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The COVID-19 outbreak has forced countries to introduce severe restrictive measures to contain its spread. In particular, physical distancing and restriction of movement have important consequences on human behaviour and potentially also on illicit drug use and supply. These changes can be associated with additional risks for users due to reduced supplies, limited prevention and harm reduction activities. Furthermore, there have been limitations in the amount of data about drug use which can be collected due to restrictions. To goal of this study was to obtain information about potential changes in illicit drug use impacted by COVID-19 restrictions. Wastewater samples were collected in seven cities in the Netherlands, Belgium, Spain and Italy at the beginning of lockdowns (March-May 2020). Using previously established and validated methods, levels of amphetamine (AMP), methamphetamine (METH), MDMA, benzoylecgonine (BE, the main metabolite of cocaine) and 11-nor-9-carboxy-Δ 9 -tetrahydrocannabinol (THC-COOH, main metabolite of tetrahydrocannabinol (THC)) were measured and compared with findings from previous years. Important differences in levels of consumed drugs were observed across the considered countries. Whilst for some substances and locations, marked decreases in consumption could be observed (e.g., 50% decrease in MDMA levels compared to previous years). In some cases, similar or even higher levels compared to previous years could be found. Changes in weekly patterns were also observed, however these were not clearly defined for all locations and/or substances. Findings confirm that the current situation is highly heterogeneous and that it remains very difficult to explain and/or predict the effect that the present pandemic has on illicit drug use and availability. However, given the current difficulty in obtaining data due to restrictions, wastewater analysis can provide relevant information about the situation at the local level, which would be hard to obtain otherwise.

Some pollutants can be resistant to wastewater treatment, hence becoming a risk to aquatic and terrestrial biota even at the very low concentrations (ng L-μg L) they are commonly found at. Tertiary treatments are used for micropollutant removal but little is known about the ecotoxicity of the treated effluent. In this study, a municipal secondary effluent was treated by a solar photo-Fenton reactor at initial neutral pH in a raceway pond reactor, and ecotoxicity was evaluated before and after micropollutant removal. Thirty-nine micropollutants were identified in the secondary effluent, mainly pharmaceuticals, with a total concentration of ≈80 μg L. After treatment, 99 % microcontaminant degradation was reached. As for ecotoxicity reduction, the assayed organisms showed the following sensitivity levels: Tetrahymena thermophila > Daphnia magna > Lactuca sativa > Spirodela polyrhiza ≈ Vibrio fischeri. The initial effluent showed an inhibitory effect of 40 % for T. thermophila and 20 % for D. magna. After 20 min of photo-Fenton treatment, no toxic effect was observed for T. thermophila and toxicity dropped to 5 % for D. magna. Graphical abstract Ecotoxicity removal by solar photo-Fenton at neutral pH. ᅟ.

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