Mar 20, 2012 at 5:02 am #1287494
I am planning a multi day trip along the beautiful but tannin rich Suwanee river. I want to have a filter to use in conjunction with my steripen that will help remove the tannin and improve the taste. I have seen some good ideas on myog gravity filters and I may wind up going that direction. But I wanted to run an idea by the collective genius that is BPL.
Shameless sucking up complete, here is my simple idea; take a 16oz. water bottle, cut the bottom off, glue (superglue or silicone?) a circle of 1 micron Bio diesel filter inside, add an inch or so of charcoal from an aquarium store, then glue a second disk of bio diesel on top of that.
Do you think this would be effective with the tannins? Keep in mind I would be using a steripen (aquamira backup) after filtering.
Thanks in advance for the input.Mar 20, 2012 at 6:20 am #1856459
@retiredjerryLocale: Oregon and Washington
I've used Katadyn filter on tannins in the Olympics
Does nothing to tannins
They must be very small
Tannins are harmless, although I don't like the tasteMar 20, 2012 at 6:41 am #1856467
@dwambaughLocale: Pacific Northwest
I've used a First Need filter on tannins in the Olympics and it reduced it, but did not completely remove it. As I'm writing this, I wonder what effect tannins have on the filter life.
I would use a paper coffee filter with the Steripen– get the big stuff out and live with the rest. I made a filter holder from a seal-a-meal bag. See http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=44546Mar 20, 2012 at 7:59 am #1856508
@flriderLocale: The Southeast
I've also used a Katadyn Hiker Pro (which has an activated charcoal element in the filter) in several places down here in FL. Not the Suwanee, but several tannin-rich streams and ponds (Ocala National Forest, Black Creek Ravines, etc.). It didn't do anything for the tannins, though the taste was better than my Sawyer In-Line offers (no charcoal in that one).
Honestly, I haven't heard of anything portable that gets rid of the tannin in "FL tea". If you find something, please share it with the rest of us!Mar 20, 2012 at 9:23 am #1856540
tanins aren't going to be removed by mechanical filtration. They're soluble, and go through filters. Activated carbon with the right sized pores can adsorb some of the stuff, but not all of them ('Tannins' are a big range of disovled organic molecules, and require a range of activation sizes.) . In commercial water purification systems, tannins are removed by anion exchange (same principal as a water softener to get rid of calcium, but anions (negative charge) instead of cations (positive charge)), which isn't terribly practical on a hike. Reverse osmosis ought to do it too, but again, not terribly lightweight.Mar 20, 2012 at 10:49 am #1856603
Thanks everyone for the insight.
I guess I better change my thought process on this.
Does anyone know where I can hire a sherpa to carry a reverse osmosis/anion exhange system for me? :)
Hopefully if the charcoal doesn't remove the tannins, it will at least taste ok.
Has anyone used silicone on one of these bio diesel filters? I want to seal it around the inside of the water bottle.
RobertMar 20, 2012 at 3:22 pm #1856742
I switch from a steripen to a myog gravity filter when I hike in Tannin rich areas. Maybe it is just me but if the water is colored, then I worry about the light penetrating to kill all of the nasties.
DaveMar 21, 2012 at 11:42 am #1857170
Water treatment works use a flocculant to cause microparticulate matter to precipate out, and this flocculant is often alum (aluminium sulfate).
I wouldn't like to suggest using this, or the amounts that might be needed. However, quoting the above 'cleanwaterstore' website:Quote:One method that we have successfully used to remove tannins in well water involves injecting a flocculant such as alum which allows the microscopic suspended particles that create the color in water, to lose their positive charge and "floc" together into larger clumps. This is easily done on small scale systems by using a metering pump and injecting 2 -5 ppm of "Cat-Floc" (one of many types of flocculant aids used for this purpose) into the water as it flows into a holding tank or storage tank.
It's also worth pointing out that errors can occur at water treatment plants.
If you can persuade the tannins to flocculate, you should be able to filter them out with a conventional filter.
Usual caveats apply…Mar 21, 2012 at 12:16 pm #1857186
Kevin's right about flocculation. And people have had good ideas about carbon. I deal with this at home (middle of a spruce forest) and on toxic waste sites (my day job) and while rafting.
