On 1 October 2026, Pump Industry Magazine reported that the $2.8 billion Alkimos Seawater Desalination Plant north of Perth has entered its fit-out phase — electrical and mechanical works now underway across the 29-hectare site. The Seawater Intake Pump Station (SWIPS) structural steel is 100% complete. The RO building switch room fit-out has commenced. The plant is on track for full operation in 2028.
Alkimos is the largest active water infrastructure project in Australia — Perth’s third desalination plant, capable of producing 50 billion litres of drinking water per year in Stage 1, with expansion to 100 billion litres possible in Stage 2. And like all seawater reverse osmosis (SWRO) plants, the pump systems are not an afterthought — they are the heart of the entire process. The electricity consumed by Alkimos’s pumps will account for approximately 65–70% of total plant operating energy, every single day it runs.
If you are involved in a desalination or water treatment infrastructure project in Australia — as an engineer, contractor, procurement specialist, or plant operator — this guide gives you a complete overview of the pump types required at each stage of a SWRO plant, how to select the right pump for each duty, and the material and sealing decisions that determine whether a seawater pump lasts 15 years or fails in 18 months.
Pump Power Australia’s engineering team provides pump selection and specification support for desalination plant pre-treatment, chemical dosing, product water transfer, and auxiliary services. Whether you are specifying for a new plant build or replacing pumps in an operating facility — contact our team on +61 3 9933 7400 or enquire online. We have over 35 years of experience supplying pumps to Australian water infrastructure projects.
A seawater reverse osmosis (SWRO) desalination plant requires five primary pump types: (1) Seawater intake pumps — drawing raw ocean water into the plant at low pressure; (2) Low-pressure pre-treatment booster pumps — pressurising water through filtration stages; (3) High-pressure RO feed pumps — the largest energy consumers, operating at 55–80 bar to force seawater through RO membranes; (4) ERD booster pumps — working alongside energy recovery devices to recover up to 94–97% of brine reject energy; (5) Chemical dosing pumps — for antiscalant, coagulant, chlorination, dechlorination, and pH adjustment throughout the process. All pump materials in direct seawater contact must be duplex or super duplex stainless steel — standard 316L stainless steel corrodes rapidly in seawater service.
1. Australia’s Desalination Plants — The 2026 Infrastructure Landscape
Australia has more operating seawater desalination plants per capita than almost any other developed nation — a direct response to the long-term drying trend affecting the country’s coastal catchments, the end of the millennium drought, and the structural water security challenge facing Australia’s major coastal cities. The six plants currently operating (or under construction) represent more than AUD $10 billion in infrastructure investment.
| Plant | Location | Capacity (GL/yr) | Status (2026) | Key pump challenge |
|---|---|---|---|---|
| Alkimos SWDP | Alkimos, WA (Perth north) | 50 GL (Stage 1); 100 GL ultimate | Fit-out phase — Oct 2026. Operational 2028 | SWIPS pump installation underway; RO building commissioning ahead. 400 MW renewable energy PPA |
| Southern Seawater DP | Kwinana, WA (Perth south) | 45 GL | Operational since 2006 | Ongoing pump MRO — impellers, mechanical seals, bearing replacements after 20 years of seawater service |
| Perth SWDP (Binningup) | Binningup, WA | 50 GL | Operational since 2011 | Second Perth plant — 15 years of SWRO operation. Refurbishment procurement now active for first-generation high-pressure pump internals |
| Sydney DP (Kurnell) | Kurnell, NSW | 90 GL (expandable) | Operational since 2010 | Cyclic operation (standby when rainfall adequate) creates unique seawater pump preservation and recommissioning requirements |
| Adelaide DP (Port Stanvac) | Port Stanvac, SA | 100 GL | Operational since 2012 | SA electricity at 42c/kWh makes pump efficiency critical — energy cost is even more dominant in the LCC calculation than other states |
| Victorian DP (Wonthaggi) | Wonthaggi, VIC | 150 GL | Operational since 2012 | Australia’s largest desal plant by capacity. Extended standby periods during wet years require careful pump preservation protocols |
Current status (October 2026): Seawater Intake Pump Station (SWIPS) structural steel and precast 100% complete. RO building switch room fit-out commenced. 2.5km intake tunnel extends 1.6km offshore — seawater will flow into the plant for treatment. Electrical and mechanical works now underway across the 29-hectare site. Acciona Agua and Jacobs Solutions (ASWA Alliance) delivering under 10-year O&M contract with 5-year extension option. Perth location page for full WA water infrastructure context.
