540 Chemie und zugeordnete Wissenschaften
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- Abwasser (1)
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- OMW (1)
- Olivenölproduktion (1)
- bait-lamina test (1)
- biodegradation (1)
- olive oil mill wastewater (1)
- phenolic compounds (1)
- soil water repellency (1)
- water re-use (1)
During olive oil production, large amounts of olive mill wastewater (OMW) are generated within a short period of time. OMW has a high nutrient content and could serve as fertilizer when applied on land. However, its fatty and phenolic constituents have adverse effects on soil properties. It is still unknown how seasonal fluctuations in temperature and precipitation influence the fate and effect of OMW components on soil properties in a long-term perspective. An appropriate application season could mitigate negative consequences of OMW while preserving its beneficial effects. In order to investigate this, 14 L OMW m-2 were applied to different plots of an olive plantation in winter, spring, and summer respectively. Hydrological soil properties (water drop penetration time, hydraulic conductivity, dynamic contact angle), physicochemical parameters (pH, EC, soluble ions, phenolic compounds, organic matter), and biological degradation (bait-lamina test) were measured to assess the soil state after OMW application. After one rainy season following OMW application, the soil quality of summer treatments significantly decreased compared to the control. This was particularly apparent in a three-times lower biodegradation performance, ten-fold higher soil water repellency, and a four-fold higher content of phenolic compounds. The soil properties of winter treatments were comparable to the control, which demonstrated the recovery potential of the soil ecosystem. Spring treatments resulted in an intermediate response compared to summer and winter treatments, but without any precipitation following OMW application. Significant accumulation or leaching effects to deeper soil were not observed. Therefore, the direct application of legally restricted OMW amounts to soil is considered acceptable during the moist seasons. Further research is needed to quantify the effect of spring treatments and to gain further insight into the composition and kinetics of organic OMW constituents in the soil.
The (un-)controlled application of olive oil mill wastewater (OMW) has positive and negative effects on soil quality. On the one hand it can be used as fertilizer, on the other hand especially the occurrence of soil water repellency is problematic. Due to this fact the objective of this study was to characterize the effects of OMW application on soil and to investigate the mechanisms that are in combination with changes of soil organic matter quality responsible for soil water repellency depending on the climatic conditions.
At first several locations of uncontrolled OMW disposal were screened for positive and negative im-pacts. Then, laboratory incubation experiments and finally a field experiment in Israel were conducted in order to determine the influence of climatic conditions. Besides standard soil parameters (pH, elec-tric conductivity, total carbon, dissolved organic carbon , specific UV-Absorption) it was focused on the determination of phenolic compounds, the carbon isotope ratio, the water drop penetration time and the contact angle as well as the thermal analysis.
This thesis shows that soil water repellency of OMW-polluted soils depends on the climatic conditions, i.e. the application season. In the laboratory as well as in the field the wettability of the soil was strongly reduced under hot and dry conditions. It was observed, that the stable carbon fraction characterized by a high calorific value is responsible for soil water repellency. In particular, amphiphilic substances, e.g. fatty acids, may interact with soil particles as a consequence of drying. On the contrary, no reduc-tion of the wettability of the soil was determined under moist conditions and degradation of organic matter of the OMW was enhanced. Nevertheless, too strong irrigation or rainfall, e.g. in winter, may leach phenolic ingredients of the OMW into the groundwater.
At the same time the application led to an increase of organic and inorganic nutrients, which should be emphasized as a positive effect. Due to these results, a controlled application of olive oil mill wastewater as alternative, low-cost and sustainable treatment option is recommended. But, instead of the current application season winter, the olive mill wastewater should be stored and not be spread before spring in order to avoid negative impacts on the soil.