High volume AND High TDS RO/DI issues

[Herpervet]

I use about 60 gallons of ro/di water every 3 to 5 days due to high evaporation rate on my large system.

The tap water tds is very high out here and ranges from 400 to over 500.

I am running two 75gpd filmtec membranes in a cascading fashion so that the waste from the first membrane feeds the second membrane. I also have a booster pump to take the pressure to around 80 psi.

Generally I get around 20tds water out of the ro effluent.

I have tried three different di cartriges. Mixed bed resins from two sources (both highly regarded sources) and spectrapure maxcap cartridge followed by a combination of 1/3 canister anion resin then mixed bed resin.

This worked better but still I am only getting a couple of months before I need to change out both the max cap cartrige and the second combination (ani/mixed bed) also.

Recently a friend told me about a cati/ani system from germany that is touted as having by far superior results.

The vendor claims that some fairly highly regarded folks here on reefcentral use this system.

I am curious if this is simply one of those "euro is better" (and really expensive) situations or if there really is a "lab grade" resin that is hands down better than the standard resins we get in the hobby.

From a chemistry stand point it seems to me that the function of these resins should be proportional to the surface area first then the affinity to the ions it is pulling out so I am having a difficult time wrapping my mind around the idea that the german resins could be that much better.




thanks,

Pete

[Billybeau1]

Unique situation. I summoned someone who may be able to help. Hang tight. If not tonight, you'll get an answer in the am. :)

[Boomer]

Your issue is CO2 which depletes the DI. It would be best to run a water softener before the RO/DI.

The vendor claims that some fairly highly regarded folks here on reefcentral use this system.

Where and what are these resins. I think it is nonsense and a sells pitch. There are however Nuclear grade resins. And I think that is what the Spectro-'s are IIRC.

From a chemistry stand point it seems to me that the function of these resins should be proportional to the surface area first then the affinity to the ions

That is correct Pete :D

[Herpervet]

Boomer,

Actually I forgot to meniton I do run a small softener as the first stage.

Explain the C02 issue for me. How does C02 correlate with TDS? I do recall that contact with air will deplete the resin so that makes some sense.

The vendor claims that Stephen Pro uses his system and is very happy with it. I have e-mailed Stephen already.

He also mentioned Anthony Calfo's name.

The next question is what to do next so that I don't have to change resin so often. Once per 6 to 8 months would be much more managable, not to mention the cost.

[Boomer]

Pete

How does C02 correlate with TDS?

It has nothing to do with being exposed to air. High TDS water is often very high in CO2 and CO2 goes right through the RO. The CO2 combines with water on the output of the RO to form carbonic acid, H2CO3, which dissociates in water to form HCO3- and CO3--. These ionic species will contribute to the total anionic load and deplete the DI. This HCO3- and CO3-- will raise the TDS on the output of the RO.

CO2(g) + H20==> H2CO3 ==> H+ + HCO3- ==> 2H+ + CO3--



Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm

[Herpervet]

Thanks Boomer,

Do you have an opinion on what I can do to improve the system?

If I had a little more room I would run an airstone in a second resovoir and plumb that tank to my ro/di and run with the booster pump.

My fish room is getting cramped however. I guess I am looking at adding 2 or 3 more canisters of mixed bed resin?

[Boomer]

Not off hand Pete. Usually a good WS solves the issue. Take a read through Randy's artlice and see if anything else is there.

I also added this to the above post

This HCO3- and CO3-- will raise the TDS on the output of the RO.

Jim is here so maybe he can help you :D

The filterguys

[Boomer]

I might add there are some new high-tech membrane EDI/CDI untis which have little CO2 issue.

Look for links to Liqui-Cel Membrane Contactors

http://www.liqui-cel.com/applications/CO2.cfm

[Thefilterguys]

Pete you are going to get nothing better out of a cati/ani system then what you getting from a mixed bed resin. The guys using cati/ani systems don't use RO and get very low production before they have to regenerate the resin. Regeneration uses hazardous chemicals and is a lot of work.

