Comparative study for the transformation of emerging contaminants and endocrine disrupting compounds : electrochemical oxidation and biological metabolism

Thesis (MSc)--Stellenbosch University, 2020.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.AFRIKAANSE OPSOMMING: Slegs 1% van alle water bronne is vars water wat toeganklik is vir gebruik en word al meer deur mens gemaakte materiale soos soliede en chemiese afval, besoedel. Vorige studies het gewys dat verskeie organiese mikro-besoedelstowwe nie deur konventionele water behandeling verwyder word nie en dat dit voortduur in natuurlike water bronne. Die primêre doel van hierdie studie was nie om mikro-besoedelstowwe te meet en te monitor nie, maar eerder om twee degradasie prosesse, elektrochemiese oksidasie en mikrobiese degradasie, asook die gevolgelike transformasie produkte te ondersoek. Die hipotese was die mikrobiese afbraak minder toksiese transformasie produkte gaan produseer as die sterk proses van chemise oksidasie. Twee mikro-besoedelstowwe, sulfamethoxazole en carbamazepine, was geselekteer op grond van hul wyd verspreide opsporing en voortdurendheid in die omgewing. Die CabECO tegnologie gebruik die proses van elektrochemiese oksidasie om osoon in die waterige fase met die doel vir water behandeling. Die CabECO tegnologie produseer >2 mg/L osoon en toon sommige effektiwiteit om die mikrobiese lading van omgewings water monsters meningsvol te verlaag, alhoewel veelvuldige ordegroottes van mikrobes steeds teenwoordig is, veral in monsters met hoë CSB. Dit was ook effektief in die afbraak van SMX en CBZ, deur dit te verwyder tot onder deteksie limiete binne 1 min se behandeling. Selfs met effektiewe afbraak binne 1 min, het die endokrien versteurende effek tot 4 ure se blootstelling geverg om die estrogeniese/anti-estrogeniese aktiwiteit te verwyder. Alhoewel effektief vir SMX en CBZ, is die CabECO tegnologie minder effektief teen ‘n wye reeks van mikro-besoedelstowwe en omgewings monster, waar nie-teiken stowwe die ozoon aas. Mikrobiese afbraak van SMX en CBZ was meer effektief deur nutriënt beperkte biofilms as deur planktoniese ewewigte. Selfs al was bio-afbraak minder effektief as osoon behandeling, was die transformasie produkte minder toksies. Nutriënt beperkte biofilms is skaars in natuurlike sisteme, aangesien meeste natuurlike en afval water hoog in nutriënte is. Daarom sal die toepassing daarvan vir mikro-besoedelaar verwydering toegepas word as ‘n na-sekondêre behandelings stap of ‘n ‘polishing’ stap in water behandelings sisteme. Die moontlikheid van gekombineerder behandelings prosesse moet verder ondersoek word om ‘n sisteem te ontwikke wat beide mikro-besoedelstowwe en die eko-toksilogiese voetspoor effektief verwyder.Master

Addressing Environmental- and Public Health through Urban Water Profiling of Emerging Contaminants in a South African Urban Setting

The study evaluated the mass balance of various contaminants of emerging concern (CEC) from a South African wastewater treatment works (WWTW) and surface waters located upstream and downstream from the point of discharge. A total of 45 CECs, that are grouped into 16 drug classes, were quantified during multiple sampling events that spanned over a period of two years in the study area. Daily loads (DL; in g/day) of the target analytes in the WWTW showed persistence of various CECs, along with population-normalised daily loads (PNDL; in mg/day/1000inh) of pharmaceuticals and drugs of abuse (DOA) that were estimated for the first time in the study area, using the wastewater-based epidemiology (WBE) approach. Multiple chemical markers were recorded in river water located upstream of the WWTW discharge, suggesting other urban pollution sources that contribute towards the CEC loading in the surface water environment. Environmental risk characterisation for the WWTW effluent and surface waters was done to calculate multiple risk quotients (RQs) for each CEC spanning over various sentinel trophic levels. High risk profiles (RQ>1.0) with a frequency of exceedance (FoE) larger than 75% were recorded for several CECs in both WWTW effluent and surface water locations that warrants the need for more refined surveillance of pollution hotspots in the urban catchment. These findings highlight the need for developing an urban water profiling (UWP) approach similar to conventional WBE approaches, at least for low- and middle-income countries (LMICs) where some (peri)urban communities are not connected to municipal sewage infrastructure and thus lead to direct discharge of human waste products into the natural environment

