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

Abstract

This study investigates microbial population dynamics in granular sequencing batch reactors (GSBR). The experimental results of DGGE fingerprint of sludge demonstrated that the microbial community structure of sludge shifted significantly during granulation period and nutrient removal improvement period. After reactor performance and physical characteristics of sludge reached steady state, microbial population of sludge became relatively stable. The high similarity of microbial community structure between co-existed flocculated sludge and granular sludge in GSBR at different operation phases indicated that similar microbial consortium could exist in compact aggregated form or in amorphous flocculated form. Therefore, strong selection pressure was still required to wash out flocs to maintain the stability of reactor operation. In addition, it was found that substrate type had considerable impact on microbial species selection and enrichment in granular sludge. The clone library of granular sludge showed that microbial species in divisions of α-Proteobacteria, β-Proteobacteria, γ-Proteobacteria and Bacteroidetes existed within acetate-fed granule communities and Thauera spp. from β-Proteobacteria accounted for 49% of the total clones in the whole clone library. It is thus speculated that Thauera spp. are important for the formation of acetate-fed granules under the conditions used in this study, maintaining the integrity of granules or substrate degradation.

Microbial Population Dynamics and Ecosystem Functions of Anoxic/Aerobic Granular Sludge in Sequencing Batch Reactors Operated at Different Organic Loading Rates

“…These four genera have earlier been reported in different granular sludge reactors operated for organic carbon and nitrogen removal (Li et al, 2008; Ebrahimi et al, 2010; Liu et al, 2010; Zhao et al, 2013, 2015; Kong et al, 2014; Lv et al, 2014; Cydzik-Kwiatkowska, 2015; Figueroa et al, 2015). Thauera and Zoogloea have been found at both low and high OLRs, between 1 and 15 kg COD m -3 d -1 (Ebrahimi et al, 2010; Zhao et al, 2013; Lv et al, 2014).…”

The competition between flocculent sludge and aerobic granules during the long-term operation period of granular sludge sequencing batch reactor

“…Aerobic granules are the products of microbes that are responding to external survival pressure, such as short settling time or high shear force exerted on the reactor. During the start-up period of the granular sludge reactor, the radical shifts of microbial community structure are reported [22][23][24]. In addition, Li and Li [25] found the rapid granulation by the selective discharge of slow-settling sludge flocs, while mixed, unselective sludge discharge did not lead to the aerobic granulation.…”

Effects of Wash-Out Dynamics on Nitrifying Bacteria in Aerobic Granular Sludge During Start-Up at Gradually Decreased Settling Time

“…Weissbrodt et al [16] reported reduced nitrogen removal efficiency due to severe biomass wash-out; the ammonium and nitrogen removal recovered after 40 days (to 77% and 60%, respectively). Liu et al [17] achieved complete ammonium removal after 49 days, while Zhao et al [29] obtained the same after 21 days with simultaneous stepwise decreased settling time and gradually increased COD and N-load. However, the authors did not provide information about the strategy applied for decreasing the settling time.…”

“…The subsequent impact of biomass loss is deteriorated nitrogen removal efficiency. Rapid changes in the microbial population have also been documented during start-up [17,18]; however, very few studies have examined the abundance and dynamics of the nitrifying community during granulation [19]. Based on a modeling approach, Su et al [20] suggested that a stepwise decrease of settling time can be an effective method for optimizing biomass discharge during start-up, but their study did not investigate the nutrient removal during granulation.…”