Factors affecting the effluent rate of single-stage reverse osmosis equipment:

1、 The impact of inlet pressure:

The inlet pressure itself does not affect the excess salt, but the increase in inlet pressure increases the net pressure driving reverse osmosis, resulting in an increase in water production. However, the excess salt remains largely unchanged, so the membrane's water infiltration rate is faster than the transfer rate of salt. The increased water production dilutes the salt passing through the membrane, reducing its permeability and improving the desalination rate of reverse osmosis.

However, increasing the inlet pressure to improve the desalination rate is limited. When the inlet pressure is greater than a certain value, a high recovery rate will increase concentration polarization, and some salts will also couple with water molecules through reverse osmosis membranes, resulting in excessive salt permeation, offsetting the increase in water production and preventing further increase in desalination rate.

2、 The influence of inlet water temperature

The conductivity of the produced water is sensitive to changes in the inlet water temperature (the room temperature of the produced water is 25 ℃). As the water temperature increases, the water flux increases linearly. For every 1 ℃ increase in inlet temperature, the produced water flux increases by 2.5% -3.0%. This is mainly due to the decrease in viscosity and enhanced diffusion ability of water molecules passing through the membrane. When the inlet temperature decreases by 1 ℃, the produced water flux decreases by 2.5% -3.0%. The viscosity and diffusion ability of water molecules passing through the membrane decrease. The increase in water temperature will lead to a decrease in desalination rate or an increase in salt permeability. This is mainly because as the temperature increases, the diffusion rate of salt in the membrane accelerates.

3、 The influence of salt content in influent water

The osmotic pressure of a single-stage reverse osmosis equipment is a function of the concentration of salt or organic matter in water. As the salt concentration increases, the osmotic pressure also increases. Therefore, the driving pressure of the influent that requires reverse natural osmosis flow mainly depends on the salt content of the influent. If the influent pressure remains constant, the higher the salt content, the smaller the flow rate. The increase in osmotic pressure offsets the driving force of the influent, while the decrease in water flux increases the salt flux through the membrane, leading to a decrease in desalination rate.

4、 The impact of system recovery

The reverse osmosis process is achieved by pressurizing the inlet water to reverse the natural osmotic flow direction between concentrated and dilute solutions. If the recovery rate increases (the inlet pressure remains unchanged), the residual salt content in the raw water will be higher, and the natural osmotic pressure will continue to increase until it is the same as the applied pressure, offsetting the driving effect of the inlet pressure, slowing down or stopping the reverse osmosis process, reducing or even stopping the permeation flux.

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