Impact of bulking agents, forced aeration, and tillage on remediation of oil-contaminated soil
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Bioremediation is a relatively new technology used to remediate contaminated soil that involves oil degrading microorganisms. Adequate aeration is essential for oil degrading microorganisms to be active. Methods of promoting aeration are tillage, pumping air into the soil, and adding bulking agents to increase porosity. More knowledge is needed regarding the interaction between bulking agents and other technologies in enhancing aeration for bioremediation of oil-contaminated soil. An experiment was undertaken using oil-contaminated soil from an oil production site in east Texas to evaluate different methods to promote aeration. Each treatment contained 10% total petroleum hydrocarbons (TPH) on a dry weight basis. Treatments were bulking agents (non-bulked control, chopped bermudagrass hay, sawdust, and vermiculite) and aeration (static, tillage, and forced aeration). Treatments were arranged in a 4 x 3 factorial with three replications in a completely randomized design. Sawdust and vermiculite were added at equal volumes with the contaminated soil and chopped bermudagrass hay at a ratio of 1 volume of hay to 2 volumes of contaminated soil. Experimental units were 1001 barrels open at the top. The TPH content was determined every 6 weeks during a 30 week period. During this time the TPH content decreased in all treatments. Bulked soils showed a more rapid reduction in TPH compared to the non-bulked control. Tilling increased the rate and extent of remediation more than soil receiving forced aeration or left static. The most rapid rate of remediation occurred during the first 12 weeks from the tilled-hay treatment, where the TPH decreased 82%. The slowest remediation rate occurred in the non-bulked-static treatment where the TPH content decreased 33% in 12 weeks. By week 30 the TPH content of the treatments ranged from 90% degraded in the tilled-hay and tilled-vermiculite treatments to 77% degraded for the non-bulked-static treatment. Tillage and adding bulking agents enhanced remediation of oil-contaminated soil.
