[Filamentous bacteria in activated sludge (bulking sludge). I. Occurrence of filamentous bacteria in a sewage treatment plant working with the activated sludge process (plug flow system)].

The occurrence of filamentous bacteria in activated sludge (bulking sludge) was investigated in the sewage treatment plant Berlin-Ruhleben. The studies were carried out in five periods from 26.10.1981 to 29.7.1982 (= 112 sampling days). It was noticed that filamentous bacteria appeared in the aeration tanks in different quantities and several kinds of species. With the identification key from Eikelboom Microthrix parvicella, Type 021 N and Type 0041 were frequently identified in all aeration tanks, whereas Type 0961 and Nocardia spec. were observed only in several aeration tanks. Haliscomenobacter hydrossis, Thiothrix spec., Type 0914, Type 1701, Type 1851 and Type 1852 appeared only sporadically. Besides the familiar filamentous bacteria another species was identified under the microscope which, however, could not be classified so far. The filaments are straight or slightly bent with a visible septation and long cylindrical cells. The species is Gram- and Neisser-negative and shows no deposition of sulfur granules.