Results of Laboratory Treatability Tests
Batch test results indicate that there is sufficient reducible iron in the aquifer sediments to change the geochemical environment from oxidizing to reducing when the concentration of sodium dithionite in the injected fluid is 17.41 grams/liter of solution. Analysis of the sediment samples reveals that the chromium is transformed from Cr (VI) to Cr(III) and is precipitated on the aquifer sediment surfaces.
Column tests and computer modeling indicate that the sodium dithionite solution will affect the aquifer within 20 feet of the injection well as a conservative estimate.
Batch and column tests were conducted to determine the design parameters for the permeable reactive barrier and the injection well spacings for the in situ redox manipulation method using sediment and groundwater samples from the site. The results indicate that granular iron is effective in removing the chromium from the contaminated ground water. Column tests indicate that a mixture of granular iron and the aquifer material will reduce to chromium concentration in solution to below detection levels in 0.78 hours after the ground water traveled through the column a distance of approximately 0.15 feet.