How reverse osmosis works

Disadvantages of reverse osmosis systems

It is worth being objective and trusting the facts. Along with a large number of undeniable advantages, reverse osmosis filters also have a set of disadvantages:

high cost of filters compared to less efficient systems;
large dimensions of the installation;
attention to preliminary water purification (the membrane is demanding on water);
low productivity (the need for storage tanks) - this item is easily eliminated by installing additional filter membranes;
discharge of filtered contaminants into the sewer with most of the water.

Professionals in the field of water treatment treat the above as necessary conditions, because the main thing is the result, and it is simply impossible to achieve deep water purification without reverse osmosis systems.

Rating and which model is better

Trademarks "Barrier", "Aquaphor", "New Water", Atoll, Aqualine have proven themselves well. They manufacture components themselves or use membranes from Filmtec, Pentair and Osmonics from the USA, TFC from South Korea. These semi-permeable media serve 2.5-5 years.

Systems are operational for 5-7 years if they are periodically serviced. Below, in the form of a kind of rating, the models that have become sales leaders are described.

Atoll

The Russian manufacturer uses PENTEK brand cartridges and flasks (Pentair Corporation products) in its systems. All elements are fastened according to the John Guest standard - they are quickly disassembled without the use of special tools.

The modules are equipped with cartridges of Big Blue, Slim Line and Inline standards, which are sold all over the world. The manufacturer claims that each part is tested for leaks.

Among buyers, the Atoll A-575m STD model is popular.

Technical description:

Price	14300 r.
Number of cleaning steps	5
Performance	11.4 l/h
Volume of the tank	18 l (12 l - usable volume)
Additional functions	Mineralization

Pros:

• Compact size, light weight (5 kg);
• Long service life;
• Ease of maintenance;
• Volumetric tank;
• Removes 99.9% of contaminants and pathogens, then infuses the fluid with beneficial mineral compounds.

Minuses:

The cost of the system and replaceable elements is higher than that of competitors.

Aquaphor

The company has been operating since 1992.The filters use Akvalen sorbent fiber, granular and fibrous sorbents. In expensive models, the membranes are hollow fiber. The company independently manufactures all components. Specializing in household filters.

The leader of sales is the model Aquaphor OSMO 50 isp. 5.

Technical description:

Price	7300 r.
Number of cleaning steps	5
Performance	7.8 l/h
Volume of the tank	10 l
Additional functions	No

Pros:

• Affordable price;
• Removal of particles larger than 0.0005 microns;
• Easy cartridge replacement.

Minuses:

• Large weight - 10 kg;
• Operates at a pressure of at least 3.5 bar, there is no pump included.

new water

The company has been in existence for over 12 years. The manufacturer Novaya Voda has joined the International Water Quality Association. In Russia, only two companies have received such an invitation. New Water products comply with the ISO 9001:2008 quality certificate and the ISO14001:2004 environmental management system certificate.

The Econic Osmos Stream OD310 won the trust of customers. This system is based on the latest technology.

Reference. Pre-treatment is handled by one powerful filter, not three, as in standard systems.

Econic Osmos Stream OD310

Technical description:

Price	12780 r.
Number of cleaning steps	3
Performance	90 l/hour
Tank	missing
Additional functions	installation of a post-mineralizer is possible

Pros:

• High-performance membrane Toray (Japan);
• Compact - the system does not need a tank, it quickly purifies water in real time;
• Small drain of liquid into the sewer;
• The membrane serves at least 3 years, the pre- and post-filter must be changed once every 6-12 months;
• The system is lightweight - weighs 2.1 kg;
• The filter is operable at a pressure of 2 atmospheres, withstands loads up to 52 atm.;
• Replaceable elements are easily disconnected;
• Warranty 3 years.

Minuses:

High price.

TO300 with the possibility of installing a mineralizer

Another popular model from the Novaya Voda company is TO300. This is a budget option from the manufacturer. Direct-flow system with reverse osmosis satisfies the drinking water needs of 2-3 people.

