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Evaluation of the risks associated with the use of rooftop rainwater harvesting and groundwater for domestic use and livestock watering
Expanded Title:South Africa has a mixture of developed and developing regions with at least 9.7 million (20%) of the people that do not have access to adequate quality water supplies (Kahinda et al., 2007). Rooftop rainwater harvesting (RRWH) has recently been considered to be one of the most promising alternatives for supplying freshwater in the face of increasing water scarcity and escalating demand (Sazakli et al., 2007). Although rainwater harvesting is being practised in a number of areas, the technology is not fully utilised in rural communities. Rainwater harvesting can provide water directly to households including those in rural and peri-urban areas where conventional technologies cannot supply adequate volumes for domestic purposes. In order to improve water access, the South African government has committed itself to provide RRWH tanks to poor households, who in most instances use it without prior treatment as it is assumed to be safe (Kahinda et al., 2007b). Although the general public perception is that RRWH is safe to drink, the presence of potential pathogens such as Escherichia coli, Aeromonas spp., Campylobacter spp., Salmonella spp., Legionella pneumophila, Giardia spp., Cryptosporidium spp., Vibrio spp. and enteric viruses have been reported in these water sources (Ahmed et al.,2011a). When rain falls to the earth it is initially free of microorganisms but as it drops or gravitate towards earth it acquires airborne particles such as dust, pollutants, organic matter and microorganisms suspended in the air (Kauirik et al., 2012). Microbes can be present in the air as bio-aerosols or may be attached to dust particles or other organic debris suspended in the air which allows them to become incorporated into the rainwater (Kaushik et al., 2012; 2014). At the catchment surface of rooftops, dust, debris and faecal droppings that have been deposited by animals (i.e. birds) or wind are washed down into the gutters and then into water tanks particularly after the first rains (Ahmed et al., 2012c). Microorganisms associated with dust particles or faecal droppings will multiply in rainwater collecting or storage vessels due to the available nutrients (Kaushik et al., 2012). Inside the storage tanks, microorganisms may die with time or survive and proliferate in biofilms (Rasid, 2009). Of the microorganisms that can be present in RRHW, bacteria are abundant and diverse and may include both pathogenic and non-pathogenic species whose presence and prevalence are indicative of the factors contributing to the prevailing microbial quality (Ahmed et al., 2012c). While efforts are ongoing to minimise the contamination in RRWH, successful mitigation is limited unless the variety and concentrations of contaminating pathogens are known. It is therefore important to develop tools that can effectively detect and characterise pathogens of concern in RRWH (Shanks et al., 2010). Moreover, biofilm formation and microbial proliferation in the holding tanks are important factors to consider to better understand microbial populations in stored RRWH (Ahmed et al., 2010a).
Date Published:01/12/2016
Document Type:Research Report
Document Subjects:Agricultural Water - Small holder irrigation
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:2175/2/16
ISBN No:978-1-4312-0875-3
Authors:Korsten L; Casey NH; Chidamba L
Project No:K5/2175
Originator:WRC
Organizations:Department of Agriculture, Forestry and Fisheries
Document Size:4 593 KB
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