2. How Seawater Reverse Osmosis Works — The Process a Pump Engineer Needs to Understand
Seawater reverse osmosis (SWRO) forces saltwater through semi-permeable membranes under enormous pressure — greater than the natural osmotic pressure of seawater (~27 bar) — to produce fresh water on the low-pressure side. The physics is straightforward; the pump engineering required to do it reliably, efficiently, and without corrosion failure is considerably more complex.
3. Stage 1 — Seawater Intake Pumps
The seawater intake pump is the first pump in the desalination process chain and — in terms of raw flow — one of the largest. Its function is to draw raw ocean water from the subsea intake structure through the intake pipeline into the plant headworks at low pressure and controlled velocity.
Alkimos SWIPS — What the Pump Station Looks Like
At Alkimos, the Seawater Intake Pump Station (SWIPS) is a purpose-built structure housing large mixed-flow vertical turbine pumps. The intake pipeline extends 2.5km from the plant headworks, with the ocean intake structure 1.6km offshore — in a “peanut”-shaped chamber buried in the seabed. The SWIPS structural steel was 100% complete as of October 2026, with patching and grouting ongoing ahead of pump installation. The pump installation is the next critical construction milestone before RO building commissioning.
Intake Pump Design Considerations
Intake flow must equal 2–2.5× the plant product water output, because SWRO recovery is typically 40–50% — only 40–50% of the seawater drawn in becomes fresh water. Alkimos Stage 1 at 50 GL/year requires raw seawater intake of approximately 110–125 GL/year.
Intake pipeline velocity must be low enough to prevent marine organism entrainment impact — typically below 0.15 m/s at the ocean inlet screen. This requires very large diameter intake pipelines and explains the “slow and steady” ocean intake design described in Alkimos project documentation.
Seawater intake screens and pipelines are subject to biofouling — barnacles, mussels, and biofilm. Intake pump impellers must be resistant to abrasion from any biological material or particulates that pass through screens. Duplex SS impellers are standard; stainless steel wear rings are replaceable.
Intake pump stations are always designed with N+1 redundancy — one duty pump and at least one standby. Loss of the intake pump station means loss of the entire plant. The standby pump must be capable of immediate automatic start on duty pump trip.
4. Stage 2 — Pre-Treatment Booster Pumps
Between the intake pump station and the high-pressure RO feed pump, raw seawater passes through pre-treatment — typically media filtration (dual-layer sand and anthracite, or dissolved air flotation in high-turbidity conditions), followed by cartridge filtration. A low-pressure booster pump is required to push the seawater through these filtration stages while maintaining adequate positive pressure at the suction of the high-pressure pump to prevent cavitation.
Pre-treatment booster pump specification is often underspecified in Australian desal plant designs — resulting in inadequate suction pressure at the HP pump during filter cartridge loading, causing HP pump cavitation and premature damage. The pre-treatment booster pump must be sized for worst-case conditions — fully loaded cartridge filters at maximum flow — not clean cartridge conditions. For cavitation diagnosis and prevention guidance, see our pump cavitation guide.
Pre-treatment booster pumps for SWRO service are typically horizontal end-suction or between-bearings centrifugal pumps in duplex stainless steel construction, operating at 3–10 bar discharge pressure. VFD control is standard to accommodate variable filter pressure drop.
5. Stage 3 — The High-Pressure RO Feed Pump
The high-pressure RO feed pump is the most technically demanding pump in the desalination process and the single largest energy consumer in the plant. It receives pre-treated seawater at 3–8 bar from the pre-treatment system and must raise it to 55–80 bar — sufficient to overcome seawater’s osmotic pressure (~27 bar) with enough additional pressure to force water through the membranes at the required recovery rate.
