Squeeze Filter and Tannins

My fiance knows all about Flocculation. She's an environmental scientist and works in commericial/stormwater treatment and is CESL certified and talks about floccing all the time. I'll have to ask her about the alum, etc. But seems like treating it would be a hassle considered tannins have never bothered us when filtering water from the same areas you've mentioned, but I could see it becoming a problem if it reduces filter flow. What's nice with the new mini's (or even the old one with the screw on adapter put on a bottle and a tube connecting the filter to the bottle) is you could use some fresh filtered water in a squeeze bag and squeeze it back through the clean end if you don't wanna bring the syringe.

I don't like tannin water

Sometimes you can find a better stream, like just South of Sand Point the stream is pretty tannined, but another 0.1 mile further is a better stream

I'm surprised they'de clog the filter, so small, filter definitely doesn't remove it from the water so it doesn't make sense it would clog it up

Hollow fiber filters are sort of finicky so maybe the flow is reduced for some other reason

Use a soda bottle for dirty water and you can put more pressure through it

Has anyone tried to cover up the tannin taste by adding a powdered drink mix? Does it work or does it just make really nasty tasting Gatorade?

Jerry (and others),

You bring up some good points.

I looked for the clearest water that I could but all the trickles within about a mile of our camp at Toleak Point had tannins in them. I've hiked in this area quite a bit and I notice the condition of the water changes from time to time depending on season, rainfall, etc. One must even be careful at one stream to make sure that salt hasn't entered the still water of the stream from high tides.

"I'm surprised they'de clog the filter."
My experience on this issue, with various filters, has varied and I'm not sure I understand what all is going on. The tannins may even be a red herring and invisible silt mixed in with the tannins following the heavy rains may have been the true culprit. Tannins were definitely the primary cause for the tea like color and taste of the water, however, so they are part of the equation…..even if they simply hide the silt that might also be in there.

Add lemon and honey and tell yourself it's iced tea. :)

Daryl, I've spent some time trying to work out the tannin problem after trips around Ozette, too. I've used that stream south of Sand Point and several others in that area and after filtration with the Squeeze on a couple of occasions I had something resembling pepsi. I found it a little difficult to make myself drink enough of it to stay hydrated. On other trips to the same area it wasn't so bad. I haven't tried using flocculants, but I have some alum in my kit now and I plan to use it whenever I encounter very tannin-rich water next.

I'm also planning to rig up an inline carbon cartridge to go downstream of the Sawyer. This was discussed in another thread and several people who have expertise in this area suggested that this would reduce the tannins in the filtrate.

I think you're right that it is probably something other than tannins that caused your filtration rate to be slow. I do parasitology research and I filter a lot of water collected from field sites along the west coast, to look for Toxoplasma gondii and other parasites. For this I use 0.2 micron hollow fiber filters. I'll be submitting a paper about this technique in December. Subjectively imperceptible gooeyness from biofilm polymers is a major problem for lab filtration of water collected from forest streams that are full of dead leaves and other decaying plant matter. Microbial growth on all of that organic matter produces sticky polysaccharides that cause filtration to go very slowly. This gooeyness occurs under the same conditions that produce high tannin concentrations. I would guess that this explains your slow filtration rate.

I just backflushed the filter and flow is now restored. Used this technique for backflushing:

backflush

I’m not concerned about the look and taste although it is a bit bitter. Everything I read says its harmless.

""I'm surprised they'de clog the filter."
My experience on this issue, with various filters, has varied and I'm not sure I understand what all is going on."

Tannins are generally very small molecules and or water soluble. So it is unlikely they clogged the filter. However Bacteria would utilize it as food. if the water is relatively stagnant the bacteria load in the water is probably very high and it is probably also loaded with organic particulates. It would probably clog most filters in a very short period of time.

I just got back from a 40 mile section of the Arizona Trail. We have had a lot of rain here and I was forced to use dirt tanks for water, the one I got the most water at was surrounded by gambel oaks and the tank had filled a lot and had lots of oak leaves (and frogs) all around the edges. Not cloudy, but not completely clear water, I pre filtered with my bandana while pouring into the sawyer bag. I got about six liters out of the sawyer and it really did not slow down too much in outflow. That's all I wanted to carry. When I returned home I immediately back flushed the filter and wow, did a lot of brown tannin and other stuff come out! I flushed it till the backflow was clear and it seems fine now. I didn't care what the water tasted like, it was like a light tea color and not bitter and got me to my pick up point well hydrated. But I am going to take the syringe with me from now on.

