Occurrence and transformation of illicit drugs in wastewater treatment plants.

Illicit drugs (IDs) and their metabolites have been recently recognized as a new group of water emerging contaminants (ECs) with potent psychoactive properties and unknown effects to the aquatic environment (Pal et al., 2013). IDs are excreted via urine and feces and arrive at wastewater treatment plants (WWTPs) where can reach ppb levels (Castiglioni et al., 2006). Over the past few years, it has been demonstrated that conventional biological processes in WWTPs are not or scarcely able to remove IDs. Thus, they are discharged into water bodies through the treated effluent (Postigo et al., 2011). Therefore, monitoring the IDs concentration in WWTPs can have a twofold advantage: i. increase knowledge on the amount of IDs discharged in the environment and estimate their effect; ii. estimating indirectly the community level consumption (Senta et al., 2014). The objective of this paper is to provide a comprehensive analysis of the occurrence and behaviour of illicit drugs and their metabolites in two Sicilian WWTPs. Specifically, two WWTPs (namely, WWTP-1 and WWTP-2) located at the north-western Sicilian coast have been monitored for 5 months (one sampling per week). The two WWTPs have a conventional scheme and mainly differ for their potentiality. Indeed, the average daily flow expressed as m3d-1 for WWTP-1 and WWTP-2 was equal to 153,600 and 19,704, respectively. Samples were analyzed for total suspended solids (TSS), illicit drugs and their metabolites (metham-phetamine; COC = cocaine; MDMA = 3,4-methylenedioxymethamphetamine; METH = methadone; EDDP = 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine; MDA = 3,4-methylenedioxy amphetamine; MDEA = 3,4-methylenedioxy ethylamphetamine; THC-COOH = 11-nor-9-carboxy-Δ9-tetrahydrocannabinol; BEG= Benzoylecgonine). In order to provide a fast and sensitive approach to quantify IDs, an automated online sample preparation method has been developed. The method uses a Thermo Scientific Transcend TLX-1 system powered by TurboFlowTM technology coupled with a TSQ Quantiva Triple Quadrupole Mass Spectrometer. Specifically, THC-COOH has been extracted from 75 µL of pre-filtered water (using 7 and 0.4 µm paper filters) by an online sample extraction method and quantified using an isotopic dilution approach between 30 and 2000 ng L-1.