|M.Sc Student||Bar Uri|
|Subject||Reclamation of Fractured Aquifers Contaminated by Non-|
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Hillel Rubin|
This study concerns the characteristics of pump-and-treat reclamation of an aquifer whose top layers are contaminated with entrapped NAPL. The aquifer is composed of a fractured permeable formation. The NAPL entrapment could be attributed to fluctuations of groundwater table and/or raising the groundwater table, where floating lens of the light NAPL (LNAPL) had taken place on top of the groundwater table. It is assumed that most of the residual NAPL is entrapped within the porous blocks of the formation. The study incorporates a parametric analysis of all physical quantities that might affect the aquifer remediation process. Reference is made with regard to a wide range of residual NAPL saturations. In cases of extremely low residual NAPL saturation the entrapped NAPL has negligible effect on the permeability of the formation blocks. On the other hand at higher NAPL saturation according to some models very significant effects of the entrapped NAPL on the block’s permeability are expected. Generally, NAPL dissolution might lead to significant local variations in the preferential flow pattern (division of the total flow between the fracture segments and the porous blocks) in the fractured formation. However, we referred to a comparatively thick aquifer, whose total discharge is practically unaffected by the entrapped NAPL, but the permeable block flow diminishes in blocks contaminated by entrapped NAPL. Two major dimensionless parameters control the processes of aquifer remediation : (1) The dimensionless interphase mass transfer coefficient, and (2) The mobility number, which represents the ratio between the permeable block and fracture flow rates. Besides these parameters, NAPL dissolution and solute transport are significantly affected by the type of relationships between the entrapped NAPL saturation and the permeability of the particular porous blocks. Local values of the interphase mass transfer coefficient and mobility number are subject to changes during the NAPL dissolution process. The study provides information about characteristics of pump-and-treat reclamation of the aquifer and indicates that the reduced block permeability may significantly reduce the efficiency of the reclamation process. In cases of top layers contaminated with entrapped NAPL often very moderate pumping is possibly associated with minor contamination of the pumped water with dissolved solutes. Intensification of the groundwater pumping may increase the pumped water contamination and also lead to penetration of dissolved solutes into deep layers of the aquifer. Characteristics and quantification of these phenomena are given in this paper.