The Orchid Garden

Reverse Osmosis water and Orchids; aquarium water

Question:

[This article has a rather bizarre crossposting, although it's actually relevant to all groups concerned. Should you choose to follow-up this article you will need to set the newsgroups line manually to the appropriate group(s)] Ed asked this question on the orchids mailing list (which from where I sit has 10X the volume of rec.gardens.orchids) so as well as responding to it there I’m sticking it in rec.gardens.orchids. Rec.gardens and rec.arts.bonsai are getting it because of the use of dirst aquarium water as a fertilizer which people may not know about, the aquaria groups are getting it for the same reason. – Hide quoted text — Show quoted text – Regarding Misting and Reverse Osmosis Water To the Assembled Brain Trust, Does anyone have any experience or thoughts on using Reverse Osmosis Water in a misting system.  (Reverse Osmosis is a filter system that yields something on the order of 99% pure water)  Aside from reduced wear on the nozzles, I would expect less hard water deposits on the plants. Thanks Ed Los Angeles

I have plenty of experience using reverse osmosis water in Los Angeles! When I lived there (3 years ago, for 10 years) I used to keep and breed killifish, a rather specialized (and very pretty) group of tropical fish. Some of them are rather demanding, and many killi hobbyists have home Reverse Osmosis setups. A reverse osmosis filter works by passing water, under pressure, through a membrane. Somehow this removes a large number of things in the water, like calcium, magnesium, lead, PCB’s etc. It does not remove chlorine/chloramine, although many people who don’t know any better will tell you it will. How much “stuff” is removed from the water by an RO filter is a function of how tigtly the membrane is wrapped around the core, the tighter it’s wrapped, the purer the water, but the less water you get. For every gallon of RO water, it dumps about 9 gallons of “liquid rock (LA Tap)” down the waste water return. If the membrane is wrapped less tightly around the core you get a higher rate of water but it’s not as pure. Of intererest to killifans is the calcium and magnesium that make tapwater (especially LA tapwater) so hard. Out of the tap it’s around 800 ppm. My membrane was wound fairly loosly, and I got about 15 gallons per day of 50 – 100 ppm water. This suited me fine, as, if if came out really pure (10 ppm) I’d need to cut it with tapwater because water that pure has no buffering ability and can take quick and drastic pH shifts. I did keep orchids when I was in LA – just a few, I was not very serious about them – and I watered them with waste auarium water, which all plants seem to love – the dirtier the better We used to hve friends who would come over once a week with 4 5 gal continers to take home some really dirty aquarium water for fertilizer for their vegetable garden. They did a little test and had better results with aquarium water than with chemical fertilizers, anyway, I digress. RO filters are vailable in rates from 5 gal per day to units than run car washes. Good ones will have a polyester prefilter to capture bit’s of rust and other sediment, and a carbon postfilter to remove the aforementioend chlorine and chloramine. Models sold as drinking water oftern have a bladder storage tank, whereas models sold for fish/plants usually just drain into a bucket. In the Los Angeles area (Glendale, I believe) there is a fellow, Ron Harlan who runs “Back to Nature Filtraton” who sells RO units specifically for plants and fish. Ron is (was ? it’s been years since I spoke with him) head of the biology department at Glendale city college. He really knows his stuff. I just called to verify his number and discovered he’s “doing inventory” (which probably means he’s off collecting fish in Peru or Argentina) and will be closed between June 6 and June 29. The recording mentioned that if you mentioned the recording you’d get 10% off. Kinda wierd but usefull I suppose. Anyway, he comes highly reccomended. When I sed RO water I has zero zip none no da nada white spots on the plants from carbonate hardness. Now that I’m in toronto and although the tapwater is only about 350 ppm I DO get white spots on the plants, espeacially on the Bromeliads, which get a “ring around the cup”. — Richard J. Sexton                Masonic order of the MANGO/Gryphon Gang North

Response:

A reverse osmosis filter works by passing water, under pressure, through a membrane. Somehow this removes a large number of things in the water, like calcium, magnesium, lead, PCB’s etc. It does not remove chlorine/chloramine, although many people who don’t know any better will tell you it will.

It is important to remember that ther eare 2 different types of R/O membranes.  One is TFC, the other is CTA. TFC is intolerant of chlorine and will be damaged by the typical chlor(am)inated municipal water.  It is recommended for use with well water supplies. The "C" in "CTA" stands for "cellulose".  This kind of filter does not break down when exposed to chlorine.  Instead, it *requires* chlorine to be present in the source water.  Chlorine kills bacteria that would otherwise grow on the membrane and would destroy the cellulose.  CTA membranes are recommended for the usual chlorinated municipal water supplies.  CTA’s rejection of chlorine is somewhere around 50% (compare that to 95-98% rejection for most other interesting chemicals, and ~90% for ammonium). A carbon postfilter will easily take care of the residual chlorine levels. How much “stuff” is removed from the water by an RO filter is a function of how tigtly the membrane is wrapped around the core, the tighter it’s wrapped, the purer the water, but the less water you get.

Water pressure matters as well.  The higher the pressure, the better the unit prforms, including more gallons of R/O product per day and a better rejection rate. For every gallon of RO water, it dumps about 9 gallons of “liquid rock (LA Tap)” down the waste water return. If the membrane is

The more recent filters (like the ones sold by Ron Harlan) reject 5 gal of water for every 1 gal of R/O product.  Ron also sells "water conservation valves" which are said to improve the reject/product ratio to 3 to 1. Ron Harlan who runs “Back to Nature Filtraton” who sells RO units specifically for plants and fish. Ron is (was ? it’s been years

By the way, I learned all these things from the literature that accompanies ROn’s filters.  See, unlike Sexton, who got his unit from some consumer/retail outlet, I got my R/O unit from Ron. — Oleg Kiselev at home                    …use the header to find the path

Response:

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