Bench-scale optimization of bioaugmentation strategies for treatment of soils contaminated with high molecular weight polyaromatic hydrocarbons

The chemical composition of crude oil and even of refined petroleum includes hundreds of different alkanes and aromatic hydrocarbons. Among these are the polycyclic aromatic hydrocarbons (PAHs), which are known carcinogens and widespread environmental contaminants. Some compounds present in hydrocarbon-contaminated soils are rapidly removed by the activities of autochthonous bacterial populations while other PAHs, especially those with four or more fused aromatic rings, are refractory to biodegradation. The persistence of high molecular weight polyaromatic hydrocarbons (hPAHs) in soils implies either that their low solubility renders them poorly available to bacteria, or that autochthonous bacteria do not contain the metabolic or co-metabolic pathways required for their degradation or both. The rate and extent of PAH degradation in contaminated soil is not always predictable for standard biological treatment strategies. This study examines a matrix of treatments suitable for land farming in order to identify those that maximize the removal of hPAHs. The treatments include those intended to increase the bioavailability of hPAH, such as additions of biosurfactant-producing bacteria (i.e. Pseudomonas aeruginosa #64) and addition of light oils, as well as treatments intended to increase the metabolic potential of the bacterial community. The latter includes the addition of inorganic nutrients and bacterial strains capable of degrading hPAHs co-metabolically (i.e. Sphingomonas paucimobilis EPA 505). The efficacy of immobilizing PAM-degrading bacteria on vermiculite is also considered, as will be the monitoring of leachate for biodegradation of PAHs in a simulated land farming operation. (C) 1999 Elsevier Science B.V. All rights reserved.