Water Science

Treating Water

As long as you stay away from water in populated areas, the main concern in The Pacific Northwest is Giardia and Cryptosporidium.  Cryptosporidium is more of a concern in coastal lakes and streams.  Giardia can be found in many water sources. Cryptosporidium is more difficult to neutralize and can cause more severe problems so the focus is generally on treating water for Cryptosporidium.

What Works

• Water filtration with a quality filter (Katadyn, MSR, Platypus, Sawyer)

  • Absolute pore size of 0.2 microns will filter out all harmful protozoa (Giardia and Cryptosporidium) and bacteria, but not viruses

• Chlorine Dioxide mostly works

  • Effective against bacteria and Giardia

  • Not as effective against Cryptosporidium and requires 4 hours of contact time

• Boiling

  • Neutralizes all protozoa (Giardia and Cryptosporidium), harmful bacteria and viruses

• UV Light

  • Effective against harmful protozoa (Giardia and Cryptosporidium), bacteria and viruses

What Doesn't Work

• Iodine

  • NOT effective against Giardia or Cryptosporidium

• Chlorine (bleach)

  • NOT effective against Giardia or Cryptosporidium

Note sure about what to get?  Talk to our Scoutmaster or Troop Medic.

Why Purify Water

There was several pathogens and contaminants that are of concern.

• Protozoa

  • Giardia lamblia

  • Cryptosporidium parvum

• Bacteria

  • Escherichia coli (E. coli)

  • Salmonella

  • Campylobacter

• Viruses

  • Hepatitis A

  • Rotavirus

  • Norovirus

• Toxins

  • Petroleum products

  • Fertilizer runoff

• Taste

All of these will make you really sick. 

In the PNW (as well as the US, Canada and the world in general), Giardia lamblia is the most common pathogen reported.  That said, Cryptosporidium is also commonly found in the US and is much more difficult to neutralize.  Cryptosporidium is also more pathogenic and can result in death, particularity in immunocompromised individuals. Because of this, focus is generally on treating water for Cryptosporidium.  

Cryptosporidium is

• Found in coastal lakes and streams in Olympic peninsula

• Livestock, especially cattle, are a significant source

  • Found downstream from livestock

• Associated with the use of a community aquatic centers

  • Australian study found notable increase in surface waters that allowed recreational activities

• Waterfowl carry infectious Cryptosporidium oocysts from habitat to habitat

• Associated with contamination of the source waters with sewage - yum

Other protozoa can be found in water but are MUCH less of a concern compared to Giardia lamblia and Cryptosporidium parvum.  These include Toxoplasma gondii, Cyclospora cayetanensis, Entamoeba histolytica, and Blastocystis hominis.  It is assumed that if water is treated sufficiently for Giardia lamblia and Cryptosporidium parvum that other enteric protozoa will also be controlled.

Water Purification

There are several ways to purify water.

• Heat

  • Boiling

  • Solar Pasteurization

  • Distillation

• Chemical

  • Halogens

    • Iodine

      • Iodine solution

      • tablets

      • crystals

    • Chlorine

      • Bleach

  • Chlorine Dioxide

  • Sodium Dichloroisocyanurate (NaDCC)

• Water filtration

• Ultraviolet (UV) Light

Heat

Usually not a first like method for treatment of water for backpackers, but is a useful backup method to have.

Boiling

• Low Tech method of purification 

• Boiling kills ALL pathogens big and small

• Requires fuel or electricity

• Not ideal in areas where fuel is limited

Heat Pasteurization

• Heating water to 72°C (162°F) and allowing to sit for a while (5-minutes) is enough to pasteurize water

• Pasteurization uses about half as much fuel as boiling

• WAPI can be used to confirm pasteurization

• NSD Superwapi is a little bit lighter if you can find one

• 162°F water if fine for Hot Drinks and Freeze Dried Meals, but NOT Dehydrated Meals

Solar Pasteurization

Used in areas with lots of sunlight.  Sustainable way to purify water if in a static location.  Not practical for backpacking as it takes all day and often uses a metal roof or solar oven to work.  Obviously, not effective in certain parts of PNW during certain times of the year.

