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|Title:||Microbial requirements for in situ biotreatment of explosives|
|Authors:||Hinds Junior College.|
Alcorn State University.
Installation Restoration Research Program (U.S.)
Davis, William M.
Myrick, Glenn B.
In situ biotreatment
Natural microbial communities
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: The biological destruction of explosives in soil depends upon several factors in addition to the presence of suitable microorganisms or microbial consortia. Successful bioremediation requires sufficient moisture, nutrients, and co-substrates (additives) at optimal concentrations. Enhancement of bioavailability by stimulating increased desorption of the contaminant from soils may also be required. Objectives of this study were to develop simple tests to determine the chemical compounds required to stimulate TNT destruction by native microorganisms and the specific combination of additives required to support the most efficient destruction of TNT under static conditions simulating surface application of additives in the field. A three-tiered test system was developed to meet these objectives. Tier I consisted of a previously developed screening test; this was used to determine the presence of TNT-degrading microorganisms and cosubstrates required to support microbial degradation. Tier II consisted of a shake flask test that was developed to determine the combinations of nutrients, cosubstrates, and/or surfactants required to enhance TNT removal with minimal production of undesirable products. Results of shake flask tests indicated that low levels of nutrients generally enhanced the number of microorganisms while supporting and stimulating the treatment process. High levels of nutrients sometimes stimulated, but at other times inhibited, growth and treatment. Addition of the surfactant Tween 80 sometimes stimulated treatment. Addition of the cosubstrates toluene or acetate sometimes inhibited growth slightly when used with nutrients, but inhibition was commonly offset when Tween 80 was used in combination with the cosubstrates. Treatment effectiveness and the required concentrations of additives were determined in the Tier III test - a static cell test developed specifically for this purpose. Results of static cell testing indicated that for Hastings soil, weekly dosing with a high nutrient solution produced rapid and nearly complete disappearance of TNT over a 7-month period. Study results suggest that when examining the feasibility of explosives biotreatment using surface application of additives, site-specific factors operate to determine microbial requirements for inorganic nutrients and cosubstrates, as well as the possible need for a surfactant. Consequently, microbial requirements must be evaluated on a site-specific basis. Therefore, the tiered testing approach is ideally suited for optimizing treatment conditions prior to pilot-level tests.
|Appears in Collections:||Technical Report|