Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2001-05-16
2002-10-01
Upton, Christopher (Department: 3673)
Liquid purification or separation
Processes
Treatment by living organism
C210S617000, C210S631000, C210S694000, C210S759000, C210S150000, C210S220000, C210S908000, C435S262500, C435S309200
Reexamination Certificate
active
06458276
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the purification of groundwater contaminated with oxygenate(s) such as alkyl ethers and tertiary butyl alcohol. This invention further relates to a method and apparatus that result in the efficient biodegradation of these compounds to carbon dioxide and water. In particular, the invention relates to the remediation of groundwater contaminated with methyl-t-butyl ether (MTBE) and other ethers using fixed beds of granular activated carbon (GAC) seeded with specific MTBE degrading bacteria cultures and to a new method of seeding said carbon beds to avoid plugging, where the required amount of culture to degrade the MTBE can be determined by a formula. Also disclosed are oxygen and nutrient delivery systems.
BACKGROUND OF THE INVENTION
In response to the 1990 Clean Air Act Amendments gasoline suppliers began to blend fuels with oxygenate(s), such as alkyl ethers, particularly methyl-t-butyl ether (MTBE). MTBE often constitutes as much as 10 to 15% by volume of unleaded gasoline.
After using oxygenated fuels for about a decade, it has become apparent that the cleaner burning fuels pose distinct threats to groundwater resources. In particular, many oxygenate(s) are very soluble in water and are slow to degrade in the environment; hence they tend to accumulate in water resources once released into the environment.
Due to leaks in underground storage tanks or spills, the groundwater at many gasoline retail, distribution, and manufacturing sites is contaminated with benzene, toluene, ethyl benzene, and xylene (BTEX), as well as MTBE and other ethers. For example, MTBE has been detected in groundwater with high frequency in many states and there are well documented cases of impacts to municipal water supply wells. Due to the fact that MTBE and other ethers are characterized by the properties of high solubility in water, relatively low volatility compared to BTEX, relatively low carbon sorption coefficient, and poor biodegradability, the ethers are more easily transported in groundwater aquifers than BTEX and do not degrade through natural attenuation. While MTBE can be removed from recovered groundwater by treatment with granular activated carbon beds (GAC), it is relatively expensive compared to the treatment of BTEX because the GAC beds are subject to frequent exhaustion. Equally important, GAC is not effective at all on TBA that is found along with MTBE in contaminated groundwater.
Where groundwater contaminated with BTEX, MTBE, and other ethers is treated using activated carbon there is a need in the art for a method which reduces the need for frequent changing of the carbon bed and which also addresses the problem of degrading tertiary butyl alcohol.
In situ methods for the removal of contaminants from ground water are known. U.S. Pat. No. 5,277,518 discloses a method of in situ removal of contaminants from soil or from ground water, the method comprising the steps of establishing in situ at least one venting well comprising gas-permeable openings at an upper portion thereof and a condensate drain at a lower end thereof and removing volatile contaminants in the ground water or soil through the venting well. This reference contemplates injecting microorganisms, nutrients for the microorganisms, and oxygen. U.S. Pat. No. 5,472,294, to the same assignee, and U.S. Pat. No. 5,653,288, to the inventors of '518 and '294, provide improvements, including providing an oxygen-containing substance to the contaminants and enhancing lateral dispersion of injected materials.
U.S. Pat. No. 5,037,240 discloses a method of ‘in situ’ collection and treatment of floating, sinking and dissolved contaminants in a soil environment which involves installation of wick-like drains in at least a portion of the waste site on the down-gradient side of in-ground water flow. Some of the wick drains include porous or slotted pipes and are employed for the injection of treating chemicals or reagents into the contaminated soil for treatment in place prior to normal flow into the aquifer. Some of the drains may be employed for injection of bacteria or microbes, nutrients and/or air. U.S. Pat. No. 5,054,961, to the same assignee, discloses the added feature of forming an in-ground diversionary water barrier as a boom around at least the downstream area of said soil environment. These in situ methods do not discuss the use of carbon beds. U.S. Pat. No. 5,425,598 discloses an apparatus and method for sparging ground water by developing density driven convection and promoting the physical removal and biodegradation of contaminants.
