Slow sand filtration water treatment plants
Practical Action
• Complete filter cleaning
This operation takes place every five years.
1) Remove the sand and the gravel, without
mixing the gravel from the different layers.
2) Wash the filter layer and the drainage
pipes with a brush and water and replace
them if they are deteriorated.
3) Wash the sand and the gravel
4) Put the clean gravel and sand back in
place. Replace any lost sand or gravel.
(Bird’s eye viewÆ)
Maintenance of the filters
• Cut back weeds, shrubs and trees around the
filters.
• Protect the soil against erosion.
• Repair cracks in the walls of the structure.
• Examine the valves and grease them if necessary.
• Remove floating elements from the water layer.
• Monitor the growth of algae. If there is excessive growth the filters must be covered.
• Monitor the flow
entering the filters.
• Monitor the smell and
flavour of the water.
• Keep a record of the
turbidity at the entrance
to the filters and note
the length of the
filtration process.
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