As granular media is ...
Published by Bob Foerster, Executive Director at Nevada Rural Water Association
As granular media is backwashed repeatedly it 'tumbles' and loses its sharp edges, essentially going off-spec. Then media starts getting washed out and there is less in place, accelerating the problems. Inspect the grains using microscope or magnifying glass. If they are rounded off you could have a sieve-size test conducted to verify but if it has been in service for several years just replace it. I suggest replacing it all at once not adding-to. Assuming the ongoing operations include monitor and adjust backwash rate and duration, carefully control coagulant dose and regularly look for underdrain problems.
1 Comment
Media is certainly old. It was commissioned in 1992. Thereafter, many a times media has been added but just to compensate the loss during backwash. Replacing all at once looks like a solution here. Thanks!
Published by Ashish Yadav, Assistant Director at Ministry of Defence, India