A novel system coupling an electro-Fenton process and an advanced biological process to remove a pharmaceutical compound, metronidazole

Abstract

The objective of this study was to improve the mineralization of metronidazole, a recalcitrant antibiotic by the development of a new combined process coupling electro-Fenton and a biological process. For biotreatment, various strategies were considered bioaugmentation, bioacclimatation and biostimulation alone or combined. So, the novelty of this strategy is to combine advanced oxidation process with advanced biological process. The conventional biotreatment with activated sludge after 120 h of culture, led to 58.1% mineralization, whereas the pure isolated strains, from activated sludge culture in the presence of metronidazole by-products, identified as Pseudomonas putida (strain A) and Achromobacter sp. (strain B), led to 37.2% and 40.1% respectively. After original acclimation of the isolated strains to electrolysis by-products, the mineralization levels reached 75.6% and 72.9% for strains A and B respectively after 120 h of culture. The results showed that the mineralization of metronidazole by-products was the most important in the case of the combination of autochthonous bioaugmentation and biostimulation, with 96.1% after 120 h of treatment. By coupling the two processes, the global treatment reached therefore a mineralization yield of 97% with a reduction in processing time of 16 days compared to previous conventional biological treatment.