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Old 10-06-2004, 04:08 PM
Helpful 1
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Default Micronutrients, truth, advice and reality RO & Boron


I am sorry, "Helpful 1," but your use of the efficacy of RO units
based upon the "Water Tiger" website is flawed, or at best,
over-simplified. (Forgive me, but I've joined Bert Pressman in his
quest to quash the dissemination of flawed or outright incorrect
orchid growing information.)

That is nice of you. I did not care of the website used, because the
small RO systems extraction tables are similar for all membrane

Granted, input water quality will effect the output quality of RO
water to some degree, but not sufficiently to be the difference
between "good" plants and "pretty ugly" ones, as the vast majority of
water supplies do not carry sufficient nutrients to adequately support
decent plant growth anyway, mandating that they be added via

It is not a major difference, usually, and RO water contains only
boron in quantities that may be important, technically speaking. Most
others ions or pollutants are removed. Boron has been touted as a
"dangerous" micronutrient. Furthermore, most of the fertilizers
developed for well/tap water ages ago have the same micronutrient
composition than today, using the latest water purification

Did you know that several major companies (such as Scotts) sell FOUR
different products for each of their fertilizers ?

Example with the popular 20-10-20 :
One USA,
the second "Florida special" ( with different levels of boron, amongst
One boron-free
and an EEC one, still different ? It is more or less like Coca Cola,
adapted to the customer's living place. Some mentions it, some others
do the correction and do not write down it, because they are within
the limits allowed by the country regulations.


I guess that you could be implying that in his old location there was
sufficient "boron breakthrough" that he did not need to supplement,
but doesn't that fly in the face of how an RO unit works?

There was definitely, a nice 1 ppm boron after the RO process.

RO, DI and ultrafiltration.

First, Ultrafiltration physically removes all ions, because of its
pore size. The membrane is very short lived usually.

DI removes positively and negatively charged ions. Incidentally, some
older systems do not remove organic contaminants at all, and need a
third cartridge, either charcoal or one of the more modern ones, to
provide really pure water. Boron as some of the borate ion usually has
trouble binding to the resins... it is well documented, and you can
find references with Google. Silicate ion are similar.

RO remove physically large ions and molecules, but let the water (H2O)
pass through.

The pore size would allow many ions to cross the membrane, but because
of an atomic electric phenomenon, a lot of ions can not pass through,
and are washed with the discarded water. Borate ion is small enough to
cross the membrane, and its electric load is very low.

Usually ion stay at the membrane surface because of electric
phenomenons at the atomic level, and are washed before they have a
chance to enter the membrane and pass through. It depends on the
quantity of water rejected.

You may make a simple test to realize that RO systems do not have a
membrane with pores small enough to purely physically block ions.
Block the waste water tube of a RO, wait a couple of minutes, and the
EC of the supposedly "pure" water will rise very shortly. Eventually,
if you wait a few hours, the EC of the "pure" water will be close to
the tap water EC... RO membranes electrically charge over use, and
after a few months, years or decades, depending on the ions involved,
become totally inefficient.

A part of boron and silicium compounds, because of their peculiar
electric behaviour, can pass through, because of their electronic

Think of RO membranes as a permanently flushed ion-repellent
structure, but not as a physical ion filter.

Rohm and Hass, the University of Rehovot, Israel, and Intel have
patents and published research on the boron and silicium problems
related to RO water. You may try google for more informations.

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