Water Treatment Thoughts for Outdoor Activities
Updated February 2009
The information here is, to the best of my knowledge, accurate. Any
information here can and should be checked against other sources
before making any decisions about water treatment. Do a
little research of your own and be your own judge. If you
find something not true or think I am missing an important fact
feel free to contact me, I am always open to suggestions and
You can go out and buy what ever filter a friend or a sales person
recommends to you. Or you could choose to get a little information first,
then make an informed decision. A decision you will feel confident about. If you choose the later,
I hope this will help point you in the right direction.
People commonly think the water around them on an outdoor adventure is safe
because it is in the great out doors. They picture a guy
hiking along a stream where no man has gone before (so they think).
The man takes out his cup and scoops up some good clean mountain
water. If you do this chances are you will be just fine, but
there is also a chance of getting very sick. The chances of
getting sick are much higher than you may think.
I chuckle when I hear someone say they are in an area where no one goes so
they are safe from contamination. Truth is people go everywhere. It is rare a
person will hike or pack somewhere without getting some information on the area
first. Where do they think this information came from? Most people want to
hike or backpack in an interesting place so we all pick similar places. It
would be very difficult to find a place to hike or pack where no one ever goes.
Taking people out of the equation, think of all the animal feces upstream and on
the banks of the stream (where rain water can wash over it and run into the
Protozoa (E. Coli or Salmonella), bacteria (Cryptosporidium or Giardia),
viruses (Polio, Hepatitis A and Norwalk Virus), chemical (pesticides etc) and
metals (metals and minerals in high concentrations) can all be spread through
water. Protozoa, bacteria and viruses get into the water when feces
containing these bacteria viruses come in contact with the water. Rain water
running over the feces and then running into the water can also get the bacteria
into the water you want to drink. Think of all the animals out there that may
shitting in the water upstream from you. Think of all the animals that have
shit on the hill side where rain water has washed across their feces then into
the stream you want to drink from. Freezing does not kill all bacteria, so that
fresh snow melt you are drinking from can carry bacteria in it as well.
I have found dead animals lying next to or in streams. They have either
fallen from a cliff or been killed by a predator like a mountain lion. Imagine
walking in a beautiful place and getting thirsty. You walk over to the stream
scoop up some water and have a drink. It tastes great. You start hiking up
stream and find a dead animal laying in the water about 100 feet up stream from
where you just scooped up that water. Doesn't feel to safe now does it?
Chemical contamination is also something to be concerned with. I have hiked
near a stream that looked inviting enough to drink from. After looking further
up stream I changed my mind. I found the stream started from a spring inside an
old lead mine. You never know what is up stream. The lead was not put there by
the miners, it is naturally occurring since it’s what they were after. With
that in mind you can have naturally occurring chemicals or metals in the water
you drink as well.
The Narrows at Zion National Park is a good example of possible bacterial,
viral or chemical pollution. If you decide to travel the entire Narrows in Zion,
you will find the trip starts by traveling through someone's farm land
(Chamberlains Ranch) with cattle and meadows. A stream runs through it and into
the Narrows. Any chemicals used on that farm land have the potential to run
downstream into the water you will want to drink on your trip. Any bacteria of
viruses in the feces of the cattle will also likely end up in the water as well.
The bottom line is, the water you are visiting could very easily be
contaminated, so keep that in mind and do something to protect yourself.
What are we trying to filter out of the water?
Protozoa are usually single celled organisms and are usually a eukaryote (has a nucleolus).
Protozoa are the largest of the things we are trying to filter out, aside from
large debris in the water like dirt particles. They are said to range from
2 microns in size and larger. Chemical treatment will take care of some but
not all protozoa. Boiling is very effective at killing protozoa.
Filtering is effective at removing protozoa with a recommended absolute pore
size of 1 micron or less. In the protozoan group are Giardia and
Cryptosporidium. These are the two major things you will hear about that
need to be filtered out in this category.
