• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.236-241
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• 2016

This study conducted a screening-level ecological risk assessment for heavy metals in dredged sediment for recycling in terrestrial environment. Toxicological information of six heavy metals (i.e., Cu, Zn, Cd, Pb, Cr, and Ni) was collected from ECOTOX of US Environmental Protection Agency, and screened and qualified for the use in the screening-level ecological risk assessment. According to the number of terrestrial ecological receptors for which toxicological information is available, PNEC (Predicted No Effect Concentration) of each heavy metal was derived using either stochastic approach (for Cu, Zn, and Cd), or deterministic approach (for Pb, Cr, and Ni). Hazard quotients of the six heavy metals were derived for a field-collected dredged sediment using the PNEC derived and the PEC (Predicted Environmental Concentration) determined for the dredged sediment. The HQs of Cu, Zn, Cr, Pb and Ni were higher than unity indicating a possibility of ecological risk of the five heavy metals when the dredged sediment is applied in terrestrial environment. Accordingly, remediation processes or a higher-level ecological risk assessment would be needed for the recycling of the material.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.4
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• pp.411-419
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• 2003

Dredged material during Masan Bay cleaning in 1990-1994 was deposited in Gapo area. The site provides an ideal experimental condition to monitor environmental remediation and benthic ecosystem stabilization processes after the disturbance. Sea water samples were taken during one tidal cycle in one hour interval from Oct. 2001 to Apr. 2002 (4 times) to estimate the organic matter and nutrient fluxes in Gapo area. Hourly material fluxes were estimated from the water balance estimated from 3 dimensional topography of Gapo area and from material concentration. Net material fluxes were estimated from the difference between total influx and total outflux during one tidal cycle. Chemical oxygen demand showed net outflux in Nov. 2001, Dec. 2001 and Apr. 2002 (2.2∼3.9 g m$\^$-2/ h$\^$-1/) and showed net influx in Mar. 2002 (1.4 g m$\^$-2/ h$\^$-1/). Ammonium showed net outflux during the study (0.1∼118 mg m$\^$-2/ h$\^$-1/m-2h-I). According to this investigation, Gapo area was a source rather than a sink of organic matter. However, the variability of the material fluxes was high so that a long term study may be required.

• Korean Journal of Microbiology
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• v.47 no.4
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• pp.356-363
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• 2011

The accidental releases of total petroleum hydrocarbons (TPH) due to oil spills frequently ended up with soil and ground water pollution. TPH may be degraded through physicochemical and biological processes in the environment but with relatively slow rates. In this study an attempt has been made to develop an integrated chemical and biological treatment technology in order to establish an efficient and environment-friendly restoration technology for the TPH contaminated soils. A Fenton-like reaction was employed as a preceding chemical treatment process and a bioaugmentation process utilizing a diesel fuel degrader consortium was subsequently applied as a biological treatment process. An efficient chemical removal of TPH from soils occurred when the surfactant OP-10S (0.05%) and oxidants ($FeSO_4$ 4%, and $H_2O_2$ 5%) were used. Bioaugmentation of the degrader consortium into the soil slurry led to an increase in their population density at least two orders of magnitude, indicating a good survival of the degradative populations in the contaminated soils ($10^8-10^9$ CFU/g slurry). TPH removal efficiencies for the Fenton-treated soils increased by at least 57% when the soils were subjected to bioaugmentation of the degradative consortium. However, relatively lower TPH treatment efficiencies (79-83%) have been observed in the soils treated with Fenton and the degraders as opposed to the control (95%) that was left with no treatment. This appeared to be due to the presence of free radicals and other oxidative products generated during the Fenton treatment which might inhibit their degradation activity. The findings in this study will contribute to development of efficient bioremediation treatment technologies for TPH-contaminated soils and sediments in the environment.

• Journal of Soil and Groundwater Environment
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• v.14 no.2
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• pp.33-44
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• 2009

