Bio-electrochemical reactor using low-cost electrode materials for aqueous contaminant removal

Abstract

The electrochemical technology is an efficient contaminant removal method for wastewater treatment and reclamation. For achieving high removal efficiency, the significant materials with excellent properties and costly were used as electrodes. In this work, low-cost materials of graphite and copper wire were utilized as anode and cathode electrodes in the bio-electrochemical reactor. The chemical reactions at electrodes generated CO2 and H2 gases, which were utilized for biological nitrate (NO3-) removal via hydrogenotrophic denitrification. The double mechanisms of hydrogenotrophic denitrification and heterotrophic denitrification in the bio-electrochemical reactor caused the increasing NO3- and total N removal efficiencies rather than the ordinary bioreactor (without electrodes and electrochemical reactions). However, the increasing applied current of maximal 30 mA could not significantly enhance the bio-electrochemical performance on the contaminant removal. This is because the chemical precipitation (i.e., MgCO3 and CaHPO4) at the copper wire hindered the utilization of generated H2 by microorganisms. In addition, the use of graphite electrode advantaged on avoiding the sudden pH change from denitrification mechanism; the generated CO2 from graphite oxidation played an important role in pH neutralization during operating.