What is reverse osmosis machine and how does it work?
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Update time : 2025-08-12 17:54:24
We learned in science class that osmosis is a natural process that delivers water and nutrients to living cells. The cell membrane is a natural semi-permeable membrane, meaning only certain substances can pass through while others are blocked. An osmotic membrane allows only water molecules to pass through easily, while intercepting various contaminants. When such a membrane separates two aqueous solutions of different concentrations, osmosis causes water to flow from the dilute solution to the concentrated one, as if to dilute the latter. The process of reverse osmosis, however, is the opposite. In reverse osmosis, pressure is applied to the solution with a higher solute concentration, reversing the direction of liquid flow—from the concentrated solution to the permeate, which is completely different from the direction of natural osmosis. Through the artificially synthesized reverse osmosis membrane, only water molecules can pass through smoothly, with almost no other molecules accompanying them. These water molecules that pass through the membrane are collected in a storage tank for later use. The remaining raw water, which contains a higher proportion of contaminants, is eventually discharged. The "ion exclusion" principle utilized in reverse osmosis refers to the fact that ions (i.e., charged atoms) form a barrier on the membrane surface, thereby preventing contaminants from passing through. It can be said that reverse osmosis systems separate water from minerals, which is fundamentally different from the principle of "removing minerals from water" in traditional filtration systems. Since Total Dissolved Solids (TDS) cannot be removed by mechanical filtration or standard carbon filtration, reverse osmosis systems have become one of the most effective filtration methods for removing TDS. During the operation of a reverse osmosis system, as water molecules pass through the membrane to the low-pressure side, the TDS level on the high-pressure side of the membrane continuously increases. This high-TDS water is directly drained into the sewer, while the water that has passed through the membrane contains almost no TDS and can be used directly. Semi-permeable membranes are crucial for ensuring the effective operation of the reverse osmosis process. Nowadays, the most commonly used artificial semi-permeable membranes are made of cellulose acetate, cellulose triacetate, or aromatic polyamide resins. These membranes are tough enough to withstand the high water pressure required in the reverse osmosis process, thereby ensuring that the system's contaminant removal efficiency is at its optimal level. Unlike ion exchange systems that require frequent regeneration, ordinary reverse osmosis membranes can typically be used for two to three years before replacement.
