Liquid purification or separation – With gas-liquid surface contact means – With separator
Reexamination Certificate
2001-05-18
2003-05-27
Upton, Christopher (Department: 1724)
Liquid purification or separation
With gas-liquid surface contact means
With separator
C210S266000, C210S532200, C210S903000, C210S617000
Reexamination Certificate
active
06569322
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to denitrification. More particularly, the present invention relates to using low-solubility metal stearates for performing denitrification.
The metal stearate denitrification system is a nutrient removal system in which nitrate is removed from water using a biological treatment method that incorporates a metal stearate such as aluminum stearate for denitrifying bacteria metabolism. In addition, some phosphate removal occurs through the precipitation of metal phosphates such as aluminum phosphate.
2. General Background of the Invention
Brief description of presently used technology and its disadvantages.
Denitrification can be used to remove excess nitrate from waste waters. These include waste waters released as oxidized effluent from home septic tanks, from municipal and agriculture oxidation lagoons, from landfills, from marine waste systems, from industrial systems, and waste waters generated within enclosed circulating systems such as aquariums. For the purpose of discussion of presently used technology, denitrification of waste waters from home septic tanks and oxidation lagoons will be used as examples.
Denitrification utilizes bacteria to reduce nitrate to nitrogen gas which is lost to the atmosphere. Denitrification rates increase with temperature and require the absence of measurable oxygen or anoxic conditions (Manahan, 1994). Different organic substrates have been tested for bacterial metabolism and the denitrification rate varies with the substrate. The most rapid rates occur using water-soluble organic compounds like acetate; however, low solubility substrates are needed for low maintenance systems. Present technology commonly utilizes wood cellulose as the bacteria substrate (Robertson and Cherry, 1994; Robertson and Anderson, 1999; Robertson et al., 2000). The problem is that cellulose-based denitrification is often incomplete and requires time on the order of a day, rather than an hour, for most of the denitrification to occur (Stoessell et al., 2001). Described herein is the use of low solubility metal stearates, in particular, aluminum stearate which bacteria can use much more rapidly than cellulose for denitrification.
At present, home septic systems, lacking a drain field, discharge their effluent into ditches in rural areas and into street curbs in urban areas. In some cases, an aeration system is used within the tank, to convert nitrogen as amunonium to nitrate prior to discharge. However, present technology does not remove nitrogen as either ammonium or nitrate from the effluent. Similar problems exist with oxidation lagoons which generally use air bubbling systems to oxidize organic matter and attempt to convert ammonium to nitrate. If the effluent is passed through a wetlands, prior to being discharged, some or all of the nitrate will be denitrified provided the residence time is of the order of days. Otherwise, the ammonium or nitrate-rich effluent is input into canals and streams.
3. Description of Related Art
The denitrification system described here was developed to remove nitrate from the effluent of aerobic septic tanks. The typical septic tank discharges ammonium-containing effluent which is oxidized to nitrate in an aerobic drain field in the soil (Wilhelm et al. 1994) . The nitrate is then subsequently removed downstream by denitrification within an anaerobic drain field having a carbon-rich substrate (Lampert and Sommer, 1997) . A problem arises in areas having a high water table (near the surface) or a limited lot size (in a town). Drainage fields are not practical under these circumstances and the effluent is usually discharged by pipe directly to a drainage ditch or street curb. Use of an air-bubbling system within the septic tank can substitute for the aerobic drain field, but the discharge still contains nitrogen in the form of nitrate. To minimize the possibility of eutrophication in surface waters, the nitrate needs to be removed prior to the effluent being discharged into a drainage ditch (Connell and Miller, 1984).
REFERENCES CITED
(All Incorporated Herein by Reference)
Connell, D. W. and G. J. Miller. 1984. Chemistry and ecotoxicology of pollution. New York, N.Y.: John Wiley and Sons.
Lambert W. and U. Sommer. 1997. Limnoecology: The ecology of lakes and Streams. Oxford, United Kingdom: Oxford University Press, Inc.
Manahan, S. E. 1994. Environmental chemistry. Boca Raton, Fla.: CRC Press, Inc.
Robertson, W. D. and M. R. Anderson. 1999. Nitrogen removal from landfill leachate using an infiltration bed coupled with a denitrification barrier. Ground Water Monitoring and Remediation 19, no. 4: 73-80.
Robertson, W. D. and J. A. Cherry. 1994. In situ denitrification of septic-system nitrate using reactive porous media barriers: Field trials. Ground Water 33, no. 1: 99-11.
Robertson W. D., D. W. Blowes, C. J. Ptacek and J. A. Cherry. 2000. Long-term performance of in situ barriers for nitrate remediation. Ground Water 38, no 5:689-695.
Stoessell, R. K., D. H. Easley and G. P. Yamazaki. (2001) Denitrification and phosphate removal using Al stearate. Ground Water Monitoring and Remediation. 21, no. 2: 89-95.
Wilhelm, S. R., S. L. Schiff and J. A. Cherry. 1994. Biogeochemical evolution of domestic waste water in septic systems: 1. Conceptional model. Ground Water 32, no. 6: 905-916.
The following U.S. Patents are incorporated herein by reference: U.S. Pat. Nos. 6,100,081; 6,077,429; 5,908,555; 5,800,709; 5,755,966; 5,494,581 and are discussed below. These are examples of patents for biotreatment processes for denitrification of waste waters and strains of denitrifying bacteria. However, none of these patents mention, discuss, or specify the use of metal stearates for denitrification as described herein.
The anoxic biotreatment cell of U.S. Pat. No. 5,908,555 is a denitrification cell designed for removing nitrates from mining, milling, and industrial-fluid wastes, incorporating an additional phosphate source and methanol as the carbon source for the bacterial substrate. This is a high-maintenance flow-through cell, requiring continuous addition of water-soluble methanol and phosphate. The biofilter of U.S. Pat. No. 6,100,081 utilizes layers of peat and wood shavings as a carbon source for the bacterial substrate for denitrification and for other processes involving water purification. The biological aerated filter of U.S. Pat. No. 5,800,709 contains both aerobic (upstream) and anaerobic (downstream) sections to accomplish both aerobic decay and anaerobic denitrification within the same vessel, but the patent does not specify a particular carbon source for the bacterial substrate for denitrification. In general, filter systems are not low maintenance, requiring backwashing to remove clogging from bacteria flocculates (biosols) and other particulate matter. Modification of activated sludge systems and bioreactors have also been proposed to facilitate denitrification in systems designed primarily for aerobic decay, e.g., U.S. Pat. Nos. 5,755,966 and 5,494,581. Finally, even the use of strains of bacteria have been patented for denitrification, e.g., a patent (U.S. Pat. No. 6,077,429) has been issued for the anaerobic perlace bacteria to denitrify nitrate and also to breakdown perchlorate.
Common soap contains metal stearate, but the metal stearate used in common soap is soluble in water and would not last long if one tried to use it as a carbon source for denitrifying bacteria.
BRIEF SUMMARY OF THE INVENTION
The unique aspect of the denitrification system of the present invention is the use of insoluble and hydrophobic metal stearate as a bacterial substrate for food for the denitrification process. For an application example, the denitrification system of the present invention can be used in an in-line system for denitrification of aerobic septic-tank effluent prior to being discharged into a drainage ditch or to a street curb.
Fl
Garvey, Smith, Nehrbass & Doody, L.L.C.
Nehrbass Seth M.
University of New Orleans Research and Technology Foundation, In
Upton Christopher
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