The long term effect of Olive Mill Wastewater (OMW) on organic matter humification in a semi-arid soil

This study investigates the performance of soil and OMW microfloras in OMW organic matter humification in soil. In order to highlight the role of OMW and soil microfloras in the processes of OMW organic matter humification, either OMW or soil was sterilized with autoclaving. The study was carried out in microcosms of 1l containing 500 g of raw or sterilized soil, to which was added 200 ml of raw or sterilized OMW. After 24 months of incubation, the amount of phenolic compounds in the different microcosms was statistically indifferent compared to the control. However, TG-DTA and FTIR analysis of soil humic acids showed that recalcitrant OMW phenolic compounds remain in soil humus in the microcosm: sterilized OMW + raw soil, even after 24 months. Results show that humic acids detected in presence of OMW microflora are loaded with proteins and carbonated compounds and deprived of phenolic compounds and aliphatics with long chain, while humic acids detected in absence of OMW microflora are loaded with phenolic compounds.