Oil Spill Bioremediation Research

Importance of Problem

Oil releases threaten public health and safety by contaminating drinking water, causing fire and explosion hazards, diminishing air and water quality, compromising agriculture, destroying recreational areas, wasting nonrenewable resources, and costing the economy millions of dollars. Examples of the severe implications to humans alone from oil spills include the following studies from a 1996 Science Advisory Board report: (1) an API study in 1994 reported 85% of refineries have confirmed groundwater contamination and 17 aboveground storage sites (AST) have oil plumes greater than 1 million gallons, and (2) in 1988, a 1 million gallon diesel oil release from an Ashland Oil Facility AST shut down 15 municipal drinking water intakes, disrupting water supply for 2.7 million residents. Oil spills harm the environment by killing fish, birds, wildlife, and biota, destroying habitat and food, and producing toxic effects in organisms and ecosystems. If left alone, often the effects can persist for years and even decades. Oil industry infrastructure is aging, thus continuing to seriously threaten the environment for years to come The health, environmental, and economic effects of oil spills are well documented and substantial. Bioremediation offers a potentially low cost alternative to cleanup of environmentally devastated spill sites. We know how effective bioremediation can be; the question now is how do we optimize its performance to meet cleanup targets?

Accomplishments

The oil spill research program has been active since the passage of the Oil Pollution Act of 1990 (OPA-90). Since that time, significant advances have been made. Most notable have been the development and promulgation of a screening protocol for confirming the effectiveness of marine oil spill bioremediation agents¹ and the statistical proof from the Delaware field study that bioremediation enhances the disappearance rate of crude oil hydrocarbons in the field despite an already high background rate.^2,3 An outgrowth of that study was the characterization of microbial community changes that occurred during the course of the bioremediation effort.⁴ The most striking change was the shift from primarily Gram(+) bacteria and eukaryotes at the beginning to predominantly Gram(-) bacteria after about 8 weeks and continuing on to the end. Other important findings from the program have been the development of a new method of estimating separately the populations of bacteria able to break down alkanes and aromatics in crude oil,^5,6 the quantification of the minimum nitrogen concentration needed on marine beaches for maximum growth rate on hydrocarbons,⁷ the definition of the frequency of application of water-soluble nutrients needed to maintain the target nitrogen concentration,^8,9 the discovery that asphaltenes inhibit the breakdown of the biodegradable constituents in crude oil,¹⁰ and the development of new mathematical models that help explain the nutrient transport dynamics on marine beaches.^11-14 The foregoing advances have been major achievements, but substantially more knowledge is needed in a greater variety of environments before program funds are allowed to wane.

Statement of Science Questions Needed to be Addressed

A number of questions still remain unanswered. Examples include:

how do we determine the effectiveness of chemical and biological countermeasures for oil spill cleanup in marine and freshwater environments?
under what conditions is bioremediation appropriate for cleaning up an oil spill?
how do we optimize bioremediation from an engineering standpoint to make it a cost effective cleanup technology?
how do we determine the utility of bioremediation as a cleanup technology for low oxygen tension environments, such as wetlands and salt marshes?
what are the environmental consequences of spills of non petroleum-based oils, what are their breakdown products, and what is their persistence?

Description of Research Activities

To answer the above questions, the Oil Spill Bioremediation Research Program has designed studies to address these important needs. Objectives of the planned or on-going research activities are described below:

To develop a protocol for testing the effectiveness of oil spill bioremediation agents in freshwater environments (the existing protocol is for saltwater environments) and to complete the standardization of the inoculum in the current marine protocol. These activities are nearing completion and a revised protocol will be submitted for approval in Headquarters during FY 2000.
To develop, finalize, and publish a protocol that tests the effectiveness of chemical products that disperse spilled hydrocarbons into the water column. A new protocol has been developed that will replace the current Swirling Flask Test, and round robin testing is planned for early in FY 2000.
To evaluate the effectiveness of bioremediation and phytoremediation for cleaning up and restoring inland wetlands and coastal salt marshes contaminated with crude or refined oil.
To study the effect of permeability on penetration and retention of nutrients in soil and sediment.
To determine the maximum oil concentration amenable to bioremediation.
To understand the mechanisms that control the transport of crude and refined oil constituents from the oil phase to the oil-water interface where they are biodegraded by microorganisms residing in the aqueous phase.
To determine the breakdown products of non petroleum-based oils (vegetable oils and animal fats), evaluate their persistence in the environment, and define emulsification factors that influence the volume increase of such oils when they are spilled in the environment.
To develop an innovative method of cleaning up a non petroleum oil spill on water by exploiting the anaerobic biodegradability of such oils in sediments.
To define the physical properties of Orimulsion in freshwater solutions.
To develop and publish a guidance document on the bioremediation of marine and freshwater shorelines by December 2000 for use by spill responders.

