Relevance of a combined process coupling electro-Fenton and biological treatment for the remediation of sulfamethazine solutions – Application to an industrial pharmaceutical effluent

A combined process coupling an electro-Fenton pretreatment and a biological degradation was implemented in order to mineralize synthetic and industrial pharmaceutical effluents, containing a veterinary antibiotic, sulfamethazine (SMT). The electro-Fenton pretreatment of an SMT synthetic solution was first examined and the obtained results showed total SMT degradation after 30 min of electrolysis at pH 3, 18 °C, 500 mA and an initial SMT concentration of 0.2 mM, while the level of mineralization remained low (2.1 and 18.1% for electrolysis times of 30 and 60 min), ensuring significant residual organic content for a subsequent biological treatment. In a second part, biological treatments were performed to complete the mineralization of the electrolyzed solutions of SMT, showing a significant level of mineralization after about 18 days of culture, 61.4% for a 30-min pretreatment. The same electrolysis conditions were then applied to the pretreatment of an industrial pharmaceutical effluent, showing a total SMT removal in the effluent after 100 min of electrolysis, while the mineralization yield remained also low (7.5%), showing the formation of organic intermediate products. Fortunately, the mineralization yield during the subsequent biological treatment increased to almost 80%, namely an overall yield of 81.4%. Consequently, the integrated electro-Fenton biological treatment process proved to be an efficient technology to reprocess industrial pharmaceutical effluents.