Technical description:

Price	4940 r.
Number of cleaning steps	3
Performance	11.4 l/h
Tank	missing
Additional functions	installation of a post-mineralizer is possible

Pros:

• Cartridges and Toray membrane retain 99.9% of contaminants;
• The filter softens the water well;
• The system can be expanded by installing a water tank, an additional filter or a mineralizer;
• Very light and compact design - 1.2 kg;
• Easy installation;
• Elements are quick-release.

Minuses:

The diverter through which the filter is connected to the water supply does not withstand the warranty period.

Barrier

The Russian company has been making filters for over 15 years. Water purification systems are made from durable BASF plastic, Norit coconut charcoal serves as a sorbent.

Interesting. For each region of Russia, experts recommend a specific filter.

Buyers appreciated the model Barrier PROFI Osmo 100.

Technical description:

Price	7500 r.
Number of cleaning steps	5
Performance	12 l/hour
Volume of the tank	12 l
Additional functions	No

Pros:

• Reliable system for an average price;
• Fast water purification;
• High build quality.

Minuses:

• Frequent replacement of filters;
• Takes up a lot of space under the sink.

Why is water pretreatment needed and how does it work?

The quality of pre-treatment of water before it is fed to the reverse osmosis membrane is of great importance, since the service life of the membrane element depends on it. It must be remembered that domestic reverse system osmosis is designed for post-treatment of tap water, previously purified at centralized stations, or water that has been purified at local water treatment plants. Household reverse osmosis systems are not intended for direct purification of water from a well or a well, since in most cases such water contains significant amounts of various impurities - iron and manganese, hardness salts, natural organic substances and others.

All these impurities are effectively removed by reverse osmosis, but very quickly disable the most expensive element of the system - the reverse osmosis membrane (Fig. 4). Therefore, the purification of untreated water using domestic reverse osmosis is primarily inexpedient from an economic point of view.

Rice. 4. Contamination of the domestic osmosis membrane due to poor quality water treatment

At the pre-treatment stage in household systems, three cartridge filters (pre-filters) are mainly used (Fig. 5):

1. Polypropylene mechanical filtration cartridge with a filtration rating of 5-10 microns, designed to remove all kinds of mechanical impurities found in tap water - grains of sand, rust and scale particles and other particles. Removing these impurities prolongs the life of subsequent cartridges and the system as a whole. The service life of a mechanical filtration cartridge depends on the turbidity of the treated water and averages 3–6 months.Untimely replacement of a cartridge clogged with accumulated mechanical impurities can lead to a decrease in water pressure at the inlet to the membrane element and, as a result, to a decrease in system performance.

Rice. 5. Types of filtration cartridges:

a) polypropylene mechanical filtration cartridge; b) cartridge with granular activated carbon; c) "carbon-block" type cartridge

2. Cartridge with granular activated carbon to remove natural organic substances and active chlorine from tap water, which adversely affect the reverse osmosis membrane. In this case, both coconut and bituminous activated carbon can be used as a cartridge filler. The first refers to microporous coals and effectively removes impurities of active chlorine and organochlorine compounds from water, the second is mesoporous and very effective for removing natural organic compounds contained in surface waters and tap water obtained from them. The service life of a granular activated carbon cartridge also averages 3-6 months. The actual resource of this cartridge depends on such indicators of the quality of the treated water as oxidizability and color. Untimely replacement of the cartridge at this stage can lead to clogging of the membrane element, the development of microorganisms on the membrane surface due to the breakthrough of nutritious natural organic matter through the depleted layer of activated carbon. In turn, this will shorten the life of the membrane element, and may degrade the quality of water treatment.

