DWC: Are airstones really an effective way to increase DO?

[Classy@Home]

DWC: Are airstones really an effective way to increase DO?

IMVHO - yes...

Fine bubble airstones w/ lots of output have produced some very large, white, solid rootballs in my grows.

I've gotten rootporn extraordinaire with dual 6" airstones in my dwcs.

I'll continue to use them - works for me...

 

[eburna]

I'm not saying air bubbles don't increase DO levels. It's been a few years but I got into the whole super fine bubble thing and for hydro applications it was not as effective as letting the same pump run free with no stone. Honestly I just wasted money on the stones. I remember calculating the amount of air flow per gallon of water to maintain a certain DO level. I did not have a meter but used the kit from Chemetrics. My 'study' was not uber scientific but enough to tell me ditching the stones, increasing my air flow and going with less but larger bubbles made a difference. At the least DO levels rose faster than with the stones.

Pretty sure I had an Alita AL-15A in a 100+ gallon res. That unit puts out .7 cfm. I ended up with 2 open lines instead of two of Alita's corundum stones. Then you gotta figure the depth you are running the stone or airline at to properly calculate output. Solution temperature is also important for influencing/supporting potential DO levels.

Sorry man...my experiments were a basement hydro hack job. Looked at getting a meter but the Chemetrics kit told me what I wanted for that application. Did things like test water DO out of the tap, let it sit for 24 hours, then tested at 48 hours, then pumped air through it, blah, blah.

I was taking a serious look at the tubing Alita offers...the silicone rubber diffuser hose...but after the basic DO testing I did it was not worth the investment. I was gonna run that line all along the bottom of the res. Open lines do the job, don't clog, are less expensive and think it comes more down to total air flow?

If I set up for hydro again I'd run open lines regardless of how much money I had to invest. The venturi option looks interesting though and inexpensive. My main consideration would be controlling the water temp.

That would seem to imply that how small the bubbles are does not correlate with increased DO. Instead, that would mean surface agitation was increased with fewer, larger bubbles. So spending a lot of money (or even any) on generating very small bubbles would seem counterproductive if anything. Just curious, did you observe any direct benefit in your plants growth when you introduced the open airline.

Thanks

 

[Scrogerman]

tagged!

 

[thefatman]

Small bubbles have much more surface area than do large bubbles so they do increase the DO more then large bubbles when considering their contribution below the water surface however the contribution of either bubble size is normally minor in comparison to the DO increases caused by turbulence of the waters surface. However if the surface area is small due to large root masses such as with DWC systems then there is not much surface area for gas exchange so bubbles can then possibly contribute to an increased percentage of the DO increases. The most common natural areas to find super saturated water is at the bottom of large spill ways on damns. Second is likely to be where there are water rapids. Yes louvered/cascade water towers such as used for large building air cooling purposes also increase the DO more then air bubbles below a waters surface can contribute with the bubble length of travel being the same as the drop height of a louvered/cascade tower.

The lesson you posted in part Spurr is a very poorly written lesson as if one is not careful they can go away believing the lesson states that the air bubbles provide more of an increase in DO than does the agitation the bubbles cause at the surface. I have taken many courses in water treatment and waste water treatment as well as courses in the design of water and waste water treatment plants while obtaining my degrees. Aeration by use of air bubbles is principally used rather than pumps in many water treatment plants because they provide three different services however the DO increase by the use of bubbles traveling from the diffusers to the waters surface is smaller than the DO increase caused by water surface turbulence. Typically if oxidation isn't needed to any extent for the waters treatment in nor is the increse of out gassing chemicals in the form of gases (such as Benzene, methane, hydrogen sulfide, or radon) needed dhe treatment process aeration is not provided by bubbles. Efficient waste water treatment plants use air that is oxygen enriched or surface agitation much more than just bubble aeration of compressed air. Very commonly the newer waste water treatment and water treatment plants use paddle or prop type aerators that float on the surface rather than using compressed air pumped through diffusers located on the vessels bottoms.

 

[thinkin]

KISS
Easiest simpliest solution for more DO in water.

double your air pump capacity

If your airstones start to float, thats just enough.
overkill but no doubt getting close to max DO.

But if sound isnt an issue,
go without airstones.

 

[Scrogerman]

KISS
Easiest simpliest solution for more DO in water.

double your air pump capacity

If your airstones start to float, thats just enough.
overkill but no doubt getting close to max DO.

