Sand Filter A. Blower (Mec. Eng); A. Elkjaer (Mec. Eng); Water Purification

Sand Filter
A. Blower (Mec. Eng); A. Elkjaer (Mec. Eng);
W. Ellis (Mec. Eng); Y.L. Lee (Chem. Eng)
Water Purification
 Drinking, washing, cooking, growing crops and rearing live
stock all require water.
Water can be collected from a natural water source or by
collecting rainwater.
Although boiling water is effective at killing bacteria, chemicals and sediment are not removed.
It is essential that they are fast and efficient to ensure there
is a constant supply of clean drinking water.
Biosand Filter
Slow Sand Filter
Slow sand Filters work by allowing gravity to draw water through a filter media
that composed of sand and gravel.
 Has to be continuously operated
 Cleaning device require considerable effort so only used for low turbidity
 Large scale
Lid – Tightly fitting lid prevents
contamination and unwanted
Inlet Reservoir Zone - Where
water is poured into the filter.
Diffuser – Prevents disturbing the
filtration sand layer and protects
the biolayer when water is poured
into the filter.
The biosand filter (BSF) is an adaptation of the traditional slow sand
filter. The biosand filter is smaller and adapted for intermittent use,
making it suitable for households. The filter container can be made of
concrete or plastic and is filled with layers of specially selected and
prepared sand and gravel.
Most BSF's are used by individual families, often shared with extended
family members, friends and neighbours.
The BSF Removes:
Particulate material
 Small Scale
 Operate as required
 Inexpensive to clean and maintain
 Expected service 10 years
 Capacity: 20-60 litres of water/hr.
Standing Water Zone – This
water keeps sand wet while letting
oxygen pass to the biolayer
Biological Zone – Develops at
the top 5-10cm of the sand surface. The biolayer removes pathogens, suspended particles and
other contaminants.
Filter Body – Holds the sand and
gravel layers.
Outlet Tube
Ref: WHO (2006)
Nigerian Water
 Nigerian water supplies are often contaminated with iron,
manganese and arsenic, in addition to pathogens and sediment.
Iron and manganese can affect the taste of the water whilst
arsenic causes cancer and reproductive problems.
Pathogens cause diarrhoea , which kills around 22 million
people each year.
Non-Biological Zone – Contains
virtually no living microorganisms
due to the lack of nutrients and
Separating Gravel Layer – Supports the filtration sand and prevents it from going into the drainage layer and outlet tube.
Drainage Gravel Layer – Supports the separating gravel layer
and protects the outlet tube from