DIY In-Line Micro-bubbler

[scolley]

For those of you following Tom Barr's recent contributions in this thread, or this one, there are a lot of interesting developments being discussed around injecting very small bubbles into a tank. Circulation of those bubbles is important. If done right, there are claims that this provides great increases in plant growth and health, even beyond the provision of 30ppm of dissolved CO2.

There are multiple methods suggested for accomplishing this. I am particularly interested in ways to accomplish this in-line. If possible, by modifications to a standard in-line CO2 reactor.

This diagram is a simple pic of a typical setup. I left off fine details on the reactor itself, for there are many varieties out there. I suppose the important things to note about the reactor is that water entering the top, CO2 is entering near the top, and water with dissolved CO2 is exiting the bottom to return to the tank.


In this next diagram, I've tried to show how this might be modified to also add micro-bubbles into the tank.


This assumes the creation of another in-line piece, with a ceramic disc or other micro bubbler, injecting bubbles into the flow of water back to the tank. This is connected to a new port on the top of the CO2 reactor, that would provide pressurized CO2 from the excess gas in the top of that chamber.

I realize upon posting this that at least 2 things are missing from this diagram. First, a check valve in the CO2 line between the reactor and "bubble chamber", to keep liquid out of that line. Second, the bubble chamber needs some kind of port to allow maintenance to the bubbler, whether cleaning or replacement.

The two threads I mentioned previously have a lot of discussion around whether these bubbles will be dissolved as they move through the water, instead of circulating around the tank. The current discussion is around whether that process of dissolving is significantly retarded once the water hits around 30ppm CO2. I'm hoping that's the case, or this will not work at all.

Will this work? Is there a better way? I welcome your thoughts and feedback.

Thanks.

[Bayleo]

If the argument holds, this would definitely be a good way to suppliment the typical pressurized setup. The only design issue I can see regards the "port" that you mentioned. Asside from splitting the line before it got back to the tank and putting valves on either side of the bubble chamber apparatus I cannot see an easy way to do this...

I know it's hard to draw in MS Paint, but you may want to angle the reactor so that the extra, undissolved CO2 can find the way out in the easiest manner possible (CO2 outlet as close to the top as possible).

Someone needs to test this to determine how much pressure really builds up in our in-line reactors, just to see if they get a good number of micro bubbles coming from their outlet. This still leaves the question of whether or not the bubbles are CO2, but that can be answered elsewhere.

[jgc]

You are attempt to burp the gas build up in your reactor into a second chamber. Problem I see is there is no presure gradient between the two, nothing is forcing the bubbles to move from the the first chamber to the second, plus any diffuser disk will require pressure to operate.

As a stop gap measure, why don't you just operate the first reactor ups down?

[Bert H]

Steve, what would prevent water, instead of gas, from exiting via the second port? You assume there will always be a gas pocket built up there otherwise, how would the gas exit via that port? I am not sure that assumption will hold water, to use a bad pun.

Seems to me, the ideal situation is to place a diffuser on line with the return tank flow. But even that way, I wonder how quickly the tiny bubbles would dissolve in the water returning to the tank.

[scolley]

Thanks for the feedback. Let me try to make combined answers here...

Pressure - There seems to be some valid concern over pressure, or lack thereof, to drive the bubbler. While it might not be enough, I thought the gas leaving the CO2 bubble counter was pressurized, pressure builds up in the CO2 line to the reactor, and once excess gas builds up in the reactor, that gas should be pressurized too. Which means pressurized gas going to the microbubbler.

I neglected to show the typical check valve in the line between the CO2 tanks and the reactor. On mine, the line between the check-valve and the reactor always fills with water when no CO2 is being released. But when it starts, the CO2 drives the water out of the line. And that implies some level of pressure.

Please someone tell me if this is not true.

Water in the line to the microbubbler - That's the check valve I was mentioning. I think that a check valve would keep water out of some of the line, and gas pressure (when the CO2 was back on) would flush the rest. But it could be that 2nd port (gas outflow) needs to be in the top of the reactor for that to work. Which BTW, achieves the same effect as tilting the reactor I believe.

Upside down reactor - unfortunately that will just get bubbles in the tank, not the 100-500 micron tiny variety Tom Barr has indicated is required. That takes an impeller to chop bigger bubbles up, or a diffuser that makes tiny, tiny bubbles as I'm showing here.

Other alternatives - I could just put a "T" on the line coming out of the CO2 tank, and drive the microbubbler with that. Bu then that would require some valves in both lines to balance the CO2 pressure appropriately between both lines after the "T". I was hoping to avoid that complication.

Thanks for your thoughts. If this can be worked out, it could be cool.

[Bayleo]

You could always split the CO2 line before the reactor, and just have the bubble chamber operating as a second reactor.

**n/m, you posted while I was typing Scolley**

[scolley]

Yeah, so you posted before I wrote the "other alternatives" option.

