Can’t it just purify all the water?
In: Technology
Osmosis is the ability of water to pass through membranes, but not other minerals or chemicals. If you have a solution with lots of minerals and another solution free from minerals, separated by a membrane, then the water will be drawn, or pushed, through the membrane until the stronger solution is diluted.
Reverse osmosis uses extra pressure on the ‘concentrated’ side, the incoming impure water, to force this backwards, to force water from the ‘concentrated’ side to the ‘pure side’.
But the pressure you have to push with increases with the difference in concentration, impurities. If you just kept pushing water from the same pool through, the concentration of remaining impurities would get higher and higher, and the force needed to push against it higher. In addition, more impurities would get forced through with the water.
So you have to keep the level of impurities in the incoming water low, which means constantly replacing and then dumping, the input water before the concentration of impurities can get too high.
And do what with the impurities?
The waste water is water that has everything just removed from the filtered water. That has to go somewhere, so it is dumped.
The machine moves salts and other contaminants from one section of water to another. The “waste” water contains everything that was in the original tap water.
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