김용진 Yong-jin Kim

DOI:10.9786/kswm.2022.39.3.185

Abstract

This study analyses, the characteristics of plastics as adsorbents and the mechanisms of adsorption between plastics and hydrophobic organic pollutants (HOPs). As the characteristics of the adsorption material, the degree of crystallinity, glass transition temperature, and contact angle with water of the plastics were investigated, and influence factors on the adsorption of various HOPs and the role of plastics as a carrier of HOPs were suggested. As factors affecting the adsorption of organic pollutants onto plastics, the physical and chemical properties of the plastic as adsorption material (i.e. size, polarity, crystallinity, glass transition temperature, presence and type of functional groups, etc.), characteristics of organic pollutants (i.e. concentration, hydrophobicity, surface charge, functional groups, etc.) and water quality (i.e. pH, temperature, ionic strength, coexisting organic pollutants, etc.) are presented. As a result, it was confirmed that organic pollutants are transferred/diffused not only in the organisms but also throughout the world due to plastic wastes in marine.

Key Words

Marine microplastics, Hydrophobic organic pollutants (HOPs), Adsorption material, Crystallinity, Glass transition temperature

장용철 Yongchul Jang , 손민희 Minhee Son , 박주영 Jooyoung Park

DOI:10.9786/kswm.2022.39.3.194

Abstract

As one of the world's top producers and top consumers of plastics, Korea has been experiencing problems with regard to the management of waste plastics since 2018, such as collection service disruptions, illegal abandonment and exports of waste, and marine pollution. To gain a complete understanding of Korea's contemporary management of plastics, this study quantified national plastic flows across production, use, and end-of-life management between 2017 and 2019. In 2017, Korea produced 17.5 million metric tons of plastic resins, more than half of which was exported, and consumed 7 million metric tons of plastic products including 3.2 million metric tons of packaging. On a per-capita basis, Korea's plastic consumption and waste generation were higher than that of other major economies, such as Japan, China, the United States, and Europe, which implies considerable potential for plastic consumption reduction. Despite the high level of waste generation, Korea has increased the level of material recycling while minimizing the landfill rate by implementing various policies, such as waste levies, voluntary agreements, and extended producer responsibility. For more sustainable plastic management, Korea must make additional efforts to reduce plastic consumption and promote high-quality recycling, for example through circular design, business models with less packaging, and advanced technologies.

Key Words

Plastics, Material flow analysis, Korea

이준규 Jun-kyu Lee , 김민정 Min-jung Kim , 박윤수 Yoon-soo Park , 김태성 Tae-sung Kim , 전태완 Tae-wan Jeon , 최효현 Hyo-hyun Choi

DOI:10.9786/kswm.2022.39.3.207

Abstract

This study evaluated the explosive hazardous properties and the likelihood of dust explosion in four types of waste dust collected from industrial sites. Waste dust samples were collected from the cement manufacturing industry, aluminum, and aluminum alloy ingot manufacturing industry, and copper alloy and non-ferrous product manufacturing industry. We evaluated whether the dust waste contained explosive substances using a standard method. Additionally, the factors that may affect the dust explosion, the presence of combustible substances, average particle size, particle size distribution, particle shape, moisture content, and calorific value were also evaluated. It was confirmed that the likelihood of dust explosion of dust waste generated in the aluminum and aluminum alloy manufacturing industry is higher than that of dust waste generated in other industries.

Key Words

Waste dust, Dust explosion, Explosiveness, Evaluation

이혜성 Hye-sung Lee , 김용진 Yong-jin Kim

DOI:10.9786/kswm.2022.39.3.217

Abstract

An increase in plastic on the sea surface may affect the absorption depth of solar radiation energy, resulting in changes in the sea surface temperature (SST), stratification, and mixed layer depth. This study evaluated the relationship between the rise of SST according to the concentration of plastic on the sea surface, as well as the effects of these temperature increases on phytoplankton concentrations and climate change. Low-density polyethylene (LDPE) has lower specific heat than water. Therefore, adding LPDE to distilled water increased the heating rate of the water, and significant differences were observed between the temperatures of LPDE-treated and untreated distilled water. Furthermore, our findings suggested that the water temperature was affected by the total amount of added LDPE regardless of the size of the LDPE. The concentration of Chl-a in seawater tended to increase as the amount of added LDPE increased. Therefore, ocean plastic will increase the SST, which, in turn, increases phytoplankton, and, again, the increased phytoplankton densities are likely to increase SST. This chain effect could exacerbate climate change.

