• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.1
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• pp.41-47
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• 1981

The characteristics of septic tank sludges were investigated and the kinetic coefficients in the aerobic biodegradation were evaluated from bach treatability tests. Using an unbiased statistical method, the estimated values, k (substrate removal rate coefficient) =0. 0175hr-1 at 17\ulcornerC, K. (Michaelis Menten constant) = 248mg/ e, a (cell yield coefficient)=0.625, and Kd (cell decay coefficient:' =0. 00192hr-1 were obtained based on biodegradable COD(mg/ \ulcorner) and volatile suspended solids(mg/\ulcorner). The relationship between COD and BOD, COD (mg/\ulcorner) =2. 1 BOD(mg/\ulcorner) +250, also was established for the septic tank sludges. Dilution was inevitable for the grit removal because of the high viscosity of the sludges. An aerobic activated sludge process rather than anaerobic processes was recommended for the removal of soluble organics after the removal of grit and suspended solids. A multi-stage activated sludge process was adapted for this highly concentrated and not easily-degradable waste. It was estimated that a four-stage activated sludge process would require 40 hours retention time compared to 92 hours for a single-stage process, 52 hours for a double-stage process, and 46 hours for a three stage process in order to achieve an effluent quality of 84mg/ e COD( 40mg/ e BOD) with about 4, OOOmg/ \ulcorner MLSS from an influent quality of I, 500mg/ t COD(714mg/.e BOD), while multi-stages beyond four stage would not save the required retention time significantly.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.20-26
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• 2008

In this paper, in order to set up the management system of water quality environment in Gwangyang Bay, the cluster analysis of water quality environment, the estimation of inflowing pollutant loads and residence time of pollutants in this bay was carried out. The Gwangyang Bay was divided into eight sea areas by cluster analysis and spatio-temporal change of water quality. The river discharges in the Bay were calculated about $11,681{\times}103m^3/day$ from the numerical simulation by Tank model. In addition, inflowing pollutant loads of COD, SS, TN, TP, DIN and DIP in Gwangyang Bay were estimated at 398 ton-COD/day, 2,846 ton-SS/day, 195 ton-TN/day, 5 ton-TP/day, 126 ton-DIN/day and 3 ton-DIP/day, respectively. Moreover, residence times of COD, TN and TP in the Bay was estimated at 6 days-COD, 20 days-TN and 195 days-TP, respectively in the dry season, and 3 days-COD, 6 days-TN and 21 days- TP, respectively, in the flood season. The central part of Gwangyang Bay (Region IV) has the longest residence time of overall pollutants.

• KSBB Journal
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• v.7 no.3
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• pp.235-245
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• 1992

A number of experiments to treat wastewater of a dye plant were conducted to investigate the basic design parameters and effluent characteristics for aerobic fixed biofilm reactor upon the variation of organic loading rate. The media used for this study were SARAN 4000 D with specific surface area $153m^2/m^3$, and 1000 D with specific surface area $307m^2/m^3$. The influent COD concentration ranged from 1250 to 4080 mg/L. Substrate removal and variation of biomass concentration were observed. At the beginning, the effluent quality was poor but improved as the time passed. However the effluent quality became seriously deteriorated when the media clogged. At influent COD of 1250mg/L, the effluent COD varied little, even if the organic loading rate increased from 0.63 to 2.5kg COD/$m^3$/day. It was also noted that the design parameters for activated sludge process could be applied to an aerobic fixed biofilm process under the experimental conditions.

• Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.182-189
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• 2010

An active stimulating device (ASD) using a rope apparatus may operated by the flow of turbulence inside a cod end, generating variable stimuli in addition to flow-related effects to minimize the by-catch of juvenile fishes. Preliminary testing involved a hydrodynamic effect inside the cod end with a rotating rope kite or conical rope array to generate variable stimuli (visual stimuli, water flow, or physical contact with fish) to change fish position. The experimental rope kite offered more choice in rotating period and range of sweeping action; adjusting the towing line or flow velocity helped to drive fish toward the net panel and encouraged escape. The conical shape of the rope array in the cod end helped to clear a path for fish by disturbing the rigging and providing more contrast between objects, preventing an optomotor response. This enabled more black porgy to be herded toward the net at an early stage of towing. Therefore, either a conical rope array or a rotating rope kite can be used as an effective ASD to prevent juvenile by-catch.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.332-337
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• 2018

The Pacific cod Gadus macrocepahlus, lays demersal eggs and the hatching larvae rise toward the surface layer of the ocean to feed. The change in the specific gravity of eggs and larvae was investigated to examine their vertical distribution and movement in the water column. The specific gravities of fertilized eggs and various size classes of larvae were measured using a density gradient apparatus. In total, the instantaneous specific gravity of 146 eggs and 225 larvae were measured. To prevent any disturbance in the gradient water column due to larval movement, 0.004% MS222 was used for anesthesia. Due to their high specific gravity, eggs spawned were deposited over the sea-bed of the spawning ground. The specific gravity of hatching larvae decreased abruptly. However, Pacific cod larvae still had a comparatively high specific gravity at hatching ($1.03655{\pm}0.00146g/cm3$, n=4, mean SL=3.62 mm) and their specific gravities tended to decrease as they grew. The specific gravity stabilized 6 days after hatching ($1.02590{\pm}0.00212g/cm3$, n=15, mean SL=4.67 mm) and the cod larvae were eventually able to float in the water column.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.355-358
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• 2002

