Surfactant desorption is key to successful PAH bioremediation

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Courtesy of Ivey International Inc.

Formulations which are patented non-ionic surfactant mixtures used in the in situ and ex situ treatment of petroleum hydrocarbons, chlorinated solvents, heavy metals, and more recently PAHs, PCBs and MTBE type contaminated waste are involved in Surfactant Enhanced Bioremediation (SEB®) using Iveysol ®. These surfactant formulations have the ability to enhance soil biodegradation.

During in situand ex situ bioremediation, the effectiveness of the bioremediation process is a function of balancing several physical and chemical parameters to achieve effective bio-mineralization of the target contaminants. The addition of Ivey-sol to the substrate can aid in the controlled desorption of the contaminants making them more bio-available. As a result, the duration of hydrophobic organic chemicals (HOC) bioremediation can be reduced by as much as 30 to 60%, or more.

Normally hydrophobic organic chemicals exhibit limited bioavailability to microorganisms as the contaminants tend to partition onto the soil matrix. This partitioning can account for as much as 95% or more of the total contaminant mass. Thus this limits the concentration of HOC available to the microbial population. Hence certain HOCs such a polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCBs) and phtalates can persist in the soil matrix for long periods of time.

The use of Ivey-sol surfactant formulations, as part of a well designed bioremediation process, will provide a mechanism to desorb and mobilize the target contaminants from the surface of soil and bed rock to make them more available to the indigenous or introduced microbial populations.

Bioavailability is governed by the substrate concentration that the cell membrane comes in contact with (i.e., what the microorganisms ‘see’) as well as the rate of mass transfer from potentially bioavailable (e.g., non-aqueous HOCs) phase to the directly bioavailable bioavailable (e.g., surfactant-aqueous HOC) phase. Surfactant Enhanced Bioremediation affects the sorption of HOC and surfactants at the solid-liquid interface (i.e., the surface–H2O–NAPL interface). This mechanism is in part responsible for the increased bioavailability of the HOC and surface-bound nutrients. SEB using Ivey-sol is effective at low surfactant concentrations. It expedites bioremediation of the contaminated soil and positively affects the surfactant–soil–NAPL systems (e.g., mass transfer of HOCs, cell hydrophobicity, and cell attachment at interfaces) while averting the inhibiting and/or microbial toxic effects associated with some surfactants (i.e., catonic and anionic) which are only effective at much higher concentrations.

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