I installed this idea a couple months ago in my Geo reactor to 1) Reduce the C02 gas leaving the rxr, and 2) maximize C02 usage efficiency. It has worked well, cutting my gas usage by 1/2, and helping to prevent "vapor lock" from clogging the effluent line. In my case, I drip 200ml/min eff, but the bubbles are only at 30bpm, and rxr pH is still 6.6 (A.R.M.)! If you want a relatively simply DIY, and you have a "top down" recirculating reactor (like the Geo), then this is for you!
In a nutshell, a second, small recirculation loop is created that allows the gas accumulating at the top of the chamber (normally escapes out the effluent line) to get pulled back into the C02 inlet (in front of the circ pump) and get chopped up again by the pump.
Even though the entire reactor is pressurized from the feed line, the pressure at the top of the chamber is still greater than on the intake side of the pump (chamber bottom).
This first pic shows the mods to the rest of the reactor.
Another tap is added on the other side of the pump inlet; the 1/8" id tubing fitting that goes here should only be screwed in (or cut) so it is flush with the cover. Both the pump return and the effluent line must protrude below the cover about 3/16-1/4" to make sure the gas goes up the second circ loop. For the existing effluent fitting, I just threaded it ALL the way in. For the pump return, I actually glued a 1/4" piece of PVC pipe over the outlet in order to keep the flow from throughing bubbles around.
This pic show's what has to be added to the lid of the rxr.
(1) is a pinch valve, as I wanted to play with the flow in this second loop. It can be left wide open. (2) is the airline tubing that takes the water down to (3) a "Tee" (located below the check valve) which allows the air/water to re-enter the gas line, getting chopped up and forced back into the loop.
Another benefit is that all of the gas coming through the bubble counter is "premixed" with the water in the secondary circulation loop, such that it goes into the pump as small bubbles, then gets chopped even finer. This makes for a constant small gas stream, instead of little "bursts" of C02 getting chopped up.
I hope someone gives this a try, it was 110% worth the time and effort. Lemme know what you think!