South Africa’s prolonged drought conditions and arid environment are increasingly highlighting the country’s existing water infrastructure vulnerabilities and demand that alternative and nonconventional sources of water beyond the traditional surface and groundwater resources be explored.
Various short- and long-term augmentation methods to make up the current and future shortfall in available natural water resources are being considered. These range from reuse, rainwater and stormwater harvesting to water demand management and seawater desalination. All these options already play a role, albeit minimal, in the water resources mix.
However, the extreme drought situation in the Western Cape has seen seawater desalination being cast most prominently as a solution to South Africa’s water woes, holding out the promise that the success of Israel, which sources much of its own supply from the technology, can be duplicated.
Desalination, which produces potable water by removing the salt and impurities from saline water, such as seawater, is often identified as the ‘ultimate endless resource’ and the ‘only truly climate-resilient source of water that is independent of rain’, providing the ‘highest assurance of supply’ – assuming the energy, capital, and environmental and demand-side risks can be adequately addressed.
This will be relevant in a future where demand will exceed supply by 17% in 2030, leaving a deficit of between 2.6-billion and 3.8-billion cubic metres as demand grows beyond 18-billion cubic metres.
Despite the deployment – and success – of several small-scale desalination plants across coastal towns such as Mossel Bay, Saldanha, Knysna, Plettenberg Bay, Bushman’s River Mouth and Lambert’s Bay in recent years, large-scale desalination operations may not be the silver bullet the country is seeking to solve its severe water challenges.
The Department of Water and Sanitation (DWS) seems to be considering a long-term strategy in which 300-million cubic metres of the 16.39-billion cubic metres of water supply a year is yielded from desalinated processes by 2040, complementing a balanced water mix that includes 2.1-billion cubic metres from reuse, 3.1-billion from groundwater and 10.8-billion from surface water.
The yet-to-be-finalised draft National Water and Sanitation Master Plan compares this to a 2020 mix of 10.2-billion cubic metres of surface water, 2.7-billion cubic metres from groundwater, 1.4-billion cubic metres from reuse and 150-million cubic metres from desalination.
This includes the desalination of mine water, brackish groundwater and seawater.
“The desalination of brackish ground- water has been in operation for decades in various small towns and settlements in the Northern Cape and along the coast – sometimes for emergency supply during droughts,” the DWS explains.
New temporary seawater desalination plants are being constructed at Monwabisi, Strandfontein and the V&A Waterfront, forming part of the first phase of the Western Cape’s augmentation programme to deliver a 16-million-litre yield of water over the next two years.
Permanent plants are being considered, with an expected two or three large-scale seawater desalination projects likely to be launched within the next five years in the major coastal hubs.
Feasibility studies for large-scale seawater desalination projects on a scale of 150-million litres to 450-million litres a day have already been completed for both eThekwini and Cape Town, with the Nelson Mandela Bay municipality currently also investigating large-scale seawater desalination for future augmentation of its resources.
“Although it can be implemented as an emergency supply during a drought, it is probably not feasible or sustainable, and may result in the mothballing of the plant,” the DWS says, noting the idling of South Africa’s largest plant in Mossel Bay, at 15-million litres a day, since its completion as an emergency scheme in 2011, as its water has not been required since then.
Inland, the DWS is considering the construction of a desalination plant to treat acid mine drainage from the Witwatersrand mining basins.
“Australia’s Millennium Drought Response Desalination Programme, costing R153-billion in the last decade, has seen several plants not being used optimally, resulting in significant public financial implications,” GreenCape says in its latest ‘Market Intelligence Report’, adding some perspective to the debate.
Further, active desalination remains a relatively costly augmentation alternative; however, is seawater desalination as expensive as people believe?
Council for Scientific and Industrial Research environmental management services manager Paul Lochner says the current global benchmark is about $1 per thousand litres of water, with costs declining.
