Tetracycline degradation and mineralization by the coupling of an electro-Fenton pretreatment and a biological process

BACKGROUND Studies on the degradation and mineralization of tetracycline by means of the electro-Fenton process are lacking in the available literature. Its relevance as a pre-treatment prior to a biological process for the removal of tetracycline was therefore examined. RESULTS Degradation followed pseudo-first-order kinetics and the optimal operating conditions were: 0.1mmolL-1 catalyst (Fe2+) concentration, 300mA applied current intensity and 25mgL-1 tetracycline, leading to total degradation within only 5min and a mineralization yield of 89 % after 6h electrolysis. Biodegradability tests were realized with 100mgL-1 tetracycline; BOD5/COD ratio increased from 0.02 to 0.56 after 6h electrolysis, showing the relevance of the electro-Fenton pre-treatment. However, to keep a significant residual organic content, 2 to 4h electrolysis time may be more relevant, leading to BOD5/COD ratio and mineralization yields of 0.33-0.44 and 46-72%, respectively. CONCLUSION Activated sludge cultures of pretreated and non-pretreated tetracycline solutions were carried out for 3weeks. The overall TOC removal increased from 28% for the non-pretreated tetracycline to 68 and 86% after 2 and 4h electrolysis, confirming the efficiency of the proposed combined process. (c) 2012 Society of Chemical Industry