Optimizing rainwater harvesting systems in the eThekwini Municipality: a case study of a public school.
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Date
2021
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Abstract
Rainwater harvesting (RWH) provides a unique perspective for water conservation, especially when considering the South African water crisis. Harvested rainwater could potentially be used for activities like toilet flushing, thereby reducing the strain on municipal supply networks. However, the economic and environmental feasibility of such systems needs to be assessed in relation to their water-saving benefits. Therefore, this research aimed to uncover the viability of two types of RWH systems implemented at a school (Duffs Road Primary). The assessment and design of the two systems (pumped and gravity-fed) were performed providing insight into system optimization in the economic and ecological settings. Water harvestings, municipal cost savings, and municipal carbon emission reductions were key aspects of each system's performance. Economic considerations included capital costs and return periods, while the environmental aspects encompassed system carbon footprints (assembly and operation) and carbon emission reduction periods. Life cycle assessments (LCAs) of the system components were also incorporated into the research, acting as an extension of the environmental feasibility analysis. The LCAs were performed using a software-modelling program called SimaPro. It was found that the gravity-fed system outperformed the pumped system in both economic and environmental contexts. Although the pumped system garnered higher harvestings and municipal savings and was also deemed economically feasible with a return period of under 6 years, the presence of pumps made the system ecologically inviable. On the other hand, the gravity-fed system would allow for yearly benefits of 452.48 kL in water savings, R27 850.94 in municipal cost savings, and 185.11 kg CO2 in municipal carbon emission savings. Including the fact that the return period would be less than 5 years and the period to reduce the system carbon footprint at just over 10 years, the system displayed both economic and environmental viability (from a global warming perspective). Besides the gravity-fed system costing less, it would also eliminate environmental emissions that would usually be generated from pump operation. Furthermore, energy usage and costs associated with pump operation would also be non-existent. However, the construction/production of the components of the gravity-fed RWH systems would always result in environmental burdens as assessed using the SimaPro software. Hence, recommendations for alternate materials that are more environmentally friendly may be possible for future endeavours.
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Masters Degree. University of KwaZulu- Natal, Durban.