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CONTENTS
Volume 12, Number 4, July 2021
 


Abstract
The effects of the order of chemical cleaning protocols on the removal of hollow fiber ultrafiltration (HUF) membrane foulants, and restoration of membrane surface properties, were identified through autopsies of fouled HUF membrane modules from a pilot-scale surface water treatment system (Hongcheon-gun, Kangwon province, Republic of Korea). Quantitative and qualitative differences in the extracted HUF membrane foulants were found to depend on the types of chemical cleaning protocols applied, the consecutive cleaning protocol II (CP II; 0.1 N NaOH -> 0.1 N HCl; the sum of DOC = 215.19 mgC m⁻2; the sum of TN = 17.82 mg N m⁻2; the sum of metals = 25.14 mg m⁻2) extracted both organic and inorganic foulants from HUF membrane surfaces more effectively than consecutive cleaning protocol I (CP I: 0.1 N HCl -> 0.1 N NaOH; the sum of DOC = 189.89 mg C m⁻2; the sum of TN = 13.66 mg N m⁻2; the sum of metals = 9.95 mg m⁻2). Furthermore, the surface morphological characteristics of the cleaned HUF membrane using CP II were relatively similar to the virgin membrane surface compared to those of the cleaned HUF membrane using CP I. These findings demonstrated that the sequential coupling of two different chemical cleaning protocols played critical roles in removing organic and inorganic foulants from the fouled HUF membrane surfaces and restoration of membrane surface elementary composition potentially related to HUF membrane performances.

Key Words
consecutive chemical cleaning; membrane autopsy; membrane fouling; pilot-scale surface water treatment plant; ultrafiltration

Address
Yong-Gu Lee: Department of Environmental Engineering, College of Art, Culture, and Engineering, Kangwon National University, Kangwondaehak-gil 1, Chuncheon-si, Gangwon-do 24341, Republic of Korea

Hojung Rho: Department of Land, Water and Environment Research, Korea Institute of Civil Engineering and Building Technology, 283 Goyang-Daero, Ilsanseo-gu, Goyang-si, Gyeonggi-do 10223, Republic of Korea

Sangwon Kim, Jaegwan Shin and Kangmin Chon: Department of Environmental Engineering, College of Art, Culture, and Engineering, Kangwon National University, Kangwondaehak-gil 1, Chuncheon-si, Gangwon-do 24341, Republic of Korea/ Department of Integrated Energy and Infra system, Kangwon National University, Kangwondaehak-gil 1, ChunCheon-si, Gangwon-do 24341, Republic of Korea

Kangmin Chon: Technology Research Laboratory, Kolon Global Corporation, 11 Kolon-ro, Gwacheon-si, Gyeonggi-do 13837, Republic of Korea




Abstract
Electrodialysis (ED) is an advanced separation process used to treat industrial wastewater using potential differences. In this study, flow rates within the stack were increased by creating a flow channel to increase the limiting current density (LCD). Increasing the flow rate within the stack increases the diffusion flux, which leads to an increase in LCDs. Experiments show that the applied voltage of the flow-accelerated stack was improved by 12.2% compared to the stack without a flow channel, but the LCD decreased by 3.6%. The removal efficiency of both copper and nickel between the two stacks was greater than 95.6%, with no significant difference. However, the concentration rate of ions was superior in the stack without a flow channel. This may be attributed to the fact that the applied voltage increases when the channel is attached, resulting in differences in the separation rate and the resulting concentration polarization. In terms of the current efficiency, the channel-less stack was found to be 42.5% better than the channeled stack. It would be desirable to apply voltages below the LCDs as those exceeding LCDs at the same membrane flow rate would significantly reduce the economic feasibility.

Key Words
current efficiency; channeled stack; economic feasibility; electrodialysis; limiting current density

Address
Kyung Jin Min: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea/ Plagen Co. Ltd., 58 Wangsimni-ro, Seongdong-gu, Seoul 04778, Korea

Joo Hyeong Kim, Sun Wouk Kim, Seunghyun Lee and Ki Young Park: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea

Hyun-Gon Shin: Department of Energy and Environmental Engineering, Shinhan University, Gyeonggi-do 480-857, Korea

Abstract
The electrochemical reduction of nitrate using a divided electrolytic cell in combination with Zn cathode and (Pt)/Ti anode reduced the high concentrations of nitrate (1,000 mg NO3-N/L). A proton exchange membrane (Nafion-117) was used to increase the nitrate reduction efficiency by preventing the re-oxidation of nitrite produced during the reduction process. The current density and anolyte concentration, considered as parameters, were tested to assess the electrochemical reduction of nitrate. The reduction of nitrate shortened the electrolysis time in proportion to the current density, and the time for 90% removal was 5 h at 5 mA/cm2, 3 h at 10 mA/cm2, and 1.8 h at 20 mA/cm2. The yields of ammonia were approximately 50%-55% of the initial nitrate-nitrogen concentration regardless of the current density and was insignificantly related to the anolyte concentration.

