Degradation of Cocaine and Benzoylecgonine in Sewage Sludge Batch Tests

Abstract

The degradation studies of cocaine and its principal metabolites, benzoylecgonine, as emerging pollutants were carried out using various sludge types collected from the RAF Molesworth Sewage Treatment Work (STW) to determine their distribution and persistence in aquatic environment. The methodology, initially characterized the various sludge types before the laboratory batch tests were carried out at different temperatures and times. The results, after 3 hours equilibration of batch samples, showed the removal rates for cocaine and benzoylecgonine to be 91.0% and 90.6%, respectively. The partition coefficients (Kd) for the two substances ranged from 2.7 – 31.9 Kg L-1. Degradation of compounds was found to be both biotic and abiotic and the two processes produced many short chain compounds and several metabolites that include cocaethylene and ecgonine methylester. Also at 4 ± 0.5o C, the degradation of substances occurred slowly, at 5 and 10% but was relatively greater at 19 ± 0.5o C. Compounds degradation was also influenced by both extracellular and intracellular enzyme activities. The batch study is an innovative method in calculating degradation rates of compounds from sewage treatment works. The capabilities of generating removal rates of drugs have also been clearly demonstrated in this work and can be applied to any organic compounds in real life (STWs) situations