• Economic and Environmental Geology
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• v.32 no.2
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• pp.177-187
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• 1999

Gravity, magnetic and VLF surveys were conducted to investigat the structural stability and hazards associated with the Ubong landfill in Pohang City, which has been built to dump industrial wastes. In 1994, the collapse of a bank happened in the 6th landfill site due to sudden heavy rain, and a large quantity of waste materials flowed out to the nearby landfill sites, factories and roads. We used $10{\times}10m$ resolution DEM data for gravity reductions. The maximum variation of the terrain effect in the survey area is about 0.5 mgal and the terrain effect is large in the vicinity of bank boundary. The Bouguer gravity anomaly map shows the effect due to the variatino of thickness and type of waste materials. The small negative gravity anomaly increases from the 9th site to the 6th site. The small negative gravity anomaly of the 9th site reflects the relatively shallow dumping depth of average 14.5 m in this site and increased density of waste materials by the repeated stabilization process of soil overlaying. The 6th site is located at the center of the former valley and rainfall and groundwater are expected to flow from south-east to north-west. Therefore, considering the previous accident of mixing waste and bank materials at the north-west boundary of the landfill, there may be some environmental problems of leakage of contaminated water and bank stability. The complex inversion technique using Simulated annealing and Marquardt-Levenberg methods was applied to calculate three-dimensional density distribution from gravity data. In the case of 6th site, it is apparent that the landfill had been dumped in four sectors. However, most part of the 9th site and showed that high magnetic industrial wastes were concentrated in the 6th site. The result of magnetic survey showing low magnetic anomalies along the boundaries of two sites is similar to that of gravity data. The VLF data also reveals four divided sectors in the 6th site, and overall anomaly trend indicates the directio of former valley.

• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.15-23
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• 2009

The aim of this study was an evaluation of closed non-sanitary landfill's stabilization degree and a determination of its an optimal reclamation method. In order to evaluate the stabilization degree, physical compositions of landfill wastes in 21 closed non-sanitary landfills were analyzed. There were 4 major items such as cover soils, organics, combustibles and incombustibles. With respect to the results of physical compositions, it was determined that the waste in 9 sampling sites of closed non-sanitary landfills after 10years of the relief time was not fully stabilized. The closed non-sanitary landfills must be reclaimed as soon as possible. The main material in closed non-sanitary landfills was cover soils and the highest content was 89.96%. Otherwise, the contents in sanitary landfills was small and 9.89~11.12%. Therefore, it was evaluated that the recovered soil by sorting transfer treatment could be reused as on-site cover soils of the reclamating non-sanitary landfills and/or constructing materials.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.1
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• pp.139-150
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• 2006

Landfilling is one of the most widely used methods for the final disposal of solid wastes. Landfilled wastes are degraded by residing microorganisms and the microbial degradation is affected by many factors such as moisture, oxygen, pH, alkalinity, sulphate, nutrient, temperature, and so on. Especially among these factor, oxygen and moisture within aerobic landfill play a major role in microbial degradation. In this study, 1) the effects of oxygen on the velocity of waste degradation and 2) the effect of moisture on the degradation of municipal solids waste (MSW) in aerobic condition were investigated. It was found that the BOD and CODcr concentration from the leachate of aerobic lysimeters dropped faster by 80 days after the start of the test compared to those from the anaerobic lysimeters. To see the effect of moisture, four aerobic lysimeters filled with MSW and four different levels of moisture (20, 30, 40, and 50%) were installed. From this test, higher moisture in MSW produced higher $CO_2$ concentration, meaning moisture was effective for the microbial degradation. thus, we concluded that higher moisture level in the aerobic landfill might help early-stabilization microbial degradation.

• Journal of environmental and Sanitary engineering
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• v.19 no.3 s.53
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• pp.13-21
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• 2004

This study was focused on the evaluation of Nanjido landfill site by leachate analysis. Several parameters, for example pH, BOD, $COD_{Mn},\;COD_{Cr}$, SS, TP, $NH_3-N$, Color, were selected as major leachate quality parameters. $BOD/COD_{Cr}$. was used to estimate the biodegradable portion in organic matter. Samples were collected at the leachate storage wells and leachate treatment facility inflow in each quarter of 2003. The results were as follows : 1. Inflow quality of treatment plant in 2003 was analysed as $pH\;7.3\~8.0,\;BOD\;12.4\~30.0mg/L,\;COD_{Mn}\;101.2\~130.3mg/L,\;COD_{Cr}\;122.5\~238.0mg/L,\;SS\;16.1\~115.3mg/L$, $T-P\;0.27\~0.80mg/L,\;NH_3-N\;208.0\~~354.0mg/L$, Color $110.3\~129.0$ unit. 2. $BOD/COD_{Cr}$ of inflow ranged between $0.07\~0.16$ indicating that the landfill had the properties of old-fill and organic portion in leachate was mostly persistent organic matter. 3. Though concentrations of BOD, COD, $NH_3-N$, Color in leachate storage wells were mostly higher in first landfill than in second landfill, $BOD/COD_{Cr}$ ranging from 0.03 to 0.20, showed reversely. 4. Correlation coefficient$(R^2)$ between color and other parameters related to organic matter showed mostly above 0.7 and especially highest value with $COD_{Mn}$ of 0.7985.

• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.5-13
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• 2005

The conventional settlement prediction method is not appropriate to model landfill settlement because it is very complex phenomenon. Biodegradation needs to be considered for long-term settlement since landfills are comprised of various organic materials and soils. As organic materials are decomposed, they directly influences on settlement producing LFG(Landfill Gas). Therefore, mathematical settlement prediction model is proposed based on the generated gas volume. As one of stabilization methods, leachate recycling system is adopted to model tests. Two model tests; one is leachate recycled, the other is non-recycled, are componented with proposed model and analysed regarding gas generation and settlement. The proposed mathematical model requires correction coefficients of 1.4 and 1.7 for non-recycled model and recycled, respectively. The recycled model showed 22% increase of long-term settlement more than the non-recycled model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.221-232
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• 1993

In this study, the period for stabilization in the case of recycling leachate was compared and analyzed with the case of non-cycle type, using lysimeters filled with municipal organic refuse. The lysimeters were operated with various detention time. In addition, the degree of stabilization was estimated by the way of measuring the quantity of gas from landfills. As the results, the recycle of leachate, which was modified as the neutral level of pH, accelerated the biological decomposition of organics with the raped growth of anaerobic bacteria in the system, and reduced the period for the stabilization. In the case of BOD and COD in leachate, COD. which had been originality similar to BOD, had increased more rapidly than BOD as time lapsed. Moreover, the quantity of gas from the recycle reactor was larger than from the non-cycle reactor. The shorter the detention time of leachate gas, the larger the quantity of gas produced in the lysimeters.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.679-684
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• 2014

Many burial sites were constructed to suppress the spread of foot and mouth disease during outbreak. Defected burial sites were removed when leachate leak is presumed and carcasses were moved to the circular storage tanks. However, carcasses were not decomposed possibly due to low water content, low microbial activities, and poor mixing. In this research, storage tank containing carcasses in it was modified to bioreactor to accelerate stabilization. Liquids with nutrients were added and circulated to maintain the optimum water content while extraneous microorganisms were augmented. Settlement was used as the primary index for assessing stabilization rate, and the consolidation theory was utilized to estimate the expected final settlement. 30% of carcasses is expected to be decomposed and removed from the storage tank for five years of bioreactor operation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.328-335
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• 2002

In this study, experiments were performed to investigate the characteristics of flame stabilization of the LFG mixing gas. LFG has merely half heating value compared with liquified natural gas but can be greatly utilized as a commercial fuel. In order to use LFG in practical combustors, Webbe Index and heating value of LFG mixing gas were adjusted by mixing LPG with LFG. The comparisons were conducted between CH$_4$and LFG mixing gas for searching the region of flame stabilization based upon the flame blowout at maximum fuel stream velocity. As a result, the flame stability of LFG mixing gas was not improved with that of CH$_4$in non-swirl and weak swirl diffusion flame. However, LFG mixing gas had wide flame stabilization region rather than CH$_4$with increasing ambient flow rate in strong swirl. It was also found that flame stability was affected by included quantity of inert gas such as CO$_2$in the weak swirl but by heating value of fuel in strong swirl.

• Journal of Environmental Impact Assessment
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• v.14 no.2
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• pp.47-53
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• 2005

노은 매립지는 사용종료된지 5년이 경과된 비위생매립지로 최종복토는 되어 있으나 침출수 차집시설 및 매립가스 포집설비가 제대로 갖추어지지 않은 상태이다. 환경부의 사용종료 매립 지 정비지침에 의하면 침출수의 BOD/CODcr 비율이 1/10 수준임으로 침출수의 안정화 과정이 거의 완결상태로 진행되고 있는 것으로 판단된다. 매립지 가스의 안정화 측면에서는 CH4의 비 율이 5%정도이기 때문에 안정화가 거의 이루어진 것으로 볼 수 있다. 매립된 쓰레기 중에서 플 라스틱을 제외한 가연물 함량이 3.97 - 9.34%이기 때문에 매립폐기물은 안정화 기준에 미흡한 상태이다. 그리고 지하수는 대장균 항목이 지하수 수질기준 생활용수 기준에 미흡하여 안정화 기준을 충족시키지 못하고 있다. 노은매립지는 매립지 안정화의 속도가 평가 대상별로 상이하 게 진행되는 것으로 평가된다.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.3
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• pp.76-85
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• 2004

Anaerobic decomposition of municipal solid waste (MSW) had potential adverse impacts such as the production of methane and long-term post closure on human health and the environment. It was demonstrated that aerobic degradation of MSW resulted in the reduction of a methane yield and the enhancement of stabilization of MSW. Excavated solid wastes were both aerobically and anaerobically treated in order to evaluate the effects of air injection on the stabilization of landfill site. The municipal solid waste (MSW) samples were excavated from a 10-year old landfill (operation period: 1991. 11~1994. 11), Jeonju, Korea. Excavated municipal solid wastes are primarily composed of soils and vinyl/plastics. For the two aerobic simulated lysimeters, the levels of $O_2$ ranged 1.6~23.1% and the levels of $CO_2$ ranged 1.5~15.1%, which confirmed the aerobic decomposition. Aeration did prevent methane formation. For the anaerobic simulated lysimeter, the $CO_2$ rose as $O_2$ was consumed and low levels of CH4 were produced. The pH levels ranged from 7.7 to 8.9 for anaerobic lysimeter and from 7.3 to 8.5 for aerobic lysimeters. As expected, aerobic treatment proved to enhance the removal of biodegradable materials in the excavated solid wastes when monitoring the concentration of BOD, COD, $NH_4-N$, and $NO_3-N$ in the leachate.