Engineered Membrane & Desalination Systems
Turnkey seawater reverse osmosis (SWRO) equipment, high-salinity brine concentration units, and ultrapure process water trains built for marine, municipal, and industrial infrastructure.
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Explore System SpecificationsEngineering Foundations of Industrial SWRO Desalination
An in-depth thermodynamic and hydraulic perspective on transforming high-salinity seawater into certified potable and municipal drinking water.
Transforming seawater into safe drinking water at municipal and industrial wholesale volumes demands precise thermodynamic control, advanced fluid dynamics, and cutting-edge membrane materials science. Modern Seawater Reverse Osmosis (SWRO) operates by applying hydraulic pressure greater than the natural osmotic pressure of seawater—typically varying from 28 bar (for brackish ocean water at 20,000 ppm TDS) up to 65–82 bar (for Arabian Gulf or Red Sea feedstocks running between 38,000 and 45,000 ppm TDS). The process forces water molecules across semi-permeable polyamide thin-film composite (TFC) membranes, achieving dissolved solids rejection rates consistently exceeding 99.7% to 99.85%.
Membrane Chemistry & Thermodynamic Recovery Architecture
At wholesale scale, standard multi-element pressure vessels house 8-inch spiral-wound membrane elements fabricated with dense cross-linked aromatic polyamide active layers. These polymers block hydrated monovalent ions such as sodium ($Na^+$) and chloride ($Cl^-$), along with heavy metals, microplastics, pharmaceuticals, and endocrine disruptors. To overcome fouling without chemical degradation, Tongjie leverages high-rejection brackish and seawater elements manufactured by world-class producers (such as DuPont FilmTec, Hydranautics, and Toray) alongside proprietary Chinese high-flux membranes.
Energy consumption historically constituted the largest hurdle in seawater conversion. Through isobaric energy recovery devices (ERDs), such as rotary pressure exchangers (PX), our plants transfer hydraulic energy directly from the high-pressure concentrate (brine) reject stream to the incoming low-pressure feed stream with thermodynamic efficiencies up to 96.5%–98%. This cuts specific energy consumption (SEC) down to 2.8 – 3.5 kWh/m³, transforming SWRO into an economically viable primary water source across hyper-arid archipelagos and coastal desert regions.
Intake & Pre-Filtration
Deep well or open sea intake passing through coagulant dosing, DAF, and automated multimedia/UF backwash barriers (SDI15 < 2.5).
Chemical Conditioning
Inline scale inhibitor, sodium bisulfite (dechlorination), and acid injection to prevent gypsum, silica, and biofouling precipitation.
High-Pressure SWRO
Super duplex 2507 booster pumps driving flow across TFC membranes coupled with isobaric pressure recovery devices (ERD).
Remineralization
Calcite (calcium carbonate) & dolomite dissolution beds combined with CO₂ dosing to balance hardness, alkalinity, and LSI.
Disinfection & Delivery
Multi-barrier UV irradiation and chlorine dioxide/sodium hypochlorite residual dosing for biological stability in distribution networks.
China Factory Supply Chain & Engineering Dominance
How Shanghai Tongjie leverages vertical integration, premium metallurgical fabrication, and complete FAT protocols to deliver unmatched CAPEX/OPEX efficiency.
Vertical Integration & Metallurgy
Operating from our advanced fabrication plant in Jiading District, Shanghai, Tongjie maintains end-to-end control over structural skid fabrication, automated TIG/orbital welding, and CNC pipe spools. We utilize certified Super Duplex Stainless Steel (UNS S32750 / 2507) and Duplex 2205 for all high-pressure saline headers to prevent pitting resistance equivalent numbers (PREN > 42) from suffering crevice attack in warm ocean waters.
- Duplex 2507 / 2205
- ASME Sec X FRP Vessels
- Zero Pitting Corrosion
Modular Containerization (FAT Tested)
Our containerized seawater plants are integrated into heavy-duty, marine-grade corten steel ISO containers (20ft and 40ft High Cube) equipped with closed-cell polyurethane thermal insulation, anti-corrosion epoxy coatings, and commercial HVAC climate systems. Every unit undergo strict Factory Acceptance Testing (FAT) with pressurized hydraulic water runs in Shanghai prior to container vessel departure.