But if sound isnt an issue,
go without airstones.

sorry bud but your 'thinkin' is flawed, it wouldnt make enough differece if you quadrupled it as far as i understand it!??
(ya cant just say double aippump output/?( floating stones etc.wtf)

Bubble it, circulate it, do what you fkin like to it, but once you achieve ya 9-10ppms(under normal atmosphere), you cant get much more without adding/pumping through pure O2 or h2o2. its water temps what count more here.(dont even go there on "2-area)) oy yeah were really covering a large area of res with open ended tubes, lol.

in water culture its root impediment that prevents surface tension break, thats why i laugh at people saying open tubes are best, it doesnt work in bucket DWC or tote ect. in an open recirc res i wont argue.

need to understand how it all works!

when it comes to DO in hydro solutions/systems KISS does not apply! its a complicated subject!

 

[spurr]

Small bubbles have much more surface area than do large bubbles so they do increase the DO more then large bubbles when considering their contribution below the water surface however the contribution of either bubble size is normally minor in comparison to the DO increases caused by turbulence of the waters surface.

Do you have technical data/info I could read on that subject? I will look around for academic info today ... the topic of surface vs. sub-surface infusion of O2 is of great interest to me. AFAIU, bubbles are greatly undervalued in terms of sub-surface DO contribution (infusion of O2 into water), ex., with repsect to this thread.

FWIW, I think with my ADFT system, I should be providing increased DO via. three routs: (1) bubbles; (2) surface aeration (ex., airlift dumping water in top tray, water drain from top tray in rez., and bubbles breaking surface); (3) controllable flow rate (the water in rhizosphere can often be lower in DO than surrounding water, esp. where there is large root mass in deep water, this is why flow rate control is critical to high DO in (and immediately around) the rhizosphere) ... and if I can't get DO high enough, I'll inject pure O2 into the top tray.

However if the surface area is small due to large root masses such as with DWC systems then there is not much surface are for gas exchange ...

Interesting, I had not considered that before. I have never really looked into DWC, but that does make sense.

... so bubbles can then possibly contribute to an increased percentage of the DO increases. The most common natural areas to find super saturated water is at the bottom of large spill ways on damns. Second is likely to be where there are water rapids. Yes louvered/cascade water towers such as used for large building air cooling purposes also increase the DO more then air bubbles below a waters surface can contribute with the bubble length of travel being the same as the drop height of a louvered/cascade tower.

The lesson you posted in part Spurr is a very poorly written lesson as if one is not careful they can go away believing the lesson states that the air bubbles provide more of an increase in DO than does the agitation the bubbles cause at the surface. I have taken many courses in water treatment and waste water treatment as well as courses in the design of water and waste water treatment plants while obtaining my degrees. Aeration by use of air bubbles is principally used rather than pumps in many water treament plants because they provide three different services however the DO increase by the use of bubbles traveling from the diffusers to the waters surface is smaller than the DO increase caused by water surface turbulence. Typically if oxidation isn't needed to any extent for the waters treatment in the treatment process aeration is not provided by bubbles and some time is not even used at all. Efficient waste water treatment plants use air that is oxygen enriched or surface agitation much more than just bubble aeration of compressed air. Very commonly the newer waste water treatment and water treatment plants use paddle or prop type aerators that float on the surface rather than using compressed air pumped through diffusers located on the vessels bottoms.

Good point about the lesson, I hope it didn't come across as if I was suggesting it as evidence that bubbles are the best to increase DO. I posted the lesson as an example of the complex interaction between bubbles and water. Many people in the cannabis world think there is no interaction between bubbles and water, besides bubbles agitating water; they think O2 is not passed from bubbles to water ... I think that is the basis of the cannabis world-centric claim that bubbles don't increase DO.

P.S. thanks for the info about your field of expertise.

 

[Shafto]

Small bubbles have much more surface area than do large bubbles so they do increase the DO more then large bubbles when considering their contribution below the water surface however the contribution of either bubble size is normally minor in comparison to the DO increases caused by turbulence of the waters surface. However if the surface area is small due to large root masses such as with DWC systems then there is not much surface are for gas exchange so bubbles can then possibly contribute to an increased percentage of the DO increases. The most common natural areas to find super saturated water is at the bottom of large spill ways on damns. Second is likely to be where there are water rapids. Yes louvered/cascade water towers such as used for large building air cooling purposes also increase the DO more then air bubbles below a waters surface can contribute with the bubble length of travel being the same as the drop height of a louvered/cascade tower.

