Previous Discussions On Oxygen Transfer From Air Stone Bubbles

[fishguy2727]

Not to get back into it, but technological advancements are not equal to scientific research. All I said was most likely someone has done a similar study since then, so going ONLY by a 1956 study is not enough IMO. The argument was whether the aeration provided by bubbles is by the surface agitation they create or by the bubbles themselves. Many people believe that effectively only the surface agitation is the reason, and I don't agree with it. Apparently neither do the commercial ponds who use the aeration described previously.

Back on topic, I don't think a biofilm is as vital as it is made out to be here. They are important, but they are not a make or break situation. A mature tank is hard to define and will vary from aquarist to aquarist. Some people will define it as any cycled tank, some will say a cycled tank that has been stable (no problems) for a certain period of time (like six months, a year, etc.). Others will have their own variation or stipulation to define it. There isn't an established definition for a mature tank, but most people would agree it is one that is older and more stable than merely cycled, and stable enough to keep less hardy fish healthy and allow them to thrive. In the end a lack of maintenance can undo any tank, resulting in health problems or even a crashed system.

 

[fishguy2727]

A good strong air pump is always a good idea. They cost very little (especially compared to all the other things you bought for the fish and the fish themselves) and they can save the entire tank if anything happens. Equipment fails, if the Eheim is barely aerating the tank and for some reason it stops running (which definitely does happen) they are left with no aeration at all. This can start killing fish in only a couple hours, you could have a dead tank by the time you get home one day.

Bubbles actively aerate the water. Gas exchange occurs at ANY air-water surface. The oxygen doesn't stop and think, 'Hey, this is just a bubble, I can't cross here, I have to wait until I am in the air above the water.' This is well known and accepted in other industries, but for some reason it just can't seem to catch on here (maybe because none of us are professionals, just hobbyists, regurgitating what we hear other hobbyists claim?). Bubble aeration is a strong tool in both aquaculture (real aquaculture, not hobbyist aquariums) and sewage treatment because the bubbles themselves actively aerate the water column.

I have seen multiple tanks saved multiple times because they had an air pump, including a 220 with a 2' pacu in it that had only an air stone running for a week (and this happened multiple times). No one gains anything but a few bucks by not getting an air pump or arguing against them, the fish could get everything back if you spend the money on that simple, cheap piece of equipment. Not to mention that some fish actually enjoy them, so why deny that from them?

 

[fishguy2727]

Assuming you have one of those magical filters that NEVER stops working. It NEVER gets jammed, it NEVER wears out, and the impeller NEVER breaks or needs replacing. Then yes, you don't need an air pump...

 

[Bignose]

Bubbles actively aerate the water. Gas exchange occurs at ANY air-water surface. The oxygen doesn't stop and think, 'Hey, this is just a bubble, I can't cross here, I have to wait until I am in the air above the water.' This is well known and accepted in other industries, but for some reason it just can't seem to catch on here (maybe because none of us are professionals, just hobbyists, regurgitating what we hear other hobbyists claim?). Bubble aeration is a strong tool in both aquaculture (real aquaculture, not hobbyist aquariums) and sewage treatment because the bubbles themselves actively aerate the water column.

fishguy, we've been over this in other threads. The only point I want to address is that what you are saying here is NOT "known and accepted" in other industries.

If so -- why would any industry build a distillation tower with trays or packing in it? The trays and packing increase the surface area for exchange -- just like the top of a fish tank. And, as a professional in this field (you can't just assume that "none of us are professionals") almost every single distillation tower has some form of packing and/or trays and/or caps and/or refluxes to increase the time and surface area of contact -- because bubbles alone are not enough.

The simple truth is that the bubbles alone, when simply rising though a short column of liquid, do not have enough surface area or time to exchange anything but an amount of gas that is essentially meaningless compared to the amount of gas exchange that occurs at the surface. Please review the last time we had this conversation on this forum for the math which performed this comparison for you -- and showed that the gas exchange at the surface was hundreds of thousands of times more significant than the gas exchange from the bubbles.

 

[fishguy2727]

So sewage treatment plants don't use aeration?
Aeration via bubbles is not used in aquaculture at fish farms?

What is the minimum interaction time for gas exchange to occur? If what you claim is true then there is a minimum interaction time which would mean that if there is a lot of flow at the surface of an aquarium the water would not be in contact with the air long enough to be aerated.

Again, it costs almost nothing compared to the rest of your setup and could save the entire stock of the tank. Why argue against it so hard?

