A Study on the Full-scale Soil Washing Process Improved by Multi-stage Continuous Desorption and Agitational Desorption Techniques to Remediate Petroleum-contaminated Soils

In accompany with the transfer of US army bases, recent surveys reported serious contamination of soils by the release of petroleum from storage facilities and heavy metals accumulated in rifle-ranges. These problems have made an increased concerns of cleanup technology for contaminated soils. In this study, a full-scale soil washing process improved by multistage continuous desorption and agitational desorption techniques was examined for petroleum-contaminated soils obtained from three different remedial sites that contained 29.3, 16.6, and 7.8% of silt and clay, respectively. The initial concentrations of total petroleum hydrocarbon (TPH) were 5,183, 2,560, and 4,860 mg/kg for each soil. Pure water was applied to operate washing process, in which water used for washing process was recycled 100% for over 6 months. The results of full-scale washing tests showed that the TPH concentrations for soils (> 3.0 mm) were 50${\sim}$356 mg/kg (85.2${\sim}$98.2% removal rates), regardless of the contents of silt and clay from in A, B and C soil, when the soils were washed at 3.0 kg/$cm^2$ of injection pressure with the method of wet particle separation. Based on the initial TPH concentration, the TPH removal rates for each site were 85.2, 98.2 and 89.9%. For soils in the range of 3.0${\sim}$0.075 mm, the application of first-stage desorption technique as a physical method resulted 834, 1,110, and 1,460 mg/kg of TPH concentrations for each soil, also additional multi-stage continuous desorption reduced the TPH concentration to 330, 385, and 245 mg/kg that were equivalent to 92.4, 90.6, and 90.1% removal rates, respectively. The result of multi-stage continuous desorption for fine soil (0.075${\sim}$0.053 mm) were 791, 885, and 1,560 mg/kg, and additional agitation desorption showed 428, 440, and, 358 mg/kg of TPH concentrations. Compared with initial concentration, the removal rates were 92.0, 93.9 and 92.9%, respectively. These results implied we could apply strategic process of soil washing for varies types of contaminated soils to meet the regulatory limit of TPH.

현장규모의 유류오염토양 세척공법에 다단연속탈착 및 교반탈착기법을 이용한 세척공정 성능향상에 관한 연구

최근 주한미군기지 이전에 따른 토양오염도 조사결과, 유류저장시설에서의 누출 및 사격장내 중금속에 의한 오염이 심각한 것으로 보고되었으며 오염토양 정화에 대한 관심이 증대되고 있다. 다단연속탈착기법과 교반탈착기법을 적용한 현장규모의 유류오염토양 세척공정 성능향상에 관한 연구를 위해서 각각 다른 세지역의 정화대상부지 오염토양 중 미세토사가 29.3, 16.6, 7.8% 함유된 토양을 사용하였으며, 초기 오염농도는 각각 5,183, 2,560, 4,860 mg/kg이였다. 세척실험에 사용한 세척제로는 물을 이용하였으며 세척수를 6개월 이상 100% 재활용하여 세척공정을 운영하였다. 현장규모 세척 실험 결과 각기 다른지역의 오염토양 중 3.0 mm 이상의 오염토양은 세척수 분사압력 3.0 kg/$cm^2$의 고압분사를 통한 습식분리 후 TPH 농도는 280, 50, 356 mg/kg으로 초기농도 대비 각각 85.2, 98.2, 89.9%의 TPH 제거율을 보였다. 3.0${\sim}$0.075 mm의 모래입경에 대하여 1차 물리적 탈착 후 TPH 농도 [초기 입경별 오염부하량 대비]는 834, 1,110, 1,460 mg/kg 이었으며, 추가적인 세척공정의 2차 연속 물리적 탈착인 다단연속탈착기법을 통한 TPH 농도는 각각 330, 385, 245 mg/kg으로 초기농도 대비 각각 92.4, 90.6, 90.1%의 세척효율을 보였다. 미세모래 입경(0.075${\sim}$0.053 mm)에 대한 다단연속세척 후 TPH 농도는 791, 885, 1,560 mg/kg으로 나타났으며, 추가적인 교반 탈착 후 TPH 농도는 각각 428, 440, 358 mg/kg으로 초기농도 대비 92.0, 93.9, 92.9%의 제거율을 보였다. 이와 같은 결과를 바탕으로, 토양세척기법은 TPH 법적기준을 맞출 수 있는 전략적 복합공정을 통해 다양한 오염토양에 폭넓게 적용할 수 있을 것으로 판단된다.