- 100% Pre-Wired & Plumbed
- Plug & Play Field Start
- ISO Intermodal Compliance
Cost Competitiveness & Global Agility
By sourcing raw components through the world's most concentrated industrial supply chain in the Yangtze River Delta, Tongjie delivers superior membrane water purification systems at 30% to 45% CAPEX savings compared to Western European or American manufacturers, without sacrificing component quality. We standardize on Danfoss APP pumps, Siemens S7-1500 PLCs, and Schneider electrics.
- Tier-1 Core Components
- Rapid Engineering Lead Times
- High Component Redundancy
Localized Compliance & Potable Water Standards
Exceeding international drinking water thresholds across biological, chemical, and organoleptic parameters.
Converting raw seawater into human-potable drinking water requires adherence to strict global benchmarks, most notably the World Health Organization (WHO) Guidelines for Drinking-water Quality (4th Edition), the US EPA National Primary Drinking Water Regulations, and regional directives such as the GCC Standardization Organization (GSO 149/2014) for Gulf nations. Desalinated permeate straight from SWRO membranes is aggressive, corrosive, and deficient in essential minerals, necessitating dedicated post-treatment mineralization.
Critical Parameters: Boron, Bromate, and Mineral Stabilization
In typical ocean water, boron exists at concentrations between 4.5 and 7.0 mg/L as uncharged boric acid ($B(OH)_3$), which easily passes through standard reverse osmosis membranes. The WHO drinking water threshold enforces a maximum boron limit of 0.5 mg/L (with some regions permitting 1.0 mg/L). Tongjie implements proprietary two-pass RO designs or second-pass polishing arrays with caustic ($NaOH$) dosing to elevate pH above 9.5, transforming uncharged boric acid into charged borate ions ($B(OH)_4^-$), boosting boron rejection above 96%.
Furthermore, post-treatment balances the Langelier Saturation Index (LSI) between 0.0 and +0.2 to prevent distribution pipe corrosion. By passing permeate through limestone calcite contactors accompanied by controlled carbon dioxide injection, we introduce 30–50 mg/L of $Ca^{2+}$ and balanced bicarbonate alkalinity, ensuring wholesome taste, dental protection, and distribution infrastructure longevity.
| Water Quality Metric | Raw Open Seawater | Raw Permeate (Post-SWRO) | Tongjie Remineralized Potable Water | WHO Potable Water Standard |
|---|---|---|---|---|
| Total Dissolved Solids (TDS) | 35,000 – 45,000 mg/L | 150 – 350 mg/L | 200 – 400 mg/L (Optimized Taste) | < 500 mg/L |
| Chloride ($Cl^-$) | 19,000 – 24,000 mg/L | 80 – 180 mg/L | 80 – 180 mg/L | ≤ 250 mg/L |
| Sodium ($Na^+$) | 10,500 – 13,000 mg/L | 50 – 120 mg/L | 50 – 120 mg/L | ≤ 200 mg/L |
| Boron ($B$) | 4.5 – 7.0 mg/L | 1.0 – 1.8 mg/L (Single Pass) | < 0.5 mg/L (2-Pass / pH Boost) | ≤ 0.5 – 1.0 mg/L |
| Hardness ($CaCO_3$) | 6,000 – 7,500 mg/L | < 5 mg/L | 60 – 120 mg/L (Mineralized) | > 50 – 100 mg/L (Recommended) |
| Turbidity | 1.0 – 50 NTU | < 0.1 NTU | < 0.1 NTU | ≤ 1.0 NTU |
| Langelier Saturation Index (LSI) | Highly Variable | -2.5 to -3.0 (Highly Corrosive) | 0.0 to +0.2 (Non-Corrosive) | Slightly Positive / Balanced |
Global Enterprise Procurement Demands
Tailored engineering frameworks satisfying international EPC contractors, mining conglomerates, island resorts, and municipal utilities.
