Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Master → Afrique du Sud → 2014 → Quality assessment of domestic harvested rainwater in the peri-urban region of Kleinmond, Western Cape and the optimisation of point-of-use treatment systems

Stellenbosch University (2014)

Quality assessment of domestic harvested rainwater in the peri-urban region of Kleinmond, Western Cape and the optimisation of point-of-use treatment systems

Dobrowsky, Penelope Heather

Titre : Quality assessment of domestic harvested rainwater in the peri-urban region of Kleinmond, Western Cape and the optimisation of point-of-use treatment systems

Auteur : Dobrowsky, Penelope Heather

Université de soutenance : Stellenbosch University

Grade : Master of Science (MS) 2014

Résumé partiel
Domestic rainwater harvesting (DRWH) refers to the collection and storage of rainwater for domestic purposes and in an effort to achieve the Millennium Development Goals (MGD), the South African government has started an initiative where DRWH tanks are financed in sustainable housing schemes in an aim to provide an additional water source directly to households. Although many provinces, including parts of the Eastern Cape and KwaZulu Natal, have been using harvested rainwater as a potable water source, there are a limited number of studies indicating the quality of harvested rainwater in South Africa. However, many studies, internationally, have indicated that while the practice of harvesting rainwater is gaining popularity, rainwater quality is not within potable standards (Chapter 1). During the first phase of the study, rainwater samples were collected from the Kleinmond Housing Scheme (Western Cape, South Africa). From a cluster of 411 houses, the DRWH tanks connected to 29 houses were selected for monitoring the microbial and physico-chemical properties of harvested rainwater. Drinking water guidelines stipulated by SANS 241 (2005), DWAF (1996), ADWG (NHMRC and NRMMC, 2011) and WHO (2011) were used throughout the study to monitor the quality of rainwater. Eight sampling sessions were then conducted from March to August 2012, during a high and low rainfall period. Overall, the physico-chemical parameters of the rainwater samples were within the respective drinking water guidelines. However, the microbiological analysis verified results obtained in international studies, and showed that the indicator bacteria numbers present in the DRWH samples exceeded the stipulated guidelines (Chapter 2 and 3). Species specific primers were also used to routinely screen for the virulent genes, aggR, stx, eae and ipaH found in Enteroaggregative E. coli (EAEC), Enterohaemorrhagic E. coli (EHEC), Enteropathogenic E. coli (EPEC) and Enteroinvasive E. coli (EIEC), respectively, in the rainwater samples. The virulent pathogenic E. coli genes were then detected in 3% (EPEC and EHEC) and 16% (EAEC) of the 80 rainwater samples collected routinely during the sampling period from ten DRWH tanks (Chapter 3). Bacterial isolates selected during the high rainfall period (June to August 2012), as well as PCR assays performed on total genomic DNA extraction from the rainwater samples, confirmed the presence of numerous pathogenic bacteria including Legionella spp. Klebsiella spp. and Shigella spp. Yersinia spp. were also isolated and detected for the first time in DRWH tanks (Chapter 4). Based on the results obtained in the first phase and as many studies have indicated the poor quality of rainwater, the second phase of the project was aimed at designing and monitoring point of use treatment systems. Three polyethylene DRWH tanks (2000 L) were installed at the Welgevallen Experimental farm, Stellenbosch University, South Africa. Various treatment systems, such as activated carbon and slow sand filtration, solar pasteurization and a combined activated carbon/PVA nanofibre filtration column, were then intermittently connected to the three DRWH tanks during the high rainfall period (June to October 2013). Results for slow sand filtration and activated carbon filters indicated that the biological layer that had developed on the filtration media had not matured and for this reason chemical and microbial parameters were not reduced to within drinking water guidelines.

Présentation

Version intégrale (5,11 Mb)

Page publiée le 1er février 2016, mise à jour le 27 mai 2018