Strandfontein

Desalination for Cape Town – Numbers and Facts – South Africa

3. What about in South Africa?
In South Africa desalination is used quite widely by mines to clean up polluted mine water and acid mine drainage. Small to medium-scale desalination has also been used in coastal towns during times of drought. Six municipalities are currently using small-scale reverse osmosis plants to desalinate water for bulk water supply.

Mossel Bay has a medium size desalination plant capable of producing 15 million litres of potable water per day but the plant is currently on standby as the dams in the area are full. Standby mode requires continuous maintenance to keep the plant functional which costs the municipality money whilst not producing any water.
The Knysna municipality has a desalination plant capable of producing 2 million litres per day which is currently shut down for maintenance and repairs. During normal operation, the plant is used at the discretion of the municipality. Currently there is sufficient water in Knysna so use of the plant is minimised due to the high operational costs.
Plettenberg (Bitou municipality) has an operational desalination plant producing 2 million litres per day.
There are two desalination plants in the Ndlambe municipality, namely the Bushman’s River Mouth and Cannon Rocks plants, that produce 1.8 and 0.75 million litres per day respectively. Both plants are currently producing at full capacity.
The Cederberg municipality has a plant in Lamberts Bay with a capacity of 1.7 million litres per day (upgradable to 5 million litres per day); however, this plant is not operational yet as it is still newly developed.
Richard’s Bay has a desalination plant that was installed during the 2016/17 drought to provide the town with 10 million litres per day. It has been operating at an average rate of 6 million litres per day. The plant has had several problems, particularly cable theft, which has interrupted supply, and excessive pressure, which resulted in pipe bursts in the areas receiving water.
4. What desalination is in the pipeline for Cape Town?
Four of the seven augmentation projects that will bring new water online for Cape Town are desalination plants. They are based at the Waterfront, Cape Town harbour, Monwabisi and Strandfontein (the latter two on the False Bay coast). These are relatively small-scale operations. The City has been criticised for initially trying to bring on smaller and quicker plants to provide water during a Day Zero scenario as these are more expensive. At one stage we were going to bring in desalination barges. Barges have only worked successfully in more sheltered sea areas in the Red Sea and the Gulf. There is very little international capacity in this market at the moment, and this is currently not a viable option for Cape Town. Barges are also generally more expensive than land-based desalination.

5. So why aren’t we doing more desalination in Cape Town?
For arid and drought-stricken coastal cities, desalination can be an important source of water which is completely independent of local rainfall. However, desalination remains the resource of last resort for most cities because it is the most expensive. Desalination takes longer to bring online than drilling the shallower boreholes in Atlantis and the Cape Flats. Desalination would also be more cost-effective at larger scales between 150 to 200 million litres per day would be the best economy of scale for Cape Town.

6. What other constraints are there?
The availability of electricity is also a potential issue. Concerns have been raised in the United States that electricity supplies in local grids are not able to accommodate new desalination plants built in response to the Californian drought. South Africa is not long out of an electricity crisis. A further energy crisis at the same time as a water shortage would place this source at risk. Some plants overseas are starting to operate with solar energy, and this could be an option for Cape Town in the long-term. At the moment most of our energy is generated using coal-fired power stations and this means our energy generation puts a lot of greenhouse gases (GHGs) into the atmosphere which is a cause of climate change – which in turn would fuel future droughts.

9. How expensive is desalination compared to other water sources?
Globally desalination is between two to four times as expensive as most other sources depending on the relative cost of capital equipment (how much has to be imported etc), the cost of energy and the cost of labour to implement other water savings. By way of comparison the costs for Cape Town would be:

Raw surface water | between R1 and R4 per kilolitre
Alien clearing to release more water from our catchments | from R6 to R15 per kilolitre
New groundwater | around R15 per kilolitre
Reclaiming and re-using treated waste water | between R10 and R20 per kilolitre
Large-scale, permanent desalination | between R10 and R22 per kilolitre
Smaller, short-term desalination | R34 to R44 per kilolitre

(LINK)

Monwabisi desalination plant starting side preparation – Cape Town – South Africa

