Fenton oxidation treatment of benzalkonium chlorides to prevent antibiotic resistance development in non-acclimated activated sludge system

Abstract

Improper discharge of benzalkonium chlorides (BAC) to sewage and wastewater treatment plants can cause acute intoxication and chronic low-dose exposure, which can lead to changes in microbial communities and can promote the development of antibiotic resistance. The aim of this study was to develop a feasible treatment strategy based on the homogeneous Fenton oxidation to minimize the negative impact of BAC-containing wastewater on activated sludge systems. The effect of initial iron and oxidant concentrations was analyzed. After an initial Fenton oxidation stage (180 min), the solution needed to be stored at ambient temperature and in the dark for some time to remove residual oxidizing agents and promote further oxidation. The 0.1 % w/v-BAC solution treated at best operating conditions, i.e., homogeneous Fenton for 180 min at 30 °C, pH0 = 3, stoichiometric oxidant dose, [Fe+2]0:[H2O2]0 = 0.011, and stored during 4 days, led to BAC conversion of 99.9 %, no residual H2O2, no sludge, and DOC conversion of 40.8 %. An increase in metabolic activity was observed when non-acclimated activated sludge was exposed to the treated solution. Treated solution showed biodegradation without increasing resistance to Ampicillin, Cephalexin, or Ciprofloxacin. Evaluation of the effect of water matrix (tap or distilled) showed that the composition of tap water enhanced the oxidation extent, resulting in a 15 % increase in mineralization and a further reduction of COD. This study provides insights into the treatment of wastewater containing BAC and its safe discharge to sewage systems or biological wastewater treatment plants.