Comparative study of anaerobic digestion of olive mill wastewater (OMW) and OMW previously fermented with Aspergillus terreus

Abstract

A comparative kinetic study was carried out on the anaerobic digestion of olive mill wastewater (OMW) and OMW that was previously fermented with Aspergillus terreus. Two completely-mixed bioreactors were used for the study. The results obtained were evaluated using the Chen-Hashimoto methane production model to obtain values for the maximum specific growth rate (μmax) and kinetic constant (K) of the process for each case studied. The kinetic parameters were found to be influenced by the pretreatment carried out, and were 4.5 and 3.8 times higher for pretreated OMW than that obtained in the anaerobic digestion of untreated OMW. This was significant at 95 % confidence level. This behaviour is believed to be due to the lower levels of phenolic compounds and biotoxicity present in the pretreated OMW, as compared to untreated OMW, resulting in an improved process performance and stability. Finally, the experimental values of methane production were reproduced with deviations equal to or less than 10% in every case.