Background Wastewater, and more generally organically polluted water, is treated by decomposing the organic matter it contains under aerobic or anaerobic conditions. This type of fermentation almost always takes place in a liquid medium (activated sludge, bacteria beds, lagooning, etc.). This requires extremely large surface areas or volumes (extensive lagooning ~ 10 m2/inhabitant equivalent) or the construction of costly plants with complex systems that accelerate decomposition and produce an undecomposed « mass » or sewage sludge which is finally digested in fields or incinerators. These treatment systems are problematic, both in terms of the space they occupy and of the high investment, running (energy, sludge disposal, etc.) and maintenance costs associated with the complex technology frequently used. This particularly applies to small rural communities such as Combaillaux, which has, like the rest of the Languedoc-Roussillon region, an expanding population (1400 inhabitants in 2003; projected 2200 in 2020). The area is already densely built-up (13 % of area), but there is a strong attachment to the preservation of the local economy and the surrounding countryside. 58% of the land is worked (including vines and olive trees) and 29% of the land is protected (120 hectares is forests). Objectives The aim of the RECYCLAQUA project was to demonstrate an innovative process for waste water treatment i.e. lumbri-filtration, which uses earthworms to treat Organically Polluted Water (OPW). The waste water treatment station to be set up by the project was to serve a community of 2000 inhabitant equivalents. The project would demonstrate the feasibility, economic and social interest of earthworm filtration for the treatment of organically contaminated liquids. Its operation would be demonstrated in a concrete local situation which would enable an upstream (waste water) and downstream (treated water and its re-uses) evaluation. Results At the end of the project, the lumbri-filtration waste water processing system was operational and used by the town of Combaillaux. The system reached all the quality requirements for processed waste water under French law (level D4: BOD: 25 mg/l; COD: 125 mg/l or 75 %; TSM: 35 mg/l or 90 %). Purification yield objectives were consistently reached and TSM and BOD abatement was of excellent quality with mean yields of 94 and 97 % and the concentrations were always below level D4 thresholds. The primary advantage of the system resided in the minimal amounts of sludge produced; this sludge in fact consisted almost entirely of pre-treatment residue (sieving This project has been selected as one of the 22 "Best" LIFE Environment projects in 2006-2007