DIY CO2 scrubber questions

[Righteous]

I've had consistent issues with low pH (7.8) for most of the life of my tank(s) due to high C02 in my house. So I'm about to set up a DIY CO2 scrubber. I was going to use tmz's juice containers as a blueprint (as seen in http://www.reefcentral.com/forums/showthread.php?t=2092232&highlight=a+tank+of+the+month), but was wondering about the slots on the bottom and the flow in general. How many/ how big should the slots be? And is there a way to determine if the setup is interfering with the flow to the skimmer? Does anyone have issues with soda lime dropping out the bottom of these things (my understanding is that it's pretty caustic). Any pointers are appreciated!

 

[oblio]

Instead of adding more "stuff" to your system, have you added an external air intake to the skimmer? (assuming your running a skimmer) I live in Florida so house is closed 11 months of the year, run an external air feed to the skimmer, you will get .2 ->.3 back in PH. That will put you in a good place.
I pull air from the attic, to a canister with some carbon and felt for rudimentary filtering, then from there to the skimmer intake. Worked for me.

 

[Righteous]

have you added an external air intake to the skimmer?

I have considered doing that, but I can't figure out a good way to manage it. My tank is next to 2 outside walls, but being a newer house in New England, both walls are full of insulation, so I can't really drop a line down from the attic. (I can't even feed lines a few feet down the wall because of the insulation) I've thought about drilling a line in the wall to the outside, but I'm concerned about ice and moisture etc building up in the wall.

Part of the issue is that my house is basically sealed up 12 months out of the year. I have horrible allergies in both the spring and fall, and then we're cooling and heating in summer and winter, so it's basically always sealed up. I opened up all the windows one day last fall as an experiment, and sure enough the tank pH went up to 8.1, but I ended up with a headache for 2 days, and the pH dropped again quickly once closed. I periodically take pH tests and compare a sample with one I take outside and expose to air for a couple minutes, and it's usually a .2 to .3 difference, so it seems pretty certain to me it's the CO2.

So the scrubber seemed like the easiest solution, but I would love to just use outside air if I could manage it.

 

[tmz]

I just slashed up the bottom with a dremmel wheel and glued a couple of small pieces of eggcrate on the bottom edges for feet to raise the bottom allowing air flow. I drew breath through it to see if there was enough opening. You could just hook it up an watch the skimmer/ if you think you have too much air going through and treating room air wastefully a little duct tape can plug some of the extra slots up.

An outside airline can help depending on how high the house CO2 is relative to the atmospheric CO2. That will vary from house to house. If you have to run it for a long distance and use smaller tubing it can also restrict airflow . I have relatively low CO2 in my house and the CO2 scrubber still increases pH. Some run a fresh air line through a CO2 scrubber.

Soda lime is chunky. The slots are narrow enough to hold it . Some small amounts of dust may drop out . I wouldn't let it sit on my skin for very long or inhale it but it's about the same as pickling lime(calcium hydroxide) in terms of causticity.

Soda lime is :

• Calcium hydroxide, Ca(OH)₂ (about 75%) commonly know as pickling lime
• Water, H₂O (about 20%)
• Sodium hydroxide, NaOH (about 3% ) commonly known as lye

• Potassium hydroxide, KOH (about 1%).

from:


http://en.wikipedia.org/wiki/Soda_lime

 

[ReefJunkie01]

Have you looked up CO2 absorbent media running o your air intake of your skimmer?

I had continual PH problems with my reef tank (always revolved between 7.8 and 8.0), I used to get excited when it would get to 8.1 for a half day.

I attempted the following:

Raised alk to 12dkh (I usually run it at 9-10) - Only got me 8.05ph

Used kalkwasser - my Ca and Alk would continually fall off balance, as well as my Ca would get to 450 but the ph would get to 8.

Spoke to wife about running the air intake from the skimmer to outside of the house - spoke to wife about putting a hole in the wall, conversation ended quickly..........

I then looked up other methods and, for those that can't run air lines to outside of the house, two methods to try are ozone generators as well as CO2 absorbent media. as my tank is in my living room, I did not go the ozone route as I did not want to risk leakage of ozone into the living room air.

I use a Bulk Reef Supply media reactor with their color changing CO2 absorbent media. The entrance side of the reactor is open to air, and the exit side runs as a tube directly to my skimmer intake. After doing this, my ph is now contstantly 8.0 to 8.3. Only down side is during the winter, I need to change the media every week, and during the summer I change it twice a month. One container of media will give you about 8-9 media reactor cartridge refills.

 

[Righteous]

I drew breath through it to see if there was enough opening.

Simple yet brilliant! Thanks!

Have you looked up CO2 absorbent media running o your air intake of your skimmer?

Yup, that's what the soda lime is for. I believe its the same as the BRS stuff. I ordered some from here for about $24 for 9 lbs:

http://www.shopmedvet.com/product/soda-lime-3-lb-bag/jorgensen-products-anesthesia-products

So it sounds like I might be going through a pound a week?

I was also reading on Wikipedia and other sources that activated carbon can scrub CO2 and then be regenerated by blowing low CO2 air back through it, but the details of how that works were lacking. Anyone have any experience with that?

And thanks for all the advice!

 

[tmz]

I use the med vet soda lime you note currently. I used soda lime from Airgas ,a national supplier. Either is much cheaper than hobby grade repackaged stuff. The soda lime is primarily used for rebreathers for divers and controlling CO2 in anesthesia applications.

