Removal of pharmaceutical compounds from real urban wastewater by a continuous bio-electrochemical process at pilot scale

Abstract

A coupled bio-electrochemical treatment was designed by combining a microalgae-based system with an electro-oxidation (EO) process for removing pharmaceutical compounds in real urban wastewater. First, a preliminary study was carried out at bench scale to identify the best configuration for the coupled treatment, which involved determining whether EO should be used as a pre or post-treatment of the microalgae-based system. The results showed that using EO as a post-treatment provided the best removal results for most of pharmaceuticals, with an average of 58.8% compared to 47.7% obtained with EO as a pre-treatment. Based on these results, a bio-electrochemical treatment was designed using a high rate algal pond (HRAP) followed by an EO process at pilot scale. EO process was evaluated using a Boron Doped Diamond electrode anode and cathode (BDD/BDD cell) with a current density of between 20 and 30 mA cm−2 and an electrolysis time of one hour. This coupled treatment showed removal efficiencies above 80% for hypolipidemic, analgesics and anti-inflammatory drugs. However, antiepileptic drugs showed the lowest removal rate between 36.8% and 69.1%. It is noteworthy that carbamazepine and 10,11-Dihydro-10,11-dihydroxycarbamazepine (CBZ-Diol) showed almost five times the removal rate in the coupled treatment compared to HRAP alone. Overall, the coupled bio-electrochemical treatment proved to be efficient in removing the studied pharmaceutical compounds. The HRAP pre-treatment reduced the presence of organic and inorganic load by 77.4%, allowing the EO process to remove the more recalcitrant target contaminants.