Klosterenga is a decentralised greywater treatment system built in connection to a low energy apartment house downtown Oslo. The system is located 15 minutes by foot from the Oslo Central Station. It treats water from approximately 100 persons. The system consists of a septic tank, a biofilter and a horizontal subsurface flow constructed wetland. The system has shown excellent treatment performance since its start in the year 2000.
Experience from Norway shows that separate treatment of blackwater and greywater nearly achieves "zero emission" and almost complete recycling. Organic household waste can be treated in the same process as the blackwater and yield a fertiliser/soil amendment and energy. The water consumption can be reduced by up to 50%. Compact and technically simple greywater treatment systems facilitate decentralised treatment even in urban areas, reducing the need for a secondary piping and pumping system for transport of untreated wastewater.JENSSEN, P.D. (2002): Design and Performance of Ecological Sanitation Systems in Norway. (= (=Proceedings of the Proceedings of the First International Conference on Ecological Sanitation 5-8 November 2001) ). Nanning, China: EcoSanRes URL [Accessed: 21.11.2012]
In Norway systems consisting of an aerobic biofilter followed by a subsurface horizontal flow constructed wetland have been very successful in reducing organic matter, indicator bacteria, nitrogen and phosphorus in greywater. This paper describes design details and performance of biofilter/constructed wetland systems for greywater treatment in cold climates.JENSSEN, P.D. VRALE, L. (2004): Greywater Treatment in Combined Biofilter/Constructed Wetlands in Cold Climate. In: WERNER, C. (2004): Ecosan - Closing the Loop. Lübeck, Germany: 875-881. URL [Accessed: 21.11.2012]
Today it is possible to foresee completely decentralized wastewater treatment systems in urban areas where the blackwater fractions (urine and faecal matter) is reclaimed for fertilizer and potentially energy production. The water from kitchen sinks and showers (greywater) is treated locally in compact low maintenance systems that constitute attractive landscape elements. These systems can coexist with decentralized water supply.JENSSEN, P. (2005): Decentralized Urban Greywater Treatment at Klosterenga Oslo. In: Ecological Engineering-Bridging between Ecology and Civil Engineering: , 84-86. URL [Accessed: 21.02.2012]