Aerating CaRX effluent to remove excess CO2

[Dennis Cartier]

I have a DIY CaRX project on the go and ran across a commercial CaRX that has an aeration chamber for the effluent to pass through. Randy, I just saw your post in Reef Myths thread about aerating tank water outside raising PH in cases where there is excessive CO2. So I am wondering if aerating CaRX effluent using house air would have the same effect? My fish room measures 400 - 500 ppm CO2 day to day on my CO2 meter. I could direct the vented air that was used for the aeration to outside the house so as to not raise the CO2 level in my fish room. Do you think it is worthwhile to explore this avenue?

Dennis

 

[NeverlosT]

Maybe drip your effluent into the skimmer if your skimmer is drawing external air for the one-two punch?

I use a CO2 scrubber on skimmer, secondary chamber on CARX, dose kalkwasser, and all that, but frankly my pH is still low. I need to get external air source to the skimmer. If only the tank/filtration wasn't part of an island in my kitchen...

 

[Dennis Cartier]

Maybe drip your effluent into the skimmer if your skimmer is drawing external air for the one-two punch?

I use a CO2 scrubber on skimmer, secondary chamber on CARX, dose kalkwasser, and all that, but frankly my pH is still low. I need to get external air source to the skimmer. If only the tank/filtration wasn't part of an island in my kitchen...

The tank I am planning this for, my frag tank using 2 part, has outside air for the skimmer and a huge 20g fuge that keeps the PH of the tank at 8.20 - 8.25 24x7. When I switched from house air to outside air, it bumped the PH by about 0.1 units. For the frag tank, I could drip the effluent into the fuge and get a boost in growth from the excess CO2, but for my 500g build, I am not planning on having a fuge, so having a method of stripping the CO2 would be best.

Dennis

 

[X-37B]

If your carx is dialed in correctly there should be very little co2 in your effluent. I drip my effluent into a small cylinder of coral bones. Ph stays the same if I do not drip into it.
I run solenoid on and adjust effluent flow and co2 drip rate to get 20+ dkh. This is the simplest way to setup a carx imo and others. Search jda for proper carx setup and follow his advice. Its really that simple. I set mine up a month and a half ago and dkh has been stable at 8.1-8.3 for over a month.

 

[Dennis Cartier]

I have read some of JDA's posts on setting up a CaRX properly. The reactor I am building will be operating a little different than the type that JDA's suggestions are for. The reactor will be operating in saturation mode with the CO2 controlled by a float switch and an excess of CO2 available to be dissolved as new water enters the reactor. My best guess is that the PH of the effluent will be around 6.0 (or lower) when it leaves the reactor and the DKH should be about 70. The flipside of the high DKH effluent is that I will be flowing much less than a typical reactor, so that is why I am investigating the possibility of stripping CO2 as it slowly passes an aeration chamber.

I have a spare Geo 618 on hand and was thinking of making a powered secondary to recirculate the effluent and then flow it into a normal secondary. That will be a last resort though as I would rather use the aeration chamber first as I can build extra of those for more tanks, but only have 1 extra 618.

Dennis

 

[Randy Holmes-Farley]

Aerating the effluent helps, although there is at least a theoretical risk of reprecipitsting the calcium carbonate if the pH rises too much.

 

[Dennis Cartier]

Aerating the effluent helps, although there is at least a theoretical risk of reprecipitsting the calcium carbonate if the pH rises too much.

Interesting, because the commercial CARX that has the aeration chamber has a settlement chamber after it where it is suggested that sediment will collect from the effluent. They state that PO4 will be stripped as it traverses the settlement chamber and that periodic removal of the sediment will be required. I thought it sounded plausible in theory, but was not sure how effective it would be (lowering PO4) in practice.

Dennis

 

[Dennis Cartier]

Aerating the effluent helps, although there is at least a theoretical risk of reprecipitsting the calcium carbonate if the pH rises too much.

Would this would be true of any secondary chamber as well? I am wondering if there could be diminishing returns of having high dkh and low PH effluent (say 70 dkh / 6.0 PH ) flow through a secondary chamber and ending up with a higher PH and lower dkh effluent as a result?

Dennis

 

[X-37B]

Would this would be true of any secondary chamber as well? I am wondering if there could be diminishing returns of having high dkh and low PH effluent (say 70 dkh / 6.0 PH ) flow through a secondary chamber and ending up with a higher PH and lower dkh effluent as a result?

