Background The European leather industry consists of about 3000 tanneries, which release a highly pollutant wastewater. Such a release is the cause of major environmental concerns. But in recent years, however, clean technologies, have been developed and implemented. These have reduced considerably the pollution from tanneries, though tanneries still produce wastewater that must be treated with an end-of-pipe solution. The wastewater usually contains a high concentration of nitrogen, which is difficult to remove due to its high solubility. Nitrogen is a major problem in many countries. It causes the eutrophication of watercourses and the pollution of groundwater, a source for drinking water. Objectives The overall objective of the project was to improve water quality in Europe by reducing the nitrogen discharge from the leather industry. A new wastewater treatment technology was implemented in the Elmo Leather AB tannery in Sweden. The technology included nitrification and denitrification processes in the treatment of tannery wastewater to reduce the discharge of nitrogen. The expected reduction of the nitrogen discharge was 80%. (Current technologies achieve about 30% reduction.) As part of the project, a new wastewater treatment plant to use nitrification and denitrification processes for nitrogen removal from wastewater from the tannery was planned. The project results were to be disseminated to other tanneries in European countries via associations and industrial organisations. Results The project developed and tested in full scale a technology for treating wastewater from tanneries that applies nitrification and denitrification processes. It achieved a reduction in nitrogen of 89%, higher than the expected 80%. The nitrogen load from Tanwater wastewater treatment plant is 15 tonnes/year, a marked decrease on 104 tonnes/year using conventional biological treatment. Monitoring of the environmental impact of the tannery also showed a reduction in BOD of 98%, COD of 91% and chromium of 89%. The wastewater treatment process was monitored for 13 months, and tests showed that the process was stable under different weather conditions. The cost of treating wastewater from the leather industry using the Tanwater concept is around the same as the conventional treatment even though it is more efficient. Treatment cost is approximately 1.5 - 1.6 €/m3. The new wastewater treatment technology gives better results than the current BAT technologies, and as a result, several meetings were held with the IPPC Bureau in Seville (part of JRC/IPTS) to discuss the revision of the BREF document for tanneries. As one of the oldest and largest tanneries in Svenljunga, the company has an interest in maintaining such improved environmental performance. This project has been selected as one of the 22 "Best" LIFE Environment projects in 2006-2007