AbstractIn situ biodegradation ofp‐xylene was studied in a 7‐cm (2.75‐in.) soil column using oxygen microbubbles to supply the electron acceptor.Pseudomonas putidacontinuously degradedp‐xylene below detectable limits until the oxygen supply was exhausted. Retention time in the biodegradation zone was approximately 45 min. Vent losses claimed 5–10% of the injected oxygen, with 71–82 % being utilized. The pressure drops resulting from increased biomass showed a slight increase over the first few days followed by a gradual decline, indicating that the biomass will not plug the soil matrix under the conditions of this test. The addition of ferrous iron in the feed and its subsequent oxidation to ferric hydroxide did not affect biodegradation, nor did it cause appreciable soil plugging. In order to precipitate the ferrous iron before it reached the microbubbles, an air‐sparging section was added. This resulted in volatilization ofp‐xylene with very little ferrous oxidation until the groundwater reached the oxyg
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