3.In the third stage, different cartridges can be used, depending on the type of reverse osmosis system. In the case of inexpensive systems, a polypropylene cartridge with a filtration rating of 1 or 5 microns is used at this stage to remove carbon particles that may be washed out from the previous cartridge, as well as possible residual mechanical impurities. In systems of a higher class, a cartridge is installed using briquetted activated carbon (carbon block), which provides not only mechanical filtration, but also additional purification from chlorine and organochlorine. The service life of the cartridge of the third stage of prefiltration is 3-6 months. Thus, all three cartridges are replaced at the same time, which simplifies the use of a household reverse osmosis system.

How to choose the right reverse osmosis

So, we gradually got to the point of choosing the right filter for your home.

What should be taken into account, and what should be paid close attention to?

1. Be sure to see that a mineralizer is present in the system, otherwise it will be unpleasant to drink water after cleaning, and there will be no benefit from it at all.
2. A standard set of reverse osmosis involves the presence of 5 stages of purification: first mechanical, then coal, then fine (removal of the smallest impurities), membrane and finishing. The structurizer is installed sixth in a row. We have already talked about its capabilities, so do not be stingy and add equipment. Moreover, he will serve at least 2 years.
3. Be sure to read the instructions for the purchased equipment, make sure that all the necessary degrees of cleaning are available to it.

Table 1. Popular models

Praktic Osmos model OU400	The average cost of this device today is 6500 rubles. It has proven itself when working even from a low-pressure water supply, but the overall quality of workmanship leaves much to be desired. The product is very compact, so it can easily fit in the sink. The working pressure at the outlet is 2 atmospheres and above. The volume of the storage tank is 3.8 liters. The total weight is about 5 kg. Productivity is 125 l/s.
Atoll A-550	Such osmosis will cost more on average by 2000 rubles. This is a more serious and high-quality product. Production Russia. The weight of the product is 12 kg, 120 l / s of clean water, high-quality body and a metal tank of 5 liters. Removal of chlorine from water. Oddly enough, finding replacement cartridges for this equipment is not so easy.
Prestige M	This osmosis costs already 9500 rubles. It is capable of delivering higher pressure, as it is equipped with a pressure pump. 6-stage purification, excellent taste of water due to the presence of a mineralizer in the system. A metal tank of 12 liters, the average daily output is about 200 liters. Today in Russia this device is in the greatest demand.
Osmosis Expert MO530	Very compact and beautiful case, which allows you to install the system openly. High productivity about 250 l/s. High-strength tank with a volume of 7.5 liters. The highest degree of purification, silent operation of the pump and the average cost in the region of 14,000 rubles.

Of course, there are a lot of models and they all differ in their performance, so look for the best option and be sure to compare prices - they can vary significantly on different sites.

Service

Each element of the system needs to be changed in time. If this is not done, the quality of cleaning is reduced.

Service life of different elements:

• Membrane - 1-4 years;
• Pre-filters - 3-6 months;
• Post-filter - 6-12 months;
• Mineralizer - 8-12 months;
• UV system - 1 year.

Important. The higher the water flow, the more often you need to change the filter elements. Once a year, it is recommended to do a biocidal flush.

Drain the tank completely every month, especially at low flow rates. Then fill the tank and drain again

Once a year, it is recommended to do a biocidal flush. Drain the tank completely every month, especially at low flow rates. Then fill the tank and drain the water again.

Flush the membrane periodically. Shut off access to the tank and turn on the clean water tap. The membrane will operate continuously at maximum power.

How does a reverse osmosis filter work

Initially, plants of this type were used to desalinate sea water. But as soon as technology allowed the production of such devices in a smaller and more expensive version, they firmly occupied their niche in the household filter market.

The principle of operation of the device is based on the phenomenon of reverse osmosis - forcing water through a membrane with microscopic holes, the same size as H2O molecules. Larger particles are retained, so the output is almost demineralized water. Impurities that have not passed through the membrane filter in the form of a concentrated salt composition are drained into the sewer.

INTERESTING FACTS!

