The - Dissolved Oxygen - think tank thread

[The Groff]

Hello IcMag!

New around these parts, so please dont bite!

I've recently upgraded from coco to RDWC, undercurrent style, though I think mine is waaaaay cooler



Anyway, doing tons of research, lots of questions pop in my mind to make our lives easier, better, cheaper, more silent, healthier etc etc...

I think I've got a pretty solid knowledge already on the subject, from Henry's Law to excessive aerobic depletion (too much tea etc), temperature control and even salt concentration, elevation, pathogens etc etc etc.. and how they influence the over saturation of 02 in H20 and provide all the goodies we love giving our root zone.

But, what I cannot find for the life of me is one piece of information that can effectively revolutionize our methods potentially making our lives easier and cheaper.

Unfortunately, DO meters that are actually useful are way too expensive. How I wish I could have one to test all my hypotheses...

My goal is to get rid of the airpump = less noise, less disease, lesser H20 heat, less maintenance, less electric cost etc etc.

The question being;

If all conditions remain equal, (water temp, pressure, recirc flow etc..) - once you oversaturate the water with oxygen - if the airpump is shut-off, how long will it take for the water to un-saturate back to baseline environmental DO ?

Why the question?

- Any decent RDWC will recircs at least about 6 to 10x the hour. That means that all the water flows around once every 6 to 10 minutes.

- At 19ºC (66ºF) maximum saturation of pure water is around 9mg/L, at sea level with 0.00ppm salinity (basically, RO water)

- RO, or even tap water, should be (extremely variable I know...) 4 to 7ppm from what I've gathered... lets say 5ppm

- So imagine we increased 4ppm, using airpumps, to raise DO from 5ppm to 9ppm. Imagine for a second that you turn off the airpump... how long would it take for the water to go from 9ppm oxygen back down to 5ppm?

Because, if it take longer that the time it take to recirc the system 1x (around 10 minutes) - then we are wasting electricity (both airpump and chillers), producing heat, introducing pathogens, making lots of noise, and basically doing very very very little for plant health.

I've only found 1 semi-scientific paper that addresses it. They were comparing 3 distinct methods for determining DO. With all three methods, I was shocked at how long DO lowers - check it out.



It suggests it takes about 24h to go from 7ppm down to 6ppm of DO.

If this this is true, we seriously have to address the whole airpump practice. Essentially, we could oversaturate just once or twice a day for a few hours, using either airpump, waterfall, whatever.

I have always been much more inclined to do flooming (correctly spelled fluming) - and for those who argue about bubbles and water movement/mixing - fluming does a heck lot more of it too.

Its not really about the cost for me, it more about noise and heat to be honest...

wadda'ya think?

 

[bayarea925]

Are you using organics? If not try h2o2 my mom plants are loving it sence my switch. They are jumping off like never before.

 

[willyweed]

water may take 24 hours to come down from 7ppm to 6ppm. but the said water does not have a plant taking the o2 out of the water ! i have been told you only need 1 watt of power per gallon .if you have 4x 3gal buckets and one control bucket the same size , a 15-20 watt air pump should enough ! that's less than a normal house light bulb !
with regards to the noise + vibration of the air pump, build a small sound proof box out of sound proof plaster board(gypsum board) ,very cheap to buy! and if the noise is still too much, build another box slightly larger and place the first box in it. it will be a bit fiddly with the cables and airlines ,but a very cost effective solution to the problem of the sound and vibration. all the best ww

 

[The Groff]

Well, thats the thing. Wouldnt putting the airpump in an isolation box make the water temperature rise even more? The heat put off by the airpump would go right down the airline. Thats like having an extra 30-40w of heat pumped right in. A little rise in temperature is a huge decrease is dissolved oxygen. That will make the chiller work more, heating the surrounding air even more, endless loop of consumption. I can also hardly believe that low frequency drone the pumps make "silent".

Oh yeah, please note I'm in the super stealth growing gang *shhhh*

Little 500L/h powerheads consume something like 4.4w, and completely silent under water.
The whole idea when hydro was developed was to "pump oxygen" and "stir nutrient mixes". But when looking further into it, I was soon lead to koi forums, where fish science plays a key role. Everywhere, fluming is prefered to airpumps for oxygen induction/general health.

RDWC comes from DWC, so the principles are applied. Therefore obviously airstones are a tried-and-tested brainless option, does 2 in 1, introduce air and stir the mix. But since in RDWC we have a head/brain pot (not in DWC), with a dedicated recirculation pump, and since most designs for this return pump is either waterfall or fluming back to the rez... is it really necessary to have an airstone in very bucket?

