Biologically Active Zone Enhancement (BAZE) for In Situ RDX Degradation in Ground Water

摘要

In 2001, the U.S. Army Engineer Research and Development Center (ERDC) received funding from the Environmental Security Technology Certification Program (ESTCP) to conduct in situ studies validating sodium acetate injection as a means to enhance biological transformation of hexahydro- 1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater. The field demonstration that evaluated the Biologically Active Zone Enhancement (BAZE) process was conducted at the former Nebraska Ordnance Plant (NOP), located near Mead, Nebraska. Runway deicer (sodium acetate) was earlier selected as the organic carbon source during bench-scale studies that used aquifer material collected at NOP. The results of the field demonstration indicated that RDX concentrations were reduced from an average of 256 g/L to below the laboratory detection limit of 0.1 g/L. The field demonstration data also quantified the capital and operation & maintenance (O&M) cost associated with the use of the BAZE process for in situ treatment of RDX contamination in groundwater. The estimated demonstration cost was $74/kgal while the real world cost for a BAZE system was determined to be $27/kgal ($7.40/m3), which is comparable to the cost for a traditional pump-and-treat method. Wells were installed for the field demonstration in September 2003 and pre-treatment groundwater samples were collected in December 2003. The first sodium acetate injection was performed January 2004 and acetate injections/sampling was completed in August 2005. Fifteen rounds of sodium acetate solution were injected and circulated through the treatment system during the course of the study. During each injection event, approximately 200 gallons (757 L) of 13% sodium acetate solution were diluted with groundwater pumped from the extraction well into an in-line mixer resulting in a 0.3% sodium acetate solution. The sodium acetate solution was then equally distributed to both injection wells.