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South Africa, Our Burning Planet

Balancing cost and quality: Cape Town's ambitious desalination project under fire from residents and experts.

Balancing cost and quality: Cape Town's ambitious desalination project under fire from residents and experts.
The recommended option for the proposed Paarden Eiland Desalination Plant in the Port of Cape Town. (Photo: City of Cape Town)
Kristin Engel
By Kristin Engel
26 Feb 2025
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As the public consultation for a permanent R5-billion desalination plant at Paarden Eiland gets under way, the City of Cape Town says this proposed project is necessary to secure reliable, climate-resilient water sources. But residents remain wary of the pollution risks of the proposed site, the high costs and potential tariff hikes.

It is still early days but the City’s plan to establish a permanent desalination plant in Paarden Eiland is moving forward with advanced pre-treatment, reverse osmosis and, potentially, UV oxidation on the table to eliminate contaminants from seawater before it’s provided as drinking water.

A desalination plant removes contaminants and chemicals from seawater, allowing it to be used for drinking, irrigation and industrial purposes. The proposed plant in Paarden Eiland is a part of the City’s New Water Programme to secure a more long-term water supply in the wake of climate change and increasing drought risks. 

When Cape Town expected to run out of municipal water due to a severe drought, it was a wake-up call that it needed to diversify its water sources. Now the City is trying to reduce reliance on rainfall by investing in desalination, water reuse, clearing of invasive plant species and groundwater schemes. 

Read more: Cape Town set to purify treated sewage water for drinking purposes

But as public meetings unfold regarding the proposed desalination plant, concern is swelling among residents and groups about the water intake being close to the harbour where previous projects were problematic, its proximity to the highly polluted Black and Diep River outflows and the current discharge of about 50 million litres of raw sewage into Table Bay from the marine outfalls, and the South African National Standard (SANS) 241 Drinking Water Specification. 

A second public meeting concluded on 19 February 2025 in Milnerton where the City sought to engage residents and solicit their views on the feasibility of the City providing desalinated drinking water through an external mechanism at the proposed Paarden Eiland site. 

This is part of a broader public participation process under way. The deadline for submissions is Monday, 3 March 2025, with more set for later this year.

Desalination Runoff into the Western Cape Water Supply System dams. Cape Town is prone to drought and the City of Cape Town says Day Zero was a wake-up call. Cape Town will experience this, and possibly worse, in future. (Photo: City of Cape Town)


The location and costs of treating polluted water 


Caroline Marx, director of RethinkTheStink, which advocates for the responsible management of our water, said modern water treatment is capable of treating polluted water to high standards, but doing so incurs extra costs compared with treating unpolluted water.

Marx told Daily Maverick that the choice to source seawater near Paarden Island was strange given that it was “perhaps the most polluted spot on the coastline”.

This was because it was “only about 5km from the Green Point marine sewage outfall, [which] discharged over 40 million litres of untreated sewage daily”.

In addition, the site was downcurrent from the harbour, risking hydrocarbon pollution which fouled filters very quickly, even in minute quantities. Marx added that the site is also close to both the Diep River and Salt/Black River estuaries, which Marx said are both massively polluted.

“Extra costs incurred to treat polluted seawater rather than cleaner seawater will be passed onto residents.”

At the meeting, Peter Walsh from RethinkTheStink too questioned the proposed Paarden Eiland site:

“Where they are going to acquire that water from is probably the most polluted stretch of ocean in the whole of the Western Cape. How are they going to clean it?

“If they were extracting the water from a clean water source, we wouldn’t be having this conversation… I can’t see it [the desalination plant] happening without a higher standard because if you give me that water back to drink, I’m not going to drink it.”

The national South African drinking water quality guidelines, SANS 241, were also a topic of debate among residents and groups who were concerned that standards were inadequate for the desalination plant since they did not impose limits on many chemicals of emerging concern.  

These chemicals come from household cleaning and other products used by residents, which are found in sewage in coastal waters, from the City’s marine outfalls at Green Point, Camps Bay and Hout Bay.

During the second public meeting on 19 February 2025, which was part of a broader public participation process currently under way, as required by section 78(3)(b) of the Municipal Services Act, residents spoke out about this.

