South Africa has long faced water shortages because of inconsistent and insufficient rainfall. With an average annual rainfall of 497mm—nearly 50% lower than the global average of 860mm—the country struggles to meet increasing water demands. Provinces like KwaZulu-Natal, Mpumalanga, Limpopo, and North West face the most extreme water shortages, and advanced desalination plants are helping maintain a reliable water supply. Desalination is the process of converting seawater into consumable water for communities and industries. So, what are the advantages of these plants? As water treatment experts, we are happy to share why seawater desalination systems are becoming popular and their benefits.

Desalination Plants Offer Reliable, Drought-Resistant Water Supply

South Africa’s water shortages are often caused by droughts and fluctuating seasonal rainfall. Unlike freshwater resources that are vulnerable to climate change, desalination plants offer a consistent source of water throughout the year, making them essential during dry seasons. Coastal cities such as Cape Town have already adopted desalination as a measure for guaranteed water supplies during periods of drought.

How Desalination Delivers High-Quality Water

NuWater’s full scale seawater desalination systems, using Seawater Reverse Osmosis (SWRO), are highly effective in delivering clean, safe water. This process is based on osmosis, a natural phenomenon where liquids with different concentrations pass through a special membrane. Naturally, the liquid with a lower solute concentration flows through the membrane towards the higher concentration until equilibrium is reached.

However, in reverse osmosis, this process is performed in “reverse”. The system passes seawater through the membrane under pressure, as it contains high concentrations of salt and impurities. The membrane allows only water molecules to pass through while preventing salts, contaminants, and other pollutants. Therefore, purified water is collected on one side, while the remaining seawater with concentrated salt is left on the other side.

The SWRO system begins with the extraction of seawater, which is then passed through a first-stage filtration system capable of eliminating large particles such as oil, seaweed, and debris. After pre-treatment, the water is treated by reverse osmosis, resulting in two distinct streams: fresh water and a brine solution, which is highly concentrated salty water. The brine is then gradually diluted with seawater and discharged back into the ocean without affecting marine life.

Versatility In Application

Desalinated water undergoes further treatment through remineralisation and chlorination, making it suitable for a variety of applications including drinking, agriculture, industry, and power generation. SWRO systems are also highly energy-efficient, using four and a half times less energy than other desalination processes, making them environmentally and economically friendly.

Environmental Concerns And Mitigation

While desalination offers significant benefits, its environmental impact must be carefully managed. One of the primary concerns is the intake of seawater, which can inadvertently capture marine life such as fish larvae, plankton, and other microorganisms, reducing local fish populations. This bycatch can disrupt marine ecosystems in coastal areas where the balance of biodiversity is delicate.

Seawater desalination plants generate a highly concentrated brine as a byproduct. When discharged back into the sea, this brine can increase salinity levels in the surrounding waters. High salinity is toxic to marine life, and combined with chemicals used in the desalination process, such as biocides and antifouling agents, the discharge can further harm aquatic ecosystems.

To address these environmental concerns, modern desalination plants employ several mitigation techniques. Many now use submerged, low-velocity intake systems to reduce the capture of marine organisms, protecting local biodiversity. Plants can also dilute the brine with other water sources or mix it with wastewater to reduce its salinity before discharging it back into the ocean, reducing its impact on the environment. Some facilities have adopted brine management technologies that enable the recovery of useful salts and minerals, further reducing waste. Additionally, desalination is an energy-intensive process, and when powered by fossil fuels, it contributes to greenhouse gas emissions. However, using renewable energy sources such as solar or wind power into the process can make desalination more environmentally sustainable.

Conclusion

Desalination of seawater stands at the forefront of addressing water scarcity in South Africa where freshwater ecosystems are under pressure, by providing a reliable means of producing the finest water.  As energy consumption in desalination processes continues to decrease, the performance and sustainability of these systems will improve, making desalination an increasingly important solution to water shortages.

At NuWater, we have the best desalination systems and we’ve been leading in water treatment for many municipality regions and other sectors. If you’re thinking about how desalination plants work, reach out to us today to learn how we can assist in creating a sustainable water future.