene of bacteria and archaea, and18S rRNA gene of eucarya in a full scale conventional textile wastewater treatment system (W1) with highly PVA-degrading efficiency and another full scale one (W2) affiliated to the same textile company with general PVA-degrading efficiency as a comparison. In total,1678(W1) and578(W2) operational taxonomic units (OTUs) were clustered respectively for bacterial communities at a3%distance,440(W1) and434(W2) OTUs for archaeal communities, and694(W1) and1000(W2) OTUs for eukaryotic communities.454-pyrosequencing could also detect the minority bacteria that were hardly detected by the conventional molecular biology methods. Although bacterial and archaeal communities were highly functionally organized (Fo> 80%), clear differences of three domains between the samples were revealed by richness and diversity indicators. At the class level, main subgroups of Proteobacteria (α-,β-,δ-, γ-proteobacteria) were distributed relatively evenly in W1, while y-proteobacteria was the predominant bacterial class (75.65%) in W2; at the genus level, Methanosaeta was the dominant archaeal genus (70.07%) in W1and may accelerate the degradation of polyvinyl alcohol. Thus, y-proteobacteria and Methanosaeta may be the key prokaryotic organism contributing to the PVA-degrading efficiency difference between the two systems. The relative abundance of uncultured Nitrosomonadaceae (AOB) and Ottowia in W1were more than that in W2, while Marine_Group_Ⅰ in W1less than W2, revealing denitrifying bacteria and denitrifying archaea worked together to support the ammonium oxidation in the two systems.