Browsing by Author "Strauss, Andre"

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    Comparative analysis of solar pasteurization versus solar disinfection for the treatment of harvested rainwater
    (BioMed Central, 2016-12-09) Strauss, Andre; Dobrowsky, Penelope Heather; Ndlovu, Thando; Reyneke, Brandon; Khan, Wesaal
    Background: Numerous pathogens and opportunistic pathogens have been detected in harvested rainwater. Developing countries, in particular, require time- and cost-effective treatment strategies to improve the quality of this water source. The primary aim of the current study was thus to compare solar pasteurization (SOPAS; 70 to 79 °C; 80 to 89 °C; and ≥90 °C) to solar disinfection (SODIS; 6 and 8 hrs) for their efficiency in reducing the level of microbial contamination in harvested rainwater. The chemical quality (anions and cations) of the SOPAS and SODIS treated and untreated rainwater samples were also monitored. Results: While the anion concentrations in all the samples were within drinking water guidelines, the concentrations of lead (Pb) and nickel (Ni) exceeded the guidelines in all the SOPAS samples. Additionally, the iron (Fe) concentrations in both the SODIS 6 and 8 hr samples were above the drinking water guidelines. A >99% reduction in Escherichia coli and heterotrophic bacteria counts was then obtained in the SOPAS and SODIS samples. Ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR) analysis revealed a 94.70% reduction in viable Legionella copy numbers in the SOPAS samples, while SODIS after 6 and 8 hrs yielded a 50.60% and 75.22% decrease, respectively. Similarly, a 99.61% reduction in viable Pseudomonas copy numbers was observed after SOPAS treatment, while SODIS after 6 and 8 hrs yielded a 47.27% and 58.31% decrease, respectively. Conclusion: While both the SOPAS and SODIS systems reduced the indicator counts to below the detection limit, EMA-qPCR analysis indicated that SOPAS treatment yielded a 2- and 3-log reduction in viable Legionella and Pseudomonas copy numbers, respectively. Additionally, SODIS after 8 hrs yielded a 2-log and 1-log reduction in Legionella and Pseudomonas copy numbers, respectively and could be considered as an alternative, cost-effective treatment method for harvested rainwater.
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    Sustainable point-of-use solar disinfection system for roof-harvested rainwater treatment
    (2018-03) Strauss, Andre; Khan, Wesaal; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: Numerous countries worldwide, particularly in sub-Saharan Africa, are currently experiencing severe water shortages and drought conditions. Domestic rainwater harvesting (DRWH) has thus been earmarked as an alternative water source that could provide water directly to households. However, research has indicated that the microbial quality of rainwater is sub-standard and does not comply with drinking water standards as established by various water associations. It is thus recommended that roof-harvested rainwater should be treated prior to use for potable purposes. While the implementation of a first flush (FF) diverter as part of a DRWH system improves the microbial quality of roof-harvested rainwater, cost-effective primary treatment methods such as solar disinfection (SODIS) still need to be implemented on-site to significantly reduce the microbial load (Chapter one). The primary aim of Chapter two was thus to design and construct a pilot-scale SODIS batch system fitted with a compound parabolic collector (CPC) which was (i) constructed from cost-effective materials; (ii) robust in nature in order to withstand adverse environmental conditions and (iii) required minimum maintenance. Two SODIS-CPC systems were constructed and connected to two separate rainwater harvesting tanks. One rainwater harvesting tank was utilised without pre-treatment, while the second tank was connected to a FF diverter. To determine the efficiency of the SODIS-CPC systems, the chemical (anion and cation concentrations as well as turbidity and water hardness) and the microbial quality [indicator organisms including Escherichia coli (E. coli), hetero-trophic plate counts (HPC), enterococci, total and faecal coliforms] of untreated and SODIS treated rainwater samples were assessed during seven sampling events. In addition, the viable Legionella and Pseudomonas population present in the untreated and SODIS treated rainwater was determined using ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR) assays. Chemical analysis indicated