Kinetic study of anaerobic digestion process of wastewaters from ripe olive processing

Abstract

A kinetic study of the anaerobic digestion process of wastewaters from black olive preparation was carried out. The bioreactors used accommodated various suspended micronized clay supports of different chemical composition (Sepiolite and Bentonite). Assuming that the overall anaerobic digestion process conforms to a first-order kinetics, experimental data pairs, namely the methane volume yielded (G) and the time (t) fitted the equation: G=G_m·[1-exp (-K_o·t)], the rate coefficient, K_o, was determined in each of the situations studied. The support used has a marked influence on the kinetic constant of the process; the Sepiolite support yields significantly the highest values. The average K_o values, obtained in the rank of COD between 0 and 1 g/L were: 1,83 days^-1 (Sepiolite) and 1,23 days^-1 (Bentonite). For values of COD greater than 1g/L, the specific rate constant decreased when the volume of wastewater added or substrate concentration was increased. The yield coefficients of methane, Y_p/s, were 333 and 316 mL CH₄/g COD for the Sepiolite and Bentonite reactor, respectively. Treatment yields of COD were above 95% in all the cases.