RO/DI with Phosphates but 0 TDS

[Arkayology]

I am getting around .05ppm P04 in my RO/DI as it comes out of the line but has 0 TDS. I am using a BRS 75gpd 5 stage RO/DI. The unit is 2 years old and I replaced the DI resin yesterday, but the carbon blocks are 2 years old and so is the RO membrane. I should say that I had this in storage (with water in it) but about 5 months after using it for 8 months. Tests were done with a hanna phosphorus meter and converted to phosphate. Tank is reading .015ppm as of today if that matters.

 

I know I need to replace the sediment filters/carbon blocks anyways, but should I replace the RO membrane as well? How do I know when it is ready to replace? I have read that the sediment filters do not have any bearing on P04, so is this a sign that I need to replace the RO membrane? I have also read that you cannot accurately read P04 with a hobbyist test kit, so if I am getting 0 TDS should I not worry about it? (AZDesertRat?)

 

Thanks for any advice.

[amored]

what are you storing it in? i know sometimes plastics can leech PO4 into the water.

[Arkayology]

I am storing it in a plastic potable water container. However, the .05ppm P04 reading I got was from the water coming directly out of the line, not from a storage container water (though I did test the same water from another storage container, a HD orange bucket, and got almost the same reading).

[Islandoftiki]

Are you certain your phosphate tests are accurate?

 

After two years, I would imagine all of your filters are done. I have the one that measures total number of gallons through the unit and I was surprised how quickly I used up the filters with making about 10 gallons a week. Ok, I'll admit, I left the unit on over night once by accident. That knocked a HUGE chunk out of the life of the filter. I got a little over 6 months out of a set of filters. I could have probably gone longer because we have such low TDS in our water, but just to be safe, I changed them. I was also just starting to lose pressure, so I know they were getting a bit clogged.

 

Here's a good explanation of when to replace your RO membrane: http://www.reefcentral.com/forums/showthread.php?t=1735411

[Arkayology]

Are you certain your phosphate tests are accurate?

 

After two years, I would imagine all of your filters are done. I have the one that measures total number of gallons through the unit and I was surprised how quickly I used up the filters with making about 10 gallons a week. Ok, I'll admit, I left the unit on over night once by accident. That knocked a HUGE chunk out of the life of the filter. I got a little over 6 months out of a set of filters. I could have probably gone longer because we have such low TDS in our water, but just to be safe, I changed them. I was also just starting to lose pressure, so I know they were getting a bit clogged.

 

Here's a good explanation of when to replace your RO membrane: http://www.reefcentral.com/forums/showthread.php?t=1735411

Thanks. Ya, I know the sediment and carbon filters need to be replaced, but I had read that the RO membrane lasts longer. I will read through the link you provided.

[Islandoftiki]

They absolutely do last longer. Many times longer. The good news is that you can test them to see if they're up to snuff, so you can know for sure when they need to be replaced.

[ReviloM]

If you got the funds to replace it, then do it. It's probably time to do that anyway. There also may be some dirt or matter on the end where the clean water comes out or the container you have may have sediment in the bottom. To me that's a small amount to even worry about. If you run something to rid phosphates in your tank then it will gone in no time. Don't stress it.

[Arkayology]

If you got the funds to replace it, then do it. It's probably time to do that anyway. There also may be some dirt or matter on the end where the clean water comes out or the container you have may have sediment in the bottom. To me that's a small amount to even worry about. If you run something to rid phosphates in your tank then it will gone in no time. Don't stress it.

I run zeovit so there is some aggressive phosphate removal going on. I was thinking about dropping a chem bag with some GFO in it to help remove any phosphates that might be in the RO/DI reservoir. Anyone see a problem with this?

[jbb]

Im not sure that the Hanna meters will be good at testing the ultra pure water that comes from a RO/DI unit.

 

 

The Rat will be a bigger help than I , but I'm pretty sure I am correct .

[ReviloM]

I run zeovit so there is some aggressive phosphate removal going on. I was thinking about dropping a chem bag with some GFO in it to help remove any phosphates that might be in the RO/DI reservoir. Anyone see a problem with this?

Nah dont do it. Just save that. Since you are running zeovit, That definitely is not needed.

[seabass]

If its testing 0 TDS, then it's probably alright. A good TDS meter is typically your best test for RO/DI water.

I think it's common to get a positive reading from Hanna Phosphate Checkers when testing RO/DI water (with either new or older filters). I can't say that I totally understand why. I get why it is difficult to test pure water's pH, but I don't see how tests, which are designed to test ppb (or ppm), are swayed by lack of TDS. Anyway, you might try testing some newly mixed saltwater, versus the RO/DI water itself.

[Horerczy]

Culprits could be the reagent being off chemically or hiding in the little packet. Doesn't take much to mess with the machine's mind (or lack thereof).

[seabass]

Inconsistencies can be caused by fingerprints on the tubes, air bubbles in the samples, spilled reagent, etc. However, testing pure water appears to consistently yield positive results. It seems like the reagent could have more influence in pure water.

[GHill762]

If its testing 0 TDS, then it shouldn't contain phosphate. That's your best test for RO/DI water.

