Background The world’s population growth over the last 50 years has resulted in greater agricultural intensification through, primarily, the increased application of fertiliser and manure. Despite strong emphasis in European directives and Community action programmes, nitrate contamination is still having adverse effects on water quality. Nitrates are highly leachable and therefore are rapidly lost to groundwater and surface waters. Some 68% of Europe’s rivers exceed natural background levels (0.3-1mg/l according to the European Environment Agency). In England, 27% of water bodies have nitrate concentrations ≥30mg/l. This has an immeasurable effect on the biodiversity of surface waters due to the loss of pollution sensitive species and eutrophication; it also impacts on human health; the recreational and tourist value of rivers; productivity of fisheries and the cost of treating drinking water (for England and Wales alone, this represents €63m/yr). In many European countries it is estimated that by 2100 many water bodies will have nitrate levels ≥50mg/l if farming practices are not altered. While farming is not the sole source, it is widely accepted throughout the EU to be the most significant. From 1950 to 2000 the annual use of mineral nitrogen in the EU increased from 1 to 10 million tonnes. A further 8 million tonnes of manure is spread annually on agricultural soils. However these figures are dwarfed by the quantities of manure excreted by animals onto farmland. In England alone, 45 million tonnes of excreta was deposited on fields by grazing cattle, sheep and pigs in 2000 which constituted 75% of the nitrate input to diffuse waters. The emphasis until now has been on providing advice/education, promoting/enforcing good practice, and financial measures (incentives/penalties). There is a heavy reliance on the farming community to deliver reductions. However, they can do little to address the legacy of nitrate contamination already in the ground and groundwater, which represents a long-term threat as it infiltrates surface waters over future decades. Objectives The project aimed: To demonstrate an innovative, cost effective and acceptable technological solution that would help protect surface waters from diffuse nitrate contamination arising from agricultural practices and would contribute to achieving levels of water quality that do not give rise to unacceptable impacts to human health and the environment. To deliver a solution that would enhance economic and social stability, through the protection of employment within the farming community and associated stakeholder groups, and that would provide significant business opportunities for environmental technology providers/contractors and consultant stakeholder groups. To provide a tool that would complement cross compliance, EU measures and action programmes and support the development and updating of environmental policies. Results The Nitrabar project aimed to demonstrate an innovative technology to improve the legacy of farming practices since the mid 20th century on nitrate levels in ground water. Although there are a number of initiatives and methods to prevent further pollution, the project is unique in that it tackled the build up of existing nitrate pollution. The Nitrabar system is a permeable reactive barrier technology and consists of a trench with a mixture of natural materials (gravel, sand and organic matter), which have the conditions for denitrifying bacteria to thrive. Gabion technology holds the components in place. As groundwater flows through the system, the nitrate present is converted into harmless nitrogen gas. The technology was installed and trialled at a field beside a river at the Ecos Millennium environmental centre in Northern Ireland and its performance verified over a 12 month period. A variety of parameters were monitored. The demonstration showed that Nitrabar is capable of supporting a near 100% denitrification at groundwater concentrates between 40mg/litre and 100mg/litre and remained 85% effective at groundwater concentrations at or above 500 mg/litre nitrate. Environmental and social benefits of Nitrabar: It provides a unique solution for removing existing diffuse nitrate pollution from groundwater, hence reducing incidence of nutrient enrichment of rivers and lakes, eutrophication and minimising the need for end of pipe high cost drinking water treatment; It uses organic widely available materials that may otherwise be regarded as waste, and that are not harmful; Use of the technology would enable the continuation of good farming practice, quality food production and strong agricultural communities; It does not require an energy input once installed.Within the project timeframe it was not possible to verify long term performance, but so far the technology appears most promising. The project partnership hopes to carry out further trials of the technology post project, and is investigating suitable locations and sources of funding for this. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).