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Antibiotics are used extensively throughout the world and their presence in the environment has caused serious pollution. This review summarizes natural methods and enhanced technologies that have been developed for antibiotic degradation. In the natural environment, antibiotics can be degraded by photolysis, hydrolysis, and biodegradation, but the rate and extent of degradation are limited. Recently, developed enhanced techniques utilize biological, chemical, or physicochemical principles for antibiotic removal. These techniques include traditional biological methods, adsorption methods, membrane treatment, advanced oxidation processes (AOPs), constructed wetlands (CWs), microalgae treatment, and microbial electrochemical systems (such as microbial fuel cells, MFCs). These techniques have both advantages and disadvantages and, to overcome disadvantages associated with individual techniques, hybrid techniques have been developed and have shown significant potential for antibiotic removal. Hybrids include combinations of the electrochemical method with AOPs, CWs with MFCs, microalgal treatment with activated sludge, and AOPs with MFCs. Considering the complexity of antibiotic pollution and the characteristics of currently used removal technologies, it is apparent that hybrid methods are better choices for dealing with antibiotic contaminants.

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Ethylbenzene is classified as a priority pollutant; however, toxicity data, especially those regarding sublethal toxicity, are rarely reported on gastropods. The present work was performed to elucidate the sublethal effects of ethylbenzene using a freshwater snail, Bellamya aeruginosa (Reeve), exposed to ethylbenzene for 21 days followed by a 17-day recovery period. Superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), reduced glutathione (GSH), and malonyldialdehyde (MDA) were used as biomarkers to evaluate oxidative stress in hepatopancreas of snails. In addition, alkaline comet assay was applied to determine the genotoxicity of ethylbenzene in hepatopancreas of snails. These biomarkers and DNA damage exhibited various responses to ethylbenzene in the tested snails. SOD and CAT activities were almost significantly stimulated during the exposure period. As exposure time was prolonged beyond 7 days, CAT activity gradually became significantly increased at higher doses of ethylbenzene. GSH concentration was positively and linearly related with exposure dose. MDA concentration was significantly greater than that in the control only under the lowest treatment after a 7-day exposure. Alkaline comet assay showed that ethylbenzene could significantly induce DNA damage in hepatopancreas of snails, and there was a good dose- and time-response in DNA damage, indicating potential genotoxicity of ethylbenzene on snails. At the end of the recovery period, the repair of DNA damage was not yet completed, showing that DNA repair requires more time. The findings from this study could indicate that SOD, GST, and GSH seem to be effective oxidative biomarkers for snails exposed to ethylbenzene in the short term. CAT proved to be a valuable discriminating biomarker in subchronic exposure to ethylbenzene, but MDA was not a suitable oxidative biomarker for exposure to ethylbenzene in either the short or long term. Alkaline comet assay was efficient tool with which to evaluate the potential genotoxicity of ethylbenzene.

No abstract