THE CAPACITY OF AGRICULTURAL SOILS TO AUTO-REGULATE BIOREMEDIATION OF OLIVE-MILL WASTEWATERS

摘要

Olive-mill wastewaters (OMW) constitute the aqueous phase produced in olive mills after the extraction of olive oil from crushed olives by the addition of water. OMW have a dark color, show high conductivity and exhibit an acidic pH (around 4.8). They present a major environmental problem because of the enormous quantities produced during the winter months, and to their toxic effects and antimicrobial properties. The latter are mainly attributed to the OMW heavy organic load (resulting in BOD and COD values of around 30 and 100 kg/t respectively), and to the presence of recalcitrant polyaromatic compounds (principally phenolics) and perhaps to long-chain fotty acids and volatile acids. In practice the application of OMW to water receptors is prohibited by their high organic load. Previous efforts to reduce the OMW pollutant effect have employed both physico-chemical and biological means. However, technical complexity, high installation and operating costs, and failure to reduce the organic load down to the limits required by law for water receptors have resulted in limited applicability. On the other hand, since OMW are of purely vegetative origin and contain no xenobiotics, added chemicals, or synthetic pollutants, their recycling into agricultural ecosystems, rather than their exhaustive treatment and disposal into domestic sewage or other water receptors, seems environmentally reasonable and financially feasible.