OZONATION OF SEAWATER
From: Øyvind Jørgensen <Oyvind.Jorgensen@akvaplan.niva.no>
To: 'AQUA-L' <AQUA-L@killick.ifmt.nf.ca>
Sent: November 09, 2000
QUESTION:
Has anyone have any experience with using ozone for water treatment
in saltwater? The problem is that we tried to ozonate seawater, filtered
down to 100 micron, up to 750 mV in a u-tube, with a contact time of 2
min. Afterward, the water was passed into a tank where it stayed for 8
min, before neutralisation with thiosulphate before going into the
fishtanks. The water was used to rear halibut larvae from hatching and
beyond. After about a week a lot of the larvae started to die. After
stopping the ozone generator it looked like the rest of the larvae
recovered, but after putting the generator on again the rest of the larvae
died. Using two different ORP meters the value was 750 mV, but by using a
Merck kit it shows very little rest ozone at all. Any suggestion what the
problem might be?
Oyvind Jorgensen
Troms Marin Yngel AS
Kraknes, 9100 Kvaløysletta, Norway
Tlph +47 77659010 Fax +47 77659011
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COMMENTS 1:
If you are using ozone with seawater you should be passing it through an activated carbon filter before introducing it to your fish tanks.
Maria Sparsis
E-mail: msparsis@sunet.net
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COMMENTS 2 :
I do not know exactly what´s the Merck kit like. But I feel it won´t
probably give you a very precise result. Here at the Oceanario, we found
that with oxidants values above 0.02 ppm (mg/L) we started to have
problems.
What is the value you read on your Merck kit? It might be that it
seems to be a low result, but with oxidants too little sometimes is too
much.
Gonçalo David Nunes
Biology Department
Oceanario de Lisboa
Portugal
E-mail : gdnunes@oceanario.pt
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COMMENTS 3:
The most likely culprit is bromine radicals. If your seawater is
high in bromine, the ozone will cause radicals to form that in essence
have the same effect as chlorine. Try using some bromine free
seawater (Instant Ocean) in the ozonator and see if you get similar
results on your testing apparatus.
Mike C.
E-mail: mchris@unix1.sncc.lsu.edu
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COMMENTS 4 :
Also bromine radicals are much more stable so they build up over time
and remain active for a much longer period than ozone. We had the
problem at the Milwaukee County Zoo where we used "Instant Ocean",
however our make-up water is not bromine free. To compensate we
operate or ozone generator at reduced power and only for 8 hours per day.
I have heard that a number of other institutions have resorted to the
same practice.
Craig S. Berg
Curator - Aquarium/Reptile
Milwaukee County Zoo
E-mail: <csb@csd.uwm.edu>
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COMMENTS 5 :
Just a thought that the effect may not be the ozone itself but the
sterilisation of water. My question would be what are your CFU's for
bacteria before and after you have used the ozone. The bacterial levels
may bounce quickly even though you have used the ozone (within 6-8 hours)
particularly if you are adding non sterile additives and you might find
there are high levels of bacteria present. The challenge with their growth
is that it might be of a single species which might be actually worse than
a mixture. To assess all this you need to know CFU numbers and identify
the bacteria.
Stephen B. Pyecroft BVSc Hons
Aquatic Diagnostic Services International Pty Ltd
Brisbane, Australia.
E-mail: Stephen.Pyecroft@dpiwe.tas.gov.au
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COMMENT 6 :
You should contact Norsk Ozone.
www.norsk-ozon.no
or kje@norsk-ozon.no
They have a biologist on staff that has been working with ozone and
seawater for years.
OIav Lyngstad
Fjord Halibut
NO-6475 Midsund
NORWAY
E-mail: olav@lillevik.no
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COMMENTS 7 :
1) 750 mV ozone is very high for fish especially larvae. We
usually shoot for somewhere between 300 mV and 450 mV. Ozone in seawater
produces some very reactive by-products. Many of these reagents have a
long life, some can last for days. The ozonated water should be passed
through activated carbon to remove the reagents.
2) Contact Aquatic Eco-Systems, the tech staff there was very
helpful.
Stuart May
E-mail: smay@bmd.clis.com
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COMMENTS 8:
As you probably already know, ozone is a very powerful oxidant. In
seawater, it can produce a number of undesirable oxidized ions which have
deleterious effects on many life forms, especially during development.
Common examples include iodate, bromate, and even chlorate ions. These all
have the potential of raising the ORP value of seawater. Are you using
natural or synthetic seawater? ORP measurements are notoriously misleading
and often incorrect. It is possible for a water to have an ORP of +750mV,
however I recommend checking proper electrode operation by the use of a
diluted tincture of iodine solution.
Please contact me if you would like the details of this simple
procedure.
My conjecture is that residual ozone is not the culprit but you just
have
created a relatively strong oxidizing aquatic environment for your
delicate life forms.
Carl Nelson
ENC Labs
E-mail : enccarl@earthlink.net
http://www.enclabs.com
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