Overview
Reverse Osmosis (RO) equipment is a advanced water treatment system based on RO membrane technology. By applying pressure higher than the osmotic pressure of the solution, it efficiently separates dissolved salts, organic matter, microorganisms, and other impurities from water. The core RO membrane has a pore size smaller than 0.0001 μm, capable of retaining substances with molecular weights over 200 Daltons, achieving desalination rates of 95%-99.9%. Widely used in seawater desalination, industrial pure water production, advanced drinking water treatment, and zero-liquid discharge (ZLD) of wastewater, it is the preferred technology for high-purity water treatment, especially suitable for desalination of high-mineralization water sources (e.g., brackish water, industrial brine).
Working Principle
I.Pretreatment Stage
Raw water undergoes multi-stage pretreatment to meet RO membrane inlet requirements:
1.Coarse Filtration: Suspended solids, colloids, and residual chlorine (must be <0.1 mg/L to avoid membrane oxidation) are removed via quartz sand and activated carbon filters.
2.Fine Filtration: A 5-μm security filter intercepts tiny particles to prevent membrane fouling.
3.Water Quality Adjustment: Antiscalants (e.g., sodium hexametaphosphate) are dosed to inhibit calcium/magnesium scaling, and pH is adjusted to the membrane’s optimal range (typically pH 4-11).
II.RO Membrane Separation Stage
1.Pressure-Driven Membrane Separation:
Pretreated raw water is pushed into RO membrane modules by a high-pressure pump (1.0-1.6 MPa for brackish water, 5.5-7.0 MPa for seawater). Water molecules permeate the membrane to form product water (desalted water), while dissolved salts (e.g., NaCl, CaSO₄), heavy metals, and bacteria are retained and discharged as concentrate.
2.Membrane Element Arrangement:
A "single-pass multi-stage" design (e.g., one-pass two-stage) is commonly used, where permeate from the front-stage modules serves as feed for the rear stages, and concentrate is recycled to the front to increase recovery rates (typically 60%-85%) and reduce discharge.
III.System Operation and Maintenance
-Real-Time Monitoring: Online conductivity meters and pressure sensors monitor product water quality and pressure drop across the membrane. When the pressure difference exceeds 0.3 MPa or water production drops by 15%, a cleaning procedure is triggered.
-Chemical Cleaning: Circulating cleaning with citric acid (for inorganic scaling) or sodium hydroxide (for organic/biofilm removal) is performed as needed (typically 3-12 months interval based on water quality).
Performance Characteristics
I.Ultra-High Desalination Rate and Water Quality Assurance
-Desalination Rate ≥95%: For brackish water with TDS=3000 ppm, product water conductivity can be reduced to <50 μS/cm; for seawater (TDS≈35,000 ppm), it achieves <100 μS/cm, meeting drinking water (GB5749) and industrial pure water standards.
-Broad-Spectrum Retention: Effectively removes >99% of bacteria, viruses, pesticide residues, and dissolved organic matter (TOC removal rate >85%).
II.Energy Efficiency and Intelligence
-Optimized Energy Consumption: With energy recovery devices (e.g., PX pressure exchangers), seawater desalination energy consumption can be as low as 3-4 kWh/ton (vs. 5-8 kWh/ton for traditional processes), and industrial RO consumes about 1-2 kWh/ton.
-Fully Automated Control: Integrated PLC systems enable remote monitoring of water quality and automatic adjustment of concentrate valve openings for "unattended" operation.
III.Modularity and Longevity
-Flexible Configuration: Membrane modules (8-inch or 4-inch spiral wound) can be combined flexibly for water production ranging from 1 m³/h to 10,000 m³/h.
-Membrane Lifespan: Under normal conditions, RO membranes last 3-5 years, and up to 7-10 years with high-quality pretreatment.
IV.Wide Applicability
-Water Source Adaptability: Handles groundwater, surface water, seawater, and industrial wastewater, especially high-hardness (Ca²++Mg²+>500 mg/L) and high-sulfate (SO₄²->2000 mg/L) sources.
-Industry Coverage: Indispensable in semiconductors (electronic-grade ultra-pure water), power generation (boiler feed water), pharmaceuticals (water for injection), and food processing (concentration separation).
Structural Components
I.Membrane Modules
-RO Membrane Elements:
-Material: Aromatic polyamide composite membranes with negatively charged surfaces for enhanced anion retention.
