An adaptable, low-cost, and easy-to-operate biological treatment system for pollutant abatement in aquaculture water at the field pond scale needs to be developed. In this study, the pollutant removal capacity of a stable bioreactor for aquaculture wastewater was assessed, and the related mechanism was elucidated via an analysis of the microbial community’s characteristics and functions. The average removal efficiencies of chemical oxygen demand, suspended solids, total nitrogen, and total phosphorus were 40%, 86.22%, 38.62%, and 53.74%, respectively. The effluent quality meets the Requirement for Water Discharge from Freshwater Aquaculture Pond, SC/T9101-2007. The results indicate that the fillers under anaerobic conditions could attract Denitratisoma and unclassified_Rhodocyclaceae, promoting the denitrification reaction. This aligns with the characteristic that total nitrogen in aquaculture sewage mainly exists in the form of nitrate nitrogen. An anaerobic atmosphere helps degrade organic contaminants at liquid interfaces and remove nitrogen in the solid phase. The fillers under anaerobic conditions could attract Bacteroidota and promote the production of polysaccharides to form biofilms, which may be associated with phosphorus removal. The results indicate that the anaerobic stage can promote the formation of biofilm on the fillers to remove pollutants, thus achieving higher aquaculture sewage treatment efficiency.

Nitrogen loss during manure composting reduces the fertilizer value of the final product and increases its environmental burden. This study evaluated whether semi-permeable membrane covering could reduce gaseous emissions and promote mineral-N retention during the co-composting of swine manure and spent mushroom substrate. Conventional aerobic composting (AC) and semi-permeable membrane-covered aerobic composting (MCAC) were conducted for 35 d. Compared with AC, MCAC reduced the estimated cumulative emissions of NH₃, N₂O, and CH₄ by 53.1%, 34.1%, and 45.7%, respectively, and lowered the estimated direct global warming potential of direct CH₄ and N₂O emissions by 37.5%. On day 35, MCAC had higher NH₄⁺-N (530.5 vs. 172.0 mg kg⁻¹) and NO₃⁻-N concentrations (80.1 vs. 42.6 mg kg⁻¹) than AC. Total nitrogen concentration decreased by 14.98% in MCAC and 17.82% in AC from day 1 to day 35. Composting stage explained 33.95% of bacterial community variation, versus 5.71% for membrane covering. Metagenomic nitrogen-cycling profiles varied mainly over time, with higher ammonia-oxidation potential in MCAC on day 10. Profiles covaried mainly with moisture and inorganic nitrogen. Overall, semi-permeable membrane covering maintained thermophilic composting while reducing gaseous emissions. The lower NH₃ and N₂O emissions, together with the higher final NH₄⁺-N and NO₃⁻-N concentrations, indicate reduced gaseous N release and greater mineral-N retention under MCAC.