Germ warfare

Bioremediation, strictly speaking, has been around since the dawn of time. In its most basic form, it's a millennia-old natural process of bacteria devouring certain types of chemical compounds. As an industry, however, bioremediation is only about 30 years old, and still evolving through the use of increasingly sophisticated technology.

Bioremediation, in general, refers to the use of microbes to destroy, or render harmless to the environment, contamination. This process can be either ex situ or in situ, and can take several different forms, such as bioventing (pushing oxygen through soil to stimulate waste-destroying microbes), injection of hydrogen peroxide or magnesium peroxide (achieving oxygen delivery through the introduction of chemicals into contaminated soil) and landfarming (moving contaminated soil to a site with a leachate collection system).

For the most part, it involves providing oxygen and, if necessary, additional nutrients, to promote the growth of contaminant-eating microbes. These microbes can either be ones that previously existed at the site (biostimulation) or ones that have been added to the site (bioaugmentation). Examples include using pseudomonas putitida to treat hydrocarbons and subtilus bacillus to treat hydrocarbons and chlorinated hydrocarbons.

Once stimulated by the addition of oxygen and nutrients, the microorganism population grows, using the contaminant compounds as a food source. This process usually breaks the contaminants down into carbon dioxide and water. Once the contaminants are depleted, the microorganisms are deprived of their food source, and either die or are reduced to inconsequential numbers.

Properly applied, this cost-effective technique works on many types of organic contaminants, and can often be done on-site. It is most effective on non-halogenated volatile and semi-volatile organics and fuels. Its effectiveness is limited, however, at sites with high concentrations of metals, highly chlorinated organics or inorganic salts, as these contaminants are deadly to microorganisms. Intermediate products, which are sometimes as toxic, if not more so, than the original contaminant, can also sometimes be generated by the bioremediation process. An example is the sequential dechlorination of a compound such as perchloroethane, through anaerobic bioremediation, into vinyl chloride (VC), a much more toxic substance than any of its parent compounds. VC must be further degraded through aerobic bioremediation.

Looking beneath the surface

Bioremediation is now a widely accepted technique for contaminant cleanup. But a few short decades ago, its use for anything as exotic as the in situ cleanup of groundwater contamination was considered laughable. "At that time, there was a myth, widely held by the geological and hydrological community, that the subsurface was sterile, that there were no bacteria, and therefore no biological processes of consequence," said John Wilson, a research microbiologist with the U.S. Environmental Protection Agency's Office of Research and Development, Subsurface Protection & Remediation Division, in Ada, Okla.

"They got it from the textbooks," said Dr. Calvin H. (Herb) Ward, Foyt family chair of engineering and director of the Energy and Environmental Sciences Institute at Rice University. "Below the plow zone, there are very few bacteria, and in deeper processes, there are probably none, according to the old texts" he said. A few scientists, however, among them Richard Raymond, questioned conventional thinking.

In July 1971, a pipeline owned by the Sun Company (now Sunoco Inc.), leaked a significant amount of high-test gasoline into limestone aquifers used for drinking water, near Ambler, Penn. At the time, Raymond was a microbiologist in the research and development department of Sun's Marcus Hook facility, near Philadelphia. "We were isolating many different types of microbiological cultures that could utilize hydrocarbon. I found that they were very widely distributed throughout the world, at different depths," Raymond said. "I had isolated and studied so many different types of organisms from the soil, and realized that they degrade a lot of different compounds. That started the idea of using bioremediation for in situ groundwater contamination cleanup," he said.

Theories put to the test

Raymond and his team were dispatched to work on the Ambler site. "They Sun Co. wanted to get the product out as rapidly as possible, and they'd been skimming it, but they still had a lot of the material left," Raymond said. "At that time, there had been very little development of anything to skim or to pump product off the surface of an aquifer. So, the geologists and the well drillers had devised a system of pumping the product out of that limestone formation, but it was quite obvious that they couldn't get very much of it out; it had adsorbed to the limestone clay."

A new approach was needed for the Ambler cleanup, and Raymond put his theories about the usefulness of soil microbes to the test. That meant some fast improvisation. "At that time, there weren't any nice sparging devices, so I devised a system using aloxite stone (as a diffusing mechanism), which I had formerly used at a candy manufacturing plant, before I got into the petroleum industry. These stones were about 2 feet long," he said.

"What we did was then design plates for the ends of the stones, and we pumped air through them with big paint compressors. At any one time, we would have anywhere from a dozen to 18 of these down into the water --100 or so feet down into the water table, and that was the air supply. Then, we mixed in fertilizer -- ammonium sulfate and phosphate and some magnesium."

Through the use of a continuous sampler and several dozen well samples, Raymond determined levels of nitrogen and phosphate in the aquifer, as well as the cell mass from microbial growth. An ultraviolet continuous flow analyzer at the end of the water supply measured benzene levels. After several years, the water supply once again met EPA's safety standards of the time.

