Truckloads of sand and gravel are first brought from a river with low silt content and located far far away from human waste. After the river sediment is delivered the next step is sorting by grain size. This is done by using 3 different sizes of screen through which the sediments are sieved. In one village we washed the sand before distributing it to the households. In most of the villages we let the householder wash the sand at their home. My team assembles the filter at the home, first gently placing gravel in the bottom of the bucket not to break the lower pipe that allows water to flow out. Next 4 liters coarse grained sand and then 12 liters of fine sand are placed in the 50 liter plastic filter. The bucket is then filled with water and Chlorine left to sit for 48 hours to kill bacteria. After the 48 hours the upper basin holding the nails is then placed in the bucket. Arsenic will be reduced in the first flow through. It takes about 2 weeks for the microbial layer that kills most bacteria and viruses to develop.

Loaded sand and gravel
3 different sizes of screens
Sorting
Washing sand and gravel
A completed filter