Diversity and distribution of bacteria in a multistage surface flow constructed wetland to treat swine wastewater in sediments

Managing waste produced from swine farming operations is a significant agricultural and environmental challenge. Confined animal feeding operations continually generate large amounts of animal waste, which necessitates adequate waste management systems. This study examines the use of multistage surface flow constructed wetlands (SFCWs) to treat pig farm sewage. The wastewater removal rate, sediment deposits, physicochemical properties, and microbial community compositions of each segment of a SFCW were examined. The results indicated that removal rates of chemical oxygen demand (COD), total nitrogen (TN), NH4+, NO3−, and total phosphorus (TP) were 89.8%, 97.9%, 98.2%, 87.6%, and 96.4%, respectively, in the multistage SFCW. The general trend showed increase in the dissolved oxygen (DO) concentrations and oxidation reduction potential (Eh) from the beginning of the SFCW to its end. Sediment concentrations of N and P in each segment of the SFCW generally decreased, suggesting their accumulation in each segment. High-throughput sequencing indicated that the bacterial diversity increased over time. Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes were dominant in multistage SFCW bacterial communities at the phylum level. Results further indicate that DO and Eh are major environmental factors that influence the bacterial community distribution. Overall, our findings suggest that multistage SFCWs not only improve contaminant removal but also change the bacterial community composition and promote bacterial community diversity.