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CONTENTS
Volume 16, Number 2, March 2025
 

Abstract
Water and wastewater treatment remain at the forefront of global environmental challenges, driving the need for innovative and sustainable solutions. This special issue explores cutting-edge research on membrane technology, process intensification, and emerging treatment strategies to address pressing concerns such as hydrophilicity enhancement, high-strength wastewater treatment, resource recovery, and microplastic removal. The included studies provide insights into diverse aspects of water treatment: from surface modification of poly(tetrafluoroethylene) (PTFE) membranes for improved hydrophilicity to the feasibility of aerobic granular sludge (AGS) for treating anaerobic digestate. Additionally, novel approaches such as CO2 absorbent-based draw solutions in forward osmosis, dissolved air flotation for microplastic removal, and solvent extraction desalination under varying conditions are explored. By presenting these advancements, this special issue aims to contribute to the ongoing development of more efficient, resilient, and environmentally friendly water treatment technologies, offering valuable perspectives toward sustainable water management.

Key Words


Address
Youngjin Kim: Department of Environmental Engineering, College of Science and Technology, Korea University, 2511, Sejong-ro, Sejong, 30019, Republic of Korea


Abstract
Poly(tetrafluoroethylene) (PTFE) microfiltration membranes were chemically modified with a two-step chemical reaction. The membranes were defluorinated through controlled etching with sodium-naphthalene solution, and then sulfonated using chlorosulfonic acid. The effects of surface modification on the morphology, pore size and distribution, ion-exchange capacity (IEC), hydrophilicity, pure water flux, and fouling of the membrane were investigated. Using X-ray photoelectron spectroscopy (XPS), the surface composition of the sulfonic acid groups on the modified PEFE membranes was analyzed. As the degree of sulfonation increased, the IEC and hydrophilicity of the membranes increased without any deformation of the morphology or pore size, as observed by scanning electron microscopy (SEM) and capillary flow porometry under controlled reaction conditions. It was also observed that the flux of pure water increased with decreasing intrinsic resistance as the degree of sulfonation increased. Membrane fouling with humic acid was suppressed with an increasing degree of sulfonation, because of enhanced electrostatic repulsion between the negatively charged surface and negative charged humic acid.

Key Words
hydrophilicity; microfiltration; microporous and porous membranes; morphology; surface modification

Address
Seul Ki Lee: Department of Environmental Engineering and Energy, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin-si, Gyeonggi-do, 17058, Republic of Korea/ Econity Inc., 2374-41, Jungbu-daero, Yangji-myeon, Cheoin-gu, Yongin-si, Gyeonggi-do 17162, Republic of Korea

Yun Chul Woo: Department of Environmental Engineering and Energy, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin-si, Gyeonggi-do, 17058, Republic of Korea

Bumsuk Jung: Department of Environmental Engineering and Energy, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin-si, Gyeonggi-do, 17058, Republic of Korea/ Department of Semiconductor Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin-si, Gyeonggi-do, 17058, Republic of Korea


Abstract
This study aimed to evaluate organic matter and nitrogen removal by the aerobic granular sludge (AGS) process for high-strength liquid anaerobic digestate from an actual resource recovery facility. Specifically, the effect of different hydraulic retention time (HRT) on organic matter and nitrogen removal was investigated. The results revealed that the system operated with a HRT of 10.5 days, achieving an organic loading rate (OLR) of 0.54 kg-COD/m3/d and an organic matter removal rate of 64%. The organic matter removal efficiency of the AGS improved as the OLR increased. Finally, the organic matter removal efficiency achieved 73% at an OLR rate of 0.94 kg-COD/m3/d. However, the nitrification efficiency was maintained at 99.9% even though the nitrogen loading rate was increased. In the ozone reactor, organic matter removal efficiencies were relatively low due to the presence of refractory organic matter. The specific nitrification rate (SNR) value was calculated to be 0.121 kg NH4⁺-N/kg MLVSS/day, while the specific denitrification rate (SDNR) value measured 0.228 kg NO3⁻-N/kg MLVSS/day. This study demonstrates the applicability of the AGS process for the treatment of high-strength liquid anaerobic digestate and provides basic operating parameters for process design.

