RO system

[Lanmark]

Thanks Ray

And Diane, I also wonder if drinking all the crap found in our city water isn't in fact worse for us than losing out on the minerals by drinking the filtered RO water. Spinach, legumes, and nuts are all good sources of magnesium in our diets.

I don't know, Diane, if adding ProTekt would be useful or if it is even necessary.

 

[SlipperFan]

The package of MSU RO formula fertilizer I have which recommends mixing it at 125 PPM Nitrogen (3/4 tsp per gallon, using once per week) came from Porters. You probably made the label. oke:

It's true -- based on the information given to us from Greencare.

No one has ever told me the strength at which I should be mixing my MSU RO formula fertilizer for use on Neofinetia falcata, whether for once a month feeding, once a week, or daily. That is part of the reason I am asking these questions.

I don't know what constitutes "full strength" MSU Fertilizer so that I can dilute it to quarter strength or less for daily use.

The 125 ppm is based on MSU's research on orchids -- this would be considered to be "full strength." MSU had all kinds of orchids when they did their research, but I'm not sure that they had any Neos. However, I truly don't think it makes any difference. The fertilizer at that strength was meant to be used once a week. I don't think it hurts to skip a fertilizing now and then. But plants seem to do better with regular feeding.

I dilute it down to about a quarter-strength in the water I spray on my mounted plants every day or two. But then, I'm an experimenter, not a scientist.

 

[Lanmark]

I dilute it down to about a quarter-strength in the water I spray on my mounted plants every day or two.

That's what I generally do too. From time to time I give them higher concentrations, and they also get some blasts of pure water as well.
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***I want to say thank you again to cnycharles, Ray, etex, orcoholic and Slipperfan for the great replies to my recent vociferously wordy posts.***
Ya'll rock!
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Getting down to the business of RO water systems again...after we run our mineral-rich source water through the RO membrane, there usually remain a few PPM of dissolved solids. Some people might only have 2 or 4 PPM remaining, I generally have 8-13 PPM, and some people with really "hard" source water might end up with 30 or even 40 PPM still remaining in their water after it has gone through their RO system. You can get rid of these additional dissolved solids by employing one or more deionization cartridges at the tail end of your RO filtration system, but is it really necessary to do this when the water is to be used for orchids? The remaining few PPM of dissolved solids usually consist mostly of silicates, phosphates and nitrates. These things are bad news for delicate micro-ecosystems found in salt water aquariums, but they sure sound like plant food to me. What do you think?

 

[Ernie]

I just got my MSU Pure Water Special by Green Care and the label says 1 tsp per gallon, so I would assume this was full strength. Will use a little less for babies. Would adding Protekt still be useful?

Diane,

ProTeKt will increase your pH. We use it with DynaGro formulas which tend to lower pH in RO water. We get a high pH when adding MSU RO to RO water and need to decrease it. We use vinegar at about 1 Tbsp per 25 gallons to lower pH when using MSU RO.

pH is important for nutrient availability as previously stated. But we test pH when we mix up fertilizer AND the runoff from watering (very easy with s/h culture!). We are most concerned with what the ROOTS see not what the fertilizer solution pH is in the bucket.

Also, "pure" water changes pH readily since it has little/no buffering capacity. The pH of your RO water fresh out of the tap might be high, but after sitting out for a short time might lower. Ours comes out a ~8 and drops to ~5 after 12 hours or so.

Wow, this turned into a beefy thread. Good job all. :clap:

-Ernie

 

[SelectOrchids]

Yep, pure water will hydrate the cells around it more efficiently than "rich" water due to a "weaker" concentration gradient. As long as that doesn't cause the cells to burst (lyse), that's a good thing. Turgid cells are generally desirable. Not entirely sure, but would guess good nutrients in plant cells are moved about actively, not passively??? Possibly even sequestered and not just drifting around in the cytoplasm? So they would not be able to be flushed out by dilution, water would rush in to try to dilute the chemicals in the cells to equilibrium. Once again, we REALLY need a bonafide plant physiologist member here!

-Ernie

They are moved both actively and passively, that's the problem. The whole plant physiology is a wide field that required years of knowledge and experiment to start to understand a little bit. Even so, it is not always practical, and does not replace skill and practice.

One example, a bit related to the question.

If plants are supplied with nitrate, the nitrate will be reduced to nitrite, then to ammonia. Simple, right?

The key problem being that if you supply calcium at the same time, the reduction of the nitrate will be made in the roots, if you supply potassium, in the leaves, where the nitrate ion will be transported first... And if you do not have enough molybdenum - which can occur in the coconut products, as molybdenum is readily blocked by coconut, the nitrate will just travel to the leaves, be stored, and never used.

Now, the key problem is that quite a few ions cannot be used alone by the plant, and by using nitrate, you can push an excess of calcium and potassium inside the plant.

If you make a foliar analysis for total N, everything looks smooth and fine even with no molybdenum. Then you have to investigate both nitrate content of the leaves and the molybdenum level.

As for pure water, it will definitely do damage to the vacuoles and to the root tips first, by a simple osmotic process. It can 'blast' root tips easily.

