Reverse osmosis water treatment systems - healthy or not?

Hello.



Today I would like to share with you my vision of water purification systems.

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I do not want to discuss the various filters, the inefficiency of which has long been known - we will talk about reverse osmosis cleaning systems, which are actively used both in industries that produce purified water and in everyday life.



Unfortunately, around these systems there is a lot of marketing noise, which is intended to make a profit by the system manufacturer, but often has nothing to do with the quality of the product.



Due to the lack of understanding of how the system works and what kind of water should be consumed, the user often buys extra components and consumables, and water manufacturers save on vital details by releasing water that is undesirable for consumption.



Let's figure it out.

Theory and its implementation

So, the materiel tells us that reverse osmosis is a process in which, at a certain pressure, the solvent (water) passes through a semipermeable membrane from a more concentrated to a less concentrated solution, that is, in the opposite direction for osmosis. In this case, the membrane passes the solvent, but does not allow some substances dissolved in it. The water that passes through the membrane is called permeate, water with a high concentration of salts, which remains and is discharged - concentrate.



Reverse osmosis has been used since the 1970s for water purification, for obtaining drinking water from seawater, for obtaining particularly pure water for medicine, industry and other needs.



Immediately make a reservation: reverse osmosis is effective in removing particles with sizes from 0.001 to 0.0001 microns from water. Hardness salts, sulfates, nitrates, sodium ions, small molecules, dyes, iron, trace elements, heavy metals fall within this range. The membrane does not trap low-molecular substances, such as gases such as oxygen, chlorine, carbon dioxide, etc. It is because of the presence of these gases in the permeate a weakly acid reaction is observed, up to a pH of 5.



The membrane reacts extremely poorly to organochlorine, organic solvents, large mechanical particles. For this reason, a coarse mechanical filter or a unit for preliminary purification of water in front of the membrane is usually used, as well as a carbon filter for the removal of organochlorine and organic matter in general. Filters are consumable items, if they are not changed, then, taking the quality of water in our water supply system, sooner or later the membrane will be damaged - and then the repair will cost much more.



It should also be remembered that even when using pre-cleaning and its timely replacement, the membrane should sometimes be washed: chemical antiscalants / dispersants are used for this, which dissolve aluminum salts deposited on the membrane (mainly oxychlorides used as coagulants on water channels), calcium sulfates , calcium magnesium carbonates and iron hydroxide. Sometimes they write that these reagents wash colloids of silicon oxide, dissolve precipitates of calcium fluoride and strontium and barium sulfates - well, this means that the reagent contains complexone 3 (Trilon B) and some surfactants, which means stories about The tenderness of membranes in relation to high molecular weight organic compounds is strongly attracted by the ears. However, it is difficult to imagine the presence of such precipitation in significant quantities after pre-treatment.



What are the nodes usually after the membrane?

1. Coal post-filtration is often used to remove residual chlorine - a small linear filter filled with activated carbon through which permeate passes. His task is to catch the remnants of dissolved chlorine and organic matter passing through the membrane. Since the water after a normally operating membrane contains few negative impurities, the load on the post filter is low, and therefore it should be changed less often.
2. Mineralizing cartridges (remineralizers) are the most important element for lovers not to lose the minerals obtained from food - the cartridge fills in minerals lost on the membrane, but instead of a mixture of useful and harmful mineralizer adds only useful ones. As a rule, water is mineralized by macronutrients, such as calcium, magnesium, sodium, potassium. It also replenishes the anionic composition, although in fact it does not matter. Without a mineralizer, you will consume water that does not contain calcium and magnesium - and therefore it can potentially lead to osteoporosis, especially in children and women: in this case, the elements will simply be “washed out” from the teeth and bones. Unfortunately, it is on this site that unscrupulous producers of purified water are saving.
3. Structurizers are a separate cohort of cartridges that can hardly be called filters, since it is almost impossible to test their effect on water. Their task is to “change the structure of water for the better” under the influence of various kinds of factors. The winners of the “Battle of psychics” approve. Exclusively distributing marketers for extra money.
4. Ultraviolet disinfection - as in a number of other equipment, this element has its own narrow purpose - to prevent the consumer from getting any viable microorganism. It is extremely difficult for me to imagine a microorganism that is less than 0.001-0,0001 microns, is contained in water in significant quantities, is harmful and is passed through by the water utilities services.
5. PH correction systems are essentially phosphate dispensers and sodium sulfite dispensers designed to raise the pH to 6.5-7.5 (it was already written above that after reverse osmosis water is slightly acidic) and to bind free oxygen. The argument of marketers are scary stories about drained skin, falling hair, and dissolving teeth. Regarding skin and hair - here I would send marketers to their colleagues in the sale of shampoos with a pH of 5.5 - in the worst case water after reverse osmosis is not very far on the scale from the "best shampoos", and problems with teeth will not be caused so much acidic, how much demineralization - see above (by the way, the pH of vinegar and lemon juice - about 2, apples and cherries have a pH of about 4 - the teeth do not tolerate anything). In fact, the combination of free oxygen and weakly acidic pH corrodes all the metallic elements — and this is what needs to be eliminated, although it is difficult for me to imagine enhanced corrosion of high-grade food grade stainless steel under these conditions. Well, if it is high quality and stainless, of course.
   
