이혜성 Hye-sung Lee , 한용원 Yong-won Han , 김용진 Yong-jin Kim

DOI:10.9786/kswm.2018.35.5.385

Abstract

Plastics, such as fiber-reinforced plastics (FRP), from vessels, nets, ropes and buoys that are found in marine materials are refined by various factors in the ocean. These microplastics are present in the surface, middle, deep and sedimentary layers of the ocean depending on their physical and chemical properties. In this study, the distribution characteristics of microplastics in mud flats are investigated and their sources are estimated. The highest percentage of microplastics consisted of blue paint fragments, which seemed to be paint from a ship. In addition, many fibrous microplastics were found in the surface layer of the mud flats. These results suggest that low-density fibers are partially retained on the surface of mud flats during high and low tide. The differences in the amount and types of microplastics at the survey sites are considered to be influenced by the surrounding environment, such as fishing vessels and farms.

Key Words

Microplastics, Mud flat, Octopus fishery, Laver farm

오정근 Jung-keun Oh , 조윤아 Yoon-a Cho , 엄남일 Nam-il Um , 신선경 Sun-kyoung Shin , 이영기 Young-kee Lee , 김기헌 Ki-heon Kim

DOI:10.9786/kswm.2018.35.5.391

Abstract

Inappropriate recycling/disposal processes that are caused by the illegal transboundary movement of electronic wastes (e-wastes) can have harmful effects on the environment and public health because of these wastes’ harmful components. Therefore, we must understand the current situation regarding the domestic management of exported/imported e-wastes and examine the international requirements according to the Basel Convention. In this study, the current management situation of e-wastes in domestic and foreign countries and the present recycling processes of companies in Korea are investigated to draw improvements when e-wastes are exported or imported. Most imported e-waste involves waste printed circuit boards (WPCB) and their scraps (more than 95.7 % of the total e-waste volume in 2015) to recover precious metals such as copper, silver, gold, etc. To distinguish between waste and non-waste under the Basel Convention, six items (① market for used electronic and electrical equipment (UEEE), ② residual life and appearance, ③ functional tests, ④ evidence of UEEE deals, ⑤ evidence of contracts to a trade partner, and ⑥ packaging and loading conditions) and a decision flowchart are considered to classify whether the end-of-life equipment is waste.

Key Words

Basel Convention, E-waste, WPCB, UEEE

김민정 Min-jung Kim , 황동건 Dong-gun Hwang , 강영렬 Young-yeul Kang , 전태완 Tae-wan Jeon , 유혜영 Hye-young Yoo

DOI:10.9786/kswm.2018.35.5.404

Abstract

According to the revised version of Waste Control Act to enter into force in 2017, Wastes could only be recycled assuming that the use of recycled wastes is safe for the environment and human health by environmental safety assessment. Even before this revision of the law, inorganic sludges could have been recycled as alternative materials for filler and cover materials by mixing with soil. However, in case of inorganic sludge from car-washing facilities, the revised law provides that the waste has to be landfilled. To assess the possibility of recycling this waste, we investigate the characteristics of the generation and concentration level of hazardous substances and evaluate the safety of recycling this material to assess whether this process meets the environmental standards. We obtained a total of eight sludge samples from car-wash shops, such as those in gas stations, car-repair shops and car-wash facilities. According to the results of leaching tests, most of the samples(8) fell under the detection limit and thus could be legally treated as general waste. However, in the results of contents some heavy metals, such as hexavalent chromium, lead, copper and zinc, exceeded the standards for soil contamination. We can conclude that the recycling of inorganic sludge from car-wash facilities could cause pollution in soil media when recycled and should not be recycled for filler and cover materials.

Key Words

Recycling of Inorganic sludge, Car wash facility, The environmental safety assessment

이명호 Myungho Lee

DOI:10.9786/kswm.2018.35.5.411

Abstract

More than 50 million tons of dredged soils are produced every year in Korea. Approximately 10% of these dredged soils are dumped into the ocean because of contamination, while 80% are reclaimed to create artificial wetlands, artificial beaches, and ecological parks. The interpretation of sedimentation and self-weight consolidation behavior is very important because this behavior is closely related to the stabilization of dredged soils and the landfilling period. The analytical solution for the calculation of excess pore-water pressure is obtained by determining the initial and boundary conditions. Then, the surface settlement and density profiles are predicted by using this analytical solution. The analytical solution from Terzaghi’s one-dimensional consolidation theory and this study’s numerical simulation with mass conservation more easily predicted the self-weight consolidation behavior of dredged soft soils than the non-linear finite strain consolidation theory.