 

[fishguy2727]

Either way I prefer to have an air stone on every freshwater tank, it can save the whole thing. People do argue against that saying that they do nothing, if the filter ripples the water you don't need it, etc. This is not the case.

And I do believe that the bubbles themselves actively aerate. I would love to see some factual information to the contrary.

 

[Bignose]

And I do believe that the bubbles themselves actively aerate. I would love to see some factual information to the contrary.

I have never said that they don't aerate. It is just that the amount of gas that the bubbles in a typical home aquarium would exchange under the most favorable conditions is 1/100 000 th of the amount that the top of that tank would exchange. To me, that is negligible when discussing what is most important for the fish. I have also always said that a benefit of an airstone is to help circulation to bring water from the bottom of the tank to the top. But, that circulation is NOT gas-exchange. It is helpful in keeping the oxygen levels pretty well-mixed in the entire tank, but if anything a well-mixed tank will actually lead to LESS gas exchange from a bubble, because the gradients will be less.

The facts have been posted on this forum, mostly in direct response to your posts, in a previous thread. If asked, I will find it again, or I will copy and paste from those previous thread and post again. But, the mathematics in those old threads is pretty conclusive in my mind, because the assumptions made are reasonable and no one posted anything contradictory.

And, speaking of facts, in that thread, you never rebutted my calculations. Your major argument was that the model I used was originally developed in the 1960s and that was too old for you. You never gave a reason why it was wrong -- any physical reason why the gas-exchange calculations were wrong 50-60 years later now -- just that it was too old. The calculations presented are actually not that hard, and are a typical homework problem for someone in a college-level mass transfer class. That should tell you how well-confirmed the model calculations I presented were -- they were brand new 50 years ago, and today they are just ho-hum homework problems. As in, everyone who takes that class should know it because it is used so prevalently in industry.

Lastly, sewage treatment is not the same as fish keeping. Black water (the nice term for sewage water) is not the same as regular water. It has a different density, viscosity, and gas diffusion rates. Also, the treatment of sewage will use the oxygen more rapidly. All of this changes the gas-exchange rate, and I suspect that their exchange rates will be higher. Or, they could just be doing things inefficiently -- it isn't the first time that would happen. For example, I suspect that black water would not do well in a typical tower with trays or packing, if only because of the varying fluid parameters and the presence of varying solid content as well. So, in their case, it may make the best sense to use bubbles just because it is cheap and while marginally effective, it won't lead to problems that trying to use more effective methods would. There are other considerations to take into account than just gas-exchange rates when looking at what 'industry' does. I actually suspect that this may be that same for aquaculture, too. Air stones and pumps are very cheap, and it could very well be a case of 'it's the way we've always done it and it works, so why change it?'

 

[fishguy2727]

Really, 1956. That is a joke. I would have been laughed at and received an F if I ever tried to include a 1956 reference in a paper I wrote in college.

Any info in the past 50 years? Ideally within the past 10? If not than there is nothing to discuss.

Buy an air pump, it can save your entire tank one day.

 

[Bignose]

Really, 1956. That is a joke. I would have been laughed at and received an F if I ever tried to include a 1956 reference in a paper I wrote in college.

Any info in the past 50 years? Ideally within the past 10? If not than there is nothing to discuss.

The fundamentals of how the equations are derived have been known for quite a few years.

If you wrote a paper on college about general relativity, and don't include a reference Einstein's 1916 paper, you'll get an F. Because -- *gasp* hold on to your hat here -- general relativity is still right.

Open any textbook on mass transfer printed in the last 10 years, and you'll see the exact same equation. It is still right after all these years because the work done on it was well done.

 

[fishguy2727]

Like I said, 1956 is a joke. Find something supporting it from the past two decades and I will check it out. Yes, maybe I would not get an A without mentioning Einstein in that paper, but I would fail it if I didn't find more recent studies showing that it is still accurate and accepted. Sticking with something so old and not supporting it with anything more recent is not scientific, it is blind.

Like I have asked many times, you claim bubbles don't have enough reaction time, what is the minimum reaction time? That EXACT same idea would support that too much water flow at the surface would also limit reaction time, but I assume you don't believe this. So which is? Minimum reaction time or magical force preventing gas exchange in bubbles? Why do some sources say no additional aeration is needed in a SW tank with a protein skimmer? The massive amount of surface area in all those bubbles aerate very well.

