The optimum surfactant, surfactant dose, biomass, and oxygen for different site-specific conditions. How the degradation, transport and partition parameters determined in laboratory batch experiments can be extrapolated to a flow through porous media and field conditions. Bioavailability of low-solubility hydrocarbons in soils is limited by their sorption onto the soil matrix. Surfactants above their critical micelle concentration enhance desorption of these hydrocarbons, and we know that the fraction of PAHs dissolved in the micelles can be bioavailable depending on the surfactant structure and its concentration in the aqueous phase. Biodegradation experiments are conducted in 25 ml reaction vessels, that contain in their headspace a cup in which the carbon dioxide that evolves during the biodegradation can be absorbed into a KOH solution.
Stoppers are lined with aluminum foil to minimize losses due to sorption from the headspace.
Reaction vessels are sealed and placed on a magnetic stirrer to mix the reactant continuously. At the end of the desired reaction time, concentrated sulfuric acid is introduced into the vessels to stop the reaction and to release any dissolved carbon dioxide from the aqueous solution. After an additional 6 to 8 hour period, samples from the KOH cup and reaction chamber are analyzed for radioactivity, to determine the mass of carbon dioxide produced and the loss of phenanthrene respectively. These experiments are being conducted in the presence and absence of soils, and for a series of different non-ionic surfactants and surfactantconcentrations. A model describing the micellar bioavailability as a function of the surfactant dose has been developed.