• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.198-205
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• 2005

This study was carried out to investigate the removal of TNT (2,4,6-trinitrotoluene) in the batch and continuous type microcosm systems consisting of marsh and pond. First, the batch reactor study showed that TNT (10 mg/L) was completely removed in the marsh and pond system within 20 days. The major reductive metabolites of TNT include 4-amino-2,6-dinitrotoluene (4-ADNT), 2-amino-4,6-dinitrotoluene (2-ADNT), 2,4-diamino-6-nitrotoluene (2,4-DANT), and 2,6-diamino-4-nitrotoluene (2,6-DANT). These metabolites concentration also decreased during further treatment. The continuous reactor systems combining marsh and pond indicated the similar pattern of TNT degadation and the metabolites production. Among the continuous reactor combinations, marsh-pond system showed more stable TNT removal and metabolites production. The toxicity of the effluent from the continuous system was examined by Microtox Assay using Vibrio fischeri. The result showed that the effluent toxicity was reduced below toxicity endpoint ($EC_{50}$) after continuous marsh pond system, indicating that metabolites of TNT are less toxic than TNT itself. Based on the results, TNT contaminated wastewater can be efficiently treated using marsh and pond wetland systems.

• Journal of Environmental Health Sciences
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• v.30 no.3
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• pp.214-220
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• 2004

The microcosm type wetland systems were constructed in order to treat wastewater contaminated with parathion. The microcosm reactor consisted of marsh and pond type. The experiment was carried out using batch (marsh or pond) and continuous (marsh-pond and pond-marsh type) systems. In the batch reactor, marsh-type wetland completely removed parathion in water within 8 days, while pond reactor removed 97% of parathion during the same period. During parathion degradation, the amount of 4-nitrophenol production, one of the metabolites from parathion degradation, was higher in marsh-type batch reactor. In the continuous systems, both marsh-pond and pond-marsh combination systems effectively removed parathion from water, and the production of 4-nitrophenol was also minimal. In the extraction experiment, the parathion and its metabolite were not found in the wetland soil and the plant. In order to achieve both aerobic and anaerobic conditions, the continuous wetland system combining marsh and pond type can be the alternative for the non-point source pollutants such as parathion pesticide.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.41-49
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• 2022

This study utilized citric acid as a floating agent in biological denitrification process and assessed its role under different carbon supplying conditions. Several microcosm tests including citric acid active (CAA), precipitating tablet release active (PTRA) and floating tablet release active (FTRA) were conducted to evaluate nitrate denitrification efficacy. In CAA reactors, nitrate removal was accompanied by the formation of denitrification by-products such as nitrite and nitrous oxide, with the extent of nitrate removal being proportional to citric acid concentration. These results suggest that citric acid induced heterotrophic biological denitrification. PTRA reactor that incorporated CAA and the same electron donor showed a similar denitrification efficiency to CAA reactor. FTRA reactor, which contained the same amount of fumarate as PTRA, enhanced denitrification by 7% as compared to the PTRA reactor. The overall results of this work indicate that surplus citric acid can be efficiently utilized in heterotrophic denitrification.

• Journal of Life Science
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• v.24 no.10
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• pp.1110-1117
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• 2014

Tidal flats are continuously contaminated by human activities. This study assessed the bioremediation efficiency of tidal flat soil using microcosm reactors and microorganisms originating from the tidal area. We screened 135 bacterial strains that produce extracellular enzymes from the tidal area located in the North port of Incheon bay. Two bacterial strains (Pseudoalteromonas sp. and IC35 Halothiobacillus neapolitanus IC_S22) were selected and used in the microcosm reactors, which were specially designed to functionally mimic the ecological conditions of the tidal flats. Pseudoalteromonas sp. IC35 was selected based on its relatively high activity of the enzymes amylase, cellulose, lipase, and protease. Halothiobacillus neapolitanus IC_S22 was selected for oxidation of sulfur. The M1 and M2 microcosm reactors were operated by continuous feeding of seawater under the same conditions, but M2 was first inoculated with Pseudoalteromonas sp. IC35 before the seawater feeding. The initial COD in both the M1 and M2 microcosm reactors was 320 mg/l. The final COD was 21 mg/l (M1) and 7 mg/l (M2). The M3 and M4 microcosm reactors were operated by continuous feeding of seawater under the same conditions, but M4 was first inoculated with H. neapolitanus IC_S22. The initial sulfate concentration in both the M3 and M4 microcosm reactors was 660 mg/l, and the maximum sulfate concentration was 1,360 mg/l (M3) and 1,600 mg/l (M4).