Key Words

Plastics, Microplastics, Sea surface temperature, Heat build-up, Climate change

강신영 Shin Young Kang , 이지애 Ji Ae Lee , 양명석 Myungseok Yang , 박세원 Se Won Park

DOI:10.9786/kswm.2022.39.3.225

Abstract

The amount of synthetic resins in household waste, generated 7850.7 tons/day in South Korea, in 2020. As an effort to reduce disposable plastic waste, multi-use container related businesses are being promoted both at the domestic and international levels. In this basic study of infrastructure, a perception analysis of consumers and merchants was conducted through a survey to spread the use of multi-use containers in Korea. The survey sample included 800 consumers (300 from Seodaemun-gu; 500 from other regions) and 311 merchants (Seodaemun-gu) of Seoul. The survey was divided into three categories: “Usage/Operation status of food delivery service,” “Awareness regarding using multi-use containers,” and “Attitudes towards multi-use container infrastructure.” The results regarding “usage/operation status” of both consumers and merchants indicate that they were aware that the high proportion of delivery order frequency and sales is impacting their lives in diverse ways, and of the seriousness of the generation of disposable wastes. In terms of “Awareness of using multi-use containers,” the hygiene management of multi-use containers and partnership of infrastructure-related institutions were considered important. For important factors in standardizing containers, stainless steel was considered useful for sauces, side dishes, and stew/soups, and standardization of size needed to be prioritized. In addition, consumers' appropriate deposit level and convenience of return needed to be considered together. “Attitudes towards multi-use container infrastructure” displayed an the overall neutral attitude, although consumers had a slightly higher business affinity than merchants. In order to induce participation, it is necessary to consider providing incentives as well as granting responsibility for solving environmental problems. In the future, system improvement for standardization, such as establishing a logistics system and hygiene standards, should be carried out with pilot projects.

Key Words

Delivery waste, Multi-use container, Infrastructure, Survey, Perception analysis

조수진 Soojin Cho , 최자형 Jahyung Choi , 강영렬 Youngryeol Kang , 전태완 Taewan Jeon , 엄남일 Namil Um

DOI:10.9786/kswm.2022.39.3.239

Abstract

Microplastics (MPs) are being widely detected in various ecosystems, including aquatic and terrestrial environments, which highlights the importance of MP management. MPs are released into the marine environment in various ways. Therefore, our study sought to characterize MPs discharged from different waste treatment facilities. This study focused on by-products of recycling facilities for synthetic polymer, synthetic fiber, rubber, and tire waste. The MPs in the samples were quantitatively and qualitatively analyzed using TED-GC-MS and FTIR. The TED-GC-MS analysis results were as follows: Waste of Synthetic Polymer 2.02 μg/g (PP 1.46 μg/g, PE 0.56 μg/g), Waste of Synthetic Fiber 66.75 μg/g (PET 66.75 μg/g), Waste of Rubber N.D., Waste of Tyre 18.71 μg/g (PP 17.79 μg/g, PS 0.74 μg/g). The FTIR analysis results were divided into three sections: 0.02-0.1 mm (Section 1), 0.1-0.5 mm (Section 2), and 0.5-5.0 mm (Section 3). The number of microplastics for each sample was analyzed for WSP 24.01 ea/g (Section 1: 19.11 ea/kg, Section 2: 3.92 ea/ kg, Section 3: 0.98 ea/kg), WSF 501.44 ea/g, (Section 1: 302.40 ea/kg, Section 2: 187.02 ea/kg, Section 3: 12.02 ea/kg), WRB 10,510.01 ea/g (Section 1: 6,320.58 ea/kg, Section 2: 3,661.20 ea/kg, Section 3: 528.23 ea/kg), WTY 311.52 ea/ g (Section 1: 205.53 ea/kg, Section 2: 104.61 ea/kg, Section 3: 1.38 ea/kg). Therefore, a managements plan for waste treatment facilities must be prepared to reduce microplastics in Korea. Our findings provide a basis for the creation of such a plan in the future.

Key Words

Microplastics, Plastic waste, Recycling facilities, Analysis, FTIR/TED-GC-MS

송재준 Jea-jun Song , 정진도 Jin-do Chung

DOI:10.9786/kswm.2022.39.3.256

Abstract

This study was conducted to derive operating conditions for biological wastewater treatment targeting highconcentration dry condensate generated in the drying process of food waste. In the biological treatment of dry condensate, lab. scale (40 L/d) bioreactor was manufactured and used in the study to evaluate the water quality of the treated water according to the change in operating conditions and to derive stable operating factors. Changes in the influencing factors inside the aeration tank according to the change of BOD load, hydraulic retention time (HRT) and F/M ratio were observed during the operation of the lab. scale bioreaction process. Thereafter, the treatment efficiency was evaluated by measuring the water quality concentration of the treated water. As a result of the study, the water quality of the treated water was BOD 71.14 ± 10.19 mg/L, TOC 49.54 ± 9.64 mg/L, T-N 33.78 ± 5.00 mg/L, T-P 3.35 ± 1.24 mg/L was evaluated as the highest treatment efficiency, under the HRT 5 day, BOD Load 0.30 ± 0.02 kg BOD/d, F/M ratio 0.40 ± 0.02 kg BOD/kg MLSS/d operating condition. It is concluded that the results of this study can be used as data for ensuring stable treated water quality and complying with the emission standards at real plant.