Cryptosporidium (single celled parasite) was very rarely found in
humans in the U.S. until the 1980's. Now animals, that's another story.
There are a lot of different species of Cryptosporidium. The one that is
found in infected humans is Cryptosporidium Parvum, or C. Parvum. It has
been documented that Cryptosporidium has spread through municipal water
systems, even though those systems met the federal water treatment standards.
1987 in Carrollton, Georgia and 1993 in Milwaukee, Wisconsin. Low levels
of the Cryptosporidium Oosysts (Oh-oh-syst) are present in municipal drinking
water systems since the methods used, only get rid of most but not all of the
Cryptosporidium. It is not known the number of Oosysts needed to cause
infection but the low levels normally found in municipal drinking water systems is not
usually something to be concerned with.
Cryptosporidium lives in the intestines and is excreted
in the feces. It is spread in a lot of ways. The most commonly thought of
method is feces coming in contact with the water we drink or rain water running
across contaminated feces then running into the water we will drink.
Anytime you get it in your mouth you can be infected, even if the amount of
Cryptosporidium is minute. If manure was used to fertilize the veggies
you are eating and you did not wash them well, there may be Cryptosporidium
present that can infect you. Drinking untreated or poorly treated water
can infect you. You could swallow a small amount of water in a
chlorinated swimming pool and be infected since chlorine is not effective at
killing it. It can spread from person to
person through contact like changing a diaper or shaking hands with someone that has
touched feces. It is surprising to think of all the ways you could get a
very small amount of this to your mouth. Washing your hands and general
personal hygiene is extremely important when trying to prevent the infection.
Cryptosporidium is very resistant to most forms of chemical treatment like
Iodine or Chlorine. Boiling water is effective but must be maintained at
a rolling boil for about 2 minutes. Although the size of the protozoa
group is 2 microns and above it is recommended that a filter with a pore size
of 1 micron or less be used to remove it. The pore size must be absolute
not nominal. Nominal pore size means approximate or average pore size.
Absolute pore size means the pores will be no larger than the size stated.
Freezing the water has not proven to be a reliable way to kill
The illness caused by Cryptosporidium is called Cryptosporidiosis and is
similar to Giardiasis. Symptoms are watery diarrhea, abdominal cramps,
nausea, low fever, and dehydration. The symptoms usually develop 4 to 6
days after infection but have been known to develop between 2 - 10 days.
Healthy individuals can be ill for several days usually not more than 2 weeks
and some don't get ill at all. Cryptosporidium can be deadly to those
with a weakened immune system rather it be from HIV, chemotherapy, drugs that
degrade the immune system, etc. Cryptosporidium cannot be diagnosed by
symptoms alone since the symptoms are similar to a lot of other conditions.
The medical profession says Cryptosporidium has no cure other than wait and
let it pass. There have been some documented successes with certain
antibiotics but not enough to say they have a quick fix for the problem.
There are some herbal cures out there that claim to get rid of Cryptosporidium.
Cryptosporidium Oosysts are present in most surface bodies of water in the
U.S. and are more abundant after heavy rains. According to the EPA,
Cryptosporidium is the leading cause of waterborne illness in the United
Giardia or Giardia Lamblia (a single celled parasite) has been around
for a long time. I did not run across any information about how long
Giardia has been present in the U.S. but it has been here for quite some time.
In Europe it is sometimes referred to as Lamblia Intestinalis. Giardia
lives in the intestines and is spread through feces just as Cryptosporidium.
It is protected by an outer shell that allows the Giardia to live outside the
body for long periods of time. Giardia is spread the same ways that
Cryptosporidium is and the same precautions with personal hygiene should be
observed to help prevent infection.
Giardia can be treated with chemicals such as chlorine
and iodine. Boiling water is effective at killing
Giardia and filtering will remove it
as well. The 1 micron pore size recommended for filtering
Cryptosporidium will remove Giardia as well.
