Talk:Reverse osmosis

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Needs description[edit]

I am not a biologist, can anyone give a good description of what Reverse Osmosis is on the top of the article? it also needs to be wikified.. -- Rotem Dan 10:40 Apr 14, 2003 (UTC)

its a pity when they cant speak plain english eh? what it says is the membrane works like a sieve... its really just like any filter but it is a sheet with tiny holes in it that only allow the water to pass through... i think people need to make it sound complicated to try to justify the money the industry is making off of it... i pay $1 a gallon for it... gas is about $2 milk $2... so i guess like i said they want to make it sound like high tech water so they can justify making you pay for it.. or what ever — Preceding unsigned comment added by Majorheadrush (talkcontribs) 21:22, 19 March 2017 (UTC)

I think we are all looking at this page through the random page lottery. But that will not stop me from mentioning than I am unaware what "osmoisis" is "osmosis" I do know.
The article is informative, but not to the point. Cimon avaro 10:53 Apr 14, 2003 (UTC)

Needs History Section[edit]

This article could use a History section. IIRC it's not that old of a technology.

San Diego does not currently recycle waste water back to tap water. I removed the erroneous entry about this. It has been proposed, but was rejected several years ago. The city has conducted a recent study, and the proposal is up for review by a city council committee. Mayor Jerry Sanders opposes the proposal. I find the Los Angeles statement highly suspect in light of this, but I'll leave it to a Los Angeles resident to research. News article: [1]

Dennis Chancelor did not "invent the Reverse osmosis processor" so I removed the reference. This was a very suspect statement supported only by a local newspaper interview with the supposed inventor. A US patent database search show no US patents with an inventor named Chancelor, while in contrast there are 461 US patents with "reverse osmosis system" in the claims section. These go back to 1976. Further - his name shows up nowhere in the scientific literature. I personally was building RO systems in 1970, I worked on developing the technology and several dozen products, systems and applications, from 1970 to 2005, and never heard of this person. Several of the RO commercial founders (Don Bray, Dean Spatz, J. Riley) and the early academics (S, Sourirajan, Merten, Lonsdale etc) are a few of the dozen or so people who could make some type of claim like this - although they would not because once Sourirajan invented it and GulfAtomic corporation developed it under early federal grants, R0 technology was developed in a very widespread and colloborative manner. 65.29.7.173 21:08, 6 July 2006 (UTC)David Paulson65.29.7.173 21:08, 6 July 2006 (UTC)


Reverse osmoisis should be merged, this also should be checked for copyright violation (I will google it..) Rotem Dan 17:41 Apr 1:: Reverse osmosis (stub which is linked by Osmosis) and the misspelled 4, 2003 (UTC)

Osmosis ...reverse osmosis comes from the process of osmosis, the natural movement of solvent from an area..., in my understanding, is imprecise. Osmosis is the movement of water only not just any solvent - anything else is diffusion. 208.114.132.151 02:16, 22 August 2006 (UTC)


This is a copyright violation, I am blanking this article. see [2] Rotem Dan 17:46 Apr 14, 2003 (UTC)

Umm, I wrote this stub off the top of my head. These are my own words, and anyone else has used the same words it's probably coincidence. Mkweise 04:27 Apr 17, 2003 (UTC)

Wet Oxidation section is irrelevant[edit]

and needs to be removed. This article is about reverse osmosis, not water purification. Unless someone objects, I'd like to move wet oxidation to it's own article. Johnathlon 01:10, 28 July 2005 (UTC)


Just for your knowledge, Glaceau Vitamin Water uses the reverse osmosis water. In all the nutrient enhanced water beverages.63.87.161.130 (talk) 18:53, 26 March 2008 (UTC)

unanswered issues[edit]

While I'm not qualified to add the info, I'd like to see a little bit more detail regarding the efficiency of RO systems and the water costs involved (my understanding is that RO uses a large quantity of source water to 'produce' a small qty of clean water)..


