Pure Water Filters – How Pure Is Reverse Osmosis?
When it comes to water filtration, there are so many myths regarding carbon and reverse osmosis filtration that it’s difficult to separate fact from fiction. It’s very much like how to bring up a child, every parent will have their 2 cents worth, if not more. What I’ve done in this post is try to go back to basics and give you some foundation knowledge about how best to produce pure drinking water in your house or office.
About Carbon Filtration
Firstly, a note about carbon filters. Carbon filtration does not remove dissolved metals, fluoride and a few other things so I don’t regard them as “pure water filters”. They do a great job removing chlorine and various other toxic substances from our water but on their own they do not produce pure water. If you’re on a budget but still want to provide some form of filtration, then I would recommend a carbon filter (normally coupled with a sediment filter).
About Pure Water Filters
In my opinion, there are only two methods of producing pure water in the home and office environment – distillation and reverse osmosis filtration. Distillation is a far more expensive proposition than reverse osmosis and hence is not considered a practical option. The fact that you don’t find distillation kits in hardware and home appliance stores is proof of this. The time, energy and capital cost involved with distillation makes it a less than attractive option for the household and office environment.
This leaves reverse osmosis filtration as the only practical home and office drinking water solution.
About Reverse Osmosis Filtration Systems
Reverse osmosis works by using high air pressure to force water through a semi-permeable reverse osmosis membrane. When the contaminated water is forced against the membrane, its pores are small enough to reject even the tiniest of contaminates but allows the water molecules to pass through. If all that sounds too complicated, think of it as a filter that has tiny pores that can filter out even microscopic things we can’t see such as virus and bacteria.
It should be noted that reverse osmosis is almost always used in conjunction with sediment and carbon filtration. Reverse osmosis on its own is rather impractical as larger sediments, iron and calcium in the water will quickly deteriorate and clog the membrane requiring it to be changed frequently (too frequently for practical applications). A typical “reverse osmosis system” usually includes:
- Sediment Filter – remove larger sediments such as dust, dirt, sand, rust and other particulates.
- Carbon Filter – removes chlorine and volatile organic compounds (eg, paint solvents, petrol, BBQ lighter fluid, etc). Chlorine is added into our water by the water authorities to disinfect public water, whilst VOC can enter our tap water from petrol and oil spillages (we’ve seen a fair few of them in the last few years) seeping into our underground water. It’s not uncommon to have two or three stages of carbon filtration in a reverse osmosis system.
- Reverse Osmosis – this usually occurs towards the end of the overall filtration process, reverse osmosis removes dissolves salts (Australia has a particularly bad salinity problem in our soil and water), dissolved metals (lead, copper, mercury, chromium, aluminum, etc) and just about anything else through its ultra-fine pores.
How Fine Are Pores In A Reverse Osmosis Membrane?
The pores within a reverse osmosis membrane is so fine that it rejects practically any particles, yet large enough to allow water molecules to pass through. Most membranes have an effective pore size of approximately 1-10 nanometers which makes it small enough to remove dissolved salts, dissolved metals, fluoride, viruses, bacteria and nearly anything else one would think of as contaminants in drinking water.
This is a rather incredible thing don’t you think? Share your thoughts by leaving a comment below.
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