EPC Infrastructure Contractors
Demanding strict engineering documentation, complete 3D BIM models, HAZOP documentation, P&ID verification, instrument tag schedules, and compliance with IEC/NEMA electrical standards.
- BIM Revit / CAD Models
- Full FAT / SAT Execution
Remote Resorts & Private Islands
Requires ultra-quiet acoustic insulation, vibration dampening pads, ultra-compact physical footprints, automated chemical dosing, and remineralization delivering premium bottled-quality taste.
- Acoustic Decibel Limits
- Bottled Mineral Profile
Mining & Offshore Exploration
Built for harsh marine and desert operational environments, featuring explosion-proof control gear (ATEX/IECEx), rugged C5-M marine paint, and fully unmanned autonomous operation.
- C5-M Heavy Anti-Corrosion
- Satellite Telemetry
Municipal Disaster Relief & Aid
Fast-track emergency deployment capabilities, fully self-contained containerized format with rapid hose attachments, capable of connecting directly to temporary diesel generators or solar grids.
- Rapid Hose Couplings
- Immediate Potable Output
Desalination Industry Trends & Technological Evolution
Leading the technological transition toward decarbonized desalination, digital-twin telemetry, and advanced brine valorization.
Renewable & Off-Grid Solar SWRO
The integration of solar photovoltaic (PV) arrays and battery energy storage systems (BESS) directly with variable-frequency driven high-pressure pumps eliminates fossil fuel reliance. Tongjie’s patented dynamic ramp-up software balances fluctuating solar wattage, protecting delicate membrane leaves from hydraulic shock waves.
- Zero Grid Power Dependency
- Soft-Ramp Variable Frequency
AI-Driven Predictive Maintenance
Incorporating edge-computing SCADA systems that track normalized permeate flux, differential pressure ($\Delta P$), and temperature-corrected conductivity in real-time. Cloud algorithms predict scale formation days before performance degradation occurs, triggering automated CIP (Clean-in-Place) flush cycles automatically.
- Autonomous Clean-in-Place
- Preventative Membrane Preservation
Brine Minimization & Resource Recovery
Advancing from conventional 40%–45% SWRO recovery to Minimal Liquid Discharge (MLD) through secondary high-pressure DTRO (Disc Tube Reverse Osmosis) and Osmosis-Assisted Reverse Osmosis (OARO). Concentrating waste brine up to 120,000–160,000 ppm TDS drastically limits environmental marine discharge impact.
- High-Pressure DTRO Up to 120 Bar
- Eco-Friendly Coastal Protection
Localized Application Scenarios & Engineering Blueprints
Demonstrated operating reliability across diverse climatic and geographic environments.
Middle East Energy Corridor
Location: Gulf Coast, Saudi Arabia & UAE
Feedwater Profile: 43,500 mg/L TDS, seawater temp reaching 38°C in summer.
Engineering Solution: Containerized dual-train SWRO producing 2,000 m³/day potable water for petrochemical camps, integrated with duplex stainless steel metallurgy, chillers, and automated 2-pass boron removal meeting SASO and WHO standards.
- TDS < 200 mg/L
- High Temperature Tolerant
Maldives Resort Islands
Location: South Ari Atoll, Republic of Maldives
Feedwater Profile: 35,000 mg/L open coral lagoon water, pristine but high biological organic loading.
Engineering Solution: 500 m³/day skid-mounted silent SWRO plant enclosed in custom acoustic housing (<68 dB(A) at 1 meter). Features UF membrane pretreatment and food-grade mineral contactors delivering ultra-crisp, premium drinking water.
- Whisper-Quiet Operation
- Luxury Beverage Quality
Southeast Asian Municipalities
Location: Coastal Archipelago, Indonesia & Philippines
Feedwater Profile: High turbidity coastal waters prone to monsoon silt run-offs (turbidity > 25 NTU).
Engineering Solution: Skid systems utilizing flocculation, lamella sedimentation, and pressurized glass-media pre-filters ahead of high-flux SWRO membranes, providing consistent drinking water for 15,000 municipal residents.
