System Effects on Remediation of VOC-Contaminated Saturated Soils and Groundwater Using In-Situ Air Sparging

地下水污染影响了我国很大一部分的供水。原位空气雾化已被证明是修复被挥发性有机化合物（VOCs）污染的饱和土壤和地下水的一种高效且经济的方法，挥发性有机化合物包括轻非水相液体（LNAPLs）如苯以及致密非水相液体（DNAPLs）如三氯乙烯。目前现场空气喷射系统的设计是经验性的，完全基于试验和过去的经验。因此，目前现场系统的实施通常需要在修复程序中对设计进行大量修改，以提高空气喷射性能，从而导致更多的时间和金钱支出。本研究将通过以下方式为空气喷射现场操作提供合理的设计基础：1)进行受控的、理想化的实验室实验，研究空气喷射过程中发生的气流模式和由此产生的传质/传输过程；2)建立一个全面的数学模型，准确地包含主要的污染物传质/传输机制，并使用实验室测试结果对其进行验证；3)组装和评估在不同地质和污染条件下在现场实施的空气喷射系统的性能；4)使用大量的现场空气喷射数据来验证数值模型。实验室实验将有以下具体目标：1)研究土壤地层和地下水流量对空气喷射性能的影响；2)评价挥发性有机化合物（VOC）的类型、形式和位置（包括LNAPL和DNAPL池）对空气喷射去除效率的影响；3)通过实验室修复实际现场土壤来验证实验室研究，4)将实验室模拟结果与现场性能数据进行比较，并开发概念空气喷射模型。由此产生的概念模型可用于开发或验证数学模型，以便将来在合理的基础上设计现场系统。由于在许多污染场地，空气喷射是一种可行的补救选择，因此这项研究将提供的设计过程的优化将带来巨大的经济效益。

Groundwater contamination impacts a significant portion of our nation's water supply. In-situ air sparging has proven to be both an efficient and a cost-effective method for remediating saturated soils and groundwater contaminated with volatile organic compounds (VOCs), including light nonaqueous phase liquids (LNAPLs) such as benzene as well as dense nonaqueous phase liquids (DNAPLs) such as trichloroethylene. The current design of field air sparging systems is empirical, based solely on pilot tests and past experience. As a result, the present implementation of field systems often requires extensive modification in design during the remediation program in order to improve air sparging performance - leading to larger expenditures of time and money. This research will develop a rational design basis for air sparging field operations by: 1) conducting controlled, idealized laboratory experiments to investigate air flow patterns and the resulting mass transfer/transport processes that occur during air sparging; 2) developing a comprehensive mathematical model that accurately incorporates the major contaminant mass transfer/transport mechanisms and validating it using the results f the laboratory testing; 3) assembling and assessing the performance of air sparging systems implemented in the field under different geologic and contaminant conditions, and 4) using the extensive field air sparging data to validate the numerical model. The laboratory experiments will have the following specific objectives: 1) investigate the effects of soil stratigraphy and groundwater flow on air sparging performance; 2) evaluate the effects of VOC type, form, and location, including LNAPL and DNAPL pools on air sparging removal efficiency; 3) verification of laboratory studies through the laboratory remediation of actual field soils, and 4) perform a comparison on laboratory simulation results with field performance data and develop a conceptual air sparging model. The resulting conceptual model can be used to develop or validate mathematical models, permitting field systems to be designed on a rational basis in the future. Because air sparging is a viable remedial option at so many contaminated sites, an optimization of the design process that this research will provide will offer enormous financial benefits.