The Cl and DOC concentrations in leachate from a leaky landfill were determined
ID: 106580 • Letter: T
Question
The Cl and DOC concentrations in leachate from a leaky landfill were determined to be 1000 ppm and 25 ppm, respectively. A series of wells were installed down gradient from the landfill (see map below). Results of chemical analyses from these wells for Cl and DOC are listed in the table. Using this data, Map the plume of contaminated groundwater down gradient of the landfill. Estimate Cl and DOC concentrations in "clean'' groundwater. Calculate the fraction "leachate" at Well 103, 106, 109, and 111. Determine if DOC is being degraded in the aquifer. Estimate the Cl and DOC concentration in Well A and Well B.Explanation / Answer
I.The plume of contaminated ground water gradient lies under the landfill area because when there is some leakage from the landfill,it gets deposited in an area below the landfill and hence groundwater deposition takes place.
II.The Cl and DOC concentration in clean ground water can be calculated by taking any one of the wells into account.
The well immediately beneath the landfill area is 114. The Cl and DOC concentration in that well can be estimated to be present in the clean groundwater.
Cl concentration in 114=230ppm
DOC concentration in 114=2.1ppm
Considering the leakages,Cl concentration=220(assumption)
DOC concentration=2(assumption)
III.Fraction of leachate at well 103=750/1000=0.75ppm in Cl and 15.9/25=0.636ppm in DOC
Fraction of leachate at well 106=330/1000=0.33ppm in Cl and 2.2/25=0.088ppm in DOC
Fraction of leachate at well 109=130/1000=0.13ppm in Cl and 0.8/25=0.032ppm in DOC
Fraction of leachate at well 111=40/1000=0.40ppm in Cl and 1.0/25=0.04ppm in DOC
IV.If DOC is being degraded in the acquifer then the intial amount would somewhat be decreased from 25ppm to approximately 20ppm.
V.Well A-The concentration can be acquired from well 109.
Cl=120ppm approximately with leakage
DOC=0.5ppm approximately with leakage
Well B-The concentration can be acquired from well 102.
Cl=30ppm approximately with leakage
DOC=0.1ppm approximately with leakage.