Process principle and characteristics of two-stage reverse osmosis pure water equipment

The process principle of the two-stage reverse osmosis pure water equipment can be divided into the following links:

‌1. Pretreatment system‌

The raw water first passes through a multi-media filter to remove suspended solids, silt and other large particle impurities; then it passes through an activated carbon filter to absorb residual chlorine, odor and organic matter; some systems are equipped with a softener or antiscalant dosing device to reduce hardness and prevent subsequent membrane scaling. The pre-treated water also needs to pass through a security filter (precision filtration) to intercept tiny particles to ensure that the incoming water meets the requirements of the reverse osmosis membrane.

2. Primary reverse osmosis treatment

The pre-treated water is pressurized by a high-pressure pump and then enters the first-stage reverse osmosis membrane assembly. Driven by pressure, water molecules pass through the semi-permeable membrane (pore size is about 0.1 nanometers), while pollutants such as dissolved salts, colloids, and microorganisms are intercepted, producing primary pure water. This stage can remove more than 90% of impurities and ions.

‌3. Secondary reverse osmosis treatment‌

The primary water is pressurized by the secondary high-pressure pump and then enters the secondary reverse osmosis membrane assembly. Since the concentration of impurities in the primary water has been greatly reduced, the secondary membrane can achieve a higher desalination rate (usually more than 98%) at a lower operating pressure, further removing the remaining trace dissolved salts and organic matter, and producing a higher purity secondary water. Some systems will mix a small amount of secondary water with primary water to stabilize the water quality.

‌4. Post-processing system‌

Secondary water production may be sterilized by ultraviolet light or ozone to ensure that microbial indicators meet standards. In some scenarios, a pH adjustment unit or degassing device will be added to meet the requirements of specific industries for water conductivity or pH value.

‌Technology features‌:

1. Adopt two-stage reverse osmosis series structure to improve water purity step by step;

2. High-pressure pump and membrane assembly are the core power and separation units. The membrane structure includes a polysulfone support layer and a desalination layer to achieve selective filtration;

3. The effectiveness of the pretreatment system directly determines the membrane life, and the sand filtration, softening and other process combinations need to be designed according to the characteristics of the raw water;

4. The automated control system monitors pressure, flow and water quality parameters in real time to ensure stable operation.