DIY Tea-bubbler

[Microbeman]

Could you elaborate a little please Microbeman? I've never heard of "Organic Gem" before. Thanks.

Just a brand name.

 

[neongreen]

"as the majority of gas exchange occurs at the water surface to atmosphere interface where CO2 is released. Dissolved O2 (DO2) in water is dependent on the release of CO2."

I think that this is true for natural bodies of water, but a brewer is not a natural body of water. To be specific, in natural bodies of water you don't get air pumped into it via air-stones in copious quantities.

I know DCO2 plays a part, but I think you are blowing it's effect out of proportion.

It's comparable to the difference between DO2 in a very shallow/fast flowing stream versus a deep, and relatively sluggish flowing stream. I realize you usually get an increased surface area to volume ratio with the shallow stream, but that is only half the story.

Therefore the column shaped brewer theory has some merit but the diffusers and air applied to a similar volume of water with a larger surface area would likely produce a higher DO2.

But, no one knows for sure...

I wish I could test it myself, but I don't have the DO2 meter. I'm going to see how much they cost.

If the column were emptied back into another container and broke the surface in the act, then you'd have multiplied
DO2. Sounds kinda like my brewer.

I'm with you on that.

It would be impractical, but I think you could get great results by pumping the water up 10 or 20 feet, and letting it fall along a partly open (at the top and bottom) pipe. That would be a bit extreme, but the greater the distance the water has to fall, the better DO2 will get. Try raising the height on your brewers by a couple of feet, and I'm sure you will see a difference

 

[neongreen]

Just a brand name.

Thanks. I'll keep an eye out for it.

 

[maryjohn]

Thanks microbeman for such a lucid and parsimonious response.

Although why do I get the feeling natural bodies work just like a tea bubbler? That's why plankton are losing their shells. CO2 dissolved at the surface is turning into carbonic acid faster than convection can take it down to be buffered by the layers of dead shells. It's part of what is killing our oceans.

 

[Microbeman]

I think that this is true for natural bodies of water, but a brewer is not a natural body of water. To be specific, in natural bodies of water you don't get air pumped into it via air-stones in copious quantities.

Regardless, the exchange can only take place at the surface with the exception of a minor amount infused from bubbles traveling.

I know DCO2 plays a part, but I think you are blowing it's effect out of proportion

What is DCO2? Do you mean dissolved CO2. It has everything to do with it. The water cannot hold dissolved
O2 without releasing CO2. Just like you can't drive a car down a street filled with stopped traffic.

But, no one knows for sure...

Actually lots of people do. An O2 meter is $300 and up.

Try raising the height on your brewers by a couple of feet, and I'm sure you will see a difference

I've already calculated my riser height against CFM output of my pumps for maximum efficiency. I designed a 1000 gal. brewer last year for a ranch with two 96 inch air lifts.


In nature DO2 is just sustaining life. In an ACT brewer we are super saturating with DO2. This is necessary to counter the huge CO2 emissions when bacteria multiply.

How is the surface of a bubble any different than the surface of water?

One is surrounded by water and has less space for CO2 to go. Had to answer that.

 

[judas cohen]

In the summer, ambient air at my desert location is 110F+....My DO must be really low with water at that temp. Can I make compost tea in 1 gal container using dual port $11 airpump from walmart? or is it just a nutrient tea with very little BB/mycorrhiza.....

(I don't have a microscope or money to have tea analyzed.) TIA!

 

[neongreen]

judas cohen just hit the nail on the head. If anything, temperature has more effect on the water's ability to absorb O2.

judas cohen, I would say there is a good chance you would run in to problems with low levels of D02. I'm afraid I have no idea what would be the optimum temperature. Perhaps Microbe man has some answers, but I'm pretty sure you need to the the temperature down, at least a bit for making tea, and get a good pump to try and make up for the increased temperature.

 

[neongreen]

Regardless, the exchange can only take place at the surface with the exception of a minor amount infused from bubbles traveling.

