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Old 14-07-2010, 10:41   #1
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RO Water Quality and Bacteria

Not sure how to proceed with this so any recommendations would be greatly appreciated...
In May, I got the watermaker running again after a long storage period.
I am quite pleased with getting 160ppm of TDS and product flow of about 42GPH. I have two SW302540 membranes in serial.

After about of week of drinking the water I felt some cramping. Stool was normal but more freequent. So I decided to test the water. Bacteria test kit from Home Depot came up positive so I took the watermaker product water for bacteria test to Health Labs in Providence RI. Got back
negative on fecol coliform, positive on total coliform and about 3 phone calls as to the source of the contaminated water.

I called them back and had a lengthy discussion with the head of the labs. It seems to me that bacteria can get into the system in so many different ways that Its pointless to test. He said that my system is too complicated and he's not qulaified to make recommendations on how to go about disinfecting it.
He wanted me to redo testing and take the sample from the galley fawcet, and not directly from the product side of the membrane.
Thinking about cleaning the membranes with organic(i guess alkaline) cleaner before doing any more tests.

Pretty cool, diagram on filtration.
Water quality- different water filtration methods- Reverse Osmosis/ Distillation/ Ion Exchange/ Carbon
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Old 14-07-2010, 13:02   #2
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I add about 1/2 mililiter of Clorox per galon of water to get around 5 ppm of free available chlorine. But the first thing I would do in your case is to shock the tank(s) with a cup of Clorox, filling the tank and rinsing at least once. I got a chlorine pool kit to make sure I have 1-5 ppm of chlorine.

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Old 14-07-2010, 13:23   #3
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Keep chlorine away from R/O membranes!

See ➥ Protecting RO Membranes from Chlorine Damage
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Old 14-07-2010, 17:44   #4
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cure for bacteria in water

#1 empty tanks down to about 1/10th vol. then add enough chlorine for a full tank(shock treatment)-run this stuff through all your pipes and let sit over night.
#2 then fill tanks with water flush out heavy chlorine from pipes.
#3 install seagull filter for potable water removes almost everything including chlorine
#4 add small dose of chlorine to new water as routine
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Old 14-07-2010, 18:14   #5
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Chlorine can do significant damage to membranes especially if the RO uses fresh water for the weekly flush. In that case, you're going to need filters to remove the chlorine before hitting the membranes.

It sounds like the water tank is contaminated, so I'd follow eyschulmans' recommendations. And I'd test the water in the tank or at the tap for a while just to make sure. There have been instances where a repeat chlorine shock was needed to get a particularly resistant bug out of the tanks and pipes.

I'd also make sure to change the potable water filters regularly as well. If allowed to sit, they can be breeding grounds for bacteria.
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Old 14-07-2010, 19:02   #6
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The tanks are contaminated. Yes the water being made by your watermaker is fine. A salt molecule is very small , bacteria are very large. Therefore the bacteria are being filtered out by the watermaker. Yes ultra vilolet lights (used in some systems) will kill the bugs , but they are more for contaminated tanks and well water . We have found if we start out with clean equipment and never add water to our tanks from an outside source, the HRO water stays good .
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Old 15-07-2010, 06:46   #7
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Ok, thanks I can clean with bleach. But the water sample I brought to the labs was before the tanks, at the product side of the first membrane. That came back positive for total coliform and negative for fecal coliform.
So I need to address the source of that contamination, thats why i was thinking about cleaning the membranes with alkaline cleaner.
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Old 15-07-2010, 08:29   #8
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Quote:
Originally Posted by phorvati View Post
Ok, thanks I can clean with bleach. But the water sample I brought to the labs was before the tanks, at the product side of the first membrane. That came back positive for total coliform and negative for fecal coliform.
So I need to address the source of that contamination, thats why i was thinking about cleaning the membranes with alkaline cleaner.

An interesting problem. While the alkaline cleaner will definitely clean the saltwater side of the membrane, I'm not sure it will clean the freshwater side. You should contact the manufacturer and ask their advice. Don't use Chlorine on your membrane under any circumstances, it will destroy it. My concern would be decontaminating the line from the membrane to the tank.

I flush my entire system with Chlorine once or twice a year. I basically add a half gallon of unscented bleach to my 110 gallon tank and fill it. I run all faucets until I get a strong chlorine smell. I then refill the tank until it starts to overflow and then let it sit for 4 to 6 hours. I then drain the tank through the faucets and refill it at least twice. On top of that I use a seagull filter for all drinking/vegetable washing etc.

Good luck.
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Old 15-07-2010, 15:54   #9
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Membranes can be damaged by to much cleaning. Your owners manuel will tell you to clean only when production drops (gals / hr ) or your ppm is over 500 and won't come down. It's not the membranes.
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Old 16-07-2010, 10:03   #10
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Ok that makes sense to not clean them often. They were never cleaned. I installed them new in Jan. 2007.
I found some literature on Dow Filmtec website that says .2% hydrogen peroxide can be used for sanitizing.
I'm gonna give that a shot. But i will clean the brine side first.
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Old 16-07-2010, 10:09   #11
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Where are you running the water maker in fairly clean open ocean water or in a harbor, marina or other area with possibly high pathogen count?
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Old 16-07-2010, 11:18   #12
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It is important to only run your watermaker in clean, open water, but this is not for the bacteria issue so much. However, my question is When did you last pickle your membrane? The pickling solution is pretty 'strong' stuff and would most likely clear the downstream side of the water maker once you begin to re-use the watermaker. I'd be a bit suspicious if the pickling hasn't been done for a long time.

As a side note, my manufacturer has now begun to recommend using polypropylene glycol as a pickling agent as being cheaper, nicer on the membrane and easier to do then mixing up caustic chemicals.

Anyone else privy to these details?
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Old 16-07-2010, 16:15   #13
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Had a contamination issue with rust colored dissolved solids. Drained, bleached, drained, still had it. Finally found that the source was a pressure accumulator tank way back in the system. No decontamination of the tank system would reach this far back. Tossed the accumulator and replaced with a pump that does not need one. Moral of the story is that there are some nooks and crannies in any system that make it tough to get a full decontamination.
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Old 16-07-2010, 17:27   #14
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Quote:
Originally Posted by cchesley View Post

As a side note, my manufacturer has now begun to recommend using polypropylene glycol as a pickling agent as being cheaper, nicer on the membrane and easier to do then mixing up caustic chemicals.

Anyone else privy to these details?


Yes PG is preferable to powdered storage solutions. It is better on the membranes and will safely store the membranes for a longer time. With some of my customers larger water makers I remove the membranes and store them separatly in tubes of PG. I've also had customers that have bought boats whose water maker was stored for over two years in PG and worked perfectly on start up. You want to use the -100 PG not the -50 PG
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Old 17-07-2010, 14:51   #15
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-100 meaning Farenheit? I'm definitely gonna use that for next winter instead of sodium metabisulfate.
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