Naturally occuring radioactivity in residues of drinking water treatment

In the course of a research project about 500 residues of drinking water treatment from approx. 400 water supply companies in Bavaria were investigated on naturally occurring radioactivity. For each residue the effective dose for workers was evaluated for each residue. The results show that increased activities, particularly of Radium-226, can be found in the material. The dose due to the exposure to the residues, which mostly result from the backwashing of filters, is below the reference value of 1 mSv/a, which can be used according to paragraph 97 of the German radiation protection standard. During the project the quantity of residues in Bavaria and the ways of their disposal were evaluated. In addition the relation between the amount of natural radioisotopes in the residues and the geological and hydrochemical conditions of the water catchment area was pointed out. (orig.)