John O'Connor

Drinking Water Filtration: Replacement of GAC Caps at Bloomington, Illinois

Blog Post created by John O'Connor on Feb 14, 2014

Bloom - GAC cap.jpg

On a rotating basis, over a three-year period, the granular activated carbon (GAC) caps on Bloomington, Illinois' 18 sand filters are replaced with virgin GAC. Microscopic examination of both the carbon and sand shows that extensive microbial colonization has occurred on the media.


Moreover, the GAC has changed markedly in size distribution. As 'fines' are lost and larger particles are reduced in size owing to abrasion, GAC progressively occupies a narrower size range.