The lesson you posted in part Spurr is a very poorly written lesson as if one is not careful they can go away believing the lesson states that the air bubbles provide more of an increase in DO than does the agitation the bubbles cause at the surface. I have taken many courses in water treatment and waste water treatment as well as courses in the design of water and waste water treatment plants while obtaining my degrees. Aeration by use of air bubbles is principally used rather than pumps in many water treament plants because they provide three different services however the DO increase by the use of bubbles traveling from the diffusers to the waters surface is smaller than the DO increase caused by water surface turbulence. Typically if oxidation isn't needed to any extent for the waters treatment in the treatment process aeration is not provided by bubbles and some time is not even used at all. Efficient waste water treatment plants use air that is oxygen enriched or surface agitation much more than just bubble aeration of compressed air. Very commonly the newer waste water treatment and water treatment plants use paddle or prop type aerators that float on the surface rather than using compressed air pumped through diffusers located on the vessels bottoms.

Thanks for the informative post Fatman. I was just reading through all of your nutrient info on RUI, good to see you active here.

From your knowledge Fatman, from what I've read from other's tests on DO with a meter previous to this thread, and since seeing the tests done here by CascadeFarmer (thanks) with the larger bubbles making more surface agitation, and therefore more DO, I'll stick to what I said in the DWC "expert" thread. Surface agitation and surface area are what get you your main source of DO, and therefore pumping water over a bed of hydroton at a rate that recirculates your entire res every 2-3 min, as it spreads out on it's way back, will surely oxygenate your water as good or better than any air stone/diffuser. This coupled with the fact that I saw a very noticeable drop in nute and water uptake from what I presume to be the turbulence/vibration of large amount of air being pumped through the water, leads me to believe that fast water circulation with a water pump is the ideal way to add DO to your system.

Using an "air lift" to pump the water is probably the best of both worlds though, I like that idea. The bubble infusion, however small, would still help, you could keep the turbulence off the roots, just use the air for water movement, and using air to move the water, your iron wouldn't fall out of suspension so fast as it can with mag-drive pumps.

 

[Haps]

OK folks, first, who's talking from experience, and who is typing stuff they read? Here is the straight skinny from 7 years of continuous hydro growing.

Stones are fine, but they do not improve do, I know, it seems like they should, it looks like they do, but it is not the case. Why? Air stones create resistance to your air flow,, so they reduce your flow in a small pump, or increase your heat in a larger one, either way, it is less effective than straight air. There is a thread here, with testing that actually proves that with numbers, if the thread is still here.

I tried lots of stones, expensive and cheap, then I also ran units side by side with stones and bare tube, and the same clones under the same lighting. No difference. And again, and again - cure the crop, smoke the crop, and again. After a year of every test I could think of I ditched the stones, no regrets.

Now I think I will go to the spa and have a tiny asian lady walk on my back and be nice to my front with all the money I saved on air stones the last few years, dig?

H

 

[spurr]

Haps,

This claim is flat wrong: "Stones are fine, but they do not improve do [sic], I know, it seems like they should, it looks like they do, but it is not the case."

I have proven it with a DO2 meter I tested, and countless others have too, including Microbeman and CTguy, as well as thefatman (I think), both of those guys livelihood's depend upon this topic (re DO and bubbles and surface agitation). Not only that, but I posted at least four references to published scientific studies on this topic, all showing bubbles do infuse O2 into water, and quite well (with caveats I listed above (and below), re water quality and bubble characteristics/quantity). There are countess studies all finding the same thing, and explaining why it happens, re bubbles increasing DO sub-surface.

Anyone using those small air pumps and cheap blue air stones from pet stores, or walmart, is sailing on the fail boat already ... IMO anyway

@ all,

Here are (IMO) the most critical facts about efficacy and efficiency of using bubbles (from air diffusers) to increase DO, in terms of sub-surface aeration of water:

(input and corrections are welcome, but please use science and/or examples from testing with DO2 meters; please list water quality (ex., EC, organic matter, temp, etc.) and bubble characteristics, if possible)

• bubbles are small (smaller bubbles have greater surface area than larger bubbles, given the same air mass; greater surface area increases infusion of O2 from bubbles into water, thus increasing DO)
• bubbles are of sufficient quantity with respect to volume of water (number of bubbles)
• bubbles have sufficient (but not too great) velocity
• water is sufficiency 'clean' and cool; re: EC, organic matter, water tension, water flow rate, water temp, etc.
• etc.

That is not to suggest bubbles are better than surface agitation, however, the claim that bubbles do not increase DO, in terms of sub-surface aeration, is flat wrong and needs to die a quick death.

 

[jammie]

right on haps. i run 5 gallon dwc individual buckets and i just attach a small clamp to the airline to let it sink. airstones cause too much back pressure which stresses your pump and decreases the amount of air produced.

 

[ak-51]

Yeah, I've just been using some metal S hooks I had laying around to sink my air lines.

The only problem I have with these is that the huge bubbles coming out will push the roots out of the way. Smaller bubbles will allow the roots to grow in a more natural pattern. Somebody mentioned silicone diffuser hoses, I'll look into those later.

