Dissolved Oxygen Meter

[barneey]

Anyone know where I can hire / borrow a dissolved oxygen meter? from.

Dont really want to, or can afford to buy one at the moment and its more of a thing I`ll use once in a blue moon.

Only place I could find were these http://www.caledonianlabs.co.uk/Service ... vices.html

Cheers

[barneey]

Dose anyone know if this meter would be any good for measuring oxygen in wort. The manual only mentions water so at the very least it could be used to experiement / test a setup with boiled water as the liquid.

Meter Clicky

Any help appreciated.

EDIT is oxygen more readily dislove in wort or plain boiled water.

Cheers

[darkonnis]

Well I am not sure however here are some things on DO:

Water is able to dissolve a little oxygen in it, (about 8 to 15 mg/litre depending on temperature and salinity,- higher temperature or more dissolved salts reduces DO). Active fish, eg trout, need about 5 - 8 mg/l of DO.

As the water temperature increases,-

• the amount of DO that the water can hold decreases,- (11.29 mg/l at 10 OC; 9.09 mg/l at 20 OC; 7.56 mg/l at 30 OC)

• the metabolic rates of the local aquatic organisms increase, (in general the rates double for every 10 OC rise in temperature), so the organisms need more oxygen.

• any oxygen demanding wastes in the water are oxidised faster, so reducing DO at a faster rate.

It is also important to note that dissolved solids reduce the amount of oxygen in water. This is true of salts and I'm not sure about sugars, but it stands to reason that the same would apply to some extent. Hope that helps mate

[barneey]

Thanks for the reply, I`m going to have to do some more reading up I think.

Basically the experiment at the moment consists of boiling water for 30mins to drive off the oxygen, cooling to 20 c, measure amount of oxygen in boiled water, bubbling pure oxygen through the water at 1 or 2 ltr per min for a set amount of time, measuring oxygen level again.

Dunc has already pointed me to the artical in the "Yeast" book + Aleman has mentioned about his setup with the spray plate etc.

Reason behind using water initially is that I didnt want to mess a brew up experimenting.

Cheers

C

[darkonnis]

It is very likely that such an experiment has already been conducted on water. I would search google scholar myself, that would be a good palce to start.
Out of interest mate, was there was reason for this experiment or just a case of curiosity?

[Martin G]

There are test kits for about £20 that do about 20 tests. Might be an option in this case. I have been thinking about getting one to see how my techniques work, I was concerned about the sugars in the wort affecting the chemistry.

[barneey]

It is very likely that such an experiment has already been conducted on water. I would search google scholar myself, that would be a good palce to start.
Out of interest mate, was there was reason for this experiment or just a case of curiosity?

For me its just another step to get a "perfect" brewday, people spend a lot of time & money on brewing setups, making yeast starters, measuring equipment for weighing ingredients etc, timers etc, gravity readings. Then what happens? you either shake the hell out of a fermenter / drop an airator in / or whisk with a mechanical means to get oxygen back into the wort. My quest is really to find out how much dissolved oxygen there is at the beginning of the fermentation process by the means I use, ie oxygen gas cylinder and what is required to get it to the 8ppm target.

As for the kits, is that the "winkler method" ?

Cheers

[jaybie]

Thanks for the reply, I`m going to have to do some more reading up I think.

Basically the experiment at the moment consists of boiling water for 30mins to drive off the oxygen, cooling to 20 c, measure amount of oxygen in boiled water, bubbling pure oxygen through the water at 1 or 2 ltr per min for a set amount of time, measuring oxygen level again.

Dunc has already pointed me to the artical in the "Yeast" book + Aleman has mentioned about his setup with the spray plate etc.

Reason behind using water initially is that I didnt want to mess a brew up experimenting.

Cheers

C

Bubbling pure O2 is a waste of money, it is really quite insoluble and so effectively all of it will be wasted. Better off bubbling air through, the other gases in air won't really affect the solubility of O2, and air costs much less than bottled gas. You can also increase the dissolved O2 (up to the saturation point) by adding hydrogen peroxide (you can get it from Boots) but of course not with live yeast.

[gregorach]

Bubbling pure O2 is a waste of money, it is really quite insoluble and so effectively all of it will be wasted. Better off bubbling air through, the other gases in air won't really affect the solubility of O2, and air costs much less than bottled gas. You can also increase the dissolved O2 (up to the saturation point) by adding hydrogen peroxide (you can get it from Boots) but of course not with live yeast.

That's entirely contrary to the data presented by Chris White in "Yeast"... Do you have a source for this claim that bubbling O2 through a diffuser stone will not get O2 into solution, with actual measured data?

[Bobba]

There are test kits for about £20 that do about 20 tests. Might be an option in this case. I have been thinking about getting one to see how my techniques work, I was concerned about the sugars in the wort affecting the chemistry.

Salifert do an o2 test kit. I bought one a while back, but never used it as it was immediately obvious that it wouldnt work with wort.... determining the exact shade of light pink in a backdrop of dark wort wouldnt be possible. It probably trashes the test chemistry also, but not exactly relevant if u cant see the result!