High-Pressure RO Pump Types — Which to Choose
| Pump type | Pressure range | Scale | Key advantage | Material standard |
|---|---|---|---|---|
| Multistage centrifugal (ring section or axially split) | 40–120 bar | Large — municipal desal plants (Alkimos, Sydney, Melbourne) | High flow at high pressure, proven large-scale SWRO track record, VFD-compatible, centrifugal flow profile suits RO membrane requirements | Super duplex 2507 (UNS S32750) for internals; casing in 2205 or cast duplex |
| Axial piston (high-pressure plunger) | 55–100 bar | Small to medium — containerised, offshore, remote systems | Very high efficiency (>90%), compact, handles variable speed well, integrated ERD option available | Super duplex or titanium for wetted components |
| Triplex/quintuplex plunger | 60–100+ bar | Small systems, high-pressure brine injection, industrial SWRO | Handles very high pressure, precise flow control, suitable for batch SWRO applications | 316L acceptable for small systems; duplex preferred for seawater |
High-Pressure RO Pump Key Specification Parameters
The most common specification error for SWRO high-pressure pumps in Australian projects is specifying 316L stainless steel for pump internals or casings in contact with seawater, based on the assumption that “316 handles salt water.” It does not — not at 35,000 ppm chloride, 55–80 bar, and 7,000+ hours/year of continuous service. Chloride-induced pitting and crevice corrosion in 316L at SWRO operating conditions is well-documented and typically begins within 2–3 years of operation. Minimum specification for SWRO HP pump wetted components: duplex 2205 for casings, super duplex 2507 (SAF 2507) for impellers and diffusers at pressures above 60 bar. See Section 8 for the full corrosion comparison.
6. Stage 4 — The ERD Booster Pump and Energy Recovery
The energy recovery device (ERD) and its companion booster pump are the engineering innovation that transformed SWRO from a high-cost technology into the dominant global water production method. Understanding how they work explains why the ERD booster pump selection is so important — and why getting it wrong is expensive.
How Isobaric Energy Recovery Works — The Pump Engineering
In a SWRO plant without energy recovery, the high-pressure brine reject stream (which exits the RO membranes at 50–75 bar — only slightly below the HP feed pressure) was historically throttled down to near-atmospheric pressure and discharged. This wasted enormous amounts of energy — every cubic metre of rejected brine had kinetic and pressure energy that was simply lost as heat in a pressure-reducing valve.
The isobaric pressure exchanger uses pistons or rotary chambers to transfer pressure from the high-pressure brine to incoming raw seawater — with no moving parts in the pressure transfer zone, achieving 94–97% energy transfer efficiency. The ERD booster pump is a small, high-efficiency centrifugal or axial piston pump that provides the 3–8 bar “top-up” pressure to the ERD outlet stream, compensating for hydraulic losses across the pressure exchanger and delivering the correct pressure to the RO membrane inlets.
The ERD booster pump specification is critical: it operates in a partially-desalinated seawater stream at 50–70 bar discharge pressure, and it is VFD-controlled for pressure modulation as membrane fouling state changes throughout the cleaning cycle. Material: super duplex 2507 mandatory. Sealing: double mechanical seal with external clean flush (Plan 32) to keep abrasives from the brine stream away from the seal faces. For multistage centrifugal ERD booster pumps, correct bearing loading and shaft deflection calculations are essential — the combination of high pressure and variable speed creates fatigue loading that must be engineered for.
7. Stage 5 — Chemical Dosing Pumps in Desalination Plants
A SWRO desalination plant requires chemical addition at multiple points in the process — each with its own dosing pump specification. Chemical dosing pumps in desal plants must deliver precise, metered, continuous addition with redundancy — because each dosing failure has a direct consequence for membrane life, product water quality, or regulatory compliance.
