Browsing by Author "Pott, Robert"

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    Integrating Microbial Fuel Cells (MFCs) into the treatment of sulphate-rich wastewater
    (2016) Couperthwaite, Jennifer; Harrison, STL; Pott, Robert
    The use of laboratory scale Microbial Fuel Cells (MFCs) for the combined generation of electricity and the treatment of wastewater has been well documented in literature. In addition to this the integration of MFCs into wastewater treatment reactors has also been shown to have several benefits. These include the improved treatment of wastewater, reduced solid waste and the potential to offset the energy costs of the process through the generation of electricity (Du et al., 2007). The treatment of sulphate-rich wastewater, and in particular Acid Rock Drainage (ARD), has become of increasing importance in water sparse countries like South Africa where mining is currently and has taken place. A semi-passive method of continuous ARD waste treatment is currently being investigated within the Centre for Bioprocess Engineering Research (CeBER) (van Hille et al., 2015). This research involves the use of a Linear Flow Channel Reactor (LFCR) designed for combined biological sulphide reduction and sulphide oxidation to yield a sulphur product. Sulphate Reducing Bacteria (SRB) mediate the biological sulphide reduction. Chemical and biological sulphide oxidation takes place in a Floating Sulphur Biofilm (FSB) on the surface of the reactor and is mediated by Sulphide Oxidising Bacteria (SOB). Sulphate-rich wastewater can therefore be remediated through total sulphur species removal.
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    A modified pH drift assay for inorganic carbon accumulation and external carbonic anhydrase activity in microalgae
    (Springer, 2014-01) van Hille, Rob; Fagan, Marijke A; Bromfield, Lucinda; Pott, Robert
    The threat of global warming due to CO2 emissions has stimulated research into carbon sequestration and emissions reduction technologies. Alkaline scrubbing allows CO2 to be captured as bicarbonate, which can be photochemically fixed by microalgae. The carbon concentrating mechanism (CCM), of which external carbonic anhydrase is a key component, allows the organisms to utilise this bicarbonate. In order to select a suitable strain for this application, a screening tool is required. The current method for determining carbonic anhydrase activity, the Wilbur and Anderson assay, was found to be unsuitable as a screening tool as the associated error was unacceptably large and tests on whole cells were inconclusive. This paper presents the development of a new, whole cell assay to measure inorganic carbon uptake and external carbonic anhydrase activity, based on classical pH drift experiments. Spirulina platensis was successfully used to develop a correlation between the specific carbon uptake (C) and the specific pH change (dpH). The relationship is described by: C (mmol C (g dry algae)-1 h-1) = 0.064 × (dpH). Inhibitor and salt dissociation tests validated the activity and presence of external carbonic anhydrase, and allowed correlation between the Wilbur and Anderson assay and the new whole cell assay. Screening tests were conducted on Spirulina platensis, Scenedesmus sp., Chlorella vulgaris and Dunaliella salina which were found to have carbon uptake rates of 5.76, 5.86, 3.86 and 2.15 mmol C (g dry algae)-1 h-1 respectively. These results corresponded to the species’ known bicarbonate utilisation abilities and validated the use of the assay as a screening tool.