Granular Activated Carbon (GAC) can remove tannins (both the color and the test) from drinking water. The Brita filter in the Brita pitcher does fine at my house, although I hate the price per pound in those little cartridges – when I buy GAC by the thousand pounds, it's $2-3/pound.
I use a lot of GAC vessels, have designed a few, and more often tweak other designs to do what I want. You need a certain contact time and anything that moves the water quickly past the GAC isn't going to acheive high removal efficiency. This makes it not so great for a pumping/sucking scheme because you want that to happen quickly. But it makes GAC ideal for a gravity-fed system because they you care much less how long it takes. Make your carbon container long to maximize contact time and relatively narrow to minimize weight and volume. For 2 people x 10 days, you'd need so little GAC, 1 cm ID by 10-15 cm length would more than do it. Syringe bodies would be one off-the-shelf item of that size and the tips could fit nicely into your tubing (maybe drill out the inside of that tip for better flow and strap two together back-to-back to get those "hose adaptors" on each end. But you could also look for a plastic filter housing with room for a cubic inch of GAC and use fine screen or coarse filter paper to hold in the GAC.
Then play with it – a high head will move more water and maybe that's fine, but if you still see color or taste, use less height in your gravity-flow system for a lower flow and longer contact time.
But the real UL method is bring some alum. It's in the baking or spice aisle at the grocery store, is food grade and really speed up clays and silts settling from the water (think Colorado River water). Just add a pitch to the water in your biggest pot, come back in 15-30 minutes and sediment will have gone to the bottom and they'll be a floating scum layer that was the dissolved tannins. Decant the clear water off gently, and/or use a scrap of (unused!) toilet paper or coffee filter to wipe the scum off the surface/edges of the pot. (Mostly, it adheres to the edges of the pot, and you can eliminate 95% of it by just pouring it gently into other containers. 10-20 grams would last you two weeks – finding a SUL container for it will be most of a weight!
Now, whatever purification you are using – UV, halogens, physical filtration – has less to deal with. UV travels further in clear water. Chlorine and Iodine aren't used up on tannins and sediments. Your filter won't clog up as soon. And some bacteria, cysts, and viruses will have settled or flocc'ed out – potentially a large fraction (90-99%) of them, but I'd still treat with something, but I worry much less about the amount and time of UV or CL/I if the turbidity has so dramatically improved.Mar 21, 2012 at 12:54 pm #1857199
@tylerdLocale: SE US
How about just use the steri pen or aquamira then add a flavoring powder?Mar 21, 2012 at 2:45 pm #1857243
Tannins are NOT harmful. Bugs and wogs in the water can be, but not tannins.
The best way to deal with tanins is to heat the water, add a little sugar and milk, and call it tea or coffee.
CheersMar 21, 2012 at 2:51 pm #1857245
So Americans pay extra to make their water perfectly clear, while Brits and Aussies pay extra to ADD tanins to it?
The groundwater we were pumping up from under an old lumbermill (because of fuels in it) was so rich in tannins it really looked like tea (because that's what tea is – soaked leaves) and everyone called it "bark juice".
Okay, I'll shut up now before we get started on the warm beer / cold beer thing.Mar 21, 2012 at 3:38 pm #1857265
> while Brits and Aussies pay extra to ADD tanins to it?
Dunno 'bout the Poms, but we have free gum leaves which are real good at it :-)
Some country, like swampy stuff, has no clear water. So, no big deal.
CheersMar 21, 2012 at 4:41 pm #1857303
"The best way to deal with tanins is to heat the water, add a little sugar and milk, and call it tea or coffee."
Dang it, Roger, you beat me to it!!!
Historically tannins were used to turn hides into leather. On old method to toughen your feet was to soak your feet in strong tea, to do the same to them!Mar 21, 2012 at 4:45 pm #1857305
Stephen: "soak your feet in strong tea". Thanks, I didn't know that. Makes sense.
