MCU Research CO2 Scrubber

[Kengar]

This unit is used to remove CO2 from the air going into your skimmer. Because CO2 makes up such a small percentage of the gas in air, I was skeptical but decided to try it out. Boy, was I impressed! I installed the unit last night. Tank is a 156, probably 170 g total system volume, and skimmer is a Bubble King mini 180. Draw is purported to be 2000 lph. Yesterday’s pH max was 8.11 with 7.84 min the night before. Today topped out at 8.35, and you can see the whole graph (from AquaController III) trending upward:

http://i224.photobucket.com/albums/dd264/Kengar/graph2.jpg

[Boomer]

Ken

We have had two full threads on this unit here in the last week :) And nice graph.

[rbnice1]

this is the 3rd thread in the last 30 minutes in different forums.

Must really need to sell these I guess.

[Boomer]

The big debate issue is how long it will last before a refill.

[kaskiles]

Kengar, does your display tank and sump(s) receive a lot of air flow? Or are they covered, canopy over the display tank and sump(s) enclosed in cabinet?

[Randy Holmes-Farley]

It is an interesting graph. It looks to me as if you will have to back off on the effect soon or the pH may raise too far. :)

[Kengar]

I put the three posts in the three different forums I thought the information would be relevant to. Not trying to sell units for them; just impressed with the performance. I didn't go checking first to see if there were other threads, I just wanted to share information that I thought would be useful.

As for my setup, my tank is completely open-topped, and lighting fixture is suspended over it. I use fans blowing across the top of the water surface to control temperature by evaporative cooling. Sump is in the stand, which is open-backed, and I have a fan running full time in the cabinet to circulate air in there.

I should also add that I run two Ca reactors in tandem, with output from one being input to next, but with CO2 only into first. Essentially a dual-chamber configuration, but with recirculation in the downstream chamber, too. Four seconds between CO2 bubbles. Haven't checked effluent parameters yet (pH, Ca, and alk) yet, though.

As for seeing the graph continue to shift, although I think Randy's post was tongue-in-cheek, I don't think thiat is a concern. Rather, I believe the system will simply move to a new equilibrium level, with pH rising and falling around that new level.

[kaskiles]

I would have expected the gas exchange with the un-stripped air (high CO2) at the water surface of the DT and sump would have exceeded that of the skimmer, and the pH increase to be much less pronounced. But your results seem to indicate otherwise... I was also worried that it might decrease the air draw of the skimmer, and possibly affect it's performance.

Please keep us updated on the consistency of these pH results, lifespan of the media and skimmer performance changes.

Thanks!

[Kengar]

I was concerned re decreased draw into skimmer, too. Per conversation wtih Premium Aquatics, though, MCU redesigned their original system to avoid/minimize additional drag. I haven't seen any noticeable performance change in the skimmer in terms of bubbles/foam, but that would really be hard to quantify, and I haven't really had enough time to see whether skimmate output falls. However, I believe one of the primary reason skimmers aren't used in freshwater systems is that the bubbles collapse under low pH conditions, so conversely raising pH may improve bubble stabiliyt in saltwater and hence improve performance, at least by enough to offset any decrease caused by reduced air intake. Final observation: I see my BTA's actually bubbling out again this a.m., which they haven't done in a while.

[Randy Holmes-Farley]

As for seeing the graph continue to shift, although I think Randy's post was tongue-in-cheek, I don't think thiat is a concern. Rather, I believe the system will simply move to a new equilibrium level, with pH rising and falling around that new level.

It likely would reach a new range, but the graph doesn't indicate that yet. There is certainly no theoretical reason such a device couldn't drive pH too high, just like dosing limewater.

[Boomer]

freshwater systems is that the bubbles collapse under low pH conditions

It has to due with surface tension and water hardness. The harder the water the more skimming there will be and this also includes the nature of the organics in FW vs hard water. Think of when you are in a bath or shower, where one house/ motel etc, has hard water and the other soft water and the difference you see when you lather yourself up with soap.

