First results from a screening of filamentous organisms present in Buenos Aires's activated sludge plants

Activated sludge samples from municipal and industry plants were evaluated with the aim to recognise the mainly filamentous bacteria found. The routine tests recommended were performed: Gram, Neisser, PHB-Nilo blue epifluorescence reaction and S. The morphologic characteristics were determined. Correlation between environmental conditions and abundance of dominant bacteria were made. All plants were completely mixed configurations with anoxic reactor for denitrification ahead of main aerobic reactor. Also all systems were working at low F/M values or high sludge age (> ten days) and in some cases with low oxygen concentration. The dominant species were Type 021N, Thiothrix I, Sphaerotilus natans, Microthrix parvicella, Nocardia sp, Type 1701, Type 1863, Type 0041 and Type 0092.