Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2003-01-21
2003-11-25
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S739000, C210S626000, C210S743000, C210S192000, C210S629000
Reexamination Certificate
active
06652752
ABSTRACT:
The present invention is directed to the treatment of oil sludges, and in particular to biodegradation of oil sludges to environmentally-acceptable products. As such, the present invention is directed to the treatment of compositions with high sludge/total petroleum hydrocarbon concentrations, examples of which are oil refinery sludges, tank-bottom sludges from oil storage tanks or tankers, sludges from residues at oil wells, so called slop oil or treater emulsions, oil sludges from processing of solids coritaining oil wastes including centrifuged sludges, clay fines, and drilling mud residues. In contrast to waste water treatment processes utilizing low total petroleum hydrocarbon concentrations or processes for the production of single cell protein, biomass or bacterial cells.
Biodegradation of crude oil materials has primarily been directed to the clean up i.e bioremediation, of oil-contaminated soils and shorelines, as a result of onland oil spills from, for example, underground storage tanks, or from oil tankers at sea. Such bioremediation of hydrocarbons generally involves creation of conditions in the soil or on the shoreline that promote growth of microorganisms using the petroleum hydrocarbons, facilitating conversion of the hydrocarbons to biomass and/or their degradation, ultimately to carbon dioxide and water. The hydrocarbons are the source of carbon for microbial growth, although it may be necessary to add other ingredients, especially nitrogen and phosphorus, as fertilizers. Microorganisms also require a range of inorganic ions for growth, but such ions are generally present in adequate quantities in the soil that is being treated.
Bioremediation processes generally utilize aerobic microorganisms that require aeration/oxygenation by maximizing contact of the contaminated material with atmospheric oxygen through procedures of soil tilling or by aerating using positive or negative pressure air pumping systems.
The general hierarchy of microbial activity in crude oil is understood to be
aliphatics> aromatics> resins> asphaltenes. Thus, aromatic and high molecular weight hydrocarbons are more difficult to degrade, compared to the lower alkanes.
Liquid-solid treatment systems have also been used to degrade petroleum hydrocarbons. However, long degradation treatment periods were encountered, e.g 50-100 days. Land treatment of waste crude oils and refinery oil sludges has been used for many years as a method of disposal of oil and sludge. Microbial growth and biodegradation rates tend to be suboptimal in land farming processes and the process is not easily controlled. In addition the process is influenced by soil composition, weather and temperature, as well as the methods used for tilling in the land farming process. For large refineries, large areas of land have to be committed to such a process, and moreover the first step in the process involves contamination of the soil with the oils to be degraded.
U.S. Pat. No. 3,899,376 discloses a single or multi-tank system that is primarily directed to waste water treatment. The process utilizes a particular bacterial strain from a culture collection for the bioremediation process.
U.S. Pat. No. 5,364,789 discloses a microbial cleaner comprising at least one hydrocarbon-ingesting microbe strain and a biocatalyst that transforms hydrocarbons into non-toxic substances. The biocatalyst includes a non-ionic surfactant, a chlorine-absorbing salt, at least one microbe nutrient and water. It is stated that the cleaner may be used in virtually any situation requiring the removal of hydrocarbons, including cleaning contaminated soil and treating oil spills on soil and water.
A method for the biodegradation of a petroleum hydrocarbon sludge fraction has now been found, such method using a reactor.
Accordingly, an aspect of the present invention provides a method for the biodegradation of an oil-based sludge, said oil-based sludge comprising a mixture of petroleum hydrocarbons, said method comprising the steps of:
(a) forming an aqueous mixture in a reactor of an oil-in-water emulsion, bacterial culture and nutrients for said bacterial culture,
said oil-in-water emulsion being an emulsion of said oil-based sludge in water,
said bacterial culture having the ability to grow on petroleum hydrocarbons as sole carbon source and having been isolated from a hydrocarbon contaminated soil or hydrocarbon-containing sludge or other environments rich in hydrocarbon degrading bacteria, by microbial enrichment techniques using hydrocarbons in the selection medium,
said reactor containing up to 50% by volume of total petroleum hydrocarbons;
(b) maintaining said aqueous mixture under aerobic conditions in the reactor at a temperature of at least 10° C. for a period of time sufficient to reduce the amount of hydrocarbon by at least 25%, and at a pH conducive to the promotion of bacterial growth and hydrocarbon degradation; and
(c) discharging the aqueous mixture having a reduced amount of said hydrocarbons from said reactor.
In a preferred embodiment of the present invention, the nutrients comprise bioavailable nitrogen, phosphorous and potassium compounds, especially in which the nitrogen compound is an ammonium ion, nitrate or organic nitrogen, and the phosphorus is phosphate.
In another embodiment, the reactor contains about 5-50% by volume of total petroleum hydrocarbons, especially about 10-30% by volume of total petroleum hydrocarbons. The oil-based sludge preferably contains hexane-extractable hydrocarbons in an amount in the range of up to 500,000 ppm, especially in the range of 65,000-250,000 ppm. For clarity, the expression total petroleum hydrocarbons (or TPHs) as used herein is defined as hexane-extractable hydrocarbons including hexane soluble hydrocarbons.
In yet another embodiment, the nutrients are in proportions corresponding to relative proportions in bacterial cells, and supplied at concentrations which promote high levels of bacterial growth and high rates of hydrocarbon degradation.
In further embodiments, the petroleum hydrocarbons consist of mixtures of saturated hydrocarbons, aromatic hydrocarbons, hydrocarbon resins and asphaltenes, especially petroleum hydrocarbons obtained from petroleum refinery sludge, from the bottom of a storage tank for oil, from an on-land well head or from the washing of a hold in a tanker.
In other embodiments, the amount of nitrogen required to support the process is in the range of 50-1000 ppm, and preferably in the range of 300-700 ppm, and the minimum amount of phosphate is in the range of 10-200 ppm and preferably 50-150 ppm.
In additional embodiments, the aqueous mixture contains a surfactant, more especially a non-ionic or an anionic surfactant. The surfactant is in an amount sufficient to form said oil-in-water emulsion, especially in which the amount of surfactant is less than 2500 ppm and preferably less than 1500 ppm. It is preferred that the ratio of the amount of petroleum hydrocarbon to surfactant be at least 40:1.
The method of the present invention relates to the biodegradation of an oil-based sludge. The oil-based sludge comprises a mixture of petroleum hydrocarbons and may include non-petroleum solid or liquid contaminants and water. The petroleum hydrocarbon mixture would normally comprise a mixture of aliphatic hydrocarbons, aromatic hydrocarbons, hydrocarbon resins and asphaltenes.
The present invention is particularly directed to the biodegradation of a mixture of the petroleurm hydrocarbon from among the aliphatics, aromatics, resins and asphaltenes. Such mixtures of petroleum hydrocarbons may be obtained from a variety of sources. For instance, the mixture may be in form of a sludge obtained from a petroleum refinery. The sludge may also be obtained from the bottorm of a storage tank that has been used for the storage of petroleum oil, with the sludge being obtained particularly when the storage tank is cleaned or drained. Alternatively, the mixture of hydrocarbons could be a petroleum residue obtained from around an on-land well head, be an oil-containing clay fines
Singh Ajay
Ward Owen P.
Anthony Asquith & Co.
Barry Chester T.
LandOfFree
Biodegradation of oil sludge does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Biodegradation of oil sludge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biodegradation of oil sludge will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3184866