Enhanced nitrogen and phosphorus removal from mining-affected waters by micro–nano aeration coupled with microbial remediation

Nitrogen and phosphorus enrichment in mining-affected waters can cause oxygen depletion, eutrophication, and deterioration of aquatic ecosystems. In this study, a combined micro–nano aeration and microbial remediation strategy was developed for nutrient removal from mining-affected water. Field investigation showed that the mining water was black and odorous, with low dissolved oxygen and elevated nitrogen and phosphorus concentrations. Simulated mining-affected wastewater was therefore prepared according to the measured field-water characteristics to ensure experimental reproducibility. The effects of aeration duration, aeration pressure, microbial activation method, inoculation dosage, and initial pH on nutrient removal were systematically evaluated. The optimal operating conditions were identified as micro–nano aeration at 0.25 MPa for 3 h, microbial inoculation at 15 mL/L, and an initial pH of 7. Under these conditions, the combined micro–nano aeration–microbial system achieved removal efficiencies of 76.70% for NH3–N, 75.84% for TN, and 73.64% for TP within 3 days, outperforming the single aeration and microbial treatments. The enhanced performance was mainly associated with improved oxygen availability and possible microbial nutrient transformation under micro–nano aeration conditions, although the detailed nitrogen and phosphorus transformation pathways require further verification. These results suggest that micro–nano aeration can alleviate oxygen limitation and strengthen microbial remediation of nutrient-polluted mining waters, providing a potential low-impact approach for ecological restoration in mining areas.