Distillation

Excellent at separating water from pathogens, minerals, salts and many other contaminants.  Requires a certain amount of supplies and know-how.

Halogens (chlorine and iodine)

Effective against Viruses and Bactria.  Super easy and light weight.

Do NOT use iodine if pregnant or have thyroid disorder.

NOT reliable against Protozoa such as:

• Giardia lamblia

• Cryptosporidium parvum

Iodine Products

• Potable Aqua Iodine Tablets

• Potable Aqua Iodine and PA+ Plus Tablets

• Polar Pure Iodine Crystals

Chlorine Products

• Bleach

Chlorine Dioxide

Effective against Viruses and Bactria.

• Highly effective against Viruses and Bactria

• High effectiveness against Giardia

• Low to moderate effectiveness against Crypto

• • requires 4 hours of contact time for Crypto!

Chlorine Dioxide Products

• Potable Aqua CIO2 Tablets

• Katdyn Micropur Tablets

• Aquamira CIO2 Liquid

Sodium Dichloroisocyanurate (NaDCC)

• • Effective against Entamoeba histolytica (E. histolytica), Giardia lamblia (G. lamblia)

  • Less effective against Cryptosporidium, Cyclospora and Microsporidia

Filtration

Filters are rated by pore size, and there is more than one way to measure the pore size.  The absolute 1 micron filter will more consistently remove Cryptosporidium than a nominal filter.  Some nominal 1 micron filters will allow 20% to 30% of 1 micron particles (like Cryptosporidium) to pass through.  For bacteria and viruses, you'll needs a filter with a much smaller pore size.  (Source: CDC)

Filter Certification

Please note that: NOT all Filters are Created Equal.  Filter testing and certification lets a manufacture know how effective their filter is.  The CDC recommends looking at the certification for a filter. 

• NSF Protocol P231: Microbiological Water Purifiers

  • Filters used for outdoor use should meet this standard

  • Overview: Protocol P231 addresses systems that use chemical, mechanical, and/or physical technologies to filter and treat waters of unknown microbiological quality, but that are presumed to be potable. 

  • Standard measures removal of bacteria, viruses, and cysts.

  • A quality filter should pass the 11 day test of Type I General Test Water (contaminated tap water) and Type III Challenge Test Water (filthy, cold "wilderness" water) 

  • Please note that not every manufacture tests the full protocol

    • The full test protocol for P231 lasts 10-11 days

    • You can test a liter of Type 1 water and state you passed this protocol, as manufactures have in the past

• NSF Protocol P248: Military Operations Microbiological Water Purifiers

  • Similar to P231 with testing of removal of microorganisms in Type III Water

  • Simulates how purifier is used in military conditions

  • Passing this test suggests purifier is effective for outdoor use

• NSF 42: Aesthetic Effects 

  • Removal of tastes such as chlorine, odors, colors or particulates from tap water

  • This standard is NOT suitable for filtration of water in the outdoors

• NSF 53: Health Effects 

  • Removal of chemicals from tap water

  • This standard is NOT suitable for filtration of water in the outdoors

Pore Size

Absolute Pore Size:

• 99.9% of the particles larger than a specified micron rating will be trapped on or within the filter

• This is the Pore Size you are looking for

Nominal Pore Size:

• Filter Rating indicating the approximate size particle

• Generally interpreted as meaning that 85% of the particles larger than a specified micron rating will be trapped on or within the filter

• This is NOT the pore size you are looking for - it is misleading 

Mean Pore Size:

• Filter Rating indicating the approximate size particle

• Some pores are larger and some or smaller

• This is NOT the pore size you are looking for - it is misleading 

Organisms of Concern:

