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Filtración de membrana: osmosis inversa

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Purpose

  • Separation of salts by concentration
  • Production of demineralised water

Principle

As with membrane filtration, during reverse osmosis water in which wastewater is passed through a semipermeable membrane by applying pressure. A reverse osmosis membrane doesn’t contain pores. Water and other neutrally loaded molecules migrate through the membrane by diffusion through the molecular structure. During reverse osmosis, the water flows in the opposite direction of the natural osmotic gradient, which is why the pressure is needed.

Reverse osmosis retains all dissolved organic molecules, viruses and nearly all salts. The quality of the treated effluent is nearly equivalent to demineralized water. A concentrate with a relatively high salt concentration is created as a byproduct.

Most of the time the membrane configuration consists of spirally wound polyamide membranes in standardized modules.
In order to protect the membranes the reverse osmosis modules are often preceded by other techniques such as sand filtration and / or ultra-filtration.

Scheme

Applications

Reverse osmosis is used to generate very pure water. Example are the production of drinking water, the production of demineralized water for industrial applications, wastewater treatment, the reuse of purifier wastewater,…

Example of realization

Two stage RO plant

Operational costs

Reverse osmosis is a pressure driven technology, which makes it relatively energy intensive. There is also a chemicals cost for the periodical maintenance cleaning of the membranes. Moreover, the membrane life is limited and thus the membranes have to be exchanged every 5 to 10 years.