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Water purification

The saying goes we can live three weeks without food but only three days without water. But anyone who has not had a drink all day will tell you how they are experiencing a hangover type headache, lethargy and irritability.

So we need water, lots of it, and a constant supply of it. Your hydration needs change constantly, but they are a result of three factors, the climate, your level of exertion, and your physical needs. In an ideal world you will have practiced due diligence before setting out, drunk plenty of water before you leave, worked out your route, and either have enough water with you or know where you can resupply. Information on hydration in sports is freely available out there on the internet.

In the height of summer, even in the UK, as the temperature and our exertion rises we sweat more so our consumption needs to increases to compensate. Sooner rather than later we are gong to have to start looking for sources of water.
In the UK and other temperate zones water in the main is not that far away in the form of streams, rivers, ponds etc. but how do I know if it is safe to drink? The short answer is we don't. 

Clear running water you can see through is much better than standing turbid water. Turbidity is the murky brown or cloudy particulate in water preventing you looking through it. But even clear water can contain things that can make you pretty ill. 
Here are three things you should know about water:  Why can it make you sick, how do you make it safe, and how should you storage it?  these three things will give you the best chance of protecting yourself anywhere in the world should you find yourself having to survive for an extended period.

Why it can make you sick.
The short answer is 'contamination', particulate some of which can be invisible to the naked eye, suspended in the water, which is broken down into four key elements. Chemical hazards, viruses, bacteria and organisms.

  • Chemicals such pesticides and nitrates enter the water table through from farming, lead, arsenic or Mercury etc from industrial accidents or illegal waste dumping enter the water table impact on the environment.
  • Viruses are the smallest “living” organic matter, though not considered true life forms, they do self replicate by attaching themselves to and invading other cells. Therefore they are smaller than bacteria, can be as small as 20nm (nanometers) in length, and includes Parvovirus, Rotavirus and Hepatitis, which can cause all sorts of ailments such as Hepatitis-A, Gastroenteritis, Meningitis, Conjunctivitis, and so on
  • Bacteria found in sewage and fertilisers are larger at starting at 200nm and upwards, they are complete sequences of DNA and RNA and can include E-Coli, Salmonella, legionella, Campylobacter Campila Bolulinum. Leading to legionaries disease, botulism and dysentery.
  • Organisms (Protozoan infections) these are single celled creatures such as Cryptosporidium, Entamoebe histolytica, leading to Gastroenteritis and Amoebic-dysentery.
Still want to drink that water?

How Can I make it safe?
There are several simple universal steps to making water drinkable recommended by aid agencies used across the world. Firstly, look for flowing water. Rather than standing water, look for clear water rather than cloudy or murky water. avoid stagnant ponds.




Straining: can considerably reduce the turbidity (dirt and soil suspended in the water) by straining water through a cloth will remove debris. A Milbank bag is a cheap and useful piece of kit for this purpose, or can be made from a trouser leg in an emergency. Tie a knot in the bottom of the leg. Thoroughly soak your purpose made or emergency milbank bag first to aid filtration, then fill with water and hang over your collecting vessel to catch the water as it drips through the bottom trapping debris in the cloth. Obviously as you continue to use a milbank bag it will become soiled and full of dirt. so remember to rinse it out regularly to aid filtration and
   Straining will remove the Turbidity but the weave will not be fine enough to remove viruses or bacteria so we then need to move on the next stage. 

Disinfection: is in turn broken down into three types- Boiling, Solarisation, Chemical

Boiling: bringing water to a rolling boil 100oC for at least one minute is considered the safest method of killing off any virus or bacteria. At altitude as the air pressure reduces so does the boiling point of water. At the top of Ben Nevis in the UK at 4,409ft the boiling point of water is already down to 95.3oC. If you’re lucky enough to go to Machu Picchu at 7,474ft the boiling point of water has dropped to 92oC. But the highest point of that trek at 13780ft the boiling point is at dangerously low level of 85oC. The aid agencies say 86oC is the minimum temperature required to effectively kill all water borne bacteria. Therefore you will need to boil your water for a minimum of 10 minutes to ensure the toughest bacteria is killed. The down side to boiling water is having enough fuel for a fire, you are able to make fire, and have a container you can place in or near the fire to boil your water.  it is also important to note that there are a couple of bacteria that even though die when boiled the can leave spores which can make you ill giving you an upset stomoch these are the spores of Clostridium Botulinum

Solarisation: also referred as SODIS or SOL-DIS (short for Solar Disinfection) utilises UV rays of the sun to destroy most germs that can cause sickness and infection, by using clear glass, plastic bottles, or even a sealed clear plastic bag, left in strong direct sunlight. UV rays pass through the glass and plastic increasing the temperature of the water. The down side to this method is that it takes many hours, a minimum of 5 hours in direct sunlight if you’re in warmer climates, longer if its in the UK this can effectively be increased to 1-2 days if it’s cool. For greater effectiveness place on metal plate to reflect heat and increase the temperature. The down side to this method clearly is the amount of time it takes, and Tastes odd. But shaking the bottle vigorously to add air will improve the taste.

Chemical: effective once the water has been filtered, Iodine or chlorine tablets are a measured doses for predetermined amounts of water. they are very effective at killing off bacteria and virus, but the down side is that they take about half an hour to work, and leave a rather unpleasant taste.

Modern travel filters: There are now a few modern filtering systems out there that are really efficient at removing bacteria and viruses from water using several different filtration types utilising activated charcoal or ceramic candles. Or inline iodine filters, and ultrafine mesh filters. The down side to filter systems are that they are relative expense and you have to look after and maintain them, replacing the filters periodically.

Storage: less of a problem if you’re on the move, rehydrate by drinking lots when you have the opportunity then refill your canteen and off you go.

If you’re camping in one spot for a while and are storing water then You don’t want to allow your water to become contaminated again. Here are a few points to remember.

Ensure that the pot you are using is clean and has a close fitting, and preferably an air tight lid.

Avoid cross contamination, if you have put your cup or bottle down on the ground don’t dip it in the storage pot and contaminate the standing water, also avoid putting your hands in the clean water, use a long handled ladle pour into a cup, don’t drink from the ladle and return it to the pot. Establish a routine. of filtering, boiling and storing clean drinking water in specific areas you are all aware of so that everyone is familier with it. Ideally keeping your clean water off the floor.
with two milbank bags and two billy cans I have kept a group of four adults well hydrated for a week  in a static camp from which we roamed out from and returned.
Lastly if you’re camping next to a stream collect water from upstream and wash down stream, and don't use the stream as a toilet.
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Good luck and safe drinking

Sources include:

INTERNATL MICROBIOL (1998) - Springer-Verlag Ibérica 1998

The Red Cross/Red Crescent field manual for aid workers

The Army Study Guide

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