Sorry, but that is wrong.

If that is the case, and air pumps + diffusers do not deliver significant aeration, then why are they so popular?

What is DCO2? Do you mean dissolved CO2. It has everything to do with it. The water cannot hold dissolved
O2 without releasing CO2. Just like you can't drive a car down a street filled with stopped traffic.

Yes, I mean dissolved CO2.

I think you're overstating the effect again. The sort of DCO2 levels that would
inhibit the ability of water to absorb O2, would not usually be reached, given sufficient aeration, and I suspect by that time your dropping PH would have affected the brew adversely anyway.

Actually lots of people do.

Well, you just said that it was "likely" implying that you are not sure... but now you are? Any chance of a link Microbeman?

An O2 meter is $300 and up.

Thanks. That's out of my price range right now unfortunately.

One is surrounded by water and has less space for CO2 to go. Had to answer that.

A bubble is just air on one side and liquid on the other, just like the water surface - air on one side and water on the other. Diffusion between the water air boundary in a bubble occurs in just the same way. Yes, one surface is curved and smaller, but that does not change the physical properties of it to any significant degree compared with the other.

Because you are constantly making new bubbles, CO2 is constantly being removed, just as O2 is being deposited. Sure there is more DCO2 in the water than normal due to the microbe-bloom, but decent aeration will take care of that. Remember, you're pumping in liters of tiny air bubbles every minute. In my case, a 1 gal brew of bacteria even at their most active, is not going to produce anything like a liter of CO2 in a minute, wouldn't you agree?

I did a little searching and found some info:

First we must understand some basics of gas (air) exchange with regard to water. Contact time is critical, the longer the better. Water oxygenation levels are increased only when the water is in contact with oxygen or air. So the surface of the pond is a significant gas exchange area because the water surface is in contact with the air all the time. The effectiveness of the water/air interface can be increased by water movement at the interface, i.e., jets, venturis, waterfalls, fountains, air stones, etc. Another example of contact time is when you use air stones, if they are
put on the bottom of the pond, the air bubbles rising to the surface are in contact with water for much longer time than if they are only 6" under the surface. There are theories that conclude that most of the gas transfer happens as the bubble is forming. (A series of related articles on the subject can be found in the “Odds and Ends” section [by Joe Cuny] of Koi USA, Jan/Feb ‘99 thru Nov/Dec ‘99.) An added benefit to deep air stones is that as the bubbles rise to the surface, they draw bottom water toward the surface in addition to adding surface movement. Now a surprise to some people is that the finer the air bubbles, the greater the gas transferred. This is
because the smaller bubbles have a greater surface area for a given volume of gas. The smaller bubbles also rise slower than larger bubbles that increases the contact time.

http://tinyurl.com/cvb29m

Notice no mention of CO2, since it is one of the least important aspects in the equation, and it's the same with everything else I found, from commercial brewers, to fish ponds, to waste management operations.

Vacuum Bubble® Technology Aeration

The Vacuum Bubble® Technology Aerator, instead of using the compressed air/fine pore system, uses a patented process to create bubbles in a partial vacuum. The micro Vacuum Bubbles® created in this process average 0.25 mm in diameter. The small size of the bubble and the low-pressure gas it holds create a small buoyancy force (The phenomenon which makes bubbles rise in a liquid). This buoyancy force is so small that it is less than the surrounding surface tension of the water. The bubble, in fact, does not rise to the surface, but remains suspended in the fluid. This makes all of the oxygen in the bubble available to be dissolved in the liquid as needed.

http://tinyurl.com/c8ojrt

Types of aerators
There are many types of aerators: gravity, surface, diffuser, and turbine types. Sometimes the aeration is a mix of these. They all work on the principle of increasing the surface area of the water and mixing with air to speed up the oxygen transfer into the water.

http://tinyurl.com/cwy4v7

As I said, bubbles effectively increase the surface area of water.

