Safe RO Water Storage

[MateoinLosAngeles]

Hey all,

I've been dealing with some rot issues for the past few days, they all happened in plants that were in S/H and that had a foul-fermented smell coming out of the pots. My plants in bark or sphagnum didn't have any distinctive foul smell. I decided to water the plants with chlorinated tap water, and the smell went away immediately. Three plants I've had to treat through other means.

Then, I saw in my fertilizer concentrate, which I make myself using the same RO water I use to water the plants, what seemed like white spores floating in the concentrate with mycelium-like filaments.

I probably will not go through the identification of these spores since it will probably be easier to make new fertilizer, but since this rot issue happened only on S/H plants, I started to wonder if I've been using contaminated water. This is also something of concern for me since I use the same RO water with my humidifiers.

The RO membrane should be able to remove most microorganisms. However, it might take really little to contaminate a batch over time, especially if one leaves the storage tanks open. I store my RO water in jugs. Or maybe there could've been a blip in the concentration of "water molds" on any given day. Maybe the RO membrane (4 months old) is in need of cleaning...

I don't like to use chlorinated water because I supplement it with live microbes. I use Quantum Total from Ray about twice a month, and I do a drench with Bacillus amyloliquefaciens and Bacillus subtilis concentrates from Arbico Organics about once a season.

So my question is... What do we know about safely storing and using RO water? This water is mostly chlorine free since the membrane is able to get rid of it, which does make it vulnerable to microorganisms.

Assuming this might've been an issue with Phytophthora, I could gather some information:

• - Some nurseries lower the pH of their irrigation water below 4, which has shown to be effective against Phytophthora. Most orchids should be able to take this. Not sure how Paphs, some terrestrials, or even Oncidiums would respond, though.
  
• - Another source mentions pH below 3 seems to kill Phytophthora completely.
  
• - Heat above 140ºF also kills Phytophtora.
  
• - Using bark might help, especially if it's been composted, since it favors the growth of antagonistic fungi like Trichoderma sp., however, it would mean giving up on the many benefits and conveniences of S/H.
  
• - Bacillus amyloliquefaciens, subtilis, licheniformis, megaterium have shown Phytophtora antagonisms, of which B. subtilis 30B-B6 has been singled out as the best.

So some speculative solutions:

• - Could lowering the pH of irrigation water help prevent the spread of Phytophthora? How would this affect calcareous-loving plants like Paphs, Terrestrials, or Oncidiums?
  
• - Could supplementing with beneficial microbes help? The issue here is how to guarantee that the microbes are alive, that the water pH is not too acidic, the concentration and frequency are right, and that the strains are the correct ones. I supplement with microbes, but whatever has caused the problem seemed to not respond to the specific strains that I use.
  
• - For a fertilizer concentrate or for water in a humidifier, could it help to acidify the water below 3 by adding a compound like citric acid? At a density of 1.66 g/cm3, a 5% solution would require adding about 114 g per gallon, but could it deposit or damage a humidifier?
  
• - Could using UV light help?
  
• - Could adding some other bacterial growth inhibitor to the stored water help? And if so, how to make sure that it is not damaging the beneficial bacteria colonizing the plant?

[Ray]

While I cannot be certain, I doubt the RO water is the source of pathogens. They’re more likely airborne and I suspect that the S/H pot is just a better environment for them than is the dryer bark.

[MateoinLosAngeles]

Originally Posted by Ray

While I cannot be certain, I doubt the RO water is the source of pathogens. They’re more likely airborne and I suspect that the S/H pot is just a better environment for them than is the dryer bark.

I wonder if I left the fertilizer concentrate open for too long, would you lower pH to <3 for preservation? It’s K-lite 13 tsp/gallon

[estación seca]

Foul smells are usually bacteria, not fungi. Are you throughly flushing at each watering? How often?

[MateoinLosAngeles]

Originally Posted by estación seca

Foul smells are usually bacteria, not fungi. Are you throughly flushing at each watering? How often?

I do, I would even say very thoroughly… I fill up the pot until it floods over for several seconds, then I do it again. I water 2-3 times a week, flush every fourth watering. Kelpak once/month, Quantum 1oz/gallon every 3 weeks and 2 oz/gallon every month or two. 50 ppm N/watering when I water 2x week, 25ppm N if I water 3x week.

Phytophthora has a documented smell and it’s neither a fungus or bacteria. It’s an oomycota.

[estación seca]

I would flush thoroughly with a solution of an acid with low pH, maybe 3. An organic acid like vinegar might be simplest. It would be unlikely to hurt the roots.

I water 2-3 times a week, flush every fourth watering.

I don't understand. With S/H each watering is a full flush. What do you mean by a watering?

[MateoinLosAngeles]

Originally Posted by estación seca

I don't understand. With S/H each watering is a full flush. What do you mean by a watering?

