Abstract
Water in the field is not always safe to drink. We examine some of the problems that can exist, and we survey all lightweight water treatment methods for use against these problems. We also illustrate each method with at least one commercial product, but this is not meant to be a State of the Market survey of products.
- Part 1 – The first part of this series provides an overview of the threats that can exist in untreated (and in some cases treated) water sources.
- Part 2 – Remove, kill, or inactivate? Part two of this series analyzes the legal and technical definitions as well as the practical significance of water purification and filtration.
- Part 3 – A critical look at several water treatment technologies available to backpackers.
- Part 4 – Chemical water treatment methods
- Part 5 – Flitration water treatment methods
- Part 6 – UV water treatment methods
Introduction
Everyone needs to drink water when working. Yes, one can go for days (or weeks in some famous cases) without food, but after a few days without water, you die. However, not all water sources found in the wild are safe (and some at home are a bit questionable too!). So, in Part 1 of this series, we start by discussing what ‘stuff’ can be found in water sources and whether it is dangerous to you. While this will get a little technical in places, we will try to keep it comprehensible to all.
In Part 2 we will look at what you need to do (or can do) to make water safe. We will also cover the legal aspects of water treatment: what the USA Environmental Protection Agency allows vendors to claim. Since a lot of this touches on ‘public health’ issues, there are government regulations (set by the EPA) to consider. These specify how much reduction in contamination is required to meet the regulations. Honesty in advertising may not be found everywhere, but the EPA does try to help. And yes, the message here is ‘reduction’, not elimination. This will be explained. Things will get a little technical here.
In Part 3 we will survey the range of methods available for dealing with all that ‘stuff’. It will become immediately clear that no one method can handle all threats – short of osmotic filtering followed by triple distillation. We will illustrate the methods by looking at some commercial products, using them as examples. This is not a complete State of The Market Survey of products; rather it’s information about risks and ways to handle them.
It should be noted that a lot of the information available on the web and in the literature about water risks and treatment methods has been written by vendors, who have a vested interest in selling you their gear. They do sometime hype the risk and their products. That does not mean there is no problem – far from it. But there have been and still are some cowboys out there. Some of them may be in jail these days though, following EPA prosecution (yes, I know of cases).
Acknowledgements
Some illustrations in this Part 1 are from published research papers I have collected over the years; many are from the Wikipedia Commons. All are gratefully acknowledged.
Some of this material has been taken from the Australian Bushwalking FAQ web site. I own the copyright there.
The Risks – What’s in the Water?
As usual, we start with theory. It’s not that hard, so stop panicking. Broadly speaking, there are four main classes of contaminants:
- Dissolved but harmless materials like tannins and salt
- Suspended matter such as dirt, vegetable matter, clay and rock dust
- Chemicals not included above such as solvents and agri-chemicals
- Viruses, bacteria, protozoa, nematodes and the like, alias ‘bugs and wogs’
Each category requires different handling to meet the requirements of the American Environmental Protection Authority (EPA). This organisation is the largest internationally-recognised certification body for water purifiers. Please note at this point: in America the word purifier as used in the context of water treatment has a defined legal meaning. If a company tries to use the word without meeting the legal requirements, they can and have been prosecuted and potentially jailed. But there are many traps for the unwary here, and I have seen a few of them.
Dissolved but harmless materials
This category covers ‘natural’ things that are relatively harmless, assuming you exclude the third category listed above. One very common example is Tannic acid. This is the stuff that leaches out of timber and leaves and makes some streams brown. A common suggestion is that you should just warm this up, add milk and sugar, and behold: tea (or coffee). Apart from dissolving any natural fibre clothing and rotting the guts out of leather boots, tannin will do you no harm. However, too much of this sort of stuff can make the water difficult to treat for other problems.
Sometimes leaves can leach out strange vegetable oils that behave a bit like surfactants. The bubbles in the water here are not dishwashing pollution – not where that photo was taken! The water was actually very clean, with just a bit of natural leaf oils for amusement. But – you do have to know the difference!
