100 Nitrate

[mari.harutunian]

Nitrates are high but ammonia? Not good.

That's the ammonia from the rodi. This is the ammonia level in the tank currently.

Zero? Close to zero?

 

 

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[Origami]

Zero to close to zero. The only way to really be confident in that is to take and run a test on some distilled water from the drug store. It should have zero ammonia. 

 

If your DI resin is releasing ammonia (because it's depleted), then large water changes would have likely caused major problems. Because of your biological filter, this was followed by a large nitrate spike (which you detected and then followed up with a big water change!).

 

Maybe we've found the root cause of your failing tank syndrome?

[mari.harutunian]

Zero to close to zero. The only way to really be confident in that is to take and run a test on some distilled water from the drug store. It should have zero ammonia.

 

If your DI resin is releasing ammonia (because it's depleted), then large water changes would have likely caused major problems. Because of your biological filter, this was followed by a large nitrate spike (which you detected and then followed up with a big water change!).

 

Maybe we've found the root cause of your failing tank syndrome?

Sounds about right... I've only had this rodi system for 5 months and my corals became irritated a few weeks ago. Isn't the cartridge that needs to be replaced the soonest still good up until 6 months?

 

 

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[khh27]

When it depletes it depletes. All sorts of things determine that. On mine on well water I go through a cartridge of DI resin about every 100-130g this is because of I think I have high CO2 in my water which depletes it very fast. So do you not have color changing DI resin thay way you can tell physically by it turning from Blue to brown it's exhaustion rate.

 

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[mari.harutunian]

When it depletes it depletes. All sorts of things determine that. On mine on well water I go through a cartridge of DI resin about every 100-130g this is because of I think I have high CO2 in my water which depletes it very fast. So do you not have color changing DI resin thay way you can tell physically by it turning from Blue to brown it's exhaustion rate.

 

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Not that I know of? It came with set dates to replace each filter and that's it. My new one has color changing DI resin though.

 

 

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[Origami]

Think of your DI resin cartridge as being able to catch and hold a fixed number of electrically-charged molecular impurities called ions. As these and water enter the cartridge, the water passes by and these ions get picked up by the resin. This continues until the resin no longer has available sites to grab the next ion. However, to the DI resin, not all ions are created equal. If a more attractive ion passes by, the resin will release the ion that it has and grab the more attractive one. If the DI cartridge is not exhausted, the released ion will get picked up again. However, if the resin is exhausted, the ion will pass thru the resin cartridge and become part of the output stream. This is how you might get a burst of ammonia out of your exhausted RO/DI system.

 

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[Origami]

BTW, when your TDS creeps up (above zero) is time to replace the resin.

 

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[zygote2k]

Ive been running ro and replacing cartridges for 25 years using this method-

when TDS out is greater than 10% of TDS in, replace the cartridges. When you do this and the tds doesn't read zero, it's time to replace the membrane. When replacing membrane, replace the ASOV and capillary flow restrictor.

 

Also- all that food you dumped into the tank took some time to turn into nitrate. what you do today usually shows up next month.

almost like- a moment on the lips, a lifetime on the hips.

 

If the tank is small and you have a myriad of species of coral, some will do well, and some will just die.

[Bruleyii]

a moment on the lips, a lifetime on the hips.

 

Is this your motto? lol

[Origami]

mari,

The ammonia reading you took was from your RO/DI, right? What about that nitrate reading in the same post? From your tank or your RO/DI output?

 

Again, when DI resin exhausts, it starts grabbing ions preferentially for those that it has greater affinity for and releasing ions that it has less affinity for. Therefore, there is the potential for more harm as previously bound silicates and even ammonia are dumped. All TDS readings are not the same. TDS-IN vs TDS-OUT ratios do not provide any insight whatsoever about the composition of the dissolved ions in the input/output of your RO/DI system. 

[mari.harutunian]

mari,

The ammonia reading you took was from your RO/DI, right? What about that nitrate reading in the same post? From your tank or your RO/DI output?

