Re: [Killietalk] Thiosulfate de-chloroamine in city watyer

[Wright Huntley <whuntley at verizon_net>]

Ken Simolo wrote:
> Hi Lee,
>
> But will you not still get the ammonia spike from breaking down the 
> chloramine?  That's a bigger problem than the chlorine in my opinion. 
>   
You usually get a spike of harmless ammonium (NH4-) ions. Ammonia (NH3) 
mostly forms at higher pH and is the deadly version.

In most cities with older plumbing, EPA has required they add enough 
alkali to get a pH of 8 or so, to prevent dissolving lead from that old 
plumbing.

The combination of high pH and the ammonia created by it is the deadly 
problem. Hard ground water also often has a high pH. Sierra runoff also 
may have a high pH (silicates from granite) but is soft and so weakly 
buffered that atmospheric CO2 quickly brings it down into the mid 7s. 
Just aerate overnight before using.

Folks with a pH of 7.5 or below can probably ignore the ammonium burst. 
It gradually evaporates as it slowly converts to ammonia, or is used by 
the plants as food. Above 7.8, look out!

There is a simple equation that describes the rate of formation of 
ammonia at any pH. At room temperatures, there is about 50 times as much 
toxic ammonia at pH of 9 as at a pH of 7. Since 5 ppb (yeah, parts per 
billion) has been shown to cause severe gill damage in young fish, it 
takes very little ammonia to do the nasty work. The stunting and poor 
health may not always be obvious. It takes more to kill outright.

It is the combination of high pH and chloramine that means we may need a 
decloraminator like "Prime" or "Amquel" and cannot rely entirely on 
simple hypo (thiosulfate) based dechlorinators. Simply breaking the 
chlorine ammonia bond isn't enough. We need to remove or sequester the 
ammonium until the plants use it or organics in the tank absorb it.

Reference: Stephen Spotte's _Fish and Invertebrate Culture_ a 
long-out-of-print classic.

Wright

-- 
Wright Huntley - 805 Valley West Cir., Bishop CA 93514 - whuntley at verizon_net 760 872-3995.

"But there's no system so imperfect that a helping hand from Washington can't make it worse."

-- Steve Chapman in Reason Magazine

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