Bioremediation: It’s Working

ABSTRACTIndustial sites contaminated by past use of penta-chlorophenol and creosote are being cleaned up by nature’sown bacteria and fungi. Research by the Environmental Bio-technology Group of the Mississippi Forest Products Labora-tory (MFPL) is identifying microorganisms and methods ofcarrying out this process, which is called Bioremediation. Bio-remediation is proving far less costly than older clean-upmethods such as burning or extracting the soil to eliminatecontaminants. There are more than a dozen sites in Missis-sippi where Bioremediation may save owners from $1 mil-lion to many millions of dollars each. If the great numbersof sites around the country where the process would workare eventually treated by Bioremediation, the savings overformer clean-up methods should be in the tens to hundredsof millions of dollars. Industry and the national EnvironmentalProtection Agency (EPA) have something to say about allthis: “Keep up the good work.”

Twenty-four hours a day, 365 days ayear, two 17,000-gallon tanks at aSouth Mississippi site treat waterpumped from soil once contaminatedby wood-treating chemicals. Aftertreatment, the clean, contaminant-freewater (80,000 gallons daily) isreturned to the soil through nearby in-jection wells, or discharged into pub-licly owned treated-water channels(sewage).

Special bacteria-discovered by Dr.

Hamid Borazjani and other MississippiForest Products Laboratoryscientists-inhabit these tanks, whichare called bioreactors. These microor-ganisms quickly destroy the toxicchemicals (pentachlorophenol andcreosote) present in the water. MFPLscientists call the process Bio-remediation.

The bacteria do get something fortheir diet in addition to the wood-

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Mississippi State University Forest Products Laboratory, P.0. Box Fp, Mississippi State, MS 39762

treatment chemicals. Daily, 7 poundsof 13-13-13 fertilizer are added toeach bioreactor to maintain the need-ed levels of ammonia and phospho-rus. Still, the organisms subsist mostlyon the contaminants. Borazjani’sgroup provides the JP-Isolate bacterialcultures that break down creosote-and pentachlorophenol (PCP)-ladenwater. Just 2 liters of these organisms(a liter is slightly more than a quart)are needed to replenish the microor-ganism population in each reactorweekly.

The Bioremediation process beginswith nine wells pumping water fromthe ground into a collection system.From there, the water goes into thebioreactors. Stirred and aerated bydevices inside the tanks, and brokendown or “digested” by the bacteria,the contaminated water moves con-tinually through the big containers.

From the bioreactors, the water ispumped into another huge vesselcalled a clarifier. Here the bacteria set-tle to the bottom and are transferredautomatically back to the reactors.

The treated water rises in the clarifi-er until it spills over a circular wearplate near the outer rim and flows toa holding tank. Gravity flow thentakes it several hundred feet to the in-jection wells-eight of them-whichreturn the water to the soil. “Thewater is tested by rigid standards aftertreatment;’ says a spokesman at theSouth Mississippi site. “Federal andstate agencies require regular reportsshowing its BOD (biological oxygendemand), dissolved solids, and otherfactors.”

For the past 3 years, since the oper-ation has been in full swing, reportsfrom the site have been acceptable tothe monitoring agencies.

The once-contaminated site showsmuch progress toward a return to amore natural state. Where nothingwould grow in the chemical-laden soila few years ago, there is now a goodcrop of grass and other ground cover.Most detectable traces of creosote orPCP on the ground surface or inearthen holding tanks are gone.

As the eye witnesses the improve-ment in ground contamination, thenose indicates that the process needsto continue; water being pumped outof the ground still has a noticeablechemical smell. That means Bio-remediation and return of treatedwater to the ground will continue forthe foreseeable future.

“Industry has spent millions of dol-lars in clean-up work at this one site,as well as at 10 other locations in

Graduate Student Kim Walkerand Dr. Hamid Borazjanimeasure toxicity of highlycontaminated waste water.Bioremediation of suchwater is the subject ofWalker’s thesis. Soil,water, and solids such asutility poles all appearsuitable for Bioremediation.

Texas, Montana, California, Washing-ton, North Carolina, South Carolina,Missouri and Louisiana (and anotherin Mississippi),” says Borazjani. “Butthe cost for bacteria (or, in somecases, fungi) to clean up chemicalcontamination still is small comparedto older decontamination methods. Sowe expect savings of tens to hundredsof millions of dollars through Bio-remediation.

