Semiconductor electrochemical treatment of domestic wastewater coupled with the production of molecular hydrogen

Abstract

We have developed a wastewater treatment system that incorporates an electrolysis cell for on-site wastewater treatment coupled with hydrogen prodn. for use in a hydrogen fuel cell. Herein, we report on the efficacy of a lab.-scale wastewater electrolysis cell (WEC) using real human waste for the first time with semiconductor electrode utilizing a mixed particle coating of bismuth oxide doped titanium dioxide (BiO_x/TiO_2). A comprehensive environmental anal. has been coupled together with a robust kinetic model under the chem. reaction limited regime to investigate the role of various redox reactions mediated by chloride present in human waste. The oxidative elimination of the COD (COD) and ammonium ion can be modelled using empirical, pseudo first-order rate consts. and current efficiencies (CE). In combination with an anaerobic pre-treatment step, human waste contg. high-levels of COD, protein, and color is eliminated within 6 h of treatment in the WEC. The reactor effluent has residual inorg. total nitrogen (TN) concn. of ∼40 mM. The CE and specific energy consumption were 8.5% and 200 kWh kg/CODfor COD removal and 11% and 260 for kWh kgTN^(-1) for the TN conversion. The CE and energy efficiencies (EE) for hydrogen prodn. were calcd. to be 90% and 25%, resp.