Key Words

Food waste, Dry condensate, Biological treatment, Operating condition, Influence factor

박상혁 Sang Hyeok Park , Abu Hanifa Jannat , 황석환 Seokhwan Hwang

DOI:10.9786/kswm.2022.39.3.267

Abstract

Korea recycles approximately four million tons of food waste (FW) annually. Around 80% of this waste is treated as animal feed and compost. As the demand for animal feed and compost from FW decreases, there is an increasing need to find innovative solutions for this waste. Anaerobic digestion (AD) is currently the most realistic solution, and Korea has plans to construct more AD facilities by 2030. Before these facilities can be built, it is essential to study the indicators and frequencies representative of the characteristic changes in FW. The current literature is lacking in this area, as many studies only focus on a few critical indicators over short periods of time. This study aims to overcome this lack of information by analyzing two processes. The first process analyzes the monthly and seasonal variations in FW characteristics of Pohang city for one year. Biochemical methane potential (BMP) tests were performed, and their data was analyzed to provide basic information for AD design. The second process evaluates different methods of estimating methane production to determine which is the most suitable. The FW characterization study was conducted twice a month and the BMP analysis was conducted once a month. An analysis of the physicochemical parameters for one year indicated an average pH of 4.82, an average moisture content of 80.68%, an average volatile solid (VS) value of 174.48 g/L, an average chemical oxygen demand (COD) of 275.48 g/L, the average carbohydrate, protein, and lipid contents in VS basis were 41.87%, 33.59 %, and 14.34% respectively, and the average BMP was 259.97 ± 12.96 mL/g COD. Principal component analysis of FW characteristics resulted in two significantly different clusters - one for winter and spring and the other for summer and fall. The ANOSIM R-value for these characteristics was 0.821 (p < 0.01). Methane production levels were estimated from FW characteristics using COD, organic composition, and heat value basis. The data indicated that estimating methane production from FW using an organic composition basis rendered more accurate results than the other two methods. These results are beneficial for designing and managing food waste using AD processes as understanding the substrate characteristic change is important to maintaining stability.

Key Words

Anaerobic digestion, Food waste, Food waste characteristics, Biochemical methane potential

원민희 Minhee Won , 조우리 Woori Cho , 장진만 Jin Man Chang , 박지수 Park Ji Soo , 이재영 Jai-young Lee

DOI:10.9786/kswm.2022.39.3.280

Abstract

The market for activated carbon is growing due to environmental awareness and strengthening of environmental regulations. Biochar is a solid carbide that is produced through a hydrothermal carbonization (HTC) process. Wood is an ideal raw material for activated carbon and biomass waste wood because it has low energy consumption rates and does not require pre-treatment to remove moisture. The activated carbon samples in this study were prepared by a chemical activation process using KOH, which is mainly used for activation. The study analyzed the specific surface area, pore volume, pore size, and pore distribution by selecting four samples with high iodine adsorption capacity among the prepared activated carbon samples. The specific surface area for all four samples was between 1192.2 and 1387.1 m²/g, all of which were over 1,000 m²/g, and the pore volume was between 0.6510 and 0.8030 cm³/g. During this process, micropores with an average pore size of 21 to 25 A were formed. SEM photography revealed that these pores were uniform and that the number of pores increased according to activation levels of the carbon samples. When the iodine adsorptivity and specific surface area of commercial activated carbon was compared with that of activated carbon prepared by waste wood biochar with KOH, the specific surface area was higher in the activated carbon samples prepared by waste wood biochar with KOH. These results indicate that the adsorption of activated carbon by waste wood biochar with KOH is successful when applied to activated carbon samples.

Key Words

Activated carbon, Wood waste, Bio-char, Hydrothermal Carbonization(HTC), KOH activation

Yun-min Song , Jong-hyuk Seok

DOI:10.9786/kswm.2022.39.3.290

Abstract

This paper presents an economic application of Fenton oxidation process to biological treatment effluent containing high-strength nitrite and refractory organics. To cope with two major drawbacks in applying Fenton oxidation process to the nitrite-rich effluent simultaneously, i.e. expensive reagent and excessive sludge production, we examined two pretreatment methodologies prior to the application of Fenton process in the following way. First, residual nitrite in the biologically treated leachate (BTL) was removed with iron-catalyzed air oxidation (ICAO) as a cost-effective pretreatment. The time necessary for ICAO reaction is approx. 5 hr. Secondly, to reduce organic loads iron sludge was regenerated for an alternative coagulant. With the regenerated iron sludge, the dose of Fenton’s regent can be reduced by half to remove residual COD in the BTL.

Key Words

Fenton oxidation, Biologically treated leachate (BTL), Iron-catalyzed air oxidation (ICAO), Nitrite, Sludge reuse