In the municipality of Sund, located in a sensitive rural area in Åland, a demonstration project is now carried out with the overall objective to move the most concentrated fractions of wastewater from the coastal area to a treatment plant situated close to arable land. Blackwater and greywater septic sludge from about twenty households and two tourist camps are treated together with energy rich organic material from a nearby potato-chip factory. The collection concept is based on the use of extremely efficient water-saving toilets, with separate systems for the blackwater and greywater in the households. The collected materials are co-treated in a batchwise aerobic thermophilic treatment process (wet composting process), where the materials reach at least 55°C during a minimum of 10 hours. The dry matter content of the collected material was about 2%. After stabilisation and sanitation (by the temperature rise caused by microbial activity during the treatment process), the compost slurry is utilized as a liquid organic fertilizer on arable land.