In this study, we have tried to find the maximum microbial efficiency at the various dissolved oxygen (DO) concentration conditions in the treatment of pharmaceutical wastewater. Experiments of activated sludge process were performed to examine the relation between microbial activity and DO concentration in a continuous bioreactor. The reduction rate of COD (chemical oxygen demand) was low at the DO concentration between 0 ppm and 1.0 ppm, but it went higher and showed maximum between 1.5 ppm and 3.0 ppm. Then the COD reduction rate was quickly decreased above the DO concentration of 3.0 ppm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.5
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• pp.493-498
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• 2012

We derived biological reference points for Pacific cod Gadus macrocephalus in southeastern Korean waters by applying a yield-per-recruit analysis based on a daily simulation that adopted size-dependent fecundity, growth, and natural mortality functions. This showed that the yield per recruit of Pacific cod can be maximized at an instantaneous rate of fishing mortality (F)=0.37 $yr^{-1}$ under the current regulations, where the minimum catch size ($L_c$)=30 cm in total length (TL). The maximum economic yield was estimated to be attained at $L_c$=35-45 cm TL, if F>1 $yr^{-1}$ but at $L_c$=35-40 cm TL, if F<1 $yr^{-1}$. Despite great uncertainty in the stock assessment, to develop fisheries management plans for the sustainable exploitation of Pacific cod in southeastern Korean waters, it is necessary to estimate F using capture-recapture or other expedient methods.

• Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.101-108
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• 2013

An active stimulating device (ASD) consisting of a net panel or ropes fluttering in the turbulence inside the cod end was effective in driving fish near the cod end to reduce juvenile by-catch. The fluttering characteristics of the rope and net panel were examined by video observations and analyzed for fluttering amplitude and period in a water channel and in field experiments with a bottom trawl. The amplitude ratio of the fluttering ropes or nets in the tank test increased with the fluttering index as the diameter of the twine, mesh size, flexibility, and flow velocity changed, whereas the period decreased with the above factors. In bottom trawl experiments, the range of mean depth difference in the fluttering net panel was 12-17% of the length of the fluttering net, and the period of depth difference or three-dimensional (3D) tilt was revealed, with shorter ones ranging from 2 to 6 s. The amplitude as depth difference and period from field measurements were similar to those of nets in tank experiments and also to the period of 3D flow velocity inside the cod end. These results could be used to design an ASD that could be used for to the cod end of actual towed fishing gear to reduce juvenile by-catch.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.4
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• pp.66-77
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• 2003

Monitoring data from agricultural reservoirs throughout the country were analyzed to classify agricultural reservoirs according to physical characteristics and COD concentrations, and evaluate the relationships bet-ween water quality items. The physical and chemical data of total 498 reservoirs were analyzed from 1990 to 2001. Average COD, TP, TN, Chl-a, SS concentrations for the reservoirs and pollutant loadings from their watersheds were used for the analysis. It was possible that reservoirs were classified to 4 types using the relationships between the ratios of effective storage per water surface (ST/WS ratio) and COD concentrations. It is recommended that the improvement measures of polluted reservoirs should be performed as following order : integrated consolidation type (complex mechanism type) $\rightarrow$ watershed consolidation type $\rightarrow$ integrated consolidation type (external mechanism type) $\rightarrow$ in-lake consolidation type $\rightarrow$ conservation type and the depth (ST/WS ratio) of reservoir maintained over 5~6 m for water quality improvement. The decision coefficients ($r^2$) between Chl-a and other items (COD, T-P, SS, T-N) were 0.6915, 0.6732, 0.5327, 0.3352, respectively. Therefore, reservoir managers could evaluate the trophic state of reservoirs by COD concentrations.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.2
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• pp.241-249
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• 2013

Ethanolamine (ETA) is widely used for alkalinization of water in steam cycles of nuclear power plants with pressurized water reactor. When ETA contained wastewater was released, it could increase COD and T-N. The treatment of the COD and T-N from ETA wastewater was investigated using the GAC as particle electrodes in three-dimensional electrode reactor (TDE). This study evaluated the effectiveness of GAC as particle electrode using different packing ratio at 300 V. The results showed that GAC-TDE could reduce ETA much more efficiently than ZVI-TDE at the mass ratio of GAC to insulator, 1:2. Additionally, The effect of applied electric potential to COD and T-N reduction was investigated. The results showed the high COD, T-N reduction and current efficiency at the low electric potential. Using the GAC-TDE will provide a better ETA reduction with reducing electrical potential dissipation.