Center for Biofilm Engineering
Abstract:
"Effects of Carbon Source, Carbon Concentration, and Chlorination on
Growth Related Parameters of Heterotrophic Biofilm Bacteria"
00-027 To investigate the growth of heterotrophic biofilm
bacteria, a model biofilm reactor was developed to simulate a drinking water
distribution system. Controlled addition of three different carbon sources
(amino acids, carbohydrates, and humics) at three different concentrations (500,
1,000, and 2,000 ppb carbon), in the presence and absence of chlorine, was used
in separate experiments. An additional experiment was run with a 1:1:2
mixture of the above carbon sources. Biofilm and effluent total and
culturable cells, in addition to total and dissolved organic carbon, were measured
in order to estimate specific growth rates (SGRs), observed yields, population
densities, and bacterial carbon production rates. Bacterial carbon
production rates (mg C/L day) were extremely high in
the control biofilm communities (range = 295-1,738). Both growth rate and
yield decreased with increasing carbon concentrations. Therefore, biofilm
growth rates were zero-order with respect to carbon concentrations used in these
experiments. There was no correlation between growth rate and carbon
concentration, but there was a significant negative correlation between growth
rate and biofilm cell density (r = -0.637, p = 0.001 control and r
= -0.57, p = 0.021 chlorinated biofilms). Growth efficiency was
highest at the lowest carbon concentration (range = 12 - 4.5%, amino acids and
humics respectively). Doubling times ranged from 2.3 - 15.4 days in the
control biofilms and 1 - 12.3 days in the chlorinated biofilms. Growth
rates were significantly higher in the presence of chlorine for the
carbohydrates, humics, and mixed carbon sources (p = 0.004, <0.0005,
0.013, respectively). The concept of r/K selection theory was used
to explain the results with respect to specific growth rates and yields.
Humic removal by the biofilm bacteria (78% and 56% for the control and
chlorinated biofilms, respectively) was higher than previously reported
literature values for planktonic bacteria. A number of control experiments
indicated that filtration of drinking water was as effective as chlorination in
controlling bacterial biofilm growth.
Ellis, B.D., P. Butterfield, W.L. Jones, G.A. McFeters, and A.K. Camper,
"Effects of Carbon Source, Carbon Concentration, and Chlorination on Growth
Related Parameters of Heterotrophic Biofilm Bacteria," Microb. Ecol.,
38:330-347 (2000).
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