The Monwabisi desalination plant is one of seven projects earmarked as part of the first phase of the City of Cape Town’s Additional Water Supply Programme. Site preparation is currently under way. “It is anticipated that the Monwabisi plant will produce a total of seven million litres of drinking water per day which will be fed into the water reticulation system to supplement current supply from the dams and other water sources. “A nine-week construction period is planned for the completion of the first phase comprising two million litres. The first drinking water generated by the desalination plant is expected to be fed into the reticulation system by March 2018 with the second phase of five million litres to follow on after a further nine weeks. “The plant is intended to operate for a period of two years, based on a service agreement in which the city has agreed to buy water from the service provider Water Solutions Proxa JV. The value of the tenders for the establishment and operation of the desalination plant at Monwabisi for a period of 24 months is R260m,” said the city’s mayoral committee member for Informal Settlements, Water and Waste Services; and Energy, Councillor Xanthea Limberg. Other projects include the Strandfontein, V&A Waterfront, and the Cape Town Harbour desalination plants; the Atlantis and Cape Flats Aquifer projects; and the Zandvliet water recycling project which will collectively produce an additional 196 million litres per day between February and July 2018. In addition, the city has 12 projects at an advanced planning stage. “There will be minimal risks to public health and safety, and work will comply with the applicable national health and safety regulations. All construction areas will be clearly demarcated and will be off-limits to the public. Any pipe work that is not underground will be clearly marked. The plant has been designed to ensure fast-tracked construction and production but with the smallest possible construction footprint. “The city will monitor the site and regularly test the drinking water that is produced. We are proud that the plant in Monwabisi will be our flagship desalination plant. We are truly grateful for the support of the community leadership and residents in this area. They will be true partners in this exciting and necessary development,” said the city’s mayoral committee member for Area East, Councillor Anda Ntsodo. In addition, the Strandfontein plant site preparation is set to commence which will also produce seven million litres of water per day when in full production. The evaluation of a tender for a temporary desalination plant on East Pier Road in the V&A Waterfront is in its final stages. This plant is to be located in an open-air parking lot opposite the heliports, and will produce two million litres of water per day.

Cape Town will have its first desalination plants working just weeks before the city’s dams are expected to go dry South Africa – Cape Town

That’s according to Xanthea Limberg, the City of Cape Town mayoral committee member for informal settlements, water and waste services, and energy . “Monwabisi and Strandfontein [plants] are currently scheduled [to start operating in] February but we are exploring opportunities to implement earlier, once internal funding issues are resolved,” Limberg told The Times. Mayor Patricia de Lille said earlier this month that the municipal water supply might dry up in March if usage was not reduced. Chris Braybrooke, general manager of water technology company Veolia, said completion of tendering for the desalination plants should have been six months ago and that the city’s water problem was a “ticking time bomb”. “We were quite surprised there was such a long wait for the city to invite tenders and then they asked for instant solutions,” said Braybrooke, whose company has built several desalination plants in South Africa, including the country’s largest, in Mossel Bay. “This type of tender should have [been invited at least] six months ago.” The problem was exacerbated by the poor maintenance of infrastructure. “We’re waiting for the time when citizens will run out of water. It is a ticking time bomb and people are scrambling for solutions.” Limberg said t 17 sites had been earmarked for building the plants but some were ruled out because they were in a coastal protected area. The city has recently come under fire for the way it has handled projects to exploit alternative sources of water, such as aquifers, boreholes and desalination. Senior lecturer in water-sensitive urban design at the University of Cape Town Tom Sanya said not enough was known about the environmental impact of aquifer tapping. “It’s a very unstable area and it’s possible that once you start tampering with the aquifer beyond a certain tapping point it could activate earthquakes worse than we have had in the past.” Anton Bredell, MEC for environmental affairs in the Western Cape, warned that desalination would not come cheap and ratepayers would be forced to dig deep into their pockets to pay for the new technology. “Water is going to be much more expensive. It’s a fact. We will know by how much after the tender process. It’s an argument of expensive water or no water,” he said.

(LINK)