Remediation of TNT-contaminated water by using industrial low-cost residue pine bark

Sammanfattning: In the process of demilitarization of explosives, army ammunition plants generate a waste stream known as pink water. The principal component of the wastewater is the nitro-aromatic compound 2,4,6-trinitrotoluene (TNT). Although the persistence of TNT when dissolved in surface water is very limited due to its susceptibility to photo- and biotransformation, discharge of pink water to the environment has been prohibited in Sweden, the U.S. and many other countries for decades because of the toxicity of the compound and its metabolites to various ecological receptors.The most frequently used method for treatment of pink water in Sweden today is adsorption on activated carbon, which as well as being costly, creates a sludge that must be incinerated off site.In many countries, the timber industry residue pine bark is discarded and has no high value application. The overall aim of this thesis was to investigate the potential of pine bark for the removal of TNT from contaminated water such as pink water. Several batch studies and a column experiment were conducted. Acetonitrile extraction of pine bark and 16S rRNA sequencing for analysis of the indigenous bacterial community of pine bark were used to investigate its performance in the treatment of pink water.The results show that pine bark has great potential as an adsorbent medium for TNT from contaminated pink water. Simultaneous use of biotransformation and adsorption methods was shown to be an improvement over adsorption alone for the removal of TNT from contaminated water bodies. Pine bark showed higher affinity towards the amino metabolites of TNT than for TNT itself. Molecular analysis of the indigenous microbial community of pine bark and chemical analysis of its acetonitrile extracts provided evidence for its ability to biotransform TNT and its metabolites. The efficiency of the transformation was enhanced by the addition of glucose and/or inoculum.Overall, this work demonstrates the versatility of this organic industrial residue with respect to pink water treatment. Not only does it have a high affinity towards TNT and its amino metabolites, but its native microbial community even in the absence of external inoculation can also be taken advantage of, opening new possibilities for remediation of pink water.