The presence and persistence of cocaine and benzoylecgonine in the Hawkesbury-Nepean river system

Abstract

Many substances of environmental concern enter waterways through the insufficient treatment and subsequent discharge of wastewater. Cocaine is an illicit stimulant drug which is frequently detected in wastewater both within Australia and internationally. Research has examined the presence of cocaine and associated metabolites in environmental waters that receive wastewater but limited work has been undertaken in Australian environments. This study aimed to determine if cocaine and metabolites are present in the tertiary-treated wastewater that is discharged into the upper and mid-sections of the Hawkesbury-Nepean river, a semi-mature, tide-dominated waterway in Sydney, Australia. The investigation revealed that cocaine and the primary metabolite benzoylecgonine are present at detectable levels in effluent from five studied wastewater treatment facilities which discharge into the Hawkesbury-Nepean river system. Concentrations of cocaine within the discharged effluent had a mean value of 4.30 -¦ 0.76ng/L across all sampling periods. Whilst all metabolites were investigated, only benzoylecgonine was detectable with a mean value of 61.61 -¦ 13.14ng/L across all sampling periods. These concentrations were found to be predictable and consistent as a result of the tertiary wastewater treatment process. An investigation into loading between weekday and 'holiday' periods found evidence of increased cocaine and benzoylecgonine concentration of up to 167% and 148% respectively in discharged effluent for some locations. The detected concentrations presented in this work are in-line with comparable studies of highly-urbanised river systems. Along with the direct effluent discharged into the Hawkesbury- Nepean river, both cocaine and benzoylecgonine were detected at lower ng/L levels in domestic non-potable recycled water used in the Hawkesbury-Nepean catchment. To the best of the authors knowledge, this is the first time cocaine and benzoylecgonine have been detected in recycled water in Australia. This research demonstrates that tertiary-treated wastewater under normal operations still emit cocaine in the effluent discharged to river systems. The detected concentrations presented in this work have been shown to result in ecological impacts in previous studies and here we show that degradation is not a rapid process and would allow for significant time for organism uptake.

Date of Award	2020
Original language	English