Here's the reverse for footwear: Your rubber-soled shoes will have better traction on ice if you wipe the soles with Clorox bleach. Just like the drag racers do to their tires. It softens the rubber and makes it stickier.Mar 22, 2012 at 11:04 am #1857733
> Tannins are NOT harmful.
No that's fair, but the OP was bothered by the taste, so I guess we tried to address his enquiry.
> Bugs and w*** in the water can be, but not tannins.
Roger, be warned if you ever come to the UK, don't use the 'w' word; most definitely not PC, even though I'm sure it must have an entirely different meaning in Oz. It would be like using the 'n' word, before it was 'reclaimed'…
I'd google it for you, but I'm not going to put it in a search engine at work, just in case IT/HR are watching…
Thanks to David; nice to have someone who actually knows what they're talking about, rather than having a vague memory about things…Mar 22, 2012 at 3:01 pm #1857843
> Roger, be warned if you ever come to the UK, don't use the 'w' word; most definitely not PC
Like I care about PC? :-)
Oh yeah, same problem here, but we are a bit more relaxed about it. Also, the phrase 'bugs and wogs' is recognised.
CheersMar 23, 2012 at 4:49 am #1858092
@skeetsLocale: Melbourne, Australia
to bring it back closer to topic: if you didn't remove the tannin, do you think the steripen still works? if so, how stained would it need to be before it was a problem? to put in layman terms, colour of strong overbrewed tea, normal strength tea, or weak tea? I've been ok so far in darkish water in whcih I can see the blue light part penetrating to the edge of the container, so assumed (hoped) the UV was doing likewise. Reasonable or just wishful, blissful ignorance?Mar 23, 2012 at 10:11 am #1858208
We did a 20 mile hike on the Florida Trail along the Suwannee River 3 years ago. We did it over 3 days of hiking. I only remember having to filter our water out of the river once or twice. The taste was fine. It comes out looking like Sweet Tea in my platupus bag. We used a Pur Hiker and a Katadyn Vario filter.
All other water was obtained from the many springs and a couple of spring runs that you'll pass along the trail. I don't remember any "great" campsites along the river, but plenty of great places to stop and relax along the trail in the springs.
The timing of our hike had us walking through the Florida Folk Music Festival at Stephen Foster State Park in White Springs. It was a coincidence and quite the surprise after being on the trail for a few days.
This section of the trail is very sparsely populated and we never saw another hiker while on it.Mar 23, 2012 at 11:20 am #1858247
Here are a few pictures from Steripen test documents of 'clear' and 'challenge' test waters. The test waters are a carefully controlled mix of desolved solids, organic carbons, pH, temperature, etc. Although you have no way of knowing exactly how your water compares in the field, the pictures give you some sense of the clarity standards used in testing.
Hope this helps,Mar 23, 2012 at 1:01 pm #1858295
Thanks again for all the input.
I think I will try the flocculation method. I could use a dedicated 2 liter cut off to allow it to be used as a scoop and flocculation :) vessel. Then just filter into my clean bottle and steripen.
John- We are really looking forward to the trip. Water levels have been really low for a while now, but it should still be nice. We are starting at Stephen Foster, it is a great park.May 27, 2013 at 9:19 pm #1990296
@ckrusorLocale: Northwest US
"Make your carbon container long to maximize contact time and relatively narrow to minimize weight and volume."
David, I'd like to include activated carbon in my gravity filtration setup (to reduce tannins), and I'm trying to decide on a way to package it. You seem like the right person to ask about it.
I don't completely understand your recommendation to use a long, skinny container for the carbon. I understand the objective of maximizing contact time, but, for a given water influx rate, shouldn't short, fat GAC vessels and long, skinny GAC vessels have the same contact time if they have the same volume? The water should move at lower velocity through a container that is short and fat, and higher velocity through a container that is long and narrow, so the transit time in the GAC container should be the same for both if their volume is the same, shouldn't it (assuming they are both cylinders with flow-distributors, like pieces of felt, at each end)? That is, if we imagine an ion in our water (that doesn't get removed by the carbon, say), shouldn't it spend the same amount of time, on average, in containers of either shape? Also, wouldn't the lower velocity of the water, relative to the GAC, improve adsorption in the short, fat container? Further, for a given volume of GAC, a short, fat container could be lighter than a long, skinny one, due to a greater volume to surface area ratio (less wall material), wouldn't it? I've spent all of one hour thinking about this and you think about this for a living, so I'm probably missing some obvious details. Any insights you can provide are appreciated.May 28, 2013 at 5:55 pm #1990569
Colin: You PM'ed me out of retirement to ask about long and narrow versus short and wide carbon vessels.