If you water chemistry was perfect you can expect 7500 ppm of TDS absorption per DI cartridge. With an RO tds of 20 it would give you 375 gallons of production water. If as Boomer suggests CO2 is an issue then all bets are off and your production will be very limited.

Jim

[Boomer]

Jim see new post above

[Thefilterguys]

You really need to give us some production figures so we know how your different resins have performed. You may already be at the peak of resin performance.

Jim

[Herpervet]

Jim,

I'm sorry but I really havn't kept track of production numbers.

It's a very rough estimate but I think the max-cap cartirges were exhausted after about 350-400 gallons at which time the second stage gets rapidly depleted.


I'm sorry but I can't give you very accurate data.

I might try stripping the CO2 using one of the membranes from the link boomer provided but from looking at the site I suspect they are $$$.

I am thinking that simpler might be better however and I might just add 3 or 4 more mixed bed cartriges.

One other idea: Could I run through 1 filmtec membrane then feed the second membrane with the permeate from the first? Even if this required a second booster pump it might solve my problem right?

i.e. drop the TDS to 20 then down to 2 to 4 from the second pass?

If I did the above with 3 membranes: i.e. cascading membranes with the effluent side going to a third membrane. This wouldn't waste as much water right?

Sorry, I'm grasping at straws since the resin costs and constant hassle are frustrating.

[Thefilterguys]

Pete interesting with all the hype the maxcap doesn't seem to live up to the claims.

Boomer the stripper is interesting but with no pricing I also suspect big bucks but I'm sure you'll have pricing for us. If the price were right a lot of people with well water would be lining up for this.

Pete I took a look at you municipal water report but it is very limited with information.

I'm not sure if a second booster pump could perform that task Pete. If CO2 is an issue you could bubble off the CO2 from your RO water and then pass it through your DI but you still have that 20 TDS. Really you should be getting better TDS from your membranes I cant remember if you added the Aquatec auto flush valve?

Jim

[Steven Pro]

I do use an Aquatechnik Kati-Ani unit (as does Anthony), but I don't think the resins are that much superior to anything one can buy from someone like SpectraPure. The big difference is the Kati-Ani is rechargeable and the recharging chemicals are dirt cheap in comparison to the disposable, mixed resin bed DI cartridges that come with RO/DI units.

Looking at your numbers, 400-500 TDS coming into the RO with 20 coming out, that would mean your membranes are rejecting 95-96%, if I did the math right, which seems normal. I would continue to use the RO, but would consider adding a Kati-Ani in place of the disposable, mixed resin cartridges. You would probably start saving money after about a year depending on the cost of the mixed resin cartridges and what size Kati-Ani you get.

The big question that you must ask yourself before purchasing is, are you comfortable doing the recharge? I have been using a Kati-Ani for over 8 years and am very comfortable doing the recharge. But, you must answer that question yourself.

[Steven Pro]

<a href=showthread.php?s=&postid=8317218#post8317218 target=_blank>Originally posted</a> by Thefilterguys
Pete you are going to get nothing better out of a cati/ani system then what you getting from a mixed bed resin. The guys using cati/ani systems don't use RO and get very low production before they have to regenerate the resin. Regeneration uses hazardous chemicals and is a lot of work. The Kati-Ani can operate at up to 10 gallons per hour or 240 gpd in RO terms. My old #2 unit would produce 200-500 gallons of water (it varied seasonally) before needing recharged, which was about 4-6 months of use with my old 55. I upgrade to a #10 set in April of this year, have gotten well over 1,000 gallons out of it (I really can't recall exactly), and it is now due for its first recharge. Recharging the unit is a breeze.

It takes about 5 minutes of work to mix the chemicals and set it up. I then go play with my kids or watch some TV, come back a while later, and it is done and just needs flushed out.