The illness caused by Giardia is known as Giardiasis (sometimes known as
Beaver Fever because Giardia is thought to be wide spread among beavers) and
is the most frequent cause of non-bacterial diarrhea in North America.
It is an infection of the small intestine. Symptoms are watery diarrhea,
stomach cramps, upset stomach and dehydration. Some people show no
symptoms at all. Symptoms usually begin 1 to 2 weeks after infection.
The illness usually lasts for 2 to 6 weeks but has been known to last for
months or years. Chronic cases are hard to treat. There are a few
strains of Giardia and there is more than one that can infect a human.
Different people will have different symptoms and different levels of severity
when exposed to the same strain. One strain is not more severe than
another it varies from person to person. Unlike Cryptosporidium where
low levels are tolerable it is possible for one Giardia cyst to infect you.
Giardia cannot be diagnosed by symptoms alone since the symptoms are similar
to a lot of other conditions. There are drugs your doctor can give you to
treat Giardia. Some individuals exhibit some immunity after being
Giardia is more prevalent in children and is common in a lot of day care
centers especially those that do diaper changes. One study from
backpacker magazine (Dec. 1996) looked at 10,000 samples from streams all
across the U.S. and Giardia was found in everyone. The incidents in the
U.S. population are estimated to be around 2%.
Bacteria are usually a single celled organisms and are usually a prokaryote (has no nucleolus).
Fecal Coliforms is a collective term referring to all bacteria, as a whole, found in fecal matter from
humans and animals. The size of bacteria is said to range from 0.2 microns and
larger. Larger bacteria can be filtered out with a micro filter but to
remove the smaller bacteria a sub micron pore size is required. Bacteria are responsible for
diseases like Cholera, Typhoid Fever, E. Coli and Salmonella.
E. Coli or Escherichia Coli is a bacteria with hundreds of different
strains. It may be surprising for you to hear most strains are harmless
and are naturally present in most animals and humans. E. Coli is one of
the dominant species of bacteria found in human feces. The E. Coli
bacteria help prevent the growth of other harmful bacteria in the intestines.
E. Coli also
produces appreciable amounts of vitamins. When you
hear of E. Coli, harmless is not a word that usually
comes to mind. That's because we never hear of all
the good strains of E. Coli, all we hear about are the bad strains and
how they made someone sick. There are very few strains of E. Coli that
cause illness in humans. One of the harmful strains of E. Coli produces
powerful toxins that can severely damage the
lining of the intestines causing a severe illness. That is the strain
usually referred to when you hear about E. Coli. This strain is called E.
Coli O157:H7 and is one of the more rare strains. It was first recognized
as a cause of illness in 1982.
E. Coli. lives in the intestines like Cryptosporidium and spreads through
feces as well. So it is spread the same way as
Cryptosporidium. Healthy cattle can carry it in their intestines, so
needless to say meat can become infected during slaughter. Ground beef is
especially susceptible to being contaminated since E. Coli. can be mixed in
during the grinding process. Infected meat can smell and look normal.
Raw milk can be contaminated by the bacteria being on the cows nipples or on the
equipment used to milk the cow. Pasteurized milk is a good choice since the
pasteurizing process kills the E. Coli.. Water contaminated from sewage
can also be a source of infection, and that is what makes this something to be
aware of when camping. If an animal can shit in the water you are drinking
it is possible for you to be contaminated with E. Coli. The amount of E.
Coli. needed for infection to occur is not known but thought to be very small.
Boiling the water for more than 1 minute, chemicals such as chlorine and
filters (with an absolute pore size of 0.2 microns or less) are all
effective at eliminating the risk from E. Coli.
The disease caused by E. Coli O157:H7 is called Hemorrhagic colitis.
Hemorrhagic colitis usually starts with abdominal pains and watery diarrhea which can
produce grossly bloody diarrhea. Usually there is little or no
fever and some individuals have no symptoms at all. The illness usually
resolves itself in 5 to 10 days without antibiotics. Antibiotics have not
been shown to improve recovery and it is thought that the antibiotics may
increase the chances of kidney problems. Anti diarrheal agents should be
avoided as well but I haven't found an explanation as to why.
