Biotoxicity evaluation and electrooxidation as a sustainable removal strategy of organic booster biocides released from ship antifouling paints

Organic booster biocides (OBBs) which are highly evident in ship antifouling paints (Diuron, Irgarol® 1051, and DCOIT) demonstrate clear harmful effects on marine organisms. Hence, the environmental impact on OBBs was first investigated through release tests and biotoxicity. Over a 60-day period, OBBs were released clearly and the EC50 values (concentrations causing 50% toxicity) were determined as 6.12, 9.30, and 0.05 mg/L for Diuron, Irgarol® 1051, and DCOIT, respectively. With this consideration, electrochemical oxidation (EO) process was performed to investigate the removal of OBB, considering that EO process showcase rapid treatment efficiency together with minimal space requirement as compared to other technologies (biological treatment, adsorption, photocatalytic degradation). By performing effective analysis on the trade-off between the OBB removal efficiency and energy consumption, the optimal current densities for Diuron, Irgarol® 1051 and DCOIT were determined as 80, 40, and 20 mA/cm2, respectively. Additionally, the EO conditions were optimized under different types of electrolytes, electrode pH, and electrode spacing to achieve the optimal condition for OBBs removal. The scavenger test in this study further revealed that 1O2 played a major role in the degradation of Diuron (83%) and Irgarol® 1051 (89%), while no dominant ROS were observed in the degradation of DCOIT.