“Recent studies for desalination in a South African context, such as in Cape Town, have costed out at R12 to R18 per thousand litres for a medium-scale plant,” he explains.
In comparison, the average cost, including bulk infrastructure and treatment, of surface water schemes is about R5 per thousand litres.
The high costs of desalination are primarily a function of scale, water salinity quality and temperature, marine works requirements, network integration costs and procurement methodologies, the City of Cape Town’s ‘Water Outlook 2018’ report shows.
The report, compiled by the DWS, notes that well-managed procurement, attracting reputable international companies, and contracting through a build-operate-transfer contract, has delivered desalinated water at less than the global benchmark in many regions.
In contrast, projects contracted through an owner-engineer design-build model are exposed to cost escalation and have proved to be more expensive, with costs in the range of $2 to $3 per thousand litres.
Further, both smaller and larger plants suffer from “diseconomies of scale”, with Lochner pointing out that the smaller the plant, the more expensive the price tag at R30 to R40 per thousand litres.
This means that the emergency small- scale desalination plants in Cape Town will likely come at a cost, Lochner adds.
“It is better to plan a cost-effective scale of 120-million to 150-million litres a day, which is the optimal size to bring down the costs to the $1 (R12) per thousand litre range,” he says.
Running a plant intermittently or under capacity also drives up the costs, says Institute for Security Studies (ISS) African futures and innovation senior researcher Zachary Donnenfeld.
“It works well for Israel and the United Arab Emirates, because the major populations are close to water and they are perpetually water scarce. They do not have the same problems that South Africa has,” he says.
However, DWS notes that, with the cost of desalination decreasing, owing to advances in technology, desalinated seawater, brackish groundwater and wastewater are increasingly economically viable.
“While the use of desalinated seawater is only financially feasible for coastal areas, it will free up surface and groundwater for upstream or inland use, where water is currently transferred or released for use in coastal areas,” the department says.
Lochner agrees that small coastal regions can benefit from small-scale one-million- to two-million-litre facilities, especially on the West Coast, where climate change predications are for reduced rainfall.
“Desalination contributions need to be worked out on a case-by-case basis. It needs to be well designed to take into account any variability,” he explains, noting that it is a lot more complicated than some of the other water supply options to construct and operate.
Fix What We Have
“My approach to the department and entities: you do not want to jump [the gun on] desalination plants,” says Portfolio Committee on Water and Sanitation chairperson Mlungisi Johnson.
“Rather, deal with what we have [and] do more with less.”
An ISS report titled ‘A Delicate Balance’, compiled in conjunction with the Water Research Council (WRC), indicates that the country can bring demand in line with available supply through policies that incentivise efficiency, including tiered pricing, improving the quality of the country’s water infrastructure, which includes wastewater treatment plants, and increasing the amount of groundwater used.
“Desalination is a small piece of a very big puzzle that South Africa needs to put together to reconcile its water security using available technologies and policies,” Donnenfeld says.
“If we can elevate the country to international best practice, or close to it, in three or four key areas, including water conservation and demand management, increasing treated wastewater, and carefully increased groundwater use . . . then there will be a lot of room for improvement,” he says.
Quite simply, South Africa must use water more efficiently.
South Africa has an arid to semiarid climate, with half the world’s average rainfall at 465 mm a year, producing a total yearly runoff of about 49-billion cubic metres a year. The current reliable yield of surface water at an acceptable assurance of supply is about 10.2-billion cubic metres a year nationally. Of this volume, about 70% is stored in the country’s 252 largest dams.
South Africans use 235 litres a person daily, well above the global average of 173 litres, while municipalities use about four-billion cubic metres of water a year, of which 41% is nonrevenue water (NRW), which compares unfavourably with Australia’s NRW of only 10% and the global best practice of 15%.
NRW is the volume of water for which no income is received, including water loss, meter underregistration, billing errors, theft and unbilled consumption.
This is causing a loss of 1.6-billion cubic metres of water each year at a cost in revenue of about R9.9-billion a year.
