highest values established among the 130 compounds that they tested; GAC is very
effective for the removal of DEHP from drinking water.
6.6 PCBs
In the USEPA report [51], two studies were reported for PCB-1221 and PCB-1232.
The K value determined for PCB-1221 was 1922μg/g (L/μg)
1/n , and the K value for
PCB-1232 was 4067μg/g (L/μg)
1/n . Both mixtures are among the lesser chlorinated
groups containing 21 and 32% chlorine, respectively. Relative to other PCB mixtures, they are more hydrophilic and hence would have lower K values than the
commercial PCB mixtures, Aroclor 1242, 1248, 1254, and 1260. The most troublesome PCB environmental mixtures tend to be derivatives of this later group of
compounds; therefore, GAC should be a very effective method for removal of
environmental PCB compounds from drinking water.
6.7 Dioxin
Dioxin is not water soluble; hence it is not likely to be present in untreated drinking
water unless it would be attached to sediment in raw water. Because most conventional water treatment methodologies such as coagulation-sedimentation and filtration are effective in removing sediment, it is likely that these processes would be
very effective in the removal of the contaminant, dioxin.
6.8 Alkylphenols and Alkylphenol Ethoxylates
GAC is best used for removal of these contaminants from drinking water. Previous
laboratory-scale testing for removal of nonylphenol with GAC has yielded K values
of 19,406 at a water pH of 7.0 [9]. For consistency of removal of synthetic organic
chemicals, GAC, POU-GAC, and PAC are recommended for small system compliance. GAC devices include pour-through for treating small volumes, faucet-mounted
for POU, in-line for treating large volumes at several faucets, and high volume
commercial units for treating community water supply systems. Careful selection of
the type of carbon is based on the specific contaminants in the water and the
manufacturer’s recommendations. Site-specific conditions may affect the percentage
removal using these techniques, including the presence of “competing” contaminants. Source water-specific testing will be needed to ensure adequate removal. For
GAC, surface waters may require pre-filtration. PAC is most applicable to those
systems that already have a process train including mixing basins, flocculation,
flotation clarification (or sedimentation clarification), and filtration.
190
N. K. Shammas et al.
effective for the removal of DEHP from drinking water.
6.6 PCBs
In the USEPA report [51], two studies were reported for PCB-1221 and PCB-1232.
The K value determined for PCB-1221 was 1922μg/g (L/μg)
1/n , and the K value for
PCB-1232 was 4067μg/g (L/μg)
1/n . Both mixtures are among the lesser chlorinated
groups containing 21 and 32% chlorine, respectively. Relative to other PCB mixtures, they are more hydrophilic and hence would have lower K values than the
commercial PCB mixtures, Aroclor 1242, 1248, 1254, and 1260. The most troublesome PCB environmental mixtures tend to be derivatives of this later group of
compounds; therefore, GAC should be a very effective method for removal of
environmental PCB compounds from drinking water.
6.7 Dioxin
Dioxin is not water soluble; hence it is not likely to be present in untreated drinking
water unless it would be attached to sediment in raw water. Because most conventional water treatment methodologies such as coagulation-sedimentation and filtration are effective in removing sediment, it is likely that these processes would be
very effective in the removal of the contaminant, dioxin.
6.8 Alkylphenols and Alkylphenol Ethoxylates
GAC is best used for removal of these contaminants from drinking water. Previous
laboratory-scale testing for removal of nonylphenol with GAC has yielded K values
of 19,406 at a water pH of 7.0 [9]. For consistency of removal of synthetic organic
chemicals, GAC, POU-GAC, and PAC are recommended for small system compliance. GAC devices include pour-through for treating small volumes, faucet-mounted
for POU, in-line for treating large volumes at several faucets, and high volume
commercial units for treating community water supply systems. Careful selection of
the type of carbon is based on the specific contaminants in the water and the
manufacturer’s recommendations. Site-specific conditions may affect the percentage
removal using these techniques, including the presence of “competing” contaminants. Source water-specific testing will be needed to ensure adequate removal. For
GAC, surface waters may require pre-filtration. PAC is most applicable to those
systems that already have a process train including mixing basins, flocculation,
flotation clarification (or sedimentation clarification), and filtration.
190
N. K. Shammas et al.