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DOI : 10.17640/KSWST.2025.33.6.305 , Vol.33, No.6, 305 ~ 315, 2025
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| Title |
| Characterization of Concentrate from Wastewater Reuse Processes and its Further Concentration Treatment by Electrodialysis |
| 김홍석 Hong-suck Kim , 이민지 Min Ji Lee , 김지연 Ji-yeon Kim , 김연권 Youn-kwon Kim |
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| Abstract |
| This study investigates the feasibility of further concentrating reverse osmosis (RO) concentrate generated from a high-recovery wastewater reuse process using electrodialysis (ED). RO concentrate (ROC 90 %) was obtained from the reuse line of sewage treatment plant (STP) A under a 90% water recovery condition. The physicochemical characteristics of ROC 90% were first examined, revealing a Langelier Saturation Index of 1.0, indicating supersaturation and a high potential for calcium carbonate scaling. The silicate concentration was 34.6 mg/L, below the supersaturation threshold, while iron and aluminum were present at trace levels. Dissolved organic carbon analysis indicated that 48% of the organic fraction consisted of molecules smaller than 1 kDa (a size range associated with irreversible membrane fouling). Subsequently, the effect of pH pretreatment on the ED overconcentration performance was evaluated by comparing runs conducted with and without feed pH adjustment. With pH adjustment, ROC 90% was concentrated to a conductivity of 72.5 mS/cm, while the untreated feed reached only 42.4 mS/cm before scaling occurred. These results confirm that pH pretreatment is essential for achieving a high degree of overconcentration. Although the overall salt removal rate was largely independent of pH adjustment, the concentration rate in the pH-adjusted case was more than twice that of the untreated case. This suggests that mechanisms such as back diffusion or membrane charge variation may influence the process and require further investigation. During ED operation with pH-adjusted feed, all three compartments of the ED stack (dilution chamber, concentration chamber, and electrode chambers) exhibited a decrease in pH. These findings indicate the need for active pH control, particularly in the dilution and electrode compartments, to maintain reclaimed water quality and prevent performance degradation of the ED system. |
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| Key Words |
| Concentrate, Electrodialysis(ED), High recovery RO concentrate, pH pre-treatment, Reverse osmosis(RO), 역삼투막, 농축수, 전기투석, 고회수율 RO 농축수, pH 전처리 |
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