Karen M. Koran

Laboratory evaluation of oil spill bioremediation products in salt and freshwater systems

Ten oil spill bioremediation products were tested in the laboratory for their ability to enhance biodegradation of weathered Alaskan North Slope crude oil in both freshwater and saltwater media. The products included nutrients to stimulate inoculated microorganisms, nutrients plus an oil-degrading inoculum, nutrients plus compounds intended to stimulate oil-degrading activity, or other compounds intended to enhance microbial activity. The product tests were undertaken to evaluate significant modifications in the existing official United States Environmental Protection Agency (EPA) protocol used for qualifying commercial bioremediation agents for use in oil spills. The EPA protocol was modified to include defined formulas for the exposure waters (freshwater, saltwater), a positive control using a known inoculum and nutrients, two negative controls (one sterile, the other inoculated but nutrient-limited), and simplified oil chemical analysis. Three analysts conducted the product test independently in each type of exposure water in round-robin fashion. Statistical tests were performed on analyst variability, reproducibility, and repeatability, and the performance of the various products was quantified in both exposure media. Analysis of variance showed that the analyst error at each time-point was highly significant (P values ranged from 0.0001 to 0.008, depending on water type and oil fraction). In the saltwater tests, six products demonstrated various degrees of biodegradative activity against the alkane fraction of the crude oil and three degraded the aromatic hydrocarbons by >10%. In the freshwater tests, eight products caused >20% loss of alkane hydrocarbons, of which five degraded the alkanes by >50%. Only four products were able to degrade polycyclic aromatic hydrocarbons (PAHs) by >20%, one of which caused 88% removal. However, when the variability of the analysts was taken into consideration, only one of the ten products was found to yield significant percent removals of the PAH fraction and only in freshwater. Viable microorganism population analysis (most-probable-number method) was also performed on every sample by each operator to measure the changes in aromatic and alkane hydrocarbon-degrading organism numbers. In general, little evidence of significant growth of either alkane- or PAH-degraders occurred among any of the ten products in either the saltwater or freshwater testing.

Protocol for laboratory testing of crude-oil bioremediation products in freshwater conditions

In 1993, the Environmental Protection Agency, National Risk Management Research Laboratory (EPA, NRMRL), with the National Environmental Technology Application Center (NETAC), developed a protocol for evaluation of bioremediation products in marine environments [18]. The marine protocol was adapted for application in freshwater environments by using a chemically defined medium and an oil-degrading consortium as a positive control. Four products were tested using the modified protocol: two with nutrients and an oleophilic component; one with nutrients, sorbent, and organisms; and one microbial stimulant. A separate experiment evaluated the use of HEPES and MOPSO buffers as replacements for phosphate buffer. The oleophilic nutrient products yielded oil degradation similar to the positive control, with an average alkane removal of 97.1±2.3% and an aromatic hydrocarbon removal of 64.8±1.2%. The positive control, which received inoculum plus nutrients, demonstrated alkane degradation of 98.9±0.1% and aromatic degradation of 52.9±0.1%. The sorbent-based product with inoculum failed to demonstrate oil degradation, while the microbial stimulant showed less oil degradation than the positive control. Replacement of phosphate buffer with other buffers had no significant effect on one products performance. Differences in product performance were easily distinguishable using the protocol, and performance targets for alkane and aromatic hydrocarbon degradation are suggested.

Development of a Rational Oil Spill Dispersant Effectiveness Protocol

ABSTRACT Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column. To be considered for use, the dispersants must be listed in the National Contingency Plan (NCP) Product Schedule. Since 1994, dispersants were required to pass an effectiveness test known as the Swirling Flask Test (SFT), which is described in Appendix C of 40 CFR 300. Listing of a dispersant on the NCP Product Schedule is contingent on the dispersant being at least 45% effective in dispersing South Louisiana crude (SLC) and Prudhoe Bay crude (PBC) oils as measured and calculated by the test. Shortly after adopting the SFT, the U.S. Environmental Protection Agency (EPA) began to receive complaints that the test was too rigorous and few dispersants that were previously listed on the NCP Product Schedule could achieve the 45% effectiveness criterion. Additionally, the SFT has been found to give widely varying results in the hands of different testi...

