ABSTRACT
The intention and experimental set-up of the pilot sand filter, the treatment of rawwater from Lake Malaren, is described in detail by Hjort et al. (1998). In this part of the project, the intention was to determine the phylogenetic diversity, density and activity of the microbial cells in different zones of pilot plant sand filters fed with rawwater from Lake Malaren. The phylogenetic diversity was determined by in situ hybridization, using oligonucleotide probes specific for the α-, ß- and γ-subclass of proteobacteria. The phylogenetic staining revealed shifts in the population composition from ß-Proteobacteria dominated lake water populations to communities representing members of all subclasses of Proteobacteria, as well as the Cytophaga-Flavobacterium group.