Infection with E. coli O157:H7 is diagnosed by detecting the
bacterium in the stool. Most laboratories do not test for E. Coli 0157:H7
so you need to make a special request to test for it. If you have bloody
diarrhea you should ask for your stool to be tested. The method to ask for
when testing is sorbitol-MacConkey (SMAC) agar. It is thought that 2% to 7% of
infections lead to Hemolytic Uremic Syndrome, in which the red blood cells
are destroyed and the kidneys fail. This usually occurs in young children and the
elderly. In the United States Hemolytic Uremic Syndrome is one of
the leading causes of acute kidney failure in children and most cases of it are
caused by E. Coli 0157:H7. Hemolytic Uremic Syndrome has a death rate of
3% to 5% when the patient is in intensive care and about 1/3 of people with
Hemolytic Uremic Syndrome have abnormal kidney function later in life.
About 8% of the people with Hemolytic Uremic Syndrome develop other lifelong
complications like high blood pressure, seizures, blindness, and paralysis.
Hemorrhagic colitis is not a common occurrence, but the actual rate of
occurrence is not known. People with severe symptoms will seek medical
help. People with less sever or no symptoms are much less likely to seek
help and the condition only lasts a few days in some cases. In the Pacific
Northwest, E. coli O157:H7 is thought to be second only to Salmonella as
a cause of bacterial diarrhea.
Salmonella is a rod shaped bacteria that is wide spread in birds and
pigs. It was first discovered in the intestine of a pig in 1885 by Daniel
E. Salmon. Environmental sources of salmonella are water, soil, animal
feces, raw meats and any surface that may have come in contact with these
things. Since salmonella is a bacteria, lives in the intestines and is
present in fecal matter the precautions and methods of spread are the same as
for Cryptosporidium or E. Coli.
Boiling the water for more than 1 minute, chemicals such as iodine and
filters of the proper size are all effective at eliminating the risk from
Salmonella. I have not yet found a source that
tells what size a Salmonella bacteria is. The only
reference I can find is the advertising of water filters
saying they take care of Salmonella because they filter
down to 0.2 microns. Take it for what it is worth,
just remember it is advertising.
Salmonella can cause typhoid and other intestinal diseases, some of which will
have a typhoid like fever. The strain that causes typhoid is Salmonella Typhi. Typhoid fever is rare in the United States today but other
illnesses caused from Salmonella are common and are collectively called
Salmonellosis. Other symptoms are nausea, vomiting, abdominal
cramps, diarrhea and headache. 3 to 4 weeks after the symptoms cease there
is sometimes a period of arthritic symptoms. The time from infection to
symptoms is usually 6-48 hours. The infective dose is around 15 to 20
cells. Symptoms usually last 1 or 2 days but can go on longer. It is
estimated that 2 to 4 million cases of salmonella occur annually in the United
Campylobacter Jenuni or C. Jenuni or Campy is another bacteria.
Healthy humans do not usually carry C. Jenuni but it is often found in
cattle, chickens and other animals. Flies can also carry C. Jenuni.
The disease caused by C. Jenuni is called Campylobacteriosis
and is often
called campylobacter enteritis or gastroenteritis. The symptoms are
diarrhea (bloody or non-bloody), nausea, headache and muscle ache. These
symptoms are just about the same as a lot of other viruses so diagnosis cannot
be done by simply looking at the symptoms. The disease usually lasts 7 to
10 days. About 25% of cases involve a relapse. The disease will go
away on its own with out antibiotics but some antibiotics can help reduce the
According to surveys referenced in the FDA's Bad Bug Book C. Jenuni is the
leading cause of bacterial diarrheal illness in the United States. A study
in the 1980's found 23% of patients showing up at a clinic near Grand Teton
National Park were infected with Campy as compared to 8% infected with Giardia.