| Chemical | Dosing location | Purpose | Dosing pump type | Key material requirement |
|---|---|---|---|---|
| Coagulant Ferric sulfate or FeCl₃ |
Pre-treatment — ahead of media filtration | Destabilises colloidal particles and organic matter for removal in media filters. Reduces SDI (Silt Density Index) feeding HP pump | Peristaltic or diaphragm dosing | PVDF wetted components — ferric salts are highly corrosive to metals |
| Antiscalant Scale inhibitor polymer |
Ahead of HP pump — RO feed stream | Prevents CaCO₃, CaSO₄, BaSO₄, and silica scale from depositing on RO membrane surfaces as concentrate factor increases. Without antiscalant, membranes scale within days | PC pump or precision diaphragm dosing | 316 SS or PVDF — antiscalant is mildly corrosive but not aggressive |
| Sodium hypochlorite NaOCl (chlorine) |
Seawater intake — biofouling control. Removed by dechlorination before RO | Prevents biofouling of intake structure and pre-treatment systems. Polyamide RO membranes are irreversibly damaged by chlorine — must be 100% removed before membrane feed | Magnetic drive or peristaltic — never metallic wetted parts | PVDF or PVC wetted components mandatory — NaOCl destroys SS and most metals |
| Sodium bisulfite SBS (dechlorination) |
Ahead of cartridge filters / HP pump | Neutralises residual chlorine before RO membranes. ORP monitoring on RO feed confirms complete dechlorination — a critical control parameter | Diaphragm metering dosing pump — precise stoichiometry essential | 316 SS or PVDF — bisulfite is mildly reducing but not severely corrosive |
| Lime / caustic / CO₂ | Post-RO — product water remineralisation | RO permeate is very low TDS and slightly acidic — remineralisation raises pH, adds calcium and carbonate alkalinity for distribution system corrosion control and drinking water standards | PC pump for lime slurry; diaphragm for caustic | Lime: rubber-lined or food-grade construction — abrasive slurry. Caustic: 316 SS, EPDM seals |
8. Seawater Corrosion — Why Standard 316L Stainless Steel Fails in SWRO Service
The corrosion of metallic components in seawater is one of the most consequential engineering challenges in desalination plant design. Every pump, valve, and fitting in direct contact with seawater must be specified in a material that can withstand 35,000+ ppm chloride, biological fouling, dissolved oxygen, and — in the high-pressure stages — erosion from high-velocity flow.
The Pitting Resistance Equivalent Number (PREN) is the primary material selection parameter for seawater corrosion resistance. PREN = %Cr + 3.3 × %Mo + 16 × %N. Higher PREN = greater resistance to pitting corrosion in chloride environments. The minimum PREN for reliable seawater service is generally accepted as 32–35.
| Material | PREN | Seawater pitting resistance | Typical SWRO application | Verdict |
|---|---|---|---|---|
| 304 SS (1.4301) | ~18 | Very poor — pitting within weeks in seawater | Post-RO product water only (low chloride) | Never specify for seawater |
| 316L SS (1.4404) | ~24 | Inadequate — pitting and crevice corrosion within 2–5 years in continuous seawater at SWRO conditions | Short-term or low-velocity seawater contact only; post-RO product water | Not acceptable for SWRO HP service |
| Duplex 2205 (1.4462) | ~35 | Good — acceptable for seawater below ~40°C at pressures up to approximately 60 bar. Standard for intake pumps, pre-treatment pumps, pump casings | Intake pump impellers, pre-treatment booster pump, HP pump casings at <60 bar | ✓ Standard for most SWRO seawater service |
| Super duplex 2507 (SAF 2507) | >41 | Excellent — specified for HP pump internals (impellers, diffusers), ERD booster pumps, and brine disposal service where high velocity and high chloride coincide | HP RO feed pump impellers/diffusers at >60 bar, ERD booster internals, brine outfall pumps | ✓ Required for high-pressure SWRO internals |
| Titanium (Grade 2) | N/A (passive oxide) | Outstanding — immune to chloride pitting and crevice corrosion at all seawater service conditions. Titanium forms a stable TiO₂ passive film that does not fail in chloride environments | Critical high-velocity zones, brine injection, and any surface where erosion-corrosion is most severe | ✓ Best seawater resistance — higher cost |
9. Brine Disposal Pumps — The Often-Overlooked Challenge
Every SWRO plant produces a concentrated brine reject stream — seawater from which 40–50% of the water has been removed, leaving behind a stream at approximately 60,000–70,000 ppm TDS (roughly twice the salinity of normal seawater). This brine must be discharged to the ocean through a carefully designed outfall system.
Brine disposal pumps face a particularly challenging combination of conditions: very high chloride concentration (making material selection even more critical than for the intake), suspended solids from pre-treatment residuals, and biocide residues from chlorination. At Alkimos, the outfall tunnel extends approximately 1.6 km offshore to return brine at sufficient depth and velocity for dilution — the outfall pump system must maintain this pressure and flow continuously.