Another common contaminant gives you ordinary salty or brackish water. This will do you no real harm either, although it may not be very useful for survival. That’s a specialised subject that we won’t go into here. One could argue that some so-called ‘sports drinks’ should also fall into this category: some of them taste pretty awful to me. Some have been linked with collapses in marathons.
Smelly or stagnant water can also fit into this category. My wife and I have drunk really smelly stagnant water bailed out of a hole dug in the ground on a couple of occasions – we were running a little close to the edge those times. I had to block my nose before I could drink it, but it was ‘safe’ to drink (we didn’t die). However, other things can make water ‘smelly’ so making such a judgment carries risks.
Suspended matter
You know that brown stuff you sometimes find floating in the water? Bits of algae and so on? In general, this stuff won’t do you much harm either (in general). Much of it can be filtered out with a handkerchief if you are worried by the appearance. We have bailed and filtered water out of many a muddy soak: despite filtration through cloth, it often remained the colour of tea. But it did us no harm, and dinner was fine. The one exception is blue-green algae: it is very toxic so leave this stuff well alone. How to tell whether something is blue-green algae is not covered here: I don’t know.
Also included in this category are things like granite dust: the stuff that makes some high mountain streams seem almost white. Now, in theory, granite dust should not harm you, although I would recommend you not to push your luck here. There are white mountain rivers in Nepal which are famous for this, and they should not be drunk. But it’s all the upstream villages that are the real danger here!
Chemicals
This category is different from the first one purely by definition. It includes all the sorts of industrial and agricultural chemicals that can do you a nasty. To be sure, normally you would not expect to meet many of them in the wild, but you sure can. Downstream from intensive agriculture is one danger zone, sadly. You only have to read the reports on the contaminants reaching coral reefs from farming use to realise the hazard. Being downstream from some mines is another hazard: old silver mines usually leach arsenic for instance. Charming – toxic and carcinogenic.
A recent hazard are the chemical used in Coal Seam Gas Fracking. They can get into the water supply and do you a lot of harm. There is a famous and viral video on the net of someone lighting the water coming out of their kitchen tap: dissolved methane!
Another set of dissolved chemicals includes chlorine and ammonia, as used by many Water Authorities to render the water supply ‘safe to drink’. It may be medically safe, but I find the smell revolting at times. So do many others, leading to thriving business in the sale of activated carbon filters for the kitchen for drinking water. These filters do reduce the amount of chlorine and ammonia in the water for a while, but please note that vendors cannot make any guarantees about how effective their filters are, or how long they will last.
The bottom line here is that water with any of these dissolved chemicals in it cannot be treated very reliably. The only safe thing to do is to seek better water elsewhere. Don’t use water draining from any of these areas. How to tell? That’s difficult, but looking upstream on your maps can help.
‘Bugs and Wogs’
Now we are getting serious (and technical). This category is the one to worry about and the one this article is mainly about. It includes several sub-categories of nasties, arranged by size:
- Viruses
- Bacteria
- Protozoa
- Nematodes, helminths & larger
Viruses
Viruses are extremely small, generally well below 0.1 um in size, down to 0.004 um. They include the rotavirus family, which includes Varicella (more commonly known as chicken pox), the polio virus, the Marburg virus and many others. The Marburg virus was first noticed in Marburg, Germany, but came to greater fame in the Congo, where in a short period it killed 128 people with a fatality rate of 83% of infections. Not pretty. Ebola hemorrhagic fever is another virus, and a pretty nasty one at that.
Not all viruses are lethal: the common cold is a rhinovirus. Actually, over 200 different viruses can give cold-like symptoms. In general you will not be in too much danger from viruses in the bush in Western countries, which is fortunate as most filters cannot reliably filter them out of the water: they are much too small. We will discuss this again later. African countries are another matter: the animal population pools and the poor standards of hygiene there can make the risks quite large.
