Unraveling EPS-SMP dynamics and microbial interactions in full-scale MBR system

This study aims to investigate the dynamic relationship between extracellular polymeric substances (EPS), soluble microbial products (SMP), and microbial communities in different sludge types of a full-scale membrane bioreactor (MBR) system treating wastewater. Over a 65-day sampling period, EPS-SMP fractions and microbial community were characterized in both aerobic and anoxic sludge samples. Results of the study revealed that polysaccharide-rich EPS (533 mg/L) and total SMP (1,106 mg/L) predominated in aerobic environments, whereas anoxic conditions fostered elevated proteinaceous and polysaccharide-rich SMP fractions with total SMP (1,235 mg/L), contributing to membrane fouling. Nitrospira and Nitrosomonas were positively correlated (r > 0.99, p < 0.05) with polysaccharide and protein fractions which indicates their functional role in promoting biofilm stability and facilitating nutrient turnover under different oxygen levels. Conversely, the negative correlation (r > 0.99, p < 0.05) with Firmicutes and proteinaceous SMP and EPS under anoxic conditions, underlining their potential impact on sludge properties. These findings provide a molecular and ecological perspective for optimizing MBR operations, specifically for mitigating fouling and enhancing nutrient removal efficiency in wastewater treatment systems.