 

Again, when DI resin exhausts, it starts grabbing ions preferentially for those that it has greater affinity for and releasing ions that it has less affinity for. Therefore, there is the potential for more harm as previously bound silicates and even ammonia are dumped. All TDS readings are not the same. TDS-IN vs TDS-OUT ratios do not provide any insight whatsoever about the composition of the dissolved ions in the input/output of your RO/DI system.

The ammonia is the RODI and the nitrate is the tank. Not RODI output.

 

 

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[Origami]

The ammonia is the RODI and the nitrate is the tank. Not RODI output.

 

 

It might be worth testing your tap water for ammonia. The result of that test will give us better insight as to whether your DI resin is concentrating then dumping ammonia. It's an academic question at this point, but one that I'd like to collect a data point on, if you're able. Thanks.

 

Generally speaking, the DI resin has a preferentially higher affinity for large, high valence ions than for small, lower valence ones. This is a generalization. For example, I found this paper that listed the order of affinity for some common cations (postively charged ions that are attracted to a negatively charged cathode) for sulphonic DI resins. The order was shown as

 

Hg2+ <Li+ <H+ <Na+ < K+ ≈ NH4+ < Cd2+ < Cs+ < Ag+ < Mn2+ < Mg2+< Zn2+ < Cu2+ < Ni2+ < Co2+ < Ca2+ < Sr2+ < Pb2+ < Al3+ < Fe3+ 

 

See the NH4+ ion listed 6th from the left. That's an ammonium ion. On the far right is a dissolved ferric (iron) ion, Fe3+.  Calcium is also far to the right (Ca2+). This order shows that iron and calcium, common ions in our water, are more attractive to the DI cation resin than ammonium. Therefore, if a calcium ion floated by a DI resin bead that had hold of an ammonium ion, there would be a statistically greater possibility that it would release the ammonium ion back into the water in order to lock onto that calcium ion. This can, in the case of an exhausted resin, lead to a burst of bad stuff coming out of exhausted resin.

 

The same paper provided a similar list for amine-based anion (negatively charged ions that are attracted to a positively charged anode) resin:

 

OH- ≈ F- < HCO3- < Cl- < Br- < NO3- < HSO4- < PO4_3- < CrO4_2- < SO4_2- 

 

Here you see that nitrates can be dumped in favor of sulfates and phosphates when anion resin is exhausted.

 

If interested in a simple primer on resins, follow this link to an article called Ion Exchange for Dummies. The top of page 7 provides a simple graphic that illustrates what is happening when TDS begins to creep up and the column (DI stage) begins to "leak" ions. You can see from the diagram that it's the first sign that the DI resin is approaching full exhaustion. (This diagram assumes that the resin column is well packed and that there's not a lot of channeling going on.) While one could wait for full exhaustion, the phenomena of ion dumping (where you get a burst of ammonia, for example) makes waiting a bad trade.

[mari.harutunian]

It might be worth testing your tap water for ammonia. The result of that test will give us better insight as to whether your DI resin is concentrating then dumping ammonia. It's an academic question at this point, but one that I'd like to collect a data point on, if you're able. Thanks.

 

Generally speaking, the DI resin has a preferentially higher affinity for large, high valence ions than for small, lower valence ones. This is a generalization. For example, I found this paper that listed the order of affinity for some common cations (postively charged ions that are attracted to a negatively charged cathode) for sulphonic DI resins. The order was shown as

 

Hg2+ <Li+ <H+ <Na+ < K+ ≈ NH4+ < Cd2+ < Cs+ < Ag+ < Mn2+ < Mg2+< Zn2+ < Cu2+ < Ni2+ < Co2+ < Ca2+ < Sr2+ < Pb2+ < Al3+ < Fe3+

 

See the NH4+ ion listed 6th from the left. That's an ammonium ion. On the far right is a dissolved ferric (iron) ion, Fe3+. Calcium is also far to the right (Ca2+). This order shows that iron and calcium, common ions in our water, are more attractive to the DI cation resin than ammonium. Therefore, if a calcium ion floated by a DI resin bead that had hold of an ammonium ion, there would be a statistically greater possibility that it would release the ammonium ion back into the water in order to lock onto that calcium ion. This can, in the case of an exhausted resin, lead to a burst of bad stuff coming out of exhausted resin.