The chemicals though, NaOH and HCl, can be dangerous in the hands of someone inexperienced. But, they are common chemicals that you can buy most anywhere. The HCl is sold at hardware stores for etching concrete. The NaOH is a common drain cleaner. The companies that make and sell these items obviously feel they are safe enough for your average Joe to throw on their driveways or pour down their sink.

[Randy Holmes-Farley]

I agree that recharging is a potential advantage for some folks, but it is not something that I'd choose for myself.

FWIW, all issues about the high "purity" of the DI resin are gone once you recharge with ordinary chemicals available to DIY'ers. I also do not consider high purity important for reef aquaria at all.

I detail how RO/DI system work here:

Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria
http://reefkeeping.com/issues/2005-05/rhf/index.htm

[Thefilterguys]

<a href=showthread.php?s=&postid=8317673#post8317673 target=_blank>Originally posted</a> by Steven Pro
The Kati-Ani can operate at up to 10 gallons per hour or 240 gpd in RO terms. My old #2 unit would produce 200-500 gallons of water (it varied seasonally) before needing recharged, which was about 4-6 months of use with my old 55. I upgrade to a #10 set in April of this year, have gotten well over 1,000 gallons out of it (I really can't recall exactly), and it is now due for its first recharge. Recharging the unit is a breeze.

It takes about 5 minutes of work to mix the chemicals and set it up. I then go play with my kids or watch some TV, come back a while later, and it is done and just needs flushed out.

The chemicals though, NaOH and HCl, can be dangerous in the hands of someone inexperienced. But, they are common chemicals that you can buy most anywhere. The HCl is sold at hardware stores for etching concrete. The NaOH is a common drain cleaner. The companies that make and sell these items obviously feel they are safe enough for your average Joe to throw on their driveways or pour down their sink.


Steve Are you running RO or just the cati/ani system? What is your TDS going into your housings and how large are your DI housings? Most people I have talked to say they get very low yield but they are trying this with high TDS. You are the first I have seen with good results. A little more explanation on regenerating would be good since you have years of experience? Do you experience one resin exhausting more rapidly then the other?

Jim

[Thefilterguys]

<a href=showthread.php?s=&postid=8317218#post8317218 target=_blank>Originally posted</a> by Thefilterguys
Pete you are going to get nothing better out of a cati/ani system then what you getting from a mixed bed resin. The guys using cati/ani systems don't use RO and get very low production before they have to regenerate the resin. Regeneration uses hazardous chemicals and is a lot of work.

Steve don't take my comments wrong but you are the first person reporting really good results. The darkside I painted are from all reports I have had up to this time hopefully you are painting a brighter picture.

Jim

[Steven Pro]

I do not run RO, just the DI. Although, I did add a common household water filter before the Kati-Ani and use a 0.5 micron carbon block filter in there.

The #2 set I had was approximately 2.5" in diameter and 24" tall. My new #10 set is about 6" in diameter and 36" tall, so these are significantly larger than the standard 10" mixed resin bed cartridges available. I have heard of people getting low yields with DI-only unit's made by Aquarium Pharmaceuticals and Kent, but as I recall, both are rather small.

I don't have a TDS meter. Actually, I did just get one, but have yet to open up the box and use it. I just recharge them when about 3/4ths of the color changes.

Regenerating is fairly easy. You dilute the chemicals and allow them to drip through each half of the Kati-Ani for about 30 minutes, similar to setting up a kalkwasser drip. Then just flush them out and they are ready to go.

[Steven Pro]

<a href=showthread.php?s=&postid=8318563#post8318563 target=_blank>Originally posted</a> by Thefilterguys
Steve don't take my comments wrong but you are the first person reporting really good results. The darkside I painted are from all reports I have had up to this time hopefully you are painting a brighter picture.

Jim No problem. Kati-Ani units have never been real popular or widely available. Most people with experience with DI-only units are using small Aquarium Pharmaceuticals or Kent units and are not happy with them. They seem to taint the discussion.

