Operation
A pump presses the fluid through a membrane in the direction of flow reversed from that in osmosis. There are applications for the preparation of drinking water, including from seawater, production of boiler water for steam boilers and purification of some wastewaters and manure. By applying a pressure difference over a semi-permeable (semi-permeable ) membrane, this can act as a filter: the solvent will then move to the side where the sum of the external pressure and the osmotic pressure (= obsolete term for osmotic value) ) is the lowest. If the external pressure on the side of the concentrated solution is large enough, the pure solvent (without carrying the dissolved substances) will be pressed to the other side. In simple language, this means that water is pushed very hard right through a sieve with microscopic holes. The removal efficiency is not only determined by the size of the substances to be removed, but also by the polarity and the charge of the substances, the solvent, and the membrane.
Application
When the Industrial Ro plant is used as a purification method, this is also referred to as hyperfiltration, RO or OO. This method is used for, among other things:
· certain forms of kidney dialysis
· water purification to obtain very pure water
· large-scale drinking water production, including desalination
· point of use drinking water systems
· mobile drinking water purification systems, the Industrial Ro plant
· industrial applications, such as purification of boiler water from steam boilers in power stations
· wastewater treatment to be able to reuse wastewater
· make tap water suitable for aquariums for demanding fish
· make tap water suitable for special glasswashers and dishwashers
· removal of salts, micro contaminants, heavy metals, etc from water.
Combinations
Reverse osmosis is often preceded by prior steps such as conventional filtration to retain solids, an activated carbon filter to absorb chlorine and other volatile substances, or an ion exchanger. Reverse osmosis can happen in one step, or with two or more steps in succession. Reverse osmosis is sometimes followed by electrodialysis (EDI) for even higher purity.
Comparison
Reverse osmosis has the advantage over an ion exchanger that no chemicals such as salt or hydrochloric acid or sodium hydroxide are needed but as disadvantages higher electricity consumption for the pump, more wastewater, and more maintenance costs.
Reverse osmosis
Reverse osmosis or RO [Reverse Osmosis] uses a membrane for the removal of salts [ions] but also minuscule organic molecules. An RO system has two compartments:
· High pressure
· Low pressure
In the high-pressure compartment we find the liquid to be treated. The compartments are divided by a permeable membrane. The external pressure that is built up until it exceeds the osmotic pressure causes the solvent to move from the most concentrated solution to the least concentrated. This process is therefore controlled by external pressure so that the direction of the osmotic flow is different from that of osmosis: reverse osmosis. This provides a concentrated solution [concentrate] and a pure solution [permeate].
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