GPH through carbon

[steve 1965]

What’s the recommended flow rate through a carbon reactor?

 

[Timfish]

To be honest I've never worried about flow and have used pumps rated from a few hundred GPH to 8 or 9 hundred on my GAC/GFO reactors. But generally, the longer the contact time the better. So maybe as slow as one tank turnover an hour might be good?

 

[steve 1965]

Yes that’s what I was thinking.

 

[Randy Holmes-Farley Verified Community Expert]

The attributes are that you do not want the flow to be too slow, and do not want it high enough that the GAC is bouncing around, breaking itself up. Higher is better if it stays put and doesn't break up.

I DO NOT agree that one wants to optimize contact time. That is a misunderstanding. GAC is not a single pass system where one would want to have decent contact time.

Higher flow is not ever a drawback to the binding. It brings in dirty water faster and thus keeps dirtier water in contact with the GAC, binding more.

 

[steve 1965]

The attributes are that you do not want the flow to be too slow, and do not want it high enough that the GAC is bouncing around, breaking itself up. Higher is better if it stays put and doesn't break up.

I DO NOT agree that one wants to optimize contact time. That is a misunderstanding. GAC is not a single pass system where one would want to have decent cotnact time.

Higher flow is not ever a drawback to the binding.

What if I want to use ROWAPHOS?

 

[Randy Holmes-Farley Verified Community Expert]

What if I want to use ROWAPHOS?

Same ideas exist. Low flow to increase contact time is not desirable. Higher flow is better for a faster tank effect unless it is causing pulverization of the material, or channeling through it.

That said, one does not need to have especially high flow as it is not generally needed or desirable to have either of these materials (GFO or GAC) act quickly.

I'm mostly arguing against the concept of contact time having any useful meaning. The materials are ALWAYS in contact with the water, and the dirtier the water the better for more binding over time.

 

[steve 1965]

Thank you Randy

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome.

Happy reefing. :)

 

[steve 1965]

How about if it’s in a media bag? Is it the same idea. Maybe about one turn over an hour?

 

[Randy Holmes-Farley Verified Community Expert]

How about if it’s in a media bag? Is it the same idea. Maybe about one turn over an hour?

Flow through a media bag is very hard to assess in many situations, relative to a reactor. But yes, ideas are the same. Some parts of a media bag may get little flow though it, especially with GFO, so it can be useful to manually mix it around occasionally before declaring it is used up. I used to mix GFO and GAC to get better flow through them, since the larger GFO particles opened up the material to flow somewhat.

 

[steve 1965]

Yes I’ve heard that the two could be mixed. Say 1/2 cup for GFO TO 1 cup of GAC? How about in a reactor. Can it be mixed together ?

 

[Randy Holmes-Farley Verified Community Expert]

Yes I’ve heard that the two could be mixed. Say 1/2 cup for GFO TO 1 cup of GAC? How about in a reactor. Can it be mixed together ?

That is how I used it, in a BRS reactor using ROX 0.8 carbon and BRS GFO.

 

[Timfish]

@Randy Holmes-Farley Who said anything about single pass use? :grinning-face-with-smiling-eyes: My own experiences using powdered GAC in diatom filters have shown pretty quick removal of the brown tint from aquarium water in just an hour or two with just the flow rate of a vortex pump (whatever that was).

From the abstract for this paper looking at empty bed contact time (EBCT) for removing micropolutants:

"Regardless of the GAC-type, a minimum EBCT between 20 – 30 min was necessary. We proved that a short EBCT would not fully use the sorption capacity, whereas a long EBCT would increase the carbon demand without improving of the removal."


@steve 1965 If you have a small pump that will just do one turnover an hour by all means use it. But like I said, I use anywhere from a couple hundred to 8 or 9 hundred. It is important to rinse well and not to tumble activated carbon to help prevent activated carbon from generating the dust that causes irritation to fish lateral line and causing errosion of the skin.

And if you want to go down a rabbit hole here's a link on GAC and EBCT :D
https://scholar.google.com/scholar?...rbon+empty+bed+contact+time&hl=en&as_sdt=0,44

 

[steve 1965]

I am using a small DC pump so I can ramp it up. Right now I have it at its lowest setting.

 

[Timfish]

Yes I’ve heard that the two could be mixed. Say 1/2 cup for GFO TO 1 cup of GAC? How about in a reactor. Can it be mixed together ?

I use both like that often, the ratio I use depends on the current PO4 level. You do want to check you PO4 levels and be sure not to drop it below the .03 mg/l threshold identified by researchers at Southampton University.

 

[steve 1965]

I use both like that often, the ratio I use depends on the current PO4 level. You do want to check you PO4 levels and be sure not to drop it below the .03 mg/l threshold identified by researchers at Southampton University.

Ok thanks

 

[steve 1965]

What if I wanted to use ROWAPHOS to control po4.

 

[Randy Holmes-Farley Verified Community Expert]

@Randy Holmes-Farley Who said anything about single pass use? :grinning-face-with-smiling-eyes: My own experiences using powdered GAC in diatom filters have shown pretty quick removal of the brown tint from aquarium water in just an hour or two with just the flow rate of a vortex pump (whatever that was).

From the abstract for this paper looking at empty bed contact time (EBCT) for removing micropolutants:

"Regardless of the GAC-type, a minimum EBCT between 20 – 30 min was necessary. We proved that a short EBCT would not fully use the sorption capacity, whereas a long EBCT would increase the carbon demand without improving of the removal."


@steve 1965 If you have a small pump that will just do one turnover an hour by all means use it. But like I said, I use anywhere from a couple hundred to 8 or 9 hundred. It is important to rinse well and not to tumble activated carbon to help prevent activated carbon from generating the dust that causes irritation to fish lateral line and causing errosion of the skin.

And if you want to go down a rabbit hole here's a link on GAC and EBCT :D
https://scholar.google.com/scholar?...rbon+empty+bed+contact+time&hl=en&as_sdt=0,44

Who said it? I did. And that is what is misleading you. The paper you post is a single pass analysis through the GAC beds. Look at Figure 1 and the collection points P1-P14. They are after a single pass through the GAC. They are not recirculating the tank water over and over through the GAC, but giving it only one chance at the water.

Of course contact time being higher matters in such a setup. It does not in a recirculating setup which is how reefers use it.

 

[Timfish]

Who said it? I did. And that is what is misleading you. The paper you post is a single pass analysis through the GAC beds. Look at Figure 1 and the collection points P1-P14. They are after a single pass through the GAC. They are not recirculating the tank water over and over through the GAC, but giving it only one chance at the water.

Of course contact time being higher matters in such a setup. It does not in a recirculating setup which is how reefers use it.

My bad on not reading the paper through. :D It's nice to know though I can setup GAC for a single pass in 30 minutes an emergency if I need to.