Aluminum Pan Corrosion and Sundews

schmiggle

Arachnoprince
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I have been keeping some drosera filiformis for a little over a year now, and I recently switched from watering them by using bowls filled with water to using large (9x13) aluminum pans (I can go much longer between waterings this way). Before I switched, I considered the possibility that the pans might corrode and poison the plants, but decided that, because I have never known them to corrode with liquidy food inside, it was unlikely that they would corrode with water inside.

However, I have been away for the past two weeks, and I came back to find the pans dry, but with an odd powder on the bottom. I gave that little thought--it could easily have been dust--so I refilled the water and gave it little thought. However, several hours later, I have realized that dust could have been corrosion.

To be clear, the plants are perfectly healthy- and happy-looking, and are producing new leaves and have lots of dew on the mature ones. However, I know a lot of metal poisoning is cumulative, so I would like to know sooner rather than later if there is a danger.
 

The Snark

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Congratulations. A simple straight forwards question and one of the largest can of worms I have encountered in many years all balled up into some powder in the bottom of an aluminium pan.

Is the powder from oxidization, sedimentation, precipitation, corrosion or chemical reaction / inclusion / contamination? Without it being chemically analyzed and identified we would have to take every one of those possible scenarios into account. Is the powder toxic or would it become toxic or break a toxicity threshold over time from accumulation? Unknown.

What bothers me, and would bother any metallurgist or toxicologist, is aluminium in commonly found commercial forms and grades does not exhibit such instability. It is either an unstable alloy or there is some factor, some chemical process, that has caused this.

So simplify in the extreme. Remove the aluminium and use a stable material such as a ceramic and use bottled drinking water.

Then create a test, trying to replicate the process that created the powder, away from plants and animals. Process of elimination. Was it the aluminium, the water, or contamination? Isolating the test from the environment will eliminate the latter. The water may be the culprit, containing chlorine or other, and the aluminium may be suspect.
Run the test and let us know if you can replicate the creating of the powder and we can go from there.
 

schmiggle

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It's definitely not the water. I've used distilled water for a very long time. I will, however, switch temporarily to something stable (probably not ceramic, I don't have it, but using cardboard bowls again for a little while is probably fine) and see what happens when both aluminum and the stable thing dry out. Thank you for the help! Glad I was able to give you such a hard time ;)
 

The Snark

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Found one possible reason for the powder. Failed clarification system in the water treatment. That is, water was being used faster than the sedimentation agent, commonly alum, was able to precipitate. You end up with a mineral soup.
It turns out this is very common with bottled waters sold and quite a few water treatment plants. The demand for delivery comes first while the precipitation takes a period of time. As long as the water passes the no growth, bacteria free tests, it is acceptable, if gnarly. What you saw in the bottom of the pan is typical of a sedimentation agent finishing it's job.

Next is was the water actually fully distilled. Distilled pure water costs a fortune. There are several 'distillation' processes that replicate steam distillation yet let contaminants through. Or was the water simply treated, which could mean just about anything.
 
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schmiggle

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First of all, I switched back to cardboard, which had never caused my any problems. I don't think I'll be using aluminum pans again.

Snark, are you saying that a sedimentation agent is put in the water in the treatment plant, but not allowed to finish precipitating? That would be really problematic, but I would have expected to see precipitants in cardboard or plastic bowls as well. Luckily, I didn't find any. Is there still the possibility that that's the issue? I admit that I don't always use the same water brand, I just make sure to buy water without added minerals and that isn't tap water. However, the truth is I've probably never used water which was actually distilled. I don't generally buy "purified" water, but I do sometimes buy even that. I just haven't had any problems, and I know it doesn't have that many chemicals in solution, so I've figured it's fine.

I don't know if there's any sure thing to do other than use rain water (which is luckily not polluted in my area). It's just a pain to remember to collect and store.
 

The Snark

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Unfortunately, bottled water is often pretty filthy. Loads of info all over the net about that. Flocculants not given sufficient time to do their job is common, filters not changed often enough and blowing past the pressure checks and so on. Look at those Olympic pools. It's all about $$$. When a system goes bad it is pretty rare a bottling plant will shut down the entire operation for several days while everything gets chemically scrubbed clean. They have certain remedial measures but those can easily screw up as well. When you are talking about millions of bottles of water processed every day by thousands of bottlers, quality control often goes out the window.

My guess is the aluminum acted as an agent, either causing or contributing to mineral compounds to form. Unlike most plastics and the treated paper, the metal can get involved chemically, electrically or biologically.

