The aim of this study was the detection of assimilable organic carbon (AOC) at four water treatment plants of different sizes, source waters and technologies. Besides AOC, detection of heterotrophic microorganisms (heterotrophic plate count at 22 and 36oC, moulds), total bacterial counts and basic chemical parameters were performed.
The average values of AOC in source waters were from 70 to 127 μg/l. The influence of technological processes to concentration of AOC was in agreement to other authors (ozonization increases the level of AOC, sand filtration and GAU filtration decrease it).
In one of the water treatment plants studied, the concentration of AOC was always below20 μg/l. No correlation between AOC concentration and other chemical, physicochemical and microbiological parameter were found.