Sorry maybe a semantics thing here. I only call “flush” waterings in which I use flat RO water without any fertilizer (I might use these waterings for the Quantum supplementation). The rest of waterings I would say I “flood” the pot but not necessarily flush it since I do add some minerals into the pot.

So a normal monthly schedule would look like this for me:

(All waterings flooding the pot)
Week 1
1 - 50 ppm N + Kelpak + Quantum Total
2 - 50 ppm N

Week 2
3 - 50 ppm N
4 - “Flush” (flat RO, no fertilizer)

Week 3
5 - 50 ppm N
6 - 50 ppm N

Week 4
7 - 50 ppm N
8 - “Flush” (no fertilizer) + Quantum Total

Sometimes during hotter days/weeks I use a sprayer and heavily water the tops of the pots with a 5 ppm N solution just to keep them going in between the heavy waterings. But the sprayer isn’t strong enough to “flood” the pot, I use a watering can or a hose connected to a pump for that.

---------- Post added at 12:21 PM ---------- Previous post was at 12:04 PM ----------

Originally Posted by estación seca

I would flush thoroughly with a solution of an acid with low pH, maybe 3. An organic acid like vinegar might be simplest. It would be unlikely to hurt the roots.

I’m throwing away one of the plants, it was an overnight vulperization but for what I’ve read these water molds are very opportunistic and can stay dormant in a plant until the heat of summer hits. There’s a good article by Sue Bottom called “Summer rots” on the St Augustine OS website. The only issue I have with the StAOS recommendations is that they always bring up professional fungicides that cost hundreds of dollars and are diluted at “4 drops/gallon” which is a huge waste for a small collection. They are also not labeled for residential indoor use (I grow in an apartment, big apartment, but an apartment nevertheless). And most importantly, I hate using them and affecting the positive microorganisms in my plants.

For the affected plants I drenched the pot using Physan 1tbs/gallon. The three showing signs of illness I will be using a copper fungicide (studies show Copper affects these mold fungi but many Bacillus subtilis can withstand them) because at this point I need something systemic. And I will leave the plants isolated. If I have to pull the big guns I might get me the generic version of Subdue and figure out to spray on the street or something!

Second, for waterings I will start mixing tap with RO to have some chlorination in the water, and I will use Quantum exclusively on “flush” days since the bacteria is sensitive to chlorinated water pre-colonization. I will have to see how much tap I can use without hurting Cattleyas.

Third, for the fertilizer concentrate, I think I’m gonna lower the pH of the solution to <3 using citric acid. I’m still researching that. I will also start using 32 oz bottles instead of one gallon bottles for storage. I will also test the pH of the irrigation water after mixing with the concentrate, I think I can go down to 4-3.5 without harming the plants. This might help. Those in bark are in orchiata which “might’ resist the acidity better.

Fourth, for the storage of water I use good grade carboys that I stack in shelves. I have some extra UV LED “black” lights from my younger partying years and I wonder if the spectrum would work to eliminate potential growths in the stored water. Gotta research that.

Finally, I think I will get more thorough with growing area hygiene and ventilation. Might need to add a couple of fans and disinfect the tubes that come from the RO system before I place them in the jugs to fill up.

The plants that aren’t affected by this, I will double dose of Quantum and use weekly during the hot, humid Summer months, and see if that helps as a preventative. I will also explore doing biweekly more concentrated drenches of biofungicides using other strains. A product called “Mycostop” seems highly recommended.

---------- Post added at 12:22 PM ---------- Previous post was at 12:21 PM ----------

Btw, I know my responses above are long but I wanted to leave it written down in case someone reads this at a later date!

[Roberta]

I suspect the the chlorine in the water is in the form of chloramine (chlorine plus ammonia) rather than chlorine, not volatile. Chlorine tends to react with organics in the presence of sunlight, generating trihalomethanes so water suppliers, especially the larger ones, have gotten away from it. Have you tested the water for either free chlorine or chloramine? There are test strips for the purpose (from an aquarium supply store or Amazon) so that you know what you are, or aren't, dealing with in that department. (The carbon filter of my RO system is rated based on volume, and I wondered if I was saturating it which would trash the membrane... found that the chlorine level in either form in my tap water was barely at detection limit or even below, so I'm no longer concerned about taking out what wasn't there in the first place.)

[Roberta]

Just for grins, I checked my water today. Total chlorine was 0.5 ppm, free chlorine zero (below detection limit of the strip). So only a tiny amount, and that held, no doubt, as chloramine. If your tap water is anything like mine, it would not contribute much to a mix with RO as far as disinfecting qualities are concerned.

At any rate, test so that you know what you're working with.

[Dimples]

I’ll add that the chlorine/chloramine in the water is only intended as a backup for the prevention of microbial growth while the water is still in the pipes on the way to the users (and if I’m not mistaken it’s actually because of the unknown status of the pipes in our homes and buildings, not the municipal supply pipes, because the high flow rate/volume keeps the insides of those clean.). The chlorine isn’t at a concentration that will do anything noticeable in your situation.