Desalination rate and water yield are the most importan […]
Desalination rate and water yield are the most important parameters to measure the quality of the reverse osmosis membrane. What factors will affect the performance of reverse osmosis membrane? How do they affect reverse osmosis membranes? The Reverse Osmosis Systems Supplier will introduce it to you.
1. Inlet water pressure. The inlet water pressure will affect the water yield and desalination rate of RO membrane. Reverse osmosis technology overcomes the natural saturation pressure by applying operating pressure in the direction of inflow water flow. When the operating pressure applied to the concentrated solution side is higher than the saturation pressure, the movement direction of natural saturation of water molecules will be reversed, and the concentrated solution will pass through the membrane to become purified water on the dilute solution side.
The addition of inlet water pressure (the useful pressure to overcome saturation pressure) has a straight-line connection with the addition of water quantity through the membrane because RO membrane cannot completely intercept dissolved salts in the inlet water. With the addition of pressure, the rate of water permeation through the membrane is faster than the rate of salt transfer, and the desalination rate will be gradually added. However, the removal rate of salt is restricted by the upper limit after adding inlet water pressure. When a certain pressure value is reached, the desalination rate will not be added. In summary, with the addition of inlet water pressure, the water flux through the membrane will also be added, and the desalination rate will also be added to a certain extent. When a certain degree of desalination rate is reached, the desalination rate will not change.
2. Temperature. The reverse osmosis membrane system is very sensitive to the change of inlet water temperature. The increase of inlet water temperature causes the viscosity of the water molecules passing through the membrane to drop and disperse before being added. Therefore, with the addition of water temperature, the water flux increases linearly, and the transmittance of salt will also accelerate. Therefore, the higher the inlet water temperature, the greater the water yield, and together with this, the desalting rate will decrease, whereas the lower the water temperature, the smaller the water yield, but the desalting rate will increase. This is the reason why RO products produce less water and more wastewater in winter, but the water quality at this time is relatively higher (desalting rate added).
3. Salt concentration (TDS value of raw water). The salt concentration target of the influent will affect the saturation pressure, which is a function of the concentration and variety of salt or organic matter contained in the water. Salt concentration addition, saturation pressure addition (will offset the pressure of water inflow), under the condition of constant water production, to reverse the natural saturation activity direction of water inflow drive should also be added at the same time. When the pressure keeps stable, the higher the salt content in the influent, the lower the flux, adding the salt flux through the membrane (decreasing the desalting rate).
4. Recovery rate (wastewater share). If the recovery rate is added (the inlet pressure is stable), the residual salt content in the raw water will be higher, and the natural saturation pressure will be continuously added until it is the same as the applied pressure, which will offset the pushing effect of the inlet pressure and slow down or even stop the anti-saturation process, thus greatly improving the scaling problem caused by the tendency of salt deposition on the membrane surface. Therefore, when the recovery rate is added, the water yield will decrease and the desalting rate will also decrease.
5.pH value. The pH value has two effects on the anti-infiltration membrane element. At the top of the list is the effect of the normal operation of the membrane system on desalination rate. Second, the influence of pH value on the cleaning effect during cleaning. At pH 7 or so, the reverse osmosis membrane enjoys the highest desalting rate. With the change of pH, the salt permeability of the membrane system is added. However, too high or too low pH value is likely to cause membrane damage.