Key Points of Reverse Osmosis Water Treatment Technology

Basic Principle of Reverse Osmosis
When pure water and salt water are separated by an ideal semipermeable membrane, the membrane allows only water to pass through while preventing salt from passing. Water on the pure water side will spontaneously flow through the membrane into the saltwater side, a phenomenon known as osmosis. Applying pressure to the saltwater side inhibits this flow. When the applied pressure equals the osmotic pressure, the net flow of water is zero. If the applied pressure exceeds the osmotic pressure, the flow direction reverses, causing water in the saltwater to flow to the pure water side. This phenomenon underpins the basic principle of reverse osmosis (RO) water treatment.

Introduction to Reverse Osmosis
The pore size of an RO membrane is as small as a nanometer (1 nanometer = 10^-9 meters). Under certain pressure, H2O molecules can pass through the RO membrane, while inorganic salts, heavy metal ions, organic matter, colloids, bacteria, viruses, and other impurities cannot. This effectively separates pure water from the concentrated water.

Purpose and Considerations of Reverse Osmosis Pretreatment
When using a reverse osmosis system, special attention must be paid to raw water pretreatment. This is to avoid clogging the system by removing suspended matter and reducing turbidity. Sterilization is also necessary to prevent microbial growth.

Reverse osmosis requires low levels of suspended matter in raw water. The pollution index measures water quality regarding suspended matter, essential for determining the potential clogging of the RO system. The pollution index should not exceed 5, with a recommended value of less than 3. The pH of the inlet water should match the RO membrane requirements, and the temperature should be controlled to maintain membrane integrity and performance. Typically, for organic membranes, a temperature range of 20-40°C is suitable, while for composite membranes, 5-45°C is appropriate.