Filter media consists of coal, sand and garnet in the direction of flow. The media characteristics are given as below –
Media characteristics
Media, Effective size in mm D10, Uniformity coefficient, D60/D10, Specific gravity.
Coal, 0.9-1.0, 1.6, 1.3
Sand, 0.4 -0.5, 1.3 – 6.0, 2.65
Garnet, 0.2 – 0.3, 1.3, 3.0 – 4.0
The rate of filtration of 200 to 400 lpm/sqm can be achieved in this filter. In addition the stratification problem after back washing can be avoided by multimedia. However, an underdrainage system needs to be modified.