Dennis

70 dkh? Is that even possible, or needed?
If your ph is 6 going through the second chamber wont your effluent dkh increase as the media dissolves in chamber 2, thus useing up excess co2?

 

[X-37B]

Interesting, because the commercial CARX that has the aeration chamber has a settlement chamber after it where it is suggested that sediment will collect from the effluent. They state that PO4 will be stripped as it traverses the settlement chamber and that periodic removal of the sediment will be required. I thought it sounded plausible in theory, but was not sure how effective it would be (lowering PO4) in practice.

Dennis

I have a small chamber, see old pic, that my effuent drips into.
I cleaned it out a while ago.
Under the bottom plate their was about a tablespoon of your settlement.
Same in my carx when I cleaned it after 10 months running
I did not really need to clean the carx as I run manmade media and it does not get mushy as most coral bones do, i.e. my friends reactors.
I dont understand the lowering po4 but maybe someone will chime it.

 

[Dennis Cartier]

70 dkh? Is that even possible, or needed?
If your ph is 6 going through the second chamber wont your effluent dkh increase as the media dissolves in chamber 2, thus useing up excess co2?

The 70 dkh is based on reports from other users who are using this type of reactor. Mine is still dry as I work on other things. These are saturation point, up flow reactors. The expectation is that by using much higher strength effluent, and lower flow through the reactor, the PH drop is minimal.

The reactor models with users reporting 70 dkh, are the Aquarium Engineering ACR automated calcium reactors (which I also have). I am just working through the idea of providing even more protection against a PH drop by further stripping the effluent using air.

The vendor using the aeration chamber and settlement is Aquacare.de. I read through their manuals and find there ideas quite interesting. I am just not sure if the end result will be worth the added complexity. They quote an operating PH effluent value of 5.0 - 5.2, which is super low, but they also recommend calcite media in their reactors. Oh, and after the aeration chamber, their effluent is 7.3 or so. That sounds pretty effective.

Dennis

 

[X-37B]

The 70 dkh is based on reports from other users who are using this type of reactor. Mine is still dry as I work on other things. These are saturation point, up flow reactors. The expectation is that by using much higher strength effluent, and lower flow through the reactor, the PH drop is minimal.

The reactor models with users reporting 70 dkh, are the Aquarium Engineering ACR automated calcium reactors (which I also have). I am just working through the idea of providing even more protection against a PH drop by further stripping the effluent using air.

The vendor using the aeration chamber and settlement is Aquacare.de. I read through their manuals and find there ideas quite interesting. I am just not sure if the end result will be worth the added complexity. They quote an operating PH effluent value of 5.0 - 5.2, which is super low, but they also recommend calcite media in their reactors.

Dennis

Thanks! I will read up on that method.
Having not read it yet they must be using manmade media, right?
I have found the effluent/bubble method to be quite simple and it has no effect on my tanks ph.

 

[X-37B]

They use manmade media as I thought.
Interesting idea but way over complicated for a very simple process, imo.
It will be interesring to get some seasoned carx users response to this method.
Always interesting to see new ideas. Thanks as I never new this existed.

 

[Dennis Cartier]

I set out to test this today. I am planning on ordering the need flanges and parts to make some hardware out of sch 80 PVC, but wanted to confirm that it would be worthwhile before I spent money on the real thing.

My effluent was testing between PH 6.1 and 6.4 as it entered the tank. I constructed a test unit out of 1.5" ABS pipe, about 18" tall. I placed an air stone in the bottom along with a feed from the CaRx. After running it for half an hour, I retested the effluent PH, and it tested at 7.76. I also noticed the effluent dripping from the test unit had turned milky and almost looked thick. So as Randy predicted, aerate it too much and it starts to re-precipitate. I will need to turn the air down to try to get the effluent to 7.3, which the Aquacare list as being the upper limit to target.

Now I just need to see if I can detect a rise in the PH of the water column after inserting the aerator.

Dennis

 

[Dennis Cartier]

As a follow up to this, I ended the test as the effluent precipitated all the calcium carbonate out of it and the alk of the water column started to drop. I did not try to lower the air, but expect that a controlled lower air flow would find a happy medium.

Dennis