Using potassium metabisulfite to remove chloramine?

Howdy good folk.

I am not currently an aquarium owner, but I have a question that you
should know something about. I make my own beer and I live in Oakland CA
where they use chloramine in the water. I purchased potassium
metabisulfite to remove the chloramine but I don't really know how much to
use. I have found references that widely vary but 500 to 700 mg per
20 gallons seems to be the best estimate I have found.

Since the life of your fish depend on proper water, I figure that you folk
may know better then the beer crowd about this issue.

So, what say you, how much should I use?

--
Doug Herr
doug*at*wombatz*dot*com

"Doug Herr" wrote in message
news

Howdy good folk.

I am not currently an aquarium owner, but I have a question that you
should know something about. I make my own beer and I live in Oakland
CA
where they use chloramine in the water. I purchased potassium
metabisulfite to remove the chloramine but I don't really know how much
to
use. I have found references that widely vary but 500 to 700 mg per
20 gallons seems to be the best estimate I have found.

Since the life of your fish depend on proper water, I figure that you
folk
may know better then the beer crowd about this issue.

So, what say you, how much should I use?

--
Doug Herr
doug*at*wombatz*dot*com

All I know about beer is that I like my draught lager cold, and I never
took chemistry but here goes ... chloramines have chlorine and ammonia,
and the concentration of ammonia and of chloramines may/will vary
tremendously depending on your municipality's process (could be
seasonal/construction/rainfall variable), so you might want to pick up a
chlorine/ammonia tester. You need to know if you just need to remove the
chloramine binding (any dechlorinator, double dosage if chloramines are
not specified) or if you also need to remove the ammonia left behind. If
you need to remove the ammonia, there are aquarium chemicals which
temporarily neutralize it (perhaps forcing it to an ammonium ion form)
but they might not suit your application. In the aquarium trade, ammonia
is removed by aquatic plants and/or nitrifying bacteria (if that helps
you any). Perhaps what you need is an algae scrubber ).
--
www.NetMax.tk

Doug Herr wrote:
Howdy good folk.

I am not currently an aquarium owner, but I have a question that you
should know something about. I make my own beer and I live in Oakland CA
where they use chloramine in the water. I purchased potassium
metabisulfite to remove the chloramine but I don't really know how much to
use. I have found references that widely vary but 500 to 700 mg per
20 gallons seems to be the best estimate I have found.

Well, I'll pull out the old chemist hat and give it a go.

From the reaction schemes I've seen, one molecule of metabisulfite
(S2O5--) is able to react with one atom of chlorine and convert it to
nontoxic chloride. The brochure from my water utility says: "The average
free residual chlorine concentration in the system is maintained at 0.15
to 0.20 parts per million." Let's bump that up to 1 ppm for good
measure. (I'd call the utility to confirm dosing levels, but it's a
holiday ...)

1 ppm is 1 microgram/L or 28 nM Chlorine. That means we need to dose the
water to at least 28 nM metabisulfite to treat it. Assuming no waters of
hydration in your potassium metabisulfite (222.32 g/mole), that means
you need 6.3 mg/L.

20 US Gallons is 75.7 L, so you'd need just over 475 mg per 20 gallons
to treat a 1 ppm chlorine level. If you had a higher level of *total*
chlorine, you'd need to up that in proportion.

Note that there is no problem with dosing more - it's reported to be
safe for fish, and the excess just reacts with oxygen anyway. (I ran
across some mailing lists where some people claim to intentionally
overdose their alcoholic fermentation to limit adverse effects of oxygen.)

Note to the fish-keepers: if you're have chloramines in the water, the
metabisulfite will detoxify the chlorine, but will release ammonia. So
our hypothetical 1 ppm chlorine will release somewhere around 0.25 - 0.5
ppm (by wt) ammonia if it's present as chloramines.

Products like AmQuel use hydroxymethanesulfonate (HOCH2SO2H) or
hydroxymethanesulfinate (HOCH2SO3H) to both convert chlorine to chloride
and bind the ammonia.

As always, the Krib is a good source of details:
http://www.thekrib.com/Chemistry/cl.html

P.S. Anyone know of a cheap source of hydroxymethanesulf(o/i)nate
available to consumers?

Rocco Moretti wrote:

1 ppm is 1 microgram/L or 28 nM Chlorine.

1 ppm is on part in a million and hence 1 mg per kilogram or, since 1 l
water has a mass of 1 kg, 1 mg per l. The molecular weight of chlorine
is 70 (2 atoms of atomic weight 35), hence 1 mg/l is 14 uM.

1 ug/l would be 1 ppb (parts per billion) or 14 nM.

By the way, you do not need sodium metabisulphide (a reducing agent) to
convert chlorine, the much cheaper and less toxic sodium thiosulphate
will do so catalytically. This is what is contained in many water
conditioners.