Refrigeration – Processes – Fractionally solidifying a constituent and separating the same
Reexamination Certificate
2001-10-23
2003-01-21
Doerrler, William C. (Department: 1724)
Refrigeration
Processes
Fractionally solidifying a constituent and separating the same
Reexamination Certificate
active
06508078
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to the treatment of waste such as agricultural and livestock waste. More specifically, the present invention relates to the separation of valuable components, such as nutrients and purified water, from waste, such as agricultural and livestock waste, by a process that includes controlled freezing and thawing, and by a system that includes the devices to achieve the same.
2. Relevant Technology
Feedlots, animal barns, agroindustrial plants, municipal sewage, and farms that keep large numbers of animals are sources of enormous quantities of organic waste. The expression “organic waste source” will hereinafter refer to any of these sources of organic waste or to any source that similarly produces organic waste, although perhaps in different quantities or by different activities. Accordingly, “organic waste source” will hereinafter also refer to organic waste recycling and treatment plants that produce liquid and/or sludge from which purified water can be separated.
The disposal of untreated organic waste causes serious pollution problems which include those due to the waste's high content of chemically oxidizable components (expressed as COD, or chemical oxygen demand) and biochemically decomposable components (expressed as BOD, or biochemical oxygen demand). When these pollutants reach bodies of water, either because they leach from disposal sites or as a consequence of being directly released or transported into water bodies, they deoxygenate the receiving waters and impair the receiving waters' capability to support aquatic life.
Acridity and high pathogen content add to the COD and BOD problems of untreated waste disposal. Acrid gases released into the atmosphere are not only unpleasant but they can also contribute to acid deposition, global greenhouse effects, and ozone depletion.
According to background material provided by the US Environmental Protection Agency (EPA), “animal waste, if not managed properly, can run off farms and pollute nearby water bodies. Agricultural run off, rich in nutrients like nitrogen and phosphorous has been linked to dangerous toxic microorganisms such as
Pfisteria piscicida
. Pfisteria is widely believed to be responsible for major fish kills and disease events in several mid-Atlantic states and may pose a risk to human health.” Draft Strategy for Animal Feeding Operations, EPA Memorandum, Mar. 4, 1998. See also EPA To Better Protect Public Health and The Environment From Animal Feeding Operations, EPA release of Mar. 5, 1998. In particular, the relationship between swine production and waste management problems has been reported in the Task Force Report No. 124, Council for Agricultural Science and Technology,
Waste Management and Utilization in Food Production and Processing
, October 1995, pp. 42-54, 110-121.
Notwithstanding the problems referred to above and other detrimental effects of the disposal of untreated organic waste, organic waste has nutritional value for plants and some forms of organic waste contain large quantities of water that could be recycled in purified, re-useable form. Land application of these dilute wastes is facing increased regulatory scrutiny. Furthermore, water in organic waste is highly polluted and it typically cannot be re-used directly even in agricultural and livestock operations. The alternative use of synthetic fertilizers is often adopted for increasing crop yield, but this solution carries at least two undesirable implications. First, a strategy that relies only on the use of synthetic fertilizers neglects the problem of organic waste disposal. Second, the manufacture of synthetic fertilizers frequently requires consumption of considerable amounts of energy and possibly expensive synthesis materials, sometimes involves polluting subprocesses, and may produce additional waste whose safe disposal is often expensive. In addition, the fast release of most synthetic fertilizers causes leaching, which in turn leads to wasted fertilizer and the ensuing pollution problems when the leached fertilizer accumulates in canals and other bodies of water. In addition to the foregoing two problems, polices that consider organic waste as an untreatable material neglect the recovery of the large quantities of water discarded with such waste, even though water is becoming a valuable and scarce resource.
The problems inherent to organic waste production and subsequent treatment require economical processes which avoid the afore-mentioned environmental problems. The efficiency of these processes is considerably enhanced when, in addition to providing a practical disposal of organic waste, the processes convert the organic waste into a useful product, such as commercial fertilizer, preferably a slow-release fertilizer and/or lead to the recovery of purified water that can be re-used in at least agricultural and/or livestock operations. This conversion requires the recovery of the nitrogenous products in the waste and their conversion into a fertilizer that can slowly release nitrogen in a form that plants can absorb. Because of the diversity of variables that determine the economic, chemical, and environmental aspects of this conversion problem, a variety of attempts to treat organic waste have been undertaken.
As indicated above, water is becoming a valuable and scarce resource to the extent that the availability of usable water limits municipal, industrial, and agricultural development in many areas. Methods for separating purified water from contaminated aqueous media have been disclosed.
These methods include the complete freezing and complete thawing of aqueous sludge to change the coagulation characteristics of the sludge for the purpose of achieving a subsequent more dense coagulation. Other methods rely on a combination of freezing with a mechanical treatment for separating precipitated material by complete freezing of the feed material followed by partial thawing and subsequent filtration or centrifugation. Some processes operate with contaminated feed that is mixed with immiscible refrigerant. Still other methods comprise the reduction of solid waste particles to atomizable size, the subsequent complete freezing of sprayed feed in a freezing chamber, and an eventual separation that requires the waste in permanent solid form. A number of methods rely on vacuum freezing with separation of low pressure water vapor and ice, or on solid-liquid-vapor multiple phase transformations. A variety of processes are designed so that a purified water component in contaminated water is frozen out in a freezer that relies on a conventional heat exchanger. Finally other methods rely on complete freezing followed by separation of volatile components and freeze-drying of the residue.
Natural freezing has been used in the purification of water produced in association with oil and natural gas production. This type of water typically contains salts, heavy metals and organic materials that are found in the exploitation of oil and material gas formations.
A freeze-thaw/evaporation purification process has been used to treat water produced in conjunction with oil and natural gas extraction. This water reportedly contains dissolved solids at a total dissolved solid (TDS) concentration of 12,800 mg/L. The reported “net result was an 80 percent reduction in the volume of water requiring disposal. Only 1612 [barrels] of the original produced water volume [of 8000 barrels] remained with a final TDS concentration of 44,900 mg/L; the remainder having been either evaporated or purified to a level of 1010 mg/L [or about 1010 ppm].”
Treating Produced Waters in the San Juan Basin with Freeze
-
Thaw/Evaporation Process
, at <http://www.gri.org/pub/oldcontent/techn/e+p/gastips/fall97/treat.htm>, visited Jun. 16, 2000. This process reportedly operates in batch mode and when enough ice is accumulated over an elevated pipe framework, the ice is melted to recover purified water. See id. Dissolved solids in wat
Crystal Peak Farms
Doerrler William C.
Drake Malik N.
Workman & Nydegger & Seeley
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