Addition to note on RO design 1: the RO membrane are size to recover only 15% permeate per "membrane unit" that is correct but it also can connect to series and do water recycling to mark up the flow rate and yield overall water recovery of 70-80%. Recovery rate must be design according to the inlet salinity and Silt density ie. from sea water then the overall recovery will be only 10% for the whole unit while 70-80% recovery can be produce from average ground water. I believe the statement that the disadvantage on small water recovery of 15% for household membrane may not be accurate. It could obtain a lot more information especially on design criteria from membrane maker.

Addition to note on RO design 2: If there is anything disadvantage on RO I would say the maintenance cost. For Ion exchanger the running cost is direct varies with water quality and less maintenance cost but for RO the running cost is low but with high maintenance cost. At high productivity of demin water the RO show advantage but if it is low productivity then the Ion exchanger become more favorable.

Addition to note on RO design 3: Regard waste water... It can't state that waste water from RO is actually more than Ion exchanger because the waste water from RO can easily pass as municipal waste water but for DI, it had high TDS and require neutralization and dilution which make overall waste water in similar figure. —Preceding unsigned comment added by 203.147.18.37 (talk) 02:03, 8 October 2009 (UTC)

I can't find any information on the types of membrane materials typically used, neither directly in the article nor through links. This is a very significant deficit since they are the essence of the the technology! — Preceding unsigned comment added by 150.227.15.253 (talk) 09:20, 25 May 2011 (UTC)

Based on size of pores, particles that can and can not pass through can be discussed here. Ashishfa (talk) 14:24, 26 February 2016 (UTC)

Drinking Water Purification[edit]

i find the latter half of the section, the part with all the citation needed marks, irrelevant to the article. I suggest it either be placed under its own article (Reverse Osmosis and it's effects??) or deleted completely. My motion's on the latter.--Psydude 16:07, 2 June 2006 (UTC)


are you kidding?!!! the only thing you can really apply reverse osmosis to in the REAL WORLD is desolination and water purification, take it from a wastewater treatment civil engineer, leave those sections IN!


Removed some criticism[edit]

Removed:

RO water used for drinking, generally has a post carbon filter for taste. RO water has a flat taste that most do not like.[citation needed] Therefore the post carbon filter, (usually walnut shells or coconut shell) gives the RO water back its 'normal' flavour.

This is not true - activated carbon does not "give back normal flavor" and it is usually washed and otherwise purified to avoid adding any extracttables. Water "tastes flat" once purified due to the same osmotic effect described earlier - an interaction with the fluid in the cells- taste bud cells in this case. small amounts of salts are added back to improve taste - an example ois Dasani bottled water. 65.29.7.173 15:32, 4 July 2006 (UTC)David Paulson65.29.7.173 15:32, 4 July 2006 (UTC)

Reverse Osmosis is generally 'oversold' as a system. In other words it is NOT as effective in removing contaminants as people are led to believe[citation needed]. It does not remove all contaminants nor does it remove all bacteria. Without pre-treatment for example it does not remove both forms of arsenic. Reverse Osmosis consists of one membrane in a multi-stage treatment process. It should be used only in situations where no other treatment options exist, such as with high salinity or high total dissolved solids. RO water will be acidic and 'aggressive'[citation needed]. Thus it is NOT optimum from a human health perspective.

This sounds like the addition of somebody with an axe to grind. Even if it's reinserted once citations are supplied, it will need considerable work for neutrality. --Robert Merkel 04:19, 2 July 2006 (UTC)


regarding the comments on ro being oversold and the deletion: some of these statements are common facts among ro users: ro does not remove bacteria; before going thru an ro membrane water must be pre-treated. would such comments need citations? as for neutrality, the ph level of the comments may need to be tested - ro isn't for everyone and i have one. in addition, the section on the effects of chlorine on the 2 types of ro membranes seems to state that chlorine damages both types but i am a little confused. you've deleted some important information - someone might like to be tipped off that they may need to buy a water softener and 3 or 4 filters and an electric pump to use a small under the sink reverse osmosis unit to supply the water for their refrigerator dispenser and ice maker. jm —Preceding unsigned comment added by 68.56.32.239 (talk) 23:00, 23 October 2009 (UTC)

Gravity powered reverse osmosis?[edit]