[Thefilterguys]

OK that clears some things up and your right about small housings, most are using 10" cartridges. The last person I questioned, after flushing was only getting forty gallons of pure water with 10" cartridges per regeneration. One resin would last three times as long as the other. Regeneration is done out side of the housings and cartridge correct?

You never did give us you tap water TDS do you know?

Jim

[Steven Pro]

Regeneration is done out side of the housings and cartridge correct?
No, not with the Kati-Ani. You regenerate inside the unit.
You never did give us you tap water TDS do you know?
I just checked it and it was 280.

[rick rottet]

I also use the Aquatechnics Kati/Ani. (not that I'm a "highly regarded folk")

Tap water TDS = 680 - 760

I am using the same series 10 as Steven. I can get less than 300 gallons at -0- TDS when running straight tap water. By 350 gallons, the TDS would read higher the tap water (which I don't understand how that is possible, but thats what the monitors read). The series 10 is advertised to be able to process 9,800 gallons of "very hard" water before needing recharged.

After I installed (4) 100 GPD RO membranes before the DI set, the TDS exiting the RO was around 8 and I could run about 6,000 gallons of RO product water throught the DI before the TDS reading would creep up to 2. BUT, there would have been 18,000 to 24,000 gallons of water wasted, plus the iron level in my tap water would plug and clog the membranes in that same two months.

I installed an aspirating iron removal system (Marlo, Inc.). Tap water TDS is still around 580 - 620 after the iron removal system, but no more membrane troubles in about a year. I can still get about 6,000 gallons between recharges of the DI, maybe could get more, but I like to recharge when it goes from -0- to 2.

I would like to say, I agree with Steven. Recharging the units is fairly simple. Fill a big plastic container with water and the chemical (muriatic acid for the kati, sodium hydroxide for the ani) and let it siphon through the DI units, then rinse them through when the recharge is done.

[honeybee]

I too am using the Aquatechnics Kati/Ani units. I use rain water stored in a concrete cistern. The TDS is about 40 but I started with the resin columns because of high nitrates and phosphates. I now run the cistern water through a Pur-FloII with booster pump which reduces the 40TDS to 1TDS I expect the #2 column will last a long time. I will recharge when the Kat column is down 80%. I like the idea of reusing the resin rather than filling the land fill with DI cartiages.

Honeybee

[Boomer]

rick


Couple of quick ones ?

1. What is the vol. ratio of water to HCL in the container ?

2. Vol of sodium hydroxide to water ?

3. What do you mean by siphon or do you mean just let the cartridge fill and then let the water run out.?

4. Shouldn't there be a time constraint, as in x min in container ?

[Steven Pro]

1.) 0.5 liters of 30% HCl to 3 liters of water parts waterfor #1 size unit, twice those amounts for #2, 5 times for #5, etc.

2.) 80 grams of NaOH to 3 liters of water for #1, .....

3 & 4.) You should adjust the flow rate of the chemicals so that it takes 30-45 minutes to run through. It is then allowed to sit inside the unit for another 15 minnutes before flushing.

[Boomer]

Thanks Steve :D

Adjust flow rate how ? Are you using a solution container which feeds the top of the unit and using a valve at the bottom of the unit to control a drip rate/flow rate = 30-45 min ? And then closing the valve, refilling it with new solution for 15 min, draining it and then flushing it with RO/DI water ?

[Steven Pro]

I use a large carboy thing with a valve on the output and mount that above the Kati-Ani so that gravity draws the chemicals into the unit. Once all the acid or base solution has run into the unit, I let it sit there for another 15 minutes. I then flush it out with the tapwater after it goes through the carbon block filter.

[Boomer]

Ok, I suppose there are different ways of doing it. I was asking as normally it is one hr for resin and you are at about that. The statements were confusing.

Meaning;
Was it fill it up and then let it drip through the unit for 30-45 min. and then fill it to sit for another 15 min or just let it fill-up in 30-45 min and then sit for 15. Either would work. The first would be best but I doubt it would really make any difference. There would be more than enough H+ and OH-.