When putting together my bubble cloner I also noticed that a lot of my check-back valves had somehow got stuck together and were severely restricting air flow. I promptly removed them and placed my pumps overhead instead.

This is what they looked like, I highly recommend not using them:

 

[CascadeFarmer]

Haps,

This claim is flat wrong: "Stones are fine, but they do not improve do [sic], I know, it seems like they should, it looks like they do, but it is not the case."

What I got from Hap's post was that if you have an air pump it will be more efficient/effective in increasing DO levels running open lines compared to that same pump with a stone on it. That's how I feel and seems to be the case based on that rudimentary testing I did years ago. The Chemetrics kit is cool and provided me with actual data. Tough to use that kit in an organic based nute system though due to solution coloration. It was easy for me when using GH 3 part.

airstones cause too much back pressure which stresses your pump and decreases the amount of air produced.

For sure more difficult for a pump to push air through a stone but then just get a higher quality pump.

 

[FreezerBoy]

I've heard the suggestion that airstones do not actually increase dissolved oxygen and that oxygenation occurs through surface agitation, therefore airstones really only work to circulate water. If so, is there a more effective way to increase dissolved oxygen in a DWC?

Stones agitate and, yes, surface agitation is where it happens. However, their true worth is stealth.

Waterfalls are the most effective means (two agitated surfaces crashing violently through a third, no bubbles involved) but, waterfalls are big and loud. Airstones are tiny and quiet. If your stealth requirements allow you to use big, loud waterfalls, do it. If you need to restrict sound and space, airstones work fine.

 

[Haps]

Not likely to die. My only factual knowledge comes from growing ganja, and doing experiments and evaluating real results for years. I do not doubt your data, but data has a funny way of not showing the whole picture, which in this world means results.

The reality at the root zone, is that any effective air pump delivery combo should deliver more than enough do to be at max at all times. Stones are fine, just an extra, unneeded componant for me. And data can be used to show any result you want, hehe, so bottom line is results say either way works well if done effectively. My roots love to dance.

H

 

[thinkin]

chasing fractions or big easy gains

chasing fractions or big easy gains

Goal is to get more oxygen to roots.

Dissolved Oxygen isnt complicated.
Simple science.

With or Without airstones:

Test results favor running without an airstone because airstones restrict(friction) amount of air being delivered to water. All the tests use same air pump. Thus, "without" wins hands down each time.

Chasing small gains by using airstones/waterfall/waterwell/h202/surface tension methods......
Might as well go aero, if you putting the time in.

MEANWHILE.
Double or triple amount of oxygen feed to the roots by adding an additional airpump(s). You hit max DO and still the bubbles (that dont dissolve) feed oxygen to the roots. (think aero)

If you are going to use an airstone, recommend big round disk shaped airstones.

 

[Scrogerman]

yeah in an open res, what about in a RDWC bucket/Tote?(80% full of roots), but once

again its tempreture that counts on DO content bro! delivery is one thing, constant(penetration) is another./

This has to be prolly my favorite subject with hydro growing! booommm every time!

 

[GP73LPC]

interesting thread.

i'm growing some jalapeno's in dwc, i think i will remove the air stone. no stealth issues there...

 

[delta9nxs]

you are all right. a still glass of water that has had all free o2 removed from it will still reach saturation due to atmospheric partial pressures.

the trick is keeping up with depletion caused by living organisms and decaying organic material.

so any of these methods can work as long as they achieve and maintain saturation under your particular set of variables.

saturation is saturation and it really doesn't matter how you get there.

 

[Microbeman]

I can only speak to testing done in vessels of water and applied to a variety of compost tea brewer designs. I built and tested almost every brewer design known to mankind, all the way from half a gallon to 1200 gallons. I used always two dissolved oxygen meters for my test results, not some dorky kit which is admitedly not up to snuff. I can state absolutely that the use of quality medium bore air stones, which produce large, medium and small size bubbles produced consistently a higher dissolved oxygen content than open tubes. If you are talking cheap aquarium stones, right, they restrict flow. Quality glass bonded diffusers allow open flow. The gas exchange does occurr mostly at the surface as several have pointed out. As CO2 is discharged O2 is infused (dissolved) = gas exchange. If there are smaller bubbles, there is also some infusion of O2 on the way to the surface because the surface area is increased and it takes longer to get there; not rocket science. As fatman has kindly pointed out, in some streams and near waterfalls water can become superstaturated with oxygen. No it is not limited to a maximum at certain elevations and temperatures, Sherlock. That is just in natural occurring circumstances. I've had DO2 at 11 PPM at 2400 ft above sea level at 72 degrees F.