Water purification for expeditions
Purifying water whilst on expeditions prevents illness and picking the most suitable system for the environment you are going to is important. In the UK drinking straight from streams can cause illness but from high mountain streams in the least visited areas it is unlikely and I do this all the time, however as the mountains become busier and at lower, more visited elevations the risk of getting ill increases. When on expedition in Low to Middle-Income countries tap water is commonly non-potable, and even not safe for teeth brushing and washing fruit and salads. By having a water purification method which is suitable for tap water as well as mountain streams means that buying bottled water is reduced or no longer required which has the benefit of reducing environmental impact. In this article on water purification for expeditions, I'll detail different systems for safe drinking water and the pros and cons of each.
What makes you ill?
There are three types of waterborne microbes which can cause illness; Bacteria (such as E.Coli, Salmonella, Cholera), Viruses (like Hepatitis and Norovirus) and Protozoa, also known as cysts, (such as Giardia).
In addition, sediment and particulates in the water, could cause stomach irritation but the main problem is that it will reduce the effectiveness of any water purification method.
Filtering, and why it isn’t my preferred method
Most people I speak to about water purification immediately think that a filter system is the best, but these are the reasons it may not be. Firstly, most water filters don’t remove viruses such as Hepatitis A and E and Norovirus, this is because viruses are very small and aren’t most filters don’t have pores small enough to removed them. For viruses which affect humans to occur in water an infect person’s faecal matter has to get in the stream. This is very unlikely in mountain streams in High-Income nations, but becomes more likely on expedition in Low to Middle-Income nations.
There are a handful of water filters which filter out viruses but due to needing to force the water through microscopic pores filtration takes more physical effort and the filter requires more regular cleaning both of which are inconvenient.
The only occasion I’ve felt the need to use a filter has been when camping on or immediately downstream of a glacier and needing to use glacial melt water. The fine sediment in the melt water known as ‘glacial flour’ which makes the water look cloudy can irritate the stomach and reduce the effectiveness of the purification method. On all other occasions I have found clear water free of sediment and particulates. A very simple and lightweight solution I have sometimes taken to filter water before purifing is a Milbank Bag.
Some other considerations for choosing a filter, apart from what it filters out, are the following:
Is it gravity fed, pump or drink from bottle? If it requires pumping it will require your time time and effort.
What is the flow rate? How quick will you be able to get a litre of water?
Does it require a specific bottle?
Pros
Removes sediment and particulates.
No bad taste or chemicals used.
Can easily sterilise small quantities of water such as one glass.
Unlikely to need to change the filter on an expedition so good for longer trips.
Big price range but some are quite affordable
Milbank Bag ~£16
Sawyer Mini System or Life Straw (doesn’t remove viruses) ~£30
Grayl Geopress filter (removes viruses) ~£100
MSR Guardian (removes viruses) ~ £270
Cons
Most filters do not remove viruses.
Filters which do remove viruses require regular cleaning and a degree of physical effort to use.
Many are bulky and/or heavy compared to alternatives.
Some need a specific bottle.
Most require regular cleaning.
Freeze readily in low temperatures making them ineffective or breaking them.
Pump filtration or gravity filter can be time consuming to get filtered water.
Filtration technology is always changing so keep a look out for new filters on the market, just make sure you know what they are and aren’t able to filter out and their limitations.
Boiling
Boiling water is the most widely used way to kill all waterborne microbes. When camping a stove used for cooking can also be used to boil water. Outdoor enthusiasts often talk about letting the water boil as a 'rolling boil' for 2 minutes, or sometimes more. Actually, even the nastiest microbes are killed at 70ºC, it's just it's hard to tell when water reaches this temperature and it is reached evenly. So, to be on the safe side, let the water come to a proper boil, so that large bubbles are rolling over each other, and at sea-level to 2000m do this for 1 minutes, any more is wasting fuel.
Using boiling as a method to treat water is great news for tea and coffee drinkers, but if you're not a fan try herbal teas, hot water and lemon, hot chocolate and hot squash as other options. Personally, I love peppermint tea because is tastes good hot or cold and you can also brush your teeth with it as it still tastes fine.
Pros
Kills all waterborne microbes
When camping a stove is usually carried which can be used to boil water
In most places and cultures it's possible to order a hot drink, and in self-catering or hostel accommodation, there is access to a stove or kettle.
Cons
It's not always convenient to boil water.
Fuel for a camping stove is both heavy, bulky and costly. You might not want to use it to purify all your water.
If you don't want a hot drink, cooled water often tastes strange, and takes a considerable time to cool.
SteriPEN Freedom
SteriPEN products are neat little gadgets which use UV light to alter the DNA of microbes, making them unable to cause illness. It's not new technology, many households on a private water supply in the UK use this, it's just that SteriPEN have made it hand-held.
SteriPEN have several different designs of essentially the same product but I like the rechargeable SteriPEN Freedom which comes with a solar panel. Depending on the trip I may or may not take the solar panel. If I do want to recharge via solar I often use a separate, more versatile, solar panel I have, rather than the one the SteriPEN comes with. I can also charge the SteriPEN Freedom from the mains via a USB cable and plug. On short trips, charging before I go is all I need.
To use the SteriPEN Freedom immerse the UV bulb fully into the water. It automatically turns on. Stir until the red light turns to green after 48 seconds or so, for a ½ litre, and then it's done.
