Desalination: A Technology on the Rise

When investing in the stock market, wise financial advisors tell us that it’s essential to watch the long-term growth of your investments rather than the day-to-day activity. The same is true for the desalination market. While desalination has recently struggled with logistics barriers due to the COVID-19 pandemic and global conflicts, a twenty to thirty-year timeline shows a technology on the rise, with larger and more desalination projects being built in every region of the globe.

As traditional water resources deplete and become contaminated, governments and industries are seeking alternative water supply and management solutions that meet both quality and capacity demands. Like any other water treatment process, desalination has advantages and disadvantages, ranging from reliability and high water quality to significant capital investments, ?energy requirements, and brine disposal. However, committed desalination experts continue to reduce desalination energy requirements and increase operations efficiency via digitalization and energy recovery systems.

?Taking a long-term view, BW Water has invested heavily in desalination’s future, with in-house experts who have designed, constructed, and operated desalination plants worldwide.

Desalination Basics

Converting salty water from oceans, seas, and saline groundwater into freshwater requires multiple steps, starting at the feed water source. The Intake System is the first stage of the desalination process. Feedwater water quality, like any water source, can impact the amount of anti-foulant chemicals needed, pretreatment configuration, and the likelihood of RO membrane fouling. Treatment facilities use two common intake methods to transport salty water to their treatment process.

Open-Ocean Intake:

Open intakes include an inlet structure with coarse bar screens, a conveyance pipeline or channel connecting the inlet structure to an onshore concrete screen chamber, and mechanical fine screens in the chamber. The intakes can be onshore or offshore. Offshore intakes with vertical inlet structures are most common for seawater desalination projects.

The offshore inlet structure is usually a vertical concrete or steel well or pipe located at or above the ocean floor and submerged below the water surface. Onshore intakes use the same structures to source water along the shoreline, reducing pumping requirements. Because these methods source water from the sea, screening is required to prevent impingement, where sea life gets caught in the intake screen, and entrainment, where small sea organisms are drawn through the intake and into the desalination plant. Impingement and entrainment can severely affect open intake infrastructure and the cost of treatment.??

Subsurface Intake:

Subsurface intake pumps water from beach wells, infiltration galleries, and slant wells to pretreat seawater via filtration through sandy ocean floors, making them best suited along ocean bottoms and shorelines. Subsurface intake requires a slower flow rate, preventing its application in medium and large-scale desalination projects that demand large volumes of seawater. Its inherent sand pretreatment improves the quality of influent entering the plant, reducing treatment costs compared to open-ocean intakes. However, subsurface intake has limited applications. Intake must be near moving water, “flushing” sediment and organic matter around the intake. Water sources low in oxygen often feature higher concentrations of manganese and iron, requiring more pretreatment at the plant.

Subsurface intake’s feasibility also depends on local hydrogeology. The most favorable hydrogeological conditions for subsurface intake are highly permeable geological formations, like sand, limestone, and gravel. The proximity of subsurface intakes to freshwater aquifers must be considered as well. Removal of large volumes of water from an onshore coastal aquifer hydraulically connected to a freshwater aquifer may result in lowering the water levels in the existing freshwater supply wells in the area. Beach erosion can also threaten these intake infrastructures, rendering them unusable not long after installation.???

From the intake, the salty water goes through pretreatment step. Turbidity and suspended solids that can include algae and plankton are the most common foulants of RO membranes in the desalination process and present unique challenges that conventional water treatment plants don’t experience. Dissolved Air Flotation (DAF) systems are commonly used for pretreatment at seawater reverse osmosis plants in Africa, Latin America, and the Middle East, removing algae and plankton loading at 95-98%. In addition to DAFs, media filters, ultra/microfiltration, and sedimentation technologies pretreat seawater and brackish water before the RO process.