[Thefilterguys]

Are these Aquatechnics Kati/Ani units still being made I would like to see their site?

Jim

[Herpervet]

A gent named Kip Tani distributes them here in the states. I don't believe he has a web site however. His e-mail address is:

reefware@yahoo.com

[Thefilterguys]

Ok anyone have pictures so we can see what these things look like?

Jim

[Steven Pro]

Here is the Aquatechnic website, but it is all in german.

http://www.aquatechnic.de/

[Thefilterguys]

<a href=showthread.php?s=&postid=8324859#post8324859 target=_blank>Originally posted</a> by Steven Pro
Here is the Aquatechnic website, but it is all in german.

http://www.aquatechnic.de/

Steve that link doesn't work but this one does. Are you using what looks like the red and yellow reactors?

Jim

http://www.aquatechnic.de/autoframe1.htm?url=http://www.aquatechnic.de/kati.htm

[Steven Pro]

Yes, this is it.

http://www.aquatechnic.de/images/kati_Kopie.jpg

[rick rottet]

i mix 1.5 gallons of the acid to 7 gallons of water.

800 grams of sodium hydroxide to 7 gallons of water.

by siphon, i mean that i stick a poly hose into the plastic container/chemicals, the other end of the hose connects to the DI container, a second hose leads from the container to the sink, then i spit-start a siphon from the sink end of the hose to draw the chemicals through the DI.

yes, i belive the instructions say the chemicals should take about 30 minutes to run through, then be left to sit for another 15 minutes. (although, i don't have the instructions anymore, but when i did, i found that with the plastic container sitting about 4 inches above the DI units, the run-through time was just about right)


edit...oooops, posted before i noticed there was a second page and y'all had already covered the info... :P

[Boomer]

Ok, I got the scoop on the Liqui-Cel Membrane Contactors for CO2 removal. A small mini unit, for a RO 50-200 gal / d, is $200, plus you need to get an inexpensive vacuum pump, another $100. So, figure $300 -$ 400 depending on pump, if you do not have such a beast sitting around :D

[SpectraPure]

I would like to belatedly ask a few questions of the original poster about your RO system and tap water, to try to figure out if your stated capacity of the MaxCap and SilicaBuster cartridges are within their norms and to perhaps determine what level of CO2 you may have in your water.

1.) What is the ratio of concentrate-to-product flow rates? (If not enough concentrate is sent to drain, product water TDS will be high.)

2.) What is the pH of your tap water?

3.) What is the bicarbonate alkalinity (carbonate hardness, kH) of your tap water?

With the pH and bicarbonate alkalinity in kH we can indirectly calculate the CO2 level of your tap water. See our SpectraPure FAQ on this subject:

http://www.spectrapure.com/faq_p0.htm#calcc02

It is best to use a CO2 test kit on RO water for the most accurate results. A good CO2 test kit can be had from LaMotte:
part # PCO-DR, code # 7297-DR.

4.) Measure the TDS of each membrane separately to see if both membranes have the same TDS output (one or both membranes could be bad).

Comments on other questions posted on this thread:

1.) First of all, the rejection of your 75 GPD FilmTec membranes is on the low end of FilmTec’s specifications. Your numbers indicate a 95-96% rejection factor. Note that not all FilmTec membranes are 98% rejection. SpectraPure Select Membranes guarantee a minimum of 98% and would double your DI cartridge life, because the RO TDS would be 8-10 ppm instead of 20 ppm.
See our sticky thread on this subject at our Reef Central Forum.

2.) You also initially state you use 360 to 600 gallons of RO/DI water per month for evaporation replacement. Do you use more than one MaxCap DI cartridge in one month or just one cartridge? You also go on to say, “I am only getting a couple of months of use before I need to change out both MaxCap and the second SilicaBuster cartridge”. If you just purchased the MaxCap alone and not as part of a kit or system, you should see our Operating Manual for the MaxCap series:

http://www.spectrapure.com/manuals/MAXCAP_RODI_MANUAL.pdf

3.) Water softeners are useful for removing calcium and magnesium hardness from the water, but do not remove bicarbonate alkalinity or affect CO2 levels. If your water contains high CO2 levels, hollow fiber membrane degassifiers are becoming a less expensive means of eliminating CO2 than they used to be.