"Portable reverse osmosis (RO) water processors are sold for personal water purification in the home. These units are gravity powered (they need no water pump), and need no electricity"

I'm not aware of any gravity powered reverse osmosis system, especially not sold for home use. It's my understanding that a significant pressure is required, more than gravity could supply. I think whoever put this in was confused because most under-sink reverse osmosis systems require no pump or electricity, because there is already enough pressure in the municipal water supply. That is very different than gravity powered, which would be something like a Brita pitcher. If portable, gravity powered reverse osmosis systems were possible, I'm pretty sure they would be sold to the outdoor and marine survival markets. Currently, the desalinator included on some high end life rafts and on some boats is a hand powered device that produces about a liter an hour, with a lot of effort. --24.24.80.35 13:25, 16 July 2006 (UTC)

To elaborate on the pressure requirements for Reverse Osmosis, typical large scale osmosis units operate at 150 to 500 psi (Lindeburg, 1990). The static head of water (height required for gravity flow) required to operate in that range would be 346 ft to 1,150 ft, respectively. House hold taps are usually less than 100 psi, but for smaller systems this pressure may suffice. The range of pressure is due to the fact that pressure must be constantly increased to maintain a constant yield. The increased pressure is to compensate for the effects of fouling and compaction. ~Gerald B.

external links[edit]

I removed the CAI Technologies link as the 'how to choose a system' link. If people want to add suppliers as external links I think that's fine, but identify them as such. CAI is not independent any more than Watts Premier is.208.114.132.151 01:12, 22 August 2006 (UTC)


Difference from filtration?[edit]

Until I read the entry, I was sure that RO was just a marketing term for filtration. It sounds better to say that the water is RO vs. just filtered. Does filtration not apply to removal of solute? Is RO a subset, superset, or alternative compared to filtration? Thanks!

RO is not filtration.[edit]

The "Salt Ions" (as the sodium and chlorine ions are referred to in this article) have diameters on the order of 2.40 and 3.40 pm, respectively (diameters, not radii). The water molecule itself has a diameter of about 1.5 Angstroms, smaller than the diameter of either of the ions that are being "filtered out." I do not understand the mechanism well enough to explain it to you or rewrite the article, but it is clear from their relative sizes (as given by wikipedia) that filtration is not at work in the macroscopic sense, and that this is not made abundantly clear in the article (which it should be.) See also "RO Models and Structure," BelowJuneappal (talk) 06:47, 9 February 2009 (UTC)

RO models and structure[edit]

It's interesting that much credit (well-deserved) is given to Loeb and Sourirajan, and yet the page states that RO membranes have no pores, a point I suspect they would disagree with given Sourirajan's development and furtherance of membrane pore models such as the Preferential Sorption-Capillary Flow Model. Perhaps this statement could be replaced with a statement such as:

The membranes used for reverse osmosis have a dense polymer barrier layer in which separaton takes place (current theory indicates transport is by diffusion through the barrier layer, known as the solution-diffusion, or through preferrential sorption pore or channel flow). —The preceding unsigned comment was added by 66.83.180.10 (talk) 20:04, 5 December 2006 (UTC).

reverse osmosis to reduce hardness of d.m water[edit]

can the process of reverse osmosis helps to reduce the hardness or Chloride contents of D.M water for Boiler ? also whether it is useful if the intake water is highly contaminated by high sewage mix-up ? what will be the impact on processing cost compared to normal water treatment? —The preceding unsigned comment was added by Anilbapatnasik (talkcontribs) 09:16, 16 February 2007 (UTC).

Energy consumption[edit]

I miss in the whole article the energy consumption

New systems with pressure recovery are at 2.5 kWh electric power / m³.

Here a desalination cost calulator

When it comes to the task to reduce carbon dioxide to a level before using fossile energy, desalination for irrigation dry areas could be a key technology.

--Pege.founder (talk) 13:56, 2 March 2008 (UTC)

Info lacking: Effectiveness at removing pharmaceuticals?[edit]

I have zero prior knowledge about RO or other water purification methods. Came to the Wikipedia RO article after reading an Associated Press article about pharmaceuticals in the water supply. (see: http://news.yahoo.com/s/ap/20080309/ap_on_re_us/pharmawater_i). In the AP article it is claimed that RO, alone amongst household water purification methods, removes pharmaceuticals.