In “Performance of Fixed Bed Reactors with Two-Phase Upflow and Downflow”, Iliuta, Ion,
J. Chem. Tech. Biotechnol.
1997, 68, 47-56, the performance of two-phase upflow and downflow fixed bed biofilm reactors, with the biocatalyst immobilized on the porous solid support was examined with the degradation of phenol selected as the test process.
Granular activated carbon (Hereafter GAC) has been used for treatment of water and wastewater at the surface. “Experiences with GAC-Fluid Bed for Bioremediation of BTEX-Contaminated Groundwaters”, G. Mazewski, J. Tiffany & Hansen, Biotechnol. Ind. Waste Treat. Biorem., (Pub. 1996)333-344(1992) relates information regarding a demonstration project and a full scale remediation project to treat groundwater from an operating recovery well at a bulk storage terminal using granular activated carbons. In this work the removal of BTEX was more satisfactory than the removal of other compounds such as MTBE.
In “Bioreactor Treatment of MTBE and TCE In Contaminated Ground Water”, by Miller, Michael E., et al, from
In Situ and On-Site Bioremediation,
Pap. Int. In Situ On-Site Biorem. Symp., 4
th
(1997),,Vol. 5, 89-94, the authors discuss a study at the Sparks Solvent/Fuel Site (Sparks, Nev.) where ground water containing MTBE, BTEX and various chlorinated solvents is treated in two granular activated carbon-fluidized bed bioreactors operating in parallel. For the first few weeks after reactor startup, 85% of the influent MTBE was removed, however effluent MTBE concentrations soon increased, indicating that the initial removal was predominately due to sorption and MTBE removal efficiencies dropped to 10-15%. Later carbon containing unidentified MTBE-degrading cultures was added to one of the fluidized bed bioreactors and the efficiency in that reactor increased to about 75%.
In “A Review of Potential Technologies for the Treatment of Methyl tertiary Butyl Ether (MTBE) in Drinking Water”, discussing a study by Anthony Brown et al., University of Southern California Department of Civil and Environmental Engineering of the Metropolitan Water District of Southern California, City of Santa Monica, the authors mention the use of GAC, along with polymeric resins and chemically modified clays, but state at page 136 adsorbability is low on GAC, adsorption capacity for MTBE is low, and frequent GAC regeneration is required. (API-National Ground Water Association “Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Remediation” Conference, Houston 11/12-14/1997)
The use of bacteria or naturally occurring microbes for biodegradation is known. U.S. Pat. No. 4,493,895 discloses microbial degradation of halogenated organic compounds. U.S. Pat. No. 5,641,679 discloses biodegradation of compounds such as naphthalene, haloaromatics, benzene, etc.
U.S. Pat. No. 5,474,934 discloses aerobic biodegradation of ethers using Amycolata sp. or a mutant. U.S. Pat. No. 5,814,514 discloses the use of propane-oxidizing bacteria for degrading an alkyl ether.
K. Mo, et al.
Appl. Microbiol. Biotechnol.
(1997) 47:69-72 proposes isolating from activated sludge and fruit of the gingko tree three pure cultures, belonging to the genuses Methylobacterium, Rhodococcus, and Arthrobacter, that are capable of degrading MTBE.
A microbe which is said to digest MTBE is described in a newspaper article by Steve Hart in
The Press Democrat,
Santa Rosa, Calif., 1 August (1999).
U.S. Pat. Nos. 5,750,364 and 5,902,73
Byers Dallas Lea
Meyer Charles Lee
Salanitro Joseph Patrick
Sun Paul Ta-chin
Shell Oil Company
Upton Christopher
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