OPTIMAL CONDITIONS IN THE COAGULATION FOR COLOR REMOVAL FROM DYESTUFF WASTEWATER

摘要

The major challenge regarding dyestuff wastewater treatment is the difficulty in removing dye from the effluent as well as the great variation in wastewater quality during batch production. For years, coagulation has been a common practice for this treatment. The objective of this study is to evaluate the efficiency of different coagulants used for treating dyestuff wastewater. The results showed that the coagulation process of FeSO_4 and polyferric sulfate (PFS) were significantly more efficient than that of Fe_2(SO_4)_3. The optimal pH for the coagulation by FeSO_4 was between 9.5 to 10 and 6 to 7 for PFS. When FeSO_4 and PFS were applied simultaneously, the color removal was improved from 90 to 95 percent. Both FeSO_4 and Ca (OH)_2 were effective in color removal, although their modes of action on the floc blanket settling velocity were completely opposite. The sequence in application affected the performance of the combination treatment by FeSO_4 and Ca(OH)_2. Central Composite Design (CCD) and Response Surface Methodology (RSM) were used to optimize the conditions of the most influential variables in the conventional FeSO_4-Ca(OH)_2 treatment procedure.