Johnson says that 37% of NRW is due to ageing infrastructure and leaks.
The initial call-to-action report of the National Water and Sanitation Master Plan by the DWS indicates that about 56% of the over 1 150 municipal wastewater treatment works and about 44% of the 962 water treatment works in the country are in a poor or critical condition and in need of urgent rehabilitation and skilled operators. Some 11% of this infrastructure is completely dysfunctional.
These trends can be reversed through a combination of infrastructure repairs, new building codes, incentives to install water-efficient appliances and implementing a tiered water-pricing structure.
Policy measures should be supplemented with campaigns to raise awareness about the high levels of per capita water use and the inherent value of water conservation in a water-scarce country, the report by ISS and the WRC notes.
Johnson says communities on the ground need to be more alert and aware of the need to save water, report burst pipes and turn off any running taps – and this awareness needs to start at schools.
In line with fixing leaky pipes is treating wastewater, which is more practical than investing in “big shiny” technologies and is an underrated opportunity to increase the quantity and improve the quality of water in the country.
South Africa treats about 50% of its municipal water, while Israel, for example, treats 90%.
“You have wastewater that is literally going into streams. This is water that can be reused for drinking, cooking, irrigation and bathing,” says Johnson.
The ‘Water Outlook 2018 Report’ shows wastewater reuse as a less costly alternative to desalination, owing to lower capital costs and energy costs that are about half of the costs required for desalination – 2 kWh for reuse, compared with desalination’s use of 3.5 kWh to 4 kWh per thousand litres.
A 450-million-litre-a-day plant in Cape Town, for example, can potentially use about 7% of the city’s electricity demand, according to data from GreenCape.
The report says the latest engineering estimate for treating wastewater to a potable standard in Cape Town is about R7.50 per thousand litres, just more than half the cost of efficient desalination.
“Scale is reasonably important for wastewater reuse too. For example, a single wastewater reuse treatment facility for 50-million litres a day is about 15% cheaper than a 20-million-litre-a-day facility, and a single combined facility of 70-million litres a day is strongly preferred for operational reasons and is cheaper, compared to two separate facilities,” it says.
There are currently a few potable water reuse projects under way, according to GreenCape, which cites an investigation into the upgrading to a permanent 75-million-litre-a-day plant of the Zandvliet Wastewater Treatment Plant.
Groundwater could also be a game changer as an underused resource in South Africa, as it is cheaper than wastewater reuse, with both the capital and operating costs significantly lower.
The technology required is also much simpler and the energy requirements are much lower.
The DWS estimates that South Africa could significantly expand the use of groundwater; however, there is a need to accurately determine how much there is and where it is located.
The DWS estimates that close to 85% of the country’s groundwater aquifers are underallocated and that there could be as much as 4.8 km3 of exploitable groundwater.
“There is still substantial potential for groundwater development in South Africa. Nationally, the total estimated yield of available, renewable groundwater is between seven-billion and ten-billion cubic metres a year, while between two-billion and four-billion cubic metres a year is currently being used,” says GreenCape.
The ‘Water Outlook 2018 Report’ shows that Cape Town has successfully developed a sandy aquifer groundwater scheme, with recharge, in Atlantis and Silverstroom; it yields 12-million litres per day.
Drilling is also under way at both the Cape Flows Aquifer and the Table Mountain Group Aquifer.
Lochner warns, however, that pumping the groundwater can potentially be unsustainable and wastewater reuse can be limited as well, owing to the limited amount of available water.
“What South Africa needs”, says Donnenfeld, “is a coordinated approach to water management, across all three tiers of government, as well as civil society and individual residents.”
The national government can invest in bulk water infrastructure, while provincial and municipal governments can do more to reduce demand. Individuals also need to use less water.
“There is room for all these technologies and solutions, but that room must be measured in such a manner that it is sustainable and brings together all stakeholders under one roof,” Johnson concludes.