Fine with water for any experiments, but as mentioned, this is all well documented, particulary in the yeast book.

[jaybie]

Bubbling pure O2 is a waste of money, it is really quite insoluble and so effectively all of it will be wasted. Better off bubbling air through, the other gases in air won't really affect the solubility of O2, and air costs much less than bottled gas. You can also increase the dissolved O2 (up to the saturation point) by adding hydrogen peroxide (you can get it from Boots) but of course not with live yeast.

That's entirely contrary to the data presented by Chris White in "Yeast"... Do you have a source for this claim that bubbling O2 through a diffuser stone will not get O2 into solution, with actual measured data?

I'm not sure what you mean - I didn't mention a diffuser. I was trying to say that of the O2 that is bubbled through, most (not all) of it will not enter solution. Oxygen enters solution slowly relative to the residence time of the bubble within the water. When bubbling pure O2, every bubble that reaches the surface contains wasted oxygen, because if you had 100% of the O2 entering solution the bubble would disappear before reaching the surface.

Smaller bubbles, as achieved with a diffuser stone, will improve the rate of dissolution as there is a greater O2/water interface over which the O2 can enter solution. Smaller bubbles are better as the surface area / volume ratio is improved and smaller bubbles move more slowly through the water.

In "non-brewery" fermentations such of those of bacteria, mechanical agitation is often used to break up bubbles and hold them in the water for longer to improve gas exchange, as getting very small bubbles is difficult and often requires quite high pressures. An excellent source of information on aeration (and many other aspects of fermentation biology) can be found in Principles of Fermentation Technology, by Stanbury & Whitaker, published by Pergamon; it is very thorough, is very heavy on maths, uses symbols I don't have on my keyboard, but is not aimed at brewers. I used it as my reference for a module on aeration and agitation a couple of years ago during my masters in microbiology.

I just felt that given the price difference between bottled O2 and common-or-garden air, and the fact that much of the O2 bubbled through never makes it into solution, that air represents better value for money. If money is not a concern then yes, using pure O2 will get oxygen in solution faster.

[barneey]

For reference I`m using a stainless steel air stone for the oxygen experiments similar to this one http://www.hopandgrape.co.uk/public/det ... TA20069953, although initial trials have resulted in quite a few of these bubbles reaching the surface of the liquid, this might be less of an issue with a taller conical fermenter or finer adjustment of the flow rate etc.

As I have already bought the gas for the experiments, cost at the moment isnt an issue, the only concern for me is how much oxygen is getting into the liquid and the best way forward to measure the result.

Cheers

C

[adomant]

I don't think there is a cheaply available tool to do this, I wonder if wort could be analysed by someone like Murhphy's to provide the necessary analysis (among other things they could analyse? My take is that with pure O2 (especially used inline) it is possible to overoxygenate the wort with undesirable effects-also that foaming could be an issue.

Aleman had a good tip: using a splashplate to fill the fermentor after/ while O2 is being pumped into it. I am trying this with a sterile air pump as I'm not keen on keeping O2 canisters around.

[darkonnis]

Indeed, why not give brewlab a ring and see if they either "know" the ideal conditions to get roughly the amount of O2 into the wort that you want (IE set flowrate and temp with an O2 stone that has openings of X size) or if they will analyse it for you and how much that'd be. Maybe cheaper doing it that way than hiring or buying a DO meter

[gregorach]

Bubbling pure O2 is a waste of money, it is really quite insoluble and so effectively all of it will be wasted. Better off bubbling air through, the other gases in air won't really affect the solubility of O2, and air costs much less than bottled gas. You can also increase the dissolved O2 (up to the saturation point) by adding hydrogen peroxide (you can get it from Boots) but of course not with live yeast.

That's entirely contrary to the data presented by Chris White in "Yeast"... Do you have a source for this claim that bubbling O2 through a diffuser stone will not get O2 into solution, with actual measured data?

I'm not sure what you mean - I didn't mention a diffuser. I was trying to say that of the O2 that is bubbled through, most (not all) of it will not enter solution. Oxygen enters solution slowly relative to the residence time of the bubble within the water. When bubbling pure O2, every bubble that reaches the surface contains wasted oxygen, because if you had 100% of the O2 entering solution the bubble would disappear before reaching the surface.

Smaller bubbles, as achieved with a diffuser stone, will improve the rate of dissolution as there is a greater O2/water interface over which the O2 can enter solution. Smaller bubbles are better as the surface area / volume ratio is improved and smaller bubbles move more slowly through the water.

Ah, I see the confusion then. AFAIK, everybody who uses O2 uses a diffuser stone, usually either 2 micron or 0.5 micron.

Anyway, given the amount of O2 we actually use and the price of a disposable cylinder, it's not exactly a big expense... A few pence worth of wasted gas isn't worth worrying about, especially when compared to the price of the equipment.