Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
1999-06-15
2002-03-26
Morrison Hoey, Betsey (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S192000, C210S205000
Reexamination Certificate
active
06361698
ABSTRACT:
TECHNICAL ART
The instant invention generally relates to a purification and odor-control system for wastewater or liquid containment areas.
BACKGROUND OF THE INVENTION
Recent attention has focused on the need for environmental control in and around manure lagoons. Odors resulting from many manure lagoons and containment areas significantly detract from the use, enjoyment, and value of surrounding property. The formation of a manure crust seals the containment area thereby preventing natural aeration and contributing to an unbalanced anaerobic state. In fact, in colder climates, the formation of an ice cap over the crust acts to further seal the lagoon and creates a greenhouse effect. The spring thaw results in an acute and malodorous release of methane, hydrogen sulfide, and other gases. The formation of the crust also creates a breeding ground for flies, believed to be the primary disease vector from the farm to the surrounding community. Birds, in turn, often feed on the fly larvae and constitute a secondary disease vector. Crust formation also seals the lagoon from aerobic replenishment, and therefore contributes to an anaerobic state in the lagoon wherein odoriferous compounds are maximized. Finally, crust formation also inhibits slurry removal thereby contributing to an inoperable lagoon. The benefits of odor control and crust prevention thus become obvious.
Economic and political pressures are now encouraging the development of pig farms, in lieu of tobacco farms for example. Recent developments however, have restricted the design of new or expanding pig farms. Concerns such as odor, air quality, and ground and surface water quality, often implicating the Clean Water Act and/or the Clean Air Act, drive the restrictions.
In fact, a recent U.S. Senate study details the magnitude of environmental problems caused by animal waste. The findings indicate that the amount of animal manure produced annually is conservatively estimated to be 130 times greater than the amount of human waste produced. Stated another way, a 50,000 acre farm in Utah has been cited as potentially producing more waste than the entire city of Los Angeles. Other findings indicate that agricultural officials consider 60% of rivers and streams “impaired”, with agricultural runoff the largest contributor to the pollution. Anecdotally, a 30,000 fish kill resulted from a weekend hog manure spill in Iowa. Efforts are therefore currently underway to impose national standards on livestock producers.
On a state level, certain areas such as North Carolina have enacted moratoriums on new or expanding hog farms. North Carolina has also granted counties zoning control over farms with more than 5,000 hogs. Industry experts warn that as more restrictions are placed on U.S. hog farms, pork production could move to other countries thereby damaging family farms and sending food profits overseas. The net result of further restrictions limits the land use and therefore detracts from the profitability of the farmland.
Aside from the private and public nuisance concerns, acute odors also indicate the potential for disease and reduced hog propagation due to respiratory problems, for example. In humans, even lower concentrations (100-300 parts per billion) of gases such as hydrogen sulfide are known to cause eye irritation, headaches, diarrhea, nausea, and an inability to sleep. Many of the gases, bacteria, viruses, spores, and worms found in manure contribute to a number of illnesses that may inhibit the full maturation of the swine, result in condemnation of all or part of the pig, and/or result in their premature deaths. In addition, many pathogens harmful to animals may also be harmful to workers. The swine flu and “farmer's lung” are illustrative. It is believed that insects and birds transfer these pathogens to the surrounding community.
In general, hog manure and urine contains or evolves into ammonia, hydrogen sulfide, methane, nitrates, trihalomethanes, spores of molds, and other contaminants. Research has shown that animal effluvia and the putrefactive gases resulting from animal and vegetable tissue are generally present in and around hog barns. Putrefaction produces highly odorous gases and compounds such as ammonia, amino acids, aromatic fatty acids, metabolites, mercaptans, indole, skatole, cresol, and alkaloid-like ptomaines such as tetramethylene-diamine and pentamethylene-diamine.
Several methods of storage and/or disposal include above-ground slurry storage, below-ground slurry storage, anaerobic lagoons with or without cover, aerated lagoons, oxidation ditches, and solid/liquid separation. Each method has its advantages and disadvantages.
Slurry storages are comparatively very costly, but the added cost is often the least risk option for farmers because slurry storages guard against mechanical and human failures that could result in environmental concerns. Straw covers are sometimes used in an effort to control odors. Other materials such as macadamia husks, cornstalks, plastic, peat moss, foam, and leka rock may also be used to cover the storage areas. The cost increases depending on the material. Additionally, temperature, humidity and light intensity can adversely effect the performance of biocovers such as straw and cornstalks. Covers may mask but do not eliminate the odors, however, and furthermore they do little, if anything, to eliminate or reduce the fly population.
A common misconception is that covers control odors. Covers actually promote poor lagoon health because there is little or no air for aerobic activity. Therefore, the odors associated with the liquid will actually increase over time. The anaerobic activity in a covered lagoon is increased for awhile, but in an unbalanced state (i.e. oxygen and aerobe deficient), the lagoon can quickly become unstable resulting in very poor organic treatment (i.e. solids buildup). Other problems associated with covered lagoons are confined explosive and toxic gases beneath the cover which must be vented, unhealthy recycle water (to the barn flushing system) that contains foul gases and higher pathogenic loads, and poor solids treatment capacity. Nevertheless, where covers are still desired, the disadvantages stated above drive improvements in the control of covered containment areas.
In the same way, odors, crust formation, and flies also plague anaerobic and aerobic lagoons open to the environment. Alternatively, the use of oxidation ditches and liquid/solid separation processes are significantly more costly as compared to other waste management methods.
Scientists have attempted to reduce odors from the annual spring runoff into the North Saskatchewan River at Edmonton, Alberta. The odors have been characterized as septic, manure, musty, earthy, and hay-like. Despite oxidative treatment, the odors persisted thereby supporting the scientists' belief of the futility of relying strictly on oxidative treatment. Other odor control methods have incorporated aeration with costly additives to control the odors.
Other efforts are underway to reduce or eliminate manure odors. For example, the University of Minnesota Agricultural Engineering department recently began a project to measure, chart, and record odors emitted from different livestock production sites around Minnesota. As one engineer states, there is currently very limited knowledge about the odor from hog production systems. The main thrust of the project is to develop a database to assist communities and pork producers in developing reasonable expectations about odor. At the national Center for Agricultural Utilization Research in Peoria, Ill., researchers sought one million dollars to attack the malodorous nature of manure. Other problems tabled for action include air and groundwater quality.
The use of ozone is well known as a disinfectant or sterilizing agent. In general, due to its disinfecting properties, ozone has not been considered a viable or feasible alternative when treating manure pits or lagoons. The conventional wisdom is that disinfection caused by the use of ozone would interfer
Dinnin & Dunn P..C.
Hoey Betsey Morrison
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