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Appl. Environ. Microbiol., Sep 1997, 3662-3668, Vol 63, No. 9
K Andreasen and PH Nielsen
Excessive growth of filamentous microorganisms in activated-sludge
treatment plants is a major operational problem which causes poor
settlement of activated sludge. An enhanced understanding of the factors
controlling growth of different filamentous microorganisms is necessary in
order to establish more successful control strategies. In the present
study, the in situ substrate uptake was investigated by means of
microautoradiography. It was demonstrated that the uptake of labeled
organic substrates by the filamentous microorganisms, during short-term
incubation, could be detected by microautoradiography. Viability and
respiratory activity of the filaments were also detected by reduction of
CTC (5-cyano-2,3-ditolyl tetrazolium chloride) and by incorporation of
[(sup3)H]thymidine. Gram, Neisser, and fluorescence staining techniques
were used for the localization and identification of the filaments.
Activated-sludge samples from five wastewater treatment plants with bulking
problems due to filamentous microorganisms were investigated. Microthrix
parvicella, Nostocoida limicola, and Eikelboom's type 0041 and type 021N
were investigated for their ability to take up organic substrates. A panel
of six substrates, i.e., [(sup14)C]acetate, [(sup3)H]glucose,
[(sup14)C]ethanol, [(sup3)H]glycine, [(sup3)H]leucine, and [(sup3)H]oleic
acid, was tested. The uptake response was found to be very specific not
only between the different filamentous types but also among filaments of
the same type from different treatment plants. Interestingly, M. parvicella
consistently took up only oleic acid among the tested substrates. It is
concluded that microautoradiography is a useful method for investigation of
in situ substrate uptake by filamentous microorganisms in activated sludge.
Copyright © 1997, American Society for Microbiology
Application of Microautoradiography to the Study of Substrate Uptake by Filamentous Microorganisms in Activated Sludge
Kruger A/S, DK-2860 Soborg, and Environmental Engineering Laboratory, Aalborg University, DK-9000 Aalborg, Denmark
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