Performances of simultaneous removal of trace-level ofloxacin and sulfamethazine by different ozonation-based treatments

Abstract

The optimization of ozonation for minimizing ozone use and energy consumption remains an important issue in practical engineering applications regarding removing antibiotics from secondary effluent of wastewater treatment plants. Within this context, the operating conditions of sole ozonation for simultaneous removal of OFC and SMT were firstly optimized in terms of cost-effectiveness, and the relatively optimized conditions were set as 4.0 mg/L of O3 and 1min of contact time with the removal efficiencies of 74.16 ± 2.21% and 99.89 ± 0.05% for OFC and SMT, respectively. The effects of two predominant components (i.e. dissolved organic matter (DOM) and nitrate (NO3−)) in secondary effluents on the ozonation of OFC and SMT were also investigated and demonstrated marked differences. DOM had adverse effects on the ozonation of OFC and SMT, and this inhibition could be mainly due to the DOM fractions reaction and transformation (HO→HiN) competing for O3 and ⋅OH with OFC and SMT. The presence of NO3− only inhibited OFC abatement and had little effect on SMT removal during ozonation. To reduce energy consumption for ozone generation and increase ozone mass transfer efficiency, the Fe-based catalysts (zero-valent iron (Fe0) and magnetite (Fe3O4)) were also adopted to explore the feasibility of simultaneous removal of OFC and SMT by catalytic ozonation. The addition of Fe0 and Fe3O4 could increase the OFC degradation by 44.21 ± 0.68% and 32.71 ± 0.95% with the dosages of 2.0 g/L of Fe0 and 2.5 g/L Fe3O4, respectively. However, the Fe-based catalysts demonstrated the varying inhibition effects on SMT degradation. The present work can hopefully assist in understanding of how and to what extent DOM and NO3− are involved in ozonation process as well as the rational use of ozonation-based treatment for polishing secondary effluent in practical engineering applications.