The essence of reverse osmosis equipment is to reverse the natural osmosis process by external pressure, achieving molecular-level separation of water and impurities through a precision semi-permeable membrane. With its efficient water purification capacity, it has become the core of modern water treatment technology. Its working principle is to use a semi-permeable membrane together with externally applied high pressure to force water to flow against the natural osmosis direction, thereby separating dissolved salts, colloids, microorganisms, organic matter and other impurities in raw water to produce high-purity water. Its core principle relies on the reverse osmosis phenomenon.
Basic Concepts of Osmosis and Reverse Osmosis
Natural Osmosis: When solutions on both sides of a semi-permeable membrane (which allows only water molecules to pass through and blocks solutes) have different concentrations, water molecules spontaneously migrate from the low-concentration side (pure water) to the high-concentration side (salty water) until the concentrations on both sides reach balance.
The natural process requires no external pressure.
Reverse Osmosis: By applying external pressure higher than the natural osmotic pressure on the saltwater side of the semi-permeable membrane, water molecules are forced to pass reversely through the membrane from the high-concentration side (saltwater) to the low-concentration side (pure water), realizing impurity separation.
A high-pressure pump is required to provide driving energy.
Core Components of RO Equipment
Pretreatment System: Protects the RO membrane from clogging and damage.
Includes: Quartz sand filter (removes suspended solids), activated carbon filter (adsorbs residual chlorine and organic matter), precision filter (intercepts particles ≥5μm).
High-pressure Pump: Provides continuous high pressure (generally 4–15 MPa) to overcome osmotic pressure and drive reverse osmosis of water molecules.
RO Membrane Module: The core component, composed of spiral-wound or hollow-fiber membranes with a pore size of about 0.0001 μm (approximately twice the diameter of a water molecule), allowing only water molecules to pass through.
Post-treatment System: Such as UV sterilization and pH adjustment to ensure effluent water quality meets standards.
Working Mechanism of RO Membrane
Selective Separation:
Water molecules: Pass through membrane pores under high pressure into the pure water side (product water).
Impurity Interception:
Dissolved salts (such as Na⁺, Cl⁻, Ca²⁺) are intercepted with a removal rate of 95–99% or higher;
Microorganisms (bacteria, viruses), colloids and organic matter (molecular weight ＞ 200 Da) are physically blocked;
Heavy metals (lead, arsenic, etc.) are almost completely removed.
Concentrated Water (Wastewater): Highly concentrated wastewater containing intercepted impurities is discharged to avoid membrane fouling and blockage.
Key Parameters
Operating Pressure:
Seawater desalination: approximately 5.5–8 MPa (high osmotic pressure);
Household water purification: approximately 0.3–0.6 MPa.
Recovery Rate: The ratio of product water volume to inlet water volume (household RO is about 1:3, while industrial systems can reach 50–80%).
Salt Rejection Rate: The capacity of RO membrane to remove dissolved salts (standard membrane ＞ 97%, high-efficiency membrane ＞ 99%).
Application Scenarios
Drinking Water Purification: Household and commercial water purifiers (removing heavy metals, nitrates and pesticide residues).
Seawater Desalination: Converting seawater into fresh water (60% of global desalination plants adopt RO technology).
Industrial Water Supply: Ultrapure water for pharmaceutical and electronics industries, boiler make-up water.
Wastewater Reuse: Recycling of industrial wastewater (such as electroplating and printing & dyeing industries).
Specializing in water treatment technology, Xi'an DIEN Water Treatment Equipment Co., Ltd. boasts outstanding advantages in R&D, customized services, energy efficiency control and local technical support for reverse osmosis (RO) equipment. With years of industry accumulation, the company has formed a complete set of multi-level and all-round supporting solutions for water treatment projects. Its project cases cover zoned water supply for residential communities in hospitals, medical testing institutions, steel & power, chemical & electronic, pharmaceutical, light industry and food industries; urban Wastewater treatment, laboratory Wastewater treatment, pharmaceutical Wastewater treatment and high-concentration organic wastewater treatment for paper mills, textile printing and dyeing plants and washing factories; industrial Wastewater treatment for non-ferrous metal smelters, electroplating plants, surface coating plants and coking plants; as well as urban Wastewater treatment, seawater and brackish water desalination projects.
