Actively used to purify water from salts, sulfates, nitrates, dyes, sugar, bacteria, viruses. When cleaning water from gases such as chlorine or CO2 reverse osmosis installations are powerless.
The definition of “reverse” for osmosis is applied because, in natural conditions, water moves towards a more saturated solution (the process of direct osmosis). Reverse osmosis is possible only if there are devices of increased pressure.
Pros and cons of reverse osmosis
How reverse osmosis works
Water treatment and industrial liquid treatment plants are built on the same principle. They consist of:
- Thin-cleaning filters that eliminate coarse mechanical impurities;
- Chemical training systems;
- High-pressure pumps;
- Modules with membrane filters;
- control unit.
Water treated with a sediment-forming inhibitor is pumped by pressure-enhancing pumps (centrifugal or rotary) through membranes. On the one hand, purified water with a minimum amount of impurities merges. On the other – the remaining concentrate, which did not pass through the membrane. Periodically, the membranes are washed with special means to remove sediment from the surface.
What is the advantage of reverse osmosis?
Even today, scientists cannot fully weigh the pros and cons of reverse osmosis installations.
Modern technical capabilities have allowed the creation, in addition to industrial, a wide range of household units of reverse osmosis. They consist of a cleaning unit that includes filters:
- mechanical cleaning (usually foamed polypropylene);
- Coal (to remove gaseous impurities);
- membrane (own, osmotic);
- extra coal.
Many manufacturers install mineralizers that enrich the water with useful salts, and UV decontaminates in drinking water units.
- This design of the installation determines the most important quality – versatility. The main advantage of reverse osmosis is the ability to use it in houses and apartments, schools, hospitals, catering facilities, in public places. Powerful installations are widely used in industry and heat power.
- The second important advantage is the multivariability of the structures. You can choose from 8 liters per hour to 50,000 BPD.
- A high degree of desalination (cleaning) of water up to 98%. With minimal energy costs, water is almost completely cleared of salts, much smaller than water molecules. There is no need to heat or use chemical reagents. This point is quite controversial. It is attributed both to the advantages and disadvantages of reverse osmosis.
- Desalination of seawater. Industrial desalination can remove up to 95% of salts from seawater, which contains up to 35 mg per liter of salts of various origins (mostly NaCl). Powerful installations allow getting water clean up to 99.9%. The residual concentrate is drained or used in the chemical industry. Reverse osmosis plants can solve irrigation problems, the water supply of cities and enterprises, reduce the burden on natural freshwater bodies.
- The affordable price of household units. This is another plus of the reverse osmosis system. The simplicity of the design, energy independence and minimal maintenance costs make household installations cost-effective for many family members.
- Household reverse osmosis units will provide a constant supply of clean, fresh water in the house, regardless of bottled suppliers. Paying once for installation, you will get rid of the hassle of orders and dependence on the delivery schedule.
- Industrial reverse osmosis plants are not replaceable for several industries to produce purified and disused water: pharmaceutical companies, food production, water preparation for steam generators, chemical production, medical industry, microelectronics, etc.
What’s the downside of reverse osmosis filters
Despite the practicality and efficiency of water purification on semi-permeable membranes, the installation of reverse osmosis is not without disadvantages, some of which are very significant.
- The first is the need to clean the filter with chemical reagents periodically. How safe they are for the body – it remains only to guess. Manufacturers do not advertise their composition and ability to maintain their activity after rinsing the filter.
- The water on the way out has no taste. This lack of osmosis is somewhat far-fetched – in a natural state, water from natural sources is also devoid of its own taste. Giving some flavor minerals, in general, can be considered pollution, which should eliminate osmosis. In extreme cases, in bottles of purified water, it is easy to dissolve a pinch of kitchen salt and a tablet with pharmacy micronutrients.
- Another point against osmosis is the high cost of industrial systems. It is determined by the fact that the output of treated water is about 25%. The rest merges into the sewer in the form of saturated saline solutions. But so far, we can only judge the existing installations. In the future, this shortcoming will certainly be eliminated. In environmental impacts, thermal and chemical desalination is much more dangerous and more expensive in the aftermath.
- Significant minus osmosis filters – the system does not delay volatile chlorine. Yes, this flaw is outstanding, but coal filters and ozone can help with cleaning, which is even part of many domestic and industrial plants. It is impossible to neutralize chlorine 100%, but it is possible to reduce its concentration safely.
- The need for pre-preparation of water is also a disadvantage of the reverse osmosis system. It uses some reagents combined under the name “inhibitors.” As in the means for washing filters, their composition is not fully understood, and what danger they carry – is unknown. Mechanical cleaning is costly at large industrial plants, where water comes from natural water intake. In household networks, the liquid gets clean enough, and a certain percentage of rust and scale from pipes does not overload the installation.
- No useful minerals in the water. After reverse osmosis, the water is almost distilled. To eat, it must be enriched with minerals and salts. Practice shows that distilled water on the body is noticeable only if you consume it for 2 – 3 liters a day and do not eat anything salty, marinated, cooked with seasonings, or contain meat, raw vegetables, fruits, etc. fish. All the necessary minerals and trace elements enter the body with food, and purified water can not harm much. This point is difficult to attribute to the system’s shortcomings with reverse osmosis, as research is still underway, and it is too early to talk about any consequences. In addition, there are water mineralization systems that fully compensate for this lack of osmosis systems.
Why reverse osmosis is so popular, despite all the drawbacks
According to most engineers and environmentalists, reverse osmosis is the most effective way to solve the shortage of quality freshwater. And water can be cleaned both in industrial and at home. In desalination, reverse osmosis is still quite expensive and is used only on an industrial scale. Still, the prospects of its transformation into the main way of obtaining freshwater are visible to the naked eye.