Key Words

Dredged soil, Landfilling, Self-weight, Consolidation, Analytical method

이명호 Myungho Lee

DOI:10.9786/kswm.2018.35.5.421

Abstract

More than 45 million tons of marine clay is dredged in the western and southern sea every year in Korea. Dredged soils, which are relatively easily supplied, have been known as an economical fill material for the construction of airports, ports, and industrial land. However, dredged soils can no longer be used as a construction material because they contain various types of heavy metals and organic pollutants. If an electric field is applied to dredged sediments, various phenomena such as electrophoresis, electro-osmosis, electro-migration, electrolysis occur because the surface of marine clay is negatively charged. The interpretation of sedimentation and self-weight consolidation is very important because this behavior is closely related to the stabilization of dredged sediments and the landfilling period. The analytical solution for the calculation of excess pore-water pressure is obtained by determining the initial and boundary conditions. Then, the surface settlement and density profiles are predicted by using this analytical solution. The analytical solution from Esrig’s one-dimensional electrokinetic consolidation theory and this study’s numerical simulation with mass conservation more easily predicted the electrically induced consolidation behavior of dredged sediments than the non-linear finite strain consolidation theory.

Key Words

Dredged soil, Landfilling, Electrokinetics, Consolidation, Analytical method

이재희 Jaehee Lee , 최장욱 Jangwook Choi , 최신묵 Shinmook Choi

DOI:10.9786/kswm.2018.35.5.432

Abstract

Renewable energy resources from foodwaste have attracted significant interest and, consequently, many alternatives are considered for large-scale biogas treatment processes and small-scale onsite drying processes (heat source: electricity, gas, and dried foodwaste by-product). The pre-treatment process for foodwaste consists of the following sequential steps: collection, transportation, shredding, segregation, and dehydration. After this pre-treatment, the dried foodwaste by-product is recycled into (among others) animal feed, fertilizer/compost or biomass solid fuel. In addition, the leachate?liquid generated by squeezing the foodwaste is used for bio-gasification, achieved through an Anaerobic Digestion (AD) process associated with a sewage co-digestion treatment. In this study, the operation cost and greenhouse gas (GHG) emissions of an improved and simplified small-scale onsite drying treatment are compared with those of a large-scale biogas treatment. The pre-treatment can be improved and simplified via this drying treatment. Through this treatment, operationcost reductions of 45.4%, 50.5%, and 89.6% are achieved when electricity, liquified natural gas (LNG), and biomass solid fuel (dried foodwaste by-product), respectively, are employed as drying heat sources. Furthermore, if the annual amount of foodwaste (5 million ton) is recycled into biomass solid fuel, then significant reductions (7.5 million tCO₂-e per annum) in GHG emissions can be realized. Therefore, this study demonstrates that improvement and simplification of the smallscale drying process (i) reduces the operation cost as well as GHG emission levels (to levels lower than those achieved via the large-scale biogas treatment process) and (ii) offers a practical solution for foodwaste treatment and a renewable energy resource.

Key Words

Drying, Foodwaste, Heat source, Greenhouse gas, Operation cost

김봉주 Bong-joo Kim , 정의인 Ui-in Jung , 곽은구 Eun-gu Kwak

DOI:10.9786/kswm.2018.35.5.444

Abstract

Waste concrete powder generated during the process of recycling waste concrete into aggregate has a low recycling rate. This is because fine particles of waste concrete powder and cement components are present. Therefore, in this study, waste concrete powder is used as a raw material for centrifugal concrete. Experimental results show that waste concrete powder has cement and aggregate composition, SEM image has irregular shape, C-S-H and Ettringite exist inside. Waste concrete powder showed the same strength, up to 5% in terms of strength by age according to the substitution rate. Also, as the strength characteristics varied according to the centrifugal forming force, the substitution rate of siliceous matter increased by 5% and the strength decreased by substitution rate of 5%. Because of this study, it is considered difficult to use waste concrete powder as a substitute for silica sand because of the resulting characteristics of centrifugal concrete. It is recommended that economic and environmental concerns be considered when some substitution is made for silica sand.