How soon it turns purple/lavender depends on how much CO2 it's processing which can vary from room to room. In my case I go through an average of 3/4lbs per week to feed two scrubbers each of which is attached to a large skimmer. The system involved has about 650 gallons of water. This thread has afew more details on CO2 scrubbers than the TOTM article does:

http://www.reefcentral.com/forums/showthread.php?t=1889552&highlight=co2+scrubber

I'm intersted in seeing what you read regarding GAC and CO2. I've never heard of that. As far as I know granulated activated carbon (GAC) sorbs organics including organic gases from the air or the water; not CO2. To reactivate GAC requires very high heat.

 

[neuwave]

Gac has little ability to absorb CO2 and have met a couple of reefers who tried carbon instead of sodalime. With no success on their tanks. I've been using CO2 scrubber for years. As a renter drilling holes in the apartment wouldn't go well with the landlord. Make sure CO2 scrubber canister can handle the amount of air pulled through the skimmer and the size of your tank. I've seen people get frusterated with them because they put a small Gatorade bottle attached to a 150 gallon tank with a massive skimmer. Without any positive results and the sodalime being used up in a couple days time. On my 60 gallon I have two RO canisters in parallel to absorb enough CO2. My place is pretty closed up tight in florida that the CO2 raises fairly fast.

 

[Righteous]

I'm intersted in seeing what you read regarding GAC and CO2. I've never heard of that. As far as I know granulated activated carbon (GAC) sorbs organics including organic gases from the air or the water; not CO2. To reactivate GAC requires very high heat.

Initially, it was a single paragraph blurb on Wikipedia without a citation on the CO2 Scrubber page. So I did a little research, and there does seem to be some science to support it. I found this paper outlining CO2 adsorption and regeneration.

http://www.ripublication.com/ijame-spl/ijamev4n1spl_05.pdf

It states an adsorption rate of 2.83 mol CO2 / kg AC. So I think the calculation would be

44.01 g/mol (CO2 molar mass) * 2.83 mol CO2 / kg AC = 124g of CO2 / kg AC

I believe a high indoor CO2 level would be 1000ppm or 1 g/L giving 124 L Air / kg AC

I have no idea how much air a skimmer is pulling in, but I'm going to guess 124L goes by pretty quick, hence it would be depleted quickly.

However I did find another paper that discusses increasing the CO2 adsorption capacity of GAC via treatment with heat and ammonia. It's pretty dense stuff, and I haven't processed all of it yet, but it seems interesting.

http://umexpert.um.edu.my/file/publication/00012476_86012.pdf

I might try an experiment of adding a layer of GAC prior to the soda lime, and then without and see if it alters the life of the soda lime.

 

[tmz]

Thanks for the information.

 

[Righteous]

I've started down the rabbit hole here researching GAC and CO2. Maybe this is better for the chemistry forum, but I just found a reference that microwaving AC resulted in 28% increase in it's CO2 absorbing capability.

http://www.sciencedirect.com/science/article/pii/S1385894710003062

Anyone every tried microwaving their GAC (maybe in an attempt to reactivate it)? I'm going to guess this is incredibly dangerous to attempt. :worried: (thinking melt/catch your microwave on fire type dangerous)

I guess I'll have to live with spending $15-$30 a month on soda lime.

 

[neuwave]

I've started down the rabbit hole here researching GAC and CO2. Maybe this is better for the chemistry forum, but I just found a reference that microwaving AC resulted in 28% increase in it's CO2 absorbing capability.

http://www.sciencedirect.com/science/article/pii/S1385894710003062

Anyone every tried microwaving their GAC (maybe in an attempt to reactivate it)? I'm going to guess this is incredibly dangerous to attempt. :worried: (thinking melt/catch your microwave on fire type dangerous)

I guess I'll have to live with spending $15-$30 a month on soda lime.

$15-$30 a month? Whoa!

 

[Righteous]

$15-$30 a month? Whoa!

Is that estimate high? I haven't actually started running yet, so I don't actually know how much I'll be using. I'm basing it off of the numbers here of changing it out every week. Seems like a pound a week would be reasonable, and I'm paying about $3.70 a pound so that would be about $15 a month.

 

[neuwave]

I buy a 5 gallon bucket from airgas. Their price ranges from $65-$80 depending on what their going rate is and sometimes you can talk them down. I refill two ro canisters every 2-3 weeks. Summertime when the house is closed tight every 2 weeks. The bucket can last me a year. Divided out that's around $7 a month. Also if it's for your 8.5 gallon tank your monthly price maybe be even smaller.

 

[Jim28fl]

Bringing this back up i had a thought

Bringing this back up i had a thought

I believe I had an issue related to when the media exhausted, i saw a mini crash due to rapid ph drop after media was exhausted when i first tried this and i stopped messing with it.

Once again, I am considering a 2-4 liter container on a air pump pushing air into my skimmer air intake which is a venturi style and draws from the outside of the house 24/7 and uses a ton of air volume compared to typical skimmers. Then set the apex to turn on air pump thru soda lime reactor to skimmer when ph goes under 7.99 off at 8.00 sort of thing. the rest of the time I would be drawing the usual outside air. If i open the windows.. I'm good to go rather quickly. few hours and tank comes up nicely. if i close the house up in three days i can't get over 8.0 as i have it now. if i shut off the skimmer say for feed mode 4 hours at a occasional phyto night feeding, I drop way down to 7.65 by the next morning. Then it take days to recover. Again living in florida, so its over 85 almost ever day of the year so doors can only be open a few hours in the morning or over night at best few months a years which results in a 8-8.2 ph consistently.. I know indoor c02 is my issue. I try to leave bath room fans on any chance i get n so forth. but i need a solid solution to get the stability i want for my SPS.

Thoughts??? opinions?