Bio-sand water filters
Practical Action
Benefits & drawbacks
Advantages
Removal of turbidity, colour, odour.
Good microbial removal.
High flow rate.
Can be constructed of local materials.
Income generation.
Durable.
Minimal maintenance.
Drawbacks
Not 100% microbial removal; may require post-disinfection.
Limited transportation due to weight.
Turbidity should not exceed 100 NTU.
Costs
Capital Costs: approximately US$ 20.00 – 26.00 (Tk. 1450.00 – Tk. 1900.00 in
Bangaldesh)
Operation and Maintenance: Minimal.
There may be educational and training costs associated with teaching users how to properly
maintain their filters. Costs will vary across regions depending on the availability of materials
and labour.
Arsenic removal by Bio-sand filter
Bio-sand filters may be used to remove arsenic from well water
based on the principles of the co-precipitation and filtration
method.
A variety of technologies have been used for the treatment of
arsenic in water, including conventional co-precipitation with
ferric chloride, lime softening, filtration using exchange resins
and adsorbents.
The divalent iron concentration is in the range of 0.2-12 mg/l
and is positively correlated with arsenic concentration in the
groundwater. Fe/As ratios of greater than 40 (mg/mg) is
required to reduce arsenic to less than 50 mg/l in Bangladesh
well water. Arsenic removal by the bio-sand filtration process
included precipitation of arsenic by adding a packet of iron
nails to the top chamber.
Figure 6: The improvement in water
After mixing the water with the iron for a few minutes, the
iron will be oxidized to form ferric hydroxide that passes
quality can be dramatic. Photo: Practical
Action Bangladesh.
through the sand bed by gravity removing the precipitates;
clean water is collected from the outlet of the filter in the
conventional way.
Further information
Household Water Treatment Systems Practical Action Technical Brief
A Small-scale Arsenic and Iron Removal Plant Practical Action Technical Brief
Water Treatment Systems Practical Action Technical Brief
CAWST - Centre for Affordable Water & Sanitation Technology
12 - 2916 5th Avenue NE
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