Development and testing of a new protocol for evaluating the effectiveness of oil spill surface washing agents

As defined by the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), a surface washing agent (SWA) is a product that removes oil from solid surfaces, such as beaches, rocks, and concrete, through a detergency mechanism and that does not involve dispersing or solubilizing the oil into the water column. Commercial products require testing to qualify for listing on the NCP Product Schedule. Such testing is conducted both for toxicity and effectiveness. Protocols currently exist for bioremediation agents and dispersants, but not SWAs. The US Environmental Protection Agency (EPA) is developing a laboratory testing protocol to evaluate the effectiveness of SWAs in removing crude oil from a solid substrate. This paper summarizes some of the defining research supporting this new protocol. Multiple variables were tested to determine their effect on SWA performance. The protocol was most sensitive to SWA-to-oil ratio and rotational speed of mixing. Less sensitive variables were contact time, mixing time, and SWA concentration when total applied mass of active product was constant. EPA recommendations for the testing protocol will be made following round robin testing.

EFFECT OF VARIABLES ON PERFORMANCE OF SURFACE WASHING AGENTS UNDER A NEWLY DEVELOPED TESTING PROTOCOL

ABSTRACT Surface washing agents (SWAs) can be used following an oil spill event to enhance the removal of stranded oil from shorelines and other surfaces. The U.S. Environmental Protection Agency (EPA) has developed a testing protocol to evaluate the effectiveness of SWAs in the laboratory. Using this protocol, the effects of substrate type, substrate hydration, and SWA-to-oil ratio (SOR) on the ability of SWAs to remove crude oil were evaluated. Experiments were conducted using Prudhoe Bay Crude (PBC) oil applied to three substrates under wet and dry conditions. Oil recovery efficiencies were similar for substrates made up of sand and the smaller of two gravels, while a decrease in efficiency was observed for the larger, more heterogeneous gravel. For the controls without SWA, after we compared dry and wet substrates, we decided dry substrates would be preferable for purposes of the protocol because variability was much lower and differences between treated and control samples were greater. To determine ...

DEVELOPMENT OF A SURFACE WASHING AGENT EFFECTIVENESS PROTOCOL

ABSTRACT The U.S. Environmental Protection Agency (EPA) is developing a protocol for testing the effectiveness of surface washing agents (SWAs) in a laboratory setting. The criteria for evaluating SWA effectiveness is based on the amount of crude oil that can be removed from a substrate with a specified amount of test cleaner. For protocol development and testing, acid washed sand was used as the shoreline substrate. Prudhoe Bay Crude, a medium weight EPA/American Petroleum Institute (API) standard reference oil, and three SWAs were tested. Oil was applied to the sand in 2″ x2″ x2″ stainless steel mesh baskets and allowed to weather for a period of time before the SWA was applied. SWA was applied as a neat solution at a product to oil volume ratio of 2:1. The baskets were then submerged in seawater in 1-L beakers and agitated on a rotary shaker table. The effects of testing variables, including substrate hydration, mode of oil application, oil-weathering time, oil-SWA contact time, mixing speed, and mixin...

Biodegradability of Orimulsion in Saltwater and Freshwater Environments1

ABSTRACT Shake flask and respirometer experiments were executed to test the biodegradability of Orimulsion in freshwater and saltwater. For each experimental setup, two concentrations of the Orimulsion and the appropriate bacterial inoculum were added to artificial seawater and freshwater solutions, and the concentrations of Orimulsion hydrocarbons were monitored with time. Respirometers were used to monitor oxygen (O2) uptake and carbon dioxide (CO2) evolution to determine when to sample the shake flasks. Sampling of shake flasks occurred periodically by sacrificing triplicate flasks for each treatment. Residual hydrocarbons were extracted with dichloromethane and quantified by gas chromatography/mass spectrometry (GC/MS). The respirometry flasks were sacrificed on the last shake-flask sampling event and similarly evaluated for residual hydrocarbon content and for Microtox toxicity. Data reported confirm literature citations that Orimulsion is indeed biodegradable, at least to some extent. In the 10 g/L ...