Surfactant-Enhanced Bioremediation of Soils in the Presence of an Organic Phase:
Peter R. Jaffé, Princeton University .


Goal:
Recent work has shown that low-solubility contaminants solubilized into the micellar phase of some non-ionic surfactants are directly available for biodegradation, meaning that the contaminant can be transferred directly from the core of the micelle to cell without having to transfer to the water phase first. This makes surfactant-enhanced remediation an attractive technology for sites that contain large amounts of low-solubility organic contaminants such as coal tars. Several crucial interactions need to be understood in order to extrapolate these laboratory results to field-scale surfactant enhanced bioremediation schemes. This research focuses on the following:
  1. How does the presence of surfactants affect the degradation of multicomponent substrates, and
  2. How does the presence of surfactants affect the attachment of bacteria to a NAPL interface. In the presence of contaminants such as coal tars for example,
  • Above is crucial since many PAH’s of concern will coexist, while
  • is important since much of the natural degradation may be occurring at the NAPL/water interface, which surfactants may affect in a negative manner by preventing bacteria from attaching to that interface.

Rationale:
Biodegradation of PAH’s can be monitored in batch experiments in the presence of varying surfactant doses. If the degree of partitioning of the substrate into a micelle is known from separate experiments, then simulation of these degradation experiments allows estimating the rate at which the micellar-phase substrate is being degraded. These measurements/simulations can be repeated for different surfactant doses and substrate combinations to assess the effect of both on the degradation rate.

Approach:


The following experiments have been conducted:

1. a. Biodegradation of naphthalene, phenanthrene, and pyrene as single substrate and binary and ternary   mixtures in the absence and presence of different surfactant concentrations.

2. a. Biomass accumulation on a phenanthrene surface as a function of varying surfactant concentrations and for bacteria with different degrees of hydrophobicity.

2. b. Biomass accumulation in column studies with beads coated with phenanthrene as a function of varying surfactant concentrations and for bacteria with different degrees of hydrophobicity.

Status:
The multicomponent PAH degradation in the presence of surfactants has been completed during the first year of this project. A set of experiments to study the effect of surfactants on the attachment of bacteria to NAPL surfaces in batch and column experiments is being completed during the second year of the project.

Technology
Transfer
and
Outreach
Plan:

Results of this research were transferred to users using three different approaches: (1) publications in journals that have a wide circulation amongst practitioners and scientists; (2) presentations in conferences, and (3) presentations to selected industrial groups from the chemical and petrochemical manufacturing sector, e.g., meetings with representatives from the environmental divisions at Shell, Exxon, Phillips Petroleum, and DuPont.