Testing Filter Media - Combining Sand Sizes

When testing for filter media, specifically for the uniformity coefficient (UC) and nominal effective size, are you allowed to combine the different sizes of the sand or do you test each sand individually as per the layering on the filter bed?

Taxonomy

• Sand Filter
• Filtration
• Filters
• Filtration Solutions
• Filtration

8 Answers

1. Different ranges must be tested separately.

2. Hi Michael

   Because you want do analyze design criteria of your media with the test results, it is better to test different layers separately.

3. Test these separately based on size ranges for different layers.

4. For multimedia filters, UC to be determined for each media separately to confirm the design criteria.

5. Dear Michael,

   
   If you mix the different UC and nominal effective size of the different sands, then you will obtain a different UC and a different nominal effective size for the mixed sand.

    

   If you want have a multilayer filter, and you can use antracite, then I recommend you use different densities media as sand and antracite with different size. The you can obtain different layers with different CU and different nominal effective size, and I think a better filtration system.

    

   Regards,

    

   Orlando D. Gutiérrez Coronado

6. Hi Michael,

   I would recommend that if different filtration layers are specified the layers must be classified separately. My perception is also that there is generally a trend away from layering, unless there is a specific requirement for a dual media filter. Depending on the application, I would go for a single layer layer suited for the selected nozzles and then sand must definitely be classified for the specific single media on it's own.

   Regards

   Andre Visser

7. I agree with Derek, each layer should be tested individually. 

8. If you have a stratified filter (multi-media) you should be checking each layer individually. If you dissimilar materials like anthracite & sand you need to do each one individually. 

   1 Comment

   1. Derek has set you on the right path. Tim Shrum