Due to the encountered difficulties in natural organic matter (NOM) removal, the concept of enhanced coagulation (EnC) was introduced to increase NOM removal where CN is more accentuated.
It is described as the process whereby particles are destabilised by dosing a chemical additive (coagulant) where charge neutralisation (CN) and sweep coagulation (SC) are the major mechanisms. In drinking water treatment, coagulation is the most common process to remove particles and impurities.
Consequently, metal cations must be well distributed in the wastewater before the metal hydroxide formation to decrease the negative effect of SE in EC process. These results may be related to the facts that in the sulphate media the 70% of the aluminium is in the form of Al(OH)3(am) and in the chloride media this percentage is around 40% and the adsorption of chloride or sulphate ions onto the surface of the Al(OH)3(am) can reduce the adsorption efficiency. However, for unskimmed milk sample and cutting oil emulsion sulphate anions were found to be quite harmful both for electrical consumption and EC efficiency. Na2SO4 has been found less efficient than NaCl as SE in EC process for the removal of humic substances, oil-in-water emulsions, and fluoride. This review tries to understand the sulphate effect on the EC reactions. However, literature has reported controversial effect of sodium sulphate on EC process. In order to enhance the EC process efficiency in organic wastewater effluents, sodium sulphate (Na2 SO4) has been used as a supporting electrolyte (SE) to increase the electric current diffusion in the EC cell. Essential mechanisms in EC are charge neutralisation by metal (Fe/Al) hydroxocations and aggregation by van der Waals forces since fl occulation of pollutants with metal is caused by their adsorption on metal hydroxide aggregates. One of the important factors for electrocoagulation (EC) process is the conductivity of the solution to be treated.
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