Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
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The Air-stripping Process Conjugated with the Ultrasonic Treatment to Remove TOC in Groundwater around the LPG Underground Storage Cavern

탈기법과 초음파 처리법을 연계한 LPG 지하공동저장소 주변 오염지하수 내 TOC 제거

  • Han, Yikyeong (Major of Environmental Sciences, Division of Earth Environmental System Science, Pukyong National University) ;
  • Jun, Seongchun (GeoGreen21 Co. Ltd.) ;
  • Kim, Danu (Major of Environmental Sciences, Division of Earth Environmental System Science, Pukyong National University) ;
  • Jeon, Soyoung (Major of Environmental Sciences, Division of Earth Environmental System Science, Pukyong National University) ;
  • Lee, Minhee (Major of Environmental Sciences, Division of Earth Environmental System Science, Pukyong National University)
  • 한이경 (부경대학교 지구환경시스템과학부 환경지질과학전공) ;
  • 전성천 (지오그린21) ;
  • 김단우 (부경대학교 지구환경시스템과학부 환경지질과학전공) ;
  • 전소영 (부경대학교 지구환경시스템과학부 환경지질과학전공) ;
  • 이민희 (부경대학교 지구환경시스템과학부 환경지질과학전공)
  • Received : 2022.10.05
  • Accepted : 2022.10.19
  • Published : 2022.10.28
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Abstract

In order to develop an air-stripping based remediation process to remove the TOC (Total Organic Carbon) in groundwater around the underground LPG storage cavern, the laboratory scale experiments at various conditions (change of air injection volume and temperature, the application of ultrasonic treatment, etc.) for two types of groundwater (initial TOC concentration of 608 mg/L and 153 mg/L, respectively). From results of experiment, as the air injection rate for stripping into groundwater increased from 2 L/min to 11 L/min and as the air-stripping time increased from 1 hour to 24 hour, the TOC removal efficiency of air-stripping increased. However, the TOC concentration of treated groundwater was higher than the discharge tolerance limit (100 mg/L) even after 24 hour stripping at the maximum air injection rate of 11 L/min. The main compounds of the TOC in groundwater were identified as methanol and propane and the long stripping time (more than 24 hour) was needed to separate the methanol from groundwater because of the affinity between water and methanol. At 20℃ and 4 L/min of air injection, the TOC removal efficiency increased to 59.1% after 24 hour air-stripping. When the temperature of groundwater increased to 30℃ and 40℃, the TOC removal efficiency increased up to 80.0% and 82.8%, suggesting that more than 24 hour air-stripping at 40℃ is needed to lower the TOC concentration to below 100 mg/L and the additional TOC removal process as well as the air-stripping is necessary. When the temperature increased to 60℃ and the ultrasonic treatment was conjugated with the air-stripping, the TOC removal efficiency increased to 87.8% within 5 hour stripping and the final TOC concentration (72.4 mg/L) was satisfied with the TOC discharge tolerance limit. The TOC removal efficiency for groundwater having low TOC concentration (153 mg/L) also showed similar removal efficiency of 89.7% (the final TOC concentration: 18.9 mg/L). Results in this study supported that the air-stripping conjugated with the ultrasonic treatment could remove successfully the TOC in groundwater around the underground LPG strorage cavern.

본 연구에서는 국내에서 운영 중인 대형 LPG(Liquefied petroleum gas: 액화석유가스) 지하공동저장소 주변 오염지하수 내 TOC(total organic carbon: 전유기탄소)를 효과적으로 제거할 수 있는 탈기법(air-stripping) 기반의 정화공정을 개발하기 위해, 국내 LPG 지하저장소 주변 두 종류의 오염 지하수 시료(초기 TOC 농도는 각각 608 mg/L와 153 mg/L)를 대상으로 TOC 제거 실내 실험을 하였다. 다양한 air-stripping 조건(공기주입량 변화, 온도 변화, 초음파 처리 연계 등)에서 처리수의 TOC 제거효율을 비교함으로써, 최적의 TOC 제거효율을 가지는 air-stripping 기반의 지하수 정화공정을 개발하고자 하였다. Air-stripping의 공기 주입량 변화 실험 결과, 공기주입량이 2 L/min에서 11 L/min로 많아질수록, stripping 시간이 1시간에서 24시간으로 길어질수록, 오염지하수의 TOC 제거율은 증가하였지만, 처리 후 지하수의 TOC 농도는 방류수 수질 기준(100 mg/L 이하)보다 높았다. 정성분석 결과 실험에 사용한 LPG 지하저장소 주변 오염지하수의 TOC 주요 성분은 메탄올과 프로판으로 나타났으며, 메탄올의 경우 물과의 친화성에 의해 air-stripping 효과가 프로판보다 낮아, 장시간의 stripping이 필요한 것으로 판단되었다. 상온(20℃)에서 공기주입량 4 L/min로 24시간 air-stripping 후 오염 지하수의 TOC 제거효율은 59.1%였으나, 온도를 30℃와 40℃로 상승시켰을 때 제거효율은 각각 80.0%와 82.8%로 증가하여, 온도 증가에 따라 TOC 제거효율도 증가하였다. 다만 오염지하수의 온도를 40℃로 유지하여도 24시간 이상 air-stripping을 해야 처리수의 TOC 농도가 방류수 수질 기준을 만족하였다. Air-stripping의 TOC 제거효율을 높이기 위해, 초음파 처리 과정을 병행한 경우, 공기주입량 9 L/min 조건으로 air-stripping을 적용한 결과 5시간 만에 87.8%의 높은 제거효율을 나타내어(처리 후 TOC 농도: 72.4 mg/L) 방류수 수질 기준(100 mg/L)을 만족하였다. 초기 TOC 농도가 낮은 오염지하수의 경우에도 초음파 처리와 air-stripping을 동일한 조건으로 병행한 경우, TOC 제거효율은 89.7%(처리 후 TOC농도: 18.9 mg/L)를 나타내었다. 연구 결과로부터 TOC로 오염된 대형 LPG 지하공동저장소 주변 지하수에 대하여 초음파 처리와 air-stripping을 연계한 정화법을 적용하는 경우, 비교적 짧은 시간(6시간 이하)에 효과적으로 지하수 내 TOC를 제거할 수 있음을 알 수 있었다.

