Water purification mechanism of slow sand filter

Bio-filter

Bio-filter which consists of algae and microorganisms grows naturally on the sand bed to a few millimeters by passing raw water to slow sand filter basin.
Water is purified by the action of microorganisms mainly through the filter in the slow sand filter basin.
Below is bio-filter found at Nabeyaueno water purification plant.

Many kinds of organism are found through the microscope. Below is some examples.

Action of bio-filter

　　・Removal of turbidity
　　・Removal of ammonia and manganese by aerobic microorganisms
　　・Removal of must compound by microorganisms
　　・Reduction of organic matter by biodegradation and adsorption
　　・Inactivation of crypt by eating by microscopic animal

Other organism in slow sand filter basin

Ecosystem is formed by algae, microscopic animal, bacteria, shrimp and fish etc. in slow sand filter basin.
Microscopic animal in water eat phytoplankton floating in water and purify water.
Below are some examples of microscopic animal and phytoplankton found at Nabeyaueno water purification plant.





Below are some examples of shrimp and fish making their habitat in slow sand filter basin at Nabeyaueno water purification plant.