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 pests. 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: Pathogens Particulate material Iron Manganese Arsenic Fluoride  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 oxygen. 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 clogging Before After