Using an Airstone vs Water Surface Tension for O2

the mass transfer of gasses (eg O2) is calculated by the formula Na=Kla(C*-CL) this is the rate at witch a gas passes between phases at the gas/liquid interface
in modern bioreactors there are 2 methods for adding O2 to the mix, 1. sparging (bubbler) and 2. mixing

the reason bubbles are put in the water instead of allowing the water to sit is because it increases the area of the gas/liquid interface; the smallre the bubbles the more area (denoted by "a" in the above formula) where mass transfer can occur, by putting a pump in the water as mentioned above would simulate wave bioreactor designs where rocking is enough to mix the media and provide sufficent gas transfer. rocking may be a little impractical for plants but placing the pump in the resivoir would work as well provided that there is high enough concentration of O2 in the headspace above (CL denotes this factor in the formula and CL denotes total gas in the headspace) to keep up with the O2 requirements of any m/orgs an the plants
Kl is a variable depending on how soluble the gas is in the liquid (O2 in water) aka the mass transfer coefficent

when the solution is mixed the more saturated liquid is moved to the bottom and the unsaturated to the top, its grand in a small setup but nothing huge

in short a pump would be fine for smaller setups but in larger setups the agitation would be insufficent and bubbles would be required

Briester Behemoth said:

K just making sure cuz logically to me you guys are right, more bubbles = more O2...but not according to that article. I've got a spare underwater pump laying around but not an extra air pump or air stone. plus I hear air stones get junky pretty quickly.

Click to expand...

Only if you buy the cheap walmart ones and shit.
My micrpore do not get clogged.
Used the same stone for 4 grows in a row and NO cleaning.

from what I understand. The smaller the bubbles you have, the better. I think its called lime wood. Wood air stones produce the smallest bubbles.

Weedasaurus said:

from what I understand. The smaller the bubbles you have, the better. I think its called lime wood. Wood air stones produce the smallest bubbles.

Click to expand...

exactly, smaller bubbles also have the added bonus on being less violent for the roots than big bubbles

I would say air stone over pump if your going to leave it in your res for long periods of time. I've heard its not good to leave electro magnetic pumps in your res. for long periods of time because of the fact that the electro magnetics of the pump messes with the micro biology in your res. Not 100% sure on it but an avid horticulturist was telling me about it.