Back to the RO system, I am writing for a while a paper on that. One thing you must pay attention, especially in Florida, is the boron content of your water. RO systems usually do not remove boron, as they are not a physical filter. I explained that already, but I think the priority when using RO water is to check the tap water analysis for boron, I just got a request from a grower who has a big mess with boron right now, as he though the RO would care of that as well...

 

[Ray]

Getting down to the business of RO water systems again...after we run our mineral-rich source water through the RO membrane, there usually remain a few PPM of dissolved solids. Some people might only have 2 or 4 PPM remaining, I generally have 8-13 PPM, and some people with really "hard" source water might end up with 30 or even 40 PPM still remaining in their water after it has gone through their RO system.

I don't agree with that at all - ignoring the variability and inaccuracy of TDS meters, if you're really getting above about 10 ppm in your "pure" water stream, your system is not doing it's job, that is, you need a new membrane.

Keep in mind how an RO membrane works, compared to other "purification" means:

Let's take a carbon filter to remove organics, for example. The water flows around a bunch of granules of activated carbon. If the organic molecule happens to pass into one of the zillions of tiny crevices in the carbon that were created in the activation (heating) process, it will be adsorbed and stay there, removing it from the water. If the molecule bypasses the first crevice, it still has a chance to be captured by another. Higher degrees of activition, larger filters, and lower incoming concentrations increase the probability that the molecules will be trapped, but don't guarantee it. So, if the incoming solution is higher in organics, all else being the same, one expects a higher level in the output.

An RO membrane, by contrast, is a mechanical barrier. The membrane is full of microscopic "holes" that are sized to allow water molecules to pass, but effectively block larger molecules. Having more or fewer larger molecules in the feed stream has no impact of the effectiveness of the membrane (but will affect its life).

The carbon filter is like an array of speed traps and the organics are speeders - most will get caught, but a few will slip through. The greater the number of speeders, the more will be lucky.

The RO membrane is like a very narrow doorway - no matter how many fatties there are in the group, none of them is going to get through, only the skinny people.

 

[Lanmark]

I don't agree with that at all - ignoring the variability and inaccuracy of TDS meters, if you're really getting above about 10 ppm in your "pure" water stream, your system is not doing it's job, that is, you need a new membrane.

I disagree.

My RO membrane is a GE Osmonics thin film composite membrane. Some RO membranes are cellulose acetate membranes. But that's not my point; I'm just stating the facts about my membrane.

My membrane is rated "Average NaCl Rejection: 98%" ...it doesn't say anything about 100%, and it definitely says the word "average" and not "absolute". Most RO membranes I have seen for sale in the market are advertised as removing "up to" anywhere from 93% to 98% of dissolved solids. Usually the higher gallons per day the filter is rated for, the lower the rejection rate it claims to have. I know there are super high efficient membranes which remove everything, but most of the RO membranes I've seen for sale aren't of that type.

If I were to add a second or third inline membrane module to my filtration system and some deionization chambers then I would expect 100% pure water, but I haven't, so I don't. My water pressure and temperature vary as do the TDS levels of my source water. If I have 400 PPM to start, a 98% reduction would leave me with 8 PPM. If I start with 100 PPM, a 98% reduction would leave me with 2 PPM.

As far as I know from the information I have read at various water treatment websites including GE who manufactured my membrane, source water pressure and temperature affect the efficiency of the membrane through mechanisms such as contractions and expansions of the film which cause slight fluctuations in the size of the microscopic pores. As the membrane is repeatedly used over time, such useage and simple aging also are both factors in the reduction of the efficiency of the membrane. When the membrane slows and/or the TDS levels begin to rise, the time has come to get a new one.

Personally I don't have a problem with my RO water containing 13 PPM TDS as it does today according to the cheap little TDS meter I have. Last night I had 8 PPM. It might be right or it might be wrong, but at least I know my meter is consistent. Distilled water invariably tests at 0 or 1 PPM, and RO water from just about every single grocery store in my area consistently reads at 18 PPM; so I'm still doing better than what I can get at my local store. It's doing its job. I refuse to purchase and lug jugs of distilled water, and a water distillation unit at home isn't what I want to be messing with. RO is easiest for me.

According to Sanderianum's post, some of those few remaining parts per million in my water might be boron too...maybe in the form of a borosilicate.

 

[SelectOrchids]

Actually, a RO is not quite a physical barrier.

It works as a physical barrier for some larger molecules, and as ion repellent for quite a lot of ions, including boron, using an electrostatic scheme, and rejection through the waste water. That's why some of the non-ionized salts and quite a few gas, including ammonia, will cross the RO membrane easily...

There are plenty of docs on internet about what a RO is, and about what it is not, and that's complicated to say the least. From my practical side, I got people who had a very strong RO water membrane, and they got some dozen of thousands of plants scrwed up by a boron toxicity. And the funny thing being that some boron compounds do not add anything to the TDS or EC readings, because they are not ionized...

One introduction to some problems of the RO systems can be found here:

http://www.membranes.com/docs/papers/04_ro_water_chemistry.pdf

 

[Ray]

It works as a physical barrier for some larger molecules, and as ion repellent for quite a lot of ions, including boron, using an electrostatic scheme, and rejection through the waste water. That's why some of the non-ionized salts and quite a few gas, including ammonia, will cross the RO membrane easily...

