Pure water to wastewater ratio of reverse osmosis water purifier

Update time : 2021-11-02 14:37:24

There are many water treatment devices and methods that we will come into contact with in our daily lives, especially the process of transforming natural water and tap water that has undergone preliminary treatment by water plants into drinking water. From boiling to the use of potassium aluminum sulfate (alum) and activated carbon to absorb impurities, and then filtering through a composite filter element to be used as drinking water. At the same time, if the standards continue to be raised and the final goal is to prepare pure water, there will still be a combination of distillation, RO reverse osmosis, ultraviolet radiation, deionization and other technical steps.

RO reverse osmosis is a technology that expands from the "decentralization" of the industrial and chemical fields to the household field with the wider application of semi-permeable membranes. This also brings a difference from the general filter water purifier/water dispenser. RO reverse osmosis water purifier that produces waste water. The main difference between the two lies in the latter's application of RO reverse osmosis technology, which is a further step in the water purification ability, and has the ability to reduce the content of water-soluble inorganic salts to produce softened water.

Considering that the ability of conventional filter elements to absorb and intercept impurities is always limited, the application of semi-permeable membranes can be said to have made a big step forward in the technology of water filtration. Here we should briefly introduce the chemical potential and osmotic pressure as the theoretical basis.

The chemical potential is similar to the temperature as a thermodynamic strength quantity. We know that heat is always transferred spontaneously from a high-temperature object to a low-temperature object. Similarly, microscopic particles always tend to transfer from a high chemical potential region to a low chemical potential region, which manifests itself in a specific Environmental conditions: When the two sides of the semi-permeable membrane that only water molecules pass through are aqueous solutions of different concentrations, it is the tendency for water molecules on the low concentration side to penetrate to the high concentration side.

But this trend is also not endless. On the one hand, as the water molecules pass through, the concentration of the solution will change in real time. On the other hand, the amount of more aqueous solution on the high concentration side will generate additional pressure, which will eventually form a pressure. In equilibrium with the chemical potential, this prevents water molecules from penetrating from the low-concentration side to the high-concentration side, and the minimum additional pressure applied from the high-concentration side is the osmotic pressure.

Understand this point, you can more easily understand the principle of RO reverse osmosis water purifier: through artificial means such as booster pumps to apply more pressure on the side of high-concentration aqueous solution (such as tap water), forcing water molecules to penetrate into the low On the concentration side, most of the salt cannot pass through the semi-permeable membrane, and can only be deposited on the high concentration side. In this way, the water flowing from the low concentration side undergoes various purification steps including filtration, adsorption, and softening, which is more suitable for drinking Of water.

Some readers may ask: Can the water purifier only use RO reverse osmosis technology instead of conventional filter elements? This is theoretically feasible, but in practice it is not suitable. On the one hand, considering the size and type of impurities, the larger solid impurities that can be blocked in conventional filter elements can be directly impacted on the semi-permeable membrane with water flow. The surface is likely to be damaged, and the semipermeable membrane with higher unit cost will be directly scrapped; on the other hand, due to the trade-off between cost and service life, the area of interception effect of the original conventional filter element is larger solid impurities, also A more economical solution is water that has been heavily filtered through physical, chemical, and adsorption methods. Among them, the trace amounts of salt that could not be used in the previous steps are then handed over to the semi-permeable membrane for interception, so as to maximize its service life and reduce The user’s cost of consumables. The old saying goes that you should use a sledgehammer to kill chickens. This sentence can also be used to purify water.

The last question to be answered is why the RO reverse osmosis water purifier produces wastewater. This is related to the semi-permeable membrane intercepting the salt on the high-concentration side. As mentioned earlier, the salt that cannot pass through the semi-permeable membrane will be deposited on the high-concentration side. At this time, in order to extend its service life, a self-cleaning method is required. On the surface of the high concentration side of the semi-permeable membrane, the carrier of this cleaning method is naturally the water that exists in the water purifier all the time. When the user turns on the faucet of the water purifier, the purification process is related to the flowing water. The cleaning process of scouring the surface of the semi-permeable membrane is carried out at the same time, and the accumulated salt is discharged together with part of the water as waste water. Although these high-salinity waters cannot be drunk, they have also undergone basic purification by a variety of filter elements before semi-permeable membranes, and there are many available scenarios, so they are not particularly wasteful of water resources.

Having said that, the improvement of the ratio of pure water to wastewater is also a hot topic developed by RO reverse osmosis water purifier manufacturers in recent years, from 1:3 to 1:1 in the early days, and then to the 3:1 pure wastewater that some products can do now. Compared with, the utilization rate of water resources has been greatly improved, and the cost of water consumption has been reduced. At the same time, it can be regarded as a contribution to the environment in which we live.

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