If dissolved oxygen really holds its saturation that long (24h 1ppm), then a constant source of saturation would be enough to compensate for the metabolic action of the roots. I argue that the headbrain might be more than enough to saturate the water with all the DO the system needs.

But once the plants get big and fills out the bucket with roots, then a passive recirc flow will certainly not cut it to deliver properly mixed nutrient mix. Thats where a dedicated powerhead per bucket comes in to force the mix up through the roots. From the little I've seen on my system (800L/h return pump flooms back into a 27L bucket) I dont thing the water pressure is too strong for the developing roots.

So taking it a little bit further, if we give each bucket its own little 500L powehead angled upwards, it would definitley stir ALOT more water around than airstones, and also add more DO according to koi forums.

In a 4 pot system, that would be

4.4w x 4 pots = 17,6w - Less than half the heat produced by an airpump, more DO, silence.

I'm going to test this in the future, my hands are tied right now. Need to look more into it of course, the term is "oxyfertigation" in horticulture if anyone is interested joining the fun.

If anyone out there has already has 0.02c to share, I'll gladly take it

 

[willyweed]

yes it does make the temperature rise,but it does give you more freedom to move the pump outside the room, i personally use silica and h2o2 so the minimal temperature increase is more that covered by this
also if you grow at night, the temps are not so much of a problem!
have a look for snype on the boards he does many systems on here, rdwc etc and would be one of the top people to ask on here ,and he is also very helpful .i can only confirm what has worked for me! he may be able to give you a better insight into what you need or what will work best for your situation ! all the best .ww (farm life with snype)

 

[Snype]

If dissolved oxygen really holds its saturation that long (24h 1ppm), then a constant source of saturation would be enough to compensate for the metabolic action of the roots. I argue that the headbrain might be more than enough to saturate the water with all the DO the system needs.

Plants roots take that oxygen and the DO decreases. Some type of fish can live at 2 PPM DO while other types of fish die at those levels. I believe plants could act a similar way so some plants may need more DO to thrive than others.

You keep talking about over saturation but once you get to saturation, you can't go over it with the methods that you are stating.

The amount of electricity that you would save from not running an air pump seem very small. Just like Willy said above about a watt per gallon. Personally, I use closer to 2 watts per gallon. I also think that the type of air pump that you use will also matter. Those cheap grow shop pumps are just garbage. I use Alita pond pumps instead and when you compare an Alita to the one at the hydro shop with the same output, it doesn't move the water the same. The grow shop pumps use high pressure while the Alita uses low pressure. I did many DO tests a couple of years back and I'm still using my air stones and air pump in my RDWC. I keep my air pump in a cooler room that there are no plants in. For every 2,000 watts of lights have 10 plants which need 60 watts of Air from my pump. 60 Watts for an air pump to run 2,000 watts is not a big expense to know you are getting all the air that your need. It is much better to try and keep your plants at saturation and for that to happen, you need to keep the pumps on 24 hours per day. Even if you did have some waterfall ideal for all the other buckets instead of airstones, you would still need another pump to create all those waterfalls which would bring you more electricity just like the air pump.

 

[The Groff]

Good point Snype... thanks for the input.

Yeah, some fish like lots of oxygen and live is very cold water. Tropical fish adapted to very low oxygen levels. Plants also vary alot, but we all know how they're tough little bitches. From the high Hindu Kush mountains to the blazing equatorial sativas. Swap them round and they'll still go at it strong.

When I said over-saturation, I dont mean saturation over 100%, though it is possible. Its called super-saturation and you'd need a compressor and pressure chamber, and a fasts decompression/heating chamber... and lots of lab equip or seriously good DIY skills.

I mean saturation above baseline DO levels. Baseline saturation is somewhere around 50% at worse.

That means that at 19ºC (66ºF) the "normal" oxygen concentration is around 5 to 7ppm, while the theoretical maximum 100% saturation at 19ºC = 9ppm

So at the very best, we're pumping air to raise 2 to 4ppm. That number can also be achieved by lowering the water temperature by 1 or 2 degrees with the chiller. Heck, before I got the chiller I was forzen-water-bottling the sysyem and could pretty much keep it swinging between within a 3ºC margin, so I could to 18-20ºC

So far I've found that its below 16ºC that roots really start to hinder development, and completely stop below 10ºC. That is a comfortable margin.

I do have 2x Hailea 9820 (60L/m) and two Charles Austin ET30 (25w 30L/m) that came with both my RDWC systems, so my problem is not in pumps or electric bills. You are right about the cost, its not significant, but in terms of heat and noise it is. I also use silicon, but not H202.

In light of all this, it just seems to me an excessive effort, even considering that plant do suck up oxygen, so much effort to maintain a mere 2 to 4ppm of oxygen. How I wish I had an oxy meter...