In 1996 a clinic reported seeing about 2 cases of Campy infection for every 1
case of Giardia.
Viruses are the smallest microorganisms and some cannot be removed by filtering.
They are said to be 0.004 microns and larger. Wilderness studies suggest
that 60% of all back country illnesses are actually caused by bacteria and
viruses. Viruses can cause Polio, Hepatitis A and Norwalk Virus. Boiling
and chemical disinfecting can effectively kill viruses. In general viral
infections from back country waters are very few compared to bacterial
infections. Viruses that effect humans are usually only present in water
that has come in contact with human feces. A virus will usually have a
short life span after it is outside the human body. A class we were put
through at my work informed us that Hepatitis is actually more of a danger than
HIV. While HIV lives outside the body for a few minutes or hours,
Hepatitis can live outside the body for up to 5 days. Lets face it a large
percentage of places you will back pack in have been visited by other humans.
This in itself indicates there is a risk of viral infection when you are in the
wilderness. So even though the chance of viral infection is low it still
is a possibility and should be considered when making your decision on a water
Chemicals and Metals:
I have not looked into chemicals or metals at this point and am not sure I will.
But they are listed just as a reminder that they do exist. If anyone
has information that might be of interest in relation to the topic of
this page relating to chemicals or metals please email me and share.
Protozoa, bacteria and viruses can cause major problems when exposed to a very
small amount because they get into your body and begin
multiplying. Chemicals and metals in the waters may enter the body in
small amounts but do not multiply. A camper may
come in contact with low concentrations of metals or
chemicals. Extended exposure to these may
develop problems, but short term exposure, like that of a camping trip, to low
the levels of the metals and chemicals in the water usually do not cause
complications. That is the main reason I have not put any effort into
looking for information for removing metals or chemicals.
Chemicals and metals in your water are definite
possibilities when camping. I have done a pack
trip through the Narrows in Zion National Park.
The trip starts out by traveling through someone's farm
land (Chamberlains Ranch) with cattle and meadows. A small stream runs
through this farm land and is part of the water that is
makes up the water in the Narrows. Any chemicals
used in that farm land have the potential to end up in
the water you would filter down stream for drinking.
I have also done some hiking in areas I would enjoy
going back to for an over night since it was beautiful
and had a nice stream. Hiking further up the
stream made me not want to camp there. The water
was coming from a spring that was inside an old lead
mine. Both of these water sources would appear
safe if you did not know what was up stream.
What are the Water Treatment Choices?
Boiling the water is very effective at killing living things from the
water like protozoa, bacteria and viruses but does not neutralize chemicals or
physically remove the bacteria. I do not like the idea of boiling water on a back
packing trip unless its the only option.
If you do boil water as a method of treating water, the common
recommendation is to keep the water at a rolling boil for at least 1 minute at
sea level and add 1 minute for every 1,000 feet above sea level.
Adding this time can add to lengthy boil times and
add to the amount of fuel that needs to be carried
along. The reason for adding time is the
temperature of boiling water changes with
atmospheric pressure (altitude). At sea level
water boils at 212°F. At 7000 feet the
temperature drops to below 200°F.
Chemical treatment is usually done with chlorine or iodine. It has
the advantage of being one of the lightest most compact methods. All you
need is a small bottle of liquid or tablets. Chlorine is not effective
against some viruses so is not the most popular method. Iodine works well
against viruses, protozoa and bacteria but usually doesn't kill Cryptosporidium.
The down side to chemical treatment is the time involved in waiting for your
water to be safe. You put the chemical in your water and wait for the
prescribed time and you are good to go, usually 30 minutes (up to 4 hours or
more for CryptoSporidium). Iodine is not recommended for
continuous use. If used too much it is actually a poison.
UV light Treatment
Treating water with UV light has proven effective as
well. Advertising for products like the
say it kills viruses and bacteria (including
cryptosporidium) in seconds. Other sources I have
found on the subject say things like mostly effective
and somewhat effective.