Brine Disposal Pump Requirements
- Material: super duplex 2507 or titanium — brine at 60,000–70,000 ppm chloride is more aggressive than feed seawater. Standard duplex 2205 may exhibit accelerated crevice corrosion at brine concentrations, particularly in dead zones and under gaskets
- Solids handling: brine may carry fine filter backwash solids, antiscalant crystals, or pre-treatment chemical residuals — pump impeller design must accommodate these without blockage
- Flow metering: brine discharge is an environmental licence condition at all Australian desal plants — accurate flow metering of the outfall is a regulatory requirement, not optional
- Sealing: double mechanical seal with external clean water flush (API Plan 32) — brine at high concentration is not a suitable flush medium for seal faces in the outfall pump
10. SWRO Pump Selection Checklist — For Every Stage
Use this checklist for every pump specification in a SWRO desalination plant. Each item prevents a common and costly specification error.
Brine is not the same as seawater — it has roughly 2× the TDS and is significantly more corrosive. Permeate is nearly fresh water. Material specification must reflect the fluid at each specific point, not a generic “seawater service” label.
Duplex 2205 (PREN ~35) minimum for seawater. Super duplex 2507 (PREN >41) for high-pressure stages above 60 bar and brine service. Reject any specification that proposes 316L SS for seawater-contact pump components — it will corrode in service.
Fixed-speed HP pumps on SWRO plants waste significant energy during low-demand periods and cannot accommodate membrane fouling pressure variation. VFD is standard on all modern SWRO HP pump installations — confirm VFD is in the specification, not an optional add.
Not for clean filter conditions — for end-of-life loaded filters. The HP pump needs adequate NPSH at worst-case pre-treatment pressure drop, not at start-of-life conditions. Under-specifying the booster causes HP pump cavitation damage within the first year.
A single mechanical seal in SWRO HP service is inadequate — process pressures above 55 bar, combined with abrasive particles, create rapid seal face wear. Double seal with external clean water flush (Plan 32) is the standard for all SWRO HP and ERD booster pumps.
Loss of the intake pump, HP feed pump, or ERD booster shuts down the entire plant. All three must have duty-standby redundancy with automatic failover. The standby pump must be hot-standby (powered up, ready to start) not cold-standby (switched off).
Key Takeaways — Desalination Plant Pump Selection
- A SWRO plant requires five pump types: intake, pre-treatment booster, high-pressure RO feed, ERD booster, and chemical dosing — each with different pressure, flow, material, and sealing requirements
- The high-pressure RO feed pump is the plant’s largest energy consumer, operating at 55–80 bar against seawater osmotic pressure — super duplex 2507 or titanium for all wetted internals
- Never specify 316L stainless steel for SWRO seawater-contact pump components — pitting and crevice corrosion will occur within 2–5 years. Minimum PREN ≥35 (duplex 2205) for seawater; PREN ≥41 (super duplex 2507) for high-pressure stages
- ERD booster pumps recover 94–97% of brine reject stream pressure energy — modern SWRO plants consume 2.0–3.5 kWh/m³ vs 7–10 kWh/m³ without ERD. Alkimos is powered by 400 MW renewable wind
- Chemical dosing pumps require chemical-specific wetted materials — NaOCl destroys stainless steel; use PVDF or PVC for chlorine dosing. Progressive cavity pumps suit lime slurry and antiscalant
- Brine disposal pumps face 60,000–70,000 ppm chloride — more aggressive than seawater. Specify super duplex 2507 or titanium for brine outfall service
- Alkimos SWDP entered fit-out phase October 2026 — the largest active water infrastructure project in Australia. Operational target: mid-2028. Perth already obtains ~50% of drinking water from desalination
- Pump Power Australia supplies multistage centrifugal pumps, magnetic drive pumps, dosing pumps, and PC pumps for desalination auxiliary and pre-treatment services — contact our team for specification support
11. Reddit, Quora, and Engineering Forum Questions — Answered
A single-stage centrifugal pump cannot produce 55–80 bar from a seawater inlet pressure of 3–8 bar without either impractically large impeller diameters (causing structural and bearing issues) or extremely high rotational speeds (beyond standard motor capabilities). Multistage pumps add head incrementally across 3–8 stages, each operating at manageable pressure differentials. Each stage contributes 10–20 bar. The cumulative head of 6–8 stages reaches 55–80 bar with manageable impeller geometry, acceptable operating speeds, and standard motor sizes. Ring-section multistage centrifugal pumps (where stages are bolted together in series) are the standard design for large SWRO plants worldwide, including Alkimos.
