how does a reverse osmosis system work
The Reverse Osmosis System uses a semipermeable membrane to selectively separate soluble impurities in water under high pressure, thereby producing high-purity product water and discharging concentrated impurity water. It is widely used in electronics, electricity, chemical, pharmaceutical and other industries.
The following article will explain how the reverse osmosis system works from six parts: principle, components, process, advantages, disadvantages and application.
1. Core principle of reverse osmosis system
The reverse osmosis system applies external pressure (higher than the osmotic pressure of the solution) to force water molecules to pass through the semipermeable membrane from the high-concentration side (raw water) to the low-concentration side (product water), while dissolved salts, impurities, etc. are retained on the membrane surface and discharged with the concentrated water.
2. Key equipment for building reverse osmosis system
| Components | Functional Description |
| Reverse Osmosis Membrane | *Core component: usually a roll-type structure membrane made of aromatic polyamide composite material. *Pore size: about 0.0001 micron. *Structure: the surface is a dense separation layer to block impurities, and the lower layer is a porous support layer to guide water production. *Performance: can efficiently intercept >99% of dissolved salts and organic matter. |
| High pressure pump | Providing the raw water with the high pressure (usually 1.0 - 1.6 MPa or higher) required to overcome the osmotic pressure and membrane resistance is the power source for the system operation. |
| Pretreatment system | *Purpose: To protect expensive RO membranes from contamination, scaling and physical damage. *Composition: Usually includes quartz sand filter (to remove suspended solids), activated carbon filter (to remove organic matter, residual chlorine), softener or antiscalant dosing device (to prevent scaling), precision filter (security filtration, to remove >1-5μm particles). |
| Pressure Vessels | *Material: Stainless steel or fiberglass reinforced plastic (FRP). *Function: To accommodate and seal one or more RO membrane elements in series and withstand high pressure operating environment. |
| Control System | *Function: Real-time monitoring of key parameters such as pressure, flow, conductivity, pH, etc. *Purpose: Realize automatic system operation, regulation (such as concentrated water discharge), fault alarm and safety protection (such as high and low pressure protection). |
| Cleaning system | *Function: Chemically clean the membrane elements regularly or as needed. *Effect: Remove pollutants (such as inorganic scale, organic matter, microorganisms) accumulated on the membrane surface and restore membrane flux and Desalination performance. Commonly used cleaning agents include citric acid (acid cleaning), alkali solution (alkaline cleaning), etc. |
| Aftertreatment system | *Purpose: To further optimize RO water production according to the final water quality requirements. *Optional methods: pH adjustment (adding alkali), degassing (removing CO₂), ultraviolet (UV) or ozone (O₃) disinfection, mixed bed ion exchange or electrodeionization (EDI) deep desalination, etc. |
3. How does a reverse osmosis system work?
The work of the industrial reverse osmosis system is a multi-stage collaborative process:
① Pretreatment:
Remove impurities in raw water
Filter through quartz sand and activated carbon to remove sediment, residual chlorine and organic matter;
Use a softener or scale inhibitor to prevent scaling, and then filter out tiny particles through a precision filter to ensure the cleanliness of the incoming water.
② Reverse osmosis core treatment:
high-pressure membrane separation
The high-pressure pump pressurizes the water to 1-1.6MPa, driving water molecules to pass through the RO membrane;
Dissolved salts, bacteria, etc. are intercepted, and fresh water (product water) and high-concentration concentrated water are produced, with a recovery rate of about 70%-85%.
③ Post-treatment:
Optimize water quality indicators
Adjust the pH value to neutral as needed, or use resin/EDI deep desalination to meet the high-purity water needs of electronics, boilers and other scenarios.
④ Monitoring and maintenance:
ensuring system operation
Real-time monitoring of conductivity, pressure and other parameters, automatic control of concentrated water discharge;
When the membrane is contaminated, chemical cleaning (citric acid/alkaline solution) is initiated to restore filtration performance.
4. What are the advantages of reverse osmosis system?
Industrial reverse osmosis systems have significant advantages in the field of water treatment due to their high efficiency and reliability:
Excellent separation performance:
- lHigh desalination rate: The removal rate of soluble salts and ions is as high as 97% - 99% or more. When the raw water conductivity is 1000 μS/cm, the conductivity of the produced water can be reduced to below 10 μS/cm.
- lBroad-spectrum removal: Efficiently intercept pollutants such as organic matter, colloids, bacteria, viruses and heavy metal ions that are difficult to remove by traditional filtration.
Wide range of water sources:
It can effectively treat groundwater, surface water, municipal tap water and even municipal sewage and industrial wastewater that have been properly pretreated.
Energy saving:
The core separation process mainly relies on electric energy to drive the high-pressure pump, and the energy consumption per ton of water is usually only 1-2 kWh
No chemical addition:
The separation process itself is a physical process, and there is no need to add a large amount of chemical agents, which avoids the waste acid and alkali generated by ion exchange regeneration, and reduces the cost of agents and the risk of secondary pollution.
Stable and long life:
The life of membrane elements can usually reach 3-5 years under good maintenance, with a high degree of automation and relatively low maintenance costs.
Modular design:
The system is easy to design and integrate modularly, and the water output can be flexibly expanded from 1 ton per hour to thousands of tons to meet the needs of industries of different scales.
Support efficient utilization:
In wastewater reuse and zero discharge projects, concentrated water can be further processed to achieve resource recovery or near-zero liquid discharge.
5. What problems may arise when a reverse osmosis system is in operation?
Recovery rate: the ratio of produced water flow to raw water flow (usually 60-80%). The higher the recovery rate, the less concentrated water is discharged, but the risk of membrane pollution increases.
Desalination rate: the ability of the membrane to remove salt (usually >95%), which is affected by the salinity, pressure and temperature of the raw water.
Operating pressure: Insufficient pressure will lead to a decrease in water production, while too high pressure may damage the membrane.
Temperature: Increased water temperature will increase membrane flux (water production), but may reduce desalination rate.
6. Where can reverse osmosis systems be used?
Due to its high efficiency in desalination and impurity removal, reverse osmosis systems are widely used in:
- l Boiler feed water (power plants, chemical plants)
- l Ultrapure water preparation in the electronics industry
- l Purified water/water for injection in the pharmaceutical industry
- l Water for the food and beverage industry
- l Seawater/brackish water desalination
- l Deep treatment of municipal drinking water
- l Wastewater reuse/zero discharge
- l Chemical process water and material separation and concentration, etc.
Through scientific system design, strict pretreatment guarantee, reasonable operation parameter control and regular maintenance, the industrial reverse osmosis system can continuously provide efficient, stable and reliable high-quality water production to meet the increasingly stringent water needs of various industries. If you need to consult water treatment solutions, you can contact "https://www.envspro.com/" at any time.