KINETICS OF ANAEROBIC-DIGESTION OF SOFT DRINK WASTE-WATER IN IMMOBILIZED CELL BIOREACTORS

A kinetic study of the anaerobic digestion of soft drink wastewater wa s undertaken, using bioreactors containing various suspended supports (bentonite, zeolite, sepiolite, saponite and polyurethane foam), on to which the microorganisms effecting the purification were immobilized. Assuming the overall anaerobic digestion process conforms to first-or der kinetics, the specific rate constants, K0, derived from the reacto rs with saponite and sepiolite (magnesium silicates) were approximatel y twice those from bentonite and zeolite (aluminium silicates) and alm ost five times higher than in the control reactor (without support); t he polyurethane support showed an intermediate behaviour. The methanog enic activity increased linearly with COD load, with saponite and sepi olite supports showing the highest values. The average yield coefficie nt of methane was 325 cm3 CH4 STP g-1 COD and the percentage eliminati on of COD was 77.8%; these values were not significantly altered by th e type of support used.