• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.642-649
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• 2007

The effectiveness of add-on tertiary treatment processes for the polishing of the effluent of a biological nutrient removal (BNR) system from a modified $A^2/O$ process has been examined under the field condition with pilot-scale plants. The add-on treatment processes of 1) combined biofilm anoxic reactor and sand filtration, and 2) two-stage denitrification filter had been operated with various operating conditions. The experimental results indicated that two-stage denitrification filter could produced a better polished tertiary effluent. Filtration rate of $150m^3/m^2{\cdot}d$ for the 2-stage denitrifying filter could decrease the nitrate removal probably due to shorter detention time that caused insufficient reaction for denitrification. Two stage denitrification filter operated with M/N ratio of 3.0 and filtration rate of $100m^3/m^2{\cdot}d$ produced the tertiary effluent with nitrate and SS concentraitons of 2.8 mg/L and 2.3 mg/L, respectively. When the operating temperature reduced $30^{\circ}C$ to $18^{\circ}C$, $NO_3{^-}-N$ removal efficiency decreased from 73% to 68%.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.338-347
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• 2005

Horizontal-Flow Roughing Filtration (HRF) is one of altemative pretreatment methods e.g. prior to Slow Sand Filtration (SSF). However, some of its limitations are that the effluent quality drops drastically at higher turbidity (>200 NTU) and at higher filtration rate (>1 m/h). To overcome these drawbacks, we suggested Direct Horizontal-Flow Roughing Filtration (DHRF), which is a modified system of Horizontal-Flow Roughing (HRF) by addition of low dose of coagulant prior to filtration. In this study to optimize the DHRF configuration, a conceptual and mathematical model for the coarse compartment has been developed in analogy with multi-plate settlers. Data from simple column settling test can be used in the model to predict the filter performance. Furthermore, the model developed herein has been validated by successive experiments carried out. The conventional column settling test has been found to be an handy and useful to predict the performance of DHRF for different raw water characteristics (e.g. coagulated or uncoagulated water, different presence of organic matter, etc.) and different inital process conditions (e.g. coagulant dose, mixing time and intensity, etc.). An optimum filter design for the coarse compartment (grain size 20mm) has been found to be of 3 m/h filtration rate with filter length of 4-4.5 m.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.356-368
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• 2003

Water quality of effluent from wastewater treatment plants (WWTPS) was reviewed to examine the feasibility of agricultural reuse using USEPA and WHO guidelines. It might meet the guidelines for BOD and SS, however, the most critical microbiological concentration was too high and further treatment is required. The pilot study of three treatments were performed to reduce microbiological concentrations. The UV irradiation was proved to be very effective in disinfection of secondary level effluent, and about 30 mW ${\cdot}$ s/$cm^2$ of dose was suggested to meet the even most stringent USEPA guidelines. Slow sand filter demonstrated effective removal of bacteria, and effluent concentration of total coliform (TC), fecal coliform (FC), and E. coli. dropped from about 10,000/100 mL to 300, 200, and 150 MPN/100 mL, respectively, showing over 95% removal. These level of bacterial concentration sufficiently meet the WHO guidelines ($10^3\;{\sim}\;10^5$ FC/100 mL), and could meet the more stringent USEPA guidelines (200 FC/100 mL) if properly applied. Slow sand filter also provided about 50% removal of SS, turbidity, and BOD in addition to bacterial removal. The removal efficiency of pond system was relatively poor, but still showed over 85% removal and effluent concentration of TC, FC, and E. coli was all below 10,000/100 mL. The pond system alone could meet the WHO guidelines, but hardly meet the USEPA guidelines and further treatment might be necessary. Overall, three methods evaluated in the study treat the effluent to meet the WHO microbiological guidelines for agricultural reuse. The UV disinfection and slow sand filter might also could the USEPA guidelines, while the pond system can hardly meet the USEPA guidelines if applied alone. The WHO and USEPA guidelines were made based on data from upland field agricultural system and may not be directly applicable to the paddy field agricultural system. Therefore, national standards for agricultural reuse of reclaimed water should be made considering domestic agricultural systems as well as international guidelines. Also, further investigation is recommended to develop optimum and feasible treatment measures for agricultural reuse of effluent from WWTPs.

