Decoloration of textile effluents containing different dyes by a combined coagulation/flocculation proces

Coagulation/flocculation is one of the most important treatment processes in textile wastewater treatments. In the present research, application of coagulation/flocculation process was employed for the removal of different dyes from synthetic textile wastewaters. Experiments were employed in order to determine the optimum conditions for the color removal, i.e. pH control, effective dosage of coagulant and addition of coagulating aid. Solutions of two dyes (Acid Red 299(AR299) and Direct Blue 71(DB71)) were used as colorant to prepare synthetic wastewater. Alum and poly aluminum chloride (PAC) were applied as coagulants and three polyelectrolytes based on acrylamide were employed (cationic, anionic and non-ionic) as flocculating aid. Dye removal percentage was measured using UV-VIS spectrophotometric method. The results showed that the best dye removal efficiency using two coagulants was achieved in neutral pH and PAC is more effective in dye removal. Direct dye due to the larger structure was easily removed by coagulation. Use of polyelectrolytes reduces the precipitation and filtration time and can optimize coagulant dose for dye removal.