Keywords

Acknowledgement

본 논문을 세심하게 심사하여주신 심사자들께 감사드립니다.

References

  1. Barlan, J., Trabelsi, F., Delmas, H., Wilhelm, A.M. and Detignani, J.F. (1994) Oxidative degration of phenol in aqueous media using ultrasound. Ultrasonic Sonochemistry, v.1(2), p.S97-S102. doi: 10.1016/1350-4177(94)90005-1
  2. Cha, S.S., Lee, J.Y., Lee, D.H., Amantini, E. and Lee, K.K. (2006) Engineering characterization of hydraulic properties in a pilot rock cavern for underground LNG storage. Engineering Geology, v.84(3-4), p.229-243. doi: 10.1016/j.enggeo.2006.02.001
  3. Goodall, D.C., Aberg, B. and Brekke, T.L. (1988) Fundamentals of gas containment in unlined rock caverns. Rock Mechanics and Rock Engineering, v.21, p.235-258. doi: 10.1007/BF01020278
  4. Jeon, H.S. (2000) A case study of correlation between inflows and geological structures around underground caverns. The Journal of Engineering Geology, v.10(1), p.79-93.
  5. Jeong, C.H. (2004) Relationship between hydrochemical variation of groundwater and gas tightness in the underground oil storage caverns. The Journal of Engineering Geology, v.14, p.259-272.
  6. Kim, D.K., Oh, D.H. and Jeong, C.G. (1999) LPG cavern in Inchon, Korea. The Journal of Engineering Geology, v.9, p.267-280.
  7. Kim, H.S., Yang, I.H., Oh, J.I., Her, N.G. and Jeong, S.J. (2009) A Study on the degradation properties of MTBE in solution using ultrasound. Journal of Korean Society on Water Environment, v.25(4), p.552-529.
  8. Kim, S.H., Lim, M.H. and Kim J.H. (2004) A Study on the sonolysis of chlorinated compounds. Journal of Korea Society of Waste Management, v.21(2), p.162-172.
  9. Kotronnarou, A., Mills, G. and Hoffamnn, M.R. (1991) Ultrasonic irradiation of p-nitrophenol in aqueous solution. The Journal of Physical Chemistry, v.95, p.3630-3638. doi: 10.1021/j100162a037
  10. Lee, J.U., Chon, H.T. and Chun, G.T. (1995) Study on hydrogeochemical characteristics of LPG storage cavern in the water curtain system. Proceeding of the Groundwater Environment of Korea, p.41-42.
  11. Lee, J.Y. and Cho, B.W. (2008) Submarine groundwater discharge into the coast revealed by water chemistry of man-made undersea liquified petroleum gas cavern. Journal of Hydrology, v.360, p.195-206. doi: 10.1016/j.jhydrol.2008.07.031
  12. Liang, J. and Lindblom, U. (1994) Analyses of gas storage capacity in unlined rock caverns. Rock Mechanics and Rock Engineering, v.27, p.115-134. doi: 10.1007/BF01020306
  13. Mo, S.Y., Shon, J.R., Kim, M.S., Chang, H.K. and Lee, K.J. (1999) Characteristics of sonolytic decomposition of the refractory organic compounds in the aqueous solution. Journal of Korean Society of Environmental Engineers, v.21(4), p.739-752.
  14. MOE (Ministry of Environment) (2022) Water analysis guidelines for the determination of Total Organic Carbon and Dissolved Organic Carbon. Water Environment Conservation Method.
  15. Nam, S.N., Koh, C.I. and Kan, J.W. (2000) The removal effect of hazardous chemiacl compounds by O3/ultrasound, ultrasound/UV, ultrasound/Fe2+ processes. Journal of Korea Society of Waste Management, v.17, p.705-713.
  16. NIER (National Institute of Environmental Research) (2015) Water Pollution Process Test Standard(general item): Total Organic Carbon-High Temperature Combustion Method (ES 04311.1c).
  17. Okouchi, S., Nojima O. and Arai T. (1992) Cavitation-induced degration of phenol by ultrasound. Water Science and Technology, v.26, p.2053-2056. doi: 10.2166/wst.1992.0659
  18. Sohn, J.R., Mo, S.Y. and Sohn, J.S. (1995) Treatment of nondegrable organic pollutants in aqueous by ultrasonic irradiation. Journal of Environmental Sanitary Engineers, v.10(1), p.75-84.
  19. Sohn, J.R. and Mo, S.Y. (1996) Characteristics of TCE, benzene & 2,4 dichlorophenol degradation in aqueous solution by ulrasonic irraditation. Journal of Environmental Sanitary Engineers, v.11(2), p.33-41.
  20. Sohn, J.R. and Mo, S.Y. (2002) Characteristics of sonolytic reaction of refractory aromatic compounds in aqueous solution by ultrasound. Journal of Korea Society on Water Quality, v.18(4), p.411-419.