חזרה לתוצאות חיפוש

Land spreading of olive mill wastewater in Israel: Current knowledge, practical experience, and future research needs

Controlled land spreading of olive mill wastewater (OMW) is now adopted in several Mediterranean countries as a practical alternative for its disposal. This approach has been supported by a large number of studies showing the potential fertilization value of OMW and the absence of negative effects on soil properties. In Israel, the current experience is limited. A few spreading activities have been managed and monitored by the Israel Ministry of Environmental Protection. More detailed information is available from two experiments conducted under controlled conditions in Newe Ya'ar (Jezre'el Valley, northern Israel) and from commercial spreading done in the olive orchard of Revivim (Negev, southern Israel). A short-term increase in soil phytotoxicity (a bioassay with cress, Lepidium sativum L.) was observed in Newe Ya'ar, whereas the soil partly or completely recovered between successive applications. In Revivim, no phytotoxicity was measured across soil profiles. Yet, the collected information shows potential leaching of organic constituents (expressed as dissolved organic carbon, DOC) and phenolic compounds (measured as total phenols, TP), as well as accumulation of presumably the more recalcitrant organic constituents. Surface spreading may cause more leaching as compared to application followed by tillage. Soil microbial activity was generally enhanced by OMW application; in Revivim, the application of OMW caused a temporary increase in the numbers of soil bacteria and fungi, whereas after degradation of the more labile fraction, the number of fungi increased in correlation to TP concentrations. A similar DOC/TP ratio was observed in Revivim across soil profiles, suggesting no selective degradation of OMW in the upper as compared to deeper soil layers. A judicious selection of sites that are safe for OMW spreading is currently hampered by the limited knowledge about potential transport and biodegradation rates under field conditions, on one hand, and the lack of hydrological sensitivity maps of suitable resolution, on the other hand. Until a detailed study is completed that will support safe spreading, it is recommended that future OMW applications be restricted to cases of unavoidable OMW release, and not used as a widely-accepted disposal approach. Co-composting of OMW with various agricultural solid wastes is suggested as a safer recycling alternative.