If PAC does not remove tastes and odors, what is a likely explanation?

If PAC does not remove tastes and odors, what is a likely explanation?

• A. It is added too late
• B. It is added too close to the chlorine feed
• C. It is not activated
• D. It is degraded in storage

Answer: (B)

Powdered activated carbon removes tastes and odors by adsorbing the organic molecules that cause them. For adsorption to work well, the carbon must be in contact with the water and the contaminants before disinfection begins, giving enough time for those molecules to attach to the carbon surfaces. If PAC is added too close to the chlorine feed, there isn’t enough contact time before chlorine is introduced. Chlorine can oxidize the organic compounds or compete with adsorption sites on the carbon, reducing the carbon’s ability to capture the taste- and odor-causing molecules. The result is poor removal of tastes and odors. So the likely explanation is that PAC was added too close to the chlorine feed; placing it earlier in the process ensures sufficient contact time for adsorption before disinfection.

Powdered activated carbon removes tastes and odors by adsorbing the organic molecules that cause them. For adsorption to work well, the carbon must be in contact with the water and the contaminants before disinfection begins, giving enough time for those molecules to attach to the carbon surfaces.

If PAC is added too close to the chlorine feed, there isn’t enough contact time before chlorine is introduced. Chlorine can oxidize the organic compounds or compete with adsorption sites on the carbon, reducing the carbon’s ability to capture the taste- and odor-causing molecules. The result is poor removal of tastes and odors.

So the likely explanation is that PAC was added too close to the chlorine feed; placing it earlier in the process ensures sufficient contact time for adsorption before disinfection.