UKC

Hi,

I ordered one of these life straws earlier today as the price seamed great.

http://www.amazon.co.uk/Sunwin-Emergency-Military-Camouflage-Purification/d...

I however cancelled my order within the hour as I did some research on the whole life straw technology.
This is what I found.
Bacteria range in size from 0.2 to 2 microns in width or diameter and from 1 to 10 microns in length for the nonspherical species, so a 1-micron filter will remove most bacteria and cysts.

The above model I almost ended up with is rated at 15 microns , this is way to big to be of any use out in the field.
The original life straw is rated at 0.2 microns this should remove almost everything real nasty from filthy water but 15 microns- wtf

I'm shocked to see these being sold under the assumption that they are going to remove bacteria cysts and parasites.

Glad I didn't waste my money.

:-

M

In reply to MGC:

You're right; in the lab we use 0.45 um or 0.2 um. 0.45 um is small enough to remove bacteria (this is probably because although 0.45 um is the largest pore size in that filter, bacteria ever so slightly below that size will get stuck in the pore network). 15 um is a joke and probably worthy of a question to the ASA.

Bear in mind that all of these filtration solutions will allow the passage of viruses - not normally considered to be a problem, but it's worth remembering if you're somewhere where viruses are ending up in the drinking water.

In reply to MGC:

Well it is a cheap(er) knock off of the lifestraw (the brand)...

Don't find the straw models very usefull anyways. I want a bottle filled with clean water, so a pump/squeeze type is much more usefull for me.

In reply to MGC:

Truly abominable

"Reduces turbidity by filtering down to 15 microns
Removes 99.9999% of waterborne bacteria, protozoan parasites and particles
Can be used in harsh conditions, such as backcountries, refuges, camping sites etc...
Easy access to clean and safe drinking water"

Taken from the description .

I've left a review on Amazon to the effect of how useless and dangerous these could be.


M

In reply to MGC:

Yep, these things are little more than snakeoil. Water treatment comes up as a topic every now and then, worth reading back on this thread:

http://www.ukclimbing.com/forums/t.php?t=577988

In reply to climbwhenready:
I don't study microbiology, but when I filter water samples at 0.45 um I still find that the apparent action of bacteria remains (i.e. the loss of certain nutrients as bacteria consume them). It seems that 0.2 um isn't always effective anyway:
http://www.sciencedirect.com/science/article/pii/S0923250804001287

In reply to Mike Peacock:

0.2um is pretty standard for "clean" water in industry. Most high risk processes like making up injection solutions of drugs you'd use a couple of 0.2um filters in series for a bit of reassurance. I would definitely have words with someone claiming 15um was good for sieving out 99.999% of nasties.

In reply to MGC:

Glad I've seen this I was going to order one ,never even thought about its efficiency,quite dangerous really

In reply to Mike Peacock:

Would it be possible for you to send me a pdf of that paper to my UKC email address please? (Unrelated, and my university has no subscription).

In reply to MGC:
I've done a bit in emergency water treatment and the key thing is to get water under 5NTU, (looks clear, 10 NTU if you have to, still looks clear,) then chlorinate. Whatever you do, make sure you chlorinate. My water treatment stuff I carry is a packet of puritabs (chlorine tablets.)

In reply to MGC:
Could be the mistake is in the description. It's not inconceivable that the marketing person who wrote it would fail to spot the difference between .15 and 15.
I really hope it is something like that.

In reply to matthew:



I thought the same at first but lots of other models on Amazon and eBay quote 15 microns as well.
So its either correct or they have all copied the specification wrong.

M

In reply to ianstevens:

I've just emailed you.