• Protozoa

  • 1-15 microns

  • Cryptosporidium

  • Giardia

• Bacteria

  • 0.2-5 microns

  • Need a Microfilter or better

  • Campylobacter

  • Salmonella

  • Shigella

  • E. coli

• Viruses

  • 0.02-0.3 microns

  • Filters are usually ineffective against viruses

  • Rarely found in US waters

  • Sometimes found in developing countries

  • Enteric

  • Hepatitis A

  • Norovirus

  • Rotavirus

Look for an Absolute Pore Size

• Basic Filtration

  • Absolute pore size of 1 micron or smaller for Protozoa like Crypto or other pathogens

  • high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia)

  • NOT effective in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli)

  • NOT effective in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus)

• Micofiltration

  • Absolute pore size of approximately 0.1 micron

  • very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia)

  • moderate effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli)

  • NOT effective in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus)

• Ultrafiltration

  • Absolute pore size of approximately 0.01 micron

  • very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia)

  • very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli)

  • moderate effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus)

  • low effectiveness in removing chemicals

• Nanofiltration

  • Absolute pore size of approximately 0.001 micron

  • very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia)

  • very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli)

  • very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus)

  • moderate effectiveness in removing chemicals.

Note: Most home water filters are NOT designed to filter out bacteria or other pathogens.  The following labels found on filters may NOT be designed to filter out Crypto:

• Nominal pore size of 1 micron or smaller

• One micron filter

• Effective against Giardia

• Effective against parasites

• Carbon filter

• Water purifier

• EPA approved (Caution: EPA does not approve or test filters)

• EPA registered (Caution: EPA does not register filters based on their ability to remove Cryptosporidium)

• Activated carbon

• Removes chlorine

• Ultraviolet light

• Pentiodide resins

• Water softener

• Chlorinated

Note: the following were listed in 2022.  Technology changes.  Information given as rough idea of what's out there based on information available at time of publication. 

Filter Types

• Hollow Fiber

  • Bundle of tiny straws

  • Very High flow rates

  • Damaged if frozen

  • Damaged if dropped

  • Avoid use in subfreezing environments

• Ceramic

  • Maze of microscopic holes

  • Slower flow rates

  • Heavy clogging can be treated with scrubbing

• Activated Carbon

  • Works by attracting contaminants so they become stuck

  • Loses effectiveness with high flow rates and with high contamination

  • Does NOT reliably filter out pathogens

  • May filter out some contaminants

• Other Types

  • Ability to filter may vary

  • Grayl GeoPress Purifier uses non-woven ceramic fibers

    • "The non-woven substrate for our technology has an effective pore size of about 1micron. But the technology doesn't rely on pore size (size exclusion). Instead, powerful electroadhesion holds onto pathogens - virus, bacteria and protozoa. And Activated Carbon removes chemicals and heavy metals."

    • Pore size of about 1 micron raises concerns

  • Katadyn Hiker Microfilter uses Pleated Glass Fiber w/ Activated Carbon Core

Gravity Water Filters

• Lets gravity do the work

• Requires wait time

• Platypus GravityWorks

  • Good group kit, especially for canoe or car camping

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 1.5L/minute

  • Filter media: Hollow Fiber

• MSR AutoFlow XL Gravity Filter

  • Relatively lightweight group setup

  • 10L of capacity!

  • Does not come with clean bag

  • Setup for Nalgene bottle - great if that is what you use

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 1.75L/minute

  • Filter media: Hollow Fiber

• Guardian Gravity Purifier

  • Filter Pore Size: 0.02 Microns

  • Filtration rate: 0.5L/minute

  • Filter media: Advanced Hollow Fiber

• Sawyer Gravity Filter

  • Filter Pore Size: 0.1 Microns Absolute

  • Filtration rate: <0.5L/minute

  • Filter media: Hollow Fiber

  • Note: flow is even slower through the Micro Squeeze Filter (in case you are looking to save weight)

• MSR Thru-Link Inline Water Filter

  • Filter only (bag and line not included)

