Quantifying filamentous microorganisms in activated sludge before, during,and after an incident of foaming by oligonucleotide probe hybridizations and antibody staining

Quantitative oligonucleotide probe hybridizations, immunostaining. and a si mple foaming potential test were used to follow an incident of seasonal fil amentous foaming at the Urbana-Champaign Sanitary District, Northeast Waste water Treatment Plant. A positive correlation was observed between an incre ase in foaming potential and the appearance of foam on the surfaces of aera tion basins and secondary clarifiers. In addition, during the occurrence of foaming, the mass and activity of Gordon ia spp. increased as measured by fluorescence in situ hybridization, antibody staining, and quantitative mem brane hybridization of RNA extracts. An increase in Gordonia spp. rRNA leve ls from 0.25 to 1.4% of total rRNA was observed using quantitative membrane hybridizations, whereas during the same period, the fraction of mixed liqu or volatile suspended solids attributed to Gordonia spp. increased from 4% to more than 32% of the total mixed liquor volatile suspended solids, These results indicate that both the activity and biomass level of Gordonia spp. in activated sludge increased relative to the activity and the biomass lev el of the complete microbial community during a seasonal occurrence of fila mentous foaming. Thus, Gordonia spp. may represent a numerically dominant b ut metabolically limited fraction of the total biomass, and the role of Gor donia spp. in filamentous foaming may be linked more tightly to the physica l presence of filamentous microorganisms than to the metabolic activity of the cells. (C) 2001 Elsevier Science Ltd. All rights reserved.