Unveiling dynamics of microbial communities, species interactions, and ecological assembly during low-temperature-induced sludge bulking in full-scale wastewater treatment systems

This study investigated the microbial community characteristics and ecological mechanisms of floating sludge and suspended sludge in a full-scale wastewater treatment plant under low-temperature conditions. Floating sludge exhibited a lower proportion of positive correlations compared to suspended sludge (56.98 % vs. 61.03 %), indicating stronger competition within the microbial community. Null model analysis revealed the roles of deterministic and stochastic processes in shaping the microbial communities, with stochastic processes being dominant. However, deterministic selection played a larger role in floating sludge, highlighting stronger influence of species interactions and temperature fluctuations. Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis revealed stronger energy metabolism in floating sludge, while suspended sludge microbes were more active in material transport. This study reveals distinct microbial and ecological differences between floating and suspended sludge at low temperatures, providing theoretical support for optimizing wastewater treatment and controlling sludge bulking in cold climates.