I suggest that an excellent addition to this Wikipedia RO article would be, discussion of the effectiveness of RO at removing pharmaceuticals. i.e. 100% for any/all; vs. less than 100%; vs. not really fully researched or understood yet from an engineering/chemistry perspective; or whatever the actual situation may be.

Thanks in advance to anyone with the wherewithal to add this kind of information. Publius3 (talk) 21:07, 9 March 2008 (UTC)

Image[edit]

Can this article have some diagram or illustrative image? I like pretty pictures, not to read much text. -- Frap (talk) 10:51, 11 August 2008 (UTC)

I had added a very informative animation which displayed in detail a reverse osmosis membrane in action as well as comparing reverse osmosis to ultrafiltration, nanofiltration and microfiltration. It had been on the site for weeks. Unfortunately for most Wikipedia users researching reverse osmosis will now not find this animation because a few sour users feel the external link is commercial spam.
Rather than attempt to gain consensus to add a link that is likely in violation of the external link guidelines you have continued to simply revert the link as well as reverting removal of other commercial links in the page. TastyPoutine talk (if you dare) 06:01, 24 June 2009 (UTC)
You write the link is "likely" in violation of the external link guidelines. <- None of the 18 "links normally to be avoided" apply. It is not in violation because the linked page is informative, useful, and factual. The link satisfied the reverse osmosis diagram/illustrative request. Did you read the request? "I like pretty pictures, not to read much text." Without the link useful and educational visual information has been removed from this Wikipedia article. Thank yourselves TastyPoutine, Ronz, and Velela for removing a very topic-relevant learning tool. How does one go about getting a consensus to re-add this link? * www.wetterwater.com/reverse-osmosis-education/reverse-osmosis-technology.html#animation Thank you for your consideration, Slimserver
I've been doing some work with Dow Water and finally understand how RO works. The diagrams on this article do not, IMO, explain RO concisely or sufficiently. Dow has a published RO manual (pdf) that has a great simple diagram and explanation on page 10, fig 1.4. As it is copyrighted material, we can't copy it verbatim. Is there a way to incorporate its usefulness? Pettijohn (talk) 14:35, 4 November 2010 (UTC)


Text can be paraphrased and referenced. Images can be redrawn, and referenced. If Dow releases these images, that works too, but that might not be worth the effort. --Rifleman 82 (talk) 15:21, 4 November 2010 (UTC)

Shorter Intro[edit]

The intro paragraph should be a lot shorter and if possible less technical. Epl18 (talk) 19:25, 13 September 2008 (UTC)

Seconded. The second half of the intro reads like an awkward retelling of the first half, with out providing any additional information. Ekozlenko (talk) 19:33, 22 November 2008 (UTC)

Efficiency etc.[edit]

I think some discussion of efficiency would be very helpful (and I note the comment above re energy consumption).

In specific regard to efficiency of small-scale (household, and I assume, therefore, cheap?) systems, I do not understand this sentence: "Household Reverse osmosis units use a lot of water because they have low back pressure." Or rather, I don't understand what the sentence is trying to convey. —Preceding unsigned comment added by 70.66.64.230 (talk) 23:51, 1 September 2009 (UTC)

Senseless Sentence[edit]

The article states "They come ranging from 1500 GPD (gallons per day) to 150,000 GPD and bigger depending on the need." If there are units that qualify as "and bigger" than 150,000 gallons per day, then it does not make sense to say "from 1,500 gallons per day to 150,000 gallons per day." --Desertphile (talk) 01:23, 20 September 2009 (UTC)


I edited the "process" section of the article by removing the description of what osmosis is from the beginning of it. If people don't have enough knowledge about osmosis to understand reverse osmosis, then they could look it up. It is not necessary to discuss it in this article. ~~ —Preceding unsigned comment added by 76.217.12.210 (talk) 08:22, 29 April 2011 (UTC)


