Aim of the project WADISUN is the development of a plant for the treatment of waste water from agricultural production. The water will be separated thermally from the waste water contents with the help of solar energy under the condition that the cost for construction and running of the plant are kept as low as possible. The plant should not contain any control device and should be largely maintenance-free.

A potential target group for such a plant are medium-sized farms of the participating Mediterranean countries, e.g. small- up to medium-sized olive oil mills. Since regulations for water protection are lacking or insufficient, it is still current practice to infiltrate the waste water, which arises seasonally within the harvest months September - March, into the ground or to discharge it without treatment into nearby receiving waters. Besides requirements implied by the process, other important demands on the plant to be developed result from the economic situation of the plant operators:

1. Investment and operating costs of the plant have to be kept as low as possible so that they can be financed by the agricultural businesses.
2. Installations requiring other energy sources in addition to solar energy, e.g. control devices for plant operation, have to be excluded, if possible. The plant has to be maintenance-free and easy to operate.

Within the scope of the work different technical alternatives are compared on an itemized basis with analysis of both alternatives of drying and distillation with possible recovery of water with a limited range of uses due to slight contamination with volatile phenolic compounds.

The aim of the project to develop a low-cost on-site treatment method for highly concentrated waste waters with the help of solar energy was not fully reached. In spite of partial success concerning drying and distillation with pilot plants, the effluent quality obtained was not sufficient. Some problems with the elimination of residues still have to be solved.

Although the costs can be estimated only within certain limits at the present state of the work, the investment costs determined and thus the specific treatment costs, related to the input material "olives", appear to be too high.