Electrochemical oxidation and microfiltration of municipal wastewater with simultaneous hydrogen production: Influence of organic and particulate matter

Electrochemical reactions, which can produce molecular hydrogen via water splitting, can degrade organic contaminants in water simultaneously. This study focused on the production of hydrogen gas during the electrochemical treatment of organic matter and colloids present in actual municipal wastewater. The electrochemical system used in this study consisted of a BiO_x-TiO₂/Ti anode and two stainless steel cathodes. Hydrogen generation was enhanced in the presence of wastewater organic matter and/or supplemental NaCl. During the electrochemical reaction, the chemical oxygen demand, proteins, and turbidity were removed well, whereas the dissolved organic carbon, carbohydrates, and organic acids concentrations remained unchanged or rather increased. The increase in dissolved carbon content was ascribed to the conversion of particulate colloids to soluble fractions and thereafter incomplete mineralization. Both the loss of organic fluorophores and the formation of large molecular organics during electrochemical oxidation exhibited the degradation of primarily present organics as well as the solubilization of particulate colloids. The accumulation and formation of oxalate and chlorinated intermediates, such as trichloromethane, also occurred. The wastewater particles larger than 0.1μm in size were responsible for the formation of dissolved organic intermediates, but such colloidal particles seemed beneficial to hydrogen generation. Microfiltration in conjunction with electrochemical treatment showed the potential to produce good quality effluent at a high permeability while simultaneously generating hydrogen energy.