 

[Bignose]

Direct measurement of mass transfer around a single bubble by micro-PLIFI
J. Francois, N. Dietrich , , P. Guiraud, A. Cockx
Chemical Engineering Science
Volume 66, Issue 14, 15 July 2011, Pages 3328-3338

Experimental study of mass transfer in a dense bubble swarm
D. Colombeta, D. Legendred, A. Cockxa, P. Guirauda, F. Rissod, C. Danielf, S. Galinatf
Chemical Engineering Science
Volume 66, Issue 14, 15 July 2011, Pages 3432-3440

Mass Transfer From a Bubble in a Vertical Pipe

Paper no. AJTEC2011-44089 pp. T10183-T10183-9

ASME/JSME 2011 8th Thermal Engineering Joint Conference (AJTEC2011)
March 13–17, 2011 , Honolulu, Hawaii, USA
Sponsor: Heat Transfer Division
ASME/JSME 2011 8th Thermal Engineering Joint Conference

Author(s):
Shogo Hosoda
Kobe University, Kobe, Japan

Ryosuke Sakata
Kobe University, Kobe, Japan

Kosuke Hayashi
Kobe University, Kobe, Japan

Direct numerical simulation of bubble-liquid mass transfer coupled with chemical reactions: Influence of bubble shape and interface contamination
C. Wylocka, , , A. Larcya, P. Colineta, T. Cartageb, B. Hauta
Colloids and Surfaces A: Physicochemical and Engineering Aspects
Volume 381, Issues 1-3, 20 May 2011, Pages 130-138

A population balance approach considering heat and mass transfer—Experiments and CFD simulations
KREPPER Eckhard (1) ; BEYER Matthias (1) ; LUCAS Dirk (1) ; SCHMIDTKE Martin (1) ;
Nuclear engineering and design
2011, vol. 241, no8, pp. 2889-2897

Nitrogen as an indicator of mass transfer during in-situ gas sparging
Gerd U. Balckea, d, M. Hahnb, Sascha E. Oswald
Journal of Contaminant Hydrology
Volume 126, Issues 1-2, 25 September 2011, Pages 8-18

Demonstration of Mass Transfer Using Aeration of Water
Sultana R Syeda, BMS Arifin, Md M Islam, Anup Kumar
Journal of Chemical Engineering, IEB Vol. ChE. 25, No. 1, December 2010 pp.56-60

Review of mass transfer aspects for biological gas treatment
Norbertus J. R. Kraakman, Jose Rocha-Rios and Mark C. M. van Loosdrecht
APPLIED MICROBIOLOGY AND BIOTECHNOLOGY
Volume 91, Number 4, 873-886


Investigations on hydrodynamics and mass transfer in gas–liquid stirred reactor using computational fluid dynamics
Panneerselvam Ranganathan, Savithri Sivaraman
Chemical Engineering Science
Volume 66, Issue 14, 15 July 2011, Pages 3108-3124
10th International Conference on Gas–Liquid and Gas–Liquid–Solid Reactor Engineering

Measurement of the Dynamical Mass Transfer of a Single CO2 Bubble Using LIF/HPTS Visualization and a Photoelectric Optical Fiber Probe
Author(s):
Kodai Hanyu
Shizuoka University, Hamamatsu, Shizuoka, Japan

Takayuki Saito
Shizuoka University, Hamamatsu, Shizuoka, Japan
Paper no. ICONE18-30073 pp. 835-843
doi:10.1115/ICONE18-30073

18th International Conference on Nuclear Engineering (ICONE18)
May 17–21, 2010 , Xi'an, China
Sponsor: Nuclear Engineering Division

A NOVEL METHODOLOGY TO MEASURE MASS TRANSFER AROUND A BUBBLE
JESSICA FRANCOIS
Université de Toulouse; INSA; INP; UPS; LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France
INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France
CNRS, UMR5504, F-31400 Toulouse, France
NICOLAS DIETRICH
Université de Toulouse; INSA; INP; UPS; LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France
INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France
CNRS, UMR5504, F-31400 Toulouse, France
ARNAUD COCKX
Université de Toulouse; INSA; INP; UPS; LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France
INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France
CNRS, UMR5504, F-31400 Toulouse, France
Volume: 25, Issue: 25(2011) pp. 1993-2000

I trust that these 10 papers which all reference the 1956 paper -- BECAUSE AGAIN, THE WORK SO WELL DONE IN THE FIRST PLACE -- satisfies you. I mean, seriously, science doesn't reinvent everything every 10 years -- it builds on previous work. What field doesn't build on previous work? What field changes so rapidly that anything older than 10 years is immediately ignored? If the papers don't satisfy you, then there is no hope at all, you're just one of those people whose mind cannot be changed regardless of how much evidence is given you.

