Flow rate surface area

[KnH]

#848

In the flow rate section, it mentions that a 55g drum would have a higher floe rate than a concrete sand filter because of the increase surface area.

It says the concrete sand filter (300mm diameter = area 282744 mm of surface area) has a recommended flow rate 22-25 lph.

If I use a plastic drum (584mm diameter = area 1071461 mm of surface area). 1071461/282744= 3.79 ratio
3.79×22=83, 3.79×25=94, between 83-94 lpm seems kind of fast

What would the recommended flow rate be for a continuous flow slow sand filter?

[Eric]

#849

Flow rate for any kind of slow sand filter should be in the range of 0.1 to 0.4 m3/m2/hour. The larger the area, the more flow, so it seems your calcs are more or less correct. Below my calcs:

Round concrete filter:
Diameter: 0.26 m
Area: 0.0531 m2
If 1m2 can have a maximum of 400 litres/hour flow rate, then 0.0531m2 can have maximum 21.23 litres/hour

Metal drum filter:
Diameter: 0.584 m
Area: 0.2677 m2
If 1m2 can have a maximum of 400 litres/hour flow rate, then 0.2677m2 can have maximum 107.09 litres/hour