Enhanced sulfamethoxazole removal using anaerobic and aerobic sequencing batch reactor with magnetite

Abstract

Sulfamethoxazole (SMX) is one of the most frequently used antibiotics. The capacity of conventional wastewater treatment plants to remove such antibiotics is limited, posing a risk of antibiotic resistance genes spreading into the environment. In this study, to carry out biological Fenton reaction under neutral conditions, an anaerobic and aerobic sequencing batch reactor (SBR) supplemented with magnetite was proposed. This process aims to enhance the treatment of antibiotics in addition to organic pollutants such as chemical oxygen demand (COD) without external addition of hydrogen peroxide (H2O2). Mixed anaerobic and aerobic sludge was exposed to alternative anaerobic and aerobic conditions in two identical SBRs with and without magnetite to treat the synthetic wastewater containing 1 mg·L sulfamethoxazole. The experimental results showed that the H2O2 level increased to 34.9 μM under aerobic conditions in the system with magnetite, and similar COD removal was observed in both SBRs. Moreover, enhanced SMX treatment was observed in the SBR with magnetite, while removal efficiencies of SMX gradually decreased in the SBR without magnetite. The experimental results demonstrate that H2O2 generation under aerobic conditions and biological Fenton reaction that can produce hydroxyl radicals led to the enhanced treatment of SMX in the SBR with magnetite. Magnetite as the catalyst was not dissolved during the redox process, indicating the possibility of its reusability. Further studies are needed to analyse the reaction mechanisms and the kinetics in the proposed SBR.