Use of Microorganisms for the Treatment of Trinitrotoluene (TNT) Containing Effluents

The samples including effluents (red and yellow effluent) and sludge (red and yellow sludge) were collected from different locations around Pakistan Ordinance Factory, Wah Cantt., Pakistan. The red effluent contained the highest concentration of trinitrotoluene (TNT), therefore it was used for further studies. A number of bacteria were isolated from these samples by enrichment technique. All these strains were adapted to grow on mineral salt medium (MSM) at different concentrations of TNT (10-100 ppm). All bacterial strains showed observable growth up to 30 ppm. With further increase in the TNT concentration there was decrease in the growth of bacterial strains. The bacterial consortium developed from the TNT contaminated soil successfully removed TNT in liquid cultures after six weeks of incubation in shake flask experiment. TNT removal is a co-metabolic process and needs a co substrate. Various co-substrates like nitrogen sources [NH4NO3, NH4Cl, (NH4)2HPO4], carbon sources (molasses, glucose, corn starch) and surfactant (Tween 80) were used separately and evaluated both in nutrient broth and distilled water at 262 nm. Among all the nitrogen sources used maximum percentage reduction (88.75 %), was recorded in the presence of NH4NO3 and NH4Cl when nutrient broth was used as diluent. Among carbon sources, molasses was identified as the best substrate for TNT removal with percentage reduction as 92.64 %, whereas in the presence of Tween 80 it was found to be 92.46 % when nutrient broth was used as diluent. It can be concluded that the newly isolated bacterial consortium demonstrated the ability to degrade TNT. The formation of the breakdown products, most probably dinitrotoluene, was analyzed by the increase in OD at 462 nm which gave indirect measure of degradation of TNT. The biodegradation was more effective when the nutrient broth was used as diluent as compared to distilled water.