Melanoidins removal from simulated and real wastewaters by coagulation and electro-flotation

• Effective pre-treatment of molasses effluents by coagulation or electro-flotation.
• Effective post-treatment of molasses effluents by coagulation or electro-flotation.
• Effective re-use of the produced ferric hydroxide sludge from coagulation.

Melanoidins are brown recalcitrant bio-polymers present in the effluents of fermentation processes due to their antioxidant properties. In this study, removal of melanoidin from simulated and real wastewaters (biologically treated and untreated) was investigated by coagulation/flocculation. The studied operating variables, based on the maximum removal of color expressed in ADMI units, were coagulant concentration, pH, mixing time and sludge re-use. The results show that coagulation experiments could achieve color removal 90% and higher, at pH = 5, for all wastewaters but with different ferric ion dose. Real effluents could be discolored by 100 mM [Fe3+], while simulated by 300 mM [Fe3+]. After flocculation, the generated ferric hydroxide sludge was washed, solubilized and re-used effectively in a new run. Melanoidin removal was also studied by electro-flotation. Color removal was 95%, 90% and 45% for real treated, real untreated and simulated wastewaters by applying 0.5 A current intensity. Furthermore, coagulation can reduce significantly the COD content of real effluents.