Water Purification: The 5 Contaminants You Need to Know About

by Paul Kirtley

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Fresh Water Stream

Is this water safe to drink? Photo: Paul Kirtley.

We can’t tell whether fresh water it is safe to drink by looking at it. Unless, for example, the water is obviously stagnant, dirty or oily we cannot visually determine the presence of some of the potential contaminants. Even if the water looks clean, it may be contaminated.

Over the years while leading people in the outdoors and teaching courses in wilderness skills, I’ve found that most uncertainty about how to treat water comes from a lack of clarity over what the problems might be. This is due, at least in part, to the marketing surrounding the many water-purification products aimed at the outdoors user.

The better your understanding of the potential contaminants, the better equipped you will be in determining the solution. Don’t be baffled by scientific terminology or over-technical marketing hype.

There are five categories of contaminants you may need to eliminate from fresh water to make it safe to drink:

  • Turbidity
  • Parasites
  • Bacteria
  • Viruses
  • Chemical pollutants

Wilderness Water Purification: Useful Detail

Turbidity: Turbid water is muddy, thick or cloudy. This can be due to sand, mud, silt or other suspended particulate matter such as decomposing organic material. Removal of turbidity is important. Even if there are no waterborne diseases present, turbid water can irritate your digestive system. In addition, turbidity can reduce the effectiveness of chemical treatments.

Parasites are organisms that live in or on another organism, benefiting at the expense of the other. Waterborne parasites can be either multi-cellular organisms such as worms or simple, single-cell organisms such as protozoa.

Protozoa are colourless microbial organisms, capable of motion. They obtain food by ingesting other organisms or organic particles. Protozoa lack the cell walls of algae and fungi and in this respect resemble animal cells. Many protozoa are free-living microorganisms, but several cause disease in humans and other animals. Protozoa are typically 0.01-0.05mm in diameter. Examples include Cryptosporidium and Giardia.

Giardia Lamblia Protozoan

Digitally coloured scanning electron micrograph (SEM) depicting the upper surface of a Giardia protozoan. Source: CDC (via Wikipedia)

 

Bacteria are a large group of single-cell organisms, some of which cause disease, between them producing a wide range of infections, some of them potentially lethal. Bacteria are widely distributed in soil, water, air, and on, or in, the tissues of plants or animals. Bacteria were first observed in the 17th century and first definitely implicated in a disease (anthrax) in 1876. Typically a few micrometers across (micrometer or ‘micron’ is one millionth of a metre), bacteria are much smaller than protozoa. Examples of diseases caused by bacteria include Typhoid fever.

Escherichia Coli

Scanning electron micrograph of Escherichia coli. Source: Rocky Mountain Laboratories, NIAID, NIH (via Wikipedia).

 

Viruses are not cells. Viruses lack many of the attributes of cells. A single virus particle is a static structure, quite stable, and unable to change or replace its parts. Only when it is associated with a cell does a virus acquire a key attribute of a living system, reproduction. Many viruses cause disease in the organisms they infect. While protozoa are measured in terms of thousandths of a metre and bacteria are measured in millions of a metre, viruses are measured in terms of billions of a metre (nano). Many causes of ‘traveller’s diarrhoea’ are considered the result of infection by waterborne viruses. More serious diseases such as Hepatitis A and Polio have long been known to result from faecal contamination of water.

Hepatitis A virus prevalence in 2005

Hepatitis A - Map of Prevalence. Source: CDC.

 

Chemical pollutants can range from pesticides to heavy metals. Chemical pollution in wilderness areas and national parks are often associated with nearby mining, forestry and agriculture.

Other Terminology

A pathogenic organism is any organism that causes disease. That is, as far as waterborne disease is concerned, could be protozoa, bacteria or virus.

Some microorganisms (such as Giardia lamblia) can form cysts, which allow the organism to live without food, water or oxygen for a period of time. The cyst protects the organism from harsh conditions, allowing it to be much more resistant to drying, heat, chemicals, mechanical disturbance such as crushing or vibration, UV and ionizing radiation than the unprotected organism. For parasitic species, the cyst will also enable it to survive outside of the host.

Graphic showing the life cycle of Giardia

The life cycle of Giardia. Source: CDC.