 

[fishguy2727]

Any abstracts or anything? Otherwise kind of useless. Without being able to read the studies they are pointless. I have read too many errored studies to trust the 'cited by' list you pulled from the original study without any other info. Many studies are very errored, sometimes the researcher comes up with the exact opposite conclusion that his data supports.

I like how the real questions are completely ignored. What is minimum contact time? With your exact same thought process too much flow at the tank's surface will inhibit aeration since water moves past the surface at least as quickly as a bubble passes through water.

Regardless of all of this:
BUY AN AIR PUMP! IT COULD SAVE YOUR ENTIRE TANK ONE DAY! I HAVE SEEN THIS HAPPEN OVER AND OVER AND OVER!

 

[Bignose]

Any abstracts or anything? Otherwise kind of useless. Without being able to read the studies they are pointless. I have read too many errored studies to trust the 'cited by' list you pulled from the original study without any other info. Many studies are very errored, sometimes the researcher comes up with the exact opposite conclusion that his data supports.

I like how the real questions are completely ignored. What is minimum contact time? With your exact same thought process too much flow at the tank's surface will inhibit aeration since water moves past the surface at least as quickly as a bubble passes through water.

I don't know what the minimum contact time would be for a bubble to get significant mass transfer. I'll have to do some calculations. I'll try to work on doing that this week.

The question about the top of the tank is a red-herring because the top of the tank is exposed to air for the entire time. So the time exposure is really infinite instead of the mere seconds it takes for a bubble to rise from the bottom to the top. And, more flow at the top of the tank is better because that leads to more circulation in the entire tank, which means that whatever mass transfer that occurs at the surface would get nice and well-mixed with the rest of the tank. Another reason that the top of the tank has good mass transfer is because the volume of fresh air is also infinite, whereas the volume in a bubble is finite. The velocity of the flow at the top is not necessarily 'at least a quickly as a bubble passes through water' -- it could be faster, it could be slower, it really depends on the circulation rate.

Lastly, I am not going to spoon feed you every paper about mass transfer in a bubble. 1) the papers are out there for you to read if you want. It is not up to me to get them for you. As soon as I were to post an abstract, then you'd say that 'without the full text it doesn't mean anything' 2) what is that nonsense about 'Many studies are very errored, sometimes the researcher comes up with the exact opposite conclusion that his data supports.' ?!?! If the papers were that bad, the peer review would have caught them and they wouldn't be published. As it is, the fact that they are published means that they have been peer-reviewed and have been judged to be quality work. Your phrase there is just an excuse to selectively believe or ignore whatever you want. Which leads to 3) I really believe that there is no convincing you anyway, so I don't feel like wasting my time. If you were sincere in wanting to learn about mass transfer, I could actually show you a derivation -- including all the assumptions that went into the derivation -- that was used for the formulas for the estimates. Maybe there is an assumption that isn't quite valid or misapplied. That is a discussion I would really enjoy having with someone who wanted to learn and discuss back and forth. But, so far, you haven't shown any interest in that. Your mind is made up, and no matter how many papers from any year I could come up with to show how these calculations are done every single day in industry (successfully, I might add since the mathematical estimates and the actual results match pretty doggone well), you still won't change your mind. That is fine, you are free to believe whatever you want. Just every time that I see the question being asked about how much gas-exchange happens from an airstone, I am going to post that it is negligible. Because that is what the calculations show; calculations based on extremely well verified models. How you can conveniently continuously ignore that is a mystery to me, but hey, whatever. Some people still believe in the Tooth Fairy, too.

In general, I think your mind is made up about an awful lot in fishkeeping. You only think one brand of food is good enough. You are convinced that airstones do more than they really do. etc. etc. etc.

So, I really wonder what your motivation for joining a forum is? Forums exist to exchange information and to learn from one another. It is ok to come in with some preconceived notions. But, you join a forum in order to get new information, which sometimes conflicts with those preconceived notions. At which time, you need to evaluate the new information. As an example, I always thought that water conditioner was absolutely necessary -- to keep the chlorine from killing the cycling bacteria and from harming the fish. I am pretty sure that some of my posts from years ago would have been pretty adamant about the need for water conditioner. However, through this forum, I learned that people were doing water changes without any kind of conditioner at all (water from city taps what put chlorine in their system). I learned that 1) the levels of chlorine in the water is good at killing small doses of bacteria, but is not concentrated enough to kill off the entire cycling bacteria colony, and that 2) most fish are also not harmed by the low levels of chlorine. 3) some of the strains of bacteria are actually resistant to chloramine and can use the amine part of the chloramine as an energy source like the cycling bacteria -- it is actually these strains that probably colonize the tank in the first place. With all that, I re-evaluated and agreed that water conditioner is not an absolute necessity. I still use it -- it is so cheap that my personal opinion is that there is no harm to using it -- but it is not an absolute anymore. I consider this a success story -- this forum allowed me to see different opinions and information that I otherwise would not have been exposed to.

