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Appl. Environ. Microbiol., Sep 1996, 3292-3297, Vol 62, No. 9
A Konopka, T Zakharova, L Oliver, D Camp and RF Turco
The microbial biodegradation of simulated graywater, containing 21.5 mg of
linear alkylbenzene sulfonate liter-1, was investigated with a
continuous-flow bioreactor with 100% biomass recycle. Low concentrations of
organic matter in the ultrafiltration eluate were achieved by hydraulic
residence times as short as 1.6 h and for periods of up to 74 days at a
hydraulic residence time of 6 h. Upon a shift from the chemostat to the
biomass recycle mode, the increase in biomass with time approximated a
linear rather than an exponential function. Biomass densities as high as
6.8 g of cell protein liter-1 were reached; this was 50-fold higher than
the steady-state biomass level in chemostats fed the same medium. We
assessed physiological changes in the microbial community after a switch
from the chemostat to the biomass recycle mode. Over 150 h, there was a
two- to fourfold decrease in the respiratory potential of the microbes.
After this decrease, respiratory potentials were relatively constant up to
74 days of operation. A decline in reactivity was also indicated by
increasing lag periods before growth in response to organic nutrient inputs
and by a decrease in the proportion of cells able to reduce tetrazolium
dye. However, the bioreactor system was still capable of rapidly
metabolizing inputs of organic matter, because of the very high biomass
concentrations. It appears that < 10% of the organic carbon inputs
accumulate as biomass.
Copyright © 1996, American Society for Microbiology
Biodegradation of organic wastes containing surfactants in a biomass recycle reactor
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA. akonopka@bilbo.bio.purdue.edu
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