Wine vinasses treatments by ozone and an activated sludge system in continuous reactors

Abstract

In this work wine vinasses have been treated separately by means of a chemical ozonation and a biological aerobic degradation in an activated sludge system, and later by means of a combined process which consisted of an aerobic pretreatment followed by an ozonation treatment, in continuous reactors in all cases. In the ozonation experiments, the hydraulic retention time and the ozone partial pressure were varied leading to substrate removals in the range 4.4–16%, with increases in this removal when both operating variables were increased. A kinetic study, which combines mixed flow reactor model for the liquid phase and plug flow reactor model for the gas phase, allows to determine the rate constant for the ozone reaction and the consumption ratio, which are kO3 = 3.6 l/(g COD · h) and b = 22.5 g COD degraded/mol O3 consumed. The aerobic degradation experiments were conducted in the activated sludge system with variations in the retention time and influent organic substrate concentration in the wastewater. A modified Contois model applied to the experimental results leads to the determination of the kinetic parameters of that model: K1 = 5.43 l/g VSS and qmax = 6.29 g COD/(g VSS · h). Finally, the combined process reveals an improvement in the efficiency of the ozonation stage due to the previous aerobic treatment with increases in the substrate removal reached and in the rate constant obtained, the last one being kO3 = 5.6 l/(g COD · h).