Water Treatment Ques for Dr. Jordan

Buildup of muck, dirt, and other contaminates will not prevent the chemicals from doing their job of killing 99% of the bacteria and viruses. However, drinking a lot of silt may or not be so very good for you, so it is up to you whether to carry to beefier pre-filter.

[Note: I’ll delete this post later when you get a better reply if this post is not referenced by any other. Don’t want to be “spanked” for destroying “Thread continuity” like I used to a year or so ago.]

>>”My concern is that chemicals are less effective in treating turbid water…assuming “fairly clean looking water” (at least to the naked eye), will a mesh coffee filter clean the water sufficiently to allow the chemicals to do their job?”

Short Answer:

Yes. They can be less effective in turbid water due to biofilm issues. Not sure about your mesh coffee filter, but a paper coffee filter should work fine as a pre-filter. That’s not to say that your mesh filter is NG; I just don’t know.

Long(er) Answer:
Ben, Certainly I’m no expert on this subject, but i do meet the “any” qualification (i know…not what you meant), and just in case you don’t get a reply from a real expert in a reasonable period of time, here’s my two cents on your question and a different modality, yet somewhat similar (in several senses/principles, including the need for pre-filtering) related water treatment method (UV-C).

Ben, I think you know most/all of this already, and are just looking for confirmation.

I think I recall reading Posts (or maybe it was emails) from DrJ on this subject. Basically, IIRC, visible particulate matter can have an effect (a biofilm issue which shields the bacteria somewhat from chem and UV-C). This situation would require a higher concentration of chemicals or longer contact (chems) or dosing (UV-C) times, or a combo of both dose level and time (chems). If using UV-C, one can simply double dose, or reduce the size of the volume of water being purified to…let’s say…500ml and dose it as if it were 1L (inverse-square principle of radiating energy governs levels of UV-C water is subjected to). I believe that the rule of thumb is that if the water is essentially clear, i.e. not turbid, and no big “floaties” (none with your coffee filter approach, i would imagine, right?), the usual dosing and times will work fine.

Also, keep in mind cold water temps reduce the efficacy somewhat of both methods (chems and UV-C; please verify/check this statement as it relates to AqM). And so, with chems more and/or longer is needed. At some point UV-C won’t work at all if the water is too cold due to limitations in the tube that generates the UV-C wavelength light. That is, it won’t produce sufficient intensity, or any, UV-C.

Also, the Siltstopper is a 5-micron prefilter. Don’t know about coffee filters’ pore size, but typical values for pore sizes for typical, commonly encountered paper filters range from 5-15 microns, IIRC. I’m not referring here to the paper filter units/cartridges (or more accurately, older non-ceramic filter technology) found in some backpacking filters – those have much smaller effective pore sizes.

In addition, traditional “disaster” advice does typically include using a paper coffee filter as a pre-filter to improve the efficacy of the “downstream” primary water filtration/purification method. You can always improve pre-filtering (and slow flow rate) by doubling up the coffee filters, or lining your nice gold metal mesh filter with a paper coffee filter. BTW, how do you package/protect your metal filter from damage in your pack? I have one, but figured I would crush and destroy it in my pack. You’re obviously cleverer than I am. Please share your secret.

Additionally, for further info you might refer to the BPL Print Issue #2 if you have it. I think for a couple of bucks or so you can download the reprinted article on AqM and water treatment laboratory Research results in PDF format from the BPL On-Line Store – it’s pretty technical in its presentation of the Research results – definitely not light reading. It might have some info on Aqua Mira efficacy under different conditions.

I hope our resisdent expert, DrJ, can weigh in here and correct any errors or omissions I may have made in this post.

Hi Paul:

Thanks for both the short and long answers. If indeed, only particles that are big enough to be visible will affect the efficacy of chemicals, then I think using my mesh coffee filter is fine. I was concerned about whether sediments and gunk too small to be filtered might still be big enough to affect the workings of the chemicals.

Answering your question, I actually cut a small piece of the filter — just a tad bigger than the opening of the Platypus bladder, so it covers the opening entirely, and wraps around it a bit. I then use an extra bladder cap and cut out almost all of the center (basically a screw-on bottle cap with an opening almost as big as the bladder opening itself). I then screw the cap onto the bladder, with the mesh sandwiched tightly in between. When filling, I either position the bladder in the stream where it gets a vertical water flow — or use my cup to pour water through the opening.

Ben, Great Idea. I knew that you were clever. I’m going to steal your idea if you don’t mind (don’t worry I’m not going to be palming it off anywhere as mine – you’ll get full credit when I share with my co-workers – even though they’re not L/UL, they use Platys – it’s a start).

