PNNL

Abstract

This paper describes results from intermediate-scale, two-dimensional testing of foam injection into sedimentary materials collected from the U.S. Department of Energy (DOE) Hanford Site. The testing was performed to evaluate the effects of delivery pressure, injection rate, foam stability, foam quality, and formation heterogeneities on the migration of foam, water, remediation amendment, and contaminants within a sedimentary volume. Testing was accomplished in a test bed that is configured in the form of two thin rectangular boxes. Each of the boxes holds approximately 135 liters (255 kilograms) of sediment. Foam was injected into each box through a segment of polyvinyl chloride slotted well casing, and air was extracted from the boxes through a similar system. Four sets of tests were conducted. During Test 1, both of the boxes were loaded in a homogeneous manner, while in Tests 2, 3, and 4, both of the boxes were loaded so as to contain two rectangular zones of heterogeneity. In addition, a zone of the sediment contained in the test bed used for Test 4 was augmented with uranium-rich calcite to produce a known concentration of uranium. The injection rate varied between the boxes during the Test 1 but was the same for each box during the final three tests. The foam generation formula for Tests 1 and 2 consisted of an aqueous solution of anionic surfactant. The foam generation formula used in Test 3 consisted of an aqueous solution of anionic surfactant and contained 25,000 milligrams per liter (mg/L) of phosphate in the form of a 9:1 mixture of sodium phosphate and sodium tripolyphosphate. The foam generating formula used in Test 4 consisted of an aqueous solution of an anionic surfactant and a nonionic surfactant and also contained 5,000 mg/L of phosphate as the aforementioned mixture. Subsequent to each of the four tests, the test beds were disassembled, and samples of the sediments were taken and analyzed for a number of parameters, depending on the specific test. This paper presents the results of the intermediate-scale testing.