Effect of Philodina erythrophthalma and its secretion on the performance of activated sludge in sequencing batch reactor for wastewater treatment

This study explores the impact of Philodina erythrophthalma (rotifers) and its secretions on the performance of activated sludge in biological sewage treatment. The effects were assessed by comparing three reactors: a control (C) reactor without rotifers, a reactor with rotifers (R), and a reactor with rotifer secretions (RS). At 12 hr, chemical oxygen demand (COD) removal efficiency was 70.5%, 79.1%, and 82.5% for C, R, and RS reactors, respectively. The removal efficiencies of total organic carbon, ammonia nitrogen, total nitrogen, and total phosphorus demonstrated consistent trends with the COD removal rate. Moreover, the treatment performance of the R reactor was comparable to that of the RS reactor. By the 10th day, the removal rates of pollutants in each reactor had reached a relatively high level, and the differences among the reactors had decreased. Microbial community analysis revealed that adding rotifers and their secretions led to a modest increase in species richness, but did not induce significant changes in overall microbial diversity. These findings suggest that rotifers may influence the microbial community through their secretions, thereby enhancing the biological treatment efficiency, and the improvement was more significant when the reactor's treatment performance was lower. • The impact of rotifers and their excretions on the SBR treatment was investigated. • Rotifers and their secretions improved pollutant removal in low-treatment phase. • Rotifers or their excretions did not change microbial communities. • The impact of rotifers on the SBR treatment is mediated by their secretion.