Impacts of different organophosphorus flame retardants on the transformation of phosphorus forms and microbial metabolic pathways in anaerobic reactors

Organophosphorus flame retardants are widely distributed in aquatic environment and wastewater treatment plants. However, their effect on biological wastewater treatment processes is not clear. The study was conducted to explore the impact of different types of organophosphorus flame retardants on the transformation of phosphorus forms, succession of microbial communities and microbial metabolic pathways in an anaerobic reactor. Results showed that the effect of tri(2-butoxyethyl) phosphate (TBEP) on COD removal in the anaerobic reactor was greater than that of tri(2-chloroethyl) phosphate (TCEP); this trend increased as the retardant concentration increased (2 mg/L to 5 mg/L). Within the predominant bacterial phyla were identified as Chloroflexi, Thermotogae, Euryarchaeota, and Proteobacteria. Chloroflexi had the highest relative abundance. The augmentation of TBEP and TCEP appeared to inhibit Proteobacteria growth. The total abundance of the phosphorus transport gene was lower in the experimental groups compared to the blank group, accounting for 0.268 % in the TBEP group, 0.278 % in the TCEP group, and 0.337 % in the blank group. This demonstrated that introducing TBEP obviously suppressed a phosphate transportation system's absorption and utilization of phosphorous. This study provides useful insights into the responses of the transformation of phosphorus forms, microbial community structure and metabolic pathways to TBEP and TCEP in anaerobic reactor.