Background European soils contain many legacies from a less-sustainable industrial past; soils, sediments and groundwater are sinks for many pollutants. The European Environment Agency (EEA) estimates the that there are between 300 000 and 1.5 million contaminated sites in the EU that can be cleaned up (where the source of contamination is no longer present). In many other sites, the pollution is still present. Some of the major pollutants present in soils are heavy metals, petroleum hydrocarbons and chlorinated aliphatic hydrocarbons (CAHs). Since CAHs are heavier than water they can easily sink to great depths. Furthermore, because they are very soluble in water and degrade slowly, they also form large groundwater plumes that are very difficult to remediate. Consequently, traditional remediation techniques are often inadequate, time-consuming and expensive. Remediation using soil organisms is a promising remediation approach for CAHs if conditions are favourable, or can be engineered to become favourable. Objectives The project's objective is to demonstrate the applicability of an innovative, cost-efficient and energy-efficient remediation technique for groundwater contaminated by CAHs. This will be applied at a site characterised by low natural groundwater flow velocities. The project aims to demonstrate: The applicability of hydrogeobiocells (HGBcells) using biostimulation and bioaugmentation, for the remediation of CAH-contaminated groundwater in areas where groundwater velocity is very low due to low hydraulic gradients; The successful up-scaling of the production of the dechlorinating microbial culture to be used in the HGBcell for bioaugmentation; The cost efficiency and energy efficiency of the remediation technique (HGBcell using biostimulation and HGBcell using bioaugmentation) for the remediation of CAH-contaminated groundwater; and The applicability of the groundwater remediation model. In addition, an anaerobic bioreactor will be developed for the large-scale growth of bacteria (of the same bacterial population of the HGBcells) on large scale. Project results and know-how will be disseminated to stakeholders. Expected results: The implementation of the dechlorinating microbial culture, the HGBcell and the anaerobic bioreactor; Decrease in the volume of the groundwater contamination in areas with lower concentrations (CAH Decrease of contaminant concentrations in areas where CAH are present in concentrations that exceed 50 mg/l; A reduction of c.40% in the remediation cost and c. 30% in the energy cost; Improved water balance and c. 60% lower water emissions.