The Community Bio-Sand filter works in the same way as traditional slow sand water filters, which have been used for centuries. The difference is that the water does not need to flow through it all the time. It can be built with a plastic container, with layers of sand and gravel inside it. The sand and gravel remove dirt, bacteria, viruses and parasites and other impurities from the water.
Water is filled up to the top of the filter tank. There is a diffuser basin placed just above the sand bed that absorbs the shock of the falling water so it does not disturb the sand.
Traveling slowly through the sand bed, the water then passes through several layers of gravel and collects in a pipe at the bottom of the filter. It is then pushed up through plastic piping and out of the filter to the water storage tank.
As with all slow sand filters, the removal of pathogens happens in the Bio-Sand Filter through a combination of biological and mechanical processes.? When water is filled up the top of the filter, the organic material it is carrying is trapped at the surface of the sand, forming a biological layer or ''. Over a period of one to three weeks, micro-organisms colonize the , where they find food (the organic material) and supplied by the water.