김용진 Yong-jin Kim , 정승미 Seung-mi Jeong , 이혜성 Hye-sung Lee

DOI:10.9786/kswm.2020.37.4.219

Abstract

In this review, data on the ingestion, translocation and egestion of microplastics by different organisms are analysed and summarized to predict the behaviour of microplastics in human body. Microplastics translocation from the gastrointestinal tract to the circulatory system or tissue are associated with the species and groups of organisms and the size of microplastics. Ingested microplastics are translocated to thoracic lymph nodes via macrophages and to the liver, kidney, spleen, heart, brain and secondary target organs via systemic circulation. In the ingestion, translocation, and egestion of microplastics by mammals, particles of >150 μm are rarely translocated or absorbed by organs (except the gut), characterized by a localization effect on the immune system or gut infection. Although microplastics <150 μm are linked to systemic exposure, their absorption remains limited with intense absorption restricted to particles <1.5μ m. Existing studies have focused on laboratory experiments to investigate microplastic concentrations in food, the type of plastics, and morphology (e.g., free or aggregate state, particle size, and shape). To further understand the behaviours of microplastics, systematic and comprehensive studies should be continued.

Key Words

Microplastic, Bio-organism, Ingestion, Translocation, Egestion

박동규 Dong Kyoo Park , 김동주 Dongju Kim , 구재회 Jae-hoi Gu , 김동철 Dong-cheol Kim

DOI:10.9786/kswm.2020.37.4.235

Abstract

The worldwide increase in energy consumption and global climate change leads to a growing interest in the utilization of unused waste heat generated by power plants and industries. In terms of recovery, storage, and reuse of the waste heat, thermal energy storage (TES) technology is considered one of the key technologies. In addition, a heat delivery system using a mobile-TES has been proposed and commercialized in several countries. In this study, heat charging and discharging processes were carried out in a 10 MJ-scale TES unit based on the latent heat of phase change material (PCM). The unit, designed to develop the TES　module, has a tube that is finned inside and outside to enhance the heat transfer surface. Docosanol was chosen as a heat storage material, and three types of heat transfer fluids were used: water, steam, and air. The results show that total heat storage using hot water and steam was 49 MJ and 17 MJ at rates of 9 kW and 18 kW, respectively. Most of the heat stored in the TES unit can be discharged at a thermal efficiency of 87 ~ 88%, and hot air can be produced indirectly and directly with efficiencies of 78% and 86%, respectively.

Key Words

Waste heat, Thermal energy storage, Phase change material, Module, Heat transfer

노형진 Hyeong-jin Noh , 유인근 In-geun Yu , 김승민 Seung-min Kim , 백승민 Seung-min Beak , 김우석 Woo-suk Kim , 곽윤근 Yoon-keun Kwak

DOI:10.9786/kswm.2020.37.4.245

Abstract

This study investigated the optimum binder content by analyzing its mechanical properties according to the replacement ratio and amount of calcium carbonate binder, used as a filler for polymer concrete, that was replaced with finely powdered waste glass. To investigate the replacement of polymer concrete fillers with fine waste glass powder instead of the previously used calcium carbonate, experiments were conducted with the binder amount used (11%, 13%, and 15%) and the replacement ratio of calcium carbonate and waste glass (10 : 0, 5 : 5, and 0 : 10). It was found that the replacement ratio of the finely powdered waste glass was suitable up to 50%, and the optimum mixing ratio of binder was 13% for concrete compressive strength and 15% for concrete tensile strength.

Key Words

Waste glass, Calcium carbonate, Filling material filler, Polymer concrete, Environmental friendliness

이영진 Young-jin Lee , 강준구 Jun-gu Kang , 박호연 Ho-yeun Park , 유하녕 Ha-nyoung Yoo , 조신영 Shin-young Jo , 이원석 Won-seok Lee , 전태완 Tae-wan Jeon , 신선경 Sun-kyoung Shin

DOI:10.9786/kswm.2020.37.4.253

Abstract

In the past, waste policies’ priority fell in stable treatment. Since the enactment of the Framework Act on Resource Circulation (FARC) in 2018, waste policies have emphasized more the recycling of resources and efficient recovery of energy. On the basis of Appendix 6 of Article 18 of the FARC, an analysis of the combustible contents of mixed waste is now required due to the difficulty in separating combustible and non-combustible waste. This study identified that the optimum conditions for changing various factors such as sample size, quantity, and analysis temperature by waste type. As a result, the size of the sample is 1 mm or less, and the quantity of the sample is 5 g or more. The target waste confirmed the burning temperature to be 300 ~ 600℃, and the analysis temperature of the combustible and ash contents was set at 600 ± 25℃. In addition, standard test methods for the combustible and ash contents in waste are presented.

