It is taken for granted that with a turn of the tap, out flows pure drinkable water whenever we require it. However, when disasters strike such as floods, hurricanes, earthquakes this supply maybe disrupted which can pose a real threat to your life.

A human being can survive an average of three days without the consumption of water, assuming normal conditions. In colder or warmer temperatures or with exercise, the need for water is greater.

A typical person will lose two to three litres of water per day. Four to six litres of water or other liquids are generally required each day in the wilderness to avoid dehydration and to keep the body functioning properly.

Lethargy, headaches, dizziness, confusion are a clear sign of dehydration, which will eventually result in death. Even mild dehydration reduces endurance and impairs concentration, which is dangerous in a survival situation where clear thinking is essential. If your urine is dark yellow or brown urine this is a clear sign of dehydration. To avoid dehydration it is essential to have a supply of drinking water at hand. However preparation to render that water as safe as possible needs to be carried out to minimise negative impact to your health.

Pollutants :Both organic and inorganic pollutants can be in the water supply such as detergents, insecticides & herbicides, petroleum hydrocarbons, debris, heavy metals, fertilizers etc. It does not need explaining that these are bad for your health.

Pathogens & Micro-organisms :In water that looks clean can lurk pathogens and micro-organisms invisible to the human eye. Some of them with symptoms of disease are listed below

Giaridia lamlia - The Giardia cyst survives weeks to months in warm water and therefore can be present wells and water systems, especially stagnant water sources such as naturally occurring ponds, storm water storage systems, and even clean-looking mountain streams. Symptoms of infection include diarrhoea, malaise, excessive gas often flatulence or a foul sulphuric-tasting belch, pale, foul smelling, greasy stools, bloating, nausea.

Novovirus - characterised by nausea, vomiting, diarrhoea, and abdominal pain; and in some cases, loss of taste. General lethargy, weakness, muscle aches, headache, and low-grade fever may occur. Symptoms may persist for several days and may become life-threatening in the young, the elderly, and the immune-compromised if the dehydration is ignored or not treated.

Parasitic Worms - They are worm-like organisms that live and feed off living hosts, receiving nourishment and protection while disrupting their hosts' nutrient absorption, causing weakness and disease.

Salmonella - Cause diarrhoea which usually heals spontaneously and does not require antibiotic treatment. However, people at risk such as infants, small children, the elderly, or immune compromised individuals.

Cryptosporidium parvum - the main symptom is a self-limiting diarrhoea in people with intact immune systems. As well as the watery diarrhoea, there is often stomach pains or cramps and a low fever. Other symptoms can include nausea and vomiting.

So now we know about some of the nasties in unsafe water, we will move on making it safe for human consumption. There are many ways in which water may be gathered and rendered safe in a survival situation, such as boiling, filtering, chemicals, distillation, UV etc

mechanical water filters are usually small, portable and light 0.5-1.0 kg or less. They tend to work by filter ing water through a hand pump mechanism, although some use a siphon drip, while others are built into water bottles. Dirty water is pumped via a screen-filtered flexible silicon tube through a high tech filter, ending up in a bottle. These filters work to remove bacteria, protozoa and microbial cysts. Other methods used for filtering are sand based solutions

it is very simple to boil water. You will be able to use a teakettle or a large pot. Boiling water treatment can occur in as little as one minute, you want the water to be at an aggressive boiling point to make sure you kill everything. However, in a survial suitation energy to heat the water may not be ready at hand.

Chemical treatment of water depends on the killing of bacteria, Giardia and amoeba cysts, and viruses by adding a chemical to the water. Halogens (chlorine and iodine) are most commonly used. The important points are that the killing effectiveness of the chemical is dependant on concentration of the chemical, temperature of the water, and contact time. Note that Iodine and other halogens appear to be relatively ineffective at killing cyclospora, a troublesome diarrhea-causing bacteria

The ultra-violet rays, similar to the sun’s UV but stronger, alter the nucleic acid (DNA) of viruses, bacteria, molds or parasites, so that they cannot reproduce and are considered deactivated. UV treatment does not alter the water chemically as nothing is added except energy. It should be noted that the deactivated microorganisms are not removed from the water. UV treatment does not remove dirt and particles, metals such as lead or iron, or hard minerals such as calcium. Don't forget that to run the UV light source batteries are required.

Water Distillation involves heating the water to boiling point and condensing the steam vapour. Pollutants with a boiling boint near that of water are hard to remove, but generally the distilled water is of a very high quality.

Distillation produces very pure water but also leaves behind a leftover white or yellowish mineral scale on the distillation equipment, which requires that the apparatus be frequently cleaned

When making water safe it is essential good cross contamination practice takes place to avoid recontaminating your clean water.