In BW Water’s experience, the three most common pretreatment technology combinations are:

• DAF to Media? Filtration (Gravity or Pressure)
• DAF to Membrane Filtration
• Sedimentation (Hydro-PAQTM) to? Filtration (Gravity or Pressure)

After the rigorous pretreatment, water is ready for RO treatment, followed by remineralization and disinfection.

While seawater is often mentioned when discussing desalination, the technique can also be used to treat inland sources. Seawater reverse osmosis (SWRO) desalination constitutes many of the projects built so far. It applies to coastal regions, where seawater is nearby and plentiful. For inland applications, the same desalination process applies to brackish water reverse osmosis (BWRO), where surface water or groundwater potentially impacted by saltwater intrusion and other pollutants depends on the RO process to meet drinking water and industrial process standards.

By The Numbers

The Gulf States on the Arabian Peninsula adopted desalination early, currently hosting ~50% of the world’s active desalination projects. Neighboring Egypt and other MENA states with similar climates and water demands have also adopted desalination as a water supply solution. Meanwhile, Asia Pacific has quickly adopted the practice in more recent years, with China planning eighteen new SWRO plants in the near future. Outside of these regions, desalination is seeing more consideration.

Between 2021 and 2022, ninety SWRO plants and ninety-two BWRO plants were awarded globally. As of 2022, desalination plants contributed 95 million m3 per day (25 billion gallons/day) to the world’s freshwater supply. Including contracted and under-construction projects, the number is closer to 108 m3 per day (28 billion gallons/day).

Energy consumption is one of the biggest hurdles regarding desalination adoption and one that the industry continues to focus its innovation. Energy recovery devices are becoming standard in the design and construction of desalination plants, reducing energy consumption by 30% compared to systems that don’t implement them. In addition, new membrane construction has been been developed and implemented to allow lower pressure/energy requirements. Modified configurations are also now available to increase efficiency by harnessing water from the brine stream. And like the rest of the water industry, digitalization is also being employed at SWRO and BWRO plants to optimize operations costs and decisions.

The size of desalination projects continues to grow as well. In Saudi Arabia, which already hosts the largest desalination plants in the world, mega desalination projects continue to be designed, built, and commissioned, such as the Jubail Independent Water Project, which will produce one million cubic meters (264 M Gallons) of fresh water daily. Projects like this have taken global desalination capacity from 25 million m3 daily in 2002 to almost 100 m3 per day in 2022, quadrupling the world’s desalination volume in the past two decades.

BW Water’s Global Desalination Footprint

BW Water has provided desalination facility design, engineering, fabrication, installation, and operational services worldwide for over thirty (30) years with our Tampa, Florida, USA office bringing extensive experience and history in desalination. In addition, we have two dedicated facilities in Penang, Malaysia, and Dresden, Germany, to fabricate and assemble our systems, subsystems, and components under the highest quality controls with highly skilled certified welders and tradespeople.

BW Water also builds custom containerized (“plug and play”) desalination solutions to meet different customers’ specific requirements, like mobilization, simplified installation, easy O&M, smaller footprint, and full automation. This product typically supplies water to:

• Coastal and Island Regions
• Island Infrastructure Development Projects
• Emergency and Disaster Relief

BW Water has operated Water Treatment Plants for many years. The experienced operation and maintenance teams can source spare parts, conduct testing, and maintain long-term plans to satisfy the plants’ optimal operation level. Our years of experience in the marketplace have accumulated into SWRO and BWRO installations around the globe.

Future of Desalination

Global water security requires the same thinking as a stock portfolio. It will require a diverse assortment of sources and treatment technologies in order to meet the needs of communities and industries. BW Water believes that desalination will be increasingly relied on as a water treatment technology to meet freshwater demands. As emerging treatment technologies make the process more feasible, sustainable and cost-effective desalination will likely play a vital role in securing water for all.

BW Water has designed, constructed, and operated desalination facilities in every region of the world. With our expertise, any community or industrial facility can equip themselves with a turnkey desalination facility to ensure reliable, high-quality water availability. To learn more about our desalination services, contact us today !