Combined biological–chemical procedure for the mineralization of TNT

Abstract

Contamination of ground and surface water with 2,4,6-trinitrotoluene (TNT) and its biological and chemical transformation products are a persisting problem at former TNT production sites. We have investigated the photochemical degradation of TNT and its aminodinitro-(ADNT) and diaminonitrotoluene (DANT) metabolites using OH-radical generating systems like Fenton and hydrogen peroxide irradiated with UV, in order to compare the degradation and mineralization rate of ADNT- and DANT-isomers with TNT itself. As a result, we find that the aminoderivatives were mineralized much faster than TNT. Consequently, as ADNTs and DANTs are the known dead-end products of biological TNT degradations, we have combined our photochemical procedure with a preceding biological treatment of TNT by a mixed culture from sludge of a sewage plant. This consecutive degradation procedure, however, shows a reduced mineralization rate of the ADNTa and DANTs in the biologically derived supernatant as compared to the pure substances, suggesting that during the biological TNT treatment by sludge competing substrates are released into the solution, and that a more defined biological procedure would be necessary in order to achieve an effective, ecologically and economically acceptable mineralization of TNT from aqueous systems.

Application of advanced oxidation processes for TNT removal: A review

“…Using this coupled reaction process, abiotic, dark-Fenton reaction), TNT mineralization at pH 3 was increased from 47 to 80% using a microbial biomass. Likewise, Kröger et al [102] and Kröger and Fels [103] have studied the possibility of a combining biological-chemical process. However, in contrast to the studies starting with a chemical treatment, these authors presented the concept of a biological reduction of TNT prior to an oxidative chemical treatment by advanced oxidation process (photo-Fenton), which seems to be the most appropriate approach towards mineralization of TNT (unfortunately, no data regarding TOC or COD were available).…”

Advanced Oxidation Processes for Wastewater Treatment: State of the Art

“…However, when an aerobic process was used, more than 30% of the naproxen was retained in the sludge waste, whereas after a photochemical treatment with H 2 O 2 / UV, only a 10% mineralization was achieved. Kröger and Fels (2007) investigated the photochemical degradation of TNT and its aminodinitro-(ADNT) and diaminonitrotoluene (DANT) metabolites. At concentrations of 2.5% H 2 O 2 , for example, this degradation was achieved within 5 h, while at 0.15% the transformation took 24 h. In this case, the TNT concentration was 50 mg/L with a pH in the medium of 3.…”

“…It should be underlined that the compound treated is often employed as a precursor in the synthesis of a pharmaceutical product, which means that it may also be present in the effluent of pharmaceutical plants. Kröger and Fels (2007) also used this process for the mineralization of TNT and its derivatives. A mineralization rate of more than 60% was achieved with concentrations of 10-40 mg/L Fe 2+ to treat a concentration of TNT.…”

Photochemical Degradation of Organic Xenobiotics in Natural Waters

“…To mention just several of them, let us start with the photo-Fenton process. Yardin and Chiron [70] and Kröger and Fels [71] used it for the mineralisation of TNT and its derivatives. Haseneder et al [72] and Santos et al [73] employed the process for the degradation of polyethylene glycol, a substance with a wide range of application in both the industrial and pharmaceutical sectors.…”