• Proceedings of the Korean Society of Environment and Ecology Conference
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• 2003.10a
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• pp.105-126
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• 2003

In Korea most of annual rainfall is concentrated in several episodic heavy rains during the season of summer monsoon and typhoon. Because of uneven rainfall distribution many dams have been constructed in order to secure water supply in dry seasons. The Han River system has the most dams among Korean rivers, and the river is a series of dams now. Reservoirs need different strategy of water quality control from river water. Autochthonous organic matter and phosphorus should be the major target to be controlled in lakes. In this Paper some problems are discussed that makes efforts of water quality improvement ineffective in lakes of Korea, even after the substantial investment to wastewater treatment facilities.1) Phosphorus is the key factor controlling eutrophication of lakes and the reduction ofphosphors should be the major target of water treatment. However, water quality management strategy in Korea is still stream-oriented, and focused on BOD removal from sewage. Phosphorus removal efficiency remains as low as 10-30%, because biological treatment is adopted for both secondary treatment and advanced treatment. The standard for TP concentration of the sewage treatment plant effluent is 6 mgP/l in most of regions, and 2 mg/l in enforced region near metropolitan water intake point. TP in the effluents of sewage treatment plants are usually 1-2 mg/1, and most of plants meet the effluent regulation without a further phosphorus removal process. The generous TP standard for effluents discourages further efforts to improve phosphorus removal efficiency of sewage treatment. Considering that TP standard for the effluent is below 0.1 mg/l in some countries, it should be amended to below 0.1 mg/l in Korea, especially in the watershed of large lakes.2) Urban runoff and combined sewer overflow are not treated, even though their total loading into lakes can be comparable to municipal sewage discharges on dry days. Chemical coagulation and rapid settling might be the solution to urban runoff in regard of intermittent operation on only rainy days.3) Aggregated precipitation in Korea that is concentrated on several episodic heavyrains per year causes a large amount of nonpoint source pollution loading into lakes. It makes the treatment of nonpoint source discharge by methods of other countries of even rain pattern, such as retention pond or artificial wetland, impractical in Korea.4) The application rate of fertilizers in Korea is ten times as high as the average ofOECD countries. The total manure discharge from animal farming is thought to be over the capacity of soil treatment in Korea. Even though large portion of manure is composted for organic fertilizer, a lot of nutrients and organic matter emanates from organic compost. The reduction of application rate and discharge rate of phosphorus from agricultural fields should be encouraged by incentives and regulations.5) There is a lot of vegetable fields with high slopes in the upstream region of the HanRiver. Soil erosion is severe due to high slopes, and fertilizer is discharged in the form of adsorbed phosphorus on clay surface. The reduction of soil erosion in the upland area should be the major preventive policy for eutrophication. Uplands of high slope must be recovered to forest, and eroded gullies should be reformed into grass-buffered natural streams which are wider and resistant to bank erosion.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.65-66
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• 2005

Anaerobic digestion is one of the well-known methods for biological treatment handling of concentrated organic matter such as swine $wastewater.^{1)} The anaerobic digestion can reduce organic loading but also hydrolyze non-biodegradable organic $matter.^{2)}$ The feces from the scrapper-type barn are usually collected to make compost and the urine is discarded with swine-slurry wastewater by ocean-dumping or treated by biological methods. The lagoon, aerobic digestion, anaerobic digestion, SBR, $A^{2}/O$, and UCT have been applied for treating swine $wastewater.^{3)} In this study, as a result of the analysis of swine wastewater, the total and soluble chemical oxygen demand was 130g/L and 60g/L, respectively. And the volatile fatty acid as chemical oxygen demand equivalent was 45g/L, which was 75% of soluble chemical oxygen demand. Before everything else, ammonia nitrogen concentration was 6.5 g/L. From biochemical acidogenic potential test, it was concluded that the enhanced acidification process to manage swine waste should be operated in the ammonia nitrogen concentration of less than 1.2 g/L. In the result of seeding ratio experiments with artificial $wastewater^{4)}, the lag period of acidogens was taken the long time because of the inhibition by the $ammonia^{5)}$, however no difference of period by the seeding ratio was not shown. The Haldane-based biokinetics were also evaluated using a method of fourth order Runge-Kutta $approximation.^{6,7)}$ The nonlinear least squares (NLLS) method with a 95% confidence interval was also used. The ranges of maximum microbial growth rate, ${/mu_{max}}$, and half saturation coefficient, $K_{s}$, for acidogenesis of various seeding ratio with artificial wastewater were 6.1 ~ 12.6 $d^{-1}$ and 45,000 ~ 53,500 mg glucose/L, respectively. Also, the methanogenic microbial yield coefficient, Y, and microbial decay rate coefficient, $k_{d}$, and inhibition substrate concentration, $K_{si}$, for the reactors were determined to be 0.32 ~ 0.465 ${/mu}g$/mg glucose; 0.42 ~ 1.01 $d^{-1}$ and 51,500 ~ 55,600 mg glucose/L, respectively.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.191-203
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• 2024

