NDMA Treatment by Sequential GAC Adsorption and Fenton-Driven Destruction

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Abstract
N-nitrosodimethylamine (NDMA) is a highly toxic environmental contaminant that was first detected in groundwater tainted by rocket fuel manufacturing wastes. NDMA is also a by-product of certain industrial processes including the chlorination of treated water and wastewater. Water treatment by carbon adsorption is costly because NDMA partitions only sparingly to carbon and frequent carbon replacement or regeneration is required. If activated carbon could be regenerated cheaply and quickly in place, NDMA adsorption on carbon, an easily implemented technology, could become attractive. In this study, the feasibility of adsorbing NDMA onto carbon followed by in-place carbon regeneration using Fenton's reagent was assessed. Batch and column tests indicated that the concentration of sorbed NDMA can be lowered to nondetectable levels in hours using reasonable hydrogen peroxide and iron concentrations. Three-log destruction of sorbed NDMA loaded to 1.04 mg NDMA/g carbon was achieved in approximately 12 h. Results of readsorption studies and modified iodine number tests indicated that the aggressive regeneration treatment results in little loss of carbon adsorptive capacity. The destruction efficiency of Fenton's reagents depended on pH and hydrogen peroxide concentration, although little advantage was obtained at very high hydrogen peroxide concentrations. Iron solubility and availability for participation in Fenton's reaction was enhanced by addition of EDTA at near neutral pH, but the NDMA destruction efficiency was greater in a comparable system without the ligand at pH 2.