Assessing the energy and carbon footprints of exploiting and treating brackish groundwater in Cape Town

Abstract

South Africa has been facing significant challenges in meeting demands in its water and energy sectors in recent years and planning for both sectors has mostly been done separately. The City of Cape Town has started to supplement its dwindling conventional freshwater supplies with groundwater, wastewater and seawater, in light of the drought that commenced in 2015. The Cape Flats Aquifer in Cape Town represents an important resource whose yield could be increased to 85 000 m3/ day through artificial stormwater recharge in the Zeekoe Catchment alone. The abstraction and treatment of this water would require significant amounts of energy and thus this paper explores the links between energy usage in the water sector and its carbon footprint. The three alternatives investigated were ‘centralised’, ‘desalination’ and ‘decentralised’ approaches. The former two are centralised treatment mechanisms to produce potable water utilising existing and new treatment infrastructure, respectively, and the latter proposed minimal treatment for non-potable end-users. The energy intensities of the alternatives were evaluated by identifying energy-intensive components and carrying out a preliminary design of the networks and the required treatment mechanisms. South Africa’s future potential electricity mixes were used to conceptualise the significance of the associated energy demand. The centralised approach’s energy intensity was found to be the lowest of the three, ranging from 1.16 to 1.57 MJ/m3, while those of the decentralised and desalination approaches ranged from 3.57 to 7.31 MJ/m3 and 7.41 to 9.62 MJ/m3, respectively. The Western Cape Water Supply System has an installed capacity of 47.6 MW which could potentially increase by at least 2.7%, 5.7% and 12.3% through the centralised, decentralised and desalination options, respectively. This paper contributes to a growing knowledge on the water–energy nexus in South Africa.

Towards improved Water-Energy-Climate Change nexus assessment in South Africa: A Participatory Approach

“…Despite the constitutional mandate requiring that key actors, such as government departments, local communities, industry, experts and researchers, are consulted to ensure meaningful, well-informed and effective policy instruments within the water, energy and climate change sectors, application of the PA appears to be lacking. The prevailing lack of coordinated and integrated approaches in the widely touted sectoral policies [12,13,11,3] demonstrates limited application of the PA in planning and implementation processes. These shortcomings suggest a lack of understanding of the interlinkages between the key socio-economic and environmental processes in the WECC nexus.…”

“…As is the case globally, South Africa lacks integrated approaches for the management of different nexus configurations such as WECC [10,11,12]. This is as demonstrated by the preponderance of fragmented approaches in the planning and development of policies and strategies for addressing growing water, energy, and climate change challenges in the country [13,3]. This observation, coupled with a lack of urgency to implement mitigation measures as proposed by different scientists in the country, suggests that there is limited coordination and collaboration among key stakeholders such as researchers, policymakers and communities.…”

Applying the Water-Energy Nexus for Water Supply—A Diagnostic Review on Energy Use for Water Provision in Africa

“…Tanzania [25] A life cycle assessment of desalination and mine-water reclamation as alternatives for portable water supply. South Africa [58] Assessed the energy and carbon footprints of using centralized, decentralized or desalination options in treating brackish groundwater, Cape Town.…”

Potential Reduction of Carbon Burden for Senak Seawater Desalination Plant in Malaysia

“…Meanwhile, the utility of chemicals consisting of Polyaluminium chloride, Polyacrylamide, Soda ash, Hydrochloric acid, Sodium hydroxide, Chlorine, Sodium hydrogen sul te, Sodium hypochlorite and Calcium carbonate contributed a total of 0.146 kg CO 2 -eq (4%). According to Gobin et al (2019), the quantity of chemicals will be higher when the productivity of potable water production is higher. For example, the use of lime, uoride, and carbon dioxide to reduce water hardness and produce good quality water can contribute to the carbon footprint.…”

“…Data loss and lack of information that are related to materials disposal, construction of plant infrastructure, tanks and transportation services are the most di cult issue to model the indirect carbon footprint emission. According to Gobin et al (2019), limited data accessibility such as chemicals and energy via data extraction using different models such as GaBi, West is the major limitation in the research of carbon footprint desalination in Cape Town, Africa. Therefore, further research needs to be done with the involvement of sensitivity analysis towards the construction, operation and dismantling phases.…”