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Photocatalytic and membrane technology process for olive oil mill waste water treatment

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Better olive mill wastewater treatment

The aim of a recent EU-funded project was to develop an environmentally friendly and affordable procedure for the treatment of olive mill wastewater (OMWW).

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OMWW is formed during one of the final steps of olive oil production. The wastewater is a particularly strong pollutant and is highly toxic to plants due to its high content of organic compounds and antibacterial phenolic substances. Mediterranean countries, in particular, are largely affected since they produce about 95 % of the world's olive oil. Current technologies for wastewater treatment and disposal are not suitable for use in mill factories, infringe on European and national regulations, and are expensive. The 'Photocatalytic and membrane technology process for olive oil mill waste water treatment' (PHOTOMEM) project aimed to overcome these issues by developing a novel treatment technology. A major part of the treatment process is the degradation of organic pollutants through photocatalysis. This step is based on the interaction of light and catalytic nanoparticles. Researchers optimised the production of ferromagnetic nanoparticles, which were coated with titanium dioxide (TiO2). TiO2 is most effective as a catalyst due to its low cost and toxicity, as well as its high photoactivity and stability. Another crucial step in the treatment is the membrane process, which involves ultrafiltration, nanofiltration and reverse osmosis. Researchers optimised this step to enable the separation of pollutants from up to 85 % of the wastewater. OMWW contains a significant amount of polyphenols such as hydroxytyrosol. Recovery of these polyphenols has been made possible through a final adsorption step in the treatment process. These different steps have been implemented into a pilot plant, with the intention of commercialisation in Spain and Italy. The project had several other positive outcomes, including reducing the chemical oxygen demand (COD) content by about 35 % and improving the overall costs associated with OMWW treatment.

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