This goes into greater detail

What is Skimming?
http://reefkeeping.com/issues/2006-08/rhf/index.php

In regards to your pH. As Randy has stated yes it can get to high. You will see this in heavy planted aquariums, be it FW or SW, where the pH can it over 9 pH. And all from what, the Algae or plants pulling out the CO2 just like the scrubber or limewater. @ 25 C, 35 ppt, 2.5 meq / l Alk, a pH of ~ 10.5 must be reached to have zero CO2

[Kengar]

I thought that surface tension varied with pH. Probably varies with a whole host of factors! I will take the caution re pH going too high to heart and watch it. I'll give the syystem a few days to stabilize at full capability of the scrubber and post further graph to show where it stands.

[Boomer]

Yes, a whole host of factors. Just stick your hand in the tank near the skimmer input and watch the skimming go about flat or put a drop of aloe-vera in it and watch it go nuts.

Also see my edit.

[Kengar]

and the difference you see when you lather yourself up with soap.

I'm supposed to use soap? :D

[Boomer]

I add Tide once a day :)

[Kengar]

Whoops! I deleted the original graph showing the rise in pH from my photobucket account. Here it is again:

http://i224.photobucket.com/albums/dd264/Kengar/risingpH.jpg

a few days later, the increased pH is holding steady (lights left on a little longer tonight, which is why the peak is sustained)

http://i224.photobucket.com/albums/dd264/Kengar/pH.jpg

[Boomer]

Good to hear Kengar :thumbsup:

[Randy Holmes-Farley]

Looks good! :)

[Kengar]

hmmmmm, two weeks later and pH has dropped about 0.2 overall. Not sure whether the GFO dust had something to do with it when I fired up a fresh batch for phosphate filtration, since the drop seemed to coincide with that. Putting in a fresh cartridge tonight; will see how long that lasts.

[Boomer]

Well, Jeremy from PA told me at MACNA his media in his test lasted like 2 weeks. It may have been the dust. Check the Alk and Ca++ and see if it has dropped.

[mcallahan]

I wanted to add to the thread as it seems the useful life of the cartridges is around 2 weeks.

I've been running the scrubber for 2 weeks and I saw a nice rise in pH - from 7.85 to 8.1 for night values, from 8.05 to 8.25 for the day values.

However, the past 2 nights, my pH has dropped all the way to 7.85 again so I'm guessing the cartridge needs to be replaced. I replaced it this am so I'll watch and see how my pH recovers.

Here is my graph:

http://mrsaltwatertank.com/tank/pH/pH-drop.jpg

[Randy Holmes-Farley]

Thanks for the info. :)

How much did the cartridge cost you?

[mcallahan]

Here is what the "spent" cartridge looked like colorwise. Below is the backside of the cartridge which I wanted to show as you can see that the cartridge is not clearly spent - there are portions of the cartridge that haven't changed colors yet.

That being said, I'm wondering if some channeling is happening in the cartridge and shaking the cartridge to re-arrange the media inside would prolong the life of the cartridge.

Spent Scrubber on left, fresh scrubber on right.
http://mrsaltwatertank.com/tank/pH/spent_scrubber.jpg

Perhaps some channeling here? The top of the scrubber is clearly more purple than the bottom
http://mrsaltwatertank.com/tank/pH/spent_scrubber_2.jpg

[mcallahan]

Thanks for the info. :)

How much did the cartridge cost you?

$25 @ Premium Aquatics.

Once we can nail down the media used, I'm going to get a refillable DI cartridge from Bulk Reef Supply and see if I can get the same results.

BTW..I'm already using a $10 canister housing from BRS...works fine so save your $$ and buy the cartridge alone and pickup the housing from BRS.

[Yogre]

Please keep us updated! If we can get the price of the media down a bit I'd look at installing one of these in my system.

I can't figure out a way to get fresh air to my skimmer and opening a window in Wisconsin in January isn't really practical.

[Boomer]

mcallahan

That does look like channeling to me. I would shake and the tumble i.e., roll the cartridge to rearrange the media and see if you can get more color change.

You can get all that stuff here now, cheaper and higher grade media :)
http://www.thefilterguys.biz/

[Yogre]

Thanks Boomer, that's what I was looking for!

Just gotta sneak this purchase past the CINC-House and I'll be set... Been spending a bit too much on the hobby recently lol.

