Characterization and Dynamic Shift of Microbial Communities during Start-Up, Overloading and Steady-State in an Anaerobic Membrane Bioreactor

Abstract

A lab-scale anaerobic membrane bioreactor (AnMBR) with a side stream tubular membrane was developed to treat synthetic domestic sewage to evaluate its performance and the dynamic shift of bacterial and archaeal communities during the start-up, steady-state, overloading and recovery periods of operation at mesophilic temperatures. During the start-up period, the bacterial and archaeal communities changed drastically, and Proteobacteria and Bacteroidetes predominated. During the steady-state period, the AnMBR exhibited excellent COD removal above 91%, and COD of the effluent was below 50 mg/L. High-throughput sequencing analysis results revealed that bacterial and archaeal communities shifted significantly from the start-up to the steady-state period, and that the Proteobacteria phylum predominated on days 140, 162 and 190, and the archaea community hydrogenotrophic methanogen genus Methanolinea (1.5–6.64%) predominated over the aceticlastic methanogen genus Methanothrix (1.35–3.07%). During the overloading period, significant changes occurred in microbial community on day 210, e.g., the phyla Bacteroidetes (30%), Proteobacteria (23%) and Firmicutes (18%) predominated and the archaeal community was completely suppressed, and Methanobrevibacter (0.7%) was the only methanogen genus that emerged in the overloading period. After a shock loading period, the microbial communities exhibited significant changes within the ranks of methanogens and shifted to dominance of the aceticlastic methanogen pathway. In addition, the TVFAs to alkalinity ratio in this study was suitable as an indicator of monitoring performance in the AnMBR operation.

System Performance Corresponding to Bacterial Community Succession after a Disturbance in an Autotrophic Nitrogen Removal Bioreactor

“…The most important finding of this study is that when bacterial community components are taken into account, the explained variation for the system nitrogen removal processes substantially increases, compared to the analysis based on physicochemical variables alone ( Table 1 ). While associations between microbial community and bioreactor performance have frequently been suggested ( 16 , 19 , 24 , 29 , 43 ), here we provide for the first time statistically evaluated results supporting the concept that microbial community succession exerts a significant influence on system functional processes of the bioreactor, beyond the effects exerted by the operational physicochemical parameters. These microbe-system relationships are expected but have hitherto been difficult to quantitatively evaluate.…”

“…Since bioreactors are typically inoculated with microbial consortia from various sources (such as sludge, soil, or compost), primary succession has been reported to vary depending on inoculum source and initial community structure ( 25 – 28 ). Then, after a period of operation in a controlled setting, the bioreactor can be considered to reach a steady state when biomass concentration and system performance approach a constant ( 29 – 31 ). However, secondary succession of microbial communities might occur due to disturbances, such as overloading ( 32 ), adding new substrates ( 33 ), or modifying operational parameters ( 23 ).…”

Effects of Solids Retention Time on the Anaerobic Membrane Bioreactor with Yttria-Based Ceramic Membrane Treating Domestic Wastewater at Ambient Temperature

“…This could be attributed to the nature of the influent wastewater or to the low temperature. As an example, our previous study by Martin et al, 2018 has resulted in alkalinity 675 ± 188.42 mg/L CaCO 3 , which was sufficient for sustaining the anaerobic microbial community with the same synthetic wastewater [29]. Moreover, as mentioned in the following section, due to the membrane feeding pump failure that occurred on Day 85, the significant changes in alkalinity have been reported as the ANOVA analysis of SRT versus alkalinity resulted in P values less than 0.05.…”

“…Synthetic domestic wastewater was prepared to represent domestic wastewater according to our previous work [29]. Its composition is listed in Table 2.…”

“…The acidification index (total volatile fatty acids/total alkalinity) (VFAs/ALK) is regarded as an early-warning indicator of acidification in anaerobic treatment system. Generally, the desirable VFAs/ALK ratio in anaerobic bioreactors should be less than 0.3 [29]. Figure S3 exhibits the variation of VFAs (acetic, propionic, i-butyric, n-butyric, i-valeric, and n-valeric acids) and VFAs/ALK ratio.…”