4.) When speaking of resin capacity, the MaxCap DI cartridge has a total capacity of approx. 18,000 ppm-gallons, vs. about 6000 ppm-gallons for a high-quality mixed-bed cartridge of 700 ml volume (the typical 24 oz. screw-on DI shell). When calculating the approximate gallons a DI cartridge will process, one must account for the total ionic load, both cationic and anionic, presented to the resin cartridge – not just the TDS reading. The presence of CO2 can be a huge factor that must be added to the TDS reading of the water presented to the DI cartridge. Many times the CO2 can be far in excess to the TDS reading.

5.) To calculate the effects of CO2 on DI production, divide the CO2 product water concentration in ppm by the sum of the CO2 concentration in ppm plus the product water TDS in ppm. For example, if you have 4 ppm TDS and 4 ppm CO2 in your RO water, you are wasting 4/8 or 50% of your anionic DI capacity on CO2 removal.

6.) On regeneration of separate bed DI resins. The strong acid cation resin regeneration is fairly straightforward but requires special safety, storage and handling considerations, including using a high quality HCl acid. Strong base anion resin, on the other hand, requires much greater care in regeneration to restore it to its original capacities. First of all, a very high quality sodium hydroxide must be used that is free of any chlorates. Low-grade technical caustic typically contains chlorate that will oxidize the anion resin, ultimately destroying its capacity. It is best to use Rayon grade or Mercury-cell grades of caustic that are purified to remove the chlorates. Always preceed the DI resins with a good sediment and carbon filter to remove particulates, chlorine and organics that can oxidize and foul the anion resin. When regenerating, it is most important to raise the temperature of the caustic regenerant to a temperature of 140 deg.F. This is necessary to solublize the colloidal silica and organics that precipitate and foul the resin, greatly reducing its capacity. Although I have never seen this mentioned in any of the FAQs in the aquarium literature, this is a commonly accepted practice to maximize the capacity and longevity of the anion resin. Of course, raising the temperature of a caustic to 140 deg.F requires special handling, ventilation, and other safety measures.

Charles Mitsis
President
SpectraPure, Inc.

[Boomer]

3.) Water softeners are useful for removing calcium and magnesium hardness from the water, but do not remove bicarbonate alkalinity or affect CO2 levels

Nobody said they did Chuck ;)

With the pH and bicarbonate alkalinity in kH we can indirectly calculate the CO2 level of your tap water

Nomograms are rather crude at that. It is much easier to use a CO2 calculator for FW. :D If you have a good pH meter and TA ( Total Alkalinity) kit you will not need a CO2 kit.

http://jerbaker.dhs.org/fish/calculators.html

3.) What is the bicarbonate alkalinity (carbonate hardness, kH) of your tap water?

They do not measure that but TA. However, in FW it is almost all carbonates unless the water is high in phosphates.


Thanks for all the added info.

[Herpervet]

I work nights and am leaving town until tomorrow evening but I will try to answer your questions when I return.

Thanks for the well thought out questions. I will do my best to answere accurately.

Pete

[Herpervet]

Charles,

I re-checked the tds out of my ro membranes yesterday and after a good flush it was 14. That is starting tds of around 450 to 500 so that is around 97% efficiency right?

I have not been religous about flushing the membranes so I'm sure I am hitting that di resin with high tds when I crank it up but I only turn it on every 4 days to make the water so the resin isn't getting hammered several times a day.

I went back and figured out the water production and I generally have to top-off 60 gallons every 4 days. Based on this and the date I ordered the cartriges I have produced around 500gallons of water for each max cap before it exhausted.

