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Two‐Stage Aquifer Pumping Subject to Slow Desorption and Persistent Sources
Author(s) -
Saez Jose A.,
Harmon Thomas C.
Publication year - 2005
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2005.00128.x
Subject(s) - aquifer , environmental remediation , plume , desorption , stage (stratigraphy) , environmental science , homogeneous , petroleum engineering , volumetric flow rate , groundwater , volume (thermodynamics) , environmental engineering , mechanics , soil science , contamination , chemistry , geotechnical engineering , geology , physics , thermodynamics , adsorption , ecology , paleontology , organic chemistry , biology
This work focuses on improving pump‐and‐treat remediation by optimizing a two‐stage operational scheme to reduce volumes extracted when confronted with nonequilibrium desorption, low‐permeability units, and continuous contaminant sources such as non–aqueous phase liquids (NAPL). Q 1 and Q 2 are the initial short‐term high pumping rate and later long‐term low pumping rate, respectively. A two‐dimensional ground water flow and transport management model was used to test the proposed strategy for plumes developed from finite (NAPL‐free) and continuous (NAPL‐driven) contaminant sources in homogeneous and nonhomogeneous (zoned) aquifers. Remediation scenarios were simulated over durations of 2000, 6000, and 15,000 d to determine (1) the optimal time to switch from a preset Q 1 to Q 2 and (2) the value of Q 2 . The problem was constrained by mass removal requirements, maximum allowable downgradient concentrations, and practical bounds on Q 2 . Q 1 was fixed at preset values 50% to 200% higher than the single‐stage pumping rates (i.e., steady pumping rates during entire remediation period) necessary to achieve a desired cleanup level and capture the plume. Results for the NAPL‐free homogeneous case under nonequilibrium desorption conditions achieved the same level of cleanup as single‐stage pumping, while reducing extracted volumes by up to 36%. Comparable savings were obtained with NAPL‐driven sources only when the source concentration was reduced by at least 2 orders of magnitude. For the zoned aquifer, the proposed strategy provided volume savings of up to 24% under NAPL‐free and reduced source conditions.