Occurrence of illicit drugs in two wastewater treatment plants in the South of Italy

Highlights

• Two wastewater treatment plants have been monitored in terms of illicit drugs.

• Cocaine and cannabis metabolites have been found in both plants.

• High average removal efficiency were found for MOR (90.16%) in WWTP-1.

• Population consume 1.6 doses per 1000 inh⁻¹ day⁻¹ of cocaine.

• Population consume 23.4 doses per 1000 inh⁻¹ day⁻¹ of cannabis.

Abstract

In this study the occurrence and the behavior of illicit drugs and their metabolites have been investigated for two wastewater treatment plants (WWTPs) (namely, WWTP-1 and WWTP-2) located in Sicily (island of Italy). Samples were analyzed for methamphetamine, cocaine (COC), 3,4-methylenedioxymethamphetamine (MDMA), methadone (METH), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), 3,4-methylenedioxy amphetamine (MDA); 3,4-methylenedioxy ethylamphetamine (MDEA), 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) and Benzoylecgonine (BEG). The BEG, COC, MOR and THC-COOH were found at the highest concentration in both WWTPs. The Wastewater-based epidemiology calculation for BEG, COC, cannabinoids and THC-COOH was performed. On average, for both plants, population consumes 1.6 and 23.4 dose 1000 inh⁻¹ day⁻¹ of cocaine and cannabis, respectively. For WWTP-1 negative removals of illicit drugs were observed. For WWTP-2 the following average removal efficiencies were obtained: BEG (77.85%), COC (92.34%), CODEINE (64.75%), MOR (90.16%) and THC-COOH (68.64%).

Introduction

During the last twenty years, on the interest towards the occurrence of emerging pollutants (EPs) in the environment has considerably increased. EPs have been defined as new chemicals with unknown impact on the environment and human health (Deblonde et al., 2011). A wide range of substances are defined as EPs: personal care products, endocrine disruptors surfactants, pharmaceuticals, gasoline additives and radionuclides (Loos et al., 2013, Cosenza et al., 2015). The illicit drugs (IDs) and their metabolites have been recently recognized as a new group of water EPs, with potent psychoactive properties and unknown effects to the aquatic environment (Pal et al., 2013, Evgenidou et al., 2015). The IDs include cocaine, cannabis, amphetamine-type stimulants, ecstasy, heroin and other opioids (Degenhardt et al., 2004).

Regarding the use of IDs, their global production and consumption have increased notably in recent decades. The UNODC (2016) revealed that 5% of the world population ranging between 15 and 64 years consumed an ID in 2014. Since the IDs are often non-prescribed drugs, it is difficult to quantify their amount discharged into environment. With this regards, several authors have recently established a new methodology (Wastewater-Based Epidemiology -WBE) to back-calculate the population drug use on the basis of the amount of a drug target residue concentration in the wastewater (among others, Maida et al., 2017, Causanilles et al., 2017). Indeed, IDs are excreted via urine and feces and arrive at wastewater treatment plants (WWTPs) where they can be measured at ppb levels (Mohapatra et al., 2016, Furhacker, 2008).

IDs can have serious potential effect on the environment due to their feature of being persistent (such as cocaine and its metabolite benzoylecgonine). The IDs’ metabolites preserve the same active action of the mother compound, thus generating toxicological effects on non-target microorganisms (Causanilles et al., 2017). IDs are discharged into the water bodies and environment through the WWTPs. However, since no legal requirements have been set for the IDs discharge into the water bodies, the interest towards the influence of the WWTP on the IDs transformation and/or removal has progressively increased in view of protecting both the environment and the human health. The recent interest towards the amount of IDs discharged into the environment is mainly due to a twofold reason: i. the increased use of IDs (UNODC, 2014, UNODC, 2016); ii. the potential environmental impact of IDs (Li et al., 2016, Santana-Viera et al., 2016, Mastroianni et al., 2017). Over the few last years, IDs concentrations in raw and treated urban wastewater (WW) have been extensively monitored (Dong et al., 2016). However, the role of the conventional biological processes in WWTPs on the IDs transformation has not yet been completely understood. Although conventional biological processes (activated sludge-type) could offer good removal efficiencies of IDs, the existing studies are often lacking of details on the process configurations and operations which hamper the removal mechanisms involved (physical, biological, etc …) (Yadav et al., 2017).

Some authors have demonstrated that the WWTPs have a very poor effect on IDs removal (Evgenidou et al., 2015). A great number of illicit drugs have been detected in the treated wastewater effluent due to the inability of being removed by conventional WWTP processes (Zuccato et al., 2008, Zuccato et al., 2011, Bartelt-Hunt et al., 2009). Thus, IDs are discharged into the water bodies through the treated effluent (Postigo et al., 2011). Several studies have demonstrated difficulties with determining the key processes affecting the IDs and their metabolites transformation inside the WWTPs (Evgenidou et al., 2015). The processes affecting the IDs concentration include: i. degradation to lower molecular weight compounds; ii. physical removal by solids and sludge waste; iii. transformation into conjugates compounds that can be hydrolyzed inside the WWTP and consequently released as parent compounds (Evgenidou et al., 2015). Therefore, monitoring the IDs concentration in WWTPs can have several advantages (Yadav et al., 2017): i. increase the knowledge on the amount of IDs discharged in the environment; ii. estimate the IDs effect on the water environment; iii. indirectly estimate the community level consumption; iv. identify the key plant operating factors mainly affecting the IDs transformation inside the WWTP (Senta et al., 2014).

However, very few studies have been conducted in South of Italy (Zuccato et al., 2016) and only preliminary studies have been published for Sicily (Cosenza et al., 2016, Maida et al., 2017).

Bearing in mind the aforementioned considerations, the objective of this paper is to provide a comprehensive analysis of the occurrence and behavior of IDs and their metabolites in two Sicilian WWTPs. Specifically, two WWTPs (namely, WWTP-1 and WWTP-2) located at the north-western Sicilian coast were monitored for 5 months (one sampling per week). Samples were analyzed for IDs and their metabolites: methamphetamine (MEAMPH), cocaine (COC), 3,4-methylenedioxymethamphetamine (MDMA), methadone (METH), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), 3,4-methylenedioxy amphetamine (MDA), 3,4-methylenedioxy ethylamphetamine (MDE), 3,4-methylenedioxy ethylamphetamine (MDEA), morphine (MOR), codeine (COD), cocaethylene (COCTH), 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) and Benzoylecgonine (BEG). A community level consumption was also assessed for COC and cannabis.