Comparative Demonstration of Active and Semi-Passive In Situ Bioremediation Approaches for Perchlorate-Impacted Groundwater at Longhorn Army Ammunitions Plant

摘要

Perchlorate is an inorganic anion and a primary ingredient in solid rocket propellant. It exhibits high solubility and mobility in water and has been identified in groundwater at numerous sites across the United States. Enhanced in situ bioremediation (EISB) of perchlorate-impacted groundwater offers a simple approach to treat and destroy perchlorate in the subsurface. This report describes work conducted to demonstrate/validate the use of a semi- passive EISB approach at the Longhorn Army Ammunition Plant (LHAAP) in Texas. The semi-passive EISB approach involves periodic (e.g., two or three times per year) delivery of electron donor to create a biologically active zone for the purposes of promoting perchlorate biodegradation either as a biobarrier across a plume or for treatment of other target treatment zones. The semi-passive biobarrier approach involves the use of extraction and injection wells to add and mix the electron donors in the subsurface. Once electron donor is delivered, recirculation is shut off, and the electron donor promotes in situ biological treatment of the perchlorate. The overall objective of this work was to demonstrate the efficacy of the semi-passive approach to EISB to generate accurate full-scale design and cost information for widespread technology consideration and application. The demonstration was designed to evaluate performance objectives, including: (1) the ease of installation of system components, (2) the ease of electron donor delivery events, (3) the enhancement of microbiological activity and the reduction in perchlorate concentrations, (4) the ease of performance monitoring and validation, and (5) the radius of influence and distance for degradation.