Maintenance
Over time, particles will accumulate between the sand grains in the filter. Also, as more water is poured a biofilm will form along the top of the diffuser plate. Both of these occurrences cause a decrease in flow rate. Although slower flow rates generally improve water filtration due to idle time, it may become too slow for the users’ convenience. If flow rate go below 0.1 litre/minute, it is recommended by CAWST to perform maintenance.
The cleaning method known as the “swirl and dump” or wet harrowing, is used to restore flow rate. To do this, about one gallon of water is added into the filter before cleaning (assuming the filter is empty). The upper layer of sand is then swirled in a circular motion. Dirty water from the swirling is dumped out and the sand is smoothed out at the top. This process is repeated until flow rate is restored.
It is also recommended to clean the diffuser plate, outlet tube, lid, and outside surfaces of the filters regularly.
Long term sustainability and efficacy of biosand filters is dependent on continued education and support from knowledgeable support personnel . Ideally this support should come from the local trained water workers embedded in the community.
Read more about this topic: Bio Sand Filter
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