Project Report PR-95-07
Extending the effective life of the GAC used to treat well water: Phase II of evaluative study at Mililani
Gordon L. Dugan, Roger S. Fujioka, L. Stephen Lau, Gerald H. Takei, Henry K. Gee, Terra L. McParland, and Holly M. Chu
January 1995
ABSTRACT
Phase II is a continuation of the Phase I study to explore means of extending the effective life of the granular activated carbon (GAC) used in three central Oahu plants established by the Honolulu Board of Water Supply for the removal of volatile organic compounds: TCP, DBCP, and EDB. The Phase II study only concentrated on the Mililani GAC treatment plant, which did not have a measurable concentration of EDB. Isotherms were developed for TCP, which were approximately two orders of magnitude higher than DBCP in Mililani well water, but the results were questionable due to relatively high TCP losses by volatilization. Fourteen laboratory dynamic filtration tests (minicolumn tests) were conducted, eight using a bituminous-based GAC (used in BWSº full-scale treatment plants) and six using a lignite-based GAC. The lignite-based GAC significantly outperformed the bituminous-based GAC, requiring 24% less carbon to remove a unit amount of TCP. Aeration treatment effectively removed TCP and DBCP, but neither aeration nor GAC treatment appeared to appreciably remove natural background organic compounds.