  • Fantastic if you have a water reservoir

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 1.5L/minute

  • Filter media: Hollow Fiber

Bottle Filter

• Mounts on Bottle or has built in bottle

• Platypus QuickDraw Microfilter System

  • Difficult to use if running

  • Can't be used as an inline filter

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 3L/minute

  • Filter media: Hollow Fiber

• Katadyn BeFree Collapsible Bottle

  • Great lightweight setup

  • Short lifespan

  • Does NOT fit standard sized bottles

  • Filter Pore Size: 0.1 Microns

  • Filtration rate: 2L/minute

  • Filter media: Hollow Fiber

• LifeStraw Peak Squeeze

  • Similar to Sawyer but heavier and even shorter lifespan

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 3L/minute

  • Filter media: Hollow Fiber

• Sawyer Mini Filter

  • Doesn't perform as well as Sawyer Squeeze Water Filter

    • SLOW flow

  • Filter Pore Size: 0.1 Microns

  • Filtration rate: Extremely LOW

  • Filter media: Hollow Fiber

• Grayl 24oz GeoPress Purifier

  • French-press-style plunger

  • Lifespan of only 65 gallons

  • Not practical for extended trips

    • only treat 24 oz at a time

  • Nontraditional

    • "The non-woven substrate for our technology has an effective pore size of about 1micron. But the technology doesn't rely on pore size (size exclusion). Instead, powerful electroadhesion holds onto pathogens - virus, bacteria and protozoa. And Activated Carbon removes chemicals and heavy metals."

    • Pore size of about 1 micron raises concerns

  • Filter Pore Size: ??? Microns

  • Filtration rate: 5L/minute press action

  • Filter media: non-woven ceramic fibers

• LifeStraw Go

  • Relatively long filter life

  • Heavy and bulky for backpacking

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: ???L/minute

  • Filter media: Activated carbon filter

Squeeze Water Filters

• Ultralight

• Sawyer Squeeze Water Filter

  • Favorite UL and economy option

    • "Mini” and “Micro” versions will reduce weight but have painfully slow flow rates

  • Bags are not great

    • Consider replacing with Smartwater bottle or longer-lasting Evernew or CNOC reservoir

  • Filter Pore Size: 0.1 Microns

  • Filtration rate: 1.4L/minute

  • Filter media: Hollow Fiber

Pump Water Filters

• MSR Guardian Purifier System

  • Overkill

  • Expensive

  • Filter Pore Size: 0.02 Microns

  • Filtration rate: 2.5L/minute

  • Filter media: Advanced Hollow Fiber

• Katadyn Hiker Microfilter

  • Short filter life

  • Expensive replacement filter

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 1L/minute

  • Filter media: Pleated Glass Fiber w/ Activated Carbon Core

• MSR MiniWorks EX Microfilter

  • Ceramic!

    • Not as delicate as hollow fiber

    • Heavier

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 1L/minute

  • Filter media: Ceramic

• Katadyn Pocket Water Filter

  • Expensive

  • Expedition/Guide quality

  • Ceramic!

    • Not as delicate as hollow fiber

    • Heavier

  • Filter Pore Size: 0.2 Microns

  • Filtration rate: 1L/minute

  • Filter media: Ceramic

Ultraviolet (UV) Light

• Effective against viruses, bacteria and protozoa

• Not for cloudy water

• Requires electricity

• Don't drop bulb on rock

• Don't look at pretty light through the opening in top of bottle - UV will damage eyes (glass, PET and Metal will stop it)

• Read the instructions and stir pen in water

Timmermann LF, Ritter K, Hillebrandt D, Küpper T. Drinking water treatment with ultraviolet light for travelers -- Evaluation of a mobile lightweight system. Travel Med Infect Dis. 2015 Nov-Dec;13(6):466-74. doi: 10.1016/j.tmaid.2015.10.005. Epub 2015 Nov 6. PMID: 26616307.