Abstract
This paper deals with the size fractions of iron and organic matter in four samples of untreated (raw) and ozonized humus-containing groundwater. The fractionation was made to specify the needed pore size of possible membranes for the removal of oxidated iron and organic material. In the tests, iron contained in two of the raw water samples penetrated all filters almost completely. The iron in ozonized water flocculated somewhat differently in different types of water. In three water samples, the set limit for domestic water was reached after filtration with a 0.20 μ m filter, which was done after ozonation had flocculated the iron. One water sample required a 100 kD filtration.