Key Words

Waste concrete powder, Replacement ratio, Centrifugal, Strength, Microstructure

박지형 Ji-hyoung Park , 황용우 Yong-woo Hwang , 민달기 Dal-ki Min

DOI:10.9786/kswm.2018.35.5.451

Abstract

Local government should have waste treatment facilities to provide good service to local residents, even though private recycling is working. There was a problem with plastic waste management in Korea in 2018. Therefore, study was conducted on whether local government has the capacity to handle additional waste streams. The study was conducted, solely using government statistics, on domestic mixed solid waste. The amount of additional plastic waste to be disposed was 2,418 ton/day (incinerate 713 ton/day + landfill 1,705 ton/day), and paper waste was 4,469 ton/day (incinerate 1,104 ton/day + landfill 3,365 ton/day). Current incinerator capacity is sufficient, and if paper waste is added, the incinerator capacity is found to be under1,544 ton/day. Landfill capacity is sufficient even if plastic and paper waste is added, but the residual life of the landfill was reduced from 31.4 years to 25.4 years. Regionally, Gyeongbuk, Daejeon, Jeju, and Sejong should develop new plans for waste management.

Key Words

Domestic waste, Treatment facility & capacity, Plastic & paper waste, Low recycling

임승환 Seung-hwan Lim , 정진도 Jin-do Chung

DOI:10.9786/kswm.2018.35.5.459

Abstract

Recently, the Ministry of Industry has made efforts to expand renewable energy by 2030, and the Ministry of Environment has sought to revitalize solid fuels from livestock manure, which is a type of bio-energy source, such as reviving laws to activate solid livestock fuels. However, the operating costs of fuel-manufacturing facilities must be reduced to activate solid livestock fuels. The proper dryer must be selected to reduce the drying cost, which comprises the majority of the operating expenses. Laboratory-scale experiments were conducted to confirm the possibility of drying cow manure, the feasibility of utilizing waste heat and the existence of an adhesion solution. Some adhesion phenomena were detected from the disk-dryer results. However, this phenomenon disappeared when the water content of the cow manure was below 50%. A water content of 41% was used to confirm this adhesion phenomenon in the cow manure. Because of the high viscosity of cow manure, a recycling method had to be applied through the disk to match the water content in the dryer. A drying test with a duct rotary dryer confirmed that waste heat that is generated from power plants can be utilized to lower the moisture content of solid fuels in livestock waste to 20%.

Key Words

Livestock, Cow manure, Moisture content, Disk dryer, Duct rotary dryer

이소라 Sora Yi , 최창식 Changsik Choi , 조성수 Sung-su Cho , 서민혜 Min-hye Seo , 지규철 Gyu-cheol Ji , 김인배 In-bae Kim , 최성만 Seong-man Choi , 장원석 Won Seok Chang , 임성묵 Seong-mook Lim

DOI:10.9786/kswm.2018.35.5.464

Abstract

This study assesses greenhouse gas evolution from construction-material manufacturing facilities and estimates the potential reduction of these gases via the future massive sequestration of carbon dioxide. The scope of the evaluation specifically targets the global-warming potential in terms of kg-CO₂ equivalent/tonnage industrial waste. Life cycle assessment (LCA) is a method to quantitatively analyze the input and output of a specific material resource during its life cycle from raw-material acquisition to final disposal as well as its environmental effect(s). LCA comprises four steps: its objective and definition of the scope, the entire life-cycle analysis list, an evaluation of its effects, and life-cycle analysis. The annual inflow of petro-ash reaches 300,000 tons, and this material is transported via screw-driving systems. The composition of the petro-ash is 1.2% volatile compounds, 6.8% fixed carbon and 92% ash contents. A total of 38,181,891 Nm³/yr of carbon dioxide is sequestrated, which is equivalent to 75,000 tons per annum and 304.5 kg/ton of petro-ash waste, with 250 kg/ton of the latter sequestrated as calcium carbonate. The final analysis on the effect of one ton of petro ash in construction materials showed 27.6 kg-CO₂ eq emission. According to the final LCA analysis, only 27.6 kg-CO₂ eq/ton was emitted by the petro-ash that was used in construction materials if CO₂ fixation during carbonate mineralization was considered, where -250 kg-CO₂ eq/ton positively contributed to the LCA. In the future, commercial-scale process modification via the realization of continuous processes and the more efficient reduction of carbon dioxide is anticipated.

Key Words

Carbon dioxide, Life cycle assessment, Greenhouse gas, Petro-ash, Mineral carbonation