Many factory schools now have water purifiers installed, and many people will be curious as to why the water purifiers will discharge waste water. The water purifier is also called a reverse osmosis water purifier. What is its filtration mechanism?
Why is it called "reverse osmosis" filtering?
When the same volume of dilute solution (such as fresh water) and concentrated solution (such as salt water) are placed on both sides of the semipermeable membrane, the solvent in the dilute solution will naturally pass through the semipermeable membrane and spontaneously flow to the side of the concentrated solution. This phenomenon is called infiltration. When the permeation reaches equilibrium, the liquid level on the concentrated solution side will be higher than the liquid level of the dilute solution, that is, a pressure difference is formed, and the pressure difference is the osmotic pressure. If a pressure greater than the osmotic pressure is applied to the side of the concentrated solution, the flow direction of the solvent will be opposite to the original direction of permeation, and the flow from the concentrated solution to the side of the dilute solution begins. This process is called reverse osmosis.
Simply put, by energizing, applying pressure to the concentrated solution, changing the original direction of penetration, and realizing the countercurrent of the concentrated solution, thereby purifying the concentrated solution and producing pure water.
Why does the reverse osmosis water purifier produce wastewater?
The core part of the pure water machine is actually a liquid concentration process during the working process. The salt content in the water increases with the flow of water through the surface of the reverse osmosis membrane, and the osmotic pressure of the water increases continuously. When the osmotic pressure is increased to the pressure of the booster pump, water cannot flow into the clean water end through the reverse osmosis membrane. The water that fails to pass this part is the wastewater generated when water is produced.