Electrochemically assisted photocatalysis for the simultaneous degradation of organic micro-contaminants and inactivation of microorganisms in water

This study presents the assessment of the performance of a photoelectrochemical reactor for the simultaneous degradation of organic microcontaminants (OMCs) and inactivation of bacteria in real surface water. Target OMCs were terbutryn, clorfenvinphos and diclofenac (500 μg L-1 each), and E. coli K12 (10⁶ CFU mL⁻¹) was used as the model microorganism. The reactor utilised a photoanode consisting of two Ti mesh electrodes anodised to give aligned self-assembled TiO₂ nanotubes on the surface. Two cathode materials were investigated i.e. Pt and carbon felt. Higher E. coli inactivation rates were observed with electrochemically assisted photocatalysis (EAP) with a 2-Log Reduction Value (LRV) for Pt and 2.7-LRV in 2 h for carbon felt cathode, as compared to only a 0.8 LRV for photocatalysis (open circuit). For the simultaneous degradation of OMCs and inactivation of bacteria a 4.5-LRV was achieved in 90 min with applied potential and a carbon felt cathode. Similar degradation kinetics were observed for the OMC for both electrochemically assisted photocatalysis and photocatalysis (open circuit) with ca 70 % of the removal of the total OMCs in 60 min. Hydroxyl radical, H₂O₂ and chlorine generation were also evaluated to elucidate the mechanisms of degradation and disinfection. This work suggests that electrochemically assisted photocatalysis is more efficient than photocatalysis alone for the combined removal of OMCs and disinfection of water.