As any aquarium
book will tell you, on its own, sand is a merely a mechanical filter - it will take out large (compared to a bacterium
) particles, and make the water look clear
It won't make it clean. There's still nastiness in there. Ammonia
is not good for you. It's probably what kills the athlete's foot fungus
However, sand is a nice place for the kind of bacteria that eat yucky urine by-products
to live, and if you leave it long enough, and keep feeding them, they will eat away all the crap
in short order. This is Biological Filtration
. The chief process is
The other main method of filtering water, Chemical filtration
, involves using chemicals like carbon
to neutralise the waste, and chlorine
or similar to sterilise it. It's the quickest method, but can't always be combined with biological filtration, as it kills or starves the bacteria. As Cletus the Foetus
suggested, ground up
or charcoal would do nicely.
So, in short, sand
from the bottom of a river, good.
Sand from homebase
, bad. Bits of
charcoal mixed in, even better.
As it turns out, coal may have all manner of impurities, including Mercury, Arsenic and Cadmium. Charcoal doesn't.