Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
1998-06-23
2001-02-20
Popovics, Robert J. (Department: 1723)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S747300, C210S769000, C210S805000, C119S447000, C119S450000
Reexamination Certificate
active
06190566
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the raising of farm animals, such as hogs, cattle and poultry, under confined conditions (e.g. in a growing building or feedlot). More particularly, the invention relates to either a new construction or retrofit system that processes the wastewater that is used to flush animal waste from the confined growing area. The process serves to extract manure from the wastewater and dispose of the manure in an environmentally responsible manner.
DESCRIPTION OF THE PRIOR ART
The confinement of farm animals according to modern agricultural techniques has produced immense environmental problems associated with waste disposal. These problems have been encountered in hog farming, feedlot cattle farming and poultry farming.
The United States Environmental Protection Agency has estimated that there are 450,000 farming operations in the United States that confine animals and of these approximately 6,600 are big enough to raise over 2,500 hogs or over 1,000 cattle or 30,000 chickens. But many farms raise far more. The EPA estimates that two thirds of the 6,600 farms do not have pollution discharge permits, and most of the existing permits are inadequate to control water pollution from the spreading of manure on land. Land spreading has always been the primary means of hog waste disposal.
Farmers, academicians, businesses and governments have devised solutions for various aspects of the animal waste situation, but these solutions are generally costly or awkward. Thus far, all efforts have yielded partial solutions, at best. Where previously the animal waste might have been sold to crop farmers for its nutrient value, the development of convenient chemical fertilizers has largely eradicated the market for cumbersome, odorous manure. Furthermore, any process that addresses environmental problems while adding significantly to farm expenses is objectionable in the extremely competitive animal growth industry.
While the problems addressed by the present invention apply to various types of animals grown in confined areas, the example of hogs raised in growing buildings is illustrative, and this type of animal farming operation will be described herein in detail, both in connection with the background of the invention and specific embodiments that illustrate details of the invention. More particularly, the present invention will be described herein in various respects with reference to the hog industry as it exists in the State of North Carolina, USA, the second largest hog producing state in the United States.
Hog farming in North Carolina has enjoyed, and suffered from, an explosive growth rate. The industry more than tripled in the period from 1990 to 1995, with over 12 million hogs marketed in 1995. Much of that production is exported to other states and other countries. Competitive pricing and increased volumes have driven a rapid trend to economize through large scale operations. Recent startups in North Carolina exceed 5000 hogs per farm, with high-tech automated factory farms processing 50,000 hogs or more.
Of course, an undesirable consequence of so many hogs is so much hog waste. North Carolina's 1995 hog crop produced as much raw waste as a country of 30 million people. While waste concentration has increased almost a hundred-fold since 1980, the waste disposal processes have remained unchanged.
Illustrative Hog Farming Operation (Prior Art)
A large scale hog farm operation incorporating prior art techniques will now be described with reference to FIG.
1
. Hogs are typically raised on grates (not shown) in close confinement growing buildings
10
from the time they are born to the time they are marketed. The hogs' manure and urine fall into troughs beneath the grates. Flush pumps
14
draw settled flushwater from a waste storage lagoon
18
to fill tanks
22
for flushing each building.
Waste accumulated in the buildings' under-floor troughs is then flushed back to the lagoon, which provides temporary storage for the wastewater until the proper conditions occur for permanent waste disposal on the spreading fields, discussed below.
Manure waste within the wastewater settles and decomposes in the lagoon. This process reduces the solid waste mass to sludge, producing extremely odorous gases which are released if the lagoon water is disturbed by excessive wind, heat, or heavy wastewater discharges. Although the lagoon's wastewater must be emptied periodically, farmers rarely remove the settled sludge. As a result, the lagoon bottom continuously rises until, after several years, the depth becomes insufficient to maintain the decomposition process. The farmer must then build another lagoon.
The lagoon's wastewater rises due to accumulation of waste plus the amount by which rainfall exceeds evaporation. To prevent overflow, the lagoon level must be reduced periodically by spreading its wastewater contents over adjacent spreading fields
24
. A typical lagoon for a 10,000 hog farm would occupy approximately six acres.
Spreading fields
24
are owned and operated by the farmer for the sole purpose of absorbing the high nutrient, bacteria laden wastewater. It is essential that the fields be planted with crops capable of completely absorbing the waste nutrients so that they do not leach through the soil to contaminate aquifers and waterways.
Effective disposal of hog waste by field spreading is dependent on the volume of waste, size of the field, type of crop and crop condition, plus care given to the spreading operation. On average, more than half of the total farm area is dedicated to the waste disposal spreading fields.
Animal waste odors cause greater distress than other forms of pollution. Farm neighbors are angered and depressed by overpowering odors and loss of property values. The primary cause of the irritating odors is the bacterial decomposition of waste beneath the lagoon's surface in the absence of oxygen. This anaerobic decomposition process releases many noxious gases, among which are ammonia, methane and volatile fatty acids. Of these, fatty acids produce the most distressing odors. Ammonia is a major contributor to acid rain, and methane contributes to global warming. These gases are released when the water becomes very warm or disturbed by winds, or by excessive waste discharges into the lagoon. Therefore, it is not surprising that the hog farm's most objectionable odors occur during emptying of the lagoon liquid onto the spreading fields. Despite the many environmental problems, anaerobic lagoons are inexpensive to operate and are therefore the most commonly used lagoons for livestock manure.
A costly alternative to the anaerobic decomposition process is achieved by aerating the lagoon. While aerobic lagoons reduce odors, ammonia is produced. Aerobic bacteria require a constant supply of oxygen which is achieved by pumping large volumes of air into the manure-water mixture. In addition, the aerobic process is dependent on sunlight. Due to the high expense of continuous oxygenation and the large surface area required, aerobic lagoons are considered impractical for most animal waste operations.
North Carolina's environmental regulations on lagoon construction, which are illustrative of those of other states, have not kept pace with the growing problems. It was generally believed that the lagoons are self-sealing; that is, sludge deposits will cover the bottom of a lagoon within months preventing escape of harmful bacteria and chemicals to the groundwater. However, recent studies show that large numbers of lagoons are leaking, some of them severely. Researchers have found that lagoons built on permeable soil may never seal adequately, and that clay based lagoons may leak after periods of hot dry weather followed by sudden rainfall. Leakproof lagoons may be built using synthetic liners or compacted bentonite clay, but sealing lagoons in this manner is costly; therefore, to date, few lagoons have been built with protective liners.
Several major lagoon breaks occurred in recent years. In one instance,
Kolber Steven N.
Myers Bigel Sibley & Sajovec P.A.
Popovics Robert J.
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