Exploring how Danfoss high-pressure pumps and energy recovery devices are redefining energy efficiency, reliability, and compact design in seawater desalination systems.
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Freshwater scarcity is no longer a distant concern - it is a current and pressing global issue. According to the United Nations World Water Development Report 2025, approximately half of the global population experiences periods of severe water scarcity whilst a quarter of the population, across 25 countries, faces extreme water stress every year. While agriculture continues to dominate water withdrawals, accounting for roughly 72%, the industrial and domestic sectors represent approximately 15% and 13% respectively - a trend driven by industrial development and expanding urban infrastructure.
As seawater reverse osmosis (SWRO) continues to dominate modern desalination, global leaders like Danfoss are driving breakthroughs in energy efficiency through advanced high-pressure pump and energy recovery device technologies. Through Desal Supplies, these Danfoss high- pressure pumps and ERDs are readily available as essential elements of modern energy-efficient SWRO plants.
Amongst available desalination technologies, SWRO remains the most popular - purifying seawater by forcing it through semi-permeable membranes at high pressure.
While SWRO is favoured over thermal or multi-stage flash distillation, due to its modularity and scalability, its energy requirements remain a key challenge - primarily due to the high pressures needed to overcome osmotic pressure. High-pressure pumps alone can account for up to 70% of an SWRO plant's total energy use, making energy efficient pumping technology absolutely critical to performance and operating costs. In addition to this, modern SWRO systems often feature ERDs, which reduce overall specific energy consumption (SEC, kWh/m of produced fresh water) by capturing hydraulic energy from the high-pressure reject stream and converting it back into useful mechanical or electrical energy.
Among the most advanced and widely adopted solutions in this space are the Danfoss APPs (axial piston pumps) and iSave ERDs, which together deliver leading efficiency, compactness, and durability. The APP design delivers smooth, continuous and pulsation-free flow, essential for maintaining stable pressures and protecting RO membranes from damage. Their positive displacement mechanism provides precise flow control, enabling efficient operation under the high-pressure conditions typical of SWRO. With hydraulic efficiencies exceeding 90%, oil-free operation, and corrosion resistant construction, Danfoss APPs significantly reduce SEC while supporting long-term reliability in harsh environments.
Complementing the APPs, the Danfoss iSave ERDs integrate an isobaric pressure exchanger, a positive-displacement booster pump, and motor into a single, space-saving unit. Available in both horizontal and vertical orientations, this compact solution is ideal for installations where footprint is limited, simplifying system architecture by reducing the need for extra piping, instrumentation, and components. By recovering energy from the high-pressure reject stream and transferring it directly to the incoming seawater, the iSave can reduce SEC by up to 60%-achieving net recovery efficiencies of up to 94%.
Real-World Success: Danfoss's APP and iSave Technologies in Action
Recent installations demonstrate how Danfoss's advanced pump and ERD technologies are improving energy efficiency and system performance across a wide range of SWRO applications. There have been several impactful projects demonstrating significant advances in efficiency, capacity, and operational reliability.
Salt Separation Services, a UK-based manufacturer of SWRO plants, selected Danfoss high-pressure pump and energy-recovery technology to retrofit the desalination system of a luxury cruise ship. The project faced significant constraints: the existing SWRO plant was ageing, energy-intensive, and limited to approximately 400m3/day of freshwater production, while the replacement system had to fit entirely within the original engine-
room and be installed during a tight dry-dock window.
To meet these requirements, Salt Separation developed a compact, modular SWRO system based on a Danfoss APP 30 high-pressure pump and an iSave 40 energy-recovery device, both supplied by Desal Supplies as an authorised Danfoss distributor. The iSave’s isobaric pressure exchanger with integrated booster pump enabled effective recovery of brine pressure energy, significantly reducing SEC, while the compact layout allowed modular installation within the ship’s limited engine-room space.
The retrofit increased freshwater production from approximately 400 to 700 m3/day, while reducing energy use and operating costs, demonstrating how Danfoss pump and energy recovery technologies can deliver substantial performance gains in constrained marine applications. Close collaboration with Desal Supplies ensured precise calculation of flow and pressure requirements, allowing the Danfoss APP and iSave units to be perfectly matched.
As a proud partner of Danfoss, we are committed to delivering these innovations across the UK and Ireland - enabling sustainable, cost-effective desalination for a water scarce future.
While this article highlights Danfoss APP pumps and iSave ERDs, they exemplify the standard for energy-efficient desalination. Leading plant designers worldwide choose Danfoss for its reliability, compact footprint, and superior hydraulic performance. Advances across the industry, from next-generation RO membranes to improved pre-treatment methods, are pushing desalination toward efficiency limits. As energy remains the biggest cost driver, Danfoss continues to minimise SWRO’s energy footprint with integrated, modular, high-efficiency solutions.
Source: Desal Supplies