Bio-sand filters are based on the same filtration system the earth itself is based on. Water added to the top of the filter passes through a large sand bed then through two different size gravel beds.
We use sand and gravel taken from a local riverbed. It is screened and sorted to the required sizes. These layers are then washed and measured into bags that can be stored for transportation to the site where the filter will be installed. A specific flow rate must be attained and maintained. This requires periodic checks to each filter to insure it is flowing properly.
It takes 30 days of use for the system to create a biolayer in the top 1-2 cm of the sand. The biolayer consists of micro-organisms that eat the pathogens in the water, which contributes to the treatment of the water being filtered.
Filtered water is safe to drink after the biolayer is formed (30 days).
The filter uses sand and gravel
from the riverbed
which is delivered by truck
Then the sand is spread out to dry
before sifting can occur
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After it is dry, the workers sift the gravel out of the sand. The filter uses 2 sizes of gravel (12mm and 6mm), so it needs to be sifted twice. |
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After the gravel is sifted out to the correct size, the sand is sifted again. The sand needs to be the correct size too. The filter needs three layers. Two layers of gravel in the bottom and 100lb of sifted sand on top. There is a lot of work involved to prepare the filter for installation. After all the sifting is done, the sand and gravel is washed |
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100 pounds of sifted and washed sand is measured and bagged for the installation |
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Two sizes of gravel,
sifted, washed and bagged |
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To install:
- ~add gravel
- ~add sand
- ~put in diffuser plate
- ~pour water through for 30 days to form biolayer
- ~Filtered water is safe to drink