• Surface Tension-Water Saturation Relationship as the Function of Soil Particle Size and Aquifer Depth During Groundwater Air Sparging
  • Kim, Heon-Ki;Kwon, Han-Joon;
  • Dept. of Environmental Sciences and Biotechnology, Hallym University, Institute of Energy and Environment, Hallym University;Dept. of Environmental Sciences and Biotechnology, Hallym University, Institute of Energy and Environment, Hallym University;
  • 대수층 폭기공정에서 토양입경 및 지하수 깊이에 따른 표면장력과 함수율의 상관관계
  • 김헌기;권한준;
  • 한림대학교 환경생명공학과, 한림대학교 에너지환경 연구소;한림대학교 환경생명공학과, 한림대학교 에너지환경 연구소;
Abstract
Reduction of groundwater surface tension prior to air sparging (SEAS, surfactant-enhanced air sparging) was known to increase air saturation in the aquifer under influence, possibly enhancing the removal rates of volatile contaminants. Although SEAS was known to be efficient for increasing air saturation, little information is available for different hydrogeological settings including soil particle sizes and the depth of aquifer. We investigated water saturations in the sparging influence zone during SEAS using one-dimensional column packed with sands of different particle sizes and different aquifer depths. An anionic surfactant was used to suppress the surface tension of water. Two different sands were used; the air entry pressures of the sands were measured to be $15.0\;cmH_2O$, and $36.3\;cmH_2O$, respectively. No significant difference was observed in the water saturation-surface tension relationship for sands with different particle sizes. As the surface tension decreased, the water saturation decreased to a lowest point and then it increased with further decrease in the surface tension. Both sands reached their lowest water saturations when the surface tension was set approximately at 42 dyne/cm. SEAS was conducted at three different aquifer depths; 41 cm, 81 cm, and 160 cm. Water saturation-surface tension relationship was consistent regardless of the aquifer depth. The size of sparging influence zone during SEAS, measured using two-dimensional model, was found to be similar to the changes in air saturation, measured using one-dimensional model. Considering diverse hydrogeological settings where SEAS to be applied, the results here may provide useful information for designing SEAS process.

대수층으로부터 휘발성 유기오염물질을 제거하기 위하여 air sparging을 실시하는 과정에서, 지하수의 표면장력을 인위적으로 감소시킴으로써 지하 대수층의 물 포화율을 낮추어 오염물질제거효율을 높일 수 있는 것으로 알려져 있다. 그러나 대수층의 구성 토양의 입경의 차이나 대수층의 두께의 차이가 이와 같은, 개량된 air sparging의 물 포화율 변화에 미치는 영향은 연구된 바 없다. 본 연구는 실험실 규모의 물리적인 model을 사용하여 air sparging공정 실시과정에서 서로 다른 토양입경과 깊이를 갖는 대수층 조건에서 표면장력과 물 포화율의 상관관계를 규명하였다. 표면 장력을 감소하기 위한 계면활성제로 sodium dodecylbenzene sulfonate를 사용하였고, 토양은 입경이 서로 다른 두 가지 모래를 사용하여 비교 실험을 수행하였다. 모래의 air-entry pressure는 각각 $15.0\;cmH_2O$, $36.3\;cmH_2O$로 측정되었다. 입경에 상관없이 표면장력과 물 포화율의 관계는 서로 비슷한 형태를 보였고, 표면장력이 감소함에 따라 물 포화율이 감소하다 일정 표면장력 이후에 물 포화율이 증가하는 형태로 나타났다. 본 연구에서는 표면장력이 42 dyne/cm일 때 두 가지 모래의 물 포화율이 48%로 최소치에 도달하였다. 대수층의 깊이는 41 cm, 81 cm, 160 cm의 세 가지 조건에서 실험하였으며, 본 실험조건에 해당하는 깊이 영역에서는 표면장력과 물 포화율의 상관관계가 대수층 깊이에 따른 특이한 상이점을 나타내지 않았다. 또한 2차원 모델을 이용한 실험에서 표면장력의 변화에 따른 폭기영역의 변화는 1차원 컬럼을 이용하여 측정된 물 포화율의 변화와 유사하였다. 본 연구결과는 SEAS(surfactant-enhanced air sparging)기술의 실제 적용에 있어서 다양한 현장조건에 따른 공정조건의 선정에 도움이 될 수 있을 것으로 전망된다.

