Water treatment in field conditions

The following article discusses the treatment of water with use mainly in military campaigns, exercises, during disasters and travel. Potable water is particularly problematic, there are not such high demands on commercial water. Drinking water from unknown wells and stagnant reservoirs can be risky and therefore it is necessary to treat the water.

Mechanical modification
The water is treated in the simplest way by melting the upper layers or by various filtrations - by cleaning muddy sources by free filtration through the soil into a parallel excavated reservoir, by using artificial filters (improvised or purposefully made), then by microfiltration of water (mechanical-chemical treatment). Filters can be supplemented with silver, iodine or activated carbon (porosity of 0.4 μm ensures the removal of bacteria ).

Editing physical
In winter, you can take advantage of the freezing conditions. Desalination can be done in the cold by repeated freezing in half (we leave the water in the cold until half of it freezes, then let the resulting ice melt and freeze again until half of the volume freezes, etc.). After several cycles, we get water almost without salt.

On the contrary, thermal disinfection of water can be used. The water is thermally treated by boiling, the total treatment time varies according to the altitude (in higher places the boiling point is lower and therefore the time must be extended to sufficiently treat the water). When treating water at boiling point, one minute is sufficient up to 1000 m above sea level, three minutes up to 2000 m above sea level, ten minutes up to 3000 m above sea level (lower boiling point). Also, if enteroviruses or bacterial spores are present, the length of the boil must be extended. The following points indicate how long the boil should be for the destruction of various pathogens:
 * vegetative forms of most bacteria are destroyed at 65 °C – 3 minutes, 100 °C – 3 seconds
 * enteroviruses: 70 °C – 1 minute,
 * bacterial spores: 121–136 °C – 20 minutes,
 * protozoa (Giardia, Cryptosporidium): 70 °C – 10 minutes.

Chemical treatment
Chemical treatment usually takes place by disinfecting the water. Before disinfection, turbidity can be removed by flocculation with aluminum alum (aluminum-potassium sulfate). Disinfection uses ions of chlorine, iodine, bromine, silver, hydrogen peroxide, ozone, peracetic acid, chlorine dioxide, isocyanuric acid, followed by dechlorination with sodium sulfate or ascorbic acid. Most often, tablet forms of active substances are used, which work for 30 to 60 minutes. Chlorine preparations include, for example, Savo, iodine preparations include Portable Aqua, Polar, Pure, and other preparations such as Micropur, SanosilD and Carola Bio. It is necessary to prevent secondary contamination of water. Dechlorinated water should not be stored for more than two days.

Edit other
There are also portable, bacterial water filters based on salt water electrolysis. Their advantage is that they do not cause changes in sensory properties, they kill common pathogens including E. Coli, Giardia and Cryptosporidia. They are used for larger groups during military campaigns or exercises, tourism, crisis situations or disasters. Treats up to 200 liters of water on one charge.

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 * Individual source of drinking water