Other Features >


Deciphering Desalination


As conventional water resources are strained to meet the growing national demand desalination is increasingly being explored as an alternative. Severe drought in the Southern Cape between 2009 and 2011 fast-tracked the successful development of small municipal desalination plants to remove salt from seawater along the Garden Route. But to date, no large-scale desalination plants have been developed, largely due to high capital and operating costs. The evolution of technology and cost improvements are, however, positioning desalination as a strong future contender for South African coastal cities.

Desalinated seawater currently costs between R14 and R15 per kilolitre, with energy and treatment costs as well as infrastructure capital being key contributing factors.

“Historically, South Africans have been paying far below the real cost of water,” says Louise-Mari van Zyl, director of Cape Environmental Assessment Practitioners (Cape EAPrac), which facilitated the environmental impact assessment process for South Africa’s first desalination plant in Sedgefield. Low water costs extend beyond under-valuing of natural resources. “Many of South Africa’s large dams, water infrastructure and treatment plants have been

built and paid off a long time ago. This drastically reduced the costs of conventional water,” says Kevin Meier, Manager of Umgeni Water’s Planning Services Department. The cost of water from a new conventional water treatment works varies depending on location as it is very site specific, but generally could range from R8/kl to R12/kl. By comparison, any alternative will be more costly, even more so for advanced technology.

Technology and Advances

All South Africa’s municipal and industrial saltwater desalination plants use reverse osmosis (RO) membrane technology. Intake water is forced through membranes at high pressure, allowing purified water through and retaining salt as brine. From the intake water, 45% becomes potable, while the remaining 55% of concentrated saltwater is discharged into the ocean. These processes and supplying of water require an operational energy consumption average of 4kWh per kilolitre.

However, this is not a limiting factor in the South African context. “There is a major international drive for lowering energy requirements and some new technologies, such as Desalitech and niche applications, can be expected for the future,” says Abrie Wessels, Veolia Water Technologies South Africa’s Cape regional general manager.

Design for Demand

Operational costs are currently preventing local Southern Cape municipalities from operating their desalination plants. The possibility to mothball the seawater plants when not required was a key design planning criteria. “Desalination remains an emergency option for when all other resources have been entirely depleted or are no longer cost-effective,” says Van Zyl. Likewise for the Mossel Bay plant.

Large-scale desalination plant planning for Durban and Cape Town is ongoing.

Maintenance and National Funding

“The maintenance cost of repeated annual repair and protection against corrosion is seriously underestimated for the marine environment,” says Wessels. Using higher cost stainless steel offers some mitigation but siting again comes into play: “Because of the high cost of the large seawater delivery infrastructure, inlet and outlet pipeline distances have to be kept to the minimum,” says Meier. RO membranes need to be replaced every five to seven years.

Maintained in zero mode, full operation of the Southern Cape plants is attainable within a short re-instatement period of between one and two months. Whether securing water for significant future town or industrial expansion or drought, “the Mossel Bay Municipality is now positioned to generate water, which was previously not possible. The current challenge is that a zero mode phase can extend over a long period, but constant maintenance of plant components is still needed. Under a specialist service provider contract, the cost for annual zero mode maintenance was R4.5 million. To manage this, the Mossel Bay Municipality established an internal municipal management team, which has drastically reduced zero mode maintenance costs,” explains Amanda Murray, manager of the Mossel Bay Municipality’s technical services department.

The Southern Cape desalination projects were largely possible because of National Treasury drought relief funding after the region was declared a disaster area. In general, “the cost of desalination will come down significantly if given State grant development funding, making it more viable,” says Meier.

Assess for Environmental Risks

Environmental factors are critical. “If the marine environment is not carefully assessed and chosen, desalination could become extremely problematic,” says Melissa Mackay, environmental assessment practitioner of Cape EAPrac. Brine discharge is one environmental risk. “A high energy coastline is necessary, with sufficient water movement to disperse the brine, otherwise brine accumulation could potentially suffocate marine life.

It means that desalination in its current form is not viable for all coastal locations,” says Mackay. Yet there are indications the development of desalination plants weigh less heavily on the environment than conventional water supply alternatives such as off-stream dams and in-stream weirs.

Environmental Resilience

Besides human and industrial use, water reserves need to be designated for ecological functioning as well.

“This is justification for municipalities to motivate that exhausting all natural resources before looking into alternatives such as desalination is not possible,” says Mackay. Climate change also necessitates alternative solutions. “The Southern Cape hardly ever relied on water storage because of constant rainfall across seasons. But suddenly, there are consecutive months with no rain,” says Mackay.

