민홍 Hong Min , 이수영 Soo-young Lee , 이미연 Miyeon Lee , 이강우 Gangwoo Lee , 조성수 Sung-su Cho

DOI:10.9786/kswm.2025.42.2.59

Abstract

Waste bittern is a by-product generated during the refined salt manufacturing process. It contains higher concentrations of Magnesium (Mg) and Calcium (Ca) than seawater and is attracting attention for its potential application in the mineral carbonation process. However, selective leaching is challenging because Mg²⁺ and Ca²⁺ ions exhibit similar chemical behavior. In this study, we analyzed the composition and physical properties of waste bittern and used computational simulations to examine ion fractionation as a function of pH variations. Subsequently, we attempted to recover Mg²⁺ and Ca²⁺ ions separately by adjusting the pH to different levels. To recover Mg²⁺ ions, a 1 M NaOH solution was added to the waste bittern; as a result, more than 95% of the magnesium was recovered at pH 10-11 in the form of Mg(OH)₂. To recover Ca²⁺ ions, another 1 M NaOH solution was added to the filtrate from which Mg²⁺ ions had been previously removed, raising the pH to 13, and then CO₂ was supplied. The precipitate formed under these conditions consisted of over 95% CaCO₃.

Key Words

Waste bittern, Cation recovery, Magnesium hydroxide, Calcium carbonate

Jihwan Park , Hye Sook Lim , Inchul Go , Sora Yi

DOI:10.9786/kswm.2025.42.2.68

Abstract

The global surge in demand for electric vehicles (EVs) and the rapid growth of the industry have highlighted the need for intensified competition over key raw materials and the stable management of the supply chain. This study aims to assess the effectiveness of policies and identify improvement needs across various stages of the EV battery supply chain through surveys of industry stakeholders. Statistical analyses, primarily using ANOVA and post-hoc tests, revealed significant differences in policy needs across different stages, particularly in downstream activities such as end-of-life diagnostics, recycling, remanufacturing, and reuse. Stakeholders in downstream operations reported greater perceived needs for policy improvements, with an average score of 6.42 on a 7-point Likert scale, significantly higher than those in the upstream (5.72) and midstream (5.61) stages. Additionally, respondents emphasized the need for stronger policy support across three key areas: improving environmental regulations, diversifying raw material supply chains, and developing infrastructure. ANOVA results showed a statistically significant variance in policy improvement needs across supply chain stages (F = 4.84, p ≤ 0.05), particularly regarding performance diagnostics and recycling initiatives related to the management of end-oflife batteries. Post-hoc tests revealed that more intensive regulatory reforms and institutional support are necessary at the downstream stage of the supply chain. These findings suggest that stage-specific policy interventions are necessary to address the unique challenges at each supply chain level. Additionally, they highlight an opportunity to evaluate policy and institutional support downstream battery industry operations while ultimately enhancing the global competitiveness of the supply chain. This study offers evidence-based recommendations to guide policymakers in designing targeted support strategies for promoting sustainable growth within the industry.

Key Words

Electric vehicles (EVs), End-of-life battery, Supply chain, ANOVA, Post-hoc test

임병현 Byung-hyun Lim , 김동욱 Dong-wook Kim

DOI:10.9786/kswm.2025.42.2.82

Abstract

Population growth and rapid economic development have driven the expansion of water supply infrastructure, resulting in increased generation of water treatment sludge. To evaluate the potential of incorporating this sludge into soil within a circular economy framework, contamination levels were assessed for sludge generated from water treatment plants in each watershed. For this evaluation, concentrations of heavy metals in the sludge were measured and classified based on soil contamination standards derived from the Natural Background Concentrations published by the National Institute of Environmental Research in 2022. Contamination coefficient and enrichment index analyses revealed that the Han River watershed demonstrated the lowest levels of heavy metal contamination, while the Yeongsan River and Seomjin River watersheds exhibited the highest levels. Among the heavy metals analyzed, arsenic was identified as the predominant contaminant. Therefore, continuous monitoring of heavy metal concentrations in both raw water and water treatment sludge, along with systematic legal and regulatory improvements, is essential to advancing a circular economy.

