Dissolved oxygen meter

Wookii

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How long do the increased DO levels, however they are generated, remain in the water column? With CO2 for example, even with fairly vigorous surface movement from a filter outlet, the levels don’t come down to atmospheric equilibrium even after 12 hours. Is DO similar?
 

dw1305

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Hi all,
the levels don’t come down to atmospheric equilibrium even after 12 hours. Is DO similar?
Diffusion of all <"dissolved gases is pretty slow">, which is why you need to maximise the gas exchange surface. You can see that this is potentially a two-way street, leading to potential <"oxygen super-saturation in suitable conditions">.

You can process wastes with really high BOD (or you can think of it as <"really large negative ORP values">) if it you can get enough <"oxygen into them">.

cheers Darrel
 

jaypeecee

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Could an ORP meter be used instead??
Hi @Nick potts

I use a combination of the JBL O2 test kit and an ORP meter. I find that the ORP meter gives a very useful indication of O2 level. As ORP is measuring oxidation-reduction potential, there is not one figure that I could give - all tanks will vary. But, I've done enough measurements now to know what to expect from my tanks. A typical figure would be around +200 mV and I consider +250 mV to be a good reading. I don't use ozone (O3) but measured doses of hydrogen peroxide (H2O2) will, as expected, increase the ORP figure. I still have more experimentation to do. My interest in ORP stems from trying to get a handle on dissolved organics (DOC/DOM).

JPC
 

Wookii

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Last edited:

jaypeecee

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Stumbled on this whilst looking for dissolved CO2 meters. No idea if it they're accurate enough for your purposes, but Extech models are a bit more budget friendly:

https://www.test-meter.co.uk/catalogsearch/result/?q=dissolved oxygen

Edit: membranes are also a lot cheaper at £25 for 10
Hi @Wookii

I have an Extech pH/ORP meter and it has served me very well for over five years. My understanding is that an ORP meter can be converted to a dissolved oxygen meter by use of a semi-permeable PTFE membrane and that's possibly what Extech are using. It's on my 'to do' list! I use the same principle when measuring dissolved CO2 except that I use the pH electrode in KH 4 solution and separated from the tank water by a very thin silicone membrane - it seems to work very well.

JPC
 

Soilwork

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