THM Precursor Removal Efficiency of Regenerated and Virgin Carbon
M. M. Varma
T. A. Stumm
Aqueous chlorine reacts with certain precursors in water to form trihalomethanes (THMS)—suspected carcinogens/mutagens. It is necessary to minimize the concentration of THMs in finished water, either by removing the precursor before chlorination or by removing the THMs by advanced treatment. Granulated activated carbon (GAC) is an accepted procedure for removing the precursor from water. This article evaluates the different methods of regeneration in restoring the quality of the spent carbon and compares the removal efficiency of precursors by virgin and regenerated carbon.
Parallel pilot plant investigations were made using virgin and regenerated carbon. The size of each column was 4" individual diameter and 6' long, with glass reducers at both ends. The carbon depth was 36"—the flow maintained at 2.75 gal/min/sq. ft. Trihalomethane formation potential (THMFP) was measured at the end of 72 hours. The results show that all the three processes restored the carbon through regeneration to near virgin state. Statistical modeling indicates that all regenerated carbons performed alike, however, TOC removal failed to show any distinct correlation with precursor removal.
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