Adding alum through electrocoagulation with rotating anodes for treating dyes from wastewaters

Dyes from textile wastewater were treated via electrocoagulation (EC) with alum addition. The effects of various operational parameters on the removal efficiency of contaminants in terms of color and chemical oxygen demand (COD) were examined. These parameters included the rotational speed of the anode, current intensity, contact time, initial concentration of dyes, and the amount of added alum (20 mg/L). Moreover, the EC of textile wastewater samples without alum added and with alum added was compared in terms of the pH value, conductivity, and amount of sludge produced. The results indicated that the optimum conditions for treating textile wastewater samples are current intensity: 0.4 A, rotational speed: 20 r.p.m, contact time: 5 min, and amount of alum (concentration: 20 mg/L) added: 5 mL. Under these conditions, the removal efficiency of dye reached 90%, the COD decreased from 240 to 41 mg/L, and the final pH of the wastewater was 7.29. These COD values indicated that the wastewater can be directly discharged into the water bodies, in accordance with Egyptian law. During the EC method, the addition of alum in very limited amounts has improved the conductivity as well as the efficiency of removing the contaminants; however, it reduced the final pH. Moreover, the addition of alum has also reduced the period of treatment to a quarter of the required time, hence saving more electrical energy. In this regard, the regression analysis was employed to develop a prediction model for the dye removal. The determination coefficient of the Excel model was ( R 2 = 0.908) and a determination coefficient was given by the ANN model as follows: ( R 2 = 0.928).