Contaminated water is obtained from retrieval wells like thatat left; nine wells are used to obtain the water forBioremediation. First stop is this holding and aerating tank,from which the water is pumped to two 17,000-gallon bioreactors.

“Bioremediation - bacterialdecontaminaton - costs approximately$1.25 per thousand gallons of water.That is one-fourth to one-third thecost of cleanup by activated carbontreatment, which was about the bestmethod we had before the advent ofBioremediation.”

The Environmental BiotechnologyGroup at the MFPL continues to lookfor the most suitable bacteria and fun-gi for environmental cleanup. Bi-oremediation is applicable not only tosoil and water, but to utility poles,lumber and other treated products.

Research Assistant Curry Templetonis testing the microorganisms in a nov-el way. He fills hollow tubes orcolumns with particulate materialladen with the clean-up bacteria.

Creosote or PCP-contaminatedwater is fed into the top of a column,where it slowly percolates through themedium. Before the water exits thebottom of the column, the con-taminants have been successfully re-moved. The success rate has beenhigh with this method, and Templetonis refining it by using different types ofmedia and different organisms. Even-tually this more efficient method mayreplace the need for large bioreactorsand further reduce costs.

Both bacteria and fungi have beentested on wood particles treated withPCP and creosote to simulate the ef-fect they would have on ground-uputility poles. These poles “umber upto 100 million in the United States,and disposing of them in a wayfriendly to the environment after theyhave served their purpose is an urgentproblem.

In the study with wood from utilitypoles, an MFPL graduate studentfound that both the bacterium Ar-throbacter sp. and the fungusCladosporium sp. broke down thecreosote that had been used topreserve the wood. But only Ar-throbacter sp. was effective for Bi-oremediation of PCP-treated wood.

Another approach to Bioremedia-tion is the use of thermophilic (heat-adaptable) microorganisms. Thesethermophiles thrive in places wherethe heat would immobilize or destroymost microorganisms. Since chemicalreactions are accelerated at highertemperatures, use of these microor-ganisms may make Bioremediation

A daily dose of fertilizer to water in bioreactors (top) helpskeep Bioremediation going. Water is then pumped to the clarifier(above) from the bioreactor, shown at rear right.

even more efficient. Borazjani says not reactions, such as food digestion, con-much work has yet been done with version of sugar to alcohol, and athese microorganisms, but what has host of others.been done is promising. Just as past research has focused

on finding the bacteria and fungithat will do clean-up work and iden-tifying the best ones for various tasks,much work now is needed to deter-mine if enzymes can do these tasksbetter. So, MFPL scientists are nowtrying to isolate enzymes that

The best approach to Bioremedia-tion in the future may be significantlydifferent from current methods: it maybe possible to let enzymes do theclean-up work instead of usingenzyme-containing bacteria.

Enzymes serve as catalysts fora number of well-known chemical (Please turn page)

will be useful in such directclean-up.

The use of bacteria for clean-upof wood-treatment chemicals, oilspills in the sea and other tasks isstill relatively new. Taking theshortcut of using enzymes directlycould be the next great advance inBioremediation.

“Determining the extent of con-tamination with which we mustdeal as well as the effectiveness ofclean-up methods is quite achallenge!” So says SeniorResearch Assistant David Strobel.He supervises a team of analytical

chemists whose sole mission is toidentify and quantitate chemicalcontamination in soil and water.Using state-of-the-art equipmentand procedures developed by theEPA, the team members can ana-lyze chemicals that may exist onlyat the parts-per-billion (ppb) level.

“Each environmental sample isunique,” says Strobel, “and wehave to analyze thousands of themeach year. It’s a difficult job, butwe know that this information isessential in determining the effec-tiveness of different Bioremediationtechniques.”

Research Assistant Curry Templeton (above 1.) filters contaminants through particlesholding microorganisms. Injection wells (top r.) return treated water to the ground.Plants (center T.) How grow on once-contaminated ground. Senior Research AssistantDavid Strobe1 (above r.) and his team can find contaminants at the parts-per-billion level.