Fishkeeping as a whole has a lot of inertia of old information being out there. The airstones is one. But also things like "ich can do dormant" or "ich is in every tank" is repeated very often. But, again, new information suggest that these aren't true. And forums like this can help spread this word.

But, if you aren't going to listen to any new information, again why join a forum? Just to come on and preach your ideas and only your ideas? If you aren't going to even try to learn something new, can I suggest that maybe a forum isn't the right place? That maybe you just want to start your own blog or website?

Otherwise, maybe you’d do me the favor of explaining why so reluctant to accept other pieces of information? I am as skeptical as the next person, and I don’t take too much just at a person’s word. There are a select few people whose word I would take, because they have shown themselves to be trustworthy to me in the past; but in general, I always ask for evidence. My history of posts on here bear this out. But, when good evidence has been provided over and over and over again – why still the reluctance to ignore it? Do you think that this is a great scheme that every bubble reactor and distillation tower have been pulling on engineers for a hundred years? That there is a mass transfer Illuminati out there silencing people who know too much about mass transfer from a bubble? I mean, the calculations I’ve presented have been used to build many millions of dollars of infrastructure around the world. What rational reason is there to claim that they are so unbelievable? Do you think that this is my personal trolling – going to random forums and posting mathematical formulas and making up research paper titles? I really just don’t understand.

Sorry about the really long post. Lots to get off my mind…

 

[fishguy2727]

Don't have time to read all that...

Bubbles rising in a tank are constant, so they also have 'infinite contact time'. It is no different than the water passing at the surface. Both are relative, water and air passing each other. If there is a minimum contact time like you claim there is a minimum contact time, regardless of how you look at it.

I know the flow rate at the surface isn't constant, that is my point. It CAN be AT LEAST as fast as a bubble passing through water. Which IF what you claim is accurate would prohibit gas exchange because of the lack of contact time between the water and air.

Mass transfer isn't accurate. A bubble may give up oxygen (losing mass) while also gaining CO2 (gaining mass). Aeration can take place without a change in mass.

If you haven't read the articles you shouldn't cite them. I am guessing you copy and pasted the 'cited by' list of the 1956 (LOL) article you love so much. Without reading them they may be citing flaws with that article. You cannot take them at face value, and definitely not how someone else interprets them.

"At which time, you need to evaluate the new information." Are these your words? Evaluate NEW information from 1956?

I am on forums to share information, and learn when I can. I do learn when good info is shared, but my education has taught me to be skeptical, very skeptical, of the info others provide. And an article from 1956 that conflicts with current practices (like sewage treatment and real aquaculture using bubble aeration for active aeration) isn't good enough. I do share valuable information, enough to be thanked on an almost daily basis on some forums (when I have time to be active).

Does anyone have an oxygen meter? If so I have an idea for an experiment for this subject if anyone with access to an oxygen meter would like to run it.

 

[Bignose]

Who said I didn't read them!!!! I read through every one to make sure that they were relevant to the question of mass transfer through a bubble. Because there were a lot more papers that weren't relevant to the question at hand that I didn't copy the citation info for.

You accuse me of not reading the papers, and you couldn't even read 9 paragraphs in my reply!!!!

Do you think all those sewage treatment plants and aquaculture facilities were built in the last 10 years? Because if they weren't, they are using old formulas, too.

Do you drive a car with an engine? Because engines are more than 10 years old. Are you using a computer? Because computers are more than 10 years old. What is so sacrosanct about 10 years? When exactly do scientific principles do stale?

And you best tell every single chemical plant on this planet that "mass transfer isn't accurate". Man, all those books about a subject that "isn't accurate". Give me a break. You probably ought to tell your body that, too, since this "inaccurate" phenomena keeps you and me alive.

In fact, saying "mass transfer is in accurate" is just a nonsensical statement. Because there are billions of dollars of materials created around the world based on mass transfer models that are fine.

It is obvious that your mind will never be changed. And this really is borderline trolling. This whole thread needs a serious clean up.