• Journal of Aquaculture
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• v.10 no.3
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• pp.261-271
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• 1997

Ammonia removal capacities of five submerged filter media, 2~3mm sand, 30~50mm gravel, 20~40mm coral sand, polythylene net, and corrugated plastic plate in a seawater recirculating system were tested. A rotating biological contactor (RBC) was also tested for comparison. Oxygen consumption rates were measured along with the ammonia removal efficiencies. The ammonia concentrations in the system were maintained from 0.052 to 0.904 mg/l (mean 0.338$\pm$0.219 mg/l) and the water temperature was ranged from 19.2 to $21.4^{\circ}C\;(mean 20.2^{\circ}C\pm0.58^{\circ}C$). The 1/2-order kinetic model (Y:g/$m^3$/day) and the mean ammonia removal rates (g/$m^3$/day) of the filter media were : Sand : Y=135.5X0.5-25.1(r2=0.8110), 45.1 Coral sand : Y=125.1X0.5-33.0 (r2=0.7307), 31.8 Polyethylene net : Y=87.4X0.5-20.1 (r2=0.6780), 25.2 Corrugated plastic plate : Y=87.4X0.5-20.1(r2=0.5206), 19.2 Gravel : Y=4307X0.5-5.5 (r2=0.2596), 17.1 RBC : Y=127.6X0.5-33.4 (r2=0.7146), 32.8 where X is the concentration of ammonia. Oxygen consumption rates well corresponded to the ammonia removal capacities of each filter medium, thus the sands showing the highest value (442g/$m^3$/day) followed by coral sands (291.1g/$m^3$/day), polyethylene nets (236.9g/$m^3$/day), gravels (135.6g/$m^3$/day) and corrugated plastic plates (134.2g/$m^3$/day). Oxygen consumption rate of the RBC was unable to measure because of the characteristics of the structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.445-450
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• 2008

Recently, environmental and ecological approaches is in progress in urban stream, especially the guarantee of instream flow becomes very important. In this paper, it is suggested that water volume estimation method utilizing the topographical shape data obtained by field investigation and satellite image to manage the urban stream efficiently. The data obtained at Gap River is the study area are analysed and those results are as belows. First, surveying to investigate topographic shape characteristics of urban stream is carried out. In details, the gradient characteristics from water surface to bottom in case of sand area and in case of grass area are 0.013 and 0.065 respectively. In conclusion, the gradient characteristic of grass area is five times bigger than that of sand area. Besides, IKONOS image is classified by spectrum analysis and Minimum Distance Method and the sand area extraction method by the generalization method as Median filter is suggested to calculate water volume. Finally, mapping process on the sand area extracted from the topographical shape field data in river and satellite images is carried out by the GIS spatial analysis. And on the assumption that the water level was 1m at that time when satellite image was taken, the water volume was $225,258m^3$. It is clarified that the effect of water volume improvement was about 10.5% in comparison with water volume that had no consideration on the gradient characteristics of sand-bar.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.264-272
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• 2007

Runoff of non-point pollutants has affected bad influence to water quality of river as reaching within short time. For this reason, reducing them prior to reaching aquatic systems or treating them after collection from discharge process of pollutants are desirable for efficient treatment of pollutants. This study was carried out to develop an ecotechnological method to prevent further aggravation of water quality by non-point source through vegetation filter strips. This study has placed a focus on improving infiltration capacity of soil for the optimum condition of vegetation filter strips. Therefore, we used titled soil filter strips instead of vegetation filter strips in this study. The three types of soil tilter strips were used in a bench scale experiment before applying to the field. The reduction efficiency of pollutants in soil filter strips (SS $84.5{\sim}92.5%$, BOD $67.9{\sim}80.6%$, T-N $43.4{\sim}76.6%$, T-P $40.6{\sim}87.4%$, Cu $28.3{\sim}48.1%$ Fe $92.1{\sim}97.7%$, Pb $81.4{\sim}97.3%$) was much higher than that of the controled group. And non-point pollutants reduction efficiency by soil filter strip's forms was estimated to be distinguishing in order of bio material, mixture of sand and gravel and lastly the whole gravel. In the event, the whole reduction efficiency of pollutants on the soil filter strips disclosed good results.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.1-8
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• 2013

This study was performed for the purpose of analyzing the effect of tide on the stress-strain behavior in the boundary surface of sea dike embankment. Tide is a dynamic condition, but there are not suitable numerical models to solve the dynamic embankment condition caused by tide. So the analysis was simplified to quasi dynamic as follow. First, seepage by tide was analyzed according to elapsed time, and the results of the analysis at every hour during one periodic cycle time of 12 hours were applied to the pore water pressure conditions of stress-strain analysis with hyperbolic model by Duncan and Chang. The place at which maximum shear strain took place in the analysis result moved up and down repeatedly along the boundary of the dredged sand fill section and the crashed stone filter section. The value of maximum shear strain was large at high water level of tide. This result means that contraction and relaxation occur in turn repeatedly at every specific position along the boundary, and the repeated action compact loose position with sand moved down from the upper position by gravity. The experiment with the small sea dike model showed the result consistent with the numerical analysis. The surface of sea side on the dike collapsed at high water level after a couple of repetition of the rising and falling of water.

