Electrochemical Processes for Wastewater Treatment

Abstract

Many electrochemical processes for watewater treatment have been developed over the years. In the field of sewage purification attention has focused on clarification, disinfection and phosphate removal with the aim of reducing costs compared to traditional processes. The on-site production of necessary chemicals is a step towards reducing operating costs. Electrochemical treatment is very efficient and reduces process detention times thereby allowing smaller plants. Sea water or brine is mixed with the screened sewage in an appropriate ratio, then passed through an electrolysis cell rather similar to that used for hypochlorite production. Depending on the material of the electrodes, their arrangement (vertical or horizontal) and the applied potential difference, the reactions which occur produce the chemicals required for the purification processes. Downstream the electrolysis, the mixture flows into a clarification basin which acts as a contact tank for disinfection. The detention time of this process depends on the type of basin used. I report results of electrochemical treatment performed on a semiindustrial scale, using horizontal electrodes: anode of graphite or silicon-iron and stretch-iron cathodes; followed by a sludge recirculation clarification basin. The removal of suspended solids and the abatement of B.O.D. and phosphates were much better than those reached by traditional physical-chemical treatment. The energy consumption is approximately 0.5 kWh/m of raw sewage.