KINETIC-STUDY OF ANAEROBIC-DIGESTION OF OLIVE MILL WASTE-WATER PREVIOUSLY FERMENTED WITH ASPERGILLUS-TERREUS

A kinetic study has been made of the anaerobic digestion of olive mill wastewater previously fermented with Aspergillus terreus. The anaerob ic process was carried out in a digester containing Sepiolite as suppo rt for the mediating bacteria. The anaerobic digestion process was fou nd to follow first-order kinetics and the experimental methane volume (G) - time (t) data to conform to an equation of the form G = G(m) [1 -exp (- K(A)t)], from which the apparent kinetic constant, K(A), was c alculated. The kinetic constant was found to be scarcely influenced by the substrate concentration over the studied COD (chemical oxygen dem and) range (viz. 3.9-8.8 g/litre). Its mean value was 1.45 days-1. Thi s value was substantially higher than that obtained in the anaerobic d igestion of untreated olive mill wastewater, and the process seemingly involved no inhibition phenomena as the biotoxicity and the total phe nolic compound content (analysed by high performance liquid chromatogr aphy HPLC) were reduced by 86.8 and 94.3% respectively as a result of the pretreatment. Finally, the average COD fraction removal was around 70% and the yield coefficient was 349 ml CH4STP/g COD, viz. 30% highe r than that provided by untreated wastewater.