What I am trying to get at is, in the same way there are dozens of products readily available to fight diseases, produced and tested over years... yet in the end the elegance and simplicity and effectiveness of bennies is undeniable and seem to kick industrial chems in the nut.

Snype, I think I remember a thread of yours long time ago, and the DO discussion. Would you mind giving me a quick run down on what you found using the DO meter?

 

[The Groff]

Sorry, I'm a bit tired, need to sleep... let me re-phrase that last bit

What I am trying to get at is, in the same way there are dozens of products readily available to fight diseases, produced and tested over years... yet in the end the elegance and simplicity and effectiveness of bennies is undeniable and seem to kick industrial chems in the nut.

So maybe, now that we're 40 years down the road since modern day hydroponics, we can look at it a little different. There were no water chillers back in the 60's for instance. One of the reasons airpumps were introduced was exactly because of raised water temps depleting oxygen, not to increase oxygen to make roots happy.

But again, I am far more interested in knowing what you found out when you had the DO meter Snype!

 

[Snype]

Sorry, I'm a bit tired, need to sleep... let me re-phrase that last bit



So maybe, now that we're 40 years down the road since modern day hydroponics, we can look at it a little different. There were no water chillers back in the 60's for instance. One of the reasons airpumps were introduced was exactly because of raised water temps depleting oxygen, not to increase oxygen to make roots happy.

But again, I am far more interested in knowing what you found out when you had the DO meter Snype!

I found that waterfalls can work in the right situation. It works great for E&F if you take your screen and riser fitting out of the tray and don't use it. I don't have to use airstones in those systems. But for me in RDWC it I found airstones to be needed all of the time. Look at how many failures come out of RDWC systems that lack good air pumps, not those hydro shop air pumps. You can see a difference in how a pump like Alita moves water compared to hydro shop pumps. Even those blue air stones are garbage and I use other ones instead. I used to lose crops all of the time before I started using bigger air pumps and Chlorine.

 

[mojave green]

dissipation times/rates of do is a fascinating question. i of course have no answer but am interested fer sure!

 

[budshoteyes]

Try a fish well aireator.....quiet!

 

[The Groff]

Well I found this which disproves the whole 24h holding "theory"

Bummer...

 

[The Groff]

Well I found this which disproves the whole 24h holding "theory"

Bummer...

Woops... ICmag newb here...

[youtubeif]http://www.youtube.com/watch?v=IMqHgWEp2Fw[/youtubeif]

 

[mrrangz]

I replaced all my loud air pumps for inline water pumps ecoplus brand. Running 633 GPH and 1056 water pumps with no significant difference on a 6 site rdwc setups got 3.

I believe as long as water is moving and being in contact with air you should have plenty exchange. There is really no information out there on how much plant roots pull oxygen from the water.

My water temperatures have reached 86 degrees and i have not witnessed any ill behavior in the root zone.

my 2 cents.

 

[willyweed]

did you get the bottle of h2o2? 15% half a mil a litre ?
if not you stand a massive chance of destroying your plants with root rot
it is hard to see with just a visual inspection.look for small pieces of root in the system.
the bigger the plant ,the harder to save them ......
your way may work ,or you may get lucky ! but with water temps that high it is only a matter of time .all the best .ww
what is the point of asking for answers from experienced growers ,to just ignore them

 

[The Groff]

Please explain how you went about things!! how did you position the inline water pumps?

I truly believe flooming is better than airstones, but the root ball becomes so big the pump wont be able to create the necessary bulge at the surface. Also, I bubbles do act on the roots themselves, not only water... kind of prevent waterlogging?

How many runs have you been able pulled since ditching the air pumps? Do you run sterile or bennies?

aaaarg! pleaaase let me know!! I'm desperately trying to cut down noise to the max

 

[Ickis]

Patients on ventilators in an ICU routinely get ABGs drawn. They are arterial blood gases. One of the things they look for is the patients O2 Saturation. They give it as a percentage of how many hemoglobin molecules have an O2 molecule attached to them. This is effected by temperature of the patient and also atmospheric pressure and ph.

I don't know an answer for you. ABGs the O2 molecule and hemoglobin molecule are attached. I don't know if in water the O2 molecule is actually attached to a water molecule or just mixed in with them.

Look up oxygen water dissociation curve or Oxygen-hemoglobin dissociation curve just to see if anything helps.

Just an idea but what about just using tanks of oxygen. There would be no noise except for the bubbling sound. I don't know how much tanks would be to refill.

They do have oxygen generators that hospitals use for patients. They are somewhat quiet.

They also have portable ones that you see advertised for people to walk around with that need continuous oxygen. They are practically silent.

 

[mrrangz]

i waterfall my water to each bucket

 

[TheCleanGame]

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