Use of conductive-diamond electrochemical-oxidation for the disinfection of several actual treated wastewaters

This work assesses the disinfection for reuse of treated urban wastewaters using electrochemical-oxidation with conductive-diamond anodes, without adding any external chemical reagent. Three actual effluents of municipal wastewater treatment plants (sample collected from the secondary clarifiers) have been treated using this technology, in every case, a complete removal of Escherichia coli have been achieved. In addition, it has been found that working within the range of current densities proposed in this work (1.3–13.0 A m−2), this technology does not form any hazardous by-products (neither perchlorates nor halo-compounds), even at trace level. Combined effects of chloramines and hypochlorite seem to be the main mechanisms to explain disinfection. The primary disinfectant produced in every electrolyses depends on the current density, and on the concentration of both: chlorides and non-oxidized nitrogen, present in the raw treated wastewater. Power consumption as low as 0.2 kW h m−3 is enough to assure the complete disinfection of a particular treated wastewater. The lower the applied current density, the lower the energy required to get the disinfection of the treated wastewater.

► Electrolysis with conductive-diamond anodes assures the disinfection of urban treated wastewaters.
► It assures the total removal of coliforms without the addition of any reagent.
► Hypochlorite and chloramines have been identified as the main disinfectants produced.
► Formation of hazardous compounds is not obtained by this technology using low current densities.
► Power consumptions as low as 0.2 kW h m−3 is enough to assure the complete disinfection of treated wastewater.