Effects Of Olive Mill Wastewater Application Research Articles

Impact of olive mill wastewater (OMW) on the soil hydraulic and solute transport properties

The Mediterranean area concentrates the world’s largest production area of olive oil. The olive oil industry represents, in this basin, one of the leading sectors of the agri-food economy. Olive mill water (OMW) is the principal waste effluent produced by the olive oil industry. Due to its high pollution load, this aqueous by-product cannot be directly disposed of in domestic wastewater treatment plants (especially those with a biological treatment unit). Untreated OMW is currently used for agronomic purposes in several countries, mainly because it is rich in valuable plant nutrients. However, OMW is characterized by toxic phenols, high organic matter, high salinity, suspended solids and several other components that may have possible negative effects on chemical and physical soil properties, as well as soil biological activities. In the present research, we focused on the effects of OMW application on transport and hydraulic soil properties. Three distinct soils from a pedological point of view were selected and a series of laboratory steady-state miscible flow tests were conducted under saturated conditions, on both OMW-treated and -untreated soil columns. Tests were conducted on disturbed and undisturbed soil columns. The approach proposed by Kachanoski, based on soil impedance (Z) measurements via the time domain reflectometry (TDR) technique, was used to monitor the leaching experiments. The breakthrough curves (BTCs) exhibited different shapes that allowed the repercussions of OMW applications on soil transport behaviour to be distinguished. Several additional tests conducted on OMW-treated and -untreated soil cores to determine water retention curves (SWRCs) and saturated hydraulic conductivity Ks allowed us to infer the probable mechanisms involved in soil hydrological behaviour changes under OMW treatments. The results show that when OMW leaches into the soil immediately after its disposal there is little effect on the evaluated hydraulic and hydrodispersive properties. By contrast, we demonstrated that a short incubation period (i.e. a short contact time between OMW and soil) of 10 days is enough to exert a great influence on all the values determined (e.g. soil pore velocity v and Ks reduced by up to one order of magnitude). These effects were especially evident in undisturbed soil samples.Graphic

Spreading raw olive mill wastewater is compatible with the growth and the beneficial functions of the earthworm Octodrilus complanatus

Recycling Olive Mill Wastewater (OMW) by its application on agricultural land is considered to be a sustainable practice for soil enrichment and waste management, and recent legislation permits large scale OMW recycling in Mediterranean countries. Therefore, studies on the effects of OMW application on earthworms under experimental conditions that closely resemble those occurring in the field are urgently required to facilitate the safe and ecologically friendly use of OMW at large scale. In this study, the effects of three-phase OMW liquid on the survival and growth of the earthworm Octodrilus complanatus (Dugès, 1828), commonly present in olive groves, were assessed. The liquid was applied at a rate i) equal to the maximum authorized by Greek legislation for olive groves fertilization (80 m3 ha−1) and ii) half of this amount (40 m3 ha−1). The effects were tested in an indoor experiment conducted in plastic containers. The results showed no adverse effect on the survival of the earthworms over a period of 56 days post-treatment, at both application doses. The growth of earthworms, as estimated by their body weight change at 28 or 56 days post-treatment, was not negatively affected; instead, there was a relative increase seen at the higher dose (80 m3 ha−1), although the difference between the treatments was not significant. Qualitative observations indicated feeding of earthworms on the OMW liquids. Organic matter decomposition was not affected and there was no significant alteration in the soil properties, except the electrical conductivity that was increased at the higher level of OMW application. Therefore, the application of OMW liquids at the doses recommended by the legislation does not affect the survival and growth of the earthworms and is compatible with their activities to promote organic matter decomposition.

Effect of Olive-Mill Wastewater Application, Organo-Mineral Fertilization, and Transplanting Date on the Control of Phelipanche ramosa in Open-Field Processing Tomato Crops

Phelipanche ramosa (L) Pomel is a root holoparasitic weed for many crops, particularly for the processing tomato in Italy. In order to integrate the use of chemical methods to control P. ramosa (L.), there has been an increased effort to research alternative methods using natural compounds. In this regard, two experimental trials were set up in an open field in Foggia (southern Italy) during the 2016 spring–summer seasons. The first trial compared two tomato seedling transplanting dates to evaluate the effects on emerged shoots of P. ramosa. The second trial compared six organic compounds added to the soil to control P. ramosa: olive-mill wastewater and five commercial products (Allyl Isothiocyanate®, Alfaplus®, Radicon®, Rhizosum Max®, and Kendal Nem®). An untreated control was also included. The numbers of P. ramosa emerged shoots (branched plants) were significantly lower for the late tomato seedling transplanting date than for the earlier one. All of the organic products tested that were applied to the soil, particularly olive-mill wastewater, Alfaplus®, Rhizosum Max®, and Kendal Nem®, showed a significant reduction of the P. ramosa infestation of the tomato crop with respect to the untreated control, with a positive effect on the productive parameters.

Effects of Olive Mill Wastewater on Soil Microarthropods and Soil Chemistry in Two Different Cultivation Scenarios in Israel and Palestinian Territories

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.