It's all about surface area.

That link has some interesting ideas you might like to look at.

Contact Time of Bubble to Water
Of prime importance in aeration is the speed at which the bubble rises to the surface.
slower speed increases contact time with water
faster speed decreases contact time

Fine bubbles rise to the surface significantly slower than coarse bubbles. As bubbles rise to the surface they drag water behind them creating friction. Since fine bubbles have a greater surface area than coarse bubbles, the friction is greater and the bubble will rise more slowly. This increased period of time in which the bubble is in contact with the area allows more oxygen to be dissolved into the water. This provides better overall water quality.

http://tinyurl.com/cxdbe5

Again, it's all about surface area in contact with water.

"Some insects have adapted to life underwater by using this bubble as an external lung," said John Bush, associate professor of applied mathematics, a co-author of the recent study.

http://tinyurl.com/caa7mq

Remember my comparison with air bubbles and lungs? This professor seems to think it's valid.

The bubble size affects the oxygen transfer efficiency. Smaller bubbles have more surface area per unit volume. This provides more area through which oxygen can diffuse and thereby increase overall transfer efficiency. Visualize a basketball filled with ping pong balls. Both take up the same volume, but the ping pong balls have a much greater cumulative surface area. Also, since fine bubbles provide larger total surface area, they create more friction and rise slower than coarse bubbles. The combination of more transfer area and a greater contact time enhances transfer efficiency.

http://www.lagoonsonline.com/finebubble.htm

With such a high number of free surface areas in a tiny volume of cell, it confers upon the bacterial cell a very high surface area to volume ratio. This very high surface area to volume ratio allows maximum or optimum surfaces for diffusions or molecular exchanges to occur between the microbial cell and the environment. No matter where the molecules are, they are easily accessible for diffusion into the microbial cell.

Compare this with the elephant which is such a huge animal. which has a very low ratio of surface area to volume ratio! If nutrients are to diffuse through the surface area of the elephant it would not be enough to supply every cell of the elephant!

http://tinyurl.com/cslp8p

This is talking about the same principal, but in a slightly different context, although we are still talking about bacteria. By pumping air bubbles into a constricted space (tube in my case), I'm basically increasing the air to water ratio. The closest distance in any part of water to the nearest air bubble is significantly less than in a less constricted vessel. This means air diffuses into the water faster, as it doesn't have to travel "through the whole elephant" to get there.

Furthermore, if fine bubbles are generated by a suitable diffuser from depth, their large surface area creates a drag against the water, reducing vertical velocity increasing contact time further. An added benefit of this "drag" experienced by a rising column of fine bubbles is the mixing and circulation of significant volumes of water. This mixing action enhances water quality by making the pond a well-aerated, homogenous and stable environment.

http://tinyurl.com/dfww8j

I think I've proved my points, but if you or anyone else can offer evidence to the contrary, I'm all ears.

Can we move on now?

 

[Microbeman]

Hi Neon,

Just to clear a couple of things. You do know I stated the small bubble and increased surface area, right? and that I concurred with the surface area of lung tissue? And I do maintain there is a small infusion of O2 as the bubbles rise?

Now, I have looked over the site you linked and do not see that it adequately addresses the gas exchange and surface tension of water. Perhaps I missed it in my haste. I am very busy and am short on time.

First let's try the common sense approach again. The word exchange means that something is being exchanged for something else. In our model CO2 is being exchanged for O2. There is no doubt about this and any astute scientist will verify this. In a brewer or an aquarium the only place for this exchange to become complete is at the surface unless there are plants or other CO2 using organisms.

I wish there were a lot of Internet resources freely available but there are only expensive journal articles and text books which really spell this out.

From an experiential plain, I have had up to 30 aquariums at one time and quickly learned that the water returned at the surface from the filtration system did a superior job of aerating compared to the air stones. Any serious tropical fish raiser will verify this.

