Applicability of coagulation/flocculation and electrochemical processes to the purification of biologically treated vinasse effluent

Abstract

We investigated the use of coagulation/flocculation (CF) and electrochemical oxidation (EO) processes to purify vinasse that had already been biologically treated (vinasse BT). The CF process was analyzed as a function of the concentration of the coagulant (FeCl 3) and the pH of the vinasse BT. After the CF process, EO was performed by potentiostatic electrolysis with a Ti/RuPb(40%)O x anode and Ti/PtPd(10%)O x cathode. The EO process was analyzed as a function of pH of vinasse CF treated and electrolysis time. The efficiencies of the CF and OE treatments on the vinasse BT were quantified in terms of the removal of chemical oxygen demand (COD), color and turbidity. The experimental results showed that the CF process with a coagulant concentration of 20 g/L and a pH of 8.4 removes a significant amount of COD (84%), color and turbidity (∼99%). The subsequent EO step satisfactorily complemented the purification of vinasse BT by CF, yielding removal efficiencies of more than 95% for COD and on the order of 100% for color and turbidity. We suggest that the mineralization via electrochemistry took place by indirect oxidation, mediated by active chlorine derived from FeCl 3 added during the CF treatment step.