 

I think it's common to get a positive reading from Hanna Phosphate Checkers when testing RO/DI water (with either new or older filters). I can't say that I totally understand why. I get why it is difficult to test pure water's pH, but I don't see how tests that are designed to test ppb (or ppm) are swayed by lack of TDS. Anyway, you might try testing some newly mixed saltwater, versus the RO/DI water itself.

I'm no RO/DI expert (where's AZdesertrat?), but from what I understand, you can have phosphates and 0.00 TDS water. Supposedly the phos won't show up as a dissolved solid..

[seabass]

I'm no RO/DI expert (where's AZdesertrat?), but from what I understand, you can have phosphates and 0.00 TDS water. Supposedly the phos won't show up as a dissolved solid..

 

Here's his answer on a similar post:

0 TDS does not necessarily mean 0 phosphates. Phosphates like silicates and forms of ammonia are weakly ionized and may not register on a hobbyist grade TDS meter, it would require a conductivity or resistivity meter to get to that level for sure.

That being said, if you are getting a reading of 0 TDS I would say its safe to assume the phosphate levels are low enough to not be a concern in the RO/DI water.

 

My thought is that there is some phosphate in the filtered water, and this is what the Hanna Checker is reading. However, the reagent might be having a more pronounced reaction to this small amount of phosphate (being basically pure RO/DI water).

[AZDesertRat]

Seriously, you are talking about 50 parts per BILLION. Lets put that in perspective.

 

Some real-world part per billion

comparisons

1 penny in 10 million dollars

1 second in 32 years

1 foot of a trip to the moon

1 blade of grass on a football field

1 drop of water in an Olympic-size swimming pool

 

The level you are suspecting is less than miniscule, its almost nothing. I seriously question the accuracy and the repeatability of the test kits and hobbyist instruments and their reagents. We as hobbyists are asking a $25 test kit or $50 pocket meter to give us the results of a $100,000 lab grade instrument which has EPA certifications and is operated by highly trained chemists and lab personnel using extremely accurate digital titrators and lab grade glassware. Its just not going to happen!

 

Use the checkers and test kits as tools in your arsenal, better than a litmus paper test but bowhere near a lab instrument, take them for what they are and do what you can to improve your initial water quality and to remove or lower what is in your reef system with many of the techniques discussed on all the reef forums. I know I'm not going to get worked up over 50 parts per billion myself, there is probably more than that in the air we breathe.

 

Spectrapure did a little blurb on one of their Sponsors Forums that I think sums it up pretty good, its probably not your RO/DI:

 

http://www.reefcentral.com/forums/showthread.php?t=2318622

 

If your membrane is good and your resin is the proper blend and is fresh you have done all you can.

[seabass]

Seriously, you are talking about 50 parts per BILLION.

I get that, but it's commonly agreed that that the recommended phosphate level is 30ppb (0.03ppm) or less:

• http://www.marinedepot.com/reef-tank-parameters.html
• http://www.melevsreef.com/parms.html
• http://www.reefkeeping.com/issues/2004-05/rhf/index.php

It's difficult to ignore when your source water is higher in phosphate than what is recommended for your reef tank.

 

Use the checkers and test kits as tools in your arsenal, better than a litmus paper test but bowhere near a lab instrument, take them for what they are and do what you can to improve your initial water quality and to remove or lower what is in your reef system with many of the techniques discussed on all the reef forums.

I agree. At such low levels, it's hard to get an accurate reading from hobby test kits. My Checker readings tend to jump around a bit. I've grown to accept the fluctuations and watch the trends/averages instead.

[Arkayology]

Thank you for the responses everyone. I try to be as meticulous as possible with my phosphorus meter and do not actually touch the vial with my hands, I make sure the packet is completely emptied, and a whole suit of other things to make sure I can get the best result possible. I try and shoot for around .02-.04ppm P04, so a reading of .05ppm is high. I try not to read into the tests too much, but look at how my coral is doing as the best indicator.

 

It seems that there is a consensus that reading RODI coming directly out of the unit is not completely accurate. I will test a newly mixed batch of SW when I do a water change this weekend to give myself a better understanding of what I am putting in my tank. I will probably replace theRO membrane in 6 months, but replace the other filters soon.

[AZDesertRat]

You also need to look at the level of accuracy and capabilities of the meter.

+/- .04ppm and +/- 4% of the reading. You are expecting accurate results that are lower than the sensitivity or accuracy of the meter.

[Arkayology]

You also need to look at the level of accuracy and capabilities of the meter.

+/- .04ppm and +/- 4% of the reading. You are expecting accurate results that are lower than the sensitivity or accuracy of the meter.

Ya, nothing is perfect. I mainly use it to tell me when things are really bad lol. Even within the .04+/-ppm I am still putting at least .01ppm into my tank that I don't need to be putting in. It could also be higher. My OP was more about knowing when to replace the filters than test kit problems. If a 0 TDS reading is fine then I will not worry about it. I appreciate you responding.

[seabass]

Even within the .04+/-ppm I am still putting at least .01ppm into my tank that I don't need to be putting in.

