Uranium (U) and chromium (Cr) in groundwater are a serious public health concern
due to their chemical toxicity. Even so, microorganisms have developed mechanisms which
permit them to thrive under previously perceived uninhabitable conditions. A number of
bacteria have been isolated from areas impacted with the soluble heavy metals, and can be
exploited as bioremediation agents since they are well adapted to these metals. To date, the
use of microbial mechanisms for bioremediation processes is a growing industry since it
provides green and sustainable technologies.
In this study, the upflow bioreactors were used as a low cost, low maintenance effective
bioremediation strategy in comparison to the available methods of remediation. Two metals
known to be toxic in their soluble state were treated. The first was Cr(VI) from an impacted
site in Limpopo and the second was U(VI) from the Wonderfonteinspruit catchment, North
West Province. The system was efficient for the removal of soluble Cr(VI) and U(VI) from
the impacted water through biostimulation of indigenous bacterial communities. This system
can be up scaled and employed for the remediation of impacted sites, and it will be useful
especially at low levels of U(VI). Indigenous bacterial community from impacted sites have
the capability to reduce Cr(VI) and U(VI) effectively over a sustainable period. The shortage
of electron donor and continuous oxygen exposure in the case of U(VI) act as a limiting
factor. However, in this study successful Cr(VI) and U(VI) reduction rates were increased by
the addition of an electron donor to stimulate the indigenous bacterial community.
Furthermore, a third upflow bioreactor showed that it is even possible with gradual
increases of U(VI) concentration that U(VI) bioreduction is possible at very high levels. The
influent water was spiked step wise with uranyl acetate, allowed to reach maximal U(VI)
reduction/removal and then the diversity was assessed. Despite the 10 mg/l U(VI) fed to the
bioreactor, the established microbial community was able to tolerate, adapt and thereby
remove the U(VI) from the spiked water. Even though biofilm could not sturdily adhere to
the matrix from the bioreactor, high levels of U(VI) removal could be achieved and the
planktonic community maintained. No biofilm could be observed from SEM analysis from
the TEM it was observed that the planktonic microbial community have an interaction with
uranium. Since no U(VI) could be detected from the effluent samples, it is thus postulated the
uranium in contact with the microbial cells is in another form, probably U(IV) as previously
shown in this laboratory. This study allows for the understanding of the metal microbe interactions in impacted environments, the use of this biome to remediate the water in an
effective, low cost and maintenance bioreactor.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08212014-122232 |
| Date | 21 August 2014 |
| Creators | Maleke, Maleke Mathews |
| Contributors | Dr E Botes, Dr PJ Williams, Prof E van Heerden |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08212014-122232/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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