ROBERT A. EVANGELISTA

BIODEGRADATION, PASSIVE EVAPORATION, and SOIL WASHING to REMOVE PHENOL and CRESOLS

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Poly Carb, located outside of Wells in Northeastern Nevada, was a pilot-plant that demonstrated the conversion of shredded tires into a type of crude oil. My objective was to explore the feasibility of using innovative on-site environmental technologies as alternatives to off-site transportation and disposal, with its associated risks and costs. Three innovative technologies were evaluated: biodegradation, cameraicon passive evaporation, and soil washing. cameraicon1

 

Biodegradation

Shake flask tests with genetically-enhanced microorganisms initially appeared promising to biodegrade phenol and cresols in Poly Carb soil. However, soil column studies, cameraicon6 cameraicon7 with native Poly Carb soil, showed the addition of these “supercharged bugs” did not improve biodegradation compared to columns without the addition of these special microbes (the control group). cameraicon2 cameraicon3 cameraicon4 The indigenous soil microorganisms were well adapted to degrade soil contaminants. Efforts then focused on enhancing the biological activity of these “local” microbes to remove phenol and cresols from soil. cameraicon5 cameraicon8 cameraicon9 cameraicon10 cameraicon11

 

Passive Evaporation

Due to the remote location of the site, I explored passive evaporation to mobilize contaminants from the soil to the vapor phase (the open air) without any additional enhancements, such as heat or vacuum. Passive evaporation tests on native soil were carried out in a cool, damp, abandoned warehouse without soil mixing to provide a conservative design for remediation in the hot dry Nevada summer. cameraicon12 Results showed compounds disappeared steadily and predictably. cameraicon12a cameraicon15 cameraicon12c

 

Soil Washing

Soil washing is the removal of contaminants by aqueous solvents, like washing laundry. cameraicon1a Compared to the various solvents explored, plain water, without additives, worked acceptably well. cameraicon13

 

Site Cleanup (Remediation)

All of the above technologies were succesful in removing phenol and cresols from soil. cameraicon13d Soil washing was selected as the primary cleanup technology. Lessons learned from the earlier use of active---equipment and energy-intensive---soil washing to remove lead from soils (see Publications and Reports) led me to co-designed a semi-passive in-situ soil leaching system to remove phenol and cresols. cameraicon13b cameraicon13c However, process conditions were designed so that biodegradation played a secondary role in treating toxicants.

 

Construction activities encompassed: soil excavation, soil leach pit construction, and soil placement into the leach pits. cameraicon14a

 

During the cleanup phase, water intermittently irrigated the soil in the pits. cameraicon14b Activated carbon cameraicon14c removed phenol and cresols from the leach water and provided an additional media (home) for indigenous microbes to grow and consume contaminants. The soil was cleaned in less than two summer seasons. cameraicon14d cameraicon14e cameraicon14f

 

I want to thank the occasional itinerant goose or cow looking for a cool drink in the midst of a desert for making us expect the unexpected.

 

More Information

R. Mandel, H. Allen, R. Evangelista, and R. Worobel, Successful Onsite Treatment of Phenols, Cresols, 1991. PDF 1.4 MB

R. Evangelista, H. Allen, and R. Mandel, Treatment of Phenol and Cresol Contaminated Soil. Journal of Hazardous Materials, 25:343-60, 1990. PDF 1.1 MB

R. Evangelista, Soil Remediation Bench-Scale Engineering Studies, Poly-Carb Site, Wells, NV.  Prepared for the U.S. Environmental Protection Agency, 1989. PDF 4.6 MB

R. Evangelista, H. Allen, and R. Mandel. Evaporation, Soil Washing, and Biodegradation Studies for On-Site Treatment of Phenol and Cresol Contaminated Soil. American Institute of Chemical Engineers Summer National Meeting Conference Proceedings, Dallas, TX, 1988.

H. Allen, R. Mandel, and R. Evangelista. In Situ Treatment of Contaminated Soil by Evaporation, Soil Washing and Biodegradation, Wells, NV. 1988 Hazardous Materials Spills Conference Proceedings, Chicago, IL, 1988. PDF 2 MB

R. Evangelista, Soil Treatability Studies for Poly-Carb Site, Wells, NV. Prepared for the U.S. Environmental Protection Agency, 1987. PDF 2.2 MB

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