[mcallahan]

Please keep us updated! If we can get the price of the media down a bit I'd look at installing one of these in my system.

I can't figure out a way to get fresh air to my skimmer and opening a window in Wisconsin in January isn't really practical.

I'll keep everyone updated. I see running a scrubber as necessary to keep my pH up, but @ $50/month, that's too steep for me.

Here is a graph of my pH recovering after replacing the cartridge. I replaced the cartridge at the bottom of the valley in the graph.

http://mrsaltwatertank.com/tank/pH/d10.jpg

[mcallahan]

mcallahan

That does look like channeling to me. I would shake and the tumble i.e., roll the cartridge to rearrange the media and see if you can get more color change.

You can get all that stuff here now, cheaper and higher grade media :)
http://www.thefilterguys.biz/

Thanks for the headsup!

Hmmm...looks like the filter guys got smart and starting offering bulk media.

I'll check it out. I like their stuff, but their shipping prices stink. They wanted to charge me $16 to ship me a 3 RO/DI filters.

Looks like the same thing here...$15 to ship me a gallon container. Esch.

[mcallahan]

Please keep us updated! If we can get the price of the media down a bit I'd look at installing one of these in my system.

I can't figure out a way to get fresh air to my skimmer and opening a window in Wisconsin in January isn't really practical.


Boomer pointed out that http://www.thefilterguys.biz/ has the media for the scrubber.

[Boomer]

How does his shipping stink, that is what shipping cost ? Have you checked on it ? Look at the savings you are getting vs MCU :) TFG 1 gal container vs MCU nonrefillable cartridges is more than a $100 saving :D

[bertoni]

I can't find a link on their home page. Sniffle.

[Boomer]

Jon

TFG
http://www.thefilterguys.biz/skimmer_media.htm

"skmimmer media"

[bertoni]

Thanks! The pages says the media turns from white to violet and back to white. What do they mean? Can it be regenerated?

[gasman059]

I'll be doing some testing of this unit shortly and will be adding the results here for sure.

The media is no different than soda lime used in our anesthesia machines to prevent re-breathing so in my case it should be a breeze to obtain!.

But then again at bulkreefsupply prcing it should be pretty affordable.

[Boomer]

No Jon you can not regen it as you are making CaCO3. "back to white" That is what happens to the color indicator once it has exhausted and turns violet. If it is left to sit, the color indicator reacts with its internal components/compounds and turns back to white,

Ca(OH)2 + CO2 ==Water/NaOH(catalyst)=> CaCO3 + H20. The "Kalk" so to speak has about ~18 % moisture.

Some do not use NaOH to include KOH, also an additive for many but are just Ca(OH)2. You end up with about 80 Calcium carbonate when these kinds of media are exhausted. There are, as you can see, different formulations of soda lime. There is a growing concern among Anesthesiologists to shift to Ca(OH)2 only, as anesthetic vapor degrades often into a number of toxic compounds, especially Compound A, a vinyl ether, when using other formulations. But for us it is a non-issue.

[bertoni]

Thanks, Boomer!

[Boomer]

You bet Jon :)

[gasman059]

No Jon you can not regen it as you are making CaCO3. "back to white" That is what happens to the color indicator once it has exhausted and turns violet. If it is left to sit, the color indicator reacts with its internal components/compounds and turns back to white,

Ca(OH)2 + CO2 ==Water/NaOH(catalyst)=> CaCO3 + H20. The "Kalk" so to speak has about ~18 % moisture.

Some do not use NaOH to include KOH, also an additive for many but are just Ca(OH)2. You end up with about 80 Calcium carbonate when these kinds of media are exhausted. There are, as you can see, different formulations of soda lime. There is a growing concern among Anesthesiologists to shift to Ca(OH)2 only, as anesthetic vapor degrades often into a number of toxic compounds, especially Compound A, a vinyl ether, when using other formulations. But for us it is a non-issue.


The main components of soda lime are

Calcium hydroxide, Ca(OH)2 (about 75%),
Water, H2O (about 20%),
Sodium hydroxide, NaOH (about 3%), and
Potassium hydroxide, KOH (about 1%).

