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A Laboratory Study of Bacteria‐Facilitated Cadmium Transport in Alluvial Gravel Aquifer Media
Author(s) -
Pang L.,
Close M. E.,
Noonan M. J.,
Flintoft M. J.,
Brink P.
Publication year - 2005
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2005.0237
Subject(s) - cadmium , bacteria , chemistry , adsorption , desorption , environmental chemistry , effluent , spore , microbiology and biotechnology , environmental engineering , biology , environmental science , genetics , organic chemistry
ABSTRACT Colloids, including bacteria, can dramatically accelerate the transport of heavy metals in ground water. Batch and column experiments were conducted to investigate adsorption of cadmium (Cd) onto Bacillus subtilis spores or Escherichia coli vegetative cells and Cd transport in alluvial gravel aquifer media in the presence of these bacteria. Results of the batch experiments showed that adsorption of Cd onto the bacteria was (i) positively related to solution pH, bacterial concentration, and negative surface charge, but inversely related to Cd concentration and (ii) a rate‐limited nonlinear process, but adsorption onto E. coli was much less. For column influent Cd concentrations of about 4 mg/L and bacterial concentrations of ≥10 5 colony‐forming units (cfu)/mL, there was a significant increase in total Cd effluent concentrations. In comparison with controls that did not have bacteria‐facilitated transport, Cd traveled 17 to 20 times faster when it traveled with mobile bacteria. However, Cd traveled mostly 2 to 3 times slower during the desorption phase under the influence of bacteria retained in the column. The difference between total and dissolved Cd concentrations was significant during Cd cotransport with B. subtilis spores, but this concentration difference was very small during Cd cotransport with E. coli , suggesting an adsorption‐dominant mechanism during Cd cotransport with the spores and the possibility of Cd chelation by the dissolved membrane vesicles secreted from E. coli cell walls. Bacteria‐facilitated transport of heavy metals may pose a threat to ground water quality in sites such as landfills and following land disposal of industrial and domestic effluent and sludge.