   However, for the purely organoleptic qualities of drinking water, the pH can be adjusted - but certainly not by buying an expensive reagent, but by a simple dosage of a dilute baking soda solution.

Total, what we have consumables?

1. Pre-filters. You will not change - kill the membrane.
2. Antiscalant / dispersant for washing the membrane. If the pre-filters are changed on time - almost no need.
3. Coal post-filters. If you do not change - nothing terrible will happen.
4. Mineralizing cartridges. Required.
5. Structurizers. Useless.
6. Ultraviolet disinfection (sometimes you need to change the lamp). Useless.
7. Solution for pH correction system. Easily changed to baking soda solution. Provided a quality system - it works the same.

And now - some results of water analysis, which I came across in life, by which one can recognize the purification system by reverse osmosis and what is saved in it.

Practical experience

Frankly, I have not met in the post-Soviet countries tap water, which would have problems with heavy metals. I do not declare order for organochlorine or microbiology, but the elemental composition of water is in fact the problem most often associated with the following:

• Rigidity. Traditionally, water is almost always very hard. Well, we see it on scale in kettles. It is fraught with sand and stones in some organs.
  
  Recommendations of the World Health Organization (WHO) for drinking water: calcium - 20-80 mg / l; magnesium - 10-30 mg / l. For the rigidity of any recommended value is not proposed, but it is associated with the content of these elements. Russian regulatory documents (SanPiN 2.1.4.1074-01 and GN 2.1.5.1315-03) for drinking water are regulated by: magnesium - not more than 50 mg / l; rigidity - no more than 7 °.
  
  Standard of physiological usefulness of bottled water (SanPiN 2.1.4.1116-02): calcium - 25-130 mg / l; magnesium 5–65 mg / l; rigidity - 1.5-7 ° W.
• Iron. Because of the old rusty pipes - we get a high iron content. This is not particularly harmful, but it affects the organoleptics - the water tastes "rusty." And therefore SanPiN regulates no more than 0.3 mg / l of iron, however, in some cases the figure can be raised to 1.0 mg / l.
• Aluminum. Vodokanal technology uses aluminum oxychloride as a coagulant. SanPiN allows up to 0.5 mg / l of aluminum, but personally I strongly suspect that the figure is overestimated due to technologists, in the same Europe, according to 80/778 / EU, the level should not exceed 0.3 mg / l with an optimal figure of 0 , 05 mg / l. Aluminum is a rare rubbish , and therefore the smaller it is, the better.

The systems that you plan to use for cleaning should first deal with these elements.



And what is the result?



In a number of cities and regions, the water is very soft, for example, the city of Kuznetsovsk (now Varash), in which the Rivne NPP is located, can boast of such water:





At first glance it may even seem that this is deionized water, but this is not so: pay attention to lithium, iron, and silicon. Having rather low hardness values ​​(even too much - according to WHO), water is not de-ionized.