• The purest water, devoid of impurities, does not freeze at 0 ° C, but goes into a state called supercooling. It does not turn into ice until -38 °C and remains liquid.Scientists have found that for the appearance of ice crystals, a point of formation is needed, a foreign body in the water - an air bubble, a mote. If you shake a bottle of super-cooled water, bubbles will appear in it and it will instantly freeze.
• Water is an excellent conductor of electricity. But only not distilled, because electricity is carried by molecules of impurities and ions of substances dissolved in it.
• Everyone is familiar with the three states of aggregation of water - liquid, solid and gaseous. Scientists distinguish five phases of liquid water and as many as 14 phases of ice.
• At -120 °C, frozen pure water becomes viscous and viscous, and at -135 °C it becomes vitreous - solid, but without a crystalline structure.

For durable operation of the membrane, water is first passed through filters that remove mechanical suspensions and other impurities from it. Thus, the reverse osmosis water purification system consists of 4-5 stages, to which additional elements are optionally connected.

Is water purified in this way useful?

In society and scientific circles, there are two points of view about how useful water purified using reverse osmosis is for the human body.

1. Supporters of the first argue that water in the human body will only serve as a solvent, and, accordingly, the purer it is, the better.
2. Their opponents are of the opinion that water entering the human body is harmful from reverse osmosis.
   The liquid must, without fail, contain various trace elements that ensure human health.

Both of them use a lot of arguments, however, experts have not yet found evidence of the absolute correctness of one of the parties.

As arguments in favor of using water purified by reverse osmosis, the following can be cited:

• the content of mineral substances in water is far from those norms that are necessary for human life, he receives the lion's share of them with food;
• far from always, minerals in water are in a form that is absorbed by the body;
• water purified in this way has excellent extracting properties, which makes it possible to obtain healthy and tasty food when it is used;
• pure water does not cause allergic reactions;
• as a result of drinking pure water, the accumulation of harmful substances in the body is impossible.

Namely, these advantages have led to the widespread use of reverse osmosis plants for some industries.

How Reverse Osmosis Works

In short, the principle of operation of reverse osmosis is that water is driven under pressure through a special membrane filter that can only pass water molecules, and it also passes through a whole system of filters with different fillings. In this case, the water moves in the reverse osmosis direction, hence the name of the system. Purification products (soluble and insoluble in water) are removed through the sewer.

The structure of reverse osmosisThe system includes a series of filters that need to be changed periodically

So, let's now analyze the structure of this device in more detail. It consists of the following elements:

1. Fine filter that retains the smallest particles of sand and clay in the water.
2. Consistently connected cartridges with briquetted and granular activated carbon and foamed polypropylene - they also purify water from various kinds of inclusions.
3. Reverse osmosis membrane, which is responsible for purifying water from substances soluble in it.

Optionally, the following elements can be added to the system:

1. The pump responsible for creating the optimal working pressure in the system.
2. Mineralizer - to saturate water with useful minerals.
3. An ultraviolet lamp that will kill all microorganisms in the water.

The performance of reverse osmosis will depend on the model, but on average this value varies from 150 to 250 liters. This is quite enough to provide a large family with drinking water. However, it makes no sense to connect the device so that water is used through it for household appliances, and even more so for other needs, therefore such equipment is most often mounted directly in the kitchen, hiding it in cabinets.

A complete reverse osmosis kit includes a storage tank

The model and manufacturer will also tell you the total resource of the system. Here the difference in performance can be huge - the simplest devices will require the replacement of filter elements, passing through about 4,000 liters of water, while more expensive ones can handle 15,000 liters.

We have already said that insoluble substances can clog the membrane filter, the most important part of the system. To prevent this from happening, it includes pre-filters. There are also filters for final cleaning. The former become clogged faster (5-6 months, depending on the degree of water purity), while the latter serve an average of a year.

The system also has a storage tank for 4-12 liters, which stores clean water.Inside the tank, the pressure is optimal for drawing water.