Using this method consists of putting water into a
container and inserting a UV light source in the
container to disinfect the water by irradiating it with
UV. The amount of water to be treated at any one
time should be kept small so the UV light can reach all
of the water. If more that 0.5 or 1 liter of water
is desired, the water must be treated in batches.
While there are no filters or cartridges to change,
batteries are required.
A filter is considered to be 1 to 4 microns, and a micro filter is considered to be 0.2 to 1 microns.
A micron is one one millionth of a meter or 0.0000394 inches. Filtration has
the advantage of taking less time than boiling or chemical
treatment, is usually lighter than the fuel carried for boiling water and unlike
boiling or chemical treatment, filtration completely
removes the contaminants in question. The down side is the pore size of even the best filters are
rarely below 0.2 microns, which is not small enough to filter out some viruses.
Although you do not have to pack extra fuel as with boiling you do still need to
carry the filter.
Filtering will meet almost all of your drinking water needs with the exception
of some viruses. Since infections due to viruses are not very common
filters are considered to be all you need for safe back
Filtering also increases the odds that you will
filter out other things that boiling and chemical
treatment will not, like metals or chemicals,
depending on the size of the particles. It is
not the intent of filters to remove chemicals or
metals but depending on sizes some of these may be
removed as well.
When selecting a filter look for the smallest pore
size you can find. Also look to see that the
pore size is rated as absolute and not nominal.
Nominal means it is the average size. If the
average size is 1 micron then there are holes that
are larger and smaller than that size. Not
comforting when you are depending on that pore size
to protect your health.
Purification seems to be a term no one will agree on
a definition for. Some say filtering below 0.004
microns is purification, others say it takes a 2
step process to be called a purifier, filtration
then another form of treatment to eliminate other
risks. I subscribe more to the 2 step definition.
But in reality pure would mean an absence of
everything except water. Each water filter company seems to have it's
own view of what purification means.
To me pure means the absence of foreign material (impurities). Chemical treatment
renders the water SAFE not PURE. Filtration removes most but not all (depending on
the size) impurities so it too makes the water SAFE not PURE.
Purification when thinking about what you do to your water in the back country is
usually considered a 2 step process, filter then some other form of treatment.
Most of the purifiers I have found that use filtration and another process
are bottle types. A bottle you fill up with a cartridge in it that
filters the water through a straw you drink from. These involve a filter, some other form of killing things (usually a proprietary name for the process so
you don't know exactly what the process is) and sometimes a carbon filter as
well. tadyn makes a few of these if you wish to look some of them up.
The problem I have with the bottle type of purifiers is they are only easy to
use if you only need the amount of water the bottle will hold. If you want
to fill up a 100 ounce water bladder it won't be a fun project.
There are two systems I have run across that are mistakenly called purifiers.
These two systems use a chemical process to kill any protozoa, bacteria and
viruses present. The dead microorganisms are still in the water.
This makes the water safe to drink, but in my opinion should
not be called purified water. The two systems are Micropur MP1
tablets by Katadyn and the MIOX purifier by MSR.
These are some good systems but are obviously
The Katadyne Micropur MP1 tablets
are used like iodine and are effective against all living things in the water.
The water is safe from everything except Cryptosporidium (under the
category of cycts) in 30 minutes. Cryptosporidium is said to take 4 hours. Their literature indicates
that it may take less time but the EPA requires them to list the time for worst case
scenario which is cysts in cold and dirty water.
The MSR chemical
treatment system called the MIOX
purifier, uses regular salt and transforms it into a combination of
antioxidants through an electrolysis process. The antioxidant blend is
poured into the water and effectively renders it safe from protozoa, bacteria
and viruses by killing them. Your water is safe from everything except
Cryptosporidium i in 30 minutes but you have to
wait up to 4 hours to kill Cryptosporidium.
