Safe Water at the Cottage: Reverse Osmosis - Part 2 of 3

What is Reverse Osmosis?
Reverse osmosis (R/O) is a water treatment process in which water is forced through a semi-permeable membrane that has very small holes or "pores". Clean water passes through and impurities that are too big to pass through the membrane are left behind and flushed away.

How does Reverse Osmosis Work?
Reverse osmosis systems purify water by forcing pressurized water through a very fine, plastic membrane. If the raw water being treated comes from a well or another private source, disinfection and pre-filters (to remove chlorine and/or particulates/sediment) may be needed in advance of the R/O unit to remove contaminants that can foul or damage the membrane.

Stages of reverse osmosis:

  1. During the initial filtration stage, tap water or well water (pressurized by a booster pump or pressure tank) is passed through a particle filter (a pre-filter) that removes silt, sediment, sand, and clay particles that might clog the R/O membrane.
  2. The water is then forced through an activated carbon filter that traps minerals and contaminants such as chromium, mercury, copper, chloramine and pesticides. It also removes chlorine, which is important, as chlorine will shorten the life of the membrane.
  3. Water is transferred under pressure into the R/O module, allowing only clean water to pass through the small pores in the membrane. Impurities unable to pass through the membrane are left behind and flushed down the drain.
  4. Treated water is then sent to a storage tank.
  5. Treated water is passed through an activated carbon filter before use to further improve the water's taste and smell.

Water that contains manganese, hydrogen sulphide or iron should be pre-treated to extend the life of the membrane. In fact the reverse osmosis package (system) that I purchased has 4 other filters to take out nasty stuff before it gets to the RO membrane.

Other URLs explaining Revers Osmosis:
How does Reverse Osmosis Work?
(this explanation is really great!)
Reverse Osmosis Water Treatment (From the CMHC website)

What chemicals do Reverse osmosis remove?

Coming Up:
In Part 3, I show and describe my RO system

Related Posts:
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