Scale determines pump type. For small SWRO systems below approximately 250,000 litres/day — residential, commercial, offshore, naval vessel — axial piston pumps (Danfoss APP series) or triplex plunger pumps achieve very high efficiency (>90%) at the smaller flow rates where centrifugal pumps become inefficient. For large municipal SWRO plants (Alkimos, Sydney, Melbourne, Adelaide) producing millions of litres per day, multistage centrifugal pumps are preferred — they achieve high efficiency at large flow rates, have simple maintenance, and can run at constant speed with VFD control. Plunger pumps in large-scale service produce objectionable pulsation that requires attenuation hardware.
The Sydney Desalination Plant at Kurnell operates on a trigger-based model — it activates when Sydney’s dam levels fall below a trigger threshold and suspends when dams recover to the upper threshold. This cyclic operation creates unique pump preservation challenges. During extended standby: seawater remains in contact with pump internals, creating concentrated chloride environments where crevice corrosion can progress. When recommissioning: HP pumps must be slowly brought back to operating pressure to avoid pressure shock damage to membranes and pump seals. Extended standby on Sydney’s HP pumps requires a specific preservation protocol — fresh water flushing, nitrogen blanketing, and periodic rotation of shafts. This is different from Perth’s desalination plants which operate more continuously due to Perth’s persistent water supply deficit.
Chlorine (sodium hypochlorite) is dosed into the seawater before pre-treatment to control biofouling. However, polyamide thin-film composite RO membranes are irreversibly damaged by chlorine — even at very low concentrations (parts per billion), chlorine oxidises the polyamide and degrades salt rejection permanently. For this reason, all desalination plants using polyamide membranes must completely remove chlorine before the RO membranes using sodium bisulfite (SBS) dechlorination, typically with ORP (Oxidation-Reduction Potential) monitoring on the RO feed to confirm zero residual chlorine. The chlorine used at the intake and in pre-treatment stages is dosed and removed before the HP pump. Post-RO, chlorine is re-added to the product water for disinfection in the distribution system — this is the chlorine you may taste in tap water.
Perth’s catchment rainfall has declined approximately 20% since the 1970s due to long-term climate change, making surface water storage increasingly unreliable. Perth sits in a Mediterranean climate zone that has experienced structural — not temporary — rainfall decline. The Gnangara groundwater system that historically supplemented Perth’s water supply has been declining for decades. By contrast, Sydney, Melbourne, and Brisbane have had sufficient rainfall in most years to meet demand from dam storage, making desalination a strategic reserve rather than a primary supply. Perth has essentially moved past the point where dam storage alone can secure the city’s water future — desalination is now structural, not emergency supply. The Alkimos plant is Perth’s third full-scale desal plant, not the first.
Frequently Asked Questions
Structured for Google People Also Ask, ChatGPT, Gemini, Claude, and Perplexity direct answer extraction.
A seawater reverse osmosis (SWRO) desalination plant requires five main pump types: (1) Seawater intake pumps — draw raw ocean water through the subsea intake tunnel at low pressure; (2) Low-pressure pre-treatment booster pumps — pressurise water through media and cartridge filtration; (3) High-pressure RO feed pumps — the primary energy consumer, operating at 55–80 bar to force seawater through RO membranes; (4) ERD booster pumps — recover up to 94–97% of energy from the high-pressure brine reject stream via isobaric pressure exchangers; (5) Chemical dosing pumps — antiscalant, coagulant, chlorination, dechlorination, and pH adjustment. Product water transfer pumps, backwash pumps, and CIP pumps are also required. All pumps in direct seawater contact must be duplex or super duplex stainless steel — not standard 316L SS.