PS Got to love the BS at those Olympic pools. 120,000 liters of HyPer MIGHT have got into the water. Oh? They happen to have so much of that stuff sloshing around it gets randomly dumped here and there? And of course, any idiot with any grade license in water treatment knows you can't add HyPer to chlorinated water since they defeat each other and the organics sail through untreated.
 
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schmiggle

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Got to love the BS at those Olympic pools. 120,000 liters of HyPer MIGHT have got into the water. Oh? They happen to have so much of that stuff sloshing around it gets randomly dumped here and there? And of course, any idiot with any grade license in water treatment knows you can't add HyPer to chlorinated water since they defeat each other and the organics sail through untreated.
(Enter two corrupt Brazilian politicians backed by the Hy-Per Lube corporation--let's call them David and Raisa)
David: As planned, I successfully used public funds intended to build safe stadiums to buy 30,000 gallons of Hy-Per Lubricant!
Raisa: WOOT! (high five)
David:...However, I have nowhere to put it. I can't just leave barrels and barrels of the stuff lying around.
Raisa: Why don't we just dump it all in the swimming pool? There's no way anyone will notice that there's a massive load of chemicals in the pools, and even if they do, we'll just bribe them with more public funds to say that there aren't. Plus, we can't be implicated even if they do find out!
David: Great idea! (Dumps 583 barrels of lube in olympic swimming pool)

PS It's a bit of a long story how I got it, but I know have a reverse-osmosis filter that was good enough to grow orchids, which I think makes it good enough for carnivorous plants. Plus the tap water here is pretty good to start with. I think I'm finally in the clear...
 

The Snark

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SNERK Not implausible enough. Expect to get sued. :arghh:

What I can't figure out is who the morons were that had their mitts on that quantity of H2O2 yet were completely clueless about the redox reaction, the industry standard method for removing chlorine from water using H2O2. So they dump the H2O2 in and all the chlorine goes poof, literally. Within a few minutes the H2O2 goes poof as well and what you have is organic material laden raw water without any growth inhibitors.

Or to simplify, they removed anything that could kill or inhibit the growth of bacteria, algae, molds, fungi and spores and did nothing that would clarify the water. IE, grab shotgun, aim at ant on foot, fire!

(Hydrogen peroxide -H dioxide is non residual. It comes in contact with air, light, a number of chemicals or any organic material and it turns into ordinary water. Great for sterilizing but useless as a growth inhibitor which is why chlorine is used instead.)
 
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schmiggle

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The Snark

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That is a standard triple stage with RO and the bypass. You will want to take them all apart, find the identity of the manufacturer and get replacement filters along with specs and info. Then clean all thoroughly. Seems to be missing the dispenser tank. Ask the people selling the filters about that. That system does not have a UV sterilizer or water polisher so it is sort of borderline for drinking water. Both can be added after the final stage if you want.
If you don't need uninterrupted service you can always use the bypass as a pre filter-sediment trap. Helps keep the filters from clogging up with high mineral content water.
 
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schmiggle

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I'm only using this filter for plants, so the UV shouldn't be a big deal, but the polisher could be.

Just to repeat what you're saying about the rest to make sure I understand: Take apart the entire system. Inside, the filters (the brown foam things in the tube) will have the name of a manufacturer on them. Buy replacement filters from that manufacturer. Ask that manufacturer about the dispenser tank. (Is this the dispenser that you use to put water in the system, take water out of the system, or both?) If they don't have filters or a dispenser for this model, should I just not use this filter?

Can I use the bypass to skip the sediment filtration? The issue with the drinking water near me for my plants is a combination of added chlorine and already existent--but fairly low--concentrations of other ions. I don't know how much point there is in skipping one filter, though...I could also maybe skip the fine membrane filtration, since its mostly good for getting rid of stomach bugs anyway, but again not sure there's much point.

Where does the water pressure come from to push the water through the system? Do I have to attach the filter to the pipes that feed water to the sink? This I'm really loath to do--I'd be willing to give taking the filter apart and putting it back together a try, but given that it's not my sink, and that I'm a very technically challenged person :) I don't want to complicate things too much. I'd like to get better at being able to do these sorts of things myself, but I think small steps are the way to go, and it sounds like taking apart the filter and putting it back together is actually pretty easy.

Thank you so much for the help! I don't want to be irritating because of my almost complete lack of knowledge (just looked up all the terminology :p). Hope these questions aren't too dumb.
 

The Snark

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Whoa. K.I.S. rule, okey dokey? Just for plants, you don't need the RO, the tube thing on top. Even a single cartridge filter will do. The triple stage set up you have is a whole house, the WH designation found on many filters, all particulates, solids, sediments and many contaminants. The only things they cannot remove are dissolved contaminants and toxins. That's the ROs job. But plants don't care about most of that unless the water contains chemicals with herbicidal properties.

