Effect of aerobic pretreatment with Aspergillus terreus on the anaerobic digestion of olive‐mill wastewater

Abstract

A kinetic study was carried out on the anaerobic digestion of olive-mill wastewater (OMW) and OMW that was previously fermented with Aspergillus terreus. The bioreactors used were batch fed and contained saponite as support for the mediating bacteria. The anaerobic digestion process followed first-order kinetics, from which the kinetic constant A was calculated using a non-linear regression. This kinetic parameter was influenced by the pretreatment carried out, and was 3.7 times higher for pretreated OMW than for untreated OMW. The anaerobic processing of pretreated OMW seemingly involved no inhibition phenomena as the biotoxicity and the total phenolic compound content (analysed by HPLC) were reduced by 71.2% and 77.9% respectively as a result of the pretreatment. Finally, the yield coefficient of methane production was 0.345 litres of methane (at standard temperature and pressure)/g of chemical oxygen demand, that is, 23% higher than that provided by untreated wastewater.