Just let me reiterate one point from my prev. post. I truly believe that the paper coffee filter is a fine pre-filter. My basis for this is that it is often recommended for inclusion in a “home” survival kit for use as a pre-filter for “disaster” situations when the public water supply may be contaminated with either biological or larger particulate matter (small clumps of iron oxides, sediment, soil, etc). It won’t filter the smaller “bugs”, but will remove the organic particulate matter that is being colonized by the “bugs” and possibly protected by a “film”.

Also, I would guess that on a theoretical basis and perhaps a practical one also, that large amounts microscopic paticulate matter or dissolved chemicals can react with the chemicals in the water dissinfectant. Hopefully, a reasonable amount of this is taken into account when typical dosing is indicated on the product’s packaging.

BTW, you can get unbleached (brown paper) filters in the Supermarket/GroceryStore.

I think it’s worth noting that any oxidizing chemical treatment will expend some of itself oxidizing non-biological debris, regardless of particle size. The more you remove in advance the less chemicals are required to kill the critters, and the less oxidizing byproducts in your drinking water.

Sometimes, filtration is simply the better treatment option.

Paul:

Feel free to try it out. BTW, there’s no need to buy expensive Platypus caps. Some of the el cheapo supermarket store brand bottled water caps fit perfectly! Get one or two of those and c-a-r-e-f-u-l-l-y cut out the center with an X-acto knife (or similar).

The reason I choose the mesh filter over paper is speed. Paper filter absorbs water and thus, it takes almost forever for water to work its way through.

Where’s Ryan today, I wonder???

Ben, Thanks again for the tip (this time on run-of-the-mill water bottle caps). I wouldn’t have thought of that myself.

Also, your comment about the metal mesh speed leads me to believe that the pore size is larger in the metal screen than it is in a paper coffee filter, so larger particulate matter can get through. I don’t think that you need to be concerned if the end result is clear, non-turbid water. Some pre-filters I’ve read descriptions of have 20micron pores, and some even larger. I’m forgetting what the smallest object the typical human eye can perceive, but it’s a lot smaller number than most people would ever guess. I read it once (in microns) and was shocked by how small it was. Somehow, I’m thinking it’s between 20 and 100 microns, but I could be all wet here. I bet someone reading this knows. If so, would you mind posting back and reminding me of the size, please.

[Note: Lighting, distance, contrast, all come into play with the smallest object the human eye can see. It’s normally spoken of a one minute of arc.]

As far as DrJ – he apparently has a life outside of the BPL Forums – we’re going to have to do something about that and figure out a way to get him all for ourselves.

Hi Paul,

I know from using both that metal coffee filters all pass “fines” and result in cloudy coffee, at least compared to paper filters which make perfectly clear coffee (however dark). I don’t think there’s any question that the effective pore size is considerably smaller with paper.

Another consideration is absorbtion–paper filters absorb some of coffee’s oils, etc. altering the taste quite a bit, while the gold-plated mesh filters don’t. Might they also absorb/adsorb certain water contaminants? I haven’t a clue, although it seems likely that biofilm could clog paper filters the same way it can clog filter elements. The good news is that paper filters don’t cost much.

All that said, I’ve never seen a fast and easy scoop-and-fill paper prefilter setup. If one’s going to perfilter then chemically treat, they’ll certainly want a quick method.

Rick, Yeah…understood. Speed is an issue with paper. One way around the speed issue would be a paper pre-filter with more area. Not sure how to implement that in a simple usable way. Have to give it some thought.

Also, if you’re telling me that “fines” get through the metal filter, then they are probably 20microns or larger. How much larger? I don’t know. Too large and they might (??? – DrJ, help) be a problem for AqM and UV-C dosing. I/We need more authoritative input here – I can’t provide that.

Ultimately, I think we’re more interested in mass reduction than absolute particle size. Of course, finer media = greater mass reduction.

From what I read turbidity, as measured in NTU, considers submicron-size particles. (NTU is a measure of light scattering caused by waterborne particles). The instrument calibration standard has a mean particle size of 0.121 micron.

Here’s way, way too much info on calibration:

http://www.amcoclear.com/articles/turbidity.perspective.php

(Sometimes I can’t tell whether a topic has been completely hijacked yet :-)

Rick. Re: Thread Hijacking. I’ve been guilty of it. In this case. Ben’s question (originating post) is pretty much answered until we get a definitive “thus saith the Doc”. The other info on particle size is related to Ben’s question, IMHO. Therefore, I don’t think the Thread’s been officially hijacked yet.

Rick, I guess technically, I was misusing the word turbidity. Particles as small as the NTU is concerned with would be too small for bacteria to colonize, so, i’m guessing here, the biofilm aspect would also be out the window if all of the particles in turbid water were that small. However, in real life, “turbid” water probably has a mixture of particle sizes.

[For Ben’s eyes only – if you’re not Ben, don’t read any further. Ben, if you ever want to see your Thread alive again, put $500 in a brown paper bag and put it under the park bench in Bozeman.]

