2 ms·
It's the trusty old rapid sand filter. http://www.who.int/water_sanitation_health/hygiene/emergencies/fs2_14.pdf http://www.who.int/water_sanitation_health/hyg
by neurostimulant 13y ago
It's the trusty old rapid sand filter.
http://www.who.int/water_sanitation_health/hygiene/emergencies/fs2_14.pdf http://www.who.int/water_sanitation_health/hygiene/emergenci...