Just like MP1 the time is most likely less but is
posted as worst case scenario. I like this
unit due to it's small size and that it kills
everything living and it uses ordinary table salt
and weighs in at 8 oz.
makes a purifier called the
First Need Purifier that uses filtration (0.4 microns
absolute pore size, 0.1 nominal pore size) then a proprietary non-chemical
three step process to remove a lot of other things from the water and is set up like a standard
pump style water filter. The process is called Structured Matrix. I
called to find out more of how Structured Matrix works and was told it is a
proprietary trade secret but the web site gave a quick run down. For the
explanation go to the Q&A
section on their site and scroll down to "What is structured matrix". First Need
removes (not kills) the protozoa, bacteria and viruses. The
Structured Matrix removes e even more. It also removes some of the
more common pesticides, PCB's and other natural and non-natural chemicals.
The other purifiers I have found do not go this far.
The only draw back is the absolute pore size of the
filter is 0.4 microns. If this were only a filter
this would not be small enough. Since the other
phases of their system work on the water after the
filter I felt safe with this system.
I do not like chemical treatments. They are
light but require wait times and are marginally
effective against cryptosporidium. Using the
chemical treatments to excess can also be bad for
your health. I am not yet fond of the UV light
treatment method. I am not yet confident about
it's effectiveness in killing cryptosporidium.
The advertising says it works great in only seconds.
Other sources describing it's effectiveness in not
so confident terms. I am also not fond of the
batteries depleting while on a trip. Both
chemical and UV treatment leave the offenders in the
water even though they are killed.
Boiling water can be very effective but requires
taking time to set up the stove and boil the water.
Along with the time to boil the water is the extra
fuel that needs to be carried. Boiling water,
like chemical and UV treatment leaves the offenders
in the water even though it is dead. I reserve
the boil method for use when my purifier is not
Filtering removes the bacteria and protozoa from the
water. No need to try to kill it, just remove
it. Unfortunately viruses are generally too
small for a filter to remove.
Purification is my choice for water treatment.
Purifying water has no accepted definition. I
prefer the definition of filtration then an
additional method(s) of removing more. The
MIOX and MP1 systems are advertised as purifiers but
are just better versions of chemical treatments.
Purification removes what it can by filtration then
kills and removes more through other proccesses.
First Need Purifier by General Ecology
is in my opinion the best choice. The unit weighs
15 ounces which is similar to the weight of most pump
style filters. The First Need Purifier is pump
style so there is no need to carry a power source
(batteries). The purifier is
field cleanable with a back washable cartridge and can
attach directly to most bottles including an MSR
Dromedary bag which eliminates the need for an output
hose (I have always hated dealing with two hoses for the
filtering process). The water is ready to drink
immediately, everything is killed or removed and there is only one
step to the process. The Purifier also removes
some chemicals, pesticides and PCB's. Pesticides
my not be a very common thing to worry about but it is
possible and as is finding water contaminated with
metals. Another nice feature of the First Need is it can be gravity fed as
well. You can attach the input hose to a bag of water supported over the
First Need and walk away while it filters large amounts of water for you.
This would be a good feature for groups of people or for just one person if you are
not in a hurry for your water and don't feel like pumping.
Choosing a Safe Water Source
If possible choose water that is clear and still. Some bacteria like Giardia will sink to
the bottom in still water. Avoid collecting water near areas that
have obvious human or animal activity. Trail crossings,
meadows with cow pies, camp sites near by, animals around the water, active or
inactive mines near by (mines can leave chemicals or metals in the water), etc.
If you are collecting snow and find it has a pinkish water melon color
(watermelon snow) stay away from it. It is caused by an algae that thrives
in a cold wet environment. There are several species of this algae but the
most common one is Chlamydomonas nivalis. While filtering will remove the
algae, it will not remove the toxins that it leaves behind. Another note
for snow is that freezing can not kill some bacteria so after the snow is melted
it should still be treated.
Hopefully this will help point you in the right direction for making your own
choices on water treatment.
Sources to recognize in no particular order