A novel aerobic denitrifying phosphate-accumulating bacterium efficiently removes phthalic acid ester, total nitrogen and phosphate from municipal wastewater

Simultaneous removal of nitrogen, phosphate and emerging pollutants are critical for safe reuse of wastewater, but research in this field is limited. In the present study, a novel aerobic denitrifying phosphate-accumulating bacterial strain RL-GZ01 was found to be able to utilize phthalic acid esters (PAEs) as carbon resource for cell growth. Based on 16S rRNA gene analysis, physiological and biochemical characterization, and genome-based average nucleotide identity calculation, RL-GZ01 was identified as Rhodococcus pyridinivorans. Strain RL-GZ01 showed high DEHP degradation in alkaline conditions and good tolerance of salinity and organic solvents. The degradation of DEHP by RL-GZ01 fitted well with a modified Gompertz model (R-2 = 0.9985). Metabolic intermediates of DEHP were identified via UHPLC-MS/MS analysis and the catabolic pathway was proposed thereafter. Genes and gene clusters contributed to the utilization of DEHP were analyzed through genomic analysis. Analysis of KEGG nitrogen metabolism pathway indicated that nitrate and nitrite were further transformed into ammonium which was further used for the biosynthesis of L-glutamine and L-glutamate. Strain RLGZ01 was further identified as a denitrifying phosphate accumulating organism which can accumulate phosphate by generating polyphosphate. Finally, strain RL-GZ01 was applied to municipal wastewater treatment for simultaneous removal of nitrogen, phosphate and DEHP. The removal percentages of DEHP (5 mg/L), TN (71.2 mg/L), NH4+-N (70.9 mg/L), PO43--P (10.89 mg/L) and COD (622.4 mg/L) by strain RL-GZ01 were 89.94 %, 64.45 %, 64.94 %, 76.30 % and 63.23 % within 84 h, respectively. These demonstrated the capability of strain RL-GZ01 for the biological treatment of wastewater containing PAEs.

Automated summary

In this study, a novel aerobic denitrifying phosphate-accumulating bacterial strain RL-GZ01 was found to be capable of utilizing phthalic acid esters (PAEs) as a carbon resource for cell growth and showed efficient degradation of di(2-ethylhexyl)phthalate (DEHP) under alkaline conditions. The metabolic intermediates of DEHP were identified and a degradation pathway was proposed. Moreover, strain RL-GZ01 was able to accumulate phosphate and achieve simultaneous removal of nitrogen, phosphate, and DEHP. The removal percentages of DEHP (5 mg/L), TN (71.2 mg/L), NH4+-N (70.9 mg/L), PO43--P (10.89 mg/L), and COD (622.4 mg/L) by strain RL-GZ01 were 89.94%, 64.45%, 64.94%, 76.30%, and 63.23% within 84 hours, respectively.