Bioremediation of TNT-Contaminated Soil: A Laboratory Study

Abstract

This research presented a bench-scale investigation of an innovative approach to land farming for the bioremediation of 2,4,6-trinitrotoluene (TNT)-contaminated soils. Molasses, which contains sugar, nitrogen, vitamins, and minerals, was used as cosubstrate and this process combines several advantages of conventional land farming with the use of molasses for the biological degradation of TNT and its derivatives. In the optimum treatment, contaminated soil was amended with shredded grass and managed in an operating cycle where it was alternatively flooded with a dilute molasses solution, then drained, passively aerated, and finally tilled when moisture conditions were optimum. Soil TNT concentrations in all treatments receiving molasses were reduced from approximately 4,000-mg/kg levels initially to less than 100 mg/kg in 12 months, and to less than 1 mg/kg in the optimum treatment in this same time. Concentrations of the primary metabolic intermediates and bacterial populations were also tracked. Radiolabeling studies confirmed that the biomass enhanced by the treatments could mineralize approximately 20% of [ 14 C] from a contaminant spike after 22 d. A shredded grass amendment in the optimum treatment was shown to increase moisture retention during aeration phases. The results of this bench-scale study are promising with regard to transferring the process to full-scale applications.

Microbial remediation of nitro-aromatic compounds: An overview

“…Widrig et al (1997) used this method for the bioremediation of TNT contaminated soil by the application of molasses.…”

Evaluation of bioremediation methods for the treatment of soil contaminated with explosives in Louisiana Army Ammunition Plant, Minden, Louisiana

“…Over the years, many new biological methods of bioremediation for explosive contaminated soil have been developed [6]. These methods include soil slurry reactors, composting, land farming, and phytoremediation.…”

“…Soil slurry reactors are designed to optimize mass transfer of nutrients and electron acceptors by using mechanical mixing and aeration [7]. Land farming is a solid-phase treatment process in which contaminated soil is mixed with nutrients and moisture, using periodic mechanical turning of the soil to increase aeration [6]. Composting is similar to land farming but includes additional significant amendments of organic substrates, which are primarily used as the carbon source to promote increased bacterial activity and higher degradation rates [6].…”

“…Land farming is a solid-phase treatment process in which contaminated soil is mixed with nutrients and moisture, using periodic mechanical turning of the soil to increase aeration [6]. Composting is similar to land farming but includes additional significant amendments of organic substrates, which are primarily used as the carbon source to promote increased bacterial activity and higher degradation rates [6]. The use of composting for explosive remediation was reported by Williams [8].…”

“…Conventional composting methods require a large input of natural organic substrates such as straw, woodchips, and livestock manure and relatively small amount of soil is treated. Land farming is a slow process [6,10]. Each method is site specific and has to be evaluated for each site prior to full-scale remediation.…”