Keywords: Aquifer;Remediation;Air sparging;Surfactant;SVE;SEAS;groundwater;

Keywords: 대수층;정화;지하수 폭기;계면활성제;토양증기추출법;지하수;

References
  • 1. Adams, J.A. and Reddy, K.R., 2000, Removal of dissolved- and free-phase benzene pools from ground water using in situ air sparging, J. Envir. Engrg., 126, 697-707
  •  
  • 2. Braida, W.J. and Ong, S.K., 1998, Air sparging: Air-water mass transfer coefficients, Water Resour. Res., 34, 3245-3253
  •  
  • 3. Brooks, R.H. and Corey, A.T., 1966, Properties of porous media affecting fluid flow, J. Irrig. Drain., 92, 61-68
  •  
  • 4. Burns, S.E. and Zhang, M., 2001, Effect of system parameters on the physical characteristics of bubbles produced through air sparging. Envron. Sci. Technol., 35, 204-208
  •  
  • 5. Faisal Anwar, A.H.M., Bettahar, M., and Matsubayashi, U., 2000, A method for determining air-water interfacial area in variably saturated porous media. J. Contam. Hydrol., 43, 129-146
  •  
  • 6. Johnson, R.L., Johnson, P.C., McWhorter, D.B., Hinchee, R.E., and Goodman, I., 1993, An overview of in situ air sparging, Ground Water Monit. Rev., 13, 127-135
  •  
  • 7. Johnston, C.D., Rayner, J.L., and Briegel, D., 2002, Effectiveness of in situ air sparging for removing NAPL gasoline from a sandy aquifer near Perth, Western Australia, J. Contam. Hydrol., 59, 87-111
  •  
  • 8. Kim, H. and Annable, M.D., 2006, Effect of surface reduction on VOC removal during surfactant-enhanced air sparging, J. Environ. Sci. Health Part A, 41, 2799-2811
  •  
  • 9. Kim, H., Choi, K.-M., Moon, J.-W., and Annable, M.D., 2006, Changes in air saturation and air-water interfacial area during surfacatant-enhanced air sparging in saturated sand, J. Conatam. Hydrol., 88, 23-35
  •  
  • 10. Kim, H., Soh, H.-E., Annable, M.D., and Kim, D.-J., 2004, Surfactant-enhanced air sparging in saturated sand, Environ. Sci. Technol., 38, 1170-1175
  •  
  • 11. Lundegard, P.D. and LaBrecque, D., 1995, Air sparging in a sandy aquifer (Florence, Oregon, USA): Actual and apparent radius of influence, J. Contam. Hydrol., 19, 1-27
  •  
  • 12. Marley, M.C., Hazebrouck, D.J., and Walch, M.T., 1992, The application of in situ air sparging as an innovative soils and ground water remediation technology, Gound Water Monit. Rev., 12, 137-145
  •  
  • 13. Rabiduar, A.J., Blayden, J.M., and Ganguly, C., 1999, Field performance of air-sparging system for removing TCE from groundwater, Environ. Sci. Technol., 33, 157-162
  •  
  • 14. Reddy, K.R. and Adams, J.A., 1998, System effect on benzene removal from saturated soils and groundwaterusing air sparging, J. Environ. Engrg., 124, 288-299
  •  
  • 15. Reddy, K.R., Kosgi, S., and Zhou, J., 1995, A review of in-situ air sparging for the remediation of VOC-contaminated saturated soils and groundwater, Haz. Waste and Haz. Mat., 12, 97-118
  •  
  • 16. Unger, A.J.A., Sudicky, E.A., and Forsyth, P.A., 1995, Mechanisms controlling vacuum extraction coupled with air sparging for remediation of heterogeneous formation contaminated by dense nonaquesous phase liquids, Water Resour. Res., 31, 1913-1925
  •  

This Article

  • 2009; 14(6): 65-70

    Published on Dec 31, 2009

  • Received on Oct 14, 2009
  • Revised on Oct 21, 2009
  • Accepted on Nov 30, 2009