Abstract:
Synthetic dyes and pigments released into the environment mainly in the form of wastewater effluents by textile, leather and printing industries cause severe ecological problems. These compounds have a great variety of colors and chemical structures and are recalcitrant to microbial attack.
Biological degradation of different dyestuffs has been extensively studied by both aerobic and anaerobic cultures. However, the degradation of such compounds by either mixed cultures or isolated enzymes is usually very slow. Chemical treatment systems, on the other hand, are generally more effective with respect to biological processes in decolorizing of textile dyestuffs.
Chemical treatment methods adopted in this work are chemical coagulation and Fenton process and both process were compared for COD and color removal efficiencies. Experiments were conducted to investigate the effects of operating variables, including pH, coagulant dose on the color and COD removal efficiency. In first stage of experimental part chemical coagulation has been carried out with coagulants ferrous sulfate, ferric chloride and poly aluminum chloride for removing color and COD from textile mill wastewater. Among the three coagulants, PAC shows highest removal efficiency with a removal of 80.6% and 77.4% for COD and color, respectively. The optimum pH and optimum dose for PAC are 3 and 4g/1, respectively.
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In second stage of experimental part Fenton process was carried out to investigate the effects of pH, temperature, H202 and ferrous sulfate doses on the color and COD removal efficiencies. Maximum removal of COD and color in Fenton process were found to be 84.4% and 93.5%, respectively and the optimum value of H202/Fe2+ ratio was found to be 3.3 for maximum COD and color removal from the textile mill wastewater.
Compared to chemical coagulation Fenton process shows highest removal efficiency for COD and color from textile mill wastewater. Mainly the color removal efficiency is much higher in Fenton process compared to chemical coagulation with PAC.
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