BACTERIOSTAT/CIDE

From: Dror Angel <angel@agri.huji.ac.il>
To: <AQUA-L@killick.ifmt.nf.ca>
Sent: January 14, 2000

QUESTION:

I am planning to sample a seawater biofilter on a frequent basis (every 15 minutes) to follow nitrification dynamics and I am looking for a simple, very rapid, safe (i.e. non-toxic), efficient means to stop all bacterial activity as soon as the sample has been taken. Moreover, I would prefer not to alter the pH since samples will serve for nitrogen determinations (ammonia, nitrite, nitrate).
Does anyone have any additional ideas re methods that are non-toxic
and do not affect the spectrophotometric analysis of ammonia, nitrate, nitrite in the samples?

Dror Angel
National Center for Mariculture
Israel Oceanographic & Limnological Research
P.O.B. 1212
Eilat 88112
ISRAEL

Tel:  972-76-361-440
Fax: 972-76-376-761
e-mail: angel@agri.huji.ac.il

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COMMENTS 1:

There is one very simple method to do this. Once you have collected the sample you filter it through a membrane filter of 0.45 micro m of diameter. It will remove all microorganisms (except mycoplasms and free viruses) from your sample and it will not alter your pH for sure. When this is done, you should freeze your sample in a bottle completely filled (to prevent exchanges with air head space) if analyses are to be conducted later on.

Regis Pilote (Ph.D. cand.)
Groupe de Recherche en Recyclage Biologique et Aquiculture
Departement des sciences animales
Faculte des sciences de l'agriculture et de l'alimentation
Cite universitaire (Quebec)
Canada G1K 7P4
Tel: (418) 656-2131 poste 4043
Fax: (418) 656-3766
E-mail: acb282@agora.ulaval.ca

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COMMENTS 2 :

Pass it through a 0.2 micron filter.

David Cox

E-mail: dave@fishvet.co.uk

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COMMENTS 3 :

For use during the BOD test there is a nitrification inhibitor
which can be used so that one can determine the carbonaceous BOD within a sample. The nitrification inhibitor is called just that : 'nitrification inhibitor' if you look it up in a lab supplies catalog.  There are also "recipes" for this in the book: Standard Methods for the Examination of Water and Wastewater. However this may not be all you need because the breakdown of organics will continue within your samples; I don't see how you may stop this without altering the pH.

Edward Parker

M.Sc. Biology candidate
University of New Brunswick, Canada

E-mail: eddyp@fundy.net or n7nk7@unb.ca

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COMMENTS 4:

We are running relatively intense abalone recirculation and biofiltration under test conditions.
Could I suggest (I have not done this but it would be my first choice) that you remove bioload and flush with 'non-loaded' ie clean seawater (ie same pH and rest as 'loaded' water). This should rapidly halt the nitro-reactions.
To start up again, reintroduce the bio-load (and the 'loaded' water if you really want to)

Mark Miles
Global Ocean Holdings - Mariculture and Associated Development with Coastal Communities
Tel: (028) 271 5666(w); (082) 773 2707(mobile); (28) 273 8308(h)

E-mail: markm@globalocean.co.za
URL: www.globalocean.co.za

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