However, being in a Western country does not mean you are risk free. Beware when downstream of any Sewerage Treatment Plant (STP). We were on a river below a large town some years ago and drank the water after careful filtration through a Katadyn filter. Little did we know! The virus load from the STP went straight through the filter. We got home that day (fortunately), but spent the next 24 hours on our backs in a very bad way. We were only semi-conscious for some of that time. Fancy that in the wild?
This particular incident was a worry as the river went straight into the Sydney water supply, which is one reason the Sydney water has to be treated with chlorine and ammonia so heavily. The ironic part is that, since the Town Council refused to clean up their STP, or couldn’t afford to (and didn’t need to for their rate-payers), the State government was forced to fund a whole new plant for them to protect Sydney. It’s called politics.
Viruses can affect most parts of your body. The diagram here illustrates how some of them affect you. It should be noted that this diagram does not cover everything: new viruses are being discovered all the time. Many unexplained aches and pains are found to be caused by new viruses.
Some filter manufacturers (eg Katadyn) claim that viruses are always attached to something larger and so can be filtered out. Well, this may work for 99% of the viruses in the water, but 1% is still quite enough to make you very seriously ill. One filter manufacturer (General Ecology) claims that their patented filter can remove viruses by an extra process: this appears to be accepted by the EPA. See Part 2 for more information.
Most viruses can be treated with heat, UV, or chemicals. I say most, not all, because there are some diabolical viruses out there that can survive in near-boiling water. They evolved in hot springs and geysers.
While perhaps not a serious concern in the USA, Europe or Australia, viruses are a real hazard when you go overseas to places like Nepal and Africa. Too often villages use the river as the sewerage disposal system: I have seen many toilet sheds sitting over the edge of the river!
Bacteria
These generally fall into the 0.4 to 1 um range. They include things like cholera, salmonella, legionnaires and of course Escherichia coli (the cause of most ‘gastro’). To a biologist and others of that ilk, they are a different sort of beastie to a virus. In fact, it is possible for a bacterium to carry a virus inside it.
The technical difference between a virus and a bacterium is interesting, and reflects a major step in the evolution of life on Earth. A virus can be nearly crystalline (which is pretty amazing in itself), but a bacterium has structure. An outer membrane typically encloses fluid with DNA swimming around inside the membrane. In effect, a bacterium is a sort of single prokaryotic (‘no nucleus’) cell. When the cell grows big enough, it splits into two identical cells in a process called fission. This is how bacteria grow and multiply inside you. Some can divide once every 10 minutes!
Many bacteria exist singly, but some can associate into bacterial mats or biofilms. Some sorts clump together when starved to make ‘fruiting bodies’, containing up to 100,000 cells. Fascinating stuff, and far more complex than I have described here.
For walkers the big risk is the E coli bacterium, illustrated here with an electron micrograph. It is commonly used as a measure of fecal contamination, which gives you a very good idea of where it comes from. In your bowels, it is fairly harmless, and almost everyone would have them there. However, if it gets into your stomach it will cause very big problems: ‘gastro’, diarrhea and dysentery, not to mention a ‘crook gut’. That it lives in your bowels causes some confusion for many.
It may surprise you to find out that there are hordes of different sorts of E coli species. Many are specific to one sort of animal: cows, etc. Some are relatively harmless; others, such as the recent O157:H7, can damage your kidneys and even be fatal. Check the numbers on that one: they give you some sort of idea of just how many different sorts there are. The same applies to most other species of bugs as well.
Another dangerous species is Salmonella. This false-colour image shows Salmonella bacteria invading human cells in the lab. These have been found on poorly prepared or handled food in supermarkets (meat, eggs, etc). They can cause diarrhea, fever, vomiting, and abdominal cramps 12 to 72 hours after infection. Most people recover, but dehydration can be a serious risk. The typhoidal form of Salmonella can lead to typhoid fever, which is a life-threatening illness. About 400 cases are reported each year in the United States, and 75% of these are acquired while out of the country. Transfer is usually by the fecal route.
