Subsurface arsenic removal is a technology with the potential to remove arsenic at low-cost without any waste stream. The injection of aerated water through single or multiple wells creates a subsurface filter consisting of goethite and ferrihydrite. The efficiency of arsenic adsorption on these iron oxides depends on pH and presence of interfering anions, such as phosphate. Though preliminary results are very promising still a lot has to be done for the system to be effectively operated at small-scale. In the ideal case a small-scale application can be constructed with a single hand pump, however, for safe implementation further information is needed on (i) the risk of arsenic remobilisation, (ii) the required groundwater properties, such as pH and Fe/As ratio and (iii) the optimal well configurations for sufficient oxygen supply.