Showing papers by "Peter Roslev published in 2021"

Degradation of the antifungal pharmaceutical clotrimazole by UVC and vacuum-UV irradiation: Kinetics, transformation products and attenuation of toxicity

Abstract: Azole fungicides are frequently detected as water contaminants due to extensive societal use, and these broad-spectrum antifungal chemicals can cause harmful effects in non-target organisms. Vacuum ultraviolet (VUV) treatment is an efficient and green technology that produces hydroxyl radical to remove contaminants from water. This study investigated the potential of UVC (254 nm) and combined VUV/UVC (185/254 nm) treatment to remove the widely used antifungal compound clotrimazole from water. Degradation kinetics, degradation mechanisms, and toxicity mitigation were investigated using a VUV photoreactor. Toxicity of clotrimazole to aquatic organisms before and after UV treatment were investigated using the luminescent bacterium Aliivibrio fischeri, the bioluminescent yeast Saccharomyces cerevisiae BLYR, the filamentous fungus Fusarium graminearum, the freshwater microalga Raphidocelis subcapitata, and the crustacean Daphnia magna. VUV irradiation efficiently degraded the persistent pollutant clotrimazole at elevated concentrations (mg/L) and at environmental concentrations (µg/L) with > 50% abatement in 1 min and > 95% removal within 32 min. VUV photolysis produced 8 transformation products manly resulting from drug hydroxylation in the phenyl ring and/or imidazole group followed by ring opening or loss of the imidazole moiety. Substantial decrease in aquatic toxicity was observed after UV treatment suggesting that VUV irradiation of aqueous clotrimazole generated less-toxic transformation products.

Survival of animal and human-associated Listeria monocytogenes in drinking water and biofilms

Abstract: Land slugs are occasionally observed as contaminants in groundwater wells and drinking water treatment plants including storage tanks. Slugs may feed on carrion and feces, and they are potential vectors of pathogens such as Listeria monocytogenes. We isolated L. monocytogenes from the pest slug Arion vulgaris and examined the persistence and survival of human- and slug-derived L. monocytogenes in groundwater-based drinking water and biofilms. L. monocytogenes survival was evaluated using cultivation and cultivation-independent techniques. L. monocytogenes remained culturable for 35–47 days in drinking water with first-order decay rates between 0.314 and 0.457 h−1 (T99 ≥10 days). Attachment of L. monocytogenes to filter sand delayed washout from drinking water filters and increased persistence 2–3-fold. Indigenous biofilms stimulated initial surface attachment 10–100-fold but L. monocytogenes declined more rapidly in drinking water biofilms compared with virgin filters not colonized by microorganisms. Grazing by protozoa likely attenuated L. monocytogenes survival in some drinking water biofilms. A comparable survival pattern was observed for L. monocytogenes and the fecal indicator bacterium E. coli. The study suggests that live L. monocytogenes can persist for weeks as sessile organisms in groundwater-based drinking water supplies and may subsequently be released to the drinking water.