Occurrence and removal of illicit drugs in different wastewater treatment plants with different treatment techniques

Abstract

BackgroundAs a class of contaminants of emerging concern (CECs), illicit drugs should be taken into account in the water management because of their social and public health risks. Wastewater treatment plants (WWTPs) are usually considered as the source and sink of contaminants, and drug residues are observed in their effluents due to the inefficient removal of CECs. In this study, wastewater samples were collected from eight WWTPs in Changzhou City for assessment of the abuse of 12 illicit drugs in the city by wastewater-based epidemiology (WBE) method.ResultsDrug concentrations ranged from < LOD-51.62 ng/L to < LOD-22.44 ng/L in influent and effluent samples, respectively. The highest removal rate of drugs was 79.0% in the WWTP which used sequencing batch reactor activated sludge (SBR) process method, while the lowest was found in the WWTP using anoxic oxic (A/O) process (47.0%), indicating that the drug removal rates were closely related to the treatment techniques. WBE method was applied to estimate the population normalized illicit drugs consumption. It demonstrated that methamphetamine (METH) was the most abused drug in Changzhou City, ranging from 0.16 to 20.65 mg/d/1000 inh, while other target drugs ranged from < LOD-1.52 mg/d/1000 inh. Consumption of cocaine (COC) and ecstasy was very low among the samples.ConclusionOverall, this research suggests that drug removal rates varied in different WWTPs and the SBR process is the best for removing illicit drugs. All target drugs were incompletely removed in wastewater treatment plants. WBE can be readily used to monitor the abuse of drugs in those regions, compared with traditional monitoring models.