Use Common Sense And Research

In a wilderness or remote travel situation, it is unusual to have to deal with all five types of contaminant at the same time. Use common sense and research to find out what you are likely to be facing.

We can see turbidity and it can be removed with coarse filtration.

Dead fish and vegetation are clear signs of serious chemical pollution. Chemical pollution is often less extreme than this, however, and the signs much more subtle. With a little bit of pre-trip research we can judge if we are visiting an area where chemical pollutants may be an issue (for example will you be near sulphide mining, or is there a lot of agriculture up river?).

The presence of waterborne pathogens is often associated with the presence of humans and domesticated animals (and their excreta contaminating the water). In many places where there has been little or no human activity and no livestock or pack animals, then the water can be free of pathogenic organisms and safe to drink. But remember we can’t know for sure without testing the water.

Even if the locals drink the water, remember that they may well have been doing it for years and have an acquired immunity to pathogenic organisms we may never have encountered before.

Pre-trip research will also help you determine which waterborne pathogens are possible, likely or endemic in the country you are travelling through. This type of research can easily be combined with determining which inoculations, if any, you require before a trip.

How To Deal With Water Contaminants

There are methods of dealing with each of turbidity, parasites, bacteria, viruses and chemical pollutants.

No single method, however, will provide satisfactory treatment for all of these contaminants. Further, there are many water purification products on the market which make use of some of these methods. This proliferation of products along with marketing tends to create some confusion amongst potential users as to which method is “best”. The best solution depends on the circumstances.

In future articles I will look at the various methods in more detail, including pros and cons and tips for application.

Author using water purification pump

The author using a water purification pump that combines filtration and chemical treatment. Photo: Amanda Quaine.

Here, I’ve gone back to first principles.

To keep things as clear as possible, the important points you need to remember are as follows:

  • Coarse filtration will remove turbidity;
  • Microfiltration will remove the larger pathogenic organisms (protozoa and some bacteria);
  • Boiling will kill all pathogenic organisms (at any altitude);
  • Certain types of filtration (activated carbon) can remove some chemical pollutants;
  • Some chemical treatments (chlorine, iodine) will kill many pathogenic organisms (in particular bacteria and viruses), while other treatments (chlorine dioxide) will deactivate all of them.

Hence, you will be able to deduce that a combination of filtration and a suitable chemical treatment or boiling will deal with any or all of the specific contaminants. If you understand these fundamental principles, then you can start to make an informed judgement, free from the influence of marketing, and adopt a solution that best fits the circumstances. The details and pros and cons of various methods will be covered in future articles.

Recommended Books For Further Reading:

 

 

 

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Paul Kirtley is an award-winning professional bushcraft instructor. He is passionate about nature and wilderness travel. In addition to writing this blog Paul owns and runs Frontier Bushcraft, a wilderness bushcraft school, offering bushcraft courses and wilderness expeditions.

 

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{ 17 comments… read them below or add one }

Jeroen

Once again an interesting article, thanks!

In most “survival shows” they just boil the water to make it safe to drink, but I never quite understood when one knows for sure if boiled water is safe to drink (short of obvious chemical sings).

So for your next article, I’d like to know which possible contaminations boiling water will remove. I’m also interested to know if distilling water is always safe. I’ve read somewhere that drinking too much distilled water can actually be harmful. Is this true?

Anyway, looking forward to the follow-up article.

All the best,
Jeroen

Reply

Chris Leeland

Yes – well written and informative as always.

When you do the section on boiling would it be possible to include a little on the ‘Water pasteurisation Indicator':

http://www.solarcookers.org/catalog/waterpasteurizationindicatorwapi-p-76.html?osCsid=d5a99bf3f5ae71f339a905e68df85e2b

This was originally solely for solar cooking but it now has a metal wire insted of nylon fishing line so it might be of interest to those (not me!) who cook at high altitudes (for example)

Reply

Paul Kirtley

Hi Chris

Thanks for your comment.