Overcoming obstacles

Raymond's successful application did not change many minds in industry, however. Misapplication of the technology by others, as well as a lack of knowledge about the process, proved difficult to overcome. "It was first considered to be snake oil," Wilson said.

"I wasn't very popular (for my theories), and it was tough to get people to believe you could get microorganisms to grow at that rate in a formation," Raymond said. Habit also proved difficult to overcome.

"Pump and treat was all anybody used; that's all anybody could imagine," Wilson said. "The problem with pump and treat is that it can only deal with the contamination in the water at that moment. For a typical gasoline spill, maybe one part in a thousand of the gasoline is actually dissolved in the water, and the rest of it's still present as an oil. So, as you remove that water, new contamination dissolves from the oily phase gasoline and replaces that contamination, so you can pump and treat forever, and it never gets clean."

Raymond's technology was applied to other sites, sometimes with mixed results. "Admittedly, there were a lot of places it was extremely difficult, because of clays. You couldn't get the transfer of oxygen and nutrients to the organisms. Those were not successful," Raymond said.

Successful persuasion

Over the next few years, the buildup of bioremediation's successes became difficult for industry to ignore. Paul Yaniga, founder of World Integrated Solutions for the Environment (W.I.S.E.) Ltd., was a regional geologist with the Pennsylvania Department of Environmental Resources in 1971, and worked with Raymond on the Ambler site. He had a first-hand view of the changing attitudes. "Even in the mid- to late-'70s, it was understood and accepted by some of the more forward-thinking working people in the industry, and a number of people in the regulatory community, but there wasn't a broad-based acceptance by industry or by the public," Yaniga said. "They thought of bacteria as bad things, as opposed to good things." Public sentiment did not begin to change until the early- to mid-'80s.

"The final thing that changed people's minds was the efficacy of properly applied bioremediation. It worked," Wilson said.

Today, increasingly sophisticated equipment and technology, as well as a better understanding of microorganisms and the contaminant degradation process, have allowed bioremediation to evolve. According to Dr. Ward, Raymond's process of aerobic bioremediation of petroleum hydrocarbons is the launching point for new technology now focused on the anaerobic bioremediation of chlorinated solvents. Ward, and many others, credit Raymond as the inventor of bioremediation.

"He very early on realized that the issue was not the concentration of contamination that might be in the water sampled, but the amount of oily phase material that was left in the aquifer. He knew you could design these remediation systems if you understood the stoichiometry of microbial metabolism and wrote it as a chemical reaction, and figured out how much raw material the bacteria needed to process the contamination, then built your designs around that, as opposed to just "Let's throw something in and see if the bad stuff goes away'," Wilson said.

Raymond's technique remains the basis for today's processes. "The technology hasn't changed. It's still identifying and enhancing organisms that can eat contaminants," Yaniga said.

After Raymond left Sun Co., he formed two bioremediation companies, Groundwater Environmental Consultants, Inc. and Biosystems Inc. Biosystems was later purchased by DuPont. Now retired, Raymond looks on his scientific contributions with fondness.

"As I've told people many times, it was so much fun, you almost couldn't accept your paycheck," he said.

As for the naysayers of 30 years ago, Raymond said, "It is gratifying to see some of the things borne out that you thought. Of course, I was mistaken in some things, I'm sure, but it's been fun."

E-sources

Natural and Accelerated Bioremediation Research ww.lbl.gov/NABIR/research_3.html

Bioremediation: Nature's Way to a Cleaner Environment

http://h2o.usgs.gov/public/wid/html/bioremed.html

A Citizen's Guide to Bioremediation

http://www.epa.gov/swertio1/download/remed/

Wealth of minds

Although many agree Richard Raymond invented the basic technique for modern bioremediation, it should be noted there are generations of scientists who also pioneered work in this field. For more information, please see the following texts:

Biodegradation and Bioremediation. Martin Alexander, 1994 Academic Press, Inc.

Bioremediation. Katherine H. Baker and Diane S. Herson, 1994. McGraw-Hill Inc.

Soil Remediation for the Petroleum Extraction Industry. Lloyd E. Deuel Jr. and George H. Holliday, 1994. PennWell Publishing Co.

Petroleum Microbiology. Ernest Beerstecher, 1954. Elsevier Press.

Petroleum Microbiology. J.B Davis, 1967. Elsevier Press.

Elementary Petroleum Microbiology. J.M. Sharpley, 1966. Gulf Publishing.

"Bacterial oxidation of crude oils," W.O. Taussoon, 1928. Neftyanoe Khoz 14:220-230.

"Microbial utilization of hydrocarbons," H.F. Haas, Yantzi, M.W. and L.D. Bushnell, 1941. Transactions of the Kansas Academy of Sciences 44:39-45.

"The bacterial oxidation of hydrocarbons," F.H. Johnson, Goodale, W.T. and Turkevich, 1941. Journal of Cellular and Comparable Physiology 19:163-72.

The bacterial oxidation of benzene. E.K. Marr, 1959. Dissertation, Penn State College.

This article originally appeared in the 10/01/1999 issue of Environmental Protection.

comments powered by Disqus