Paul and Rick:

Interesting discussion — and yes, both of you are still very much on topic. Hopefully, someone can tell me either the mesh filter is sufficient — or a waste of time (and why).

Paul — I’ve just placed the brown paper bag with $500 under the park bench in Bozeman. You can retrieve it now.

Whoooooooooaaaa…. I just read a post somewhere up above stating that some chlorine dioxide will be used oxidizing non organic matter. That is completely false. Chlorine dioxide is not affected by contaminates like silica, rock, sand, or glacial silt. It is affected by organic particulate matter, but only if that buildup of matter is significant according to the dosage size. If you are able to see a few large clumps of this sort of matter, no real significant increase of chlorine dioxide is needed because the of the reactible biomass. Invisible particulate matter, shown in water with tannins or a slight green tint, DOES need more chorine dioxide because the amount of reactible biomass is greater than the oxidatible amount of chlorine dioxide.

chlorine dioxide with react with non-organic iron and manganese and sulfides if these are present in the water. In fact, that is sometimes cited as an advantage of chlorine dioxide in water treatment. So if there’s a lot of iron or manganese or sulfides in the water, you have to use a lot more of chlorine dioxide. But how much more exactly?

ref: http://www.epa.gov/safewater/mdbp/pdf/alter/chapt_4.pdf

Peter, Read again please. You didn’t read what you think you did. Here is what you read regarding paper coffee filters, not AqM:

“Just let me reiterate one point from my prev. post. I truly believe that the paper coffee filter is a fine pre-filter. My basis for this is that it is often recommended for inclusion in a “home” survival kit for use as a pre-filter for “disaster” situations when the public water supply may be contaminated with either biological or larger particulate matter (small clumps of iron oxides, sediment, soil, etc).”

Frank, Thanks for the URL to the PDF doc. You’re proving to be a veritable treasure trove of valuable informatino. The article should prove interesting reading. Do you have any good links to the subject of “Biofilm”? Never even covered the topic relative to disinfecting water 30+ years ago in all of microbiology courses I had. Must be a topic of interest more recently than the early 70’s (either that, or I slept through that lecture).

Cool Idea, Ben! (Referring to Ben’s Response, which is the 4th post) I was thinking about your “pre-fiter” and wonder if I might suggest an improvement? Pouring water into this arrangement would lead to a lot of overflow I would think. So, why not create a platy funnel. Cut your disk of mesh insert as before but leave the sport top intact when screwing it down on top of the mesh disk. Cut the platy bottle down so that inverted it creats a funnel. Then pour your water into the inverted platy funnel and let it flow into an open platy bottle. No need for a cup to disinfect because the sport top can be closed when you fill the funnel and opened over the mouth of the bottle to be filled. What do you think?

That would work… although it means sacrificing a platy and making sure that you maintain a “connection” between the sport cap of the platy funnel and the opening of the receiving platy.

For me, the overflow isn’t much of a problem if I’m next to a stream and water is plentiful. But if you want to minimize overflow, this should work too — there is a very fine, non-absorbent mesh filter built into the funnel. Probably easier to balance this over the platy opening as you pour water into it.

Ben, Same funnel. Cheaper Price I’ve got different colored ones for different types of fuel (blue = kero; red = white gas; yellow = alc.). Never thought to try them as a prefilter. I’m thinking that cutting the funnel tip closer to the funnel would improve flow rate.

Good catch! I got a bit lazy and just linked REI because I knew they carry it. Maybe I shouldn’t admit this, but I got mine at Wal Mart.

Ben,

What was that you said before in the UL PIllow Thread about you and I being the same? I think you know what I mean (that’s how I got three different colors).

Rick writes:

>> I think it’s worth noting that any oxidizing chemical treatment will expend some of itself oxidizing non-biological debris, regardless of particle size. The more you remove in advance the less chemicals are required to kill the critters, and the less oxidizing byproducts in your drinking water.

This is true, and the main reason why I’m a fan of chlorine dioxide based treatments vs. iodine or chlorine based treatments.

Chlorine dioxide is more selective than chlorine (bleach) or iodine at oxidizing or otherwise reacting with nonbiological materials, such as naturally occurring nonbiological organic matter (e.g., the decaying plant materials that makes water tea-colored) and inorganic particulates (e.g., silt and its associated mineral coatings).

In addition, bacteria (and to some extent, cysts) have the capability of forming oxidation-resistant biological walls/membranes around the cell(s) that can render iodine or chlorine treatment partially or wholly ineffective, while chlorine dioxide still nails it. EPA says it may take 4 hours (note: for a “complete kill”) with chlorine dioxide. It could take “days” (effectively, never) for free Cl or I in some cases.

Sorry PJ, I wasn’t refering to you, I was refering to what Rick Dreher stated about the nonorganic matter.

Ryan:

Curious, how do you usually treat your water?