Some idea of the range of problems presented by bacteria can be seen here. Yes, a bit technical, and no, you wouldn’t normally meet many of these. Fortunately! It is in fact amusing to note the Helicobacter pylori, now known to be the real cause of stomach ulcers. Once the bane of harried business men, but now easily cured with the right antibiotic.
Bacterial growth requires nutrients or food. This is obtained from your body. By itself, this is not necessarily harmful. In fact, without a healthy population of bacteria all through your body you would be dead. They protect your skin and they run your bowels. Their action is what digests the food you eat. It has been estimated that your body holds more bacteria than ‘human’ cells. The mainly American craze for sterilising everything is, in fact, potentially dangerous to your health: you need bacteria to survive. However, some bacteria can leak harmful toxins. Those bacteria are the ones we need to watch out for.
As I just mentioned, your bowels are host to a huge mass of bacteria that are vital to your continued health. However, they must stay in their right place, your bowels, and not get into your stomach. In this context, it is important to note that bacteria cannot go backwards from your bowels to your stomach: there is a valve there to block any backflow. The principle way for bacteria to get to your stomach is through your mouth, usually from your hands. Wash your hands after going to the toilet! That said, some transmission is possible through wounds and blood during accidents, which is why medics use gloves.
Some very popular camping sites on rivers have an undeserved reputation for having ‘bad water’. Curiously, people who subscribe to this idea seem happy to drink the water from the river when further downstream. I am willing to bet that much of this reputation derives entirely from the number of young inexperienced campers who have gotten sick there, and that in all cases it was really because they didn’t wash their hands after going to the toilet. I am not alone in thinking this: see for instance class="numorator">2010/05/100505113249.htm Real-World Proof of Hand Washing’s Effectiveness in Science Daily. That said, it is known that cows can carry some strains of E coli that can be quite dangerous (or fatal) to humans, so watch out in farming areas.
Bacteria can (usually) be treated by filtration, chemicals, UV light and heat.
Protozoa
Protozoa are large, typically over 6 um in size. This category includes the Cryptosporidium family and the now well-known Giardia lamblia illustrated here in delightful detail. Cryptosporidium can be widespread at a low level, even in municipal water pipes, while Giardia seem ubiquitous. I gather the Giardia cysts can be spread by the likes of foxes and possibly some native animals, but they originally come from humans – again via the fecal route.
They have a complex life cycle, cycling between an active state and an egg-like cyst. After you swallow them, they hatch out of their cysts in your stomach and attach themselves to the walls of your bowels. If you look at the previous illustration, you will see what looks like a huge sucker on the underside of the bug. It is just that, and is used to attach itself to the inside surface of your stomach or bowels. Once attached, they grow, feeding off your blood stream by sucking blood through the walls via that sucker. The photo here shows a really bad infestation of G lamblia attached to the intestines of a gerbil, feeding. The author of the photo does not record what the gerbil thought of the matter. Once adequately fed they turn into several cysts (i.e. they multiply) and pass out of you (in the usual way). If they get a chance they will float around as cysts until some other hapless soul drinks the water, then they wake up in the gut and start again. Every 12 hours they fission or divide into two. This may not sound like much, but after ten days of infection you could have a million of them growing there on your blood supply and irritating the hell out of your bowels. The loss of nutrients from your bloodstream can be serious too.
The dose quoted as being sufficient for infection is about 10 cysts. Why not just one cyst I do not know, but apparently some people can have some resistance – which can also be overwhelmed by a big enough population. The symptoms of a G lamblia infection develop slowly, taking a week and a half to two weeks to become apparent. A figure of 10 days is often quoted. If you feel sick a day or two after drinking suspect water you can be reasonably sure it is not G lamblia. It’s very likely to be E coli. In general, you won’t notice any Giardia symptoms until well after you have got home from the trip.