• Journal of Environmental Science International
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• v.16 no.6
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• pp.671-675
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• 2007

The objective of this study was to clarify the characteristics of the removed micropollutant since the breakthrough of adsorption ability was occurred in biological activated carbon(BAC) process. The removal efficiency of DOC (Dissolved Organic Carbon) was 36 % in the breakthrough of BAC occurred by NOM (Natural Organic Matter). The most of removal DOC was found out the adsorbable and biodegradable DOC (A&BDOC). But it was not clear to remove by any mechanism because A&BDOC have simultaneously the adsorption of activated carbon and biodegradation by microorganism in BAC. The removal of bromophenol was examined with BAC and rapid sand filter, for investigation of DOC removal mechanism in the breakthrough of BAC. In this experiment, BAC filter has been operated for 20 months for the treatment of reservoir water. The BAC filter was already exhausted by NOM. Bromophenol, adsorbable and refractory matter, was completely removed by BAC filter. Therefore, it might be removed by the adsorption in BAC. Adsorption isotherms of bromophenol were compared to two BACs which was preloaded with 500 daltons and 3,000 daltons of NOM. BAC preloaded with 3,000 daltons of NOM was not decreased to the adsorbability of bromophenol but BAC preloaded with 500 daltons of NOM was greatly decreased to it. These result indicated that NOM of low molecular weight can be removed by adsorption after a long period of operation and the breakthrough by NOM in BAC. Therefore, micropollutants might be removed through adsorption by saturated BAC.

• Korean Journal of Environmental Agriculture
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• v.25 no.1
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• pp.14-24
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• 2006

To develop small-scale sewage treatment apparatus for detached house of agricultural village, a small-scale sewage treatment apparatus by natural purification method that consisted of aerobic and anaerobic bed was constructed. To reduce the area of a sewage treatment apparatus, four different fitter media were used and each filter medium was coarse sand, broken stone, steel slag, and mixed fitter media (coarse sand : broken stone : steel slag = 1:1:1). The efficiency of sewage treatment according to the depth of aerobic and anaerobic bed and the volume ratio of aerobic to anaerobic bed were investigated in small-scale sewage treatment apparatus. The removal rate of pollutants according to the depth of aerobic and anaerobic bed in small-scale sewage treatment apparatus was high in the order of 50 cm < 70 cm < 90 cm. The removal rate of pollutants according to the ratio of aerobic to anaerobic bed in small-scale sewage treatment apparatus was high in the order of 1:1 < 1:2 $\fallingdotseq$ 1:3. Under the optimum conditions, removal rate of BOD, COD, SS, T-N and T-P were $98{\sim}99,\;95{\sim}97,\;99,\;65{\sim}66\;and\;96{\sim}99%$ respectively, in small-scale sewage treatment apparatus.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.126-126
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• 2003

Performance of a laboratory scale closed seawater recirculating aquaculture system was evaluated. Twenty-kg Korean rockfish (130 fish) with an average body weight of 153.8 g was stocked. Over 107-day culture period, fish reached final density of 51.7 kg/m$^3$ (initial density, 33.3 kg/m$^3$) on the culture tank volume basis. On a daily basis, water addition was 3.4% of the total water volume in the system. Total ammonia nitrogen (TAN)concentrations were below 1 mg/L and nitrite nitrogen (NO$_2$-N) concentrations were within the range of 1-3 mg/L on most sampling days. TAN was removedin bead and sand filters and it was removed or produced in the sedimentation basin. Basically, NO$_2$-N was removed in the bead and sand filters while it was either removed or produced in the sedimentation basin. Nitrate nitrogen (NO$_3$-N) was produced in the bead filters and removed in the sand filter and sedimentation basin. Foam fractionator performed well in the recirculating system. The maximal daily removal values for total suspended solids (TSS) and protein were 10,9 g and 1.4 g, respectively. Whole water quality parameters were within the levels commonly recommendedfor fish culture on most of the sampling days. However, further studies are needed to evaluate the commercial feasibility of this system because of the small-scale system used in present experiment. At least, present study still provides some basic information for further studies of this kind of system.