- Heavy Silt Resistance
- Low-Cost Public Utility
Frequently Asked Questions (FAQ) for Wholesale Buyers
In-depth technical and commercial answers addressing procurement, water chemistry, maintenance, and international shipping protocols.
What specific raw water data is required to design an accurate wholesale SWRO proposal?
To size the pressure vessels, select membrane models, and configure pre-treatment stages correctly, our engineering team requires: Total Dissolved Solids (TDS), chloride, sulfate, calcium, magnesium, barium, strontium, silica, bicarbonate, and boron concentrations. In addition, please provide the feed water temperature range, Silt Density Index (SDI15) or turbidity, target daily product output (m³/day), and available power supply (voltage/frequency).
How does Tongjie prevent biofouling and scaling in tropical ocean waters?
We apply a multi-barrier defense strategy. Upstream raw seawater undergoes automated disk or multimedia filtration down to 5 microns, followed by precision chemical dosing of certified phosphonate antiscalants to prevent calcium carbonate and sulfate scaling. Periodic dosing of non-oxidizing biocides controls organic biofouling without damaging polyamide membranes, supported by automated low-pressure permeate flushes during shutdown.
What is the standard life expectancy of the SWRO membranes and high-pressure components?
With proper automated pretreatment maintaining SDI15 < 3.0 and routine Clean-in-Place (CIP) cleaning every 3–6 months, modern SWRO membranes achieve an operational service life of 3 to 5 years. High-pressure pumps manufactured in Super Duplex 2507 and ASME Class X fiberglass pressure vessels carry design lifespans exceeding 15 to 20 years.
How does isobaric energy recovery achieve sub-3.0 kWh/m³ power consumption?
Seawater RO systems discharge approximately 55%–60% of their intake volume as high-pressure brine (at 60–70 bar). Isobaric pressure exchangers (such as ERI PX or Danfoss iSave devices) route this reject brine into rotating ceramic ducts where it directly transfers hydraulic energy to a stream of equal volume incoming seawater. The main high-pressure pump only needs to pressurize the remaining 40%–45% permeate portion, slashing net power draw by up to 60%.
What post-treatment is essential before desalinated seawater is safe to drink?
Pure SWRO permeate is devoid of essential dietary minerals and exhibits an aggressive negative LSI, meaning it will dissolve iron and copper pipes and cause gastrointestinal distress. Potable conversion demands: (1) remineralization through calcite/dolomite beds to add calcium and magnesium, (2) pH adjustment using CO₂ or sodium carbonate to reach an LSI between 0.0 and +0.2, and (3) residual disinfection (sodium hypochlorite or chlorine dioxide) to maintain biological safety throughout storage tanks and pipelines.
Can Tongjie containerized plants operate entirely off-grid in remote islands?
Yes. We engineer self-sustaining off-grid desalination stations coupled directly to solar PV arrays, wind turbines, or localized diesel generators. Our control software includes dedicated variable-frequency soft-starts that eliminate large inrush currents, enabling smooth startup even on limited generator capacities or battery storage inverters.
What certifications and quality documentation accompany export shipments?
Tongjie holds ISO 9001, ISO 14001, ISO 45001, and CE certifications. Export equipment includes full material test reports (EN 10204 3.1 for duplex piping), hydrostatic pressure test logs, non-destructive welding test (NDT) results, electrical wiring schematics, calibration records for instrumentation, and comprehensive operations & maintenance (O&M) manuals in English.
What is the typical fabrication, delivery, and commissioning timeline?
Standard containerized systems (100 to 1,000 m³/day) require 6 to 10 weeks for complete manufacturing, assembly, and factory testing in Shanghai. Transit via ocean freight to Middle Eastern, European, or Southeast Asian ports typically takes 15 to 30 days. Because units arrive 100% pre-wired and plumbed, field commissioning requires only 7 to 15 days under our remote or on-site engineering supervision.
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Explore System SpecificationsRequest an Engineered Desalination System Proposal
Send your feed water analysis, capacity demands, and site operational conditions. Our senior chemical process engineers will formulate a comprehensive mass balance, P&ID drawing, and commercial proposal within 24 hours.