Microbial population dynamics in temperature‐phased anaerobic digestion of municipal wastewater sludge

Abstract

BACKGROUND The present study compared the performance and capability of thermophilic–mesophilic, temperature‐phased anaerobic digestion (TPAD) of wastewater sludge at 45 and 55 °C in terms of rate of hydrolysis and methanogenesis at two point interval times – December and January – with operational conditions kept constant (total solid content 6.5%, solids retention time 12.5 days). RESULTS The reduction of volatile solids (VS) was 77% at 45 °C TPAD‐1 and 72% at 55 °C TPAD‐II. The accumulation of ammonia and volatile fatty acids (VFAs; propionic acid) were observed to be below the inhibitory range (>3000 mg L−1), whereas the methane (CH4) production (45 °C, 3.55 ± 0.47 L CH4 L−1 day−1; 35 °C, 1.44 ± 0.12 L CH4 L−1 day−1) remained considerably higher in TPAD‐I than TPAD‐II. Furthermore, the TPAD‐II system suffered from certain degree of instability due to high level of total VFAs (6087 ± 1578 mg L−1), low buffering capacity, increased level of total NH3 (2982 ± 219 mg L−1) and free NH3 (246 ± 25 mg L−1), and relatively reduced CH4 production (1.69 ± 0.1 L L−1 day). The bacterial and archaeal population of the TPADs investigated by 454 pyrosequencing and Illumina sequencing showed, in both TPAD systems, a bacterial community dominated by Firmicutes, followed by Bacteriodetes, Proteobacteria, Synergistetes and Actiniobacteria. The archaeal community was dominated by Methanimicrobia (74–84% Methanosarcina) and Methanobacteria (15–27% Methanobacterium). A progression from genus Clostridium to Coprothermobacter and Tepidanaerobacter, and Methanocarcina to Methanothermobacter and Methanobacterium was observed in TPAD‐II. CONCLUSIONS This study proved the processes driving the dynamics of key microbial population and its correlation with hydrolytic functionality of TPAD systems. © 2019 Society of Chemical Industry

Assessment of multiple anaerobic co-digestions and related microbial community of molasses with rice alcohol wastewater

“…Lee et al [54] also reported that the accumulation of propionic acid could decrease process performance and lead to process failure. Our results are in agreement with Lee et al [55] who stated that an alarming concentration of propionic acid is 1000-2000 mg/L and suggested that exceeding this limit can inhibit methanogens. In our study, we con rmed that using molasses as a sole substrate in anaerobic digestion, monitoring of propionic acid and total VFA should be determined periodically.…”

“…During this time, in MR35, an unexpected increase in abundance of Beijerinckiaceae from class alpha-proteobacteria and other uncultured bacterium was observed by suppressing the abundance of other families. Hameed et al [55] and Zhang et al [56] identi ed the genera beijerinckia and other related bacteria from the same family in anaerobic communities with stable acetoclastic methanogenesis (74-84%) that shows syntrophic association with methanogens. The bacteria related to family Beijerinkia are known for nitrogen reduction in the anaerobic system [56].…”

Shifts in the soil bacterial community along a salinity gradient in the Yellow River Delta

“…Thus, the microbial diversity and abundance are negatively affected in soils with a pH >7 and high Na + levels (Rath & Rousk, ). Additionally, increased K + could lower bacterial richness and diversity (Hameed et al, ). Different bacterial species show different levels of tolerance to specific ionic toxicity.…”

Role of Microbial Hydrolysis in Anaerobic Digestion

“…pH below 6.5 and thermophilic temperature decrease archaea diversity [3,39]. In a study of Hameed et al, the abundance of Methanosarcina-assumed to be a main producer of methane in biogas production-was reduced from 76.7% to 23.8%, and also the alpha diversity decreased with a shift from 35 • C to 55 • C [40]. As a diverse microbiome is assumed to be more stable, staging of AD leads to a better process performance.…”