Raw and Microbiologically Detoxified Olive Mill Waste and their Impact on Plant Growth

Olive-oil production is of vital importance for the economy and social life of the Mediterranean region; however, the side effect of the olive-oil mill activity is the generation of enormous quantities of biotoxic olive-mill waste within a short period of three months. Numerous physicochemical and biological methods have been used in the past for the treatment of both olive mill wastewater (OMWW, deriving from three-phase extraction systems) and two-phase olive mill waste (TPOMW, deriving from two-phase extraction systems), but these generally failed to come up with a viable solution of wide applicability. On the other hand, since olive mill waste are of purely vegetative origin, their recycling (either raw or after treatment, including composting) into agricultural ecosystems seems environmentally reasonable and financially feasible. The detoxification and biotransformation potential of naturally occurring and other microorganisms is a promising alternative to the previous approach, especially in cases where in situ decomposition of such waste can not be readily applied. Raw and detoxified (chemically and microbiologically) olive mill waste application on tree and crop cultivation, showed that there is differentiation of plant responses depending on the plant species, type of the growth substrate and time of exposure. Based on hydroponics, soil and soilless cultures it appears that the higher the organic matter in the growth medium, the lower the waste toxicity. The toxicity is evident in all the plant functions from the germination to organs morphology, physiology, metabolism, ultrastructure, ripening and quality of the final product. _____________________________________________________________________________________________________________