Microbiological investigations into granular sludge from two anaerobic digesters differing in design and industrial effluent purified.
Loading...
Date
1995
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Due to a combination of selection criteria, sludges from upflow anaerobic digesters
treating industrial waste waters consist primarily of well-settling, dense agglomerates
called granules. Quantification of the component mixed microbial populations of these
granules has been severely restricted by the inability of researchers to disrupt them
without concomitantly destroying numerous cells. In situ quantification using light and
electron microscopy is complicated by the high cell numbers and bacterial diversity; the
small cell size; and the destructive nature of electron microscopy preparative
techniques preventing the viewing of more than a small percentage of the population
at a time. For these reasons, in this investigation, standardization of qualitative electron
microscopic techniques was performed prior to their application to granules. Isolation
and electron and light microscopic techniques were applied to granules from a fullscale
clarigester treating effluent from a maize-processing factory. In addition, a
method using montaged transmission electron micrographs (TEMs) taken along a
granule radius, and image analysis, was developed for bacterial quantification within
granules. This method, together with antibody probe quantification, was applied to
granules from an upflow anaerobic sludge blanket (UASB) digester treating a brewery
effluent. The clarigester granules contained a metabolically and morphologically diverse
population of which many members were not isolated or identified. By contrast, the
UASB digester granules consisted primarily of morphotypes resembling Methanothrix,
Methanobacterium and Desulfobulbus, in order of predominance. However, only about
one-third of the population reacted with antibody probes specific to strains of bacterial
species expected to occur within these granules. According to the antibody probe
library used, the Methanobacterium-like cells observed in TEMs were probably
Methanobrevibacter arboriphilus. From this study it is apparent that different anaerobic
digester designs, operational parameters, and the chemical composition of the waste
water purified, are factors which influence the formation and maintenance of granules
differing with respect to their microbial populations. Until the difficulties associated with
quantification are overcome, the processes governing granule formation and/or
population selection will remain obscure.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1995.
Keywords
Anaerobic bacteria--Industrial applications., Sewage--Purification--Biological treatment., Sewage disposal plants., Theses--Microbiology.