CAN YOU SOLVE THIS? From a water lab!

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Dorp
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CAN YOU SOLVE THIS? From a water lab!

Postby Dorp » Mon Sep 21, 2009 6:02 pm UTC

Hey, all. I work in a water quality lab in the state of Alaska and we've just run into an interesting problem. One of our clients, wanting to test his metallic water for iron content, sent us a number of samples to run. Strange things began happening, however, and none of us can figure it out. I tried to think of the smartest (free) forum I could find, and this was it! It's not a question we absolutely need answered, since we just do the testing and tell the client their results, but we're all really curious how this came about.

So here are the haps:
1. Client's sample is clear upon arrival, but after sitting 24 hrs in a dark refridgerator separates into a dark red/pink colour on bottom and clear to yellow colour on top.
2. When tested for iron and manganese, count came back to less than .1mg per liter. Sample was not run incorrectly or switched with another sample.
3. When acidified to less than pH 2 with nitric acid, sample does not separate out and remains clear after more than 48 hours settling time. The method we use to test metals requires nitric preservation, so metals fraction is clear while alkalinity fraction is pink/yellow.
4. Water's natural pH is low, around 6.2
5. Tested negative for total coliforms and e.coli

I could probably get more information if you think you need it, but I don't want to go digging around in the report folder if I don't have to. So! Can anyone solve this mystery?? I'm just the microbiology analyst, so I can't make heads or tails of it.

Thanks, xkcd boards!

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Charlie!
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby Charlie! » Mon Sep 21, 2009 6:37 pm UTC

Red algae maybe? Pink-producing bacteria (I forget the name of the really common ones)? Can you see red particles when you put it under a microscope, or is the spread even?
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scarecrovv
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby scarecrovv » Mon Sep 21, 2009 6:46 pm UTC

I like Charlie's idea: Look at it under a microscope and see if the color is uniform or clumped. If it's clumped, examine the clumps.

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frezik
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby frezik » Mon Sep 21, 2009 7:14 pm UTC

A reaction involving a leftover cleaning agent, perhaps? I'd presume you have no control over how your client takes the sample.
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drosophila
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby drosophila » Mon Sep 21, 2009 7:43 pm UTC

Charlie! wrote:Pink-producing bacteria (I forget the name of the really common ones)?

Serratia marcescens? http://en.wikipedia.org/wiki/Serratia_marcescens
They're ubiquitous, produce red or pink pigment, and would definitely be killed @pH <2.

Also, you might could want to think in the direction of molds and fungi (As a not very hard-and-fast rule, they tend to outgrow bacteria @ lower temperatures).

In any case, I would boil a small sample of your water before you put it in the refrigerator and see if it does the same thing. That could help you tell the difference between a microorganism having this effect and a chemical.

nsmjohn
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby nsmjohn » Mon Sep 21, 2009 8:03 pm UTC

If it is important to you I could ask one of the Water Quality Engineers I work with. I work for the EPA.
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dedalus
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby dedalus » Tue Sep 22, 2009 10:13 am UTC

Seeing as you have the same phase throughout your system (right?), it's sounding a lot like coagulation of some kind as people are saying. See if you can filter off the red colour with a millipore filter? That'd be a clear indication of whether or not it's bacteria of some sort. If it's actually dissolved matter, check if it's a colloidal system (shine a laser through see if it scatters), otherwise I'm fairly lost as to how the colour gradation is occurring.
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Agent_Irons
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby Agent_Irons » Tue Sep 22, 2009 4:01 pm UTC

There's always the possibility that your fridge is haunted by the ghosts of long-dead water quality activists, and they're precipitating out blood into the water.

More seriously, the posters above me seem to have it.

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Velifer
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Re: CAN YOU SOLVE THIS? From a water lab!

Postby Velifer » Tue Sep 22, 2009 6:01 pm UTC

Does the customer have a private water supply? Is he chlorinating/brominating or otherwise treating it (be sure to ask specifically about whole-house filters that hide in the basement)? What are the details on the source water (what aquifer geology, what surrounding land uses) and what is going on between the wellhead and the tap?

Cheap exploration:
Test for nitrate, nitrite, and total phosphorus--especially if free phosphorus is 0.

Wild speculation: If he has a filtration system/holding system and hasn't been taking care of it, it could be Methylobacterium.
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