Treatment and re-use of wastewater is nowadays a major need all over the world due to the low availability of water resources, as well as to the negative impact on environment of industry. This problem is particularly pressing on the Mediterranean area. Olive oil industry, which is traditional in all the Mediterranean countries, is responsible for high-contaminated wastewater containing organic compounds. These recalcitrant compounds are difficult to detoxify and those effluents need a treatment before being discharged in receiving waters. Conventional physical/chemical methods are time and energy consuming which made them very expensive. This project purposes to apply novel biotechnological processes to treat effluent waters from olive oil industry and, where possible combine with urban sewage, and re-using the resulting waters in horticulture. A new system of Linear Matrix Multicellular Photoreactors (LMMP) using microalgae cultures for the treatment of the final effluent will be designed, constructed and tested in situ. This innovative process intend to achieve an adaptation of the technology to the specific environmental conditions of the regions involved, which will be very low energy consuming and consequently with high economical benefits