 

The same paper provided a similar list for amine-based anion (negatively charged ions that are attracted to a positively charged anode) resin:

 

 

OH- ≈ F- < HCO3- < Cl- < Br- < NO3- < HSO4- < PO4_3- < CrO4_2- < SO4_2-

 

Here you see that nitrates can be dumped in favor of sulfates and phosphates when anion resin is exhausted.

 

If interested in a simple primer on resins, follow this link to an article called Ion Exchange for Dummies. The top of page 7 provides a simple graphic that illustrates what is happening when TDS begins to creep up and the column (DI stage) begins to "leak" ions. You can see from the diagram that it's the first sign that the DI resin is approaching full exhaustion. (This diagram assumes that the resin column is well packed and that there's not a lot of channeling going on.) While one could wait for full exhaustion, the phenomena of ion dumping (where you get a burst of ammonia, for example) makes waiting a bad trade.

Supposedly my water is high in calcium. Moved here before I started the tank. Lots of hardened calcium around the pipes. The water was probably tested for contaminants but I'll test the ammonia just to know.

Didn't even get cloudy. (Test kit is not expired, held the droppers vertical, added the only 5 mL water etc)

 

 

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[Origami]

Supposedly my water is high in calcium. Moved here before I started the tank. Lots of hardened calcium around the pipes. The water was probably tested for contaminants but I'll test the ammonia just to know.

Didn't even get cloudy. (Test kit is not expired, held the droppers vertical, added the only 5 mL water etc)

That sort of settles it. Your DI resin is dumping ammonia. It's caught the occasional ammonium ion that was in the water and trapped it. Now that the DI resin is exhausted, it's dumping the ammonia. Not so good for you, but I do appreciate your doing the test as it puts it (ion dumping) out there for everybody to see.

 

Is this a regular, multi-stage RO/DI system that you're using or a single stage cylinder that you're using?

[mari.harutunian]

That sort of settles it. Your DI resin is dumping ammonia. It's caught the occasional ammonium ion that was in the water and trapped it. Now that the DI resin is exhausted, it's dumping the ammonia. Not so good for you, but I do appreciate your doing the test as it puts it (ion dumping) out there for everybody to see.

 

Is this a regular, multi-stage RO/DI system that you're using or a single stage cylinder that you're using?

Multi stage and cheapest one I could find on eBay. http://m.ebay.com/itm/110691608751?_mwBanner=1

 

 

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[AlanM]

Are you on a well or city water?  I don't remember reading which you were using.

[mari.harutunian]

Are you on a well or city water? I don't remember reading which you were using.

Well water

 

 

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[Origami]

I can see that the membrane housing is refillable (typical). However, do the other stages have refillable contents? Or do you have to replace the entire stage, plastic housing and all? If the latter, it'll probably get pretty expensive overall.

 

There's a nice Spectrapure unit that was listed in the For Sale forum. You may want to take a look at that.

 

Well water, huh? Like me and a few others here. I'm guessing that you have high dissolved CO2 in the water and that your resin will exhaust very quickly. Sometimes in as little as 100 gallons for a regular sized DI canister. There are strategies to improve resin lifetime on well systems, but I don't yet have first hand experience with them. I'm planning on building something (possibly by the summer) to aerate RO water (to "blow off" dissolved CO2) prior to pushing it through the DI stage.

 

This makes me wonder, I guess: If running with an exhausted DI stage is potentially so bad, then is it better (in cases like ours) to just remove the DI stage and go with RO water only, and just accepting the ions that get through the membrane as an economic compromise?

[Origami]

About the POQ-4B-50...

 

1st stage is a sediment filter. Appears to be a 5 micron sediment filter. $11 to replace this stage according to purewaterclub.com (the manufacturer).

 

2nd stage is granular activated carbon (GAC). $11 to replace this stage.

 

3rd stage is the RO membrane. Should last a while. 

 

4th stage is the DI resin. $13 to replace. Will exhaust quickly in most well systems in our area (personal experience). There's no real data on this stage at purewaterclub.com that would tell me how much resin is in the stage or what its capacity is. It looks small compared to a standard 10-inch x 2.5-inch cartridge that is typical. My guess is that it will exhaust more quickly. At this point, this stage will drive your operating cost for this system.

