Co2 Reactor venturi issue, excessive gas buildup

How much CO2 are you injecting into the powerhead to start? It seems like you are just injecting too much CO2. Once you get beyond a certain point and it builds up there's little point in adding more.

 

I'm not sure its really a saturation point as much as the gas injection rate exceeds the dissolution rate of CO2 within the reactor. You can improve dissolution rates a number of ways: increased flow (optimal counter current type flow), decreased bubble sizes, mechanical ways of breaking up the gas or preventing it from collecting all together. When the gas collects there is less surface area contacting the water so reduced dissolution of the gas. Basically everything is going for maximum mixing and minimum bubble size.


I like the cerges reactor styles, because I think you have more options to do these things within them. For example, Aquariumplants.com sells a cerges style reactor they put a pump into. The pump circulates water from the bottom into the top of the reactor. The added flow greatly enhances the efficiency of the reactor. Other commercial style reactors use spinning parts at the top to constantly chop up the collecting bubbles, most of these are versions of the Cerges design. In the types you are using people often add bio balls or other types of media to break up the bubbles and allow small bubbles to collect within the media. Something like that may help improve efficiency.


I've been thinking about the idea of adding a small plastic fan blade around a small cylinder that runs the length of the reactor. It would spin with the flow and break up bubbles. Not sure if it could be DIY'd since finding parts might be tough and putting it together more difficult.


I'm not sure if you could make the pump thing work in a reactor like this, but it would be interesting to see, since no one has done it that I'm aware of. You need a cable gland connector of the appropriate size for the pump cord. Cut the cord, drill a hole in the bottom side of the reactor the appropriate size for the cable gland connector, fix the pump inside (small rio) so that it flows counter to the inflow creating more stirring and agitation, run the cut cord through the gland and seal, reconnect the plug to the cord, and then seal up the reactor. This is all in theory and easier said than done...but it'd be cool to see a counter current pump inside a vertical style reactor like this. Basically same thing aquariumplants.com does...but in a different style reactor.


You can get too much flow through and carry out the bubbles before they are dissolved, but looking at the pump you are running, I'd say its underpowered for the size of your reactor. I use a very similar model on my large UV filter when I use it because the flow is slow and I get good dwell time. I wouldn't want that slow of a flow in a reactor. To start you could probably use a stronger pump, if you start to get a lot of bubbles moving out of the reactor through the outflow, a bit of media like coarse filter sponge in the bottom to collect the small bubbles would alleviate that.


Reactors are sweet...don't give up on them yet.

 

Nice work! Looks very good.