Abstract
The active biomass in thermophilec aerated sewage sludge was analyzed during a period of more than two years under the following aspects: The viable cell counts of neutrophilic thermophiles (when determined at the actual sludge temperature) varied up to five orders of magnitude during the observation period; there were always acidophilic and alkalophilic thermophiles present, however, at lower concentrations. The thermal distribution of microorganisms was always extremely broad (eurythermal), ranging from psychrophiles to bacteria capable of growth around 80°C. The percentage of thermophiles able to degrade polymers was usually high, occasionally up to 100%. Stability of thermophilic populations was high, even after drastic changes of cultural parameters, i.e., either temperature, mean hydraulic retention time, or aeration rate. A representative subset of thermophilec isolates was characterized using mainly classical microbiological and biochemical techniques. At least 95 % of the thermophiles were classified as Bacillus stearothermophilus . The populations did not produce antimicrobial compounds in detectable amounts not was an unusual resistance to antibiotics found. All thermcphilec isolates did grow very rapidly on simple media even under oxygen limited conditions.
Published Version
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