The reaction is basically:
CO2 + H2O --> H2CO3
H2CO3 + 2 NaOH (or KOH) --> Na2CO3 (or K2CO3) + 2 H2O + Energy
Na2CO3 (or K2CO3) + Ca(OH)2 --> CaCO3 + 2 NaOH (or KOH)


There's basically two main: soda lime and baralime, the difference is barium vs calcium, mainstrem is soda lime.

The compound A theory for volatile anesthetics ie. specifically sevoflurane and the formation of compound A in low flow states has only need studied in rats and there's no clinical application. So in theory it exists but in clinical practice is of no concern although we all when using sevoflurane tend to run our machines in higher flows to cover that possibility.

The particle size and channeling provides variables for "channeling" and IMO this ceratinly can be extrapolated to what we are trying to do here.

As soon as I get this unit going in my tank I will be using our mixture of soda lime from our canisters to establish lenght and efficacy.

[Boomer]

Thanks Gas for the more detailed reaction and the future testing. However, not all Soda limes contain NaOH or KOH as I stated but are using, Calcium Hydroxide, Calcium Chloride and Calcium Sulphate with about ~ 15 % water.

low flow states has only need studied in rats and there's no clinical application

I do not think I could agree on rats only, at least as far as CO exposure goes, in low flow :)

ANESTHESIOLOGY NEWS - July 2009:

Low-Flow Anesthesia Routinely Yields High CO Levels

Dr. Richard Levy and his colleagues studied children who underwent general anesthesia at CNMA in Washington, DC. CO exposure was confirmed during low-flow anesthesia as it was regularly produced, even with fresh soda lime. This work is consistent with other studies that have also linked the presence of NaOH and/or KOH to the production of CO, but more often focused on this patient safety issue with desiccated soda lime.

The "take-home message" outlines the risk of using strong alkali absorbents during low-flow anesthesia. Their recommendation is to choose either higher fresh gas flow rates or simply use the CO2 absorbent that lacks the strong alkali metal hydroxides.

[gasman059]

Boomer thx I bet ya the articles are quite conflicting- and furthermore w/o even reviewing the article and reference, childrens anesthesia has tons of variables the must important of all is the different circuits utilized and the possiblity of re-breathing that each circiut brings to the table.
There's Mapleson A-B-D( types of circuits) etc and all to some extent can casue re- breathing if not utilized at a certain flow rates.

Who would have thought i would be getting anesthesia CME'S in reefcentral LOL.


While there's always a possibility of re-breathing with low flow states( meaning utilizing a flowmeter with a fresh gas flow of oxygen below 1 in must cases) our anesthesia machines do provide us alarms to avoid this problem.

The reference to rats as it related to this forum was specific to sevoflurane and seviflurane only and it causes renal faliure when they are exposed to low flow states for prolongued periods of anesthesia/sevoflurane.

Sevoflurane anesthesia is used every x millions around our O.R> w/o problems. Is safe with a great partition coeficient and a proven track record.


Our vapors are quite safe this days and our anesthesia machines even safer---some have changed since I went to medical school/anesthesia residency and so forth but for the must part our avoidance of re-breathing whether it is with soda lime/baralime in a closed or semiopen circuits is completely dependent on our ability to be vigilant and the used of soda/baralime.

[Boomer]

Thanks gas for the further input :)

Who would have thought i would be getting anesthesia CME'S in reefcentral

:rollface::rollface::rollface:

I'll go back to my cave on chem issues I know about before I start post-hole digging myself, with an Anesthesiologist, in his own field :)

[Yogre]

Yeah, you guys are making my head hurt. :lolspin:

I'm going to hook up a system soon, I'll post my results as well. Although, I don't have a controller so I can't post any graphs. As I mentioned earlier in the thread, I've struggled from the get-go with low(er) pH due to a tight house and not being able to keep the windows open much of the year.

