Activated Carbon in Potable Water Treatment - Norit

GAC - State-of-the-Art Technology
GAC filtration is currently the state-of-the-art
technology in many water treatment plants. Norit
products are often used as the final step, either as a
filter cap or as a separate post-filter contactor. If ozone
is used as a pre-oxidant, then the bio-activity of the
GAC is enhanced, usually resulting in an increased
filter service time. Regardless of how the carbon is
applied, Norit can deliver the most appropriate GAC
that will result in optimum performance.
Purity Requirements
Norit activated carbons meet the most stringent
requirements concerning purity and leaching behavior.
They comply with the US Food Chemicals Codex
requirements and meet NSF and AWWA standards.
Details are available upon request.
Treatment Objectives
The major treatment objectives for GAC are the
removal of dissolved organics (both low and high
molecular weight), taste and odor causing compounds,
disinfection by-products, overall organics (DOC, TOC,
UV254 and constituents), biodegradable organics
(AOC and BDOC), pesticides and detergents, etc.
Additionally, GAC removes suspended solids and
residual oxidants such as chlorine and ozone.
Filter Types
Around the world you will find GAC filters using Norit
products. Gravity filters are most common, but
pressure filters are used as well. Both post-filter
contactors and existing (mechanical and/or biological)
filters are used.
• Post-filter contactor
Filters designed to hold only GAC. Typically this is
the last polishing step in the treatment process
prior to the clearwell. Empty Bed Contact Time
(EBCT) is typically from 5-15 minutes.
• Converted existing filters
Replacing anthracite with GAC, thus maintaining
the filtration properties of the filter while adding
the capability of adsorption, results in relatively
short EBCT of