Enzymatic and electrochemical oxidation of emerging contaminants
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Emerging contaminants, also known as chemicals of emerging concern (CoCs), have been widely detected in water systems, and are under intensive research because of their potential risks to human health and the environment. Developing cost-effective and environmentally friendly remediation technologies is in urgent demand to address the risks of CoCs. Enzyme catalyzed oxidative humification reaction (ECOHR) is an enhanced natural process that is capable of degrading numerous recalcitrant organic compounds with the presence of oxidative enzyme and mediators. This study reported that the water extract of a natural matter, soybean meal, can be used as a cost-effective mediator solution, which facilitated the degradation of sulfadimethoxine in water via ECOHR, leading to over 95% removal in six hours. Several phenolic compounds were identified as the key mediators, and the transformation pathway of sulfadimethoxine as well as the toxicity of the treated solutions were studied. Other than being used as a standalone remediation technology, ECOHR can be coupled with other in situ adsorption technique to promote the degradation of contaminants on the sorbents. Our data showed that over 30% of a persistent CoC, perfluorooctanoic acid (PFOA), was removed in batch reactor with granular activated carbon and enzyme added to induce ECOHR after 60 days of incubation. This study also investigated the electrochemical oxidation of tetracycline using a novel ceramic electrode named Magnéli phase Ti4O7 electrode. The concentration of tetracycline spiked in solution was significantly reduced (>90%) in the electrolysis reactor after several hours, and its antibiotic activity also reduced as evidenced by antibiotic susceptibility test. In addition, electrochemical treatment was found to be a promising point of use water disinfection technology in an experiment that demonstrated the inactivation of E Coli spiked in water by 5 log using an electrochemical filtration device equipped with Magnéli phase Ti4O7 electrode. The data collected in this study showed that certain environmentally friendly enzymatic or electrochemical oxidation processes can effectively degrade or inactivate COCs, including antibiotics, per- and polyfluoroalkyl substances, and pathogens, and thus hold promise in being used as novel schemes in remediation or treatment to address the risks posed by emerging contaminants.