| With the large-scale development of the livestock industry, a large number of manure and wastewater is produced, and would become severe pollution source if it was not treated in a right manner in time. Hence, it’s very important to reduce the pollutants to the environment accompanying with changes of farm producing pattern, by investigating and developing new technologies in treating livestock wastewater. Microorganisms as one of the most important part in the wastewater biological treatment system, play an essential role in reducing the pollutants and achieving harmlessness of livestock wastewater. Therefore, in this study, we aimed to analyze the microbial diversity in the activated sludge and livestock wastewater during the treatment process of "ABR-CASS-constructed wetland" system at Sichuan Agricultural University, by using the next generation Mi-seq sequencing technology and detecting the physical and chemical items. The dominant bacteria will be screened in the samples at different stages of treatment process, and also will be analyzed combining with the changes of physical and chemical items, to investigate the possible mechanism of the wastewater biological treatment in this system, and also would be further provide a reference for studies on improving the sewage treatment process and the efficiency of the biological treatment. The main results and conclusions in our study are as follows:(1) The results of monitoring temperature and pH value showed that the temperature was stable during the entire experiment phase, and there were little apparent fluctuations for pH by treatment, which ranged from 6.87-7.66. The main pollutants in livestock wastewater had been removed by ABR-CASS- constructed wetland system, which could be reflected by items including CODcr, TP and NH4+-N, and the removal rates were 71.84%, 17.28% and 66.51%, respectively. The data also showed there were differential removal efficiencies for individual items at different disposal periods.(2) Basing on the result of sequencing data, total 28 phyla of bacterial have been found in the wastewater samples, and the most abundance of them were mainly included the Proteobacteria, Bacteroides and Firmicutes. In addition, the abundance of bacterial genera such as arcobacter (Proteobacteria), Sulfurospirillum (Proteobacteria), Bacteroides (Bacteroidetes) and Acinetobacter (Proteobacteria), Hydrogenophaga (Proteobacteria) is higher in 4 wastewater samples at different treatment process, and they are characterized as the dominant bacterial genera in the wastewater.(3) The sequencing data from activated sludge at different treatment phase showed that the composition and structure of microbial communities were relatively stable during the whole studied periods (2months), indicating no apparent microbial succession phenomenon occurred. Total 31 bacterial phyla has been found in all sludge samples, only 21 of them were commonly found in different samples at different phase of treatment, including ABR, CASS and artificial wetland. The first dominant abundance microorganisms in the studied process were Proteobacteria and Bacteroidetes, followed by Firmicutes. Based on the classification levels of bacteria, it showed there are different predominant abundance bacteria for them at different treatment phase. Basing on the classification level of genus, the most abundance bacteria were Bacteroidales in Bacteroidetes, and uncharacterized bacterias in Sphingobacteriales, followed by Syntrophus.(4) The clustering results revealed that it has some relationships between the community and diversity of microbial in wastewater and in its corresponding sludge at the treatment process. However, it also showed some differences in their individually predominant abundance microbial, indicating that the wastewater may have some functional bacteria, which are necessary for removal pollutants, but they may exist with a low abundance level in sludge. |
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