Dear Lokesh,  I have faced ...

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Dear Lokesh, 

I have faced the same problem several years ago and it was due to the fact that suspended solids were escaping from the settling tank, along with clear water, as a result of not frequent operation of the filter press.

So the reasons for your problem could be :

1. High concentration of suspended solids, much higher than the initial filter design.

2. Suspended solids escaping from your settling tank, if you've got any.

3. Poor SAND QUALITY. If the sand is not QARTZ type- special sand for sand filters-  but it's normal building sand then the susdpended solids stick with the sand particles. This blocks the water routes and as a result you get high pressure drop and frequent backwash.

Please note that if No3 is your problem then when you backwash the filter only a small part of the suspended solids are rejected so only a small part of the filter works. The rest 

is blocked.   

N.B. You must remember that the filtration speed should never exceed the value of 15 m/h. To calculate that you need to divide your flowrate by the cross-sectional area of the filter. 

 

2 Comments

Greg Moss a few seconds ago

Lokesh- I concur with George.  First - check your source water and your pre-treatment processes.  Then - the filter material itself. One annoying problem we faced was the angular grain shape of the filter sand,  which had orders of magnitude lower k, than would have been expected based only on grain size.  Look at your filter material under a microscope - if it is moderately sub-rounded to well-rounded, then that is not the issue.  However, if it is sub-angular to angular, that may be an important part of the issue.

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