Steven/Colin/Others,

The bacteria/organic particulates/tannin model makes sense to me and would explain some of the observations posted here. For example:

(1) The filtered water is still tea colored because the tannins went through the filter.
(2) The filter gets slower through use because the bacteria and organic particulates are filtered out and build up on the dirty side of the filter
(3) Seasonal variations in the problem could coincide with the natural variation in bacteria growth that accompanies changes in water temp, sun exposure, length of day, etc.
(4) The "stuff" that Desert Dweller observed during back flushing would be mostly bacteria and organic particulates

I think I read somewhere that Sawyer says their filter doesn't need a prefilter. Not so sure I'd agree with them.

>" biofilm polymers (feeding on organics in the influent) are a major problem for lab filtration of water"

Colin: I see the same thing on a large scale. I'll have a 2000-pound-dry-weight carbon vessel (6 feet high, 4 feet in diameter) and get increasing back pressure even with no sediment loading. This only happens with a food (like dissolved gasoline or diesel) in the influent and one can sometimes see the mat of microbes living on the carbon. Backflushing works surprisingly well, high flow rates are better (to the pressure limits of the container and/or fluidizing the bed), and I haven't even needed to put a full pore volume through. Even a pulse of 1/4 of a pore volume significantly reduces back pressure for another week (e.g. backflushing with 100 gallons over 5 minutes might give me good operation during forward flow at 5 gpm for a week (50,000 gallons)).

For a BP filter: I'd suggest a short, quick back flush You're not trying to dissolve some material over time or into a big volume. Just blast off the layer of bioslime that is coating the filter element.

Pressure = good.
High Flow = good.
Big volume = unnecessary.

What color is the microbial film that you see on the media when you're filtering water contaminated with gasoline or diesel? Greenish? I wonder if Pseudomonas is dominant in those mats. It's interesting to me that you see that.

Thanks for the backflushing advice. It's consistent with my observations in the lab. When I use 0.2 um pore hollow fiber filters with a capsule volume of 20ml, and I backflush to recover parasites, I get good recovery (stuff comes back out) when I do a hard (40 psi), rapid, low volume (15 ml) backflush. Increasing the volume doesn't increase the recovery very much.

The backflushing syringes provided with the Sawyers are 60 ml, I think. Maybe a smaller smaller diameter syringe would help people achieve a more effective backflush. The advice should be "to achieve optimal backflushing pressure, choose a backflushing syringe having a diameter in inches equal to 1/200 of your body weight in pounds."

>"What color is the microbial film that you see on the media when you're filtering water contaminated with gasoline or diesel? "

Colin: I see essentially clear films, white mats and white fiberous mats. My understanding is that they get more filament-like to increase their surface area because something is in short supply.

My day job (cleaning up toxic waste sites) could be summarized as making the bacteria happy.

Edit: So we're agreed: a hard, fast push on the syringe is the best technique to clear a filter element and re-establish higher forward flows.

" The "stuff" that Desert Dweller observed during back flushing would be mostly bacteria and organic particulates".

There was a LOT of critters in that water (visible to the eye) also! Smaller than the frogs. Which despite their presence I delight in seeing since I do live where water skaters and bugs are not commonly seen, to me it means a healthy environment. If I see water with no life in it I am very wary of using it. I consider these filters we have now a minor miracle of science..(thank you scientists!!) ..that I can have drinkable water from a dirt cow tank that I don't get sick from consuming…..I will add that I also used my Aquatabs also once the filtered water was in my bottles and bags, just to be safe. It's probably overkill but I have had Giardia once and do NOT want to go through that experience again. That was in 1981 when I did the CDT and only could boil water for drinking, and I believe I got the Giardia from someone's unwashed hands making a meal, not the water.
I've been told that once you have had Giardia that you can't get sick from it again, but I think it's a myth, true or false?

Dweller, that information you got about Giardia is absolutely false. If you remember who told you, you could do them a favor (maybe save them from a bout of Giardia) by letting them know that the information they gave you is wrong. A person can get Giardia many times, even from the same source.

Giardia have a trick called "antigen shifting". Giardia has a repertoire of more than 200 "variant surface proteins" and individual Giardia cells are constantly changing the ones that are on their surface at any given time so your immune system will never be able to recognize them as something it has seen before. There is a Giardia vaccine in development that uses whole inactivated Giardia cells that have been genetically manipulated so all of their protein wardrobe is on the surface at once. This is not likely to confer perfect immunity but it will get one's immune system better acquainted with more of Giardia's disguises, so it is more likely to recognize new Giardia cells as pathogens.