Okay, allow me to dumb things down. No insult whatever intended.

-Filters are in stages, each stage feeding the next. They remove large, small, and smaller yet particles. Cram the raw water into a fine stage filter it plugs up very fast.
-All filtration systems have a minimum and maximum pressure range. Water must be under some pressure to get through the filters. Check with the manufacturer for the required pressure range. With typical residential water delivery systems this range is between ~7 PSI up to ~45 PSI.
-When you shut down the system to clean it and change the filters some systems have a bypass filter, a jack-of-all-trades filter to keep water supplied temporarily while the main system is down.
-Another use of a bypass filter is when the water flow exceeds the capability of the filter stages. Usually an alarm goes off when this happens, if so equipped: Hey, too much water demand! Going to have to bypass the main filters. Better check your system!

So it's just clean, cleaner, cleanest in filter stages.

The Reverse Osmosis is a membrane filter capable of removing dissolved contaminants. It delivers very high purity water. However, it is very slow, thus having it run constantly and a storage tank is pretty much mandatory. It also wastes off some water as the membrane has to have water flowing constantly over it. This water has to go down the drain or you need a recovery system. You cannot send the waste off water back into the filters since there is no pressure differential and no water would flow over the RO membrane.
Your system has the RO membrane but no storage tank. So you would only get a tiny trickle, an ounce or two a minute. Where the storage tank went is ??? Buy a new one when you get the filters if you want to use the RO. You change the membrane usually when you change the filters. The outlet, cleaned water to the house, comes out of that storage tank.

Some systems have multiple flows. The water goes through the filters then is sent to the toilets, shower, dog washing station, whatever, and to the RO. The RO does additional cleaning which is your drinking water. If you want ultra clean odor free water you can add a UV bacteria killer and water polisher after the RO stage.

Hope this helps.

PS The filters, the entire system, is designed to be taken apart with ease. Many manufacturers even supply a special wrench to make opening the filter containers easy. For example, the system you pictured, I could completely disassemble with just my hands in less than a minute.
 
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schmiggle

Arachnoprince
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At least it's not the KISS rule. :) But this is super helpful! Thank you very much. I'll ask the person it came from to see if she has the dispenser tank lying around somewhere.

Once I have a tank, I just hook it up, fill it with water, and wait a while, right? Where does the extra RO water go? (I promise these are my last questions...)
 

The Snark

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Once I have a tank, I just hook it up, fill it with water, and wait a while, right? Where does the extra RO water go?
Down the drain. Pours into the sink on countertop units or you hook some fitting under the sink so it squirts into the drain pipe. Companies that sell these systems usually sell the drain fittings as well.
 

Daniel Wilson

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If you haven't already, i recommend putting a small gate valve on the drain line. I have mine running at just enough to keep the tds meter reading 0. The valve also reduces waste water by a lot. Mines running 7/1 filtered/waste. As well, if pressure in the membrane housing is too low the auto shut-off valve wont shut off completely. Mineral content in drain water is only a few percent higher than its feed water and can be used to water normal landscape plants. The 21"commercial membrane housing i have is a LOT more efficient than the standard 100gpd membrane i started with. I was, however, forced by hundreds of Sarracenia and a highland greenhouse to up my game.
 

The Snark

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If you haven't already, i recommend putting a small gate valve on the drain line. I have mine running at just enough to keep the tds meter reading 0. The valve also reduces waste water by a lot. Mines running 7/1 filtered/waste. As well, if pressure in the membrane housing is too low the auto shut-off valve wont shut off completely. Mineral content in drain water is only a few percent higher than its feed water and can be used to water normal landscape plants. The 21"commercial membrane housing i have is a LOT more efficient than the standard 100gpd membrane i started with. I was, however, forced by hundreds of Sarracenia and a highland greenhouse to up my game.
EXCELLENT INFO!

It's been a long time since I worked with RO and was thus unable to recall and mention those specifics. I do recall some of the miniature RO units aren't worth the powder to blow them to hell. They work but are fantastically inefficient. Very good idea to dial the waste down, even metering it to the average output desired if possible.

Trickiest system I've ever seen. Water delivered 120 feet up a hill by a water ram from an artesian well. Entered the household system into a pressurized holding tank with captive air that buffered the ram force. Went through a filter system, RO and a UV. RO waste water was recovered into a series of sedimentation galleries then reintroduced into the system by a small high pressure solar powered pump which also supplied a drip irrigation system for the garden. Zero energy use, delivered ~50-100 gallons per day. When they installed composting toilets they were able to supply the neighbor with drinking water from surplus production.
 
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