Resident Ryan Harris said desalination technology was good but it was well known that SANS 241 was not sufficient for some of the contaminates that accumulate in the environment, and that reverse osmosis would not remove them. 

The recommended option for the proposed Paarden Eiland desalination plant in the Port of Cape Town. (Photo: City of Cape Town)



Harris also highlighted that reverse osmosis had been documented as a good technology but that maintenance and operational costs were a nightmare. “The City has an absolutely horrific track record when it comes to reverse osmosis. The various other small-package plants were disasters.”

In response to this, the director of bulk services at the City’s water and sanitation directorate, Mike Killick, said the SANS 241 standards were being revised and that this would include a risk-based assessment.

“The City has been implementing a mix of groundwater, water reuse and desalination. In fact, water reuse is about half the price of desalination but it is also not entirely climate resistant because when we cut our demand, there’s less wastewater being produced,” Killick said.

Harris was also concerned about the R5-billion price tag for a plant that would service only a fraction of Cape Town, as well as the consequent changes to tariffs. 

“If you took it [the R5-billion] and invested it into water reuse and loss management, and various other interventions, I suspect you would get a massive better return on your money than that. As a taxpayer, I have a big concern about that,” he said.

City responds to public concern 


On selecting Paarden Eiland as the site for the desalination plant, the City said it is considering locations for desalination plants between the Cape Town harbour and Atlantis. 

Zahid Badroodien, the mayoral committee member for water and sanitation, said the harbour site was advanced to feasibility ahead of other options because it has a lower anticipated environmental impact; was close to water and electricity infrastructure; the small site available lends itself to construction of a medium-sized plant; and helps secure water supply for the Cape Town CBD (where major development is planned). 

Regarding public concerns about the environmental impact, cost and energy demands of the plant, Badroodien said desalination had a high energy demand and would rely on grid supply, but that energy recovery devices were included in the plant’s design to reduce its energy consumption as much as possible.

The City confirmed that it was not just looking at the general parameters of SANS 241, but other parameters as well, and that more information about this would be shared once the environmental impact assessment was completed.

About the SANS 241 concerns, Badroodien said the City will implement risk-based water quality monitoring, as required by SANS 241, for the design and operation of the plant. 

This would include consideration of contaminants of emerging concern and implementation of water safety planning protocols, following water industry best practices.

Badroodien explained that said desalination removes salts and minerals from water, making it safe to drink. Calcium is then added back into the treated water to stabilise it. 

Since some people are more sensitive to taste, they might experience a slight “flatness” in the water, but the water from the plant would also be blended with the current surface water supply.

Given the projected plant’s proximity to the polluted Black and Diep River outflows, concerns were raised about how the City will ensure that contaminants, including raw sewage currently being discharged into Table Bay, do not compromise the quality of desalinated water. 

Badroodien said the City implemented a comprehensive water quality monitoring programme that assesses potential contaminants in the seawater and dispersion thereof within the proposed plant intake area, which will be modelled during further investigations. 

Findings from this and other related studies in the area would inform the design and operational processes of the plant.

To ensure the highest water quality, Badroodien said the plant will use advanced pre-treatment, reverse osmosis and, potentially, UV oxidation to eliminate contaminants.

The City has started a scoping and environmental impact assessment for the plant. A pre-application report was opened to the public in late 2024. More public engagement is planned for early 2025 before the final scoping report is submitted for approval.

After that, a draft environmental impact report, including specialist assessments and an environmental management programme, will be compiled.

Value for money of the plant and tariff impacts 


“While desalination is a significant investment, it provides a reliable, climate-resilient water source as contemplated in the Water Strategy,” Badroodien said.

Construction would cost about R5-billion, the start of which was dependent on the outcome of the section 78 study, which was under way, and the procurement processes which need to follow after the City makes a decision.

A feasibility study, conducted with National Treasury’s Government Technical Advisory Centre (GTAC), was assessing the most cost-effective financing model for the plant.

“Water scarcity is increasing globally,” Killick said. “The cost of doing nothing could be far greater in the long run.”

Badroodien said the new supply schemes will have an impact on tariffs, but it was a wise investment for Cape Town’s shared water future and “will help ensure that we can keep the water flowing and avoid exorbitant restriction tariffs in times of drought”. DM

https://www.youtube.com/watch?v=REeWvTRUpMk

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