[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Live Foods Digest V2 #108



Toan Tran wrote:
> 
> Date: Tue, 07 Apr 1998 19:55:39 -0700
> From: "Toan T." <RiceGuy at stones_com>
> Subject: hard water / peat substrates
> 
> What possible methods are there to reduce water hardness?
> I know two; deionization and reverse osmosis. are there
> any other ways of reducing hardness?

Probably the most simple one is ion exchange used in most household
water softeners, which are regenerated with salt, NaCl. The water is
soft, but NOT deionized.

Another method, if you have HIGH hardness, say over 350 ppm, is to let
it just stand for a week or so & you will see CaCO3 precipitating. The
first time you use a container, it precipitates quite slow, but once you
have some deposit of solid calcium carbonate on the bottom, it goes
faster. It will soften the water somewhat, depending on exact
conditions.

Another method, probably the cheapest, and the one used by municipal
water works, is quantitative addition of "hydrated lime" - calcium
hydroxide (I know, it does not seem to make sense but, trust me, it
works!). The trouble with this method is the term "quantitative
addition". If you add too much  hardness goes back up! Using this
method it is POSSIBLE to reduce hardness to about 20 ppm - very, very
soft! 

> I'm still very confused on the subject of water hardness -- the scales,

You are right to be confused! The situation, most of it caused by one
publisher of aquarium literature, is a mess, to put it mildly.

In order to understand the problem, one has to go a little bit back in
history:

In the "good old days", before WW I, practically each industrialized
country had its own units to measure water hardness. We had German (dH),
British (degree Clark), American (DH or "points"), French (Degre
Hydrotimetrique), etc. scale of hardness. After WW II only the German
degree of hardness was left in wide use. All the other countries changed
over to the "scientific" units, i.e ppm (parts-per-million) of CaCO3,
(except the water-softener industry in the US, but I have seen them use
both Units). On the "scientific" scale 1 ppm = 1 milligram CaCO3 per
Liter (mg/L).

So far, so good. After WW II there appeared translations of several
German books on breeding tropical fish. Unfortunately, the translators
"were at sea" concerning water hardness and confused "degree dH" (Grad
deutscher Haerte) with the American "DH" (degree of hardness), sometimes
using them interchangeably. In practice it did not matter much, because
the difference between both scales is only 5%, but it set in motion a
confusion that lasts to this day!

I could go on & on, but will spare you the gory details. Suffice it to
say, that 1 dH = 17.85 ppm & 1 DH = 17.12 ppm CaCO3. Also, I will not
bore you with milliequivalents/Liter & other sundry things, just add,
that for water hardness purposed (it simplifies calculations & doesn'y
matter industrially) magnesium content is handled as if it were calcium,
i.e. we assume that all the hardness derives from the calcium ions.

> the types of hardness -- despite my efforts to understand it.

Water hardness is traditionally divided into "permanent" and "temporary"
hardness. This nomenclature is due to the fact, that boiling any water
will rid it of "temporary" hardness. 

Components of temporary hardness are the carbonates and bicarbonates of
calcium and magnesium, which precipitate upon boiling (boiler stone!),
making the water softer. 

Permanent hardness is comprised of other salts of calcium, magnesium,
iron and aluminum. The last two components seldom are in high enough
concentration to add much to the hardness.
> 
> I recently read that the addition of peat would render
> the chart many people use to determine CO2 concentration
> by measuring water hardness and pH to be inaccurate. This
> makes sense, because peat moss only lowers pH and not
> water hardness... doesn't it?
> 
I have read, that peat can act as an ion exchange medium. If that is
correct, then it CAN soften water - but how efficient?

Re interference of peat-treated water in measuring CO2 - it probably
depends on the method. The method Im am familiar with is titration. Peat
extract WILL interfere with it!

Does what I wrote make sense to you? If not, write to me!

Best,

George