Great thread as always here in the chem forum! :thumbsup:

[Boomer]

Take 2 of these and lie down for 1 hr :)

http://blogs.targetx.com/snhu/ChrisDupuy/Advil.jpg

[addicted2reefin]

Boomer, in ur post u stated u need to reach a ph of 10.something to have zero co2. u have it backwards. if u have zero co2 u reach a ph of 10. u cannot manipulate co2 by adjusting alkalinity and ph, but co2 adjusts ph. and this is based on no other buffers in the water other than carbonates and co2. im sure u knew this just thought i would clarify this for the rest :D

[Boomer]

I think your are very confused :) Where do you come up with "backwards". If you take a sample of water and add some CO2 the pH will go down with no effect on Alk. If you take a sample of water and remove the Alk it will have not effect on CO2. If you take a sample of water and add a buffer to it the Alk and CO2 will both increase and in many cases so will the pH.

Here is my post

In regards to your pH. As Randy has stated yes it can get to high. You will see this in heavy planted aquariums, be it FW or SW, where the pH can it over 9 pH. And all from what, the Algae or plants pulling out the CO2 just like the scrubber or limewater. @ 25 C, 35 ppt, 2.5 meq / l Alk, a pH of ~ 10.5 must be reached to have zero CO2

None of what you claim is there in that post. Nowhere am I trying to manipulate anything. And where do you come up with this pH of 10 ? At a pH of 10 in the parameters I gave the CO2 = .0007 ppm and at a pH of 10.5 = .0001 and to be exact at a pH of 10.58 it is zero CO2 and this ~ = About and I said ~(about) 10.5. How do I get this :) From a seawater CO2 calculator, set to Salinity, Temp, pK1 and pK2 @ atm, taken from Luecker et al., 2000. And in FW it is a pH of 10.92

I forgot, if I subtract for Borate Alk the pH is 10.55

http://www.hamzasreef.com/Contents/Calculators/CO2LevelSalt.htm Look in the lower right corner for credit ;)

Just thought I would clarify this for all the readers :D

[Young Frankenstein]

I am more interested in the graph and that PH controller, anyone else using that to get great charts like that one ?

[gasman059]

Thanks gas for the further input :)

Who would have thought i would be getting anesthesia CME'S in reefcentral

:rollface::rollface::rollface:

I'll go back to my cave on chem issues I know about before I start post-hole digging myself, with an Anesthesiologist, in his own field :)

:beer:

BTW I would also like those fancy graph posts.

[addicted2reefin]

ok, i wasnt saying that u were manipulating anything, and i said ph of about 10, cuz i didnt know it was 10.5 or whatever u said.

the only way to effect co2 in anything is to add or subtract co2. i know u are reffering to the kh, ph, co2 charts and alot of people get confused in planted tank with this. they figure that if the ph goes down, then co2 must go up, and they get all confused and add abunch of ph down. well this isnt the case, they are adding another chemical which nullifies the table. if u raise the ph to 10.5 u could still have co2 in the water. this is all i am trying to say, not argue or degrade ur statement at all, sorry if it came off that way. depending on the buffer it may increase/decrase co2, if it will form carbonic acid with the water. kalk binds up the carbon dropping co2 and raising alk, and ph.

if u raise ph with a foreign substance, co2 will stay the same. if u drop ph, co2 will stay the same, at a given alk. i was reffering to this "a ph of 10.5 must be reached to have zero co2". i am just debating that u could raise the ph to 10.5 and still have co2 in the water, u are making it seem that if u raise the ph, co2 drops. it is backwards because u must drop co2 to zero to have a ph of 10.5 at the given alk with no other buffers.

[Boomer]

I'm not confused at all but you still are very, very confused. If you add a buffer, like baking Soda, the Alk goes up, as does the CO2 and the pH can remain the same but depending variables it can also up or down. Meaning, the pH can go down with an increase in CO2 if you raise the Alk by adding buffer but usually as the CO2 is blown off it raises the pH a tad.

The pH and CO2 dictate the Alk. The Alk and CO2 dictate the pH. The Alk and pH dictate the CO2. If you know the pH and Alk you can calculate the CO2. If you known the CO2 and Alk you can calculate the pH. And if you know the CO2 and pH you can calculate the Alk. Adding buffer affects all 3 of them. You are not going to have any CO2 in the water at a pH of 10.5 unless the Alk is very, very, high.

if u raise ph with a foreign substance, co2 will stay the same.