One of the issues with clayey soils, particularly those with significant quantities of organic matter, is the creep settling problem. Clay soils can be strengthened using a variety of techniques, one of which is the use of stone columns. Prior research involved foundation loading when the soil beds were ready and confined in one-dimensional consolidation chambers. In this study, a particular methodology is used to get around the model's frictional resistance issue. Initially, specimens were prepared via static compaction, and they were then re-consolidated inside a sizable triaxial cell while under isotropic pressure. With this configuration, the confining pressure can be adjusted, the pore water pressure beneath the foundation can be measured, and the spacemen's lateral border may be freely moved. This paper's important conclusions include the observation that secondary settlement declines with area replacement ratio. Because of the composite ground's increasing stiffness, the length to diameter ratio (l/d) and the stone column to sample height ratio (Hc/Hs) both increase. The degree of improvement varies from 12.4 to 55% according to area replacement ratio and (l/d) ratio.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.315-322
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• 2007

The purpose of this study was to investigate the biodegradability and performance of organic removal and methane production rate when treating piggery wastewater using a granule of two-phase anaerobic process applied UASB. BMP test was conducted as simple means to monitor relative biodegradability of substrate and to determine methane production of an organic material. The two-phase anaerobic process is consisted of a continuous flow stirred-tank reactor (CFSTR) for the acidification phase and an Upflow Anaerobic Sludge Blanket reactor (UASB) for the methanogenesis. The acidogenic reactor played key roles in reducing the periodically applied shock-loading and in the acidification of the influent organics. A stable maximum biogas production rate was 400mL. The methane contents ranged from 73 to 80% during the experimental period. It is known that most of the removed organic matter was converted to methane gas, and the produced biogas might be high quality for its subsequent use.

• Membrane Journal
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• v.14 no.4
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• pp.289-297
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• 2004

In this study, membranes were coupled to a sequencing batch reactor for simultaneous removal of organic matter and nitrogen, and the influences of MLSS (mixed liquor suspended solid) concentration and the sludge loading rate on membrane fouling and bioactivity were investigated. The amount of membrane fouling slightly increased with MLSS concentration at both non-aeration and aeration conditions, but effect of MLSS concentration was more significant at aeration condition. Although the effect of MLSS concentration on membrane fouling was found to be insignificant at low concentration level, extremely low sludge loading, which were generated by the maintenance of large amount of biomass in the reactor, caused severe membrane fouling, and air scouring effect decreased significantly in this condition. Specific bioactivity was constantly reduced as sludge loading rate decreased. In spite of high MLSS concentration over 17,000 mg/L, the activity of the reactor decreased at extremely low sludge loading rate presumably due to the lower oxygen transfer and the competition of biomass to deficient substrate.

• Journal of environmental and Sanitary engineering
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• v.15 no.3
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• pp.15-23
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• 2000

This study's purpose is the investigating the created liquid post-acid fermentation of usability of denitrification as exterior carbon sources by loading capacity of Organic matters. The time of acid fermentation of food waste, the slower loading capacity of organic matter, the faster decomposition fate, but the density of generation $VFA_S$ was weak and, $SBOD_5$ : ST-N rate and $SBOD_5/SCOD_{Cr}$ rate was low. Between TS and VS, VS was decreased to 6th day rast, and then was decreased slowly. Two days after stating the experiments, $SCOD_{Cr}$, $SBOD_5$, STOC and $VFA_S$ was decreased or increased slowly, and then increased fast. And after showing the highest density, it was tended to decreased fast. About 5 days after, because about 5 days later $CH_4$ bacteria activity due to the accumulation of $VFA_S$ was limited, $CH_4$ density was weak. When highest density in the acquisition of VFA, $R_1$ was $10,120mg/{\ell}$, $R_2$ was $11,380mg/{\ell}$, $R_3$was $13,720mg/{\ell}$. So $R_3$ only cut was highest generation. At the time of $SBOD_5$ with the highest density, at $SBOD_5$ : ST-N ratio, $R_1$ was 243:1, $R_2$ was 278:1, $R_3$ was 293:1. All of these were high $SBOD_5$ : ST-N ratios. And $R_3$ was the highest. After studying $SBOD_5$ : ST-N ratio and $SBCD_5/SCOD_{Cr}$ ratio, as a carbon source of biological denitrification it was profitable composition ratio.

