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Content archived on 2024-05-15

Technology for treatment and recycling of the water used to wash olives


Scientific objectives and approach:

The present project aims to create an affordable and compact system capable of recovering and recycling the majority of the drinkable water used in the washing of the olives. The proposed treatment for recycling the most part of the water will follow three basic steps:
- Preliminary aerobic treatment: the treatment will be conveniently implemented before the ultrafiltration unit (or integrated with the ultrafiltration unit in the same apparatus), in order to reduce the content of the organic compounds.
- Ultrafiltration: this stage purifies the waste stream from all of the suspended solids. A factor of volumetric concentration of 10 is foreseen; removal of 100% of the suspended solids and colloids, of 33% of COD, of 50% of the fatty substances. Turbidity of the filtrated liquid <1 NTU is also expected.
- Reverse Osmosis: for the concentration of saline and organic components that were passed into the permeate in first stage and that are found in solution.
The total treatment will allow for the procurement of:
- Drinkable water, to be used again for the washing of olives in loco (more than 90% of the residual is expected to be recycled)
- A relatively small amount of a polluting solution (i.e. with high concentration of pollutants and with the characteristics of vegetation water), to be sent to disposal mixed with vegetation water.
The UDOR project will be structured in 4 phases:
- Identification of requirements and definition of specifications, determined by the end-users, by analysing the generic EU producers situation and by characterising samples from different production sites.
- Laboratory work on the aerobic treatment, the ultrafiltration and reverse osmosis operations: the three principal steps will be studied in the lab to determine the process to be applied, the equipment to be used and the most favourable operative conditions to reach the foreseen specifications.
- Design and development of the pilot plant: the pilot plant will be designed and developed on the basis of the results of lab tests performed.
- Installation and Field tests: the plant will be installed in an oil mill, in order to be tested in site and to evaluate the results of the technology with regard to a real production streams.

Problems to be solved:

Olives undergo a series of treatments and operations in order to reach the point at which oil is extracted from them. The first of these operations is the washing, which is necessary to eliminate the impurities that collect during the harvest and the temporary storage. The water used in this process must be drinkable for obvious reasons of food hygiene. About 50 litres are required to treat 100 kilos of olives. Hence an enormous amount of drinkable water in Europe is consumed by this process (about 5 billions of litres annually). Such huge amount of water is mostly required in rural areas of Mediterranean countries, which exhibit serious shortage of water. Moreover, a chemical analysis of the water after the washing shows a high level of toxicity, with a strong presence of phenols. Currently, there are not generally applied systems in olive processing firms, allowing for the disposal of the pollutants and the recycling of the water used in the washing of olives. Therefore, olive oil producers mix this water with the vegetation water (which is the most dangerous residual of olive processing) and send it to the disposal treatment. This procedure greatly increases the cost of the residuals disposal, because of the higher amount of effluent to be treated and because of the dilution caused by this mixing. In many cases, in order to avoid this increased cost, producers use the water coming from the washing for irrigation or simply send it to sewage. This has a serious environmental impact, since the water is acidic and has a high content of pollutants; in addition the procedure will be illegal or at least heavily scrutinised under the EU Directive 91/271/EEC that concerns urban waste-water treatment.

Expected Impacts:

The UDOR system, if applied to all EU oil production sites, is projected to save about 4 billions of litres of drinkable water per year. The system would clearly have a significant impact in Europe, especially in Mediterranean countries. The significant advantages for oil producers will be:
- Reduction of costs, by reducing the amount of water to be disposed and reducing the cost of disposal.
- Compliance with new regulations in waste water treatment to be applied in agriculture.

Call for proposal

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EU contribution
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Participants (9)