If you are infected you become sensitive to any fats and rumble very loudly, usually in public, and especially after eating anything fatty – like cheese. You can be infected for weeks before you wake up to the fact that something is the matter, and in that time you will be spreading a huge load of cysts for others to ingest. Not good. It seems that some people get really hung up on the whole Giardia thing: there is even a Giardia Club in America! Reality check: they sell water filters and chemicals for outdoors people. But the site has some good information.
The big worry is that it isn’t just humans who carry G lamblia: quite a few other animal populations can spread it around, including foxes and some native animals. The Whites River corridor in the Snowy Mountains in Australia, beloved of skiers in winter, was notorious for it. Personally, I put much of the blame on the pit toilet at Whites River Hut: it was so dilapidated that most people were not game to step on the floor, let alone sit on the seat, for fear it would collapse under their weight. You can work out the rest for yourself.
Giardia lamblia are not the only protozoa of concern. Cryptosporidium are small protozoa that can cause acute short-term gastro-intestinal illness with diarrhea. There are many varieties of it. I have seen claims that Cryptosporidium can be smaller than the 6 micron limit mentioned above. Cryptosporidium is the organism most commonly isolated in HIV positive patients with diarrhea. Interestingly, they are fairly resistant to chlorine, which presents a problem for the water supply authorities. Fortunately, they are quite susceptible to UV and boiling, while filtering also works due to their size.
There are many other protozoa in the world. Four general categories are illustrated here. You might now recognise the one second from the left. All can be dangerous, but there are several practical ways of dealing with them. You can boil the water, filter the water with a good EPA-rated filter or treat it with UV light. Note especially that research papers report that chlorine and some other chemicals will not work reliably on G lamblia or Cryptosporidium, no matter what the vendors claim on their packets, and it seems that even iodine is not always entirely successful against Crypto. Their hard cyst shells are a great defense against the inwards diffusion of the chemicals. However, it seems that chlorine dioxide may be effective given enough time.
Nematodes, helminths and larger
I don’t know a lot about this class, so I will include a number of quotes from Wikipedia. You can get a lot more detail there if you wish.
These are even bigger, and can be every bit as nasty as any of the above or worse. Once again, there are many different sorts, a few of which are shown here. They are not that common and can be filtered out quite easily. You will run into them overseas in the tropical and Asian areas, and in a few places in America. Some of them, quite delightfully, bore into your skin (through your feet for instance), enter your blood supply, and take up residence in an internal organ. Very charming. Ultimately I believe some of them can be fatal. On the other hand, there have been experiments using certain worms aimed at boosting a person’s immune system. Figure that one out!
These are roundworms or nematodes (even if they look like bean sprouts). They are slender worms, typically less than 2.5 mm (0.10") long.
The smallest nematodes are microscopic, while free-living species can reach as much as 50 mm (2.0") in length and some parasitic species are larger still. The ‘mouth’ is lined with cuticle, which is often strengthened with ridges or other structures, and, especially in carnivorous species, may bear a number of teeth. The mouth often includes a sharp stylet that the animal can thrust into its prey. In some species, the stylet is hollow, and can be used to suck liquids from plants or animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. The total number of nematode species has been estimated to be about 1,000,000. In general, they have tubular digestive systems with openings at both ends. Is that enough?
Common parasitic nematodes include ascarids (Ascaris), filarias, hookworms, pinworms (Enterobius) and whipworms (Trichuris trichiura). The species Trichinella spiralis, commonly known as the ‘trichina worm’, occurs in rats, pigs, and humans, and is responsible for the disease trichinosis. Baylisascaris usually infests wild animals, but can be deadly to humans, as well. Hundreds of Caenorhabditis elegans were the only known living organisms to have survived the Space Shuttle Columbia Disaster. I could go on, but I won’t.