-Types: Spiral wound membranes (most common, single element area 37-75 m²) and hollow fiber membranes (anti-fouling, for wastewater treatment).
-Pressure Vessels: Made of stainless steel or FRP,耐压 (pressure-resistant) 1.6-10.0 MPa, each housing can hold 1-7 membrane elements.
II.High-Pressure Pumps and Energy Recovery Systems
-High-Pressure Pumps: Multi-stage centrifugal or piston pumps providing power for membrane separation.
-Energy Recovery Devices: Turbine-type energy recoverers (PERC) reclaim concentrate pressure energy, reducing pump power consumption by 30%-50%.
III.Control System
-Instruments and Valves:
-Online Instruments: Conductivity meters, pH meters, flow meters, and pressure gauges.
-Valves: Electric control valves (for concentrate flow) and quick-flush valves (for rapid membrane surface flushing).
-Human-Machine Interface (HMI): Displays real-time water quality data, supports historical data query and fault alarms.
IV.Auxiliary Equipment
-Dosing Systems: Include antiscalant and reducing agent (sodium bisulfite) dosing units to prevent membrane fouling.
-Cleaning Systems: Equipped with cleaning tanks, pumps, and security filters for preparing and delivering cleaning solutions.
Application Cases
I.Seawater Desalination
-Saudi SWCC Seawater Desalination Project
The SWCC Jubail plant in Saudi Arabia deploys a 1,000,000 m³/day RO seawater desalination system using 8-inch anti-fouling RO membranes and energy recovery, achieving 3.2 kWh/ton energy consumption and product water TDS<200 ppm for municipal supply.
-Yongxing Island, Xisha Islands, China
A 5,000 m³/day RO seawater desalination station on Yongxing Island uses a one-pass two-stage membrane arrangement with 65% recovery, solving drinking water challenges for island residents and meeting national drinking water standards.
II.Industrial Pure Water Production
-Semiconductor Wafer Cleaning
TSMC’s Nanjing factory uses RO+EDI to produce ultra-pure water with 99.8% desalination rate and conductivity <0.1 μS/cm, meeting the stringent water quality requirements for 12-inch wafer cleaning (particle >0.02 μm content <1 piece/mL).
-Thermal Power Plant Boiler Feed Water
Huaneng Yuhuan Power Plant’s 300 m³/h RO system treats high-hardness groundwater (Ca²+>400 mg/L), producing water with conductivity <5 μS/cm. Replacing traditional ion exchange, it saves 90% annual acid/alkali consumption and reduces hazardous waste by 800 tons.
III.Drinking Water Advanced Treatment
-Qujing Brackish Water Reconstruction, Yunnan
A RO system in Qujing treats brackish water with TDS=2,800 ppm, producing water with TDS=150 ppm and solving drinking water safety for 30,000 residents, with a 2.5-year investment payback period.
-Bottled Water Production Line
Nongfu Spring’s Qiandao Lake factory uses RO membranes to treat lake water, removing bromate and heavy metals for natural water production, with microbial indicators complying with *Bottled Drinking Water Hygienic Standards* (GB19298).
IV.Zero Liquid Discharge (ZLD) of Wastewater
-Coal Chemical High-Salt Wastewater Treatment
An Inner Mongolia coal-to-oil project employs "RO+evaporation crystallization" for high-salt wastewater (TDS=12,000 ppm). RO permeate is reused in circulating water systems, while concentrated brine is evaporated to produce industrial salt (NaCl purity>95%), achieving ZLD.
-Electroplating Wastewater Heavy Metal Recovery
A Shenzhen electronics factory’s RO system retains Ni²+ and Cu²+ (>500 mg/L) in wastewater, concentrating Ni²+ to 5,000 mg/L for electrolytic recovery. The permeate is reused in cleaning tanks with >90% recovery rate.
Conclusion
Reverse Osmosis equipment has become a core technology for global water recycling and high-purity water treatment, thanks to its superior desalination capability and wide application. From desert seawater desalination plants to advanced semiconductor fabs, and from remote brackish water projects to high-challenge industrial wastewater treatment, RO technology continues to improve through material innovations (e.g., low-energy membranes, anti-fouling coatings) and system optimizations (e.g., salt-splitting processes, intelligent O&M). In the future, integrated with renewable energy (solar/wind power), RO equipment will play a pivotal role in the "water-energy-food" nexus, supporting global sustainable water management goals.