Or as much as 0.09ppm (depending on which extreme you are considering). I have actually gotten larger fluctuations than +/- 0.04ppm during consecutive tests before.

 

However, it does raise the question whether or not additional phosphate reduction would be beneficial. IDK, maybe like a canister of Phosguard in between the RO and DI stages. I doubt that it's needed, but it makes one wonder if our source water isn't at least a contributing factor to some of our phosphate issues.

[Arkayology]

Or as much as 0.09ppm (depending on which extreme you are considering). I have actually gotten larger fluctuations than +/- 0.04ppm during consecutive tests before.

 

However, it does raise the question whether or not additional phosphate reduction would be beneficial. IDK, maybe like a canister of Phosguard in between the RO and DI stages. I doubt that it's needed, but it makes one wonder if our source water isn't at least a contributing factor to some of our phosphate issues.

I had thought about this and was wondering if putting a chem bag in my RODI bucket would be a good way to remove any present phosphates? I can't think of any reasons what this would not be ok?

[markalot]

I get that, but it's commonly agreed that that the recommended phosphate level is 30ppb (0.03ppm) or less:

• http://www.marinedepot.com/reef-tank-parameters.html
• http://www.melevsreef.com/parms.html
• http://www.reefkeeping.com/issues/2004-05/rhf/index.php

It's difficult to ignore when your source water is higher in phosphate than what is recommended for your reef tank.

 

I agree. At such low levels, it's hard to get an accurate reading from hobby test kits. My Checker readings tend to jump around a bit. I've grown to accept the fluctuations and watch the trends/averages instead.

 

I think this simply points out how much unreasonable unscientific information there is in this hobby. You can't rationalize worrying about levels that low using hobby grade kits, and having three publications mention an acceptable level is, unfortunately. meaningless. Typically these are just echos of one another.

[seabass]

I had thought about this and was wondering if putting a chem bag in my RODI bucket would be a good way to remove any present phosphates? I can't think of any reasons what this would not be ok?

You'd probably want some way to circulate water through it (like a reactor). However, really I don't think that will be needed. New DI resin might be all that you need. Test some freshly mixed saltwater and see what you get.

 

I think this simply points out how much unreasonable unscientific information there is in this hobby.

We work off of what is available to us (information and hardware) on a hobbyist's available time and budget. I'm not aware of a scientific report that contradicts these guidelines. I'm confused, are you questioning the 0.03ppm recommendation? I know that some people prefer to use algae growth as a measure to determine high phosphate levels. I assumed that this particular guideline is based upon limiting algae growth. Although I agree, our kits aren't precise enough to worry about differences of 0.01ppm.

[markalot]

We work off of what is available to us (information and hardware) on a hobbyist's available time and budget. I'm not aware of a scientific report that contradicts these guidelines. I'm confused, are you questioning the 0.03ppm recommendation? I know that some prefer to use algae growth as a measure to determine high phosphate levels. I assumed that this particular guideline is based upon limiting algae growth. Although I agree, our kits aren't precise enough to worry about differences of 0.01ppm.

 

 

I can't question the level, nor do I care to question Randy Holmes-Farley's excellent analysis in multiple publications, but in all of that there is only a single reference to a single study that showed raising phosphates on a reef patch inhibited coral growth by 43%.

 

edit, sorry, 2 studies.

 

http://www.advancedaquarist.com/2002/4/chemistry

 

This inhibition of calcification takes place at concentrations frequently attained in reef tanks, and may begin at levels below those detectable by hobby test kits. For example, one research group found that long term enrichment of phosphate (2 mm; 0.19 ppm; maintained for 3 hours per day) on a natural patch reef on the Great Barrier Reef inhibited overall coral calcification by 43%.23 A second team found effects in several Acropora species at similar concentrations.24

 

23. Effects of elevated nitrogen and phosphorus on coral reef growth. Kinsey, Donald W.; Davies, Peter J. Limnol. Oceanogr. (1979), 24(5), 935-40.

24. ENCORE: the effect of nutrient enrichment on coral reefs. Synthesis of results and conclusions Dennison, W.; Erdmann, M.; Harrison, P.; Hoegh-Guldberg, O.; Hutchings, P.; Jones, G. B.; Larkum, A. W. D.; O'Neil, J.; Steven, A.; Tentori, E.; Ward, S.; Williamson, J.; Yellowlees, D. Marine Pollution Bulletin (2001), 42(2), 91-120.

 

What I do question is the rationality of testing very low levels of phosphates. If you have algae odds are you won't get an accurate reading anyway, and if you don't you certainly would not let things go until you did. The only rational testing, IMO, would be to find a floor for the test and look for a change in the phosphates so you have an idea when to replace media or take other action.

 

.03 is in the noise floor of most hobby kits and frankly I'm still now sure exactly how it was chosen, but then I wouldn't be smart enough to understand if someone told me.

 

http://www.advancedaquarist.com/2012/3/chemistry

 

Foods are by far the most important source of phosphate in most aquariums. In considering whether sources of phosphate other than foods are important, one must carefully look to the actual amounts involved to determine whether other sources are even worth trying to minimize.

 

^^ another good article.