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Reverse Osmosis

Reverse osmosis is a physical process in which the purified liquid is propelled at high pressure through a special membrane capturing any undesired substances. The membrane pore ranges from 0.001 to 0.0001 µm, which allows the elimination of even the smallest contaminants. Therefore, only the water molecules pass through the membrane under a great pressure. The result of reverse osmosis process is a pure liquid which has passed through the membrane and the waste solution intended for disposal. Purified water free of harmful substances can be further treated according to the specific application, e.g. remineralising, alkalizing etc.

Reverse osmosis technology has an efficiency up to 98% and it is capable to remove almost any undesirable substances:

  • mineral salts
  • sulphates
  • nitrates
  • nitrites
  • fluoride
  • chlorides
  • heavy metals
  • asbestos
  • arsenic
  • radon
  • bacteria and viruses
  • pharmaceuticals

The advantages of reverse osmosis

The advantages of reverse osmosis technology are not only energy savings in the process of water purification and process simplicity, but also the fact that there is no need of any chemicals that may degrade the fluid or change its properties.

The effectiveness of water purification by reverse osmosis is influenced by several factors:

Membrane quality
Different brands of reverse osmosis membranes have a different design, materials and quality. This has a significant effect on the result of water purification, because the lower quality membranes do not have to capture all pollutants and also have lowered resistance and durability.

Sufficient inlet pressure
Inlet pressure for the efficient reverse osmosis process has to be as high as possible with respect to the equipment design and the membrane type used. In standard applications the water pressure ranges between 2 and 6 bars.

The amount of contaminants in inlet water
The yield of the outlet water depends on the degree of inlet water comtamination and decreases with the increasing amount of dissolved solids. Generally there is a problem with iron, which tends to form crystals in the pores, which gradually reduce the membrane efficiency and thus the quality of outlet water. Similarly, higher amounts of manganese adversely affects the properties of the membrane. Silicon and calcium clog the membrane pores. This degradation of the membrane can be prevented either by pretreatment of the inlet water before the reverse osmosis unit, or simply by more frequent replacement of membranes.

Inlet water temperature
The quality of the purified water decreases with an increasing temperature of the inlet water above 30 °C and also with a decreasing the temperature below 5 °C. The optimal inlet water temperature is 25 ° C.

Inlet water optimal properties

  • The water temperature should be between 15 to 25 ° C, the upper limit is considered as ideal.
  • Inlet water pH for optimal results of reverse osmosis is limited to the range of 2 to 11.
  • The pressure depends on the individual circumstances and applications, ranging between 2 bar to 6 bar.
  • Maximum iron and manganese content is 0.15 mg/l, the higher concentration can damage the membrane.
  • Maximum active chlorine content is 0.1 mg/l.

Pretreatment of water before the reverse osmosis

As already mentioned, some of the substances e.g. iron may in higher concentrations cause the membrane damage or reduced filtration ability. Therefore, if the maximum limits are exceeded, inlet water has to be appropriately pretreated before it is processed through the reverse osmosis technology. Pre-treatment is carried out eg.:

  • iron removal
  • water softening
  • sand filtration of water
  • water dechlorination

Reverse osmosis utilization

Reverse osmosis finds a very wide range of applications in almost all types of the industrial processes, but also in homes, restaurants, aquariums and other areas. Examples of the reverse osmosis use:

  • water and sewage treatment
  • sea water treatment and desalination
  • purification and treatment of water from wells
  • pharmaceutical industries and laboratories (as a replacement of distillation)
  • dilution chemical and cosmetic agents
  • restaurants, bars and breweries
  • food industry
  • water treatment with a request for a salt content
  • water for replenishing the batteries in handling technology and cooling systems
  • domestic waste water and water management
  • water for air conditioning, humidifiers, heating systems, irons, ...
  • hydroponics and horticulture
  • aquariums
  • and many other examples of the effective use of reverse osmosis

Reverse osmosis removes all undesirable substances causing the unpleasant taste of water, so the outlet water has a completely natural taste and drinks produced from such a water will taste better. The taste of the outlet water is directly dependant on the inlet water quality and contaminant content.

Assuming the use of quality membranes, up to 98% of all pollutants normally found in contaminated water can be removed. By maintaining the optimal reverse osmosis conditions, only molecules of water permeate through the membrane, while all the other substances are separated as a waste.

Reverse osmosis currently belongs among the best worldwide used filtering technologies. It is not only highly effective and efficient, but also economic, environmentally friendly, and utilizable in almost all industrial plants and households. Our company BKG - úprava vody a.s. features experts in the reverse osmosis and all the other water treatment and purification technologies. With us, every customer gets a professional consultancy based on individual process requirements.

For industrial operations we design and imlement fully automatic reverse osmosis units, taking into account all aspects of the individual production processes, as well as economic impact and corporate regulations.

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