Key Words

Combustible waste, Particle size and weight, Waste test method

임종훈 Jonghun Lim , 김정환 Junghwan Kim

DOI:10.9786/kswm.2020.37.4.263

Abstract

The wet flue gas desulfurization process, which added the mixing process, was simulated to predict the quality of gypsum, considering a low-grade limestone and waste oyster shell. High-grade limestone with more than 94 wt% CaCO₃ content is used for producing the gypsum with 93 wt% purity that is available for sale. However, low-grade limestone also needs to be used because of resource depletion. Low-grade limestone might not be used because it contains many impurities that reduce the quality of the gypsum; however, it can be used in a mixture with oyster shell. For process modeling, low-grade limestone and oyster shell were mixed through a mixer model and entered the reactor model. The dissolution reaction of CaCO₃, the absorption of SOx, and the crystallization of gypsum were considered in two stages using an equilibrium reactor. Thermodynamic models used the NRTL model for the gas-liquid equilibrium and the van't Hoff solubility method for the solid-liquid equilibrium. For process optimization, the following constraints were set: 93% purity of gypsum, 94% desulfurization efficiency, and 3,710 kg/h in total absorbent usage, and the objective function was set to maximize the mass flow of oyster shell. The maximum blending quantity of low-grade limestone for 2,275 kg/h in waste oyster shell that satisfied the constraints was ~ 1,435 kg. For the economic analysis, the total capital investment (TCI) increased to KRW 545,690,970, but the annual operation and maintenance (O&M) cost decreased to KRW 122,270,721, allowing the payback time to be estimated at approximately 4.5 years.

Key Words

Desulfurization, Limestone, Waste oyster shell, Gypsum, Optimization

변성주 Sung-ju Byun , 이채영 Chae-young Lee

DOI:10.9786/kswm.2020.37.4.275

Abstract

This study was conducted to evaluate the effects of pretreatment on anaerobic hydrogen fermentation of Chlorella vulgaris (C. vulgaris). Ultrasonication (1 to 10 min at 20 kHz) and thermal pretreatment (70 to 150℃ for 20 min) were applied to increase disintegration efficiency and hydrogen yield from C. vulgaris. Optimal results were obtained with a 5-min-ultrasonication followed by thermal pretreatment at 150℃, showing a disintegration efficiency of 59.4%. The highest hydrogen yield was 45.1 mL H₂/g dcw with 5-min-ultrasonication followed by thermal pretreatment at 110℃. This value was about 15 times higher than that obtained without any pretreatment (3.1 mL H₂/g dcw). The results of this study suggested that a combination of ultrasonication and thermal pretreatment on C. vulgaris microalgae could increase the disintegration efficiency and hydrogen yield from C. vulgaris via anaerobic hydrogen fermentation.

Key Words

Hydrogen fermentation, Hydrogen production, Chlorella vulgaris, Ultrasonication, Thermal pretreatment

박휘언 Hwi-eon Park , 장용철 Yong-chul Jang , 김현희 Hyun-hee Kim

DOI:10.9786/kswm.2020.37.4.284

Abstract

In this study, a static and dynamic material flow analysis (MFA) of polybrominated diphenyl ethers (PBDEs) emitted from end-of-life televisions (TVs) was conducted by examining their life cycle. Domestic end-of-life TV waste generation was approximately 200,900 tons. Among them, 42,000 tons of the TV waste was treated in formal ways, but 18,000 tons of the TV waste was treated in informal ways. About 94 tons and 36 tons of PBDEs were emitted from the TV production and use stages, respectively. The amount of PBDEs that are separated from the TV recycling facilities was approximately 57 tons. Cumulative amounts of PBDEs at the production stage was 18,176 tons. Since 2016 there has been no report of PBDEs emitted from cathode ray tube (CRT) TVs during their usage. It was estimated that by 2030 the amount of PBDEs generated from liquid-crystal display (LCD) TVs will be about 39 tons. In the collection and recycling stages, the overall PBDEs emissions were minimum in 2017. The generation of PBDEs emitted from CRT TVs has been decreasing linearly from 2001 to 2017. The predicted emission of PBDEs by LCD TVs will be 37 tons by 2030. This study may help develop a management strategy to properly treat TV wastes.

Key Words

PBDEs, BFRs, TV, Dynamic MFA, Life cycle

조우리 Woori Cho , 김장영 Jang Yeong Kim , 이진주 Jin Ju Lee , 이재영 Jai-young Lee

DOI:10.9786/kswm.2020.37.4.295

Abstract

As an efficient way of reusing sewage sludge as a solid fuel, hydrochars were made from sewage sludge and wood waste via hydrothermal carbonization (HTC). Optimal HTC conditions were determined to be 220℃ for 2 h with varying the ratio of sewage sludge to wood waste. Mixing sewage sludge and wood waste improved the fuel properties (carbonization degree and lower heating value) of the hydrochar. It was determined that the nitrogen content of the hydrochar was decreased by mixing of the products. When the amount of wood waste that was mixed with sewage sludge was low, the ash content was increased. For the efficient reusing of sewage sludge as a solid fuel (hydrochar), more waste wood should be mixed with sewage sludge.

Key Words

Hydrothermal carbonization, hydrochar, Sewage sludge, Wood waste