Long-term exposure to low arsenic concentrations in drinking water causes different diseases including cancer. Hundreds of millions of people worldwide are exposed to arsenic in drinking water. Within Europe, Hungary, Serbia and Croatia are likely most affected. Elevated arsenic concentration has been found in several wells used by the Water Supply Company in Makó, Hungary. Groundwater in southern Hungary typically contains also ammonia, methane, some iron and manganese. Situation is very similar in several other surrounding countries. There are intensive efforts to find affordable approach for treatment of such complex arsenic contaminated groundwater. UNESCO-IHE has been developing an innovative arsenic removal technology (IHE ADART), based on adsorption on iron oxide coated sand (IOCS) and an in-situ regeneration of exhausted adsorbent. The paper presents results from field-testing of the IHE-ADART technology in Southern Hungary. Two pilot plants have been operated at several arsenic-contaminated wells with arsenic concentrations from 20 to 260 μg/l. Very consistent arsenic removal below 10 μg/l was achieved at all testing wells and throughout the 18 months of continuous testing. In addition methane, ammonia, iron and manganese were removed highly effectively. Life cycle cost analysis showed that overall treatment costs would be below 0.10 Euro/m3.