Comparison of reverse osmosis and electrodialysis in brassware effluents treatment

The manufacture of the handcrafted items is carried out in a succession of deposit baths and rinses. However, this process gives rise to complex and highly loaded effluents, including a mixture of heavy metals (Cu(II), Ag(I) and Ni(II)). Therefore, to meet the Moroccan discharge limits, it is necessary to treat these effluents before discharging them into the natural environment. The objective of this study is the comparison of electrodialysis (ED) and reverse osmosis (RO) in the reduction of heavy metals in brassware wastewater of the city of Fez (Morocco). The first part is devoted to the study of the influence of the operating parameters of RO (transmembrane pressure (TMP) and recovery rate) on the quality of the permeate. The rejection (R) of metal ions (Cu(II), Ag(I) and Ni(II)) increases with TMP, but decreases with the increase in the recovery rate. The maximum values of 96%, 66.39% and 99.6% have been reached for Cu(II), Ag(I) and Ni(II), respectively. The second part of this work focuses on the feasibility of ED in the removal of heavy metals. The influence of the demineralization rate (DR) on the quality of the dilute is studied. Results show that the removal rate of cations (Cu(II), Ag(I) and Ni(II)) increases with the increase of DR and reaches, respectively 98%, 95% and 97% for a DR of 90%. Finally, a comparison between RO and ED based on the water quality delivered and the energy consumed is performed under optimal operating conditions.