Microbial population dynamics of granular aerobic sequencing batch reactors during start-up and steady state periods

摘要

This study investigates microbial population dynamics in granular sequencing batch reactorsn(GSBR). The experimental results of DGGE fingerprint of sludge demonstrated that the microbialncommunity structure of sludge shifted significantly during granulation period and nutrient removalnimprovement period. After reactor performance and physical characteristics of sludge reachednsteady state, microbial population of sludge became relatively stable. The high similarity ofnmicrobial community structure between co-existed flocculated sludge and granular sludge innGSBR at different operation phases indicated that similar microbial consortium could exist inncompact aggregated form or in amorphous flocculated form. Therefore, strong selection pressurenwas still required to wash out flocs to maintain the stability of reactor operation. In addition,nit was found that substrate type had considerable impact on microbial species selection andnenrichment in granular sludge. The clone library of granular sludge showed that microbial speciesnin divisions of a-Proteobacteria, b-Proteobacteria, g-Proteobacteria and Bacteroidetes existednwithin acetate-fed granule communities and Thauera spp. from b-Proteobacteria accounted forn49% of the total clones in the whole clone library. It is thus speculated that Thauera spp. arenimportant for the formation of acetate-fed granules under the conditions used in this study,nmaintaining the integrity of granules or substrate degradation.