Advanced wastewater treatment with ozonation and granular activated carbon filtration: Inactivation of antibiotic resistance targets in a long-term pilot study

The inactivation of antibiotic resistant bacteria (ARB) and genes (ARGs) in an advanced plant combining ozonation and granular activated carbon (GAC) filtration applied for effluent after conventional activated sludge treatment at a full-scale urban wastewater treatment plant was investigated for over 13 consecutive months. The nitrite compensated specific ozone dose ranged between 0.4 and 0.7 g O 3 /g DOC with short-time sampling campaigns (0.2–0.9 g O 3 /g DOC). Samples were analysed with culture-dependent methods for bacterial targets and with qPCR for genes. The log removal values were correlated with a decrease of the matrix UV absorption at 254 nm (ΔUV 254 ) and indicated a range of ΔUV 254 that corresponds to a sufficient membrane damage to affect DNA. For trimethoprim/sulfamethoxazole resistant E. coli , sul 1, erm B and tet W, this phase was observed at ΔUV 254 of ~30 % (~0.5 g O 3 /g DOC). For ampicillin resistant E. coli and bla TEM-1 , it was observed around 35–40 % (~0.7 g O 3 /g DOC), which can be linked to mechanisms related to oxidative damages in bacteria resistant to bactericidal antibiotics. GAC treatment resulted in a further abatement for trimethoprim/sulfamethoxazole E. coli , sul 1 and tet W, and in increase in absolute and relative abundance of erm B and bla TEM-1 . • Ozonation and GAC were evaluated for ARB and ARGs abatement in a long-term study. • Ozone doses ≥ 0.6 g O 3 /g DOC were required to affect tested DNA targets. • Ampicillin resistant E. coli was less susceptible to ozonation effects than other ARB. • A relative abundance of bla TEM-1 gene increased after GAC treatment. • ΔUV 254 was tested as a proxy parameter to indicate DNA damage by ozone.