Key Words

Water treatment plant, Water treatment sludge, Heavy metal pollution, River basin, Waste recycling

김도완 Do-wan Kim , 임병란 Byung-ran Lim , 김정대 Joung-dae Kim , 박준석 Joonseok Park , 홍인기 In-gi Hong

DOI:10.9786/kswm.2025.42.2.90

Abstract

Statistics play a crucial role in waste management by underpinning policy development and implementation, thereby highlighting the need for accurate and reliable data compilation. However, waste statistics often exhibit anomalies and outliers. Challenges such as double counting, the inclusion of illegally disposed waste, and the aggregation of disaster-related waste into total generation figures hinder accurate interpretation and effective use of the data. This study aims to identify the factors undermining the reliability the national waste statistics in Korea, with a focus on data related to waste generation and treatment. It further investigates the root causes of these statistical inconsistencies and reviews international practices to propose measures for improvements. The findings suggest that “junk shops” should be incorporated into the formal waste management system to ensure proper oversight. Furthermore, illegal waste and disaster-related waste should be managed as distinct categories, reflecting their unique characteristics and statistical implications, as demonstrated by the approach adopted in Japan. To prevent double counting, waste generated at treatment facilities that does not undergo a compositional change―such as secondary waste from shredding, crushing, or drying―should be excluded from reporting or managed separately, consistent with practices adopted in the European Union. Finally, given the recurring errors in the current statistical compilation system, this study highlights the need for a more advanced digital data entry platform and a three-stage verification process involving local governments, the Korea Environment Corporation, and an expert review panel to improve the accuracy and reliability of national waste statistics.

Key Words

Waste statistics, Junk shop, Double counting, Illegal waste, Disaster waste

정상언 Sang-un Jeong , 이선주 Sun-ju Lee , 장진만 Jin Man Chang , 이승택 Seungtaek Lee , 이재영 Jai-young Lee

DOI:10.9786/kswm.2025.42.2.103

Abstract

Hydrothermal carbonization (HTC) has gained attention as a sustainable method for converting biomass into energydense materials. This process occurs at relatively low temperature ranges (180-260°C) in high-pressure sealed environments. However, a well-known limitation of HTC is the reduced yield of hydrochar, leading to ongoing efforts to explore alternative solutions. Current approaches focus on modifying operational parameters and incorporating catalysts to address this challenge. Therefore, this study aims to investigate the integration of the cooling-reheating (CRH) process as a complementary method to the HTC process. The CRH process is well-documented for its ability to redistribute carbides and form fine spherical structures in alloys. Preliminary studies suggest that applying CRH to biomass may enhance its energy yield. This study examines how integrating the CRH method into the HTC process affects the physicochemical properties of hydrochar derived from wood waste. The analyses conduced included ultimate analysis, calorific value assessment, and specific surface area measurement. The results indicated that integrating the CRH process improved both solid yield and calorific value compared to the standalone HTC process. Additionally, the fixed carbon content increased slightly, while ash content decreased by up to 17.6%. Specific surface area measurements demonstrated consistent enhancements, with the most significant improvement―a 1.52-fold increase―observed at 260°C.

Key Words

Wood waste, Hydrothermal carbonization, Cooling-reheating, Calorific value, Specific surface area

김나원 Nawon Kim , 이가영 Gayeong Lee , 김용진 Yong-jin Kim

DOI:10.9786/kswm.2025.42.2.112

Abstract

Leachate treatment facilities are designed to remove pollutants from leachate, but their effectiveness in removing emerging contaminants such as microplastics (MPs) remains uncertain. In this study, three leachate treatment facilities near M-city were selected for regular long-term sampling. The goal was to determine whether MPs are continuously discharged in leachate and to analyze their behavior throughout the treatment process. At Facility C in particular, a total of five samples were collected from different stages of the treatment process: raw leachate, effluents from primary and secondary sedimentation tanks, final treated leachate, and dewatered sludge cake. These samples were used to evaluate the fate and removal efficiency of MPs. Additionally, MPs concentrations were analyzed before and after rain events to assess the correlation between rainfall and MPs levels, as well as the impact of rainfall on MPs mobility in leachate. The results of confirmed that MPs were consistently detected in both raw and treated leachate each month. MPs concentration decreased as the leachate underwent the treatment process. The highest MPs concentration was found in the dewatered sludge cake, suggesting that MPs likely settled and were transferred into the sludge during treatment. Despite a weak correlation between increased rainfall and higher MPs concentrations in leachate, the difference was not statistically significant.

Key Words

Landfill leachate, Leachate treatment facility, Microplastics, Behavior