Chemistry: fertilizers – Processes and products – Bacterial
Reexamination Certificate
1998-02-27
2001-05-01
Langel, Wayne (Department: 1754)
Chemistry: fertilizers
Processes and products
Bacterial
C071S010000, C071S011000, C071S015000, C210S612000, C435S268000
Reexamination Certificate
active
06224646
ABSTRACT:
The present invention relates to a method of treating waste.
BACKGROUND OF THE INVENTION
According to municipalities, government agencies, environmentalists and the public in general, odour and potential pollution sources emanating from swine facilities are the main issues that the hog industry needs to address in order to sustain its development. The most intense source of odour from livestock facilities occurs during manure handling and land application. The manure from hogs can generally be classified as low volume, high strength liquid waste. That is, waste of high strength requires high levels of oxygen to biodegrade and may contaminate ground water. Typically, most commercial hog operations feature under-floor manure storage pits. These pits are situated beneath the barns and store the manure until the manure is emptied from the pit and transferred to mid-term storage lagoons. The odour problem that arises when the manure is stored in such a manner is a result of the anaerobic conditions that exist in the lagoon. Typically, aerobic conditions exist only in the layer of manure that is in contact with air and the malodorous gases produced anaerobically beneath this layer gradually diffuse to the surface, which in turn raises the prospect of public annoyance and creates health concerns for the swine herd and the barn workers. Conditions where anaerobic processes under very low dissolved oxygen (<0.5 mg/l) conditions occur are referred to as anoxic conditions. Current methods used in controlling odour production during manure handling and land application have only been capable of suppressing or delaying odour production. Without an adequate treatment, producers are forced to handle manure that is highly non-homogeneous, which can cause a variety of technical and mechanical related problems. Therefore, a method of waste treatment must ensure odour reduction or elimination as well as a reduction in solids content or volume and waste strength. Waste strength is directly related to the Biological Oxygen Demand (BOD) of the waste. The BOD defines the waste strength in that it depicts the amount of oxygen required by the waste in order to biodegrade. Such a method will reduce handling concerns and pollution such as ground water contamination and/or air pollution caused by the malodorous gases. Furthermore, the treated waste produced should be a low strength waste and have high nutrient content (nitrogen, phosphorus, potassium) which is essential for fertilizer value.
It is of note that nutrient application to farm land must be balanced with the ability of the crops to utilize the nutrients applied. That is, excess nutrients in the fertilizer that are not absorbed by the soil are likely to contaminate the aquifers and surface water bodies. As a result, the amount of fertilizer that can be applied to a given plot of land is highly dependent upon the local soil conditions, hydrology, geology and geography. However, in many cases, it is not cost effective for swine producers to haul raw manure long distances if the land surrounding the facility is already nutrient rich. Clearly, in cases such as these, it would be preferable to be able to separate the nutrients from the manure, thereby producing a concentrated fertilizer. As a result, the condensed fertilizer could be cost effectively transported and applied to farm land significant distances away from the swine production facility.
SUMMARY OF THE INVENTION
It is an object of the invention, therefore, to provide a system for treating waste.
According to one aspect of the invention there is provided a method of treating waste liquid containing solid content comprising:
providing waste liquid containing solid content;
heating the waste to a temperature range of 40-70° C. for a time period of 12-36 hours, thereby reducing waste strength and odour of the waste; and
separating the treated waste into liquid material and solid material. Heating will eliminate many pathogens within the waste.
Preferably, the waste is mixed and shredded during heating.
Preferably, the method includes treating the waste with augmenting bacteria and enzymes prior to heating. The addition of bacteria and enzymes promotes anoxic/anaerobic breakdown of the waste in the manure pit.
Preferably, the method includes removing gases emitted during heating of the waste and bubbling the gases back into the liquid material and the solid material. As a result of this arrangement, the nutrient content of the liquid material and the solid material is enhanced.
The liquid and/or solid material may be used as fertilizer and/or disposed of as a benign waste.
Preferably, the waste strength and the odour of the waste are reduced in the absence of added chemicals.
Preferably, the nutrient content (nitrogen, phosphorus, potassium) of the waste is maintained.
The waste may be homogenized prior to and/or during heating.
The method may include heating the waste at a pH range of 8.5 to 9.5, thereby promoting production of gases. Furthermore, the heating may be done at lower than ambient pressure, which will promote liberation of gases, such as ammonia gas, nitrogen gas, methane and carbon dioxide, from the waste. The gases may then be cooled and condensed to liquid form, thereby producing liquid fertilizer.
According to a second aspect of the invention, there is provided a waste treatment system for treating waste liquid containing solid content comprising:
a reactor tank for reducing waste strength and odour of the waste, thereby producing treated waste, said reactor tank comprising:
a reactor inlet arranged to accept the waste;
heating means for heating the waste in the reactor tank;
a reactor tank homogenizing system for mixing the waste;
a shredding system to reduce particle size; and
a withdraw port for removing the treated waste from the reactor tank.
The waste treatment system may include a clarifier for separating the treated waste into liquid material and solid material, said clarifier comprising:
a clarifier inlet arranged to accept the treated waste from the withdraw port;
a liquid outlet for removing the liquid material from the clarifier; and
a solid outlet for removing the solid material from the clarifier.
The waste treatment system may include a flow equalization tank for storing and mixing of the waste, said flow equalization tank comprising;
a flow equalization tank homogenizing system for mixing the waste; and
a siphon port for supplying the waste to the reactor inlet;
Preferably, the heating means may be comprised of a heat exchange system within the reactor tank.
The waste treatment system may include de-watering means connected to the solid waste outlet for removing residual liquid from the solid material.
Preferably, the waste treatment system includes gas collection means for removing gases emitted from the waste in the reactor tank.
The waste treatment system may include gas injection means for bubbling the gases removed by the gas collection means into the liquid and solid material.
The storage inlet may comprise a cone-shaped flow distribution baffle.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:
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Arato Claudio
Hildebrand Martin
Battison A. D.
Dupuis R. W.
Langel Wayne
Manitoba Ltd.
Williams M. R.
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