I have researched this (DO2) extensively over the past 6 years and measurements taken have validated this.

As for copious amounts of bacteria in a gallon. Well I easily see 100,000 in a drop which is 1/20th of a ml. all the time. Look at some of the video on my webpage.

You provided me with a rather junior little website so here are some equally junior sites for you to peruse. I recommend you read up on gas exchange.

Properties of water;

http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/water.html#c1

Surface tension

http://hyperphysics.phy-astr.gsu.edu/hbase/surten.html#c3

CO2

http://www.syngnathid.org/articles/oxygenSaturation.html
Surface

http://www.planetcatfish.com/shanesworld/shanesworld.php?article_id=313

“ http://www.rsc.org/education/teachers/learnnet/cfb/gas.htm

Gas exchange occurs as a result of respiration, when carbon dioxide is excreted and oxygen taken up”

This explains it pretty well. It even mentions that tall skinny aquariums do not maintain DO2

http://books.google.ca/books?id=OZX...jEh_Tzk&sig=dJsGM5vbB_OxqDOMfjzR2_1s42k&hl=en

 

[Microbeman]

If that is the case, and air pumps + diffusers do not deliver significant aeration, then why are they so popular?

The majority of the aeration from air stones is from bubbles breaking the surface tension where the gas exchange takes place. They also contribute to the circulation of the water. That is why. I know that 'good quality' airstones are efficient. I just discontinued them in my brewer because they require acid for cleaning. I replaced them with diffusers I designed and had machined. Auburn University has some info BTW.

 

[Microbeman]

Neon,

On my lunch break I looked up a few more links for you.


Aquarium Info:

http://www.wetwebmedia.com/FWsubwebindex/fwaerfaqs.htm

http://www.bestfish.com/tips/070899.html

http://www.oursimplejoys.com/freshwateraquaria/01-freshwater-aquarium-setup.html

http://www.tropicalfishcentre.co.uk/Filtration.htm

http://www.fishlore.com/aquariummagazine/oct07/fishbeginnerpart2.htm

“ http://badmanstropicalfish.com/articles/article70.html#3

3. Aeration means only adding air, or more specifically, oxygen to the water. Long ago, filters were far less efficient and moved far less water than those we use now. Airstones had a functional place in the hobby. Current filter construction and design is likely to provide quite enough filtration and aeration without the need for airstones. That statement does presume that the filter is properly sized for the setup, and properly maintained. Airstones today are more décor than functional requirements in conventional tanks. “

[Most of these articles say something similar. MM]


http://www.ratemyfishtank.com/articles/104

By Robert Lashlee
In nature, fish live in oceans, lakes, ponds, and rivers. These bodies of water all have large surface areas and sometimes large currents as well. This serves to oxygenate the water so that fish survival is possible. However, in an aquarium, the surface of the water is greatly reduced. Therefore, artificial ways of oxygenating he water must be accomplished through aeration. There are several ways to aerate your aquarium and these methods will be discussed in this article.

Before discussing specific methods, it is important to address the surface area of the water surface in your aquarium. The greater this surface area is, the more water that is in contact with the air at any given moment. This leads to greater oxygen absorption by the water. Therefore, you should try to maximize the surface area in your aquarium. People sometimes think, “If I can put x number of fish in a 20 gallon, then I should be able to put the same number of fish in a 20 gallon tall aquarium.” However, the 20 gallon actually has a larger surface area due to its length and width dimensions. You need to be careful with tall tanks or irregularly-shaped tanks (such as hexagons) as the water surface can be fairly small. This smaller surface limits the stocking capacity of the aquarium.