"Areas that have either no or limited surface water or groundwater may choose to desalinate" is nonsense. Areas don't make choices. — Preceding unsigned comment added by 80.5.252.34 (talk) 07:32, 3 July 2014 (UTC)

Disadvantages[edit]

In the disadvantages section, this article states "Reverse Osmosis water is, in fact, so chemically unstable and acidic that in many countries national plumbing codes restrict water that has been filtered via reverse osmosis from being reintroduced into copper pipes due to its corrosiveness on the copper. This also has implications for reverse osmosis filtration systems that use steel storage tanks, as the acidity of the water can lead to the steel rusting over time and contaminating the post-filter water." Acidic is incorrect here. The water should be neutral, or somewhere in the vicinity of neutral, depending on the temperature. The water would be more corrosive, as it would strip/leach metals as it passes through the piping (be it steel or copper). This is due to the fact that the metals are slightly soluble in water, and normally the water is saturated, or nearly saturated with these solutes. With RO water, it is completely devoid of contaminants. As it passes through the piping, it will strip/leach whatever it can, at a relatively rapid rate. Woahmid (talk) 18:42, 27 February 2012 (UTC)

Define Solvent[edit]

Why does the article use the word solvent as if it's something other than water? Isn't the very reason that water makes up so much of our bodies- between 50 to nearly 80 percent- because it makes an excellent solvent? Or do I just need to read further into my book on anatomy and physiology? Because it calls water a solvent in chapter 3. — Preceding unsigned comment added by Thetrellan (talkcontribs) 03:06, 14 June 2012 (UTC)


"Reverse osmosis is in the final category of membrane filtration, "hyperfiltration", and removes particles larger than 0.1 nm."

This needs to go. To quote Wolfgang Pauli, "Not only is it not right, it's not even wrong!" You can't talk about particles at the Angstrom (0.1 nm) level - quantum mechanics kicks in here in a big way. As pointed out elsewhere this isn't filtration, but a chemical/statistical mechanics force/pressure. — Preceding unsigned comment added by Waveman68 (talkcontribs) 18:27, 29 August 2012 (UTC)

"Reverse osmosis is in the final category of membrane filtration, "hyperfiltration", and removes particles larger than 0.1 nm."

This whole paragraph should be checked for accuracy. Since 0.1 nm = 1 angstrom and the diameter of a water molecule is approximately 1.5 anstroms then the "hyperfiltration" reverse osmosis membrane should reject the passage of water molecules and so reverse osmosis could not occur. Since reverse osmosis does work, this statement can not possibly be correct. — Preceding unsigned comment added by 69.120.111.106 (talk) 04:27, 24 November 2013 (UTC)

Why do you have to purge the replacement RO filter for twenty-four hours?[edit]

Any body know why this is recommended by the filter Mfg. They say to replace the rO filter and let the water run for 24 hours, and Do Not Drink the water during this time; why is it dangerous? — Preceding unsigned comment added by 24.176.238.174 (talk) 21:43, 31 January 2013 (UTC)

This article is incorrect in the concept of why RO rejects dissolved salt molecules[edit]

Reverse osmosis works by a diffusion mechanism and not a straining mechanism. There are no 'holes' in the membrane, so it works completely differently to processes such as sand filtration or even ultra filtration (which do work via straining through holes). To describe the mechanism in simple terms, RO works whereby the water molecules 'dissolve' into the membrane and then 'undissolve' out on the permeate side. Salt molecules do not 'dissolve' across the membrane as easily (but some do). This mechanism explains why some large organic molecules can cross the RO membrane more easily (since they are essentially non-polar and can dissolve into the membrane easier) than much smaller (and highly charged) salt molecules. It also explains why different RO membranes have different rejection rates for the same salt molecule, and why some small molecules more readily cross the membrane than others. To prove a point, take for example boron. At neutral pH's it exists mainly as a non-ionised species (boric acid) and membrane rejection rates are in the order of 50-75%. If the pH is increased to around 10 boric acid [B(OH)3] becomes a borate ion [B(OH)4-] and is negatively charged and rejection rates increase dramatically (>95%). Rejection increases because the ionised borate ion finds it harder to 'dissolve' into the (essentially) non-polar membrane. Note that RO membranes have a slight negative surface charge but on the whole are non-polar BluesLewis (talk) 12:19, 20 February 2013 (UTC)


