The role of microbial ecology in improving the performance of anaerobic digestion of sewage sludge

Abstract

The use of next-generation diagnostic tools to optimise the anaerobic digestion of municipal sewage sludge has the potential to increase renewable natural gas recovery, improve the reuse of biosolid fertilisers and help operators expand circular economies globally. This review aims to provide perspectives on the role of microbial ecology in improving digester performance in wastewater treatment plants, highlighting that a systems biology approach is fundamental for monitoring mesophilic anaerobic sewage sludge in continuously stirred reactor tanks. We further highlight the potential applications arising from investigations into sludge ecology. The principal limitation for improvements in methane recoveries or in process stability of anaerobic digestion, especially after pre-treatment or during co-digestion, are ecological knowledge gaps related to the front-end metabolism (hydrolysis and fermentation). Operational problems such as stable biological foaming are a key problem, for which ecological markers are a suitable approach. However, no biomarkers exist yet to assist in monitoring and management of clade-specific foaming potentials along with other risks, such as pollutants and pathogens. Fundamental ecological principles apply to anaerobic digestion, which presents opportunities to predict and manipulate reactor functions. The path ahead for mapping ecological markers on process endpoints and risk factors of anaerobic digestion will involve numerical ecology, an expanding field that employs metrics derived from alpha, beta, phylogenetic, taxonomic, and functional diversity, as well as from phenotypes or life strategies derived from genetic potentials. In contrast to addressing operational issues (as noted above), which are effectively addressed by whole population or individual biomarkers, broad improvement and optimisation of function will require enhancement of hydrolysis and acidogenic processes. This will require a discovery-based approach, which will involve integrative research involving the proteome and metabolome. This will utilise, but overcome current limitations of DNA-centric approaches, and likely have broad application outside the specific field of anaerobic digestion.

Effects of Temperature Shifts on Microbial Communities and Biogas Production: An In-Depth Comparison

“…In the present study, we demonstrated the capability of Methanosaeta to exist in both mesophilic and thermophilic conditions and its resiliency in surviving temperature changes while becoming the most predominant biogas producer via an acetoclastic pathway. This finding strengthens the earlier discovery that the abundance of acetoclastic methanogen (such as Methanosaeta) can provide reliable CH 4 production and stability indicators [48]. Instead of temperature, the metabolic shift of abundance from Methanosaeta to Methanosarcina may occur if Methanosaeta cannot produce methane due to specific environmental changes such as acetate availability, decreasing pH, increasing organic loading rates, high levels of salts, and ammonia nitrogen [6,49,50].…”

Source-Separated Industrial Wastewater Is a Candidate for Biogas Production through Anaerobic Digestion

“…The other factor affecting the extent of foaming is the presence of certain microbes and the biosurfactants and hydrophobic substances they produce [9]. Gordonia, a genus implicated in wastewater digester foaming [47,123], was detected from the beginning of the acclimatisation period until foaming event B. Microthrix was also identified but steadily decreased in relative abundance throughout the digestion period [40].…”

“…The extent and stability of digestion, and therefore the composition and volume of biogas, are affected by a range of parameters, including design decisions such as reactor configuration [6], temperature [7,8], and retention time [8], together with chemical properties of the feedstock and reaction medium, such as pH and elemental balance, and the microbial community [9].…”

Succession from acetoclastic to hydrogenotrophic microbial community during sewage sludge anaerobic digestion for bioenergy production

“…The generalist groups can perform similar ecological functions in a reactor and this redundancy ensures that even when the environmental conditions change, the ecosystem will stay functional, because its functional niches are occupied (Krohn et al 2022;Zhu et al 2020).…”