The objective of the study was to develop a hybrid technology integrating biological and physicochemical technologies to efficiently remediate arsenic contaminated lands such as abandoned mine area. The tailing soil samples contaminated with As at a high level were obtained from Songchon abandoned mine, and the content of arsenic and heavy metals as well as physicochemical properties and mineral composition were investigated. In addition, two sets of sequential extraction methods were applied to analyze chemical speciations of arsenic and heavy metals to expect their leachability and mobility in geoenvironment. Based on these geochemical data of arsenic and heavy metal contaminants, column-type experiments on the bioleaching of arsenic were undertaken. Subsequently, experiments on the hybrid process incorporating bioleaching and electrokinetics were accomplished and its removal efficiency of arsenic was compared with that of the individual electrokinetic process. With the results, finally, the feasibilty of the hybrid technnology was evaluated. The arsenic removal efficiencies of the individual electrokinetic process (44 days) and the hybrid process incorporating bioleaching (28 days) and electrokinetics (16 dyas) were measured 57.8% and 64.5%, respectively, when both two processes were operated in an identical condition. On the contrary, the arsenic removal efficiency during the bioleaching process (28 days) appeared relatively lower (11.8%), and the result indicates that the bioleaching process enhanced the efficacy of the electrokinetic process as a result of mobilization of arsenic rather than removed arsenic by itself. In particular, the arsenic removal rate of the electrokinetics integrated with bioleaching was observed over than 2 times larger than that obtained by the electrokinetics alone. From the results of the study, if the bioleaching which is considered a relatively economic process is applied sufficiently prior to electrokinetics, the removal efficiency and rate of arsenic can be significantly improved. Consequently, the study proves the feasibility of the hybrid process integrating both technologies.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.374-381
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• 2015

Occurrences of coastal dredged materials are ever increasing due to port construction, navigational course maintenance and dredging of polluted coastal sediments. Ocean dumping of the coastal dredged materials has become virtually prohibited as London Treaty will be enacted as of the year 2012. It will be necessary to treat and recycle the dredged materials that may carry organic pollutants and heavy metals in a reasonable and effective process: collection of the dredged materials, liquid and solid separation, and treatment of organic compounds and heavy metals. In this study we have developed a continuous bioreactor system that can treat a mixture of silt and particulate organic matter using a microbial consortium (BM-S-1). The steady-state operation conditions were: pH (7.4-7.5), temperature ($16^{\circ}C$), DO (7.5-7.9), and salt concentration (3.4-3.7%). The treatment efficiencies of SCOD, T-N and T-P of the mixture were 95-96%, 92-99%, and 79-97%. The system was also effective in removal of heavy metals such as Zn, Ni, and Cr. Levels of MLSS during three months operation period were 11,000-19,000 mg/L. Interestingly, there was little sludge generated during this period of operation. The augmented microbial consortium seemed to be quite active in the removal of the organic component (30%) present in the dredged material in association with indigenous bacteria. The dominant phyla in the treatment processes were Proteobacteria and Bacteroidetes while dominant genii were Marinobacterium, Flaviramulus, Formosa, Alteromonadaceae_uc, Flavobacteriaceae_uc. These results will contribute to a development of a successful bioremediation technology for various coastal and river sediments with a high content of organic matter, inorganic nutrients and heavy metals, leading to a successful reuse of the polluted dredged sediments.

• Journal of Wetlands Research
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• v.26 no.2
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• pp.168-181
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• 2024

Constructed wetlands (CWs) deliver a range of ecosystem services, including the removal of contaminants, sequestration and storage of carbon, and enhancement of biodiversity. These services are facilitated through hydrological and ecological processes such as infiltration, adsorption, water retention, and evapotranspiration by plants and microorganisms. This study investigated the correlations between microbial populations, soil physicochemical properties, and treatment efficiency in a horizontal subsurface flow constructed wetland (HSSF CW) treating runoff from roads and parking lots. The methods employed included storm event monitoring, water quality analysis, soil sampling, soil quality parameter analysis, and microbial analysis. The facility achieved its highest pollutant removal efficiencies during the warm season (>15℃), with rates ranging from 33% to 74% for TSS, COD, TN, TP, and specific heavy metals including Fe, Zn, and Cd. Meanwhile, the highest removal efficiency was 35% for TOC during the cold season (≤15℃). These high removal rates can be attributed to sedimentation, adsorption, precipitation, plant uptake, and microbial transformations within the CW. Soil analysis revealed that the soil from HSSF CW had a soil organic carbon content 3.3 times higher than that of soil collected from a nearby landscape. Stoichiometric ratios of carbon (C), nitrogen (N), and phosphorus (P) in the inflow and outflow were recorded as C:N:P of 120:1.5:1 and 135.2:0.4:1, respectively, indicating an extremely low proportion of N and P compared to C, which may challenge microbial remediation efficiency. Additionally, microbial analyses indicated that the warm season was more conducive to microorganism growth, with higher abundance, richness, diversity, homogeneity, and evenness of the microbial community, as manifested in the biodiversity indices, compared to the cold season. Pollutants in stormwater runoff entering the HSSF CW fostered microbial growth, particularly for dominant phyla such as Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes, which have shown moderate to strong correlations with specific soil properties and changes in influent-effluent concentrations of water quality parameters.