How a reverse osmosis membrane works

Despite their effectiveness in water purification, reverse osmosis membranes are quite sensitive to oxidizing agents (chlorine) and precipitation, such as colloidal iron, which can “stain” the membrane surface. Therefore, in reverse osmosis filters there are modules for preliminary mechanical and sorption purification, which filter chlorine, sand, dirt and mucus. After pretreatment, water enters the module with the membrane.

To explain how a reverse osmosis membrane works, a simple example can be given: a juicer. Pretreated water is fruit, filter is a juicer, completely pure water is juice. Only unlike a juicer, the membrane can “squeeze out” not only the “pulp”, which is an analogue of undissolved impurities, but also substances that are dissolved in water.

Water with impurities under pressure is forced through a rolled-up membrane. All impurities - absolutely everything! - remain on the membrane itself, exceptionally pure water passes through. Another stream of untreated water passes along the membrane, washes away all impurities from it and sends them to the sewer. To get 1 liter of clean water, some filters consume as much as 10 liters of drainage water to flush the membrane.

The membrane itself, when untwisted, does not represent anything interesting - a thin polymer material that feels like masking tape to the touch. In the photo below - a piece of the membrane from the disassembled module from the filter in the hands of his wife, who watched our experiment with interest.

As mentioned above, so that people do not have to wait for the membrane to filter the water, reverse osmosis filters have special tanks in which purified water accumulates. Tanks are from 3 to 18 liters in volume. The most common tanks have a volume of 18 and 12 liters. And clean water is collected in them 12 and 9 liters, respectively - at least a third of the tank is occupied by air, under the pressure of which the water passes post-filtration and is supplied to a separate tap. The system is called a water-air tank.

How to choose a household filter

Manufacturers of purification systems also produce household water filters that use the phenomenon of reverse osmosis.

When buying it, you should pay attention to several factors:

• membrane quality;
• performance, the presence of a storage tank - a hydraulic accumulator (which is better - it is written here) for purified water, equipment with pumps and other design nuances;
• the degree of water purification by prefilters, the quality of their filter elements and the frequency of their maintenance or replacement;
• ease of installation of the device and its operation (dimensions of sanitary hatches);
• Availability of a guarantee and service departments that carry out warranty repairs, post-warranty maintenance and supply of components.

 
Water purification technologies are quite costly. Reverse osmosis plants help, to a large extent, correct the situation with the poor quality of drinking liquid.

You can see the principle of operation of a reverse osmosis water treatment system in the proposed video.

Factors affecting the operation of the reverse osmosis system

Conditions on which the effectiveness of reverse osmosis depends:

• pressure;
• temperature;
• acidity level;
• the material from which the membrane is made;
• chemical composition of source water.

Inorganic substances are most effectively separated in the process of reverse osmosis. For the best types of membranes, the degree of purification from such substances is 90-98%. However, membranes do a good job with organic substances. Since viruses and bacteria are of considerable size, their penetration through the membrane elements is excluded. But oxygen dissolved in water and some gases that determine the taste of water, the membrane passes.

Place for mounting

If you want to mount a reverse osmosis for an aquarium with your own hands or a system for domestic use, you will need to choose the right place for installation.

If you plan to use water for cooking, for drinking purposes, reverse osmosis is installed in the kitchen under the sink. Its size is usually quite compact. A faucet for drinking water is installed on the sink, for which an additional hole will need to be drilled.

It is convenient if all elements of the system are close to each other. The efficiency of the system largely depends on the length of the hoses to move the water.

Before collecting the return do-it-yourself osmosis, you will need to check all the elements of the kit for compliance with the incoming parameters. At the same time, the packaging of each component of the system is not disclosed, otherwise it will be difficult to make a return.

During this process, the membrane pressure, the inlet water temperature, and the flow pressure are checked. The manufacturer's instructions indicate what these indicators should be.

It is also worth considering that the system will need to be installed away from heating objects. Reverse osmosis should not be exposed to direct sunlight.First you need to turn off the water (cold and hot). Next, the valve is opened, which allows you to relieve pressure in the system. Then it is closed again. Next, the cartridges and the membrane, like your own hands, will need to be disinfected.

