Multimedia Filters Design

[QApollo]

I need some guidelines in regards to Multimedia Filters bed dephts. Specially on the gravel support layer.

I have found on my system that there´s media leaking downstream and my first guess is that the gravel layer is too short.

By the way, is there any difference between layers depth when using air for BW?

 

[ch81pc]

How many stages or media types in your filter? Anthracite, courser sand, finer sand, gravel?
Are you doing a collapsed pulse (combined water/air) BW or individual aire then water stages? If your leaking media, where is it appearing? It could be beign lost during backwash or else through damaged nozzels in the floor.

 

[bimr]

The design of the gravel support will depend somewhat on the design of the underdrain.

You should have from 4 to 6 layers of gravel. A four layer filter should have gravel gradings of 0.7-1.4 mm, 2-4 mm, 6-12 mm, and 18-36 mm. A six layer filter should have gravel gradings of 0.6-1.1 mm, 1.2-2.4 mm, 2.4-4.8mm, 4.8-10mm, 10-20 mm, and 20-40 mm.

The finer gravels should be 3-Inches in depth for each gravel gradation. The coarser gravels should be 4-5-Inches in depth for each gravel gradation. The overall depth of the support gravel should be approximately 0.3-0.45 m (12-18-Inches).

http://www.who.int/water_sanitation_health/publications/ssf4.pdf

Verify the gravel support requirements with the manufacturer of your filter.