Clean water

How many of you are nervous about the water you drink when walking or trekking? In some places it is a valid worry as there are potential ‘nasties’ lurking in impure water that can lead to illnesses, including travellers diarrhoea. The germs that cause the problems are, in order of size:

  • Protozoa and cysts -  hard-shelled parasites or cysts . e.g. Giardia and  Cryptosporidium. Can be found in UK and Ireland but is most likely in developing countries
  • Bacteria - E.coli, cholera, salmonella, typhoid and dysenter
  • Viruses - Hepatitis A

Contaminated water is often blamed unjustly and proper hygiene is just as important, unclean hands can often transfer pathogens to food or water.

What is the source?

Choose carefully, even mountain streams may have villages above them and lowland agriculture and industry use herbicides, pesticides, and fertilizers. Dirty water is unpleasant to drink and the bits can upset your stomach. The bits also reduce the effectiveness of the methods for creating safe water. If the water has bits in it, let it settle for an hour or more and siphon off the clear water. To clear larger debris pour the water through finely woven cloth, a coffee filter, a sand filter made using a sock or a ceramic filter with a pre-filter on the intake hose to eliminate larger particles.

Safe water

Choosing the best method to clean water depends on the amount you need, the source, time, cost and the equipment carried. When you treat water in a container with a lid, be sure to let some of the treated water clean the threads of the cap and rinse the bottle with clean water between uses.

Bottled Water – Bottled water creates a waste problem and should be avoided! If you must drink bottled water, carbonated is best, because the acidity will help to kill any germs.

Heating – When you have the time and fuel, heating water to 65°C for a few minutes kills all germs including Cryptosporidium and Giardia cysts. Water that is brought just to a boil is safe and boiling for longer, even at high altitudes, simply wastes time and fuel. Avoid boiled water in ‘tea houses’ as most use trees as a source of fuel. Other technologies make boiling water largely unnecessary.

UV light –      impart any taste to the water. Four Alkaline AA batteries purifies 10-15L, Lithium batteries 65L,_DSC0361.jpg and NiMH 75L.  However its effectiveness is lower in dirty or icy water (see above), if the water clarity is poor filter it first or give it three doses of UV. The downside is that it is expensive, the quartz lamp can break, they are relatively heavy and batteries run out. The UV tube wears after 5000 uses, but can be replaced by the manufacturer. The ‘steriPEN’ uses UV light to destroy the DNA of germs rendering them harmless, and does not

Chemical purification - Chemical purification can cheaply treat a large volume of water while you occupy yourself with more important tasks. Boiling, filtering or chlorine dioxide are the only ways to eliminate Giardia and cryptosporidium.

Iodine tincture and chlorine – These eliminate bacteria and viruses but not Cyclospora and cryptosporidium cysts plus they need over an hour to eliminate Giardia especially when the water is cloudy or cold. If you are in a hurry, double the dose and halve the contact time.Iodine and Chlorine both flavour the water, but neutralising tablets or vitamin C will remove the taste, but add them onlyafter the contact time as they will deactivate them. Iodine is also a useful antiseptic and a drop or two on a leech soon makes it drop off. Although iodine is rapidly cleared from the body, you should not use it if you have an allergy to iodine, active thyroid disease, or are pregnant. Some literature suggests using iodine for six weeks or less, because of this iodine tablets are no longer sold in the EU, but Iodine tincture is available through some chemists.

Chlorine dioxide (ClO2) -      Cryptosporidium. ClO2 also, destroys sulfides, cyanides, and phenols, controls algae, and neutralizes iron and manganese ions. A 4-hour wait time is required to eliminate Cryptosporidium from cloudy, cold water. Chlorine dioxide is available in both tablet and liquid preparations. Chlorine dioxide is extremely effective and rapidly kills everything including_DSC0347.jpg

Filtration – The rational behind using filters is to clear the water of larger protozoans including cryptosporidium, bacteria, sediment and organic debris, thus allowing lower doses of halogens to be used to kill viruses more rapidly. They work by trapping pathogens in a micro-porous screen, but some viruses are too small to trap. Ceramic filters have a long life (2000 litres) and can be cleaned many times before the cartridge needs replacing. A pre-filter helps reduce clogging. Ceramic filters can come with a carbon core, to remove chemicals (but not viruses) from water e.gMSR mini works. Some filters have both a filter and achlorine/ iodine-resin element that is capable of killing all viruses, but contact time with the iodine is limited. There are also some lightweight straw and bottle filters but if the water is dirty then they block in next to no time. There are also gravity-fed filters to filter the water without pumping.

Filters provide immediate access to small amounts of water without adding any taste. However, they are expensive, bulky and cracks created by freezing or erosion may allow the passage of unfiltered water, they can become contaminated and most do not remove virus particles.

So what do I actually do?

In general, gravity-fed or pump filters, work faster than chemical treatments, though chemical treatments are lighter and smaller. 

Day hikes - In Ireland I simply carry enough water, but if I am travelling lightweight or overnighting where I am a little concerned about the water source I use chlorine or Iodine or my SteriPEN .

Multi day hikes - I carry Chlorine dioxide when I am unsure about the source or filtration combined with Iodine/chlorine.

When I want to treat a lot of water, or there are limited water sources pump filters or gravity-fed filters work well. Boiling is fool proof when you have enough time and fuel.