Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-10-22
2001-03-20
Upton, Christopher (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S620000, C210S096100, C210S220000
Reexamination Certificate
active
06203702
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to biodegradable waste treatment systems, and more particularly to aerobic biodegradable waste treatment systems suitable for use with large-scale livestock operations.
BACKGROUND OF THE INVENTION
Commercial livestock raising operations continue to pursue ways in which output may be increased and costs per raised animal reduced. Recently, confined animal feeding operations (CAFOs) or “factory farms” have become widespread. These bear little resemblance to the animal husbandry operations of a century ago. In a confined animal facility, a single building houses thousands of animals, which may be cattle, pigs or poultry. In one commercial installation, about 38,000 animals are present in the facility at the same time.
The public has begun to object to these large-scale corporate farms as bad neighbors and water polluters. The keeping of thousands of animals means disposing of thousands of pounds of their bodily wastes, known as biodegradable mass or BOD (an acronym referring to the biological oxygen demand of the waste). There are two waste disposal methods which are presently employed in these operations.
The first is the spreading of untreated manure onto surrounding agricultural fields. While this fertilizes the field on which it is spread, this method produces quite objectionable odors during the spreading and creates water pollution from field runoff.
The second is the essentially anaerobic sewage treatment of the manure in large lagoons. This creates sludge disposal problems. The water used in treating the manure in this manner is released into the environment, but the water has large concentrations of ammonia and other nutrients which limit how often the wastewater can be applied to surrounding agricultural fields; only so much of the nutrients can be irrigated onto fields without exceeding the capacity of the plants therein to metabolize them. The loading of fields by wastewater streams typically is regulated by state environmental statutes. To the extent that these nutrients cannot be absorbed by the plants of the field on which they are put, the nutrients find their way into streams and rivers, creating environmental problems such as algal blooms and fish kills. There is also concern that these nutrients will begin to contaminate drinking water. Anaerobic lagoons also are remarkable for their odiferous emissions.
A combination aerobic and anaerobic lagoon has been developed by MFA Incorporated of Columbia, Mo. In this system, air is injected into the top six feet of the lagoon by diffusers which are suspended from the surface. Irrigation water and recycled water for the hog buildings to which this lagoon are connected are drawn out of the top eighteen inches of the lagoon. The MFA system is designed to control lagoon odor caused by H
2
S. It still does not meet the need of reducing combined nitrogen nutrients in the treated lagoon water, will still result in the production of large quantities of sludge and, as such, points out the need for further improvements.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a biodegradable mass treatment system has first and second treatment cells. A conduit connects the biodegradable mass source, such as a confined animal facility, with the bottom of the first cell. A first aerator means, preferably a plurality of static tube aerators, is disposed in the first cell for introducing compressed air. The first aerator means is spaced off of the bottom of the cell by at least two feet. A first anaerobic zone extends between the bottom of the cell and this aerator elevation. A first aerobic zone of the first cell extends from the aerator means elevation to the water surface. This first aerobic zone should be at least twelve feet in extent.
A transfer conduit has a first end location near the surface of the water of the first aerobic zone and a second and disposed near the bottom of a second anaerobic zone located in a second treatment cell. A second aerator means, such as a second plurality of static tube aerators, is disposed in the second cell at a predetermined distance, which should be at least two feet, from the bottom of the second cell. A second anaerobic zone extends from the second aerator means downward to the bottom of the second cell, and a second aerobic zone extends upward to the water surface of the second cell. The difference between the second aerator elevation and the water surface of the second cell is at least twelve feet.
A further conduit removes treated wastewater from the second cell for use in agricultural purposes and for use as a recycling water source. In a preferred embodiment, treated water in the aerobic zone of the second cell is fed to a water reservoir. Optionally, the third reservoir also has aeration equipment. Preferably, a portion of the water from the reservoir is recycled back to the confined animal facility for use in dilution flushing, and the remainder is sent to irrigate surrounding fields.
In another aspect of the invention, the flow rates and sizes are selected such that the system may use interruptible power, which is considerably less expensive than twenty-four hour demand power. By using power which is interrupted on a schedule (one schedule is to interrupt power for four hours every weekday afternoon), the electrical costs incurred in operating the system can be significantly reduced. One or more blowers are sized to send air to the aerations in the first and second treatment cells, such that the amount of oxygen going into solution in the aerobic zones over the residence time of forty two days is at least 2 lbs. and as much as 4.5 lbs. per pound of BOD
5
introduced into the treatment system. The volumes of the first and second cells should be large enough to contain this amount of oxygen. The blowers are so sized that the oxygen level in the aerobic zones of the treatment cells approaches a saturation level, which is about 9 mg/l (temperature 68° F. at sea level). Having this amount of oxygen available creates an “oxygen battery” which can be used to react with organic nitrogen, NH
3
, H
2
S and other objectionable contents even when power to the blowers is interrupted. Without fresh input of more air, and therefore more oxygen, into the cells, the oxygen concentrations in the cells will decline by known rates. If the cells are large enough, however, the oxygen content will never fall below 2 milligrams per liter during the power interruption period, obviating any odor problem.
The present invention has several technical advantages over other solutions to the factory farm waste problem. One of the advantages is that the present invention obviates any odor emanating from the lagoons or the treatment reservoir, and further gets rid of objectionable odors that otherwise might be associated with irrigating the crop land using treated water from the confined animal facility. Another advantage is the enhanced cleanliness of the confined animals, since in a preferred embodiment the confined animal facility is flushed at a rate of four to twelve times that of conventional practice. This prevents ammonia build up within the facility and reduces respiratory illnesses due to high humidity.
A third technical advantage is the significant reduction in the amount of combined nitrogen which is left in the treated water. The present invention, through the long residence times of the wastewater in the cells and the reservoir, allows about 68 percent of the combined nitrogen to be converted into elemental nitrogen, which is stripped off into the atmosphere. The amount of land which must be irrigated by the treated wastewater is therefore reduced to approximately one third of previous requirements, as the amount of combined nitrogen loading on the agricultural plants is reduced by this amount.
According to yet another aspect of the invention, two cells are used instead of a combined cell in order to take advantage of higher conversion rates. It is known that, in a particular cell, the amount of conversion of BOD
5
s
Perkins Jefferson
Piper Marbury Rudnick & Wolfe
Sheaffer International Ltd.
Upton Christopher
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