No it will not. If I add baking soda, a foreign substance, the Alk and CO2 will go up and the pH can be the same or could go down or up depending on some variables.

if u raise the ph to 10.5 u could still have co2 in the water

When you raise the pH of water the CO2 is converted Bicarbonate and Bicarbonate is converted to Carbonate. As the pH gets higher all the CO2 is converted to Bicarbonate and Carbonate and there is no CO2. As the pH continues to raise all the Bicarbonate is converted to Carbonate. If I take a sample of water and aerate hell out of it I will drive off all the C02 and the pH will go up and you just said it can't go up.

u are making it seem that if u raise the ph, co2 drops. it is backwards because u must drop co2 to zero to have a ph of 10.5 at the given alk with no other buffers.

It does drop as the pH rises. You seem to think if you have a pH of 8 with CO2 at 2 ppm and the pH rises to 8.5 the CO2 is the same. It is not the same, as the CO2 is converted to Bicarbonate as pH goes up.

CO2_g + H2O ==> H2CO3 + ==> HCO3- ==> CO3--

As the reaction moves from right to left the pH goes down. As it movers from left to right pH goes up

Here, in seawater at 35 ppt @ 25 C 1atm

pH 8, Alk 2.5 meq/ l = 0.9462 ppm CO2

pH 8.3, Alk 2.5 meq / l = 0.4188

pH 8.5 , Alk 2.5 meq / l = 0.2324

Now what is happening here, as the pH goes up, the CO2 drops. Now if we were to increase the Alk at the same rate of CO2 fall, as the pH goes up, the CO2 can remain the same.


pH 8, Alk 2.5 meq/ l = 0.946 ppm CO2

pH 8.3, Alk 5.67 meq / l = 0.946

pH 8.5 , Alk 10.18 meq / l = 0.946



You can also have a higher CO2 at a higher pH

pH 8.0, Alk 2.5 meq/ l = 0.946

pH 8.2, Alk 4.5 meq/ l = 0.997

This will give you a better idea what happens to CO2 as pH rises. Note the flat line for CO2 starting at a pH of around 9 and note how the bicarb and carb shift in their concentration. Note at a pH of ~ 6 it is half CO2 and half bicarb, with no carb and the note at a pH of ~ 9 it is half bicarb and half carb and about zero CO2.

http://bm2.genes.nig.ac.jp/RGM2/R_current/library/seacarb/man/images/big_bjerrum_001.png

they figure that if the ph goes down, then co2 must go up,

How is that, a FW CO2 table is pretty clear, as the pH goes down the CO2 increases.

http://www.tropica.dk/catalog/images/articles/akvaristik/co2table.gif

Some things for you to read, if you can understand it

The Relationship Between Alkalinity and pH.
http://www.advancedaquarist.com/issues/may2002/chem.htm

What is Alkalinity
http://www.advancedaquarist.com/2002/2/chemistry

[euromomtx]

I just wanted to say THANKS for posting this thread. I've been thinking of getting the CO2 scrubber for awhile but didn't think I could afford the 30 bucks a pop for refills so the link to the filterguys was great.
I got my filterguys package and tried out the scrubber/media and now I am exactly where I want to be.
Before daily high/low: 7.7 to 8.25 (I did run an airline from skimmer intake to window)
After CO2 media added high/low: 7.8 to 8.35 Yay! (just CO2 scrubber, no more airline to the window :) )
And with the refillable cartridge the media only cost me $10 per refill :)

Thanks! :)

[Boomer]

Karin keep us updated on how long the media lasts :)

[porthios]

karin? :)

[euromomtx]

I replaced the media last week so that would have been a bit short of 1 month. I bet I did it too early though. It was just lightly purple.
I'm sorry but I am a terrible test person because I also changed other things around:
I got a bigger sump (from 20 gallon to 50 gallon) which seemed to have cut my swing from a 0.5 down to only 0.3 swing range. (I have a very large refugium on opposite to DT light cycle now)
I also am dosing a more saturated ATO of kalk.
In short I no longer struggle with low pH at all but I also did 3 things at once and can't say for sure how much each of these impacted this improvement.

[porthios]

awesome, ty :)

[gasman059]

so far so good in my system- media been running for about 2-3 weeks and all is well.
my next replacement will be medical grade soda lime that should last perhaps longer. I will report back my findings, if there's any improvement.