Filter design and characteristics

A home reverse osmosis system typically includes the following key components:

• pre-filters (single or multi-stage pre-cleaning);
• reverse osmosis membrane;
• post-filters (finish cleaning);
• storage tank.

The preliminary stage of purification allows to remove mechanical impurities, chlorine, a number of organic compounds from water. This allows you to maximize the life of the "heart of the system" - the membrane that performs the main fine water purification.

The photo gallery will present the standard package of the reverse osmosis unit:

Image gallery
Photo from
In the basic configuration of the system for fine filtration and preparation of drinking water, at least five working modules

From the water supply, water first enters a coarse filter made of foamed polypropylene. Here, water is freed from mineral and organic inclusions larger than 5 microns.

After the first stage, coarse water will have to go through another polypropylene filter, but with a porosity of 2 microns.

After passing the coarse and fine filters, the water enters the flask with a membrane filter. Here it is cleansed at the molecular level, getting rid of viruses and microbes at the same time

Not all water passes through the membrane filter. The one that did not pass is discharged into the sewer through a hose connected to the bottom of this module only

Ultra-thin membrane purification deprives water of the usual taste and pleasant smell.In order to return these properties, a carbon filter is included in the installation.

Next, the water enters the flask with a mineral filler. It is designed to saturate purified water with useful trace elements and minerals.

The minerals contained in the mineralizer not only restore the mineral composition required by the water, but also equalize the acid-base balance

Household fine water filtration unit

Flask with coarse filter

The second stage of rough cleaning

Membrane cartridge installation module

The bottom of the flask with a membrane filter

Charcoal filter to equalize the taste of water

Mineral filled module

Mineral filling of a flask with a mineralizer

Post-filters are installed for additional deep purification of the liquid, ionization, and improvement of its taste.

Fully "treated" water enters the storage tank, from where it is supplied through a special separate tap for clean water. Usually a crane is also included in the equipment delivery.

In order for the reverse osmosis filter to work for a long time, productively and efficiently, a certain pressure in the water supply is required. From 2.8 to 6 atm - optimal.

If the pressure is too low, a pump is needed; if the pressure is too high, care should be taken to install a pressure reducing valve.

A properly installed high-quality device has been working properly for many years - without breakdowns, leaks, failures. The user only needs to change the cartridges in a timely manner.

The reverse osmosis membrane needs to be changed approximately every 2-4 years. Preliminary filters - once every six months, final filters - once a year. You can do this work yourself.

Timely replacement of filters and membranes is the key to the efficient operation of the equipment and the health of all family members. This process is usually not difficult.

The subtleties of choosing an osmotic filter and additional elements

Before going to the store, several measurements are taken. They will help you make the right choice.

The pressure in the pipes is measured. For forcing liquid through the membrane and normal operation of the reverse osmosis system, at least 2.8 bar is required. If it is less, you can not do without a booster pump - a pressure booster pump with a transformer.

USEFUL INFORMATION: Reverse osmosis mineralizer: why you need it, maintenance and replacement

• Estimated household water consumption is calculated. Focusing on this indicator, determine the desired performance of the cleaning system. First of all, it depends on the membrane used. For domestic use, a 50G (8 l/h) or 75G (12 l/h) membrane is sufficient. Gallon (G) per day is a measure of membrane performance adopted by global manufacturers. 1 G=3.785 liters.
• Focusing on the throughput of the membrane, they acquire a water flow restrictor. This is a calibrated tube through which liquid is discharged into the sewer. For a 50G membrane, a flow restrictor with a value of 300 is suitable, for a 75G - 450, for a 100G - 550. With a low pressure in the water supply, a restrictor with a lower value can be taken.

• It is also recommended to measure the place under the sink to be sure that the selected model will fit there.
• For proper sealing of the joints, an FUM tape is purchased.

More information about the Atoll UP-7000/24V pressure booster pump on the manufacturer's website