Optimizing Carbon Block Life

[tigé21v]

I'm in an area with moderately hard water, with a high ph and treated with chloramines.
(120-150 mg/l, 9.7-10 ph, 2.5 mg/l chloramines. No water softener.)
Current RO/DI setup is .5 micron sediment filter /.5 carbon block/chloramine block before the 90 gpd membrane.
I'm only getting around 250 or so gallons of finished water (4:1 ratio) before I have measurable chlorine after the first carbon block. I know that the chloramine block is catching what is getting through . But I'd like to get more life out of the first block. There's only so many things I could possibly do that I can think of, but I don't know if any of the options would have a measurable (or cost effective) impact. Here's what I think are the options, and I'd like everyone's opinions.

Sediment- switching from a .5 micron to a .35 micron sediment filter. How much gain?

1st carbon block- I already use a .5 micron, there's nothing smaller out there (that I know of). If I switched from the standard sized carbon (2.5 x 10) block to a larger block make a difference? Say, would switching from a 2.5 x 10 to a 2.5 x 20 get me double the life? More than double? Is the contact time/removal a linear relation?
At what level of chlorine breakthrough does damage to the membrane begin?
I've looked at the BRS Chloramine monster time and time again. But I just can't bring myself to pull the trigger. Not so much the price, but more the claims, and the fact that it is a 25 micron block.
Also, do carbon blocks need to , or benefit from "resting"- not having any water passing through them for a period of time?

Membrane- It would be easy enough for me to add another membrane to my system. I could plumb it in so both membranes were still on the system, but only use one at a time. If I added a lower production membrane to the system, that would increase contact time with the carbon block. Since the carbon block's capacity is a product of contact time, it seems the slower the flow the better. But exactly how much more capacity ? As far as decreased production, my normal water needs are about 70 gallons a week, so a smaller membrane wouldn't be an issue. If I needed more water for an emergency, I'd just run both membranes. (And I'd be sure to run some water though the 90gpd membrane on a weekly basis.) I've seen 35 gpd membranes, but do they make even lower production membranes? And do the lower production membranes have the same rejection rate as the more popular 75 gpd (or more) membranes? I really enjoy the DI Max Cap resin savings of my current Spectra Select 99% membrane. It would be kind of silly to save a few bucks on carbon blocks and have to turn around and spend those savings (probably more) on DI resin.

Tap water- Ok, let's go ahead and take this to the extreme.
It would be feasible for me to treat the tap water prior to running it through the system. Fill some barrels, treat them with Prime and do something to lower the ph ( muriatic acid? ), aerate the water for a period of time to blow off the elevated CO2 from treatment, then pump it through the system. It would be fairly easy to automate through my Apex. (Though not very cost-effective, I am sure.)
What exactly would/could the RO/DI system remove with such a setup? If the chlorine has been "removed", is the carbon block catching the "removal" by-products? And if the ammonia has been converted to another form, is the new form better caught by the membrane? And, what is this the effect of this new form of ammonia on the DI resin? Longer or shorter resin life?

Thanks in advance to all who take the time to respond.
OCD/Perfectionists members- please chime in!

 

[Randy Holmes-Farley Verified Community Expert]

Do the carbon blocks you are using get clogged, dropping the pressure and flow rate?

While I've not used or seen any data for the chloramine blocks from BRS, I trust them enough to believe they will work better than their normal carbon blocks (but maybe not last longer).

Since I am not sure what is limiting the lifespan of yours, I cannot be sure what would make one last longer.

As to what the stages in an RO/DI do for chloramine, here are some comments from my articles

Chloramine and the Reef Aquarium - Reefkeeping.com
http://reefkeeping.com/issues/2003-11/rhf/feature/index.htm

Removing Chloramine From Water: Activated Carbon

Another method for removing chloramine from water is with activated carbon (as is contained in most RO/DI systems). In a two step process, the carbon catalytically breaks the chloramine down into ammonia, chloride, and nitrogen gas

C + NH2Cl + H2O à C-O + NH3 + Cl- + H+

C-O + 2NH2Cl à C + N2 + 2Cl- + 2H+ + H2O

where C stands for the activated carbon, and C-O stands for oxidized activated carbon. In this case, as was found for thiosulfate, the product includes ammonia, which is not bound significantly by activated carbon. Consequently, treatment of water with activated carbon will need to be followed up by some method of eliminating the ammonia.

In the case of a reverse osmosis/deionizing system (where carbon is usually part of the prefiltration prior to the RO membrane), the ammonia is partially removed by the reverse osmosis system. The extent of removal by the RO membrane depends on pH. At pH 7.5 or lower, reverse osmosis will remove ammonia from 1.4 ppm-Cl monochloramine to less than 0.1 ppm ammonia. The DI resin then removes any residual ammonia to levels unimportant to an aquarist.

 

[tigé21v]

Do the carbon blocks you are using get clogged, dropping the pressure and flow rate?

While I've not used or seen any data for the chloramine blocks from BRS, I trust them enough to believe they will work better than their normal carbon blocks (but maybe not last longer).

Since I am not sure what is limiting the lifespan of yours, I cannot be sure what would make one last longer.

