The river water often contains bacteria that cause illness. The filter acts to remove these in four
The filter physically traps dirt in the top few inches of sand,
Microbiological life builds up in the sand layers, larger bugs eat smaller ones. Some
of the ‘bad bugs’ die in this way.
The grains of sand become coated in a sticky blanket. Bacteria and even viruses stick
and become part of the layer.
It takes time for the water to pass through the system. Certain bugs, eg Cholera, do
not live long enough in open water make it to the exit!
Sand Filters Are A Cheap Solution.
Sand filters clean water from biological contaminants, such as E.Coli, Cholera, or physical contaminants
such as suspended mud, etc. They are not proof against chemical contamination and do not
work with salt water. They are unlikely to be of value in environments prone to freezing.
They need at least one bucket of water each day as through put, so would not be ideal in situations
where the water supply was so intermittent as to make this impossible. They take six week
to initialise and so are not an "instant" solution in the sense that a charcoal filter might
be. Sand filters do not provide the "buzz" associated with the provision of a technically
advanced clean water solution.