Mineral-Based Advanced Oxidation Processes for Enhancing the Removal of Antibiotic Resistance Genes from Domestic Wastewater

Wastewater treatment plants (WWTPs) release antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) into the environment. Advanced oxidation processes (AOPs) can remove ARB and ARGs, but they often require impractically high chemical or energy use. Here, we explore a low-energy AOP that uses Fe-bearing clay mineral (NAu-1) either combined with H₂O₂ (H₂O₂/NAu-1) or as prereduced structural Fe (rNAu-1) to degrade selected ARGs (i.e., <i>tet</i>M, <i>tet</i>Q, and <i>bla</i> _OXA-10), <i>int</i>1 (a mobile genetic element), and the 16S rRNA gene in postsecondary WWTP effluents. Addition of H₂O₂/NAu-1 significantly increased <i>tet</i>M and <i>int</i>1 removals relative to UV irradiation and H₂O₂/UV (<i>p</i> ≤ 0.02). Removals increased with greater H₂O₂ doses and contact times, reaching maximum values of 1.2 and 2.3 log units at H₂O₂ doses of 0.26 and 10 mM and contact times of 4 and 8 h, respectively. Bacterial regrowth after 24 h of contact was probably due to H₂O₂ depletion. However, the addition of rNAu-1 achieved the highest removals, up to 2.9 log units after 0.5 h, and suppressed bacterial regrowth over 24 h. Similar removals were observed with rNAu-1 under oxic and anoxic conditions. Results show that mineral-based AOPs offer the potential for elevated ARG removal and lower chemical and energy demands in tertiary wastewater treatment.