On the one parameter of "contact time", you are correct that it makes no difference. A certain volume, filled with carbon, will have the same apparent contact time as another volume.
And a short, squat vessel will definitely have less pressure-drop along it's length.
My reason for specifying long and narrow was to avoid "channelized" or "preferential" flow paths.
Taking an extreme example of a one-gallon paint can with inlet and outlet at the center of each end, filled with carbon: Most all of the water flow will be in a straight line from inlet to outlet, about 8 inches. Very, very little flow would go radially out another 3+ inches to the first corner and/or to the outlet-end corners (another 3+ inches of travel). Not only does this decease the average residence/contact time, but it leaves that carbon in the corners under-utilized. And you have "breakthrough" sooner when the carbon in the middle has reached its capacity. From either perspective, you've brought more carbon (weight, bulk) than you needed because you weren't using it all at the same rate.
I do utilize carbon vessels that are relative short and squat. But then there are "distribution manifolds" in the form of "H"s and "E"s of perforated pipe or, often, a layer of highly permeable material like 1.5"+ gravel, then a geotech fabric before the carbon itself. And then a similar collection manifold on the other end. For backpacking, you can avoid the extra piping (or hauling rocks along!) by simply using a longer vessel. Anything 3-4 times or more length than width will use 90% of the carbon pretty efficiently.
Other nuances: while a short, fat container has less surface area and might seem to offer a weight savings, larger diameter pipes need thicker walls for the same pressure rating (not a concern in this application) and thicker walls for crush resistance (which is relevant). A soda straw can have pretty thin walls.
Trying to multi-purpose the components might lead you to use a length of tubing as the carbon vessel. You need some tubing anyway, to have the pressure head. You might save a few adaptors (weight and cost) and such if you don't even convert to and from tubing but made the whole system out of tubing. Small grains of carbon could be poured (when dry) into 1/2" nominal tubing, maybe even 3/8" I.D.
Hope that help clarify my thinking. A bit of fine mesh over the end of the tubing (or a very small, porous plug into the tubing) once you've added 10-20 grams of carbon to the tubing might be all you need. As I posted before, if your water isn't being treated adequately for tannins in such a set up, then reduce the pressure head to reduce the flow, and the percent removed will get better.
Sorry, I keep having more ideas. the "very small, porous plug" in 1/2" tubing could be a bundle of those little, hollow, plastic coffee stirrers (usually red for some reason). 12 or 15 of them would be a tight fit and could then be trimmed off so only 1 cm of their length remained in the tubing. That would allow water through easily, but hold back the carbon grains.May 28, 2013 at 8:47 pm #1990648
@ckrusorLocale: Northwest US
David, thanks for taking a brief hiatus from your retirement to answer my questions.
I had thought of the flow path problem in short, fat vessels. This was my reason for specifying that the hypothetical cylindrical vessels in my question had "flow distributors" made of felt or something similar. I assume, given your explanation of the pipes and gravel you've used, that felt wouldn't work. And I assume that something like perlite wouldn't be a good substitute for gravel because it is too close in particle shape and size to the GAC, and if particles of that shape and size were able to distribute the flow over the cross-section of the vessel then the GAC would do it itself and we wouldn't have this problem.
I also wondered about "flow distributors" shaped like this:
A flow spreader like this has a greater fraction open area near the perimeter and a smaller fraction open area near the center. If the water enters the cylindrical vessel via a tube at the center of one end, I wonder if this kind of flow spreader would keep the flow rates similar everywhere in the vessel (or close). I also wondered about circular flow spreaders that are perforated with larger holes near the perimeter and smaller ones near the center.
The plug of coffee stirrers is a good idea.
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