Effect of UVA/LED/TiO2 photocatalysis treated sulfamethoxazole and trimethoprim containing wastewater on antibiotic resistance development in sequencing batch reactors

Abstract Controlling of antibiotics is the crucial step for preventing antibiotic resistance genes (ARGs) dissemination; UV photocatalysis has been identified as a promising pre-treatment technology for antibiotics removal. However, information about the effects of intermediates present in the treated antibiotics wastewater on the downstream biological treatment processes or ARGs development is very limited. In the present study, continuous UVA/LED/TiO 2 photocatalysis removed more than 90% of 100 ppb sulfamethoxazole (SMX)/trimethoprim (TMP), the treated wastewater was fed into SBR systems for over one year monitoring. Residual SMX/TMP (2–3 ppb) and intermediates present in the treated wastewater did not adversely affect SBR performance in terms of TOC and TN removal. SMX and TMP resistance genes ( sul I, sul II, sul III, dfr II, dfr V and dfr 13) were also quantified in SBRs microbial consortia. Results suggested that continuous feeding of treated SMX/TMP containing wastewaters did not trigger any ARGs promotion during the one year operation. By stopping the input of 100 ppb SMX/TMP, abundance of sul II and dfr V genes were reduced by 83% and 100%, respectively. sul I gene was identified as the most persistence ARG, and controlling of 100 ppb SMX input did not achieve significant removal of sul I gene. A significant correlation between sul I gene and class 1 integrons was found at the level of p = 1.4E-10 (r = 0.94), and sul II gene positively correlated with the plasmid transfer efficiency (r = 2.442E-10, r = 0.87). Continuous input of 100 ppb SMX enhanced plasmid transfer efficiency in the SBR system, resulting in sul II gene abundance increasing more than 40 times.