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LAND TREATMENT OF TWO PLATEAU MATERIALS CONTAMINATED WITH PAHS
Citation:
Acheson*, C M., G D. Sayles*, R F. Herrmann*, T Richardson*, T Dahling*, Y. Shan, D. A. Balz, AND M. J. Kupferei. LAND TREATMENT OF TWO PLATEAU MATERIALS CONTAMINATED WITH PAHS. Orlando, FL, 6/2-5/03.
Description:
This study was designed to evaluate several treatments for their ability to enhance the biological removal of polycyclic aromatic hydrocarbons (PAHs) from contaminated soil and sediment. Previously land-treated material was used to test the treatments in a 13 week bench scale study.
Prior to this study, pilot scale land treatment had been conducted on two matrices: soil from a former manufactured gas plant, Calhoun Park Superfund Site, Charleston, SC; and sediment from the East River, near New York, NY. Pilot scale land treatment significantly reduced the PAH contamination on both materials, but a treatment plateau was reached after which longer land treatment did not remove additional PAHs. The residual or plateau concentrations were 1800 and 270 mg/kg dry solid respectively, 39% of the original contamination for both matrices.
In an effort to reduce residual PAH concentrations, several treatments were evaluated in a completely randomized design with a factorial treatment structure (2 x 2 x 9), two matrices by two matrix preparations by 9 amendments. The two matrices were Calhoun Park soil and East River sediment. To enhance microbial bioavailability, half of the soil and sediment was prepared by grinding to a fine consistency; the other half was not manipulated. The amendments tested in this study were: (1) no amendments; (2) surfactant flooding designed to redistribute PAHs in the soil and enhance PAH mobility; (3) surfactant flooding plus solid oxygen addition; (4) water flooding; (5) water flooding plus solid oxygen addition; (6) Fenton's reagent addition to chemically oxidize the PAHs followed by bioremediation; (7) Fenton's reagent addition plus solid oxygen addition; (8) compost tea addition to inexpensively feed the microbial community; and (9) compost tea addition plus solid oxygen addition. A solid oxygen source (CaO2) was added to stimulate aerobic degradation during the flooded conditions. Killed controls were also included.
Throughout the course of the study, moisture content and pH were measured and adjusted. Dissolved oxygen was measured when reactors were flooded. The concentration of 19 PAHs, phospholipid fatty acid concentrations (PLFA), and solid phase Microtox toxicity were measured throughout the experiment. Initial and final samples were tested for plant toxicity (lettuce and oat seed germination and root elongation). Chemical data were corrected for dilution by amendment addition. Chemical and toxicity data were statistically analyzed using Analysis of Variance techniques. The chemical results show virtually no change in PAH concentrations in any of the treatments. The toxicity data show significant increases in Fenton's treated reactors. These results demonstrate that: residual contamination is recalcitrant to bioremediation; other treatments are needed to manipulate the plateaus; and toxicity assays assist in evaluating treatment performance.