Assessment of the desalination potentials of some algal/cyanobacterial strains isolated from Buffalo River in the Eastern Cape Province, South Africa.

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dc.contributor.advisorOkoh, A.I.
dc.contributor.authorMnikana-Cibi, Yolanda Blessings
dc.date.accessioned2026-08-18T10:30:46Z
dc.date.available2026-08-18T10:30:46Z
dc.date.issued2024
dc.descriptionMsc dissertation
dc.description.abstractWater scarcity is a global disaster, especially in arid and semi-arid countries including South Africa. When compared to the global average, South Africa's average rainfall is very low. Furthermore, freshwater scarcity is expected to worsen over the next few decades as the human population and demands grow, and the development of sustainable, energy-efficient desalination technologies could make about 97% of the water in the oceans become a useable substitute. Biodesalination using cyanobacteria is an emerging approach that could be used to achieve this feat. As a source of nutrition for growth, algae and cyanobacteria absorb ions that have a negative impact on water quality, and cyanobacteria can grow in high salt concentrations while producing a low-salt environment. Both biosorption and bioaccumulation contribute to salt removal, with biosorption having the highest salt removal efficacy. This study explores the potential of desalination potential of freshwater and marine algal/cyanobacterial strains isolated from the Buffalo River in the Eastern Cape Province, South Africa. It supports sustainable development goals related to clean water, climate action, and environmental conservation. The standard culture-based method was used for the isolation of presumptive algal and cyanobacterial strains from water collected from the Buffalo River. The presumptive cyanobacterial isolates with desalination potential were then sent to Inqaba Biotech for identification. Identification was done based on Next-generation sequencing (NGS). In total, 25 species were identified, comprising 12 cyanobacteria (Anabaena sp., MAG: Pseudanabaena, Pseudanabaena sp., Nostoc minutum, Synechococcus lividus, Hydrococcus rivularis, Spirulina subsalsa, Chroococcus sp.,Cyanobacterium aponinum, MAG: Dolichospermum, Dolichospermum sp., Chamaesiphon minutus,), diatom (Nitzschia inconspicua), and 12 green algae (Coelastrella sp., Chlamydomonas sp., Chlorella vulgaris, Monoraphidium sp., Parachlorella kessleri, Chlorella sorokiniana, Tetradesmus obliquus, Monoraphidium sp., Picochlorum costavermella, Stichococcus bacillaris, Haematococcus lacustris) isolated from the buffalo River. Out of the 20 screened isolates, 5 non-axenic (25%) strains exhibited biodesalination potential of more than 40% salinity reduction. These 5 non-axenic cultures named: 3 Wimpy, 12 Grinika, 14 Grinika, 15 Ndevana, 20 Buffalo Pass were further investigated for optimisation of culture conditions for high algal biomass to improve the efficiency of the algae/cyanobacteria biodesalination. The optimum parameters investigated included carbon source, nitrogen source, pH, light source, and effects of different salinity concentration. Salinity reduction was achieved by up to 92% salinity reduction at salt concentrations of 20 ppt seawater. Both sucrose and nitrates were found to be the best carbon and nitrogen sources under high salinity conditions yielding 55.5% and 50.0 % respectively at the regulated optimum parameters of shaker speed (180 rpm), temperature (30 ± 3 °C), 40 Watts cool white, fluorescent bulbs, and pH 7.5. To prevent the release of salt and cyanotoxins produced by cyanobacteria reverting into the desalinated water, membrane filtration was used to safely separate and recover algal and cyanobacteria strains from desalinated water. Removal of cells from the desalinated water resulted in a significant salinity reduction. To address public health and safety concerns, an in vitro toxicology study was conducted using the CyQUANT LDH Cytotoxicity Assay Kit to assess the potential risks associated with desalinated water, which turned out to be negative. The use of cyanobacteria and photosynthetic organisms in the desalination of seawater has been proven in this study. Algal strains have been shown to produce significant biomass in seawater while at the same time reducing the salt content. Using optimal conditions for algal/cyanobacterial growth, such as light, carbon, and nitrogen sources enables cyanobacteria to grow at high densities and enables future biological processes for sustainable water treatment applications. However, energy sources were a major challenge in this study. Alternative methods should be investigated for the supply of artificial energy sources. Equally, more stringent monitoring of physiological changes caused by ionic stress should be investigated. Understanding how salinity affects cell growth and viability would enable scaling up cyanobacterial growth to meet the demands of water treatment scenarios.
dc.identifier.citationMnikina-Cibi, Y.B. (2024) Assessment of the desalination potentials of some algal/cyanobacterial strains isolated from Buffalo River in the Eastern Cape Province, South Africa. MSc (Microbiology) dissertation. Alice, South Africa: University of Fort Hare.
dc.identifier.urihttp://hdl.handle.net/20.500.11837/4830
dc.language.isoen
dc.publisherUniversity of Fort Hare
dc.subjectSaline water conversion -- South Africa -- Eastern Cape
dc.subjectCyanobacteria -- South Africa -- Eastern Cape
dc.subjectFresh water -- South Africa -- Eastern Cape
dc.subjectSeawater -- South Africa -- Eastern Cape
dc.titleAssessment of the desalination potentials of some algal/cyanobacterial strains isolated from Buffalo River in the Eastern Cape Province, South Africa.
dc.typeThesis
person.identifier.orcid0000-0003-1884-1978

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