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In order to improve the water quality in shrimp aquaculture operated under low-salinity conditions, a sequencing batch reactor (SBR) was tested for treatment of the wastewater. This water from the backwash of a single-bead filter from the Waddell Mariculture Center, South Carolina, contained high concentrations of carbon and nitrogen and was successfully treated using the SBR. By operating the reactor sequentially in aerobic, anoxic and aerobic modes, nitrification and denitrification were achieved, as well as removal of carbon. Specifically, the initial chemical oxygen demand (COD) concentration of 1201 mg l −1 was reduced to 32 mg l −1 within 8 days of reactor operation. Ammonia in the sludge was nitrified within 3 days. The denitrification of nitrate was achieved by the anoxic process and total removal of nitrate was observed.

A laboratory study was conducted to determine whether tetryl (2,4,6-trinitrophenlymethylnitramine) contaminated soil could be bioremediated using a sequencing batch soil slurry reactor (SBR) operated under anoxic–aerobic sequence. The results indicated that tetryl was co-metabolically converted to aniline under anoxic conditions with molasses as the growth substrate. The gas chromatographic/mass spectrometric analysis of the soil slurry showed various metabolites, identified as trinitrobenzeneamine, dintrobenzenediamine, nitroaniline and aniline. Aniline was not metabolized further under anoxic conditions. When the soil slurry reactor was operated under aerobic conditions, the aniline concentration was reduced to below the detection limit (0.05 ppm). This metabolic conversion of tetryl is probably of value in the treatment of tetryl-contaminated soil and ground water, such as those found at the Joliet army ammunition plant site in Illinois and the Iowa army ammunition plant site in Burlington, Iowa.

Metabolism of nitroaromatic compounds by a Klebsiella pneumoniae isolated from a regional wetland was studied. When it was grown with nitrophenol as the sole nitrogen source, the isolate had the metabolic capability of transforming nitrophenol to phenol; however, it did not use nitrophenol as the sole carbon source. The metabolic pathway showed that the K. pneumoniae reduced the nitro group to an amino group forming aminophenol as a major metabolite. This aminophenol was oxidatively deaminated to phenol. For every mole of nitrophenol metabolized, 1 mol of phenol was produced and the phenol did not undergo further metabolism. The isolate also used several other nitroaromatic compounds including nitrotoluenes and nitrobenzenes as its nitrogen source. Even though this organism did not degrade the nitroaromatics completely, it may be useful in degrading nitroaromatics in contaminated soil and water containing other aromatic degraders in a syntrophic condition in nature.

The biodegradation of No. 2 diesel fuel under anaerobic conditions was investigated using anaerobic soil slurry reactors. Soil samples were collected from a diesel spill site, where the diesel spill has migrated to vadose zone. The purpose of this study was to find out which of the various groups of anaerobic bacteria present in the study site will degrade the petroleum hydrocarbons in the soil. The various anaerobic groups included sulfate-, nitrate-reducing, methanogenic, and mixed electron acceptor conditions. The results indicated enhanced biodegradation of diesel fuel under all conditions compared to no electron-supplemented reactor (passive bioremediation). However, the rate of diesel degradation was the highest under mixed electron acceptor conditions followed in order by sulfate-, nitrate-reducing, and methanogenic conditions. Under mixed electron acceptor condition, 80.5% removal of diesel fuel was achieved within 290 days. While under sulfate-reducing condition 55% degradation of diesel fuel was observed for the same period. This study showed that the mixed heterogeneous microbial population of the contaminated site has the metabolic capability to degrade diesel fuel.

This research paper presents two bioremediation technologies for the treatment of explosives-contaminated soil. The technologies include soil slurry reactor, and in situ bioremediation. Both bioremediation technologies showed promising results and these treatment methods used co-metabolic process with molasses as a co-substrate for bacterial growth. The soil slurry reactor removed the explosive contaminants present in the soil within three weeks of incubation period. The in situ treatment method also removed all the explosives present in the soil, but the treatment time was approximately 12 months. Each of the bioremediation methods described in this study has advantages and disadvantages. The major advantage in the soil slurry reactor method is the short treatment time, but the disadvantage is that it is labor intensive and expensive due to the excavation of soil, operation of slurry reactors, and post-treatment costs. The in situ treatment method has the advantage of lower treatment costs, but the disadvantage is the treatment time, which is considerably longer.

A laboratory study was conducted to study the feasibility of removing explosives in contaminated soil under anaerobic conditions. Anaerobic enrichment cultures were prepared from soil samples under various electron-accepting conditions, namely, sulfate-reducing, methanogenic, and nitrate-reducing conditions. The sulfate-reducing condition was very effective in removing all of the explosive compounds from the soil. The sulfate-reducing consortium removed 100% of 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB) within 10–15 days of incubation and removed 75 to 95% of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX), within 21 days of incubation. The consortium used explosive compounds as the nitrogen source, however, it did not use these compounds as the sole carbon source. The various metabolites obtained from TNT metabolism were 4-amino-2,6-dinitrotoluene (4-A-2,6-DNT), 2,4-diamino-6-nitrotoluene (2,4- d -6-NT), and 2-methyl pentanoic acid. This sulfate-reducing consortium was further studied for its usefulness in removing TNT at the contaminated site. The results showed that the consortium can remove TNT under 5% and 10% soil slurry conditions. This laboratory study demonstrated that under anaerobic conditions, sulfate-reducing bacteria can be useful in the bioremediation of contaminated soil with TNT and other explosives.