Future Planning

Previous droughts may have focused attention on desalination, but “do not wait for drought. The current desalination plants provide specific South African references and experience on planning, operation and maintenance costs,” says Wessels.

“Determining the viability for a city is complex and a site specific calculation. But for coastal cities, it is definitely a resource option that should be considered,” concludes Wessels.

By Francini van Staden

See earthworks issue 31 Apr-May 2016 for the full feature.

Read More »

UCT Water

UCT Water Research Unit

A new water research unit at the University of Cape Town aims to help create a sustainable water future.

South Africa is ranked as the 30th driest country in the world, according to the Department of Water and Sanitation (DWS). Projections noted in National Treasury’s 2012 Budget Review are concerning and show that by 2030 the demand for water in the country will outstrip the ability to supply it. The reality of water shortages hit home more recently as the ongoing drought wreaks havoc across the country. It is therefore essential to find new, innovative and scalable solutions to ensure water security into the future.

Read More »


Back to basics: Waste-to-liquid fuel


Pyrolysis, a process that converts hydrocarbon products like waste plastic and tyres back to their roots of liquid fuel, is a potential solution to reduce waste to landfill. earthworks looks at Japanese technology being tested locally and a homegrown company ready to enter the market.

Read More »


Eco-engineering with floating wetlands


Solving South Africa’s devastating water issues, compounded by drought and destruction of wetlands, has fallen to a new generation of engineers who work ecologically with nature, in many cases mimicking natural phenomena like floating wetlands.

Read More »


Mechanical concrete: A road building revolution


Making a leap in waste beneficiation, the mechanical concrete system of road building transforms waste tyres into ‘geo-cylinders’, which function as lateral reinforcement elements and make road construction more affordable, faster and more sustainable.

Read More »


Holding energy and promise: the Eco-mc2 compressed air energy storage solution

The Eco-mc2 compressed air hydraulic energy storage system could revolutionise energy storage in South Africa. A winner at the WWF Climate Solver Awards earlier this year, a top five finalist in the Eco-Innovation category of this year’s Eco-Logic Awards and a top 10 finalist in the Global Cleantech Innovation Programme, its application is particularly relevant for renewable energy where conventional battery storage is thought to be expensive, bulky and environmentally toxic.

Read More »


Waste not, want not: Bronkhorstspruit biogas to electricity

South Africa’s first commercial biogas plant, in Bronkhorstpruit, east of Pretoria, is the product of perseverance, good partnerships and lateral thinking. For over eight years, entrepreneur Sean Thomas, CEO of Bio2Watt, waded through untested waters, eventually setting a precedent for future biogas-to-electricity projects with a 10-year off-take agreement with BMW.

Read More »


South Africa’s renewable energy projects

Globally, the renewable energy revolution is gaining momentum, and renewable resource-rich South Africa is striving to keep up. Bloomberg New Energy Finance (BNEF) recently reported that a tipping point has been reached and the world is now adding more renewable power capacity each year than new coal, natural gas, and oil capacity combined.

In April 2015, the South African government announced the successful projects in the fourth round of the renewable energy independent power producers programme (REIPPP), bringing the total number of projects approved to 79. The 41 projects already online are making a valuable contribution during the current power crisis South Africa is facing, and the renewable energy rollout is gathering pace in the country.

Read More »


Roofing: Choosing cover

Roofs can be divided into two categories: lightweight structures characterised by trusses, beams and purlins with some form of cladding; and slabs, which take the building’s structural form to the roofing level. Both offer their own set of opportunities and challenges.

Read More »


Between a rock and a hard place

Green building is a space of innovation, and in its pure form, sustainable practice encourages the growth of micro-economies, both on-site and around the development of new technologies.

But in South Africa, for those who have innovated ways of building with natural materials such as stone, clay and straw-bale, the path to certification is a difficult one, and one that small-scale operators and start-ups often have not been able to survive.

Read More »


Liesl Hattingh
021 447 0822
082 777 5746

Managing Director

Eugene Hugo
021 447 0822
071 672 3545

Sales Director

Suna Dindar
021 447 0822
076 010 1045


021 447 0822

Cape Town: Unit 105A, 1st floor, The Woodstock Exchange, 66 Albert Road, Woodstock, 7925
PO Box 1189, Woodstock, 7915

Tel: 021 447 0822 | Fax: 086 524 8930