The effects of pH of water or wastewater on electrocoagulation are reflected by the current efficiency as well as the solubility of metal hydroxides. When there are chloride ions present, the release of chlorine also would be affected. It is generally found that the aluminum current efficiencies are higher at either acidic or alkaline condition than at neutral. The treatment performance depends on the nature of the pollutants with the best pollutant removal found near pH of 7. The power consumption is, however, higher at
neutral pH due to the variation of conductivity. When conductivity is high, pH effect is not significant. The effluent pH after electrocoagulation treatment would increase for acidic influent but decrease for alkaline influent. This is one of the advantages of this process. The increase of pH at acidic condition was attributed to hydrogen evolution at cathodes, reaction [10] by Vik et al. [31]. In fact, besides hydrogen evolution, the formation of Al(OH)3 near the anode would release H+ leading to decrease of pH. In addition, there is also oxygen evolution reaction leading to pH decrease. When there are chlorine ions, there are following chemical reactions taking place