Key Words
anolyte concentration; divided electrolytic cell; electrodialysis; limiting current density; proton exchange membrane

Address
Ho Young Cha: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea / Department of Civil and Environmental Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea

Youngho Park, Kee-Won Seong and Ki Young Park: Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea



Abstract
Monosodium glutamate (MSG) was evaluated as a draw solute (DS) of forward osmosis–nanofiltration (FO-NF) process for sewage thickening. Water flux (Jw) and reverse draw solute flux (Js) through FO membrane with MSG were compared to those with NaCl as the reference DS. In addition, the influence of MSG to anaerobic digestion of concentrated sewage for methane gas production was investigated. The Js/Jw for MSG was 0.0015mol/L at 1M of initial concentration with a CTA(HTI) membrane, which was 6 % of that for NaCl, while the water flux (Jw) for MSG (ca. 10 L/m2h) was comparable to that for NaCl in FO processes. MSG recovered up to 98% by NF process, which changed with applied membrane and MSG concentration. The collected primary effluent from the full-scale wastewater treatment plant was thickened up to nine times in terms of volumetric concentration factor. The physical membrane flushing by a water could effectively recover the flux. The inhibitory effects of MSG on anaerobic methane production could be negligible and the gas production potential increased.

Key Words
anaerobic toxicity assay; forward osmosis; monosodium glutamate; nanofiltration; reverse solute flux; sewage thickening

Address
Seungheon Yang, Taaekguen Yun, Soon Bum Kwon and Seockheon Lee : Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea/ Advanced Environmental Science, Energy Environment Policy and Technology, KU-KIST Green School, Graduate School of Energy and Environment, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

Kyungjin Cho and Seongpil Jeong: Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea

Seungkwan Hong: Advanced Environmental Science, Energy Environment Policy and Technology, KU-KIST Green School, Graduate School of Energy and Environment, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea


Abstract
Water scarcity issue becomes severe due to climate change and increase of water needs, globally. In order to provide fresh water in islands, small-scale desalination plants (< 100 m3/day) had been installed using reverse osmosis technology. To decrease high desalination cost of small-scale SWRO plants in islands in Republic of Korea, the desalination vessel having RO system (300 m3/day) was recently suggested. The desalination costs of the small-scale SWRO plants in islands and desalination vessel which can provide desalinated water to several islands were analyzed and were compared. The operational schedule of the desalination vessel in Shinan-gun, Republic of Korea was suggested considering the water demands, velocity and water storage of the desalination vessel, and distances between target islands. It was found that the water production cost could be saved when the desalination vessel was applied in Shinan-gun, Republic of Korea.

Key Words
cost analysis; desalination vessel; reverse osmosis (RO); small-scale desalination; vessel routes

Address
Hien Thi Nguyen, Kyungjin Cho and Seongpil Jeong: Division of Energy & Environment Technology, KIST school, Korea University of Science and Technology, Seoul 02792, Republic of Korea/ Water Cycle Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea

Am Jang: Graduate School of Water Resources, Sungkyunkwan University, Jangan-gu, Suwon, Gyeonggi-do 440-746, Republic of Korea

Abstract
Per- and poly-fluorinated compounds (PFCs) are persistently found during drinking water treatment processes, which can also be found in tap water. However, the mechanisms for removing PFCs during drinking water treatment processes have not been fully understood. In this study, we investigated the effect of coagulation on the removal of short- and long-chain PFCs. The PFCs mixture (C5–C10) resulted in a lower removal efficacy via coagulation treatment, and the average removals of selected PFCs were found to be below 5%. Only long-chain perfluorodecanoic acid (PFDA) (C10) and perfluorooctanesulfonic acid (PFOS) were significantly removed via coagulation. The removals of suspended particles and bacterial cells via coagulation were correlated with the reduction of PFDA and PFOS. However, higher turbidity, humic substances, and biopolymers in the source water were found to significantly reduce the removal efficiency of PFDA and PFOS, resulting in insignificant changes between the PFC species. We concluded that coagulation was not effective in removing selected PFCs, hence, a multiple-barrier treatment strategy is needed for PFC removal.

Key Words
chain length; coagulation; perfluorinated compounds

Address
Ji Won Park, Jin Hyung Noh, Seon Won Yoon, Samiya and Sung Kyu Maeng : Department of Civil and Environmental Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Republic of Korea

Byeong Gyu Choi: Water Supply and Sewerage Research Division, Environmental Infrastructure Research Department,
National Institute of Environmental Research, Hwangyong-ro 42, Seogu, Incheon, 22689, Republic of Korea

Gyoo-Bum Kim: 3Department of Construction Safety and Disaster Prevention, Daejeon University, Daehak-ro 62, Dong-gu, Daejeon, 300-716, Republic of Korea

Heekyong Oh: Convergence Technology Research Team, Daewoo Institute of Construction Technology, 170 Eulji-ro, Jung-gu, Seoul, 04548, Republic of Korea




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