[Qualitative and quantitative determination of bacterial populations in an aquatic environment. 8. Variation of the species spectrum during a drinking-water treatment process].

Water treatment processes such as aeration, gravel filtration, ozonation, activated-carbon filtration and chlorination causes variation in the number of bacteria as well as the development or die off of specific species. The number of bacteria was always reduced to a large extent if ozone or chlorine were applied whereas after filtration process often an increasing number of bacteria could be observed in the effluent. Despite of the differing bacterial counts a reduction of the variety of species was found during all treatment process. Whereas the raw water contained a heterogeneous spectrum of copiotrophic and oligotrophic bacteria the treated water contained mainly slow growing oligotrophic bacteria which didn't express any physiological activities.