Impact of salinity on anaerobic microbial community structure in high organic loading purified terephthalic acid wastewater treatment system

•1% NaCl effect on anaerobic terephthalic-degrading microbial consortia was studied.•Salinity had no significant effect on COD removal.•PT concentration impacted by salinity increased sharply up to 38.09 mg/L.•Acetic acid accumulation can be noticed due to salinity addition.•The predominant phylum changed from Planctomycetes to Proteobacteria. To investigate the effect of salinity (1% sodium chloride) on anaerobic microbial community structure in high strength telephthalic wastewater treatment system, the performances of anaerobic-aerobic process and the shifts of microbial community in anaerobic tank were studied and determined. Results showed that the chemical oxygen demand (COD) removal in the whole process remained above 90%. And the effluent concentrations of targeted pollutants were lower than 10 mg/L, other than para-toluic acid (PT, 38.09 mg/L). However, methane production significantly decreased compared to no salinity situation. This might be due to the inhibition of salinity on methanogens, which hindered the conversion of acetate to methane. Furthermore, the dominant genus in bacterial level changed from Tepidisphaera to Syntrophus, which facilitated the syntrophic association with hydrogenotrophic methanogens. The prevailed archaea remained acetoclastic Methanothrix above 90%. Therefore, the salinity on anaerobic microbial community structure mainly reflects in the methanogen process, remarkably decreasing methane production.