That is certainly a big improvement over my results before the max cap but it is still a significant expense when you are using one a month.

That is without doing water changes. I need to crank out between 150 and 300 gallons a month to do water changes also
so I am probably looking at more like 1.5 a month.

I plan on adding a third ro membrane with the production water of the first two feeding the third. This should drop the tds exposure to the di resin and hopefully cut down on the resin cost.

What do you think?

[rick rottet]

<a href=showthread.php?s=&postid=8330828#post8330828 target=_blank>Originally posted</a> by SpectraPure
6.) On regeneration of separate bed DI resins. The strong acid cation resin regeneration is fairly straightforward but requires special safety, storage and handling considerations, including using a high quality HCl acid. Strong base anion resin, on the other hand, requires much greater care in regeneration to restore it to its original capacities. First of all, a very high quality sodium hydroxide must be used that is free of any chlorates. Low-grade technical caustic typically contains chlorate that will oxidize the anion resin, ultimately destroying its capacity. It is best to use Rayon grade or Mercury-cell grades of caustic that are purified to remove the chlorates. Always preceed the DI resins with a good sediment and carbon filter to remove particulates, chlorine and organics that can oxidize and foul the anion resin. When regenerating, it is most important to raise the temperature of the caustic regenerant to a temperature of 140 deg.F. This is necessary to solublize the colloidal silica and organics that precipitate and foul the resin, greatly reducing its capacity. Although I have never seen this mentioned in any of the FAQs in the aquarium literature, this is a commonly accepted practice to maximize the capacity and longevity of the anion resin. Of course, raising the temperature of a caustic to 140 deg.F requires special handling, ventilation, and other safety measures.

Charles Mitsis
President
SpectraPure, Inc.



I sent off an email to Aquatechnic asking them about heating the caustic (sodium hydroxide). I get mine from the chemistry store (.com).

Dear M Reib and other concerned Sirs,
A specialist has told me that in order to recharge the ani, the caustic solution (sodium hydroxide solution) must be heated to 140 degrees farenhiet.
Is this a beneficial practice?
Thank you for your attention,
Rick Rottet - A Prairieland Reef

I plug that into Google language tools and sent this;

Liebes M Reib und andere beteiligte Herren,
Ein Fachmann hat mich erklärt, daß, um das ani neuzuladen, die ätzende Lösung (Natriumhydroxidlösung) zu 140 Grad farenhiet geheizt werden muß.
Ist dieses eine vorteilhafte Praxis?
Für deine Aufmerksamkeit danke,
Rick Rottet - Ein Prairieland Reef

They sent me back this;

Sehr geehrte Damen und Herren,

das Natriumhydroxid bitte NICHT erwärmen!!!

Mit freundlichen Grüssen

M. Reiss

AQUATECHNIC

which again I plug into google to get this

Ladies and Gentlemen, the sodium hydroxide please do not warm up!!! Yours sincerely M. Tear AQUATECHNIC



I don't want to start a big argument, and I'm not trying to flame anybody. I just want there to be responsible information presented. I am not a chemist nor any kind of water filtration expert (although, if you saw what my tap water made my prefilters look like before I put in all of my filtering systems, you would see that I do have a good working knowledge of at least the mechanics of it all, and I do understand ion exchange, but more towards biological functions and human physiology.)

I can fathom that heating a solution might make the recharge process more efficient (adding heat to a chemical reaction usually does).... but is it practical for the average hobbyist to heat a caustic solution to 140 F? I don't think so. In fact, I think it is dangerous to heat the caustic to that temp. This thought seems to be backed up by my e-mail to Aquatechnic, and several conversations I have had with a college professor who told me to NEVER heat up the caustic. Personally, I think it was a little irresponsible to even mention doing it in a public forum, other than to try to steer people away from buying separate bed DI and towards buying (and re-buying over and over) a mixed bed DI. I understand that helping people with accurate information is a good form of advertising and creates faithful customers, however, one must consider how many people out there are actually going to try this at home!!! It may be accepted practice for those with access to the proper equipment, and the need for every technical absolute maximum capacity from their filtering equipment, but I would hardly regard the process as "most important" for our purposes. The ion exchange will occur and will be quite adaquate for our purposes. I mean, how much better water can we get (practically) than to have -0- TDS, and if run through an RO membrane first, 97 % - 99 % reduction in organics (including silicates), and to get that quality of water for a decade or more? Most of the filtration technicians I have talked to tell me, "if you can't get it with RO/DI, you can't get it".