Re the WAPI, I really don’t think you need it if you are boiling the water. At the highest point on Earth, water will boil at 71 degrees Celsius. So, wherever you are, if water is boiling it is always an indicator that you have risen above the necessary temperature to kill pathogenic organisms. Then it is just a question of how long you boil it to make it safe…

All the best

PAul

Reply

Paul Kirtley

Hey Jeroen

Glad you found the article useful. I will be covering boiling in a future article and will certainly address the points you make in your comment.

Regarding distilled water – you won’t be able to distil water to the level of laboratory distilled water with basic camping equipment, so I don’t think it is an issue you need to worry about.

All the best

Paul

Reply

Steve Bayley

There is plenty of ignorance and confusion amongst the outdoor community around this subject and definitive factual discussions such as this are very helpful. Once we can understand the scope of a problem it becomes easier to understand how to best to respond. I’m looking forward to the follow up article on how to deal with the contaminants you’ve identified Paul. I’ve been intrigued by the more recent developments in portable water treatment devices which use UV light to destroy pathogens, or at least to mitigate their harmful effects, and wonder if you’ll be able to assess these in the next article alongside the more traditional methods.

Reply

Paul Kirtley

Hi Steve

Thanks for the comment. I will touch on UV light although personally I don’t favour it because it either depends on batteries or moving parts. Also, one of the issues is it requires clear water to work properly.

All the best

Paul

Reply

Rody Klop

Chlorine desinfection does not work effective for cryptosporidium (3-6 micon), giarda (4-15 micron) and some ecoli type bacteria (some became recently resistent). Besides Active Carbon (mostly made of coconutshells) a new type has become available named Nano Carbon (NMC).

I am studying waterfilters for almost 2 years now and the information about waterfiltration devices is very hard to find. (the real important info!).

Reply

Paul Kirtley

Hey Rody

Yes, halide disinfection is not effective against Cryptosporidium cysts, in particular. I’ll expand on this in future articles.

Agreed! – It is not easy to find good (and consistent) information on water filters.

All the best

Paul

Reply

Dean Read

Paul
Another great article, I really look forward to receiving your invite to view e-mails.
Valuable and important information that I know I can rely on.
Kindest regards
Dean

Reply

Paul Kirtley

Hi Dean

It’s been a while. Nice to hear from you.

Thanks for your comment and letting me know you are finding this material useful.

All the best

Paul.

Reply

Phil

Looking forward to catching up with you this weekend, I understand that this topic is on the agenda. I’m going to bring my purification kit with me, and welcome your thoughts. I think it’s true that marketing can cloud peoples judgements of what is useful and effective.

Cheers

Phil

Reply

Paul Kirtley

Hi Phil

Yes, it’ll be good to see you this weekend. Looking forward to it!

We can talk water and fire and anything else people are interested in :)

Cheers,

Paul

Reply

Survival Topics

It has been proven many times over that anywhere on earth, even on Mount Everest, once water reaches the boiling point ALL disease causing organisms have either been destroyed or rendered inert.- the water is hot enough. No need to boil for even 5 seconds.

Actually, even before the boiling point has been reached the water is safe to drink- but we typically let it start bubbling as proof it is hot enough (since we likely do not have a thermometer).

However, chemical contamination is generally not solved by heating water. That requires filters and other techniques.

Reply

Paul Kirtley

Yep, all of that is covered in the article.

Specifically, the penultimate paragraph states:

* Coarse filtration will remove turbidity;
* Microfiltration will remove the larger pathogenic organisms (protozoa and some bacteria);
* Boiling will kill all pathogenic organisms (at any altitude);
* Certain types of filtration (activated carbon) can remove some chemical pollutants;
* Some chemical treatments (chlorine, iodine) will kill many pathogenic organisms (in particular bacteria and viruses), while other treatments (chlorine dioxide) will deactivate all of them.

So, I’m not quite sure what your point is: Are you suggesting that the only technique you ever have to employ is boiling?

All the best,

Paul

Reply

Kropotkin

Chlorine dioxide looks most effective against biologicals,
turbidity still needs to be reduced beforehand to ensure effective dose.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA453968

Reply

Paul Kirtley

Agreed.

Reply

WillSkillDude

Nice article.
Must admit I have never heard of ‘Turbid water’…! You learn something every day eh.
You also cover each point very well which makes it very interesting.
Looking forward to reading more in your future articles.

Reply

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