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Re: RO reconstruction

Mark Faulkner is looking for ways to increase his water's Alkalinity.

> I'm looking for a method to increase the KH of RO water to 4 to 7 deg.
> I have Kent's RO right (for trace elements, etc.), but it dosen't
> provide the buffering capacity needed for CO2 injection.  Are there any
> common methods (dolomite chips, aragonite)that give predictable
> results.  I'm new to the mailing list and I'm sure this topic has been
> covered in the past, so if there are previous discussions someone could
> point me to that would be great.  Thanks.

Yes, this subject has been covered in the past, but so have a lot of
others - don't sweat it. Here goes nothing...

According to a chemist who works for a major aquarium products company (and
who shall remain nameless), Kent's RO Right is merely a repackaged form of
Aquarium System's "Instant Ocean" salt mix. If he is correct, and his advice
to me usually is, it is capable of adding all the necessary ions and
electrolytes to recreate "typical" water values for RO water. Kent however,
is not very forthcoming when asked what they mean by "typical" - they just
gave me hype and confustion when I asked them about the subject last year.
Different lakes and rivers have different ratios of the various anions and
cations present, so I don't know where the term "typical" lies. Be that as
it may, RO Right is what I used for a few years to adjust the Total Hardness
of my RO water, and I had no problems with the product.

Now however, I use Seachem's Equilibrium, a product which leaves out the
Sodium and Chloride which can lead to problems in planted tanks if present
in excess amounts (and which is the major component in marine salt). Seachem
also provides a guaranteed analysis of their product which makes it
relatively easy to figure out how much of each ion is present in the
reconstituted water.

That takes care of the "GH" side, but Mark is quite correct in his thinking
that the Alkalinity of R/O produced water must be adjusted when CO2
injection is being contemplated. The easiest, and by far the cheapest way to
increase the Alkalinity of your water is to use common, everyday Baking Soda
(Sodium Bicarbonate: NaHCO3).

One teaspooon (approx. 6 g) of Baking Soda per 50 liters of water will
increase the Alkalinity by 4 degrees (per George Booth), without affecting
the Total Hardness at all. I prefer to think in terms of equivalents of
CaCO3 measured as mg/L, which is what my Hach Alkalinity kit is calibrated
in, but you are free to use whatever units you prefer and are comfortable
with.

Baking Soda will also raise the pH of the water, which if you are injecting
CO2 is a good thing (according to Martha Stewart anyway) as CO2 lowers the
pH. It is just a matter of balancing the amount of NaHCO3 used with the
amount of CO2 injected. Any good test kit for KH (which actually measures
Alkalinity) will allow you to figure out how much Baking Soda you need to
add to the quantity of water you use for your water changes to get the
proper Alkalinity level in your water.

Calcium Carbonate (CaCO3) would also work - but would also affect the Total
Hardness of the water. (Two teaspoons, approx. 4 g, of CaCO3 will increase
both the Total Hardness and the Alkalinity of 50 L of water by 4 degrees,
again according to George Booth.)

Hope this answers your question.

James Purchase
Toronto