Schistosoma, commonly known as blood-flukes and bilharzia, includes flatworms which are responsible for a highly significant parasitic infection of humans by causing the disease schistosomiasis. This is considered by the World Health Organization as the second most socioeconomically devastating parasitic disease, next only to malaria, with hundreds of millions infected worldwide. They can be quite large: in the photo here the small white bar is 0.5 mm long.
Adult worms parasitize some blood vessels. Eggs are passed through urine or feces to fresh water, where larva must pass though an intermediate snail host, before a different larval stage of the parasite emerges that can infect a new mammalian host by directly penetrating the skin. Yes, that means you don’t have to swallow them: they can burrow into your feet while you are wading. As such, I guess they may not be considered solely a hazard in drinking water.
The hookworm is a parasitic nematode that lives in the small intestine of a mammalian host – dog, cat, or human. Two species of hookworms commonly infect humans: Ancylostoma duodenale and Necator americanus. A. duodenale predominates in the Middle East, North Africa, India and (formerly) in southern Europe, while N. americanus predominates in the Americas, Sub-Saharan Africa, Southeast Asia, China, and Indonesia. Hookworms are thought to infect more than 600 million people worldwide.
The most significant risk from hookworm infection is anemia, secondary to loss of iron (and protein) in the gut. The worms suck blood voraciously and damage the mucosa – the lining of the gut. Hookworm is a leading cause of mother and child death in the developing countries of the tropics and subtropics. In susceptible children, hookworms cause intellectual, cognitive and growth retardation.
Is this the End of the Earth?
All of the above can be a bit intimidating, but it is worth remembering that many walkers never treat their water at all – and survive to a ripe old age. So to conclude this Part 1, I will briefly try to put all this in some sort of context.
For most walkers in the Western world the two biggest threats are E coli and G lamblia. The threat from E coli is ‘gastro’: stomach pains and diarrhea/dysentery. But E coli are mainly transmitted by the fecal route, and most people actually infect themselves. If you wash your hands with soap and water every time immediately after going to the toilet you will probably never encounter it. Mind you, the same could be said about behaviour at home. Giardia is not that common, except under special cases (like the Whites River case I mentioned above). With a modicum of care about where you collect your water from, you are unlikely to ever encounter it either.
An amusing side story here for your entertainment. The Thredbo ski resort in Australia was hit some years ago with an outbreak of gastro. It took some work to discover the source. The sewerage treatment plant was down-river from the village, and the water collection areas were up the valley and hillsides above the village. There was ‘no way’ there could have been any cross-infection over that distance, uphill. No way – until some realised that ducks sometimes swam in the open secondary treatment ponds before flying up the valley to the streams used as the water supply. Oops! Covers were placed over the ponds.
I started off never bothering. Then I got Giardia in Whites River during one ski touring trip, and became quite devoted to the subject of water treatment. (A very popular place for novice tourers, with an appalling and unsafe long-drop toilet which no-one used.) The treatment, one dose of Flagyl, was worse than the disease! But, after a while, I realised I was doing an awful lot of work to no real purpose, and I stopped treating our water. Instead, I paid a whole lot more attention to what water I collected, or rather, where I collected it. I focused on small side creeks with ‘clean’ headwaters instead of large rivers, and never from below any sort of human habitation. I especially like small springs where the water comes out of the ground: a built-in filtration system. I haven’t got sick since.
If you are one of the unfortunate people who have been sick from gastro, the message is clear. If you got Giardia, my sympathy (I have had it too), but please remember that your case is one experience out of tens or hundreds of thousands of nights of bug-free camping. If you have to use suspect water sources, then some sort of treatment might be smart.
In Part 2 we will look at what you need to do if you want to treat your water, and at what the EPA regulations have to say on the matter. I will say here that you do not have to achieve a 100% elimination of all bugs and wogs; all you have to do is to get their concentration down to a level your body can handle.
In Part 3 we will look at treatment methods (at last), and illustrate these methods with actual commercial gear. This will not be a comprehensive survey of every brand and model on the market: we are concentrating on the different methods.