Impact of the Fenton pretreatment on enhanced biological phosphorus removal: emphasizing variations in microbial community and metabolism.

The enhanced biological phosphorus removal (EBPR) process is widely used to remove inorganic phosphorus from wastewater. Phosphorus-accumulating organisms (PAOs) play a central role in this process. However, for wastewater containing organic phosphorus, a pretreatment oxidation step is necessary to convert organic phosphorus into inorganic forms before EBPR. In this study, a combined system consisting of a Schorl/H2O2 oxidation unit and an EBPR reactor was established to treat fosfomycin, an organophosphorus antibiotic. After the addition of the Schorl/H2O2 oxidation influent, the phosphorus accumulation in the EBPR system decreased significantly from 98.12 to 11.08 mg/L. High-throughput sequencing was employed to investigate the microbial community and functional genes in the EBPR system. The significant inhibition of phosphorus removal was mainly attributed to a shift in the dominant microbial species. Specifically, the abundance of the inorganic phosphate remover Casimicrobium_huifangae dropped from 13.6 to 2.3%. In contrast, the abundance of the organophosphorus degrader Acidovorax_sp._KKS102 increased from 0.8 to 14.3%. Correspondingly, the abundance of key functional genes (PPK2, yjcG, PhaC) involved in phosphate accumulation and phosphorus release decreased. Metabolic pathway analysis further indicated that the Schorl/H2O2 oxidation effluent markedly enhanced the abundance of peroxisomes, which help mitigate oxidative stress. It also enriched pathways related to phosphonate and phosphinate metabolism. This study provides novel insights into the integrated application of advanced oxidation and EBPR for organic phosphorus removal and offers technical guidance for future process design.