posted 14 years ago
I have lots more to say, i always bubble over with these themes, i have been looking things up on you tube again.
arashinage's video bio sand filter says that you use 70 mesh silica sand for a sand filter. this is a barrel full of sand with a bit of gravel at the bottom.
The pipe the water comes out of, leaves from the bottom of the barrel and then bends upwards to just below the level of the top of the sand and then turns out and has a tap on the end. So you will only get the water from the level of hte top of the sand coming out of the tap.
The bio layer at the top is called schutzdecke in some videos, in plain english smutty deck layer, i suspect or more scientifically, the biological layer.
the top layer of sand catches bacteria and bits of organic matter that live and breed in the first two centimetres and form the biolayer.
HideouseMonsterHank says that you need to have dirty water in the filter for about two or three weeks to get you bio filter top layer, and that you need to keep the whole wet he thinks. commenting on a videoand asks to be advised if he is wrong.
One thing that is fun about the computer is that people with unserious names make very seriouse commments.
Another good video to whatch is HOw a sand filter works animation style.
The bit below the bio filter is said to filter the water through mecanical means, these being that particles get held up in the sand for one and for another that the bits of sand have static eletricity that stick particles to the sand, and thirdly that the dark and lack of food kills pahtogens held up in the sand.
It seems they are installing these biosand filters all over India and Pakistan, there are lots of indian and pakistnai videos on it . Some comments on one videos said "it woudn't work" and one woman replied it would be much better than no filter. However scientist have studied it and it is vouched for at least it kills nintey five percent of pathogens and all parasites. It maynot be so absolutely sure as chlorine but it seem it is pretty sure. There are videos of sand filters in two litre bottles, type, big coke bottles about a third full of sand, they did mention how much sand you have to have. Zenrainman who is great on all these themes has a video of this is biosand filter-using 2 litre pot bottle. agri rose macaskie