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Cleaner Controlled And Cost-Efficient Olive Oil Production

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For centuries in the production of olive oil in the Mediterranean area, olive oil mill waste products Alpechin and Alpeorujo were carelessly discharged into rivers and lakes or spilled onto land. Several experimental treatment methods have been investigated in the past, e.g. physico-chemical, chemical or microbiological processes, although industrial applications of these methods have not been realised. Biological treatment solutions were so far not very successful mainly due to the high content of antibacterial polyphenols in the olive mill waste inhibiting the activity of microorganisms. This 2.5 year co-operative development effort was brought to a successful conclusion. The COOP consortium is now offering for the first time an economically viable and efficient solution for the cleaning of liquid wastes from olive mills. Essential preparation for the process development was the detailed physical, chemical and biological characterisation of olive mill effluents. Laboratory scale investigations focussed on the development of an integrated process combining physical and chemical pre-treatment steps and a two-stage biological process. After separation of solids the antibacterial polyphenols are removed by physical adsorption. Then the waste is led to an anaerobic degradation process. After a following flocculation step, the supernatant is degraded aerobically. To reach the required limiting values a second flocculation step is carried out. At lab scale with a miniplant installation, the combined process achieved a removal of total organic carbon (TOC) of more than 97%, which exceed the targeted value of 95% stated in the original proposal. Additionally, huge efforts were carried out for post-treatment to remove colour and remnant organics in the microbiologically treated wastewater, for instance by ozone, UV-radiation, FENTON' s agent and various filtration tests. The total process creates only small amounts of solid waste, final waste products, which can be disposed in an environmentally safe manner. Moreover, from the anaerobic step, a biogas production takes place, which can serve for energy winnings and finally lead to reduced costs of the total treatment process. The cleaned water can be recycled and re-introduced at the olive milling process for instance for the washing of olives. Thus, the requirement of fresh water at the olive mills can be reduced to a minimum. The hardware and process parameters were then scaled-up and two modular ß-site bio-reactor plants were designed, constructed and successfully installed at the premises of the COOP partner mills Olivarera del Condado in Spain and at Agrotikos Archanes in Greece. Throughput of the plants was 10 m³/d and 1 m³/d respectively. For both test bed plants, the process of treatment consisted of 5 main steps: separation of solids, adsorption, anaerobic degradation, aerobic degradation and finally clarification by filtration. Because the incremental treatment benefits of flocculation steps do not justify the additional investment and ownership costs, the flocculation steps were not realised in the test bed plants. Nevertheless, after a start-up period, the test bed plant to treat Alpechin (original TOC 28000 mgC/L) from Olivarera del Condado achieved a degradation efficiency of 99.4% (TOC 160 mgC/L), reaching a COD of about 368 mg/L (aim stated in project proposal: COD less than 500 mg/L). In case of the test bed plant employed to treat liquid phase of Alpeorujo (original TOC 21000 mgC/L) at Agrotikos Archanes, a cautious interpretation of results indicates a degradation efficiency of approximately 93%. With these results, the main aim of the project could be reached and confirmed by the operation of the test bed plants. ARGUS has made an application of the patent of the developed process for cleaning of olive mill wastewater at the European Patent Office within the project's duration. With the a. m. process for the first time the running costs of such a biological treatment process lie in the right order of magnitude compared to other olive mill waste treatment solutions. The total running costs of the test bed at Olivarera del Condado, in respect to the combined treatment process consisting of the 6 above mentioned treatment steps, are calculated at EURO 7.67 per m³ of cleaned Alpechin. The reasonable cost of ownership of the COOP developed bioreactor plants will contribute to build acceptance by olive mill operators to integrate the new treatment techniques into the olive milling process. Market research and the feedback from dissemination activities indicated clearly the demand from the milling industry for better treatment techniques. A strong interest in environmental friendly solutions, and in particular in the COOP results, could be observed on part of olive oil mill operators, government officials, experts and media representatives at the COOP workshops conducted in Spain and Greece. A detailed study of user's demands combined with an analysis of infrastructure issues of bioreactor plant utilisation in the olive oil producing countries Spain and Greece indicates very favourable market potential for the COOP bioreactor plants.