KINETIC-STUDY OF ANAEROBIC-DIGESTION OF WINE DISTILLERY WASTE-WATER

A kinetic study was made of the anaerobic purification or biomethanation of wine distillery wastewaters ('vinasses'), using bioreactors containing various suspended clayey supports (sepiolite, bentonite and saponite), on to which the microorganisms effecting the purification were immobilised. Assuming that the overall anaerobic fermentation process conforms to first-order kinetics, experimental data pairs, namely the methane volume yielded (G) and the time (t), fitted the following equation: G = G(m) x (1 - exp (K0 x t) ). The specific rate constant, K0, was determined in each of the situations studied. The support used has a marked influence on the kinetic constant of the process; the saponite support yielding significantly the highest values. On the other hand, the specific rate constant decreased over the chemical oxygen demand (COD) range studied (1.0-8.1 g/litre) when the volume of wastewater added or substrate concentration was increased; this showed an inhibition phenomenon. Also, the mean rate biogas production and the methanogenic activity decreased irrespective of the support used. The yield coefficient, Y(P), was 0.32 litres CH4 STP/g COD.