That could well be the best way to do it. But then it would require a valve on either one (or both) of the "reactors". I'm kinda hesitant to get into pressure balance or co2 flow contention issues between the two devices.

But it would allow me to hook something up without drilling a hole in my reactor.

Anyone have any idea about pressure, or flow, contention between the two devices if I just put a "Y" off my CO2 tank that went to both of them?

[jgc]

not sure if my thought about the "upside down" reactor made it to my post. Mostly just saying that why don't you remove the first chamber and just run all your co2 through the diffuser disk in the second chamber.

A lot will disolve but what remains should still be pretty small bubbles

[scolley]

jgc - Oh, hmmm. That's a thought! Thanks!

So just lose the regular diffuser? And let the "microbubbler" do it all for me.

Tom Barr's contention is that bubbles dissolving gets a lot harder as you approach and exceed 30ppm. If that's true (but still being argued about in another thread) then just using the microbubbler would hopefully spew dissolving bubbles until the tank hits 30ppm, then they should stop being absorbed so easily and start spreading the "oh so desirable" little micro bubbles.

Got to go think about that one. Thanks!

[jhoetzl]

OK, I have been thinking about ways to accomplish this without another powerhead, pump or other inline device...

With that, I thought of something that might work, and, eliminate the external chamber entirely, and not add any more powerheads/pumps.



I wonder how much pressure is exerted on the end cap on my spraybar and how fine a bubble I can get to occur inside the spray bar...

Hmmmm, might give it a shot over the weekend.

[Bayleo]

That's good thinkin' -- just flipping a normal in-line reactor with a diffuser in it upside-down (i.e. water flowing up towards the tank) you might even be able to control the amount of "micro-bubbles" you get by tilting the reactor a bit, or having it vertical, depending on the thickness of the pvc/et cetera you used to build it.

I think it would be critical to have it enter the reactor just before it went up into the tank though, to ensure that some of the bubbles stuck around. Seems like it would work best with something like a lily pipe as opposed to spray-bars, et al.

That still leaves the issue of diffuser maintainence though...

You could build something along this line, with a chamber wide enough for a good-sized diffuser disk, and a removable lid of some sort with valves to shut when you need to remove the lid and clean the diffuser.

[scolley]

jhoetzl - Nice diagrams! And I'm happy for people to use this thread to figure out how to do this without in-line devices. But I've got zero interest in that personally. I want ALL that stuff out of my tank...

Bayleo - what you are showing in your pic is pretty much what I was talking about with the "microbubbler". Just a container with an in, an out, a maintenance port, and a place to take CO2 in that goes into a micro bubble creating device. And not just any airstone will do apparently. The bubble size appears to be 100-500 nanometers, which is much smaller than most airstones can accommodate.

But, I ordered a few of these a couple of days ago - and should arrive in a couple of days.

And I'm assembling something to accommodate it now. So I bought one of these...

The right angle opening is screw threaded and will be the maintenace port. And slip fittings will go in the big holes at either end to hook up to the water hoses. The big problem is the port for the CO2.


But any airline connector I could find was not long enough, so I had to drill an inset in the exterior like so...




So with a connector it looks like this...




And for an inside view, you can see that there was almost not enough connector showing to get a good airline connection within the PVC. So I got the Dremmel out (gotta love those Dremmels ) and sanded out a little depression on the inside. So there is hopefully just enough connector poking through to get a good connection.




What I had not thought about, until this thread, was that this might just be all I need - replacing my in-line diffuser.

Can't wait to see how this turns out!

[Momotaro]

What is to stop the CO2 bubbles from immediately rising to the water's surface once they exit the spraybar?

Seems to me you'd need a pretty strong current to prevent the gas bubbles from rising up as they exit the output.

Mike

[scolley]

Originally Posted by Momotaro

What is to stop the CO2 bubbles from immediately rising to the water's surface once they exit the spraybar?

Seems to me you'd need a pretty strong current to prevent the gas bubbles from rising up as they exit the output.

Mike

Good question. I'm given to understand that when bubbles are small enough, the upward force they get is exceeded by their tendency to flow with the current.

But that's just what I've surmised from reading the other threads. I, for d*mn sure don't know, and would love to be told what will happen.

I can say this, with all the other discussion in the other of Tom B's threads about Amano's configurations, and where he puts diffusers and whatnot, it is clear that people think the micro bubbles are going to be blown around the tank and not just rapidly rising to the surface. So, I'm assuming the same.

But frankly, I don't know. That's why I started this thread... to get such questions discussed. Thanks for asking!

[jgc]

once you have it connected and burped - post pics

The hope is that the bubbles that reach the tank will be small enough to have minimal bouancy and will rise pretty slowly.

Just my thoughts - place the T on it's side. Input on the side, diffuser on the bottom, exhaust out the top. Or not. If you use threaded fittings you can always change it - and not as if cost all that much to change even if it is all glued up.