But unfortunately, in other regions the situation is not so good - yes, it is rarely possible to meet the MPC exceedances in tap water, but the numbers are often close to unpleasant values.



Some examples are:





Pretty tough with an anomalous ratio: magnesium content is higher than calcium. Sufficiently high content of strontium (however, below the MPC) - probably feeds from underground sources.







Different in geography of the city, but the same: hard, salty water.



Summing up: to find water that would be optimal for use is almost impossible. It is in such cases that cleaning systems are used. True, with varying success.



Amway's highly publicized water purification system partially copes with the task:







Yes, aluminum and iron are related, but the rigidity has remained, as before: the content of calcium and magnesium has not changed. However, it’s fair to say that these contents did not exceed the norm. However, when we introduced calcium and magnesium supplements, which corresponded to 100 mg / l and 50 mg / l, respectively, the filter still “missed” these elements.



If you use a reverse osmosis purification system, then eventually the permeate can have the following composition:





I even saw several certificates of quality of draft water for sale, which were praised by similar figures. However, in fact this means that the manufacturer saved on remineralization - and you drink deionized water with all the consequences of osteoporosis like this - pay attention to extremely low values ​​for common elements like calcium, magnesium, potassium and even silicon.



This is how high-quality purified water usually looks.





As you can see, there is nothing superfluous, but the levels of calcium and magnesium, in accordance with the recommendations of the WHO, are almost no aluminum and iron. A small level of sodium, potassium and phosphorus is the result of the work of the acidity corrector, it uses exactly sodium and potassium phosphates. This water is sold for baby food company Bebivita.



And here is the result of the analysis of their water, when the remineralizer gradually began to wear out:





Calcium and magnesium fell, phosphorus increased slightly - before that its solubility was restrained by calcium and magnesium - it's time to change the cartridge urgently!



Usually, in modern cleaning systems, the need to change the cartridge is indicated by sensors, which by their nature are conductometers, that is, they measure the conductivity of water, which, as we know, depends on the content of dissolved salts in it (by the way, Xiaomi and other Chinese companies offer water "on the same principle, which is generally funny).



Unscrupulous water manufacturers often trick these sensors as follows:





Before you - the result of the analysis of purified water from the cooler in Kazan: according to the level of magnesium and calcium, water is not recommended for drinking, but there is an abnormally high sodium content! This is not sodium from pH corrector - phosphorus is too low. And even if instead of branded liquid, soda was used for correction, this is not our case either: potassium is too low, and it is a natural soda contaminant. Just the developer poured salt in his deionized, to deceive the sensors total salt content. This water should not drink, although a primitive device and shows that everything is fine.

findings

First - the sad statistics:

• According to various estimates, the share of fresh water in the total amount of water on Earth is 2.5–3%.
• The distribution of fresh water across the globe is extremely uneven. In Europe and Asia, where 70% of the world's population lives, only 39% of the river waters are concentrated.
• At the moment, it is safe to say that about 80 countries suffer from a shortage of fresh water suitable for drinking. First of all, it is worth noting the north of Asia, the Middle East, China, Mexico, Argentina, Chile and even the western states of America. The territory of Australia is under serious threat due to water scarcity.
• According to the UN at the beginning of the 2000s, more than 1.2 billion people live in conditions of constant shortage of fresh water, about 2 billion suffer from it regularly. By the middle of the XXI century, the number of people living with a constant shortage of water will exceed 4 billion people.

It can be said that at present the quality of tap water meets the standards, but sometimes there are dangerous approaches to the MPC level. Water does not have toxicity, but can cause some disturbances with constant use.



To improve the quality of water the most technologically advanced and convenient are reverse osmosis systems. However, as around any technology that is gaining popularity, there is a lot of speculation - both from suppliers and vendors of systems, and from enterprises that use them.



The most common customer / system user error is:

• Acquisition of unnecessary placebo sites, such as “structurizers”.
• Acquisition of expensive reagents, for example, pH regulators.
• Late maintenance of important system nodes.

The most frequent fraud on the part of manufacturers of purified water is the late substitution (or complete absence) of mineralizing cartridges.



PS Thanks for reading, in the comments I will try to answer questions as much as possible.