After using this system on several trips I have found that it works best shared between no more than four people, with bigger groups it feels like it takes forever to get everyone's water purified and also requires charging frequently (every couple of days).
Pros
No bad taste.
No chemicals used.
Can easily sterilise small quantities of water such as one glass.
Good for long-term travel as, if charged, can purify 20 litres per charge (although in testing I found it to sometimes be less) and 4,000 litres of water for the life time of the lamp.
If the lamp comes to the end of its life span SteriPEN will replace your SteriPEN for free.
Can't 'over' treat.
Cons
Can't purify bottles larger than 1 litre.
Requires the battery to be sufficiently charged.
The Freedom is designed to work with ½ litre bottles. A double treatment (i.e. double the time) is required for 1 litre bottles.
Although it treats water the fastest for the all the methods here it does require 50 seconds of stirring (~1 min 30 seconds for 1 litre). This doesn't sound like long but putting a couple of drops or tablets in the water and leaving it for a bit is easier.
Can be tedious waiting for water to be purified, especially if doing several 1 litre bottles at a time.
It is possible to break the lamp (it's made of glass) or for the SteriPEN to malfunction in other ways.
Bacteria can 're-activate' if water is exposed to sunlight.
A bottle with a wide enough neck for the filament to fit in is required (the Freedom comes with a bottle). A standard plastic water bottle has too narrow a neck.
The light on the Freedom is hard to see in bright sunlight so difficult to work out when the treatment is done.
Intial cost is expensive but if used a lot cost per use low. Price £75-£100
Chlorine or Chlorine Dioxide tablets
Chlorine and chlorine dioxide is extremely safe, if you use mains tap water in the UK then you use chlorine. Both can be bought in tablet form which are compact and lightweight. In fact, I always carry a packet of ten tablets in my first aid kit so I know that I always have some on me. One tablet generally treats 1 litre of water and you must wait 10 minutes for the tablet to take effect.
Chlorine is less effective than chlorine dioxide, not being able to treat protazoa like Giardia, it also has the disadvantage that it can can leave the treated water tasting a little like a 'swimming pool'. However, it is cheaper.
Most people get used to the taste of chlorine but some people really dislike it and it can discourage people, especially younger people, from rehydrating properly. I find a few things help. It is possible to buy neutralising tablets which remove the taste. Using cordials or flavoured drinks powders can mask the taste. Also, leaving the treated water to stand with the lid off allows the chlorine to evaporate off once it has done its work.
Pros
Can be added to any shaped bottle or water container.
Can leave the treatment to work therefore less time consuming.
Can be made up into a stronger solution for treating particularly suspect water or for washing fruit and veg.
Very lightweight to carry in small quantities.
Impossible to break or spill, unlike a filter, SteriPEN or Aquaprove.
Cheap (£4 for 200 litres)
Cons
Can't easily purify less than a litre of water, but can purify much larger quantities.
Need to wait 10 minutes until the water can be drunk.
Need to estimate how many tablets you need for any trip and buy in advance.
Some people don't like the taste, which could result in them not hydrating properly.
Cold water takes longer to purify.
Chlorine has a limited effectiveness against protozoa such as Giardia. Chlorine Dioxide, however, does kill protozoa including Giardia which is a major advantage and worth the extra money.
Aquaprove (Chlorine Dioxide solution)
Aquaprove is one of my new favourite ways to sterilise water. This simple system uses the advantages of a Chlorine Dioxide treatment but is faster acting than tablets and has the ability to purify small quantities whilst not having a chlorine taste.
The treatment is bought as a tablet with a small plastic bottle. When you need to treat drinking water simply take the tablet out of its packaging, put it in the 50ml bottle, add tap water and wait for 10 minutes. Now the Aquaprove is in a concentrate Chlorine Dioxide solution form and can be used to treat water.
The concentrated solution can be added to the water requiring treatment taking just 5 minutes to work. Four drops purifies 1 litre which means that it is easy to purify smaller quantities, such as a single glass of water. Each bottle can treat up to 250 litres of water.
Once the solution has been made up by dissolving the tablet in the bottle it is only effective for 40 days, hence why you only make it up when you need it, rather than it being purchased as a solution. I recommend writing a date on the bottle in permanent pen recording when you make it into a solution to keep track of this.
Pros
The quickest method of chemical treatment.
Can be added to any amount of water from ¼ litre up.
Lacks chlorine taste.
Comes in a compact and convenient plastic bottle, so difficult to break.
Can be used in any shaped bottle or water container.
Can make up stronger solutions for washing fruit and veg.
Less fiddly than opening tablets.
One small bottle can treat up to 250 litres of water.
Still quite cheap even though more expensive than Chlorine tablets. (£12 for 250 litres)
Cons
The solution goes out of date 40 days after being made into a solution from its tablet form.
Currently, it is only possible to buy in packs of 10 or larger.
Can be spilt.
Can't take a smaller amount, say enough to treat 10 litres, which means tablets might be more suitable for short trips or to carry just in case.
On any trip I'll use at least two of these methods, often three. It's not a set formula, instead, about picking the methods suitable for your trip.
Summary
It is quite possible that you may plan for multiple methods of purifying water on any expedition depending on the environment you’re in. It is also good not to be reliant on one method. Before you go away research what waterborne diseases you could be at risk of and make sure your water purification system protects you from them.
