[Analysis of methanogenic community of anaerobic granular sludge in a full-scale UASB treating avermectin wastewater].

Methanogens is considered to be important functional microbial population in anaerobic granular sludge. Fluorescence in situ hybridization was used to analyze methanogens of anaerobic granular sludge in a full-scale UASB treating avermectin wastewater. The results indicated that the distribution forms of methanogens, Methanobacteriales and Methanosarcinales were identical on the surface and inner face of granular sludge samples in different formation stages (with different diameters) , although the relative abundances of these methanogens were different. The relative abundances of methanogens on the inner face were larger than these on the surface of granular sludge samples. The relative abundances of Methanobacteriales were larger than these of Methanosarcinales. The relative abundances of methanogens in all granular sludge samples ranged from (25.50 +/- 8.63)% to (48.67 +/- 8.87)%. The maximum relative abundances of methanogens were obtained in mature granular sludge with diameter of 1.0-2.0 mm, (47.08 +/- 8.26)% on the surface and (48.67 +/- 8.87)% on the inner face, respectively. The avermectin residue in wastewater showed possible inhibition effect on methanogens. The maximum specific methanogenic activities of granular sludge samples ranged from 1.311 to 1.562 g/(g x d), varying as same as COD removal ratios and relative abundances of methanogens, implying the strong correlation of methanogens with bioactivity of granular sludge.