Publications

Venosa, A.D., J.R. Haines, W. Nisamaneepong, R. Govind, S. Pradhan, and B. Siddique. 1992. "Efficacy of commercial products in enhancing oil biodegradation in closed laboratory reactors." J. Ind. Microbiol. 10: 13-23.

Venosa, A.D., M.T. Suidan, B.A. Wrenn, K.L. Strohmeier, J.R. Haines, B.L. Eberhart, D. King, and E. Holder. 1996. "Bioremediation of an experimental oil spill on the shoreline of Delaware Bay." Environmental Sci. and Technol. 30(5): 1764-1775.

Venosa, A.D., M.T. Suidan, D. King, and B.A. Wrenn. 1997. "Use of hopane as a conservative biomarker for monitoring the bioremediation effectiveness of crude oil contaminating a sandy beach." J. Ind. Microbiol. & Biotechnol. 18: 131-139.

Macnaughton, S.J., J.R. Stephen, A.D. Venosa, G.A. Davis, Y-J. Chang, and D.C. White. 1999. "Microbial population changes during bioremediation of an experimental oil spill." Appl. Environmental Microbiol. 65(8): 3566-3574.

Haines, J.R., B.A. Wrenn, E.L. Holder, K.L. Strohmeier, R.T. Herrington, and A.D. Venosa. 1996. "Measurement of hydrocarbon-degrading microbial populations by a 96-well plate most-probable-number procedure." J. Ind. Microbiol. 16: 36-41.

Wrenn, B.A. and A.D. Venosa. 1996. "Selective enumeration of aromatic and aliphatic hydrocarbon-degrading bacteria by a most-probable number procedure." Canad. J. Microbiol. 42: 252-258.

Du, X., P. Reeser, M.T. Suidan, T. Huang, M. Moteleb, M. Boufadel, and A.D. Venosa. 1999. "Optimum nitrogen concentration supporting maximum crude oil biodegradation." In: Proc. International Oil Spill Conference, Seattle, WA, American Petroleum Institute, Washington, DC.

Wrenn, B.A., M.T. Suidan, K.L. Strohmeier, B.L. Eberhart, G.J. Wilson, and A.D. Venosa. 1997. "Nutrient transport during bioremediation of contaminated beaches: evaluation with lithium as a conservative tracer." Wat. Research 31(3): 515-524.

Wrenn, B.A., M.T. Suidan, K.L. Strohmeier, B.L. Eberhart, G.J. Wilson, A.D. Venosa, J.R. Haines, and E.L. Holder. 1998. "Influence of tide and waves on washout of dissolved nutrients from the bioremediation zone of a coarse-sand beach: application in oil-spill bioremediation." Spill Sci. & Technol. Bulletin 4(2): 99-106.

Uraizee, F.A., A.D. Venosa, and M.T. Suidan. 1998. "A model for diffusion controlled bioavailability of crude oil components." Biodegradation 8: 287-296.

Boufadel, M.C., M.T. Suidan, A.D. Venosa, C.H. Rauch, and P. Biswas. 1998. "2D variably saturated flows: physical scaling and bayesian estimation." J. Hydrol. Engineering 3(4): 223-231.

Boufadel, M.C., M.T. Suidan, and A.D. Venosa. 1997. "Density-dependent flow in one-dimensional variably-saturated media." J. Hydrol. 202: 280-310.

Boufadel, M.C., M.T. Suidan, and A.D. Venosa. 1999. "Numerical modeling of water flow below dry salt lakes: effect of capillarity and viscosity." J. Hydrol. 221: 55-74.

Boufadel, M.C., M.T. Suidan, and A.D. Venosa. 1999. "A numerical model for density- and viscosity-dependent flows in two-dimensional variably saturated porous media." J. Contaminant Hydrol. 37: 1-20.

For information, contact Albert D. Venosa, Ph.D. at venosa.albert@ epa.gov