The high-pressure feed pump in a seawater reverse osmosis (SWRO) plant must raise feed water pressure to 55–80 bar (5.5–8.0 MPa) at the RO membrane inlet. This is required to overcome seawater’s osmotic pressure (~27 bar) with sufficient driving pressure for the chosen recovery ratio. Australian coastal seawater (Perth’s Indian Ocean, Sydney’s Tasman Sea, Adelaide’s Spencer Gulf, Melbourne’s Bass Strait) has TDS of approximately 34,000–37,000 ppm — corresponding to operating pressures at the lower-middle of this range under normal conditions. Membrane fouling, higher recovery ratios, and lower water temperatures increase the required pressure over the operating cycle.
Standard 316L stainless steel corrodes in seawater desalination service because its Pitting Resistance Equivalent Number (PREN ~24) is insufficient to resist chloride-induced pitting at the chloride concentrations (35,000+ ppm), temperatures, and pressures of SWRO service. Three corrosion mechanisms attack 316L in seawater: pitting corrosion (initiated by chloride ions in surface defects), crevice corrosion (under gaskets and in threaded connections), and stress corrosion cracking (at elevated temperatures in chloride environments). Duplex stainless steel 2205 (PREN ~35) resists pitting in standard seawater SWRO conditions. Super duplex 2507 (PREN >41) is required for high-pressure internals above 60 bar and brine disposal service at elevated chloride concentrations.
An energy recovery device (ERD) captures the pressure energy in the high-pressure brine reject stream — which exits RO membranes at 50–75 bar — and transfers it directly to incoming raw seawater, reducing the pressure the high-pressure feed pump must generate. Modern isobaric pressure exchanger ERDs achieve 94–97% energy transfer efficiency. A complementary ERD booster pump compensates for minor hydraulic losses. Without ERDs, early SWRO plants consumed 7–10 kWh per cubic metre of product water — modern plants with ERDs consume 2.0–3.5 kWh/m³, a reduction of 60–70%. The Alkimos plant at Perth will use renewable wind energy under a 400 MW Power Purchase Agreement, making it one of the world’s most sustainable large-scale desalination plants. See our VSD energy savings guide for related pump efficiency principles.
SWRO (Seawater RO) and BWRO (Brackish Water RO) require very different pump specifications. SWRO processes ocean seawater at 30,000–45,000 ppm TDS — feed pump operating pressure 55–80 bar, all wetted materials must be duplex or super duplex SS or titanium. BWRO processes brackish groundwater or industrial water at 1,000–10,000 ppm TDS — feed pump operating pressure only 10–25 bar, standard 316L SS is acceptable for most service. Australian inland desalination for brackish groundwater (common in regional SA, NT, WA outback, and mine site water treatment) uses BWRO specifications. Australian coastal city desal plants all process seawater (SWRO specifications). For seawater pump material selection, see our chemical transfer pump guidance for related corrosion-resistant selection principles.
Modern SWRO desalination plants with isobaric energy recovery devices consume approximately 2.0–3.5 kWh per cubic metre of fresh water produced. The high-pressure feed pump accounts for 60–70% of total plant energy. Without ERDs, early SWRO plants consumed 7–10 kWh/m³. The Alkimos SWDP is designed to be powered by 400 MW of renewable wind energy procured under a Power Purchase Agreement — making it one of the lowest-carbon desal plants in the world. At Australia’s average commercial electricity rate of approximately 30c/kWh, producing 50 billion litres/year costs approximately AUD $30–$50 million annually in electricity for Stage 1 at Alkimos — underscoring why pump efficiency is critical and why renewable energy agreements are fundamental to desal project economics.
Five Australian cities have seawater desalination plants: Perth (3 plants — Kwinana since 2006, Binningup since 2011, Alkimos under construction for 2028); Sydney (Kurnell, since 2010); Adelaide (Port Stanvac, since 2012); Melbourne (Wonthaggi, since 2012 — Australia’s largest by capacity at 150 GL/year); and the Gold Coast (Tugun, since 2009). Perth has the greatest reliance — approximately 50% of Perth’s drinking water already comes from desalination, rising further when Alkimos operates. Sydney’s plant runs intermittently on a trigger-threshold basis. Melbourne’s plant is similar. Perth’s structural rainfall decline has made desalination a permanent primary supply, not an emergency reserve. For WA water infrastructure context, see our Perth location page.