Quite correct - it's a combo thing, but back to my scientific disagreement with Lanmark for a moment (I love how we can do this here without the "Jane you ignorant ****" attitudes), yes, the membranes are sometimes rated as X% rejection of NaCl, but it is my understanding that such a specification is a statement of the tolerance in the "hole" size, i.e., X% of the holes are small enough to block the NaCl, and should not be construed to suggest that the membrane is only going to block X% of whatever is in the input stream.

It would be possible to produce a membrane that will reject 100% of the NaCl, but it's cost is prohibitive for the benefit, and as you noted, the output would likely be very low, unless the membranes were huge, of course.

I'll absolutely agree with you that RO water with apparent TDS levels in the teens is fine.

I have never heard of boron toxicity due to RO use, but i am pretty sure any in the water is not a borosilicate - Pyrex glassware is borosilicate, and is quite insoluble in water.

 

[Lanmark]

Quite correct - it's a combo thing, but back to my scientific disagreement with Lanmark for a moment (I love how we can do this here without the "Jane you ignorant ****" attitudes), yes, the membranes are sometimes rated as X% rejection of NaCl, but it is my understanding that such a specification is a statement of the tolerance in the "hole" size, i.e., X% of the holes are small enough to block the NaCl, and should not be construed to suggest that the membrane is only going to block X% of whatever is in the input stream.

Okay, perhaps that particular statement should not be construed to suggest that the membrane will only block X% of whatever is in the input stream, but when I read the the marketing materials and spec sheets for the various RO membrane units out there for sale, it seems to be very clearly implied by all of them that the higher the gpd rating given to the RO membrane, the lower the overall rejection rate will be. If I use a 150gpd RO membrane, my resultant purified water will in fact contain more TDS than if I were to use a 50gpd unit.

Hehehe...I'm seriously thinking now of adding one or more deionization cartridges after my RO membrane. I currently have two types of sediment filters, a carbon filter, and a KDF filter inline before my source water reaches the RO membrane. I carefully monitor each of these and replace as needed (probably more often than needed).

The pure water stream leaving my RO membrane is then post-processed by another carbon filter before entering my collection container. I'd love to have RO water which always reads 0 or 1 PPM on my TDS meter, but it's entirely possible there'd still be potentially damaging elements present in my purified water when the meter readings are that low.

I guess the bottom line for each of us would be how pure is pure enough? Each person would have to make that decision for themselves based upon what species of plant they grow or what type of aquarium they have or what application their end-product purified water is intended to be used for.

:rollhappy: @ Ray (I'm still choking back the laughter and tears about "Jane") Just think how boring our lives could be without the awesome collective volume of humor with which Saturday Night Live has enriched our lives!

 

[etex]

Yea,Saturday Night Live used to rock!! Good reference!!LOL

 

[Ray]

Lanmark:

OK. You have now added yourself to the list of people I'd like to spend an afternoon with over a bottle (or so....) of wine (or whatever).

Seems to me we should probably establish the SLS - Slippertalk Libation Society - with regular meetings. Can you imagine what that would be like?

Could we get an AOS affiliation?

 

[SlipperFan]

Lanmark:

OK. You have now added yourself to the list of people I'd like to spend an afternoon with over a bottle (or so....) of wine (or whatever).

Seems to me we should probably establish the SLS - Slippertalk Libation Society - with regular meetings. Can you imagine what that would be like?

Could we get an AOS affiliation?

Only if we use RO water. oke:

 

[SelectOrchids]

Based on my empirical experience with low TDS/EC below 100microsiemens approximately, if your area does not have chromium or boron, your water is fine for orchids, period, and no need to bother any further...

 

[Yoyo_Jo]

... Could we get an AOS affiliation?

oke: Did you mean an AA affiliation? :rollhappy:

This has been an entertaining and educational thread.

 

[Lanmark]

Lanmark:

OK. You have now added yourself to the list of people I'd like to spend an afternoon with over a bottle (or so....) of wine (or whatever).

Seems to me we should probably establish the SLS - Slippertalk Libation Society - with regular meetings. Can you imagine what that would be like?

Could we get an AOS affiliation?

Sounds awesome, Ray! :drool: Dot can drink RO water as she has suggested while the rest of us devise a way to quick-ferment vanilla orchid blossoms to create a wicked brew. Sanderianum can analyse it for microsiemens, etex will think of exciting things to add to it to make it more nutritious, and we can all party and dance to old tunes by Jane's Addiction :wink: while the moths make tarts of themselves in the moonlight. :rollhappy:

 

[Ernie]

Now we're getting somewhere!

-Ernie

 

[Lanmark]

Hehehe... Ernie likes to party!

 

[etex]

Sounds like a plan!!

 

[cnycharles]

Sounds awesome, Ray! :drool: Dot can drink RO water as she has suggested while the rest of us devise a way to quick-ferment vanilla orchid blossoms to create a wicked brew

what about fermented salep or something like that?