Sewage surveillance of SARS-CoV-2 at student campus residences in the Western Cape, South Africa

The current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostic capacity is limited in defined communities, posing a challenge in tracking and tracing new infections. Monitoring student residences, which are considered infection hotspots, with targeted wastewater surveillance is crucial. This study evaluated the efficacy of SARS-CoV-2 targeted wastewater surveillance for outbreak mitigation at Stellenbosch University's student residences in South Africa. Using torpedo-style passive sampling devices, wastewater samples were collected biweekly from manholes at twelve Stellenbosch University Tygerberg (SUT) campus and Stellenbosch University-Main (SUM) campus student residences. The surveillance led to an early warning detection of SARS-CoV-2 presence on campus, followed by an informed management strategy leading to restriction of student activities on campus and a delay in the onset of the third wave that was experienced throughout the country. Moreover, the study highlighted the extent of possible infections at defined locations even when a low number of confirmed coronavirus disease 2019 (COVID-19) cases were reported. The study also tracked the surge of the Delta and Omicron variants in the student residences using the Thermo Fisher TaqMan® RT-qPCR genotyping assay.</p

Spatial and temporal trends of SARS-CoV-2 RNA from wastewater treatment plants over 6 weeks in Cape Town, South Africa

CITATION: Street, R. et al. 2021. Spatial and temporal trends of SARS-CoV-2 RNA from wastewater treatment plants over 6 weeks in Cape Town, South Africa. International Journal of Environmental Research and Public Health, 18(22):12085, doi:10.3390/ijerph182212085.The original publication is available at www.mdpi.comRecent scientific trends have revealed that the collection and analysis of data on the occurrence and fate of SARS-CoV-2 in wastewater may serve as an early warning system for COVID-19. In South Africa, the first COVID-19 epicenter emerged in the Western Cape Province. The City of Cape Town, located in the Western Cape Province, has approximately 4 million inhabitants. This study reports on the monitoring of SARS-CoV-2 RNA in the wastewater of the City of Cape Town’s wastewater treatment plants (WWTPs) during the peak of the epidemic. During this period, the highest overall median viral RNA signal was observed in week 1 (9200 RNA copies/mL) and declined to 127 copies/mL in week 6. The overall decrease in the amount of detected viral SARS-CoV-2 RNA over the 6-week study period was associated with a declining number of newly identified COVID-19 cases in the city. The SARS-CoV-2 early warning system has now been established to detect future waves of COVID-19.https://www.mdpi.com/1660-4601/18/22/12085Publisher's versio

Uptake and presentation of exogenous antigen and presentation of endogenously produced antigen by skin dendritic cells represent equivalent pathways for the priming of cellular immune responses following biolistic DNA immunization

Gene gun-mediated biolistic DNA vaccination with β-galactosidase (βGal)-encoding plasmid vectors efficiently modulated antigen-induced immune responses in an animal model of type I allergy, including the inhibition of immunoglobulin E (IgE) production. Here we show that CD4+ as well as CD8+ T cells from mice biolistically transfected with a plasmid encoding βGal under the control of the fascin promoter (pFascin-βGal) are capable of inhibiting βGal-specific IgE production after adoptive transfer into naïve recipients. Moreover, suppression of IgE production was dependent on interferon (IFN)-γ. To analyse the modalities of activation of CD4+ and CD8+ T cells regarding the localization of antigen synthesis following gene gun-mediated DNA immunization, we used the fascin promoter and the keratin 5 promoter (pK5-βGal) to direct βGal production mainly to dendritic cells (DCs) and to keratinocytes, respectively. Gene gun-mediated DNA immunization with each vector induced considerable activation of βGal-specific CD8+ cytotoxic T cells. Cytokine production by re-stimulated CD4+ T cells in draining lymph nodes and immunoglobulin isotype profiles in sera of immunized mice indicated that immunization with pFascin-βGal induced a T helper type 1 (Th1)-biased immune response, whereas immunization with pK5-βGal generated a mixed Th1/Th2 immune response. Nevertheless, DNA vaccination with pFascin-βGal and pK5-βGal, respectively, efficiently inhibited specific IgE production in the mouse model of type I allergy. In conclusion, our data show that uptake of exogenous antigen produced by keratinocytes and its presentation by untransfected DCs as well as the presentation of antigen synthesized endogenously in DCs represent equivalent pathways for efficient priming of cellular immune responses