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2. Biosand filter - Wikipedia

   en.wikipedia.org/wiki/BioSand_Filter

   The high water level (hydraulic head) in the inlet reservoir zone pushes the water through the diffuser and filter, then decreases as water flows evenly through the sand. The flow rate slows because there is less pressure to force the water through the filter. The inlet water contains dissolved oxygen, nutrients, and contaminants.

3. Slow sand filter - Wikipedia

   en.wikipedia.org/wiki/Slow_sand_filter

   However, some slow sand filter operators use a method called "wet harrowing", where the sand is scraped while still under water, and the water used for cleaning is drained to waste. For municipal systems there usually is a certain degree of redundancy , since it is desirable for the maximum required throughput of water to be achievable with one ...

4. Water filter - Wikipedia

   en.wikipedia.org/wiki/Water_filter

   A water filter removes impurities by lowering contamination of water using a fine physical barrier, a chemical process, or a biological process. Filters cleanse water to different extents, for purposes such as: providing agricultural irrigation , accessible drinking water , public and private aquariums , and the safe use of ponds and swimming ...

5. Water purification - Wikipedia

   en.wikipedia.org/wiki/Water_purification

   In water purification plants, there is usually a high energy, rapid mix unit process (detention time in seconds) whereby the coagulant chemicals are added followed by flocculation basins (detention times range from 15 to 45 minutes) where low energy inputs turn large paddles or other gentle mixing devices to enhance the formation of floc.

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7. Bank filtration - Wikipedia

   en.wikipedia.org/wiki/Bank_filtration

   Chemical filtration or ion exchange may take place when aquifer soils react with soluble chemicals in the water. [3] Most 'normal' contaminants (microbial organisms and inorganic or organic pollutants) will be removed by bank filtration, either because they get filtered out by the sand/earth of the bank, or because the passage time (which may ...