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Content archived on 2024-05-21

Wastewater recycling of olive mills in mediterrenean countries - demonstration and sustainable reuse of residuals


The partners will investigate cheap, cost-effective WWT technologies for the processing of olive oil wastewater (OMW) in the Mediterranean. At an experimental test plant biological aerobic treatment technologies (reed beds and Equalisation) will be compared with classical in-plant processes. Anaerobic treatment will be used to produce biogas (valorisation of waste). The effluent quality will be adapted to different reuse possibilities. (Milestone: Definition of water quality). Considering the experimental results a pilot WWTP for the treatment of OMW in Crete will be erected. During the operation of the plant the effluent quality will be economically and ecologically optimised, the biogas production will be maximised; Different reuse possibilities for the WW are investigated: production of plants (treatment and direct production of plants by Equalisation or water reuse in agriculture) and the production of bricks in a nearby brickyard.
The objective of the WAWAROMED project was the treatment and reuse of olive mill wastewater (OMW), which in the Mediterranean region is normally stored in open basins and causes harmful ecological impact due to overflows during winter. The OMW was treated aerobically and anaerobically in order to reduce the organic pollution. COD removal rates of 89 % were achieved but the conductivity of the effluent was still high. In order to facilitate the treatment a new biological sedimenter, which combines the advantages of aerobically and anaerobically treatment was developed. This unit shows good removal rates for COD and phenolic compounds and was realized at an olive mill in Crete. As a second treatment technology Epuvalisation which uses plants in hydroponics to purify the wastewater was tested. Diluted wastewater flowed through gravity in channels in which plants were placed, and circulated for several days. Plants absorbed all the nutrients from the wastewater in order to feed, while their roots were operating as natural filters, withholding the solids the wastewater contained. In anaerobic treated OMW the reduction of COD with the Epuvalisation system, reached, 98%, after a few days (5-9) of effluent circulation in the channels. That reduction was more likely due to sludge settlement.

EC was also reduced due to K absorption from the plants. Some of the plants used in Epuvalisation system (Canna sp, Cyperus sp) adjusted very well in wastewater and got big in height with extended leaf canopy. Those plants were loosing great amounts of water through evapotranspiration. Test were made and in effluent with 33% of wastewater, more than 220 L/day/channel of wastewater effluent was lost through evapotranspiration, that means more than 70L of wastewater were lost per day. Experiments with lysimeter and field-grown olive tress, 20-year-old, were carried out in Chania, Crete, Hellas, in order to study the effects of winter application of OMW (after one day sedimentation) and summer irrigation with treated effluent (aerobic-anaerobic and epuvalization systems) on soil properties and tree performance. Seasonal application of 416 m3/ha of raw OMW (5 applications) for 3 years had no negative effects on plant physiology, nutritional status, yield and soil properties, while soil K increased, enhancing soil fertility. The analysis of leachate from 2 m soil treated with raw OMW in a lysimeter, clearly showed that pollution load (in terms of phenols and COD) was zero. Treated OMW effluent was generally suitable for summer irrigation of olives; however, the effluent from the aerobic-anaerobic treatment plant has to be diluted before used for irrigation. Toxicity tests had proved that the toxic effect of untreated OMW is given to living species. This shows once again the necessity for a treatment of the yearly huge amounts of OMW in the Mediterranean. Microbiological examinations were executed in order to separate special fungi and bacteria.

By this Aspergillus Niger and Geotrichum candidum were isolated, grown and added to the OMW treatment plants in Crete. The removal rate for especially phenolic compounds was increased in order to decrease the toxicity of the untreated and treated wastewater. The energy supply of the OMW treatment plant was designed in order to substitute parts of the conventional energy by renewable energies. A PV generator supplied electric energy and a solar-thermal system was planned to heat the anaerobic reactor up to 37 C. Calculations showed that this concept is useful for small scale treatment plant but for the large scale treatment plant the heating system was realized by a biomass system. The treatment and irrigation facilities will be in operation even after the end of the project due to a cooperation between the local university and the mill owner. Efforts will be taken in order to disseminate the results. In cooperation with the Moroccan partner, contacts to the local government of the city of Fes were worked out in order to realize a similar treatment plant with the developed technologies in Morocco.


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Ginsterweg 1
52428 Jülich

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Participants (5)