USE OF DIRECT VIABLE COUNT METHODOLOGY WITH OZONATION IN DRINKING-WATER

Viable cells were detected by direct viable count methodology on ozonated anthracite taken from an active dual media rapid sand filter. Also, at least a thousand fold more cells were determined to be viable by direct viable count methodology than by the heterotrophic plate count in raw water which had been exposed to ozone. This suggests that bacterial cells were not killed as quickly by ozone as previously thought, and that the direct viable count may have a place in assessing the effectiveness of killing bacteria by ozone. Problems were encountered in determining nutrient responsive cells which could result in errors in the direct viable count.