• Journal of Environmental Health Sciences
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• v.24 no.1
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• pp.38-46
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• 1998

This study was to investigate the effects of carbon loadings, temperature and expansion ratio on the waterborne organic removal by the biologically active GAC fluidized bed on a laboratory scale. The raw water to be treated comes from midstream of Han river. BACFB(Biological Activated Carbon Fluidized Bed) process was very effective to remove the biodegradable fraction of dissolved organic matter. The more carbon weighed, the more DOC removed in a range from 16.7 to 133.3 g/l. DOC and UV$_{254}$ were removed more than 40% and 20% above 20$\circ$C respectively. Between 5$\circ$C and 10$\circ$C, DOC and UV$_{254}$ were eliminated about 30% and 15% respectively. In general, even if the temperature was higher, DOC removal was a little sensitive, probably influenced by GAC's residual adsorption capacity. UV$_{254}$ reduction was little fluctuated in accordance with water temperature. The gradual increase in expansion ratio from 10% to 75% didn't greatly affect on the removal of DOC and UV$_{254}$. The expansion ratio, therefore, is not a key factor over the critical expansion ratio.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.603-609
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• 2004

The objective of this study was to determine the optimal operation conditions in an anoxic oxic process to eliminate both organic and nitrogen matters in swine wastewater. For the purpose of this, the removal efficiency was evaluated with various HRTs and internal recycling ratio. During the whole 580 days of experiment, HRTs had been gradually decreased in an order of 20, 14, 12 and l0days, and the internal recycle ratio was kept at 20Q. So as to determine the effect of the internal recycle ratio on the nitrogen removal, the internal recycle ratio had been gradually increased from 20Q to 50Q while HRT was maintained at 12days. As a result, it was shown that the removal efficiency of organic matter was above 95% regardless of changing of HRTs. The average influent concentration of TCODcr and SCODcr were 24,854 mg/L and 18,920 mg/L, respectively. Average removal efficiency of TKN was shown to be nearly 98% when HRT was kept at 12days; however, the $NH_4{^+}-N$ concentration of effluent was shown to be increased when the loading rate of $NH_4{^+}-N$ was increased to $0.602 kgNH_4{^+}-N/m^3$-day by means of decreasing HRT to 10days. It was concluded that nitrogen loading rates should be more considered rather than organic loading rates in case of determining an optimal HRT. When gradually increasing the internal recycle ratio from 20Q to 50Q, the removal efficiency of organic matters and TKN were 96% and 98%, respectively so that no significant changes in removal efficiency was detected. However, when the internal recycle ratio was kept at 50Q, it was revealed that the $NO_3-N$ concentration of effluent seemed to drop and the average $NO_3-N$ concentration of effluent was around 52 mg/L.

• 한국해양학회지
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• v.29 no.2
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• pp.107-118
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• 1994

An investigation of the annual change and C:N:P ratio in particulate organic matter (POM) in Chinhae Bay, a semi-enclosed bay of the southern coast of Korean Peninsula, was carried out for a period of 12 months between January and December, 1993. The concentrations of POM have a broad range: 198∼4,416 ugC/l, 24∼792 ugN/l and 4.5∼69.0 ugP/l, Marked seasonal changes of POM, particularly particulate organic carbon (POC) and nitrogen (PON), were observed in the surface water. Generally, the concentration of POM peaks in summer. The C:N:P composition ratio of particulate organic matter, which is high in summer, also shows a seasonal change. The C:N assimilation ratio is constant at 6.53, which is consistent with the Redfield ratio. The significant linear relationship between POM and chlorophyll-a in the surface water during the survey period (except for January and February) and the C:N ratio suggest that the concentration of POM is controlled by phytoplankton biomass. POM peaks in summer, a period characterized by high freshwater input and the strong stratification, as a result of the intense proliferation of phytoplankton by a large amount of nutrient loading from the tributaries. On the other hand, the high C:P and N:P ratios in summer indicate that P is limited for phytoplankton growth owing to N-enrichment from a high input of freshwater with a high dissolved inorganic N:P ratio.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.2
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• pp.28-35
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• 2015

In this study, the experiment was carried out to produce methane by applying Semi-Continuous Leachate Recirculation Anaerobic Digestion System fed with source separated food waste from school cafeteria. There were two systems and each system consisted of a bioreactor and a liquid tank. Each bioreactor had a screen near the bottom of the reactor. 2.5L of separated liquid was transferred to the liquid tank for 30min each day by using a tubing pump and the liquid from the liquid tank was pumped to the bioreactor at the upper of the bioreactor as soon as the transfer was ended. Through this circulation, the liquid having high concentration of VFAs was supplied to the top of bioreactor. At the beginning of the experiment, food waste/inoculum anaerobic sludge volume ratio was 2:8 that is 9g VS/L of OLR(Organic Loading Rate). Feeding was conducted every two weeks. Experimental results showed that the contents of moisture, combustible matter, ash were 65.91%, 32.73%, and 1.36%, respectively. Two different food waste loading were studied. The average organic loading rates were 3.51g VS/d for System A and 3.86g VS/d for System B, respectively. The average produced methane based on food waste fed to bioreactor were observed as $6.30m^3CH_4/kgVS{\cdot}d$ for system A and $4.94m^3CH_4/kgVS{\cdot}d$ for System B, respectively.