Arsenic removal in water works

After implementation of the new EU drinking water directive in Denmark, many water works can not comply with the 5 ug As/L limit for the water leaving the water works (10 ug As/L at the consumers tap). 16% of the water in the wells exceed the 5 ug As/L limit. However, a significant removal of arsenic takes place in the water works and therefore arsenic is only a problem in some of the water works among the 16%. The purpose of this project is to improve the basic knowledge of the processes that determine the arsenic removal in water works treating groundwater.
The arsenic removal is studied in the field and in laboratory systems on the basis of water samples and sand cores from sand filters. Data is analysed by PHREEQC and AQUASIM. Various modifications of existing water treatment plants are studied and the results are interpreted on the basis of the process understanding.