Abstract
Although olive mill wastewater (OMW) is often applied onto soil and is known to be phytotoxic, its impact on soil fauna is still unknown. The objective of this study was to investigate how OMW spreading in olive orchards affects Oribatida and Collembola communities, physicochemical soil properties and their interdependency. For this, we treated plots in two study sites (Gilat, Bait Reema) with OMW. Among others, the sites differed in irrigation practice, soil type and climate. We observed that soil acidity and water repellency developed to a lower extent in Gilat than in Bait Reema. This may be explained by irrigation-induced dilution and leaching of OMW compounds in Gilat. In Bait Reema, OMW application suppressed emergence of Oribatida and induced a community shift, but the abundance of Collembola increased in OMW and water-treated plots. In Gilat, Oribatida abundance increased after OMW application. The effects of OMW application on soil biota result from an interaction between stimulation of biological activity and suppression of sensitive species by toxic compounds. Environmental and management conditions are relevant for the degree and persistence of the effects. Moreover, this study underlines the need for detailed research on the ecotoxicological effects of OMW at different application rates.
Highlights
IntroductionOlive mill wastewater (OMW) is produced during the three-phase olive oil extraction process [1]
Olive mill wastewater (OMW) is produced during the three-phase olive oil extraction process [1].Typically, OMW is acidic, has a high chemical and biological oxygen demand, high concentrations of cations and anions, nutrients, fats, oil and polyphenolic compounds [2]
We identified 7 days as the optimal extraction time allowing a compromise between sufficient microarthropod extraction and decreasing water content and heat stress during extraction
Summary
Olive mill wastewater (OMW) is produced during the three-phase olive oil extraction process [1]. OMW is acidic (pH 4–5), has a high chemical and biological oxygen demand, high concentrations of cations and anions, nutrients, fats, oil and polyphenolic compounds [2]. As discharge of OMW into wastewater treatment plants is generally forbidden, it is often discharged in an uncontrolled manner into the environment [3]. OMW treatment could reduce negative biological effects as shown in the study of Mekki, et al [4] and in avoidance tests using the collembolan species Folsomia candida [5]. Treatment options are not feasible in countries where olive oil production is decentralized and/or family-owned, as for example in Greece [6], Israel or the Palestinian Authority [1]. The Israeli Ministry of Environmental Protection allows land application at rates up to 40 m3·ha−1·year−1, which is expected “to be on a safe side” [7]
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