Key Words
aerobic granule sludge; denitrification; kinetics; liquid anaerobic digestate; nitrification; ozone

Address
Myungchan Kim and Hanna Choi: Technology research team, Taeyoung E&C, 111, Yeouigongwon-ro, Yeongdeungpo-gu, Seoul, Republic of Korea

Sungju Im: Department of Environmental Engineering, Gyeongsang National University, Jinju 52725, Republic of Korea

Duksoo Jang: Department of Civil and Environmental Engineering, Hanbat National University, Daejeon 34158, Republic of Korea

Abstract
This study investigates the feasibility of using sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3), by-products of carbon dioxide (CO2) capture processes, as draw solutions (DSs) in forward osmosis (FO) systems. The primary objectives were to evaluate the basic performance of these DSs, analyze membrane fouling behaviors, and assess economic feasibility. The FO process demonstrated superior water flux performance with Na2CO3, attributed to its high osmotic pressure, followed by NaHCO3 and sodium chloride (NaCl). Fouling analysis revealed that Na2CO3 mitigates fouling due to its alkaline nature, which inhibits biofouling and scaling. Economic evaluations confirmed Na2CO3 as the most cost-effective DS, offering significant cost savings over NaHCO3 and NaCl at all recovery levels. These findings highlight the potential of Na2CO3 as a sustainable and efficient DS for wastewater treatment and other FO applications, emphasizing its compatibility with CO2 capture technologies.

Key Words
adsorbent; carbon capture; domestic wastewater; draw solution; forward osmosis

Address
Sehyuk Ahn and Ihn-Sup Han: School of Environmental Engineering, University of Seoul, Siripdae-gil 13, Dongdaemun-gu, Seoul, 02504, Republic of Korea

Jieun Kim, Jeongkyun Yu and Youngjin Kim: Department of Environmental Engineering, College of Science and Technology, Korea University, 2511, Sejong-ro, Sejong, 30019, Republic of Korea

Hyunsup Jang: Environmental Forensic Lab, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Republic of Korea

Sangyoup Lee: Institute of Conversions Science, Korea University, 145, Anam-ro, Sungbuk-gu, Seoul 02841, Republic of Korea

Abstract
In the current study dissolved air flotation has been applied to verify the removal characteristics in drinking water treatment processes. Various aspects of microplastic, and water quality conditions were tested using dissolved air flotation to determine the removal efficiency and mechanism of microplastics. To simulate DAF processes under practical conditions, the type and size of microplastics were set based on the water quality conditions of a river, and the experiments were conducted under similar water quality conditions. For the microplastics used in the experiments various size, and densities were tested to verify its removal characteristics. Different pollutant type and concentrations were also tested with microplastic to verify the removal rate and mechanism during the flotation process. To better understand the removal of microplastics, different type and concentration of coagulants were also used in the system to better understand the removal mechanism. Finally the transport of various heavy metals were also verified to better understand the effects of organic pollutant's effect on heavy metal transport in the system. Results showed a correlation with the microplastic flotation capacity and removal rates. Effects of organic matter showed a high impact on the removal mechanism, where the increased amount of organic matter resulted in lower removal rates. The amount of organic matter also influenced the ate and transport of heavy metal sorption and transport on microplastic surfaces, indicating a higher hindrance of sorption capacity due to chelating effects.

Key Words
dissolved air flotation; fate and transport; heavy metal sorption; micropastic; microplastic coagulation

Address
Won Hyeong Seo: Department of Environmental & IT Engineering, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea

Byeong-Gyu Choi: Nakdong River Environment Research Center, National Institute of Environmental Research, Chilgok-gun, Gyeongsangbuk-do 39914, Republic of Korea

Soohoon Choi: Department of Environmental Engineering, Chungnam University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea


Abstract
This study investigates the performance of solvent extraction desalination (SED) using three amine solvents DPA, DIPA, and DBA under various temperature and ion valency conditions. The results revealed that reaction and separation temperatures significantly influenced water recovery and salt removal efficiencies. DIPA demonstrated the highest water recovery, while DPA exhibited superior salt removal efficiency. Mg2⁺ was effectively removed through a precipitation mechanism, distinct from the polarity-driven removal of sodium chloride. Additionally, reuse experiments over nine cycles showed stable performance in water recovery and salt removal, emphasizing the economic and operational feasibility of SED. These findings highlight the adaptability and potential of SED as a membrane-free desalination technology for high-brine scenarios, offering a sustainable alternative for seawater and brine treatment.

Key Words
amine solvents (DPA, DIPA, DBA); magnesium ion (Mg2⁺) removal; solvent extraction desalination; salt removal efficiency; solvent reuse; water recovery efficiency

Address
Gyeong-soo Kim and Doo-il Kim: Civil and Environmental Engineering, Dankook University, 152, Jukjeon-ro, Suji-gu, Yongin, Gyeonggi-do, 16890, Republic of Korea

Oh Kyung Choi: Bio Resource Center, Institute for Advanced Engineering, 175-28, Goan-ro, Baegam-myeon, Cheoin-gu, Yongin 17180, Republic of Korea

Gyu Dong Kim: Technology Advancement & Commercialization, RTI International, 3040 East Cornwallis Road, Research Triangle Park, NC, 27713, USA

Jae Woo Lee: Environmental Engineering, Korea University, 2511 Sejong-ro, Sejong City, 30019, Republic of Korea

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