Evaluation of different treatment processes with respect to mutagenic activity in drinking water.

Treatment processes which are applied in The Netherlands during the preparation of drinking water have been evaluated with regard to introduction and removal of organic mutagens as well as halogenated organics. It appeared that the most efficient processes in reducing mutagenic activity were activated carbon filtration and artificial dune recharge. In general these processes were also the most efficient in removing halogenated organics. Using low doses of chlorine dioxide (less than 1 mg C1O2/l) for safety disinfection of drinking water, no change or substantial less mutagenic activity than by chlorination (1 mg Cl/l) was found. This counts too for the formation of halogenated organics. Transport chlorination of stored river Meuse water was able to introduce or activate mutagenic nitro organics which have not been found previously. Ozone treatment under field conditions showed mostly a tendency to decrease the activity of organic mutagens. It was also shown that dependent on the water quality and treatment conditions a slight increase of mutagenic activity occurred, but this activity would be reduced by increasing the ozone dose. It seems possible to optimize the ozone treatment conditions regarding the level of ozone dose and the contact time to avoid an increase of mutagenic activity. Furthermore it was shown that when a mutagenic raw water source was used a proper combination of treatment processes is able to produce drinking water in which no mutagenic activity could be detected under the test conditions. Finally it is stated that before far-reaching decisions with respect to use mutagenicity data for a selection of water sources or treatment processes will be made, more information on the relation mutagenic activity from drinking water and effects on human health should become available.