Reverse Osmosis Filtered Type 1 And Type 2 Water Applications[edit]

For some reason the article doesn't specifically cover how RO water is produced in labs at different qualities. For instance type 1 water is RO water filtered once. Type 2 water, which is even purer, is RO water filtered through a second RO filter. Although Type 1 water and Type 2 water are a measure of how pure the water is, I think it should be mentioned that they can be made with RO filters. Also, someone who knows how to make new Wiki articles better than me should make a Wiki article stating what Type 1 and Type 2 water are.23.16.154.149 (talk) 13:12, 27 February 2013 (UTC)BeeCier

Ok, so I found some info on Type 1 (Type I) and Type 2 (Type II) water in the "Purified Water" Wiki article. I still think that it could be mentioned in the "Reverse Osmosis" article. Anyone? What say you?23.16.154.149 (talk) 13:26, 27 February 2013 (UTC)BeeCier

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Health risks from drinking demineralised water?[edit]

I'm not seeing how the information is actually supported by the references offered. Please quote from the references. (Additionally, WP:MEDRS and WP:FRINGE apply, but let's start by verification first.) --Ronz (talk) 16:05, 13 April 2014 (UTC)

I agree. At present the article presents a rather rosy picture of the use of water produced by reverse osmosis without any of the caveats that probably ought to be there. One of the refs produced at a very late stage by Esco83 eventually resolves back to this a commercial site reviewing what appears to be an unreleased WHO paper by F. Kozisek. The paper itself is both interesting and well balanced and does not contain the somewhat hysterical language used in recent edits to this article. The paper dated 2004 is marked a draft and not for citation. However it was finalised and published one year later here and this would be a very useful starting point for a section in the article. It is of course also pertinent to note that water supplied for drinking purposes is required to be potable in many (most ?) parts of the world, and to be potable it needs to be treated to ensure that those drinking it should be a negligible risk of harm to health. Thus if RO water is supplied for drinking it would need supplementary treatment to ensure the pH was satisfactory and that it contained appropriate mineralisation. This is already the case with naturally soft waters. Where I live, the concentrations of total minerals is less than 25mg/l and the pH of the raw water is often around 5.5. If it was supplied in this condition it would dissolve pipes and I would be a risk of toxic impacts from heavy metals in the plumbing. To avoid such problems the water is treated. The same would be true of RO water and I think we need to be very careful to distinguish between the quality of RO water as it is produced and the water that might be sold for human consumption that is derived from an RO process. The two are not the same.
What is more interesting to me is this ref that Esco83 posted on his/her talk page but didn't directly reference. Unfortunately it is a primary source and it would be useful to find a corresponding secondary source. The interest for me in particular is the ability of Boron, a powerful phytotoxin, to pass through RO membrane and cause toxic effects in crops irrigated with RO water. This is an issue far more intractable than low Mg in drinking water and it is a pity that Esco83 didn't make more considered edits and that we now have to wait three days to include him/her in the discussion.  Velella  Velella Talk   19:49, 13 April 2014 (UTC)

Membrane Fouling Statement Confusing[edit]

This sentence: "Up to 50% of the seawater input can be recovered as fresh water, though lower recoveries may reduce membrane fouling and energy consumption." appears to be incorrect. Was the author trying to say that membrane fouling causes lower recovery and higher energy consumption? As written, it says that one of the effects is the cause. Could someone with a background in this please read and correct? — Preceding unsigned comment added by 155.95.80.243 (talk) 19:45, 31 July 2015 (UTC)

Incorrect description of Normal Osmosis - Backwards[edit]

"In the normal osmosis process, the solvent naturally moves from an area of high solute concentration (high water potential), through a membrane, to an area of low solute concentration (low water potential)." This is exactly backwards. In a normal osmosis process, the solvent moves from lower solute concentration to higher concentration until equilibrium is reached. — Preceding unsigned comment added by 192.234.111.8 (talk) 19:49, 10 September 2015 (UTC)