As to what the stages in an RO/DI do for chloramine, here are some comments from my articles

Chloramine and the Reef Aquarium - Reefkeeping.com
http://reefkeeping.com/issues/2003-11/rhf/feature/index.htm

Removing Chloramine From Water: Activated Carbon

Another method for removing chloramine from water is with activated carbon (as is contained in most RO/DI systems). In a two step process, the carbon catalytically breaks the chloramine down into ammonia, chloride, and nitrogen gas

C + NH2Cl + H2O à C-O + NH3 + Cl- + H+

C-O + 2NH2Cl à C + N2 + 2Cl- + 2H+ + H2O

where C stands for the activated carbon, and C-O stands for oxidized activated carbon. In this case, as was found for thiosulfate, the product includes ammonia, which is not bound significantly by activated carbon. Consequently, treatment of water with activated carbon will need to be followed up by some method of eliminating the ammonia.

In the case of a reverse osmosis/deionizing system (where carbon is usually part of the prefiltration prior to the RO membrane), the ammonia is partially removed by the reverse osmosis system. The extent of removal by the RO membrane depends on pH. At pH 7.5 or lower, reverse osmosis will remove ammonia from 1.4 ppm-Cl monochloramine to less than 0.1 ppm ammonia. The DI resin then removes any residual ammonia to levels unimportant to an aquarist.

Randy,
No issue with the carbon blocks clogging.. They're never in the system long enough to clog.:mad: All kidding aside, my incoming water is somewhere between 130 and 190 ppm, depending on the season.

 

[Buckeye Hydro Verified Sponsor]

Reverse the order of your carbon blocks so that you put the higher capacity block right after the sediment filter. Let your best carbon blocks take the brunt of the chlorine/chloramine.

The concept of each successive filter having a smaller pore size is a good one, but it applies only to sediment filters.

Russ

 

[tigé21v]

Russ,
We exchanged a couple of emails on this subject. My rationale was more along the lines of let the cheaper blocks take the beating and have the chloramine block play the part of doing the finishing work/ being the safety net in case I didn't catch the chlorine getting through the first carbon block in time. Also done under the assumption that I would get longer life out of the more expensive block.
Does anyone run dual chloramine blocks in lieu of a carbon/ chloramine combo?

 

[Buckeye Hydro Verified Sponsor]

Absolutely.

I understand your rationale.... but how is that working working out?

 

[tigé21v]

lol... not as well as I had hoped. It may be better to say, I'm honestly not quite sure. I guess I need to try reversing the two and see what kind of results I get.
But with the chloramine block in front of the carbon block, what purpose is the carbon block fulfilling?
Again, my line of thought may be way off base. And I cannot seem to find the right analogy to use as a comparison. I guess the best I can come up with is waxing a car- you could walk outside and start waxing it, but you'll get better results from the wax if you wash and dry it first.
I hope this doesn't come across as argumentative, because that is not my objective. Just trying to better understand.
And, it may be that I'm making a mountain out of a molehill. The results I'm getting may be just that- the results I get. Nothing I can do will significantly change it. Just get a case of .5 micron blocks and accept changing it out every month or so.

 

[Buckeye Hydro Verified Sponsor]

No worries - I'm not thinking you're arguing.

Think about it this way - you have two jobs for the two carbon blocks. One job is really hard (take ~3 ppm chloramine or chlorine down to almost 0), and one job is easy (take just greater than 0 ppm chloramine or chlorine down to almost 0). Give the better quality block the harder job, and the lower quality block the easier job.

With your current configuration, you have the the roles reversed. In short order you blow through the capacity of the lesser block, and functionally - what are you left with? Just one functioning block, proceeded by a faltering block.

Russ

 

[Buckeye Hydro Verified Sponsor]

And if that doesn't make sense to you, then just do what I say.

 

[tigé21v]

To test for chlorine breakthrough, would I want a total chlorine test or a free chlorine test? Also, I know Hanna needs the high ph neutralized. How would I go about this? Are there any test kits out there that will give accurate results at elevated ph levels?

 

[Buckeye Hydro Verified Sponsor]

Because you have chloramines in your water, I'd test for both. Not certain what Hanna meter you're using, or what its limits are.

Russ

 

[Randy Holmes-Farley Verified Community Expert]

To test for chlorine breakthrough, would I want a total chlorine test or a free chlorine test? Also, I know Hanna needs the high ph neutralized. How would I go about this? Are there any test kits out there that will give accurate results at elevated ph levels?

I'd just use a total chlorine kit as for this purpose, since you do not care what form it takes. Any form should not be present.

What pH are you worried about? Tap water often has pH up to 9.5 and the kits work fine.

 

[AZDesertRat]

I would suggest trying a 0.2 or 0.35 micron absolute rated sediment filter. Even though you may not be seeing physical signs of plugging or fouling of the carbon block it doesn't take much to plug the microscopic pores rendering them useless for adsorbing chlorine.

 

[tigé21v]

What pH are you worried about? Tap water often has pH up to 9.5 and the kits work fine.

Hanna told me that for the total chlorine test kit, I would have to neutralize the ph. I believe it has to be below 8.0 for accurate results.
What would I use to neutralize it?

 

[Randy Holmes-Farley Verified Community Expert]

Hanna told me that for the total chlorine test kit, I would have to neutralize the ph. I believe it has to be below 8.0 for accurate results.
What would I use to neutralize it?

Vinegar should work OK.