Activity And Community Composition Of Denitrifying Bacteria In PHBV Using Solid-phase Denitrification Processes

The concentration of nitrate in water is too high,which will not only cause eutrophication,but also threaten human health.In this study,polyhydroxybutyrate-co-hydroxyvalerate(PHBV)was used as solid carbon source and biofilm carrier to remove nitrate from synthetic wastewater and recirculating aquaculture system(RAS).On this bases,metabolic characteristics and microbial community structure of solid-phase denitrification were analyzed.This study provides a theoretical and experimental basis for the application of solid-phase denitrification in the treatment of nitrate pollution in water environment.When the influent NO3--N concentration was 80mg/L and the hydraulic retention time(HRT)was 6.5h,the nitrate removal rate reached 99%.When the influent NO3--N concentration was 120mg/L,HRT was 1.5h,and the removal rate was still above 80%.But the removal rate of HRT for 6.5h was much lower than 1.5h.For further understand the mechanism of solid-phase denitrification.The biofilm on the surface of carbon source under different working conditions was extracted.BiologECO plate and high throughput sequencing were used to detect the carbon metabolism function and microbial community in different periods.The results showed that the biofilm improved efficiency of phenolic acids and carbohydrate carbon source utilization under the influent NO3--N concentration increased condition.The dominant bacteria phylum of all biofilm samples were Proteobacteria,Bacteroidetes and Firmicutes.Comamonadaceae and Rhodocyclaceae belong to Proteobacteria which have denitrification function but different distribution in different periodsPHBV was used as solid carbon source and biofilm carrier to remove nitrate from recirculating aquaculture system(RAS).90 days later,NO3--N concentration in culture pond reduced from 100mg/L to 40mg/L,nitrite?ammonia nitrogen and DOC concentration were not changed significantly,and the growth of the fish was not affected.Biolog ECO plate was used to study carbon metabolism characteristics of recirculating aquaculture system after connected denitrification reactor.Denitrification reactor and MBBR biological filter due to different functions which caused different carbon metabolism characteristics.Because of continuous feeding,the whole system increased to amino acids,carboxylic carbon source utilization.High throughput sequencing is used to analyze recirculating aquaculture units(MBBR biological filter,solid phase denitrification reactor,culture pond)microbial community.Solid phase denitrification could increase the microbical diversity of RAS and affected obviously.The relative abundance of Bacteroidetes increased,and the dominant genus of solid phase denitrification was Acidovorax that increased abundance in culture pond,it proves that the denitrification reaction in the RAS.