As South Africa faces a deepening water crisis, desalination should be considered as part of the solution towards water security.
The 2 800 km coastline, stretching from Mozambique to Namibia, positions South Africa well to use sea water to help combat water scarcity, says ABB Energy Industries South Africa ABB power and water manager Joyce Moganedi.
“South Africa is a water scarce country. Our situation is becoming more desperate because of climate change, water pollution and overwhelmed water infrastructure. The holistic solution to ensuring clean, safe water for all South Africans must include desalination. It is increasingly being used by countries around the world to close gaps between water supply and demand,” she explains.
“Getting potable water from sea water must be part of the solution if we are to avert South Africa’s worst-ever water crisis.”
While the energy requirements of a desalination plant can account for up to 50% of its running costs, the high energy consumption and costs associated with desalination can be mitigated by having the right technology and systems in place.
“In the last few decades, production costs in desalination plants have fallen fourfold thanks to the emergence of highly efficient electrical equipment,” says Moganedi.
She highlights ABB’s three-pillar approach to desalination which includes the constant development of highly efficient products such as drives and motors that contribute to a desalination plant’s electricity bill; accurate energy audits and advice for plant modifications to help the overall energy footprint, including using a variable frequency drive to control the process; and leveraging the full potential of Industry 4.0.
“Digital solutions optimise the process by giving operators insights to make immediate decisions that enable the same production levels, but with less energy,” she pointed out, adding that variable speed drives and motors maximise plant efficiency and productivity levels, reduce energy consumption by up to 60% and reduce the mechanical and electrical stress on pumps and aeration equipment, significantly lowering maintenance costs.
“Extending the life of assets makes desalination more affordable. When digital solutions are applied to one of the most critical pieces of equipment in a reverse osmosis plant, the membranes, the condition of the membranes can be chosen as a main parameter to decide the regeneration point, rather than production volumes or time. ABB’s solutions are modular and can be scaled up from equipment level to plant level and even at a network level,” explains Moganedi.
She further cites several examples of some desalination projects that South Africa could emulate, including the world’s largest desalination plant in Taweelah, in Abu Dhabi, United Arab Emirates, which will be able to process over 900 000 m3 of seawater a day and is scheduled to be fully operational in the fourth quarter of 2022.
“The power solutions provided by ABB will enable this facility to set new benchmarks for its size, efficiency and cost by using the lowest amount of energy per cubic metre of water produced.
Meanwhile, ABB supplied a turnkey electrical solution to power the Algeria-based Magtaa membrane-based reverse osmosis seawater desalination plant. This plant has a designated capacity of 500 000 m3 a day of drinking water to serve about five-million people.
“ABB was responsible for the design, engineering, supply, installation and commissioning of the electrical plant system, which included constructing a 220 kV outdoor substation to provide power to the facility and supply products such as power transformers, medium-voltage drives and a range of medium and low-voltage switchgear,” Moganedi says.
Other projects using ABB solutions are the Jeddah Reverse Osmosis Desalination Plant Phase 1 and the Yanbu Reverse Osmosis Desalination Plant, both in Saudi Arabia.
“The Jeddah plant has a capacity of 48 848 m3 a day. ABB supplied a distributed control system using state-of-the-art digital technology for the Yanbu plant, which consists of five major components: a seawater supply system, a feed water pre-treatment system, high-pressure pumping, reverse osmosis modules and a permeate post-treatment system.”
In Oman, ABB contributed to the development of one of the largest reverse osmosis plants in the Gulf: the Al Ghubra plant, which has a potable water production capacity of 191 000 m3 a day; equivalent to supplying a population of 800 000 people using reverse osmosis to desalinate sea water.