The removal of illicit drugs and morphine in two waste water treatment plants (WWTPs) under tropical conditions

The consumption of drugs of abuse has been recently investigated in Martinique using the back-calculation approach, also called the "sewage epidemiology" method. Results demonstrated a very high consumption considering the international data. Wastewater treatment plants (WWTPs) are located just behind the Martinique island shoreline, and effluents could impact the vulnerable corals and marine seagrass ecosystem. The present article aims to determine a WWTP's efficiency by comparing the influent and effluent of two WWTPs, with different residence times and biological treatments, located either outdoors or indoors. In parallel, a degradation study is conducted using spiked wastewater exposed to tropical and ambient temperatures. Results demonstrate the consistent efficiency of the two processes, especially for the outdoor WWTP which uses the activated sludge process. The positive effect of the tropical temperature is showed by the increase of cocaine degradation at 31 degrees C. Thus, low illicit drug residue concentrations in effluent would indicate that wastewater treatment is efficient and even enhanced under tropical context. This fact should be confirmed with others molecules. Furthermore, our results highlight the need for subsequent studies of sludge contamination because of their local recycling as compost.