Increase of the anaerobic biodegradability of olive mill wastewaters through a pre-treatment with hydrogen peroxide in alkaline conditions

Olive mill wastewaters, due to a low biodegradability, acidic pH, high salinity, lack of nutrientsand elevated amounts of polyphenols, are hard to treat using conventional biologicalprocesses. In recent years, several pre-treatments of these by-products have been developedto increase their anaerobic biodegradability and to exploit them for biogas production.However, these processes are often expensive and hard to carry out. This paper presents aprocess, easy to manage, that involves the use of hydrogen peroxide under alkaline conditionswithout the addition of catalysts. This process is able to efficiently increase the anaerobicbiodegradability of olive mill wastewaters. In fact, with mild treatment conditions, it ispossible to obtain polyphenols abatements of 78%, increases of 48% in the volatile fattyacids content and only a restricted reduction in the organic matter content. By conductingmany digestion tests, it was verified that this process permits high biogas production byolive oil by-products. Indeed, with properly prepared samples, after a negligible acclimationperiod, methane yields of approximately 0.37 LCH4/gCODremoved were detected