Water purification encyclopedia: Why does the RO water purifier discharge waste water?
Many people will wonder why reverse osmosis water purifiers discharge waste water. What is the difference with the physical filter water purifier and what’s the filtering mechanism?
Why is it called "reverse osmosis" filtration?
When the same volume of dilute solution (such as fresh water) and concentrated solution (such as saline) are respectively placed on both sides of the semipermeable membrane, the solvent in the dilute solution naturally flows through the semipermeable membrane and spontaneously flows to the side of the concentrated solution. This phenomenon is called infiltration. When the permeate reaches equilibrium, the liquid level on the side of the concentrated solution will be higher than the level of the dilute solution by a certain height, that is, a pressure difference is formed. This pressure difference is the osmotic pressure. If a pressure greater than the osmotic pressure is applied to the side of the concentrated solution, the direction of flow of the solvent will be opposite to the original direction of permeation, and the flow from the concentrated solution to the dilute solution side will begin. This process is called reverse osmosis.
Simply put, by energizing, pressure is applied to the concentrated solution, the original infiltration direction is changed, and the reverse flow of the concentrated solution is realized, thereby purifying the concentrated solution and producing pure water.
Why there is waste water?
The process of the reverse osmosis membrane, which is the core component of the water purifier, is actually a process of liquid concentration. The amount of salt in the water increases with the flow of water through the surface of the reverse osmosis membrane, and the osmotic pressure of the water also increases. When the osmotic pressure is increased to the pressure of the booster pump, water cannot flow into the purified water through the reverse osmosis membrane. This part of the water that fails to pass is the waste water produced during water production.
"Waste water" is really nothing?
First of all, with the current development of clean water technology, basically producing a cup of pure water will be equivalent to the discharge of a cup of wastewater, that is, if your family can drink 3L of water a day, then this day will discharge 3L of wastewater, It will feel a lot at first glance, but compared with the flush toilet, mopping the floor, washing clothes and brushing bowls on this day, this water consumption is much smaller.
Moreover, the waste water is not useless, and it has also been filtered through the first three stages of the water purifier. The waste water can be used in large quantities and it is a good use to mop the floor, flush toilets and wash things.