[Sounds like the science you applied to your design. MM]

Oxygen/Carbon Dioxide Exchange Basics
At the water’s surface, oxygen and carbon dioxide are exchanged. Carbon dioxide goes from the water to the air. This is important because the carbon dioxide concentration in the water is raised as it is produced by fish. The fish would die if the CO2 was never allowed to escape into the atmosphere.
While CO2 is going from the water to the air, oxygen is going from the air to the water. This is important as it provides oxygen to the water that is needed by fish.
For this gas exchange to occur, the surface tension of the water must be broken. Agitating the surface breaks this surface tension and allows for a proper exchange of gases.

[Does this sound familiar? MM]

Air stones
Air stones are connected to pumps to produce bubbles in an aquarium. Many think these pumps are too noisy and, therefore, choose not to use air stones. However, placing the pump on a sponge will usually dampen the noise significantly.
Some hobbyist really like the look of a bubble wall in their aquarium and, therefore, use them even when further aeration is not needed. You can really add a nice look with these devices.
Air stones are placed in an aquarium to produce bubbles. It is not actually the bubbles that provide the oxygen to the water (a common misconception), but it is their disturbance of the surface and ability to provide more water circulation that helps to raise the concentration of oxygen in the tank.

[A common misconception. Why did I not think of that? Were you all ears? MM]

 

[neongreen]

Hi Microbeman,

Thanks for your reply.

The word exchange means that something is being exchanged for something else.

Yes, that is true, but technically the term "gas exchange" means:

The diffusion of gases from an area of higher concentration to an area of lower concentration

.

It can also mean that one gas is "exchanged" for another.

From an experiential plain, I have had up to 30 aquariums at one time and quickly learned that the water returned at the surface from the filtration system did a superior job of aerating compared to the air stones. Any serious tropical fish raiser will verify this.

It makes more sense to lift water and return it when you are breeding fish on a big scale, I agree. But you are not trying to super-saturate fishtanks with O2.

I have researched this (DO2) extensively over the past 6 years and measurements taken have validated this.

I can appreciate that, but is there a chance you could have overlooked something, misinterpreted something? I think so. I am just trying to point out those areas. I studied this subject at degree level, albeit a while ago. I think I know what I'm talking about.

As for copious amounts of bacteria in a gallon. Well I easily see 100,000 in a drop which is 1/20th of a ml. all the time. Look at some of the video on my webpage.

According to this link:

bacteria weigh about one trillionth of a gram ( about 400 trillion bacteria per pound)

http://www.nairaland.com/nigeria/topic-873.0.html

Using that figure, by my calculation, a 5 gal brew with the numbers of bacteria you quoted, would contain about 45 grams of bacteria. That's about the same weight as a couple of packs of cigarettes. I can't find numbers, but I doubt even 45 grams of bacteria would produce more than a liter or two of CO2 per hour under optimal conditions.

This explains it pretty well. It even mentions that tall skinny aquariums do not maintain DO2

Of course they do not, but then you are not pumping in multiple liters of air per minute.

-

Most growers here have relatively small grows, and although it's good to have surface area, that takes up a great deal of room, which is not practical for most growers.

My design tries to address the problem of getting enough DO2 into the tea without having to outlay too much on a powerful pump. I believe it achieves these goals.

I don't mean to tread on any toes here, just work out which designs work best for small grows. The work you have done and info you have shared is great, but I think it translates better to larger scale brewers.

I'm going to have a look at the links you posted now - thanks for posting them. I agree, that it's become very hard to come by solid info on the subject. It's a shame

 

[neongreen]

That is why. I know that 'good quality' airstones are efficient. I just discontinued them in my brewer because they require acid for cleaning. I replaced them with diffusers I designed and had machined. Auburn University has some info BTW.

Interesting - thanks, Ill look into it.

"Airdomes" sound promising. Any experience with those?

 

[neongreen]

. You need to be careful with tall tanks or irregularly-shaped tanks (such as hexagons) as the water surface can be fairly small. This smaller surface limits the stocking capacity of the aquarium.

