Microbial reduction of dinitrotoluene sulfonates in TNT red water–contaminated soil

Abstract

Large quantities of TNT red water which contained mainly dinitrotoluene sulfonates (DNTS) were produced during the production of TNT, threatening the surrounding environments. In china, about 1.5 × 105 m3 soil was contaminated by TNT red water. So, it is extremely important to remediate the DNTS-contaminated sites. Batch biodegradation tests were conducted to investigate the influence of environmental factors (microorganism dosage, initial DNTS concentration, water/soil ratio, and temperature) on the microbial reduction of DNTS in soil. The biodegradation intermediate metabolites of 2,4-dinitrotoluene-3-sulfonate (2,4-DNT-3-SO3−) and 2,4-dinitrotoluene-5-sulfonate (2,4-DNT-5-SO3−) during the remediation process were determined. Three kinetic models were used to study the biodegradation kinetics of DNTS in soil. Finally, high-throughput sequencing (HTS) technology was applied to identify the microbial communities in soil samples during the bioremediation process. Batch experiments showed that at initial concentration of 500 mg kg−1, 2,4-DNT-3-SO3− and 2,4-DNT-5-SO3− removal efficiencies reached 100% after 25 and 13 days under the following conditions: water/soil ratio of 2:5, microorganism dosage (w/w) of 1%, and temperature of 35 °C. The microbial consortium metabolized 2,4-DNT-3-SO3− and 2,4-DNT-5-SO3− via reductive pathways. The biodegradation processes fitted well with zero-order reaction kinetics at different initial DNTS concentrations. HTS results showed that the bacterial communities were greatly influenced by the DNTS addition. The dominant genus in 2,4-DNT-3-SO3−-contaminated soil were Bacillus, Pseudomonas, Simiduia, Salegentibacter, and Methylohalomonas while that in 2,4-DNT-3-SO3−-contaminated soil were Bacillus, Pseudomonas, Simiduia, Methylohalomonas, Salegentibacter, Pontibacter, and Actinotalea. Microbial consortium showed great DNTS-degrading ability. Bacillus, Pseudomonas, and Simiduia played a major role in biodegradation of 2,4-DNT-3-SO3− and 2,4-DNT-5-SO3− in soil. The microbial consortium tolerated high levels of DNTS found in the soil and degraded the contaminants into more biodegradable forms. The biotreatment technology is effective and has a potential to be use in remediation of TNT red water–contaminated sites.