M12 PM Remediation
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 345-346

(AAA-1117-660715) Enhanced microbial consortium production for creosote-contaminated soil bioaugmentation using humic acids to increase PAH bioavailability.

D'Amours, D¹, Samson, R¹, Deschênes, L¹, ¹ Industrial Chair in Site Remediation and Management, École Polytechnique de Montréal, Chemical Engineering Department, Montreal, Quebec, Canada

ABSTRACT- The widespread contamination of soil by creosote in industrialized countries has created the need for reliable, cost-effective and sustainable bioremediation processes. Polycyclic aromatic hydrocarbons (PAHs) in creosote are of particular concern because they represent up to 85% of its weight composition and many are carcinogenic and degrade poorly. Soil activation, a method based on the cultivation of an indigenous microbial consortium from a fraction of a contaminated soil for subsequence use as an inoculum for bioaugmentation of the same soil, was studied as a method for the bioremediation of creosote-contaminated soils. Since the bioavailability of PAHs is low due to their high hydrophobicity, humic acids were added during soil activation in soil slurry bioreactors to increase it. The effect of this organic material on the microbial consortium performance was investigated. Soil activation was performed in 8 L stainless steel soil slurry bioreactors operated in fed-batch mode with periodic creosote addition in increasing quantity. Half of the bioreactors were supplemented with humic acids. During the 75-day activation period, PAH concentration, pH, temperature and oxygen consumption were monitored. Microbial community performance was evaluated using phenanthrene, anthracene and pyrene mineralization tests, direct counts using Live/Dead® BacLight™ method and PAH-specific microbial population counts using the spread plate method. During soil activation, the effective concentration of PAHs in the aqueous phase was increased by a factor of 1.2 to 25 in presence of humic acids. Humic acids also increased PAH degradation and mineralization rates and reduced the latency phase resulting in an enhanced microbial consortium performance. The presence of higher concentration of PAH-degraders and an enhanced microbial tolerance to increasing creosote concentration were also attributed to the addition of humic acids. These results indicate that the use of humic acids during creosote-contaminated soil activation efficiently enhances microbial consortium performance.

Key words: Bioavailability, Creosote, Bioaugmentation, Humic acids