that both the anion and cation concentrations before [Tank 1 and Tank 2 (FF)] and after SODIS treatment [SODIS-CPC-1 and SODIS-CPC-2 (FF)] were within the drinking water standards as stipulated by various national and international water associations. In addition, the turbidity of all untreated and SODIS treated rainwater samples were within the aesthetic drinking water guideline, while the total water hardness of all samples were classified as soft. Microbial analysis further indicated that the microbiological quality of the untreated rainwater [Tank 1 and Tank 2 (FF)] was compromised as E. coli, HPC and total coliforms were detected at concentrations exceeding drinking water guidelines. However, after SODIS treatment, the E. coli and HPC were reduced to within the drinking water guidelines. In contrast, while total coliforms were reduced to within the drinking water guidelines during sampling sessions 1 to 4, counts exceeding the guidelines were obtained in the treated samples collected during sampling sessions 5 to 7 for both SODIS-CPC-1 and SODIS-CPC-2 (FF) systems. Moreover, viable Legionella spp. and Pseudomonas spp. were detected in the Tank 1 and Tank 2 (FF) rainwater samples. The copy numbers of these organisms then decreased significantly (p < 0.05) after SODIS treatment in the SODIS-CPC-1 rainwater samples. However, while both Legionella spp. and Pseudomonas spp. copy numbers decreased after treatment in the SODIS-CPC-2 (FF) system, the decrease was not significant (p = 0.195). As results indicated that opportunistic pathogenic genera (Legionella spp. and Pseudomonas spp.) were still viable after SODIS treatment, the primary aim of Chapter three was to investigate the overall diversity and abundance of the viable bacterial community present in the Tank 1 rainwater and the SODIS-CPC-1 treated rainwater, using Illumina next generation sequencing coupled with EMA. Using this technique, the viable opportunistic pathogenic genera persisting after SODIS treatment in roof-harvested rainwater were also detected and identified. After taxonomic assignments were performed, various α-diversity indices were utilised to investigate the diversity and abundance of the viable bacterial communities present in the untreated versus SODIS treated rainwater. Results indicated that there was a significant reduction (p = 0.0033) in species richness after SODIS treatment, indicating that the number of different species in SODIS-CPC-1 rainwater samples were less than in the Tank 1 rainwater samples. In addition, the Shannon diversity index significantly decreased (p = 0.0107) after SODIS treatment, indicating that the species in the SODIS-CPC-1 rainwater samples were less diverse than in the Tank 1 rainwater samples and that the treated rainwater samples were possibly dominated by a smaller group of viable bacteria. The β-diversity was further determined using the Bray-Curtis distance metric and permutational multivariate analysis of variance (PERMANOVA), whereafter results indicated that there was a significant (p < 0.05) shift in the viable bacterial community after SODIS treatment. Although the Nocardiaceae family and Rhodococcus genus dominated the Tank 1 (16.5 %) and SODIS-CPC-1 rainwater samples (44.0 %), the rest of the viable bacterial community differed. For example, Pseudomonadaceae (8.9 %) was the second most abundant family, followed by Sphingomonadaceae (6.0 %) in the Tank 1 rainwater samples. While in the SODIS-CPC-1 rainwater samples, Micrococcaceae (31.7 %) was the second most abundant family, followed by Oxalobacteraceae (5.0 %). Furthermore, signatures of opportunistic pathogenic genera were detected in both the Tank 1 and SODIS-CPC-1 rainwater samples. In addition, genera such as Pseudomonas, Clostridium sensu stricto, Legionella, Mycobacterium and Yersinia, amongst others, were detected in rainwater samples after SODIS treatment. It was thus hypothesised that the presence of these potential opportunistic pathogenic genera may be ascribed to debris, leaves, soil, dust and bird faecal matter which contaminated the catchment area either by anthropogenic activity or naturally through wind dispersion, etc. Based on the results obtained in the current study, it is highly recommended that the catchment area is regularly cleaned, particularly before the rainy season commences and that a FF diverter is routinely installed as part of a RWH system. In addition, it is recommended that the SODIS treated rainwater should primarily be used for domestic purposes such as laundry, irrigation, car washing, etc.