Masters Degrees (Microbiology)

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Browsing Masters Degrees (Microbiology) by Author "Brocker, Johann Heinrich Ludwig"

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    Comparative study for the transformation of emerging contaminants and endocrine disrupting compounds : electrochemical oxidation and biological metabolism
    (Stellenbosch : Stellenbosch University, 2020-04) Brocker, Johann Heinrich Ludwig; Wolfaardt, Gideon M.; Stone, W.; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: As little as 1% of all water sources is fresh water accessible for use and it is increasingly be polluted by anthropogenic materials such as solid and chemical waste. Previous studies have shown that various organic micropollutants are not effectively removed by conventional water treatment processes and persist in natural water sources. The primary aim of this study was not to detect and monitor micropollutant distribution but rather to investigate two degradation processes, electrochemical oxidation and microbial degradation, as well as the resulting transformation products. It was hypothesized that microbial degradation will produce less toxic transformation products than the harsh process of chemical oxidation. Two micropollutants, sulfamethoxazole and carbamazepine, were chosen based on their widespread detected and persistence in the environment. The CabECO technology harnesses the process of electrochemical oxidation to produce ozone in the aqueous phase for water treatment and produced >2 mg/L of ozone at the suggested operating parameters. Ozonation of environmental water sources showed some success in reducing the microbial load, however, several orders of magnitude of microbes remained after treatment, especially in samples with high COD. It also proved effective in the abatement of SMX and CBZ, reducing the micropollutant concentration to below detection limits within 1 min. However, the endocrine disrupting effect of the compounds required up to 4 hours of exposure time to ozone to eliminate the estrogenic/anti-estrogenic activity. Although effective for SMX and CBZ, the CabECO technology is less effective against a broad suite of micropollutants and environmental samples, where non-target pollutants scavenge the ozone. Microbial degradation of SMX and CBZ was more effective by nutrient limited biofilms than by planktonic counterparts. Even though biodegradation was less effective than ozonation, the transformation products proved to be less toxic. Nutrient limited biofilms are scarce in natural system, as most natural and waste water is high in nutrients, therefore the application thereof for micropollutant removal would be a post-secondary treatment step or ‘polishing step’ for water treatment systems. The possibility of combinations of treatment processes should be further investigated to optimize a system that can effectively reduce micropollutants as well as the eco-toxicological footprint.