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Re: Denitrator question...



> From: Kevin.Buckley at uk_neceur.com
> Subject: Re: Denitrator question (freshwater) - CO2 & plants
> 
> In case anyone's interested ...
> 
> The denitrator was producing 0ppm NO3 outflow from 40ppm input within 48
> hours at about 200ml / hour.
> 
> Within 3 weeks it was processing NO3 at a flow rate of 1 litre/hour & tank
> Nitrates have remained at zero.
> 
> It's completely trouble-free so far (& seemingly insensitive to flow rate
> at the low levels I'm using) except that it seems to also be reducing the
> KH of the tank at a rate of around 1 degree / week.
> 
> I've compensated for that twice now (raising the KH from 2 degrees back to
> 4 degrees) but it's still happening - yesterday it was back down to 3.
> 
> The outflow KH is the same as the inflow KH though, as is the pH, (within
> the limits of home testing) so it's clearly a very gradual process.

	At a reduction of 1KH/week, I wouldn't expect a measurable difference
between the intake and outlet.

> 
> Happy New Year everyone!
> 
> Someone bought me a denitrator for Christmas &, as a gadget freak with
> mains water already high in Nitrates, I thought I'd give it a go (Sulphur
> based, made by Deltec - see
> http://www.ultimateaquatics.co.uk/acatalog/Deltec_Equipment.html for a
> picture).

(snip) 

> - - I read somewhere that the outflow is quite acidic & that the reason is
> because one of the reaction components is xxSO4;

	I looked at the web site, and I wouldn't be at all surprised if
the bacteria are making sulphuric acid, if they are using sulphur.

> - - Is that because it forms H2SO4 (or some other acid - is H2SO4 a "strong"
> acid BTW?)?

	It is.  The strong acid would then destroy the KH:

	HCO3-  +  H+  ->  H2O  +  CO2 (leaves)

> - - If the above is true (or even if it's not) how will this affect my
> ability to calculate my CO2 content using the KH / pH formula?

	Not at all.  There is no problem provided there are no other
_weak_ acids around.

> Mainswater is 30ppm NO3, GH=16, KH=5;
> Water change is just using mains water when the tank Nitrates start to get
> too high (remember, they start at 30ppm!).

	I would just do lots of water changes if the NO3- concentration
tends to rise.  I don't think 30 ppm will
present a great problem, and if the plants grow well and the fish load
isn't too high, it will fall with time, not build up.  In that case,
to keep NO3- down, one _avoids_ water changes!


-- 

Paul Sears
psears_at_nrn1.nrcan.gc.ca, 613-996-4171, facsimile / tÚlÚcopieur 613-996-9400
Natural Resources Canada, 1, Haanel Drive, Nepean, Ontario K1A 1M1
Ressources naturelles Canada, 1, Haanel Drive, Nepean, Ontario K1A 1M1
Government of Canada / Gouvernement du Canada