Something else I have never seen addressed in any aquarium FAQ, or filtration supply company FAQ, is how to separate the mixed bed resins so they can be recharged. Disposing of muriatic acid combined with sodium hydroxide (neutral solution) is far less damaging to our environment than disposing of non-biodegrdeable plastic cartridges containing non-biodegradeable resins. I haven't even seen a recycling program by any of the filtration supply companies.

Speaking from my own personal experience, I don't see, nor can I measure by any practical means, any decline in the capacity of the ani (nor the kati) from it's original state. I could process about 300 gallons of tap water through the separate bed DI when it was brand new, and the same holds true two years later. I have been running the DI post-RO for more than a year now, and can still run about 6,000 gallons before the TDS creeps from -0- to 2. Others have used their separate bed DIs for a decade or more without RO and I haven't heard any of them say the DI decreased significantly in capacity until that period of time had passed.

Also, when we recharge the units, the kati is flushed through first, until the water has reached a neutral pH. Then the ani is flushed with water that first runs through the already-flushed kati. When flushed in this manner, the ani is always "behind" the kati in terms of it's used capacity. Since the color change only occurs in the kati unit, there is miniscule chance that the ani would run out of capacity before the kati changes color.

If we use RO membranes before the DI, the amount of colloidal silicates and organics will be minimal, hence lowering the fouling of the ani unit and extending the life of both kati and ani plus lessening the frequency of recharging. Even if the colloidal matter and organics precipitate into the ani unit, if they need to be solubilized by using 140 F caustic, what is the likely hood that this matter will find it's way into the product water running through at 55 - 80 F.

So maybe heating the caustic would make a difference, but how much of a difference compared to the risk and the practicality of the process? AM I going to run, what... 20, maybe 50 more gallons per recharge? Is my resin going to last 12 years instead of 10??

[SpectraPure]

Thank you for your post. We agree with you about the need to be posting responsible information. That is why nowhere in our post did we suggest this be done at “home”, instead we made sure to state not once, but twice that raising the temperature of a caustic “requires special safety, handling, ventilation, and other safety measures”. We would also add that this applies to any caustic at room temperature. But back to the thrust of our post… technically speaking, raising the temperature is “most important” as we stated (here is one reference amongst many teaching this procedure http://www.wqpmag.com/wqp/index.cfm/powergrid/rfah=%7Ccfap=/CFID/928646/CFTOKEN/58533763/fuseaction/showArticle/articleID/1711). We do not imply that YOU should perform this procedure, rather we are trying to bring to the readership technical awareness of the basic principle necessary to solubalize the colloidal silica and various organics that would otherwise precipitate and foul the resin, greatly reducing its silica removal ability, a highly desired property for aquatic applications. This principle was primarily addressing deionizing tap water, not a DI system after RO, which is not as likely to silica foul. The decline in capacity I speak of is not a decline in overall capacity, but a decline in SILICA removal, something that a TDS meter or even a resistivity meter will NOT measure. A colorimetric test kit for reactive silica is required for this. Hopefully this answers some of your questions and more clearly defines the response to what we thought was the original topic.
bh

[rick rottet]

understood. although, I thought the original topic was "High volume and High TDS RO/DI issues".

thanks for clarifying and re-edifying your statements. seems that we agree on more than it appeared.

I was also wondering if you have plans to initiate any type of recycling program for mixed bed resin cartridges, or is it not practical to do so.