Lesson 3 - Water SAQ
This lesson allows you to test yourself on the material covered in the Water lesson and determine the level to which you have met the learning outcomes.
Suggested Response - Q2
** Describe the operation of a typical sand filter.
Response:
In a typical sand filter, water is filtered through layers of sand to remove particles. The water is pushed through the media from the top, and filtered water exits the bottom. The material is periodically backflushed to remove the trapped particles. Backflushes are done in reverse, as the term ‘back’ implies. The particles settle back down with the heaviest particles settling out first so that the layers are reformed. Sand filters can be unpressurised, but most modern ones are pressurised as this allows for greater throughput.
The figure below illustrates the different layers of sand the water is filtered through using this method of water treatment.
Figure: Typical pressurised multimedia filter