Abundance and removal of antibiotic resistant E. coli from urban wastewater in case of two Norwegian wastewater treatment plants

Summary

The effectivity of different treatment stages at two large wastewater treatment plants (WWTPs) located in Oslo, Norway, to remove antibiotic resistant E. coli from municipal wastewater was investigated. The WWTPs were effective in reducing the total cultivable E. coli. The E. coli in WWTP samples were partly resistant to ampicillin (6-27 %) and co-trimoxazole (5-24 %),and, to a lesser extent, tetracycline (3-14 %) and ciprofloxacin (0-7 %). In the first WWTP, a clear decrease in the percentage of E. coli resistant to these antibiotics was found, with the main removal occurring during physical/chemical treatment. In the second WWTP, the percentage of cultivable resistant E. coli did not display a considerable change. During lab-scale membrane filtration of WWTP effluents using ultrafiltration (UF) and nanofiltration (NF) membranes, all E. coli, including those resistant to antibiotics, were removed completely.