Antibiotic-resistant bacteria disinfection in untreated hospital wastewater using peracetic acid with short contact time

Abstract

The occurrence of antibiotic resistance in wastewater attracted interest in investigating the inactivation of antibiotic-resistant bacteria by various disinfecting agents. In this study, the removal of multi-resistant and ciprofloxacin-resistant bacteria from municipal and hospital untreated wastewater using peracetic acid (PAA) was studied. Pilot experiments were performed twice in each of two locations with untreated municipal wastewater and untreated hospital wastewater applying 25–150 mg L⁻¹ PAA with 1–10 min contact times. These contact times were selected in order to mimic the retention time of wastewater in a pipe running from a hospital to a municipal wastewater pipe before it mixes into municipal sewer networks. Batch experiments were conducted in parallel under the same experimental and wastewater conditions to verify the PAA dosage in the pilot experiments. The numbers of multi-resistant and ciprofloxacin-resistant bacteria were twenty and five times higher, respectively, in untreated hospital wastewater compared to untreated municipal wastewater. This difference in the level of ARB could be used to specify the disinfection requirements to reduce the ARB from hospital wastewater to the level of ARB in municipal wastewater by minimally 95%. PAA degradation was swift in the pilot and batch experiments, and no adverse effects were observed for the WWTP from the residual PAA. A similarity in the removal of ciprofloxacin-resistant bacteria from the pilot experiment and batch experiments performed in the laboratory was observed. The removal of resistant bacteria increased by increasing the contact time and PAA concentration. PAA was demonstrated to be an effective disinfectant able to minimize the risk of multi-resistant and ciprofloxacin-resistant bacteria in both municipal and hospital untreated wastewater.