Liquid purification or separation – Processes – Including geographic feature
Reexamination Certificate
2002-04-15
2003-06-10
Hoey, Betsey Morrison (Department: 1724)
Liquid purification or separation
Processes
Including geographic feature
Reexamination Certificate
active
06576142
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The field of the present invention relates generally to methods of treating agricultural equipment, alleys and lagoons to improve the effectiveness of the equipment, safety of the alleys and quality of the water stored in the lagoons and used therefrom. More specifically, this invention relates to methods of utilizing sulfuric acid and sulfuric acid compounds to treat agricultural equipment, alleys and lagoons used in confined animal feeding operations.
B. Background
It is well known that the storage and treatment of manure and management of manure in confined animal feeding operations, such as those used for dairy, poultry and swine is one of the most difficult, expensive and potentially limiting problems facing the agricultural industry today. Animal excrement, in the form of manure, contains high amounts of nitrates and other chemical constituents such as salts, much of which derives from the animal feed, that make such manure undesirable for contact with fresh water sources, such as rivers and underground aquifers, and difficult to treat or remove once it contaminates fresh water. As a result, manure management is an important task for every confined animal feeding operation and can require a significant amount of resources, including labor, land, equipment and financial resources.
In one increasingly popular method of operation, manure handling in confined animal feeding operations consists of a hydraulic flushing system that flushes the animal manure from the animal holding area, typically having concrete alleys and walkways, to deliver the manure, as a slurry, to a storage area where the water is stored and then utilized for irrigation. Often, a portion of the water from the storage area is utilized for recirculation through the waste handling system to clean the alleys and various agricultural equipment. The storage areas for animal waste handling systems are usually lagoons, ponds, pits and similar surface storage areas (collectively, referred to as “lagoons”) that are located on or near the agricultural property on which the manure is generated. Is also common for the manure from the lagoon to be used to irrigate agricultural crops, typically after being mixed with four to five parts of fresh water for every one part of recycled water.
The manure from livestock operations is comprised of the dry feed matter that is fed to livestock and the nutrients associated with that feed matter, including magnesium phosphate and calcium phosphate. This material ends up in the manure handling and treatment system where the high solids and nutrients content causes problems, particularly in the associated agricultural equipment, alleys in the holding area and lagoons. The high solids content results in sludge buildup on the equipment and alleys and lagoon. The sludge buildup also impacts the ability of the pumps to pump fluid from the lagoon and the solids material can plug equipment utilized in the manure handling system, including screens, separators and other equipment. When used to rinse the alleys in the animal holding areas, these materials can create conditions unsafe (i.e., slippery) for the animals. In the lagoon, the solids materials take up space in the lagoon that needs to be used to store water.
In addition, if the irrigation water that is taken from the lagoon contains high solids content, then this material can hinder crop seed germination and growth. If not managed properly, the high nutrient content of the lagoon water will overload the land with nutrients, particularly nitrogen, which can contaminate groundwater or surface water resources. Salts in the lagoon water can seal the soil, causing drainage and crop growing problems, including toxicity to plants. Odors and gases produced during the decomposition of the manure and other materials in the lagoon can adversely impact air quality and be a nuisance to neighbors who live downwind. As a result, there is continuing demand for livestock producers and handlers to improve their animal manure management practices to develop best management practices (“BMP”) to minimize the impact of their livestock operations on the environment and their neighbors.
To improve the operation and efficiency of the manure handling system, most livestock operators utilize one or more waste treatment methods as part of a manure treatment system, such as manure separators, biological materials, flush water, mechanical excavation and slurry spreading. When they function properly, manure separators utilize screens to separate out a portion of the solid materials from the manure slurry prior to the slurry reaching the lagoon. The solid material separated out by the separator is hauled away for fertilizer and used as bedding for animals in free stall barns. Over time, the separator screens and the piping associated with the flushing system can become plugged with precipitate and waste materials. A common form of the precipitate found in the manure handling systems of confined animal feeding operations is struvite, having a chemical composition made up of oxygen, phosphorus, magnesium, hydrogen and nitrogen. As is well know in confined animal feeding operations, struvite build-up in the piping system and flow lines can severely limit the flow capacity of the lines and the pressure available for use to clean the manure handling system. Typically, the struvite build-up occurs over a period of time in the flush lines. This is dependant upon the diet that is fed to the animals and the quality of the water flowing through the lines.
A number of livestock operators favor a biological solution to the foregoing manure handling problems, requiring the introduction of microbes into the lagoon to facilitate a biological breakdown of the solid and liquid nutrient materials stored in the lagoon. Biological agents are costly and can be sensitive to changing conditions. Under some circumstances, the quality of the lagoon can be improved by the addition of fresh water to change its chemical balance. Typically, even with the various treatment methods, mechanical excavation is periodically required when the capacity of the lagoon is diminished to the point where storage capacity and effective treatment are severely impacted. In addition to the excavation, this method of treatment results in additional expense for disposal of the excavated materials. As an alternative, under the right circumstances the livestock operator can pump out excess manure slurry and spread the slurry on agricultural lands utilizing liquid manure trucks. The spreading of slurry requires consideration of the content of the slurry (i.e., percent of nitrogen), the impact of that content on the crops, the amount of material that can be safely and effectively applied to the agricultural land and soil compaction from the trucks driving on the fields while spreading the slurry.
Even with the availability of the foregoing waste treatment methods, a number of problems still exist. For instance, many confined animal feeding operations, particularly in the dairy industry, utilize concrete alleys or lanes which confine and transport the animal manure, both liquid and solid. These alleys are flushed several times a day with recirculating water from the lagoon. The nutrients in the manure can cause bacteria and/or algae growth to accumulate on the concrete alley walkways and cause an animal to slip and fall, which can result in injury or death for the animal. In addition, the pipes carrying the recirculating fluid to and from the lagoon to flush the concrete lanes can become so clogged with struvite, the precipitate material comprising magnesium phosphate and calcium phosphate, and entrapped manure, that the flush system must be operated over much longer periods of time in order to properly flush the alleys of manure. Various tests and a review of research literature has determined that the struvite precipitate material is adaptable for removal with sulfuric acid.
Sulfuric acid is one of the most commonly used and readily available industrial chemica
Verdegaal Russell J.
Verdegaal, Jr. George F.
Hoey Betsey Morrison
Ryan Richard A.
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