Student Number : 9902262G -
MSc Dissertation -
School of Molecular and Cell Biology -
Faculty of Science / Anaerobic fermentative bacteria degrade waste components in landfills where methane
(CH4) and carbon dioxide (CO2) are the primary biogases emitted and methanotrophic
bacteria in the cover soil oxidise the emitted CH4. Three bi-phasic bench-scale landfill
bioreactors were commissioned to evaluate soil nutrient addition effects on CH4
formation and oxidation and to isolate inherent soil methanotrophs using Nitrate Mineral
Salts (NMS) medium. Set A soil contained no nutrient additions, Set B soil contained 50
μM nitrate and 150 μM phosphate and Set C soil contained dried sewage cake.
Bioreactors were run for a 4 week period and pH, anaerobic gas emissions, volatile fatty
acids (VFA), bacterial counts and scanning electron microscopy (SEM) analyses were
performed. A pilot study revealed that pH dictated the stability of methanogenesis, where
increased VFA levels inhibited methanogenesis. Furthermore, it was revealed that
modifications of the NMS medium were needed to enrich for methanotrophs. An in
depth study showed that the Set C anaerobic reactor produced the most methane with Set
B the least. The hypothesis that methane oxidation in the soil could regulate methane
formation in the waste could not be conclusively observed, as a lack of aeration in the
soil reactors is believed to have prevented the proliferation of methanotrophs here. No
methanotrophs were successfully isolated from soil, but rather major heterotrophic
bacterial interference was observed. SEM revealed the presence of rod and cocci forms of
bacteria in both leachate and soil, consistent with literature reports, which indicated that
the bench-scale landfill bioreactors were capable of promoting bacterial growth.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/2076 |
| Date | 22 February 2007 |
| Creators | Muthraparsad, Namisha |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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