Research On Functional Microbial Populations Of Anaerobic Granular Sludge In A Full-Scale UASB Treating Avermectin Wastewater

Methanogens, syntrophic acetogenic bacteria, sulfate reducing bacteria and filamentous bacteria are considered to be important functional microbial population in anaerobic granular sludge. Fluorescence in situ hybridization(FISH) based on 16S rRNA was used to analyze the corresponding functional microbial populations of anaerobic granular sludge with different formation periods(initial period, developing period, mature period and aging period) in a full-scale UASB treating avermectin wastewater. The results indicated that the distribution forms of methanogens, syntrophic acetogenic bacteria, sulfate reducing bacteria and filamentous bacteria as well as their dominant species were identical on the surface and inner face of granular sludge samples with different formation periods, Inaddition, the dominant species showed overlap distribution. However, the relative abundances of these functional bacterial populations were different, the relative abundances of methanogens, syntrophic acetogenic bacteria, sulfate reducing bacteria and filamentous bacteria were 25.50±8.63% to 50.08±8.87%, 10.08±0.81% to 28.06±2.12%,10.35±2.33% to 16.16±4.59% and 16.69±2.51 to 23.93±4.62%, respectively. The relative abundances of methanogens, syntrophic acetogenic bacteria and sulfate reducing bacteria in mature granular sludge were maximum, The relative abundances of methanogens on the inner face were larger than those on the surface of granular sludge samples, on the contrary, the relative abundances of syntrophic acetogenic bacterias on the inner face were smaller than those on the surface of granular sludge samples. The avermectin residue in wastewater showed possible inhibition effect on functional microbial community, compared their relative abundances with reported cases. The maximum specific methanogenic activities of granular sludge samples ranged from 1.311 to 1.562g·(g·d)-1 and the maximum specific acetate rate ranged from 0.912-1.145g·(g·d)-1. The variation tendencies of maximum specific methanogenic activities and the maximum specific acetate rate of granular sludge samples were the same with the relative abundance of methanogens and syntrophic acetogenic bacteria, implying the strong correlation of methanogens and syntrophic acetogenic bacteria with bioactivity of granular sludge.Polymerase chain reaction(PCR) and denaturing gradient gel electrophoresis(DGGE) were also used to analyze the microbial community in the anaerobic granular sludge. The result indicated that methanogens were the dominant archaea and their dominant species were Methanobacteriaceae, Methanosarcinaceae and Methanosaetaceae, and the relative abundances were 50.03%,39.22% and 10.75%, respectively. This was in accordance with the results of FISH analysis.