Effect of Aerating Calcium Reactor Effluent on pH and dkh?

[JDtimk]

Has anyone tried aerating the effluent of a calcium reactor with an air-stone prior to returning it to the tank to see if it:

1. raises the pH a bit so it doesn't lower the tank pH so much
2. has no effect on the dkh of the effluent

I run a calcium reactor with a secondary reactor chamber in an effort to fully utilize the co2 in the effluent and raise the pH as much as possible before returning it to the tank. I also run Kalkwasser.
I am not stuck on the pH number per say, but am borderline low end of the pH in my tank range and want to see if I can scrub a bit more co2 before I return the effluent to the tank in hopes that the effluent won't depress the pH in the tank as much.

Basically I would take the effluent output at the needle valve that normally goes into the tank and run it into a small container with an air stone. The output of the air stone container would fill up with effluent and overflow unrestricted out an overflow tube. The output of the air stone container would be dependent on the output of the calcium reactor needle valve that would normally go straight into the tank.

Any thoughts on this whether you have tried it yourself or not?

 

[declanisadog]

I’ve never heard of anyone doing that, but it sounds like a good experiment. Tagging along for results.

 

[kwan8911]

It might be easier and better to just drip the effluent close to the intake of a protein skimmer ?

 

[sghera64]

Been there, done that. . .. won’t do it again.

As soon as air bubbles through the effluent, the pH increases and causes a precipitate (CaCO3).

I had my effluent go into a pipe with bubbles running counter current. The pipe walls and the drain tubing got coated as did the air stone.

I now drip my CO2 reactor’s effluent into that part of my refugium that has the chaeto. The algae scrub the excess CO2 and the effluent is immediately diluted with tank water before any precipitation.

 

[tgrick]

I do that now. I do not run an air stone, but just tubing. I took 2" PVC pipe, put a cap on the bottom and a 3 way fitting on the top. I put the airline in the top and drip the effluent there. The effluent from the pipe drips into the refugium. My Ph hovers around 7.9. It drops to 7.8 at times and gets as high as 8.1. I also use Kalk as well. The tank is a red sea 625xxl...135 gallons and about 160 gallons total volume.

 

[lapin]

I drip as well into my sump before the socks. The vortex of the water moving thru the socks causes some air to mix in. Never measured the effect.

 

[Wrasse-cal]

Been there, done that. . .. won’t do it again.

As soon as air bubbles through the effluent, the pH increases and causes a precipitate (CaCO3).

I had my effluent go into a pipe with bubbles running counter current. The pipe walls and the drain tubing got coated as did the air stone.

I thought about doing this, and then decided not to precisely because I feared this would happen! Thanks for confirming my instinct.

 

[JDtimk]

I have some results from 12 hours of aerating the effluent with an airstone.
Before aerating the effluent:

1. the pH of the water in the reactor was 6.52
2. the pH of the effluent coming out of the second chamber was 6.98
3. the pH of the tank at 6am was 7.80

After aerating the tank water as described in my first post:

1. the pH of the water in the reactor was 6.52
2. the pH of the effluent coming out of the second chamber was 6.98
3. the pH of the effluent after aeration in a third holding container by air stone with room air
   1. I aerated the effluent and let the pH stabilize overnight
   2. the pH of the effluent after 12 hours of aeration was 7.67
4. the pH of the tank at 6am following 12 hours of aeration of the effluent as it returned to the tank 7.92

Obviously just quasi experimental design here with variables uncontrolled and unaccounted for, but in general it looks like aerating the effluent before returning it to the tank can raise the pH of the effluent by approximately 0.5 to 0.7 units of pH.
The effect on the tank pH may be a rise of similar pH.

I did not measure the dkh of the effluent but I have no reason to suspect it changes. My tank dkh didn't change over the course of the aeration of the effluent. It followed the usual rise and fall of evening to morning alkalinity consumption as before the aeration of the effluent.

I haven't run this long enough to notice any precipitation of calcium carbonate yet, if that is a given I will find out soon.

 

[sghera64]

I have some results from 12 hours of aerating the effluent with an airstone.
Before aerating the effluent:

1. the pH of the water in the reactor was 6.52
2. the pH of the effluent coming out of the second chamber was 6.98
3. the pH of the tank at 6am was 7.80

After aerating the tank water as described in my first post:

1. the pH of the water in the reactor was 6.52
2. the pH of the effluent coming out of the second chamber was 6.98
3. the pH of the effluent after aeration in a third holding container by air stone with room air
   1. I aerated the effluent and let the pH stabilize overnight
   2. the pH of the effluent after 12 hours of aeration was 7.67
4. the pH of the tank at 6am following 12 hours of aeration of the effluent as it returned to the tank 7.92

Obviously just quasi experimental design here with variables uncontrolled and unaccounted for, but in general it looks like aerating the effluent before returning it to the tank can raise the pH of the effluent by approximately 0.5 to 0.7 units of pH.
The effect on the tank pH may be a rise of similar pH.

I did not measure the dkh of the effluent but I have no reason to suspect it changes. My tank dkh didn't change over the course of the aeration of the effluent. It followed the usual rise and fall of evening to morning alkalinity consumption as before the aeration of the effluent.

I haven't run this long enough to notice any precipitation of calcium carbonate yet, if that is a given I will find out soon.

Give it a month and I would expect there to be deposits forming on surfaces in contact with the aerated water up stream from where it joins the bulk of the system water.

If you want a more dramatic pH rise from aeration, bubble air through the water that has been pulled from outside the home. Or take a cup of effluent outside and aerate it for 15 minutes to see the effect.

When we use inside air to off-gas CO2 into the inside air, . . . Well you see where this is going. It become a diminishing return process.

I did not see much advantage for fish and corals when I was doing this. I was able to increase tank pH with my CO2 reactor on-line by about 0.2-0.3 pH simply by drawing in outside air into my skimmer and through a Luft air pump - into my fuge. Again, not much difference. Some folks say that the algae in coral actually use and appreciate CO2 - so leaving it in, along with the Ca and Alk in the effluent, may all be good stuff.

As a aside, I also add kalk. But I now only add it at night in 1 hr intervals. This keeps my pH pretty constant over a 24 Hr period at around 8.18 - 8.20.