 

Pure water club sells an "alkaline water filter" stage for $35. It says that it "changes the acidic RO water into a perfect Natural Alkali Calcium lionized Water." My guess is that it's full of limestone chips (calcium-magnesium carbonate) to help neutralize the carbonic acid from the CO2 in the water. It might help if it was installed as a pre-filter to your setup, but I'm not sure exactly how much of a benefit it would provide.

 

Spectrapure provided some information on CO2 in well water and its effect on DI resin on this page.

[AlanM]

You mentioned earlier in the thread that you needed to rinse the membrane for 7 hours or something.  What did you mean by that?  I've never heard of a system that needed 7 hours of rinsing.

 

I've usually just run about 5 gallons through it and out the waste line to get the preservative out of the RO membrane and called it done after I put in a new membrane.

Edited February 24, 2017 by AlanM
change 9 to 7

[Jon Lazar]

That sort of settles it. Your DI resin is dumping ammonia. It's caught the occasional ammonium ion that was in the water and trapped it. Now that the DI resin is exhausted, it's dumping the ammonia. 

 

Wow, you learn something new every day.  Makes perfect sense in hindsight, but I never realized that would happen.

[WheresTheReef]

How much water do you make at a time? Reason I ask is that there is an initial spike in the TDS coming out of the RO that will go through the DI filter. In my case, the TDS rises quickly and spikes just over 100 TDS and then quickly drops to around 3 TDS. This happens over about the first minute or so. I recently added a flush line between the RO output and DI input that I open until the RO output drops to single digits. I then close this valve and open the valve on the DI output to start making water. By doing this I hope to extend the life of my DI resin. Making larger batches of water can help offset the initial TDS spike as well. I usually make at least 20g at a time.

[Origami]

How much water do you make at a time? Reason I ask is that there is an initial spike in the TDS coming out of the RO that will go through the DI filter. In my case, the TDS rises quickly and spikes just over 100 TDS and then quickly drops to around 3 TDS. This happens over about the first minute or so. I recently added a flush line between the RO output and DI input that I open until the RO output drops to single digits. I then close this valve and open the valve on the DI output to start making water. By doing this I hope to extend the life of my DI resin. Making larger batches of water can help offset the initial TDS spike as well. I usually make at least 20g at a time.

This works great for people that are on city water. The TDS burst is short and avoiding it can stretch resin life. However, for those of us who are on wells, we may have high dissolved CO2 in the water. This shows up as carbonic acid and passes through the RO membrane. Then, it sucks up all our anion resin in very short order. I used to get 3 or 4 months out of my DI resin while on city water. Today, I can only get about 100 gallons out of it (2 weeks?). It makes using a mixed bed resin very expensive.

[mari.harutunian]

You mentioned earlier in the thread that you needed to rinse the membrane for 7 hours or something. What did you mean by that? I've never heard of a system that needed 7 hours of rinsing.

 

I've usually just run about 5 gallons through it and out the waste line to get the preservative out of the RO membrane and called it done after I put in a new membrane.

It's a 100gpd system so it's 100g/24 hours and instructed me to rinse the ro filter for 30 gallons. It does about 4.2 gallons per hour so it would take about 7 hours to run 30 gallons of water through it. Why is it 30 gallons? It said something about a preservative(not sure)? I'll read it again when I get home.

 

 

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[mari.harutunian]

How much water do you make at a time? Reason I ask is that there is an initial spike in the TDS coming out of the RO that will go through the DI filter. In my case, the TDS rises quickly and spikes just over 100 TDS and then quickly drops to around 3 TDS. This happens over about the first minute or so. I recently added a flush line between the RO output and DI input that I open until the RO output drops to single digits. I then close this valve and open the valve on the DI output to start making water. By doing this I hope to extend the life of my DI resin. Making larger batches of water can help offset the initial TDS spike as well. I usually make at least 20g at a time.

Usually 5-10 gallons at a time. Not much.

 

 

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