A SWRO plant requires chemical dosing pumps for five main chemicals: coagulant (ferric sulfate/chloride) ahead of media filtration — PVDF wetted parts; antiscalant ahead of HP pump — 316 SS or PVDF; sodium hypochlorite (chlorine) at seawater intake — PVDF or PVC mandatory, never metal; sodium bisulfite (dechlorination) ahead of RO — 316 SS or PVDF; and post-RO remineralisation chemicals (lime slurry, caustic, CO₂). Lime slurry dosing uses progressive cavity pumps for abrasive handling. All dosing points require N+1 redundancy. Accurate metering (±1% or better) is a process requirement — not optional. Poor antiscalant dosing accuracy causes membrane scaling within days.
Seawater pump corrosion occurs through four mechanisms: pitting corrosion (chloride initiates localised attack on passive film), crevice corrosion (oxygen depletion under gaskets and in threaded zones), erosion-corrosion (high-velocity seawater removes passive film faster than reformation), and galvanic corrosion (dissimilar metals in seawater). Prevention: specify duplex SS 2205 (PREN ≥35) minimum for all seawater-contact components; super duplex 2507 (PREN >41) for high-pressure stages and brine service; titanium for the most demanding zones. Avoid mixed metals in seawater pump assemblies. Use PTFE or Viton elastomers — avoid NBR which is attacked by seawater biological compounds. Maintain protective coatings on external surfaces. Implement a pump preservation protocol during standby periods for cyclic-duty plants. See our pump maintenance checklist for preservation guidance.
Yes. Pump Power Australia supplies pump solutions for desalination plant pre-treatment, chemical dosing, product water transfer, and auxiliary services from our Brooklyn, Victoria warehouse — with fast freight to all Australian states. We supply multistage centrifugal pumps for high-pressure service, magnetic drive pumps for chemical dosing in corrosive seawater chemical service (NaOCl, HCl, ferric salts), progressive cavity pumps for polymer, antiscalant, and lime slurry dosing, and chemical dosing systems for all desal plant chemical addition points. For desalination project pump specification and selection enquiries — contact our engineering team on +61 3 9933 7400 or enquire online.
References
- Pump Industry Magazine — “Alkimos desalination plant moves to fit-out phase” (October 1, 2026): pumpindustry.com.au
- Water Corporation — Alkimos Seawater Desalination Plant project updates (September 2026): watercorporation.com.au
- Marine Business News — “Alkimos Desalination Plant marks marine milestone” (September 2026): marinebusinessnews.com.au
- Sulzer Pumps — “Pumps for Desalination Plants” technical guide: sulzer.com
- DataIntelo — “Seawater Reverse Osmosis Desalination Pump Market Research Report 2034” (2026): dataintelo.com
- Aqualitek — “What Are the Core High-Pressure Components in Seawater Desalination Systems?” (2026): aqualitek.com
- IDRA — “New booster pump for desalination plants based on reverse osmosis” (Sulzer ZF-RO, October 2024): idrawater.org
- ERI (Energy Recovery Inc.) — PX Pressure Exchanger technology: energyrecovery.com
- IChemE — “Alkimos Desalination Plant — Project Overview from Planning to Construction Stages” (May 2026): icheme.org
- Infrastructure Pipeline Australia — “Alkimos Seawater Desalination Plant” project entry: infrastructurepipeline.org
- International Desalination Association (IDA) — Global desalination technology standards: idadesal.org
Desalination or Water Treatment Project Pump Enquiry?
Whether you are specifying pumps for a new desal plant build, replacing pumps in an operating SWRO facility, or need chemical dosing pump support for a water treatment project — Pump Power Australia’s engineering team provides selection and specification support at no charge.
We supply multistage centrifugal, magnetic drive, progressive cavity, and chemical dosing pumps for Australian water infrastructure projects — fast dispatch from Brooklyn VIC to all states.
📞 +61 3 9933 7400
✉ info@pumppower.com.au
9 Export Drive, Brooklyn VIC 3012 | Mon–Fri 8:00am–5:00pm AEST
This guide was prepared by the engineering team at Pump Power Australia, a specialist industrial pump supplier based in Brooklyn, Victoria, with over 35 years of experience supplying pumps to Australian water treatment, mining, food processing, chemical, and marine industries.
Related guides: Pump Total Cost of Ownership | VSD Energy Savings | Pump Cavitation Guide | Pump Performance Curve | Mechanical Seal Guide | Perth & WA Location
