Category:
Introduction
On Water
Purification of drinking water is an important part of life, not only
in the tropics, but everywhere, anymore. Especially since our efforts
to use their own weapons against pathogenic micro-organisms have enabled
their latest, newly resistant strains.
If you go so far as to boil your water, that's about it. Boil your food
and scald your dishes and appurtenances while you are at it, or at least
let them dry in the sun. This is the most comprehensive prophylaxis against
water-bourne diseases.
Three minutes of boiling at sea level or thereabouts will kill most bacteria and parasites, even those capable of encystment. Virus particles, on the other hand, are barely alive to start with, and some are very difficult to kill. The hepatitis 'A' virus, often called 'infectious hepatitis,' is endemic throughout the tropics and is making new inroads in temperate climes... it takes twenty minutes of boiling at sea level to inactivate. This and other virus diseases are usually associated with particulate matter and so filtering and settling are useful tools.
If circumstances force the use of muddy, silted or stagnant water, you may want to try this trick; first allow the sediment to precipitate if time allows. Then pour off into a clean vessel and bring to a boil along with a lump of charcoal from your fire. This 'activated' charcoal will absorb some of the off flavours from decomposing vegetation. Let this settle once more, and it is ready for use.
So much for water in the jungle. Most of us will find ourselves using water from a big city faucet. Modern municipal 'treatment' of waste water usually entails settlement of solids in large tanks before the waste water is returned to the same source from which potable water is drawn. Few modern polis can boast water in its pipes that is free of micro-organisms. Normally, if the fecal organism count goes higher than the arbitrary cut-off level, a certain amount of chlorine is added. This may not seem a suitable solution to us all but it is expedient for city managers. After all one can only do so much with so little.
Most, if not all, of the simple counter top filters are simply inefficacious at removal of anything more than a bad smell. Many simple filters are simply a wonderful place to store cultures of various bacteria. Charcoal filters also fall into this category if used by themselves. Once infected, the filter itself becomes a perfect breeding ground.
Reverse osmosis is one of the most effective ways to remove bacteria, virions, heavy metals, organo-chlorides and other contaminants with large molecules. Unfortunately, the membranes of these systems are very delicate, and once torn, perhaps by a fragment of rust or mineral scale, allow pollutants to pass right through them.
So, for the real big city filter system, here's what you must do. First, deploy a one micron pre-filter. This will exclude rust and other sharp edged particles from the membrane of the second unit, the reverse osmosis filter. Thus protected, this will last many times longer than otherwise. For a final treatment, use a sealed 'activated' charcoal filter. Since the water entering this last appliance is free of microbes, it is much less likely to become infected, and so its life if also prolonged.
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