The way of water treatment, known as reverse osmosis, is applied already more half a century. Initially it was used in installations of desalting of sea water. Now the reverse osmosis gives the chance every day to produce many tons of the potable water cleaned from impurity.
Modules of reverse osmosis give the chance to carry out demineralization of water by means of transmission it through film membrane under certain pressure. At the same time through time of membrane there pass molecules of pure liquid, and the hydrated salt-forming ions and number of microelements are late.
The water treatment systems working at the principle of reverse osmosis differ on the performance, complete set, the sizes and other characteristics.
The design of installation of reverse osmosis usually depends from:
- composition of initial water;
- level of content of salts;
- structure of membrane group.
The arrangement decision is defined by way of the organization of membrane elements.
Installations of small performance give up to 5 CBM of purified water an hour. In devices of this kind the membrane elements install in the uniform body. It gives the chance to make system cheap and easy-to-work. Apply vertical and horizontal configuration of membrane elements.
Installations of average performance consist of two body which connects in parallel. Such design allows to raise exit of purified water. Devices of average performance can quite work with sea water. Most often here horizontal configuration of elements is applied.
The systems of high performance have more difficult device. To them the concentrate is given on additional membrane group that allows to provide pure maximum exit, reduces the general consumption of power. However high load of additional membranes forces to take measures for their additional washing. The hardware of similar systems differs in complexity.
The system of reverse osmosis usually includes:
- supporting structure;
- fine filter;
- high-pressure pump;
- membrane elements;
- system of washing of membranes;
- control board.
Installation of reverse osmosis gathers on bearer frame which in many respects defines exterior of adaptation. Also the rigidity of system, its durability and reliability depends on type of supporting structure. Rational configuration gives the chance to make installation convenient in operation, repair and service.
The best characteristics frames from the aluminum shape and stainless steel have. The painted metal designs are less often applied. The most perfect installations equip with wheel support which can be regulated on height.
On such metal base mount the pump, group of membranes, the filter, the closing valve, the pressure switch and the back valve necessary for washing of membranes. Devices of control and control of the device put on the front panel of frame.
The module of installation of reverse osmosis is executed from separate units and adapted for connection it for the pipeline and plum in sewerage system. Guidance system of installation is calculated on use in lines of three-phase alternating current.
Osmosis is basis of metabolism of living organisms. It serves for introduction to cage of nutritious elements and removal of slags. If to separate two hydrochloric solutions semipermeable membrane, it will begin to pass molecules of one size, but will turn into barrier to substances which molecules have the bigger size. For this reason of molecule of the salts dissolved in water cannot get through such membrane.
Provide that on both sides from membrane there are solutions containing salts of different concentration. Molecules of water will move at the same time from solution with weak concentration to more concentrated solution. Penetration of water through semipermeable wall goes even then when external pressure equally affects both solutions. Force under the influence of which liquid gets through membrane is called osmotic pressure.
When more concentrated solution is affected by the external pressure which is higher osmotic, molecules of liquid will begin to move through membrane in the opposite direction, that is from more concentrated solution to solution with smaller concentration of salts. This process is also called reverse osmosis.
At reverse osmosis water and the microelements dissolved in it are separated at the level of molecules. On the one hand from semipermeable membrane very clear water concentrates, and substances polluting liquid remain on the other hand. Openings in membrane are very small therefore they through them can pass only water molecules. The reverse osmosis guarantees such large-scale of cleaning which cannot be reached by methods of filtration of mechanical particles and adsorptions by means of activated carbon.
Conditions on which the efficiency of reverse osmosis depends:
- pressure;
- temperature;
- acidity level;
- material of which the membrane is made;
- chemical composition of initial water.
Most effectively inorganic substances separate in the course of reverse osmosis. For the best types of membranes the extent of cleaning of such substances makes 90-98%. However membranes not bad cope also with organic matters. As viruses and bacteria have the considerable sizes, their penetration through membrane elements is excluded. And here the oxygen dissolved in water and some gases defining taste of water, membrane passes.
In reality the best membrane cannot detain all foreign substances dissolved in water. In it is insignificant small quantities they get through obstacle. The quality of cleaning can be improved at the expense of rise of pressure on entrance.
As a result of purification of liquid the concentration of salts at the entrance grows that leads to pollution of membrane. At impact on membrane of large foreign suspensions the small time also gets littered. To prevent this undesirable phenomenon, along membrane create compulsory water current which washes away salts in drainage system.
To avoid membrane exit out of operation, turn on several complementary filters in which liquid has certain training for the finishing cleaning in system.
At the first stage water from external source is pumped on primary filters. After that there is process of reverse osmosis. The purified liquid comes to the special accumulative tank, and concentrate which contains the filtered particles, goes to the sewerage. Purified water via the extra is pumped on the crane with clear water.
The system of filters and membrane should be replaced from time to time. To define that these elements of system of cleaning need replacement, it is possible by means of the special electronic instrument measuring the level of salts in liquid. If the amount of impurity in water exceeds 20 mg/l, it is recommended to replace membrane.
Membrane – the most expensive element of system of cleaning. On the design it represents material with very small time which is twisted in several layers around the plastic element having perforation. By means of mating rings to membrane the protective cover fastens. Arriving in membrane, water passes through filler, and here pollution cannot break this barrier. Salts and other foreign inclusions are removed since the opposite end of the membrane block and transferred to utilization.
Usually the membrane is changed time in two-three years. This term is defined by the following factors:
- pressure in water supply;
- number of pollution;
- temperature of the purified water.
There are cases when the membrane serves up to five years; sometimes it should be changed in year of the strengthened operation. Use of mechanical and charcoal filters of preliminary cleaning gives the chance to raise membrane life cycle. Coal and mechanical filters in the system of reverse osmosis demand replacement approximately in half a year.
In general cleaning level by means of the system of reverse osmosis brings closer water to distilled. To improve taste of purified water, it is in addition passed sometimes through mineralizer or the bioceramic cartridge, useful image changing structure of water. However water is completely suitable for consumption and after passing through membrane. To boil it for drink there is no need.
Till some time of system of reverse osmosis were applied only in the industry, in improving institutions, at catering establishments. The growing requirements to quality of potable water have made reverse osmosis popular way of water treatment and in life.