Abstract
Doxycycline, an antibiotic, is largely used in human and veterinary medicine. The conventional treatment with activated sludge is not very efficient. Laccase appeared to be the main enzyme secreted essentially by white rot fungi as Trametes versicolor and Phlebia fascicularia on the degradation of xenobiotic compounds from the pharmaceutical industry. The main purpose of this study was to enhance the biodegradation of doxycycline through activated sludge combined with addition of glucose as a carbon co-substrate to improve the growth of the microbial population present in the activated sludge, phenol as a laccase mediator, copper as a cofactor and inductor for laccase production. The enhancement of the biodegradation of doxycycline was 50, 90, 68 and 83% greater respectively with the addition of glucose, copper, phenol and with a mixture of the compounds after 14 days of treatment at 25°C. Compared with the biotic control (activated sludge alone), a 30% increase for the test with the addition of phenol was observed.
Highlights
During the last few years, many studies have shown the importance of the treatment of micropollutants which are called emerging contaminants
Biosorption experiments The elimination of Doxycycline hyclate (DC) for 250 min is lower than 20 %, this shows the negligible DC biosorption on the activated sludge (Fig. 2), this can be explained by the value of the log Kow of DC, since for these values, the biosorption was reported to be very low (Naghdi et al, 2018)
At the same time, the Chemical Oxygen Demand (COD) value didn’t evolve. It means that despite the action of the activated sludge on the removal of the doxycycline, the by-products formed from initial doxycycline were not eliminated by activated sludge
Summary
During the last few years, many studies have shown the importance of the treatment of micropollutants which are called emerging contaminants. Pharmaceutical substances, personal care products, hormones, industrial chemicals, pesticides, and many other emerging compounds can be found in wastewater in trace concentrations, from a few ngL-1 to several μgL-1. Micropollutants in wastewater, unless properly treated, pose substantial risks to human health and the environment (Boonnorat et al, 2019; Wolff et al, 2018). Pharmaceuticals are used to cure, prevent or eliminate diseases in animals and humans. They are designed to resist biodegradation long enough to attain their beneficial effects, and this explains why they are resistant to biodegradation. Continuous input to the environment of these chemicals can lead to their accumulation in organisms and transfer of effects along natural food-chains (Corcoran et al, 2010). One main concern is that antibiotics promote the development and spread of resistant bacteria (Becker et al, 2016)
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