[Occurrence of Pseudomonas aeruginosa in waste water and its behavior under biological treatment].

103 days long, the concentration of Pseudomonas aeruginosa was determined in 206 samples of raw wastewater and of the activated sludge after the biological step in the wastewater pretreatment plant of Braunschweig. 2594 strains of P. aeruginosa were isolated, 95.8% of them showed production of pyocyanin. The concentration of P. aeruginosa varied between 2.6 X 10(1) and 4.8 X 10(4) cells/ml. Neglecting some exceptions, there were about ten times more P. aeruginosa in the sludge than in the clearly filtered wastewater and about one hundred times more than in the clearly filtered effluent. In general, P. aeruginosa seem not to be reduced by the biological oxidation during the wastewater treatment. On the contrary, we observed a multiplication in 69% of all cases. The multiplication of P. aeruginosa during the biological oxidation is discussed. Finally, the hygienic role of sludge is discussed because P. aeruginosa are concentrated herein.