[Sounds like the science you applied to your design. MM]

In an aquarium situation, it's obvious you'd run into problems without much surface area, as well as little aeration, but the whole point I'm trying to get across here, is that you can more than make up for the loss in surface area, by sending in a large (not necessarily huge) amount of air in the form of small air bubbles, and prolonging their contact with the water.

I think you're missing how significant the difference is.

Off to read over your links now. Thanks again for posting!

ng

 

[Microbeman]

Of course they do not, but then you are not pumping in multiple liters of air per minute.

I believe your's pumps 3.3 lpm = 0.117 CFM/ 0.08 = 1.46 gal efficiency

 

[Microbeman]

FYI, I've recorded the DO2 go from 8 PPM to 2 PPM in a period of 2 hours from a bacteria/archaea bloom in a 50 gallon brewer with numbers similar to that previously mentioned. Whether in a 1200 gal or 1 gal brewer the ratio (count) of bacteria/archaea per ml remains pretty much the same if the ratio of foodstock is the same. I would be willing to bet $500 that if I used the same pump in a 12 inch deep container utilizing my simple air lift formula (without air stones) that my container would measure a substantially higher
DO2.

 

[maryjohn]

ok, at some point someone has to say "neon, you should pipe down, take a seat, and listen. This dude knows what he is talking about, and chances are you are probably not the super-genius who will turn accepted science on its head. See Plato's Republic, dialogue between Socrates and Thrasymachus.".

Really dude, you should be very grateful for such a patient teacher willing to explain all this.

 

[neongreen]

I would be willing to bet $500 that if I used the same pump in a 12 inch deep container utilizing my simple air lift formula (without air stones) that my container would measure a substantially higher
DO2.

I would not be surprised if it did, and I never said it would not. To be honest I had not even considered air lifts before you mentioned them.

ok, at some point someone has to say "neon, you should pipe down, take a seat, and listen. This dude knows what he is talking about, and chances are you are probably not the super-genius who will turn accepted science on its head. See Plato's Republic, dialogue between Socrates and Thrasymachus.".

Really dude, you should be very grateful for such a patient teacher willing to explain all this.

I never claimed to be a "super-genius", and I'm certainly not trying to "turn accepted science on its head". If everything in this world was considered 100% satisfactory and efficient, there would never be any new invention, but it is not, and there is nearly always lots of room for improvement.

So far no one has shown me definitively that the combination of things I have thrown together does not work. This was never supposed to be a "be all to end all" design anyway, but hopefully a step in the right direction. Perhaps, I should have made that a bit clearer at the start of this thread, but in my hurry to complete this thread I may have overlooked that.

I can see that Microbeman knows what he is talking about in general, but no one is perfect, and even the best make mistakes. I've thanked him for his continued contribution to this thread/subject throughout, but we obviously don't see eye to eye on a few points, although I do agree with the vast majority of what he says. Thank you again Microbeman.

I want to try and draw on the best of everyone's ideas here, so hopefully we can move on now...

I suppose if you really wanted the best aeration possible, you could use both the lift and a diffuser, so you're aerating from top and bottom, plus driving bubbles/water in both directions, which should increase turbulence and pressure, which should in turn mean better O2 diffusion.

Anyone else have bubbler ideas or designs that they care to share? Feel free to contribute them if so - and we'll try and tear them to pieces (only joking)

 

[Microbeman]

This will be my last entry in this thread. Certainly I can be mistaken as is indicated in my signature. I am always willing (& anxious) to admit the world is not flat when it has been proven not to be so. Neon, you are stubbornly holding on to a premise which in all appearances does not exist. I do not believe people should think they can build on this premise. I did say I thought your design would fulfill your needs but it is not efficient. All water O2/CO2 gas exchanges call for atmospheric interface. The ones who do not know what it is, use phrases like gas transfer.

BTW in your 2nd to last paragraph you describe my design.

 

[maryjohn]

So far no one has shown me definitively that the combination of things I have thrown together does not work.

In 6 months when you are not so invested in this, take another gander at the thread.