Towards oxidoreductase-based processes for the removal of antibiotics from wastewater

The occurrence of antibiotics in surface waters is an alarming issue that can be addressed by advanced wastewater treatment technologies. Among them, enzymatic treatment is an emerging technology claimed to provide prospective benefits in terms of efficiency, controllability, and safety. This review illustrates the current state of research focused on enzyme-based approaches for pollutant abatement, specifically on the most critical classes of antibiotics (e.g. tetracyclines, sulfonamides, fluoroquinolones). In addition to providing an overview of the efficiency both in terms of compound removal as well as toxicity reduction, we critically analyze if selected reaction conditions, such as the pH, temperature and water matrix are representative for real-case scenarios. Enzyme immobilization strategies onto inorganic, organic and composite materials are analyzed in terms of their effect on enzyme stability and activity. Their feasibility to be applied in future processes was also evaluated. We found that adequate kinetic description of target compound removal by sufficiently detailed models is still scarce even though it will be key for successful conceptualization of treatment processes. Considering that only a few studies have been conducted at scales above 100 mL, we present the investigated reactor configurations which are at the forefront of further scale-up. The systematic approach presented in this manuscript, which aims to critically evaluate the feasibility to implement enzymatic processes for the removal of antibiotics, can be adapted for other types of recalcitrant compounds targeted by oxidoreductases. Intensified research in the recommended areas will contribute to the development of enzyme-based processes which can complement other advanced wastewater treatment processes.

Graphical abstract