Background Groundwater provides EU citizens with an important source of fresh water, but the quality of Europe’s groundwater supplies has been threatened by an increase in the amount of nitrates entering aquifers. Agriculture has been linked to this increase in groundwater contamination, which can result in serious negative impacts, such as increased water stress and risks to human health. The latter can be particularly problematic in parts of rural Europe, where residents still rely on wells for their drinking water. Objectives The LIFE+ InSiTrate project aims to demonstrate the potential of an innovative technology for tackling groundwater pollution from nitrates. The technology will be used to restore groundwater quality and improve the safety of drinking water in wells, especially for small communities that do not have access to other freshwater sources. These objectives will be achieved through the following actions: Demonstrating at pilot scale, the feasibility of in-situ bioremediation technology for treating nitrate-polluted groundwater to a standard suitable for human consumption; Developing an innovative tool for design and prediction, based on mathematical modelling, to describe the performance of the in-situ bioremediation technology in any aquifer, and assist in the design of the optimal remediation strategy at each new site; Studying the feasibility of the in-situ technology from a technical, environmental and economic perspective, and comparing this technology with other existing technologies using the same indicators; Fostering uptake of the technology and involving stakeholders and target groups in the technology’s development; Assessing the potential for transferring the technology to other European specific sites to demonstrate its potential implementation; Preparing a decision matrix to select the best organic matter to be used in the in situ bioremediation, based on technical, economic and environmental criteria. Expected results: The main expected results of the InSiTrate project are: A validated strategy and technology for in-situ treatment of nitrate-polluted groundwater and the production of drinking water for small communities; One pilot plant will be designed, operated and optimised; Removal of at least 1 000 kg of nitrates from groundwater; Obtaining 20 000 m3 of water that meets drinking water standards; Design of a tool, based on mathematical modelling, to support the development of the project pilot plant, and two other plants at different sites to show its potential transferability; Selection criteria established for organic matter, taking account of technical, economic and environmental aspects, and including the evaluation of 15 organic substrates; Quantified comparison of the developed technology with two other existing ex-situ technologies and the water blending option. The comparison will include technical, economic and environmental aspects; An environmental profile of the in-situ treatment for the main environmental impact categories: climate change; potential freshwater eutrophication; marine eutrophication; freshwater ecotoxicity; and water depletion (m3/m3 of produced water); An assessment of the cost in euros per m3 of the water produced through the in situ bioremediation technology.