Bioremediation of Exxon Valdez Oil Spill

[EPA press release - July 31, 1989]

Based upon results of EPA's research program, the Exxon Corp. will soon begin bioremediation applications on 5800 yards of shoreline on Green and Seal Islands in Prince William Sound, Alaska. Exxon's proposal has been approved by the Regional Response Team, chaired by the U.S. Coast Guard.

EPA informed Exxon on July 26 that it would support a proposal by the company to use bioremediation to aid in cleaning up the oil spilled from the Exxon Valdez in Prince William Sound.

In a letter to Exxon, EPA provided information that would support the use of bioremediation as a cleanup technique for the Valdez oil spill. EPA's recommendations are based on the preliminary results of a small-scale feasibility test the agency began in June using indigenous microorganisms to degrade spilled oil on the Sound shoreline.

The bioremediation technique being used in the test involves adding fertilizers to enhance the growth of bacteria naturally present in the environment. These bacteria naturally degrade certain of the toxic hydrocarbons in oil. Bacterial growth can be increased by applying fertilizers, which increase the availability of nitrogen and phosphorus, the nutrients bacteria need to utilize hydrocarbons as a food source. EPA is recommending both fast- and slow-release fertilizers to optimize cleanup.

Attached is a copy of EPA's letter to Exxon in which the agency states its support of an Exxon proposal for the use of bioremediation to clean up the Valdez oil spill.

United States Environmental Protection Agency
Office of Research and Development
Washington, D.C. 20460
July 26, 1989

Mr. K. T. Koonce
Senior Vice President
Exxon Corporation
P.O. Box 670
Valdez, Alaska 99686

Dear Mr. Koonce:

As part of our cooperative agreement with Exxon on the Bioremediation Project in Prince William Sound, the Environmental Protection Agency (EPA) agreed to provide information that would help Exxon decide on whether to use nutrients as a technique to clean up oil contaminated shorelines in Alaska this summer. As you are aware, all data to make a definitive recommendation on the efficacy of bioremediation are not available at this time. However, given the data presently available, the significant potential positive benefits, the absence of adverse ecological effects, and the limited time remaining in the summer season in Alaska, EPA would support an Exxon proposal for nutrient addition on oil contaminated shorelines. We recommend the following regarding nutrient types, pretreatment application rates, and monitoring.

1. Nutrient Application. Application of both oleophilic fertilizer and a slow release soluble fertilizer is recommended for cobble and mixed sand and gravel shorelines. Preliminary information from our field studies show that the oleophilic fertilizer enhances the removal of oil from the surfaces of cobblestone and gravel. However, there is insufficient evidence to demonstrate that oleophilic fertilizer enhances the degradation of the less accessible oil found under large cobblestones and at any significant depth in the sediment. We believe oil degradation in these areas would be optimized by the application of slow release soluble nutrient formulations in conjunction with the oleophilic fertilizer. Nutrient release from these formulations will allow penetration into the less accessible areas through tidal flushing. While we recommend simultaneous application of both types of fertilizers, we recognize that there are beach situations where, due to the physical constraints or other factors, it would be appropriate to apply either one or the other fertilizer.

2. Pretreatment. For bioremediation to provide maximum cleanup to heavily and moderately oiled shoreline, physical cleaning should precede the application of nutrients. For lightly oiled shoreline, physical cleanup is not recommended prior to nutrient application.

3. Rates of Fertilizer Application. Rates of application are an important consideration to ensure maximum effective loading of fertilizer with the minimum environmental impact. It is recommended that an oleophilic fertilizer be used at an application rate that covers oiled areas completely with a thin coating of the product (approximately 0.06 lbs/ft2 of beach area). The slow release fertilizer should release nitrogen (ammonia or nitrate) and phosphate rates of 1-10 and 0.1-0.5 mg/1/day per 100 grams of granules, respectively, for periods of up to 40 days.

4. Ecological Effects and Monitoring. Fertilizer application should be initially conducted on those oil-contaminated shorelines that are exposed to adequate flushing through the action of the tides and wind. Based on mathematical model projections for tidal mixing and dilution and our monitoring studies to date, these areas should not experience any adverse ecological effects at recommended application rates.

The potential for algal blooms from nutrient addition and direct toxicity to marine biota from the oleophilic fertilizer (during or after application) is greatest in protected, poorly flushed embayments, particularly if large portions of the shorelines are treated. When such embayments are considered for bioremediation, the mixing characteristics should be established prior to nutrient application. It is recommended that you consult with NOAA and examine bays for obstructions to mixing and flushing, such as sills at bay entrances and strong stratifications as indicated by abrupt and large pycnoclines or sags in dissolved oxygen. If the information shows adequate flushing and dilution of the fertilizers under the worst-case situation (complete and rapid transport of the fertilizers off the beaches into receiving waters), then large scale application of nutrients in these types of embayments is appropriate. If the sufficiency of flushing and dilution are questionable for controlling algal blooms and toxicity, we recommend that ecological monitoring should be carried out along with the fertilizer application. The following monitoring parameters should be considered:

  • total hexane-extractable hydrocarbons in the water column

  • nitrogen and phosphorous nutrients

  • plankton chlorophyll

  • total aromatic hydrocarbons bioaccumulated in mussels (held in cages at the low tide zone of the fertilized shorelines)

  • water sample toxicity using a standard effluent toxicity test program. (This test is designed to detect any general toxicity associated with the nutrient addition operation.)

If monitoring results demonstrate any adverse environmental effect, the application of the fertilizer should be terminated immediately.

We would be pleased to work with you to provide additional details, information, etc. regarding this activity.

Sincerely yours,

Erich Bretthauer
Acting Assistant Administrator for Research and Development

Vice Admiral Clyde Robbins, U.S. Coast Guard
Dennis Kelso, Commissioner, State of Alaska Department of Environmental Conservation
John Robinson, National Oceanic and Atmospheric Administration
Donald Collingswoth, Commissioner, State of Alaska Fish & Game
Paul Gates, Department of the Interior, National Parks

Robie Russell, Regional Administrator, Reg. 10
Jim Makris, Director, Chemical Emergency Preparedness and Prevention Office