Browsing by Author "Louw, Carli"

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    Diamond based electrodes for water quality applications: disinfection, micropollutant removal and the suppression of biofilm proliferation.
    (Stellenbosch : Stellenbosch University, 2024-03) Louw, Carli; Wolfaardt, Gideon M. ; Botes, Marelize; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: Rivers in most low and middle income countries face a growing burden of pollution in the form of pathogens and persistent micropollutants caused by waste discharge from informal settlements and poorly maintained wastewater treatment plants, operating above capacity. Farming communities are often reliant on the these rivers for irrigation. This study investigated the potential application of diamond based electro-oxidation in decentralized water treatment systems for disinfection and micropollutant abatement. The diamond-electrode based electrochemical in-situ system (DiaDis) forms ozone and hydroxyl radicals via electro-generation. It was hypothesised that the system would possess strong disinfection properties, but that micropollutant abatement would be dependent on the compounds and organic matter present. The disinfection study included the treatment and prevention of biofilms by monitoring the effects on biofilm metabolic activity during DiaDis treatment. A pure culture of Pseudomonas fluorescens sp. was used for the single culture biofilm disinfection study, and for the mixed species biofilm study the culture was sampled from a polluted river. The disinfection capabilities of the DiaDis was found to be comparable or slightly superior to 1:10 dilution sodium hypochlorite in this study for the single culture biofilms, however, the mixed species biofilms were more effectively treated with sodium hypochlorite. Biofilm-forming species have varying resistance to disinfectants and the results suggest the presence of synergistic adaptation. For the single and mixed species biofilms the treatments studied proved more effective when used preventatively than to treat mature biofilms. Removal efficiency of micropollutants by the mixed species biofilms was comparable to published literature, although lower abatement rates were reported for caffeine and acetaminophen, which could be the result of higher organic matter acting as oxidation scavenger in the environmental water. Negative removal rates were obtained for sulfamethoxazole, benzotriazole and efavirenz, likely due to electro- oxidation facilitated reconstitution of breakdown products to the respective parent compounds. The DiaDis was evaluated as a final disinfection step in an aquaponics, as well as a constructed floating wetland system. It performed better in the floating wetland, possibly due to higher levels of organic matter coming from fish-feed in the aquaponics system. Overall the DiaDis showed promising disinfection capabilities, which will benefit from future work to better control pH reduction and to reduce interference of organic matter with micropollutant abatement.