Drivers of microbial community composition in mesophilic and thermophilic temperature-phased anaerobic digestion pre-treatment reactors

• Published in: Water research (Oxford) 2013-12, Vol.47 (19), p.7098-7108
• Main Authors: Pervin, Hasina M., Dennis, Paul G., Lim, Hui J., Tyson, Gene W., Batstone, Damien J., Bond, Philip L.
• Format: Article
• Language: English
• Subjects: activated sludge; anaerobic digestion; Anaerobiosis; bacterial communities; Bioreactors - microbiology; community structure; Coprothermobacter; digestion; DNA libraries; Firmicutes; fluorescence in situ hybridization; genes; Gram-Negative Anaerobic Bacteria - genetics; Gram-Positive Endospore-Forming Rods - genetics; hydrolysis; Hydrolysis–fermentation; In Situ Hybridization, Fluorescence; Microbial Consortia - genetics; Microbial Consortia - physiology; Molecular microbial ecology; new technology; pathogens; Polymorphism, Restriction Fragment Length; pretreatment; Proteobacteria; ribosomal RNA; RNA, Ribosomal, 16S; sequence analysis; Sewage - microbiology; sewage sludge; Temperature; Temperature-phased anaerobic digestion; Thermophilic pre-treatment; Time Factors; Waste Disposal, Fluid - instrumentation; Waste Disposal, Fluid - methods
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2013.07.053

Temperature-phased anaerobic digestion (TPAD) is an emerging technology that facilitates improved performance and pathogen destruction in anaerobic sewage sludge digestion by optimising conditions for 1) hydrolytic and acidogenic organisms in a first-stage/pre-treatment reactor and then 2) methogenic populations in a second stage reactor. Pre-treatment reactors are typically operated at 55–65 °C and as such select for thermophilic bacterial communities. However, details of key microbial populations in hydrolytic communities and links to functionality are very limited. In this study, experimental thermophilic pre-treatment (TP) and control mesophilic pre-treatment (MP) reactors were operated as first-stages of TPAD systems treating activated sludge for 340 days. The TP system was operated sequentially at 50, 60 and 65 °C, while the MP rector was held at 35 °C for the entire period. The composition of microbial communities associated with the MP and TP pre-treatment reactors was characterised weekly using terminal-restriction fragment length polymorphism (T-RFLP) supported by clone library sequencing of 16S rRNA gene amplicons. The outcomes of this approach were confirmed using 454 pyrosequencing of gene amplicons and fluorescence in-situ hybridisation (FISH). TP associated bacterial communities were dominated by populations affiliated to the Firmicutes, Thermotogae, Proteobacteria and Chloroflexi. In particular there was a progression from Thermotogae to Lutispora and Coprothermobacter and diversity decreased as temperature and hydrolysis performance increased. While change in the composition of TP associated bacterial communities was attributable to temperature, that of MP associated bacterial communities was related to the composition of the incoming feed. This study determined processes driving the dynamics of key microbial populations that are correlated with an enhanced hydrolytic functionality of the TPAD system. Variation in bacterial community composition in the thermophilic digestion (TP) was attributed to reactor temperature. [Display omitted] •Enhanced anaerobic digestion is achieved in a TPAD system.•Increased temperature drives microbial community composition changes.•Particular bacteria were dominant when enhanced digestion occurred.