Effluent purifying system

Details Effluent purifying system Effluent purifying system

2000-04-11

2003-01-07

Hoey, Betsey Morrison (Department: 1724)

Liquid purification or separation

Processes

Utilizing electrical or wave energy directly applied to...

C210S742000, C210S791000, C210S085000, C210S103000, C210S195100, C210S259000, C210S407000, C210S908000

Reexamination Certificate

active

06503401

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an effluent purifying system that enables the reuse of the circulating effluent upon purification. More particularly, the invention relates to a purification method and apparatus for cleansing water of a water bath in a chiller unit used in poultry processing so the chiller wastewater can be recycled and subsequently recirculated throughout the chiller.
2. Description of Related Art
Water traditionally has been a key processing medium in food processing plants. Water is used throughout all steps of the food production process, including food cleaning, sanitizing, peeling, cooking and cooling. Water also is used as a conveyor medium that transports food materials throughout the process. Water additionally is used to clean the equipment of the processing plants between operations. Food processing is thus a water-intensive operation.
The wastewater of such food production has attributes that are distinct from other industrial activities. In particular, food processing wastewater can be characterized as “friendly” in that it generally does not contain conventional toxic chemicals such as those listed under the Environmental Protection Agency's (EPA) Toxic Release Inventory. However, food-processing wastewaters can be subject to bacterial contamination that represents a special issue for wastewater reuse.
Food processing wastewaters are distinguished by their conventionally high Biochemical Oxygen Demand (BOD) concentrations, high levels of dissolved and/or suspended solids, nutrients and minerals. If separated or recovered, many of these constituents have value in secondary markets. Reclaimed materials have value through 1) direct in-plant reuse (e.g., recovery of sugars from fruit canning), 2) sale to external markets (e.g., recovery of pasta starch for animal feed or for compost), and/or 3) use in energy recovery (e.g., through biological or thermochemical gasification).
The characteristics and generation rates of food processing wastewater are highly variable, depending on the specific types of food processing operations. One important attribute is the general scale of the operations, since the range of food processing extends from small, local operations to large-scale national and international producers. This difference in scale not only is relevant in identifying sources of wastewater, but also in determining appropriate reduction or recycling options. In addition to scale differences, the types of food production processes (e.g., poultry, meat, fish, fruit, vegetable, oils and dairy) vary widely, with associated differences in the specific wastewater contaminants. Even within a given food processing plant, the wastewater discharged from different unit operations—or from different seasons—may vary with respect to flow rates and compositions. These characteristics will all affect how readily a new reduction or recycling technology can show a return on investment.
In addition to the variability in internal operating conditions, external constraints on food production wastewater management also vary widely. Wastewater disposal costs, which are a key driver for reduction/recycling technologies, will vary based on a given food processor's location and pertinent regulatory requirements.
With the many obstacles facing wastewater reuse, water traditionally has been used on a once through basis in the food processing industry. However, due to rising utility costs, scarcity of available fresh water, costly more stringent wastewater disposal surcharges and pollution regulations, processors must now look at recycling process wastewaters, and specifically chiller overflow waters, to achieve reduced operational costs.
It is customary in the poultry processing industry to ship live birds to a processing plant where they are bled, scalded, defeathered and eviscerated. Since the scalding operations are usually carried out at about 128 degrees Fahrenheit, the eviscerated birds must be subsequently chilled prior to packaging and shipping. Before the 1960's, poultry was chilled in layers of ice or immersed in small tanks of ice water. The poultry was chilled using these methods for a sufficient amount of time to reduce the temperature of the poultry to about 40 degrees Fahrenheit or below, after which the tanks were emptied. The use of small, individual single-use tanks required significant resources, including space, employees and water or ice. Because of these disadvantages in single-use tanks, continuous immersion chillers were developed.
Continuous immersion chillers are one or more large tanks where fresh chilled water is continually replenished through which poultry carcasses continuously enter and exit. Modern chillers are equipped with refrigeration units and systems for controlling water volume, direction and agitation. These types of chillers have become more and more efficient, rapid and economical to use.
Presently, the birds are chilled in this continuous fashion in an open tank containing a mixture of ice and water for a period of about 4 to 24 hours. The water chilling step not only is used to cool the birds after scalding, but also is used for the purpose of cleaning away most of the internal and external bacteria of the birds prior to packaging. After the birds have been chilled, they are usually packed in crates with ice and shipped.
The aforementioned procedures suffer from at least three major drawbacks. First, the chiller is quickly contaminated with fecal matter,
escherichia coli
and salmonellae from the birds. These contaminants are eventually distributed throughout the chiller water and contaminate all of the carcasses moving through the system. Second, the contaminated water of the chiller presents a serious disposal problem. Processors incur substantial toll charges when dumping the contaminated water into either private lagoons or municipal sewer systems. Lastly, continual dumping of the contaminated water necessitates the replenishment with fresh water of the food processing system at significant costs.
In addition to these disadvantages, federal government regulations do not mandate the industry use enough make-up fresh water in the chiller to keep the system clean (only a half gallon per bird), nor does the government regulate how much water should be used in cleanup. Further, many in the industry try to cut costs associated with the water demands by simply using less water, leading to increased incidents of contamination.
In relation to the waste chill water, in recent years there has been increasing awareness and concern with the possibility of poultry and meat being infected with, in particular, pathogenic microorganisms such as species of salmonella or listeria bacteria, with a resultant risk of disease outbreak following human consumption of poultry, meat or meat-based foodstuffs infected in this manner. Throughout the world there are many guidelines and regulations controlling reuse of waste chill water. The poultry industry and the United States Department of Agriculture (USDA) have attempted to deal with these problems by raising the amount of make-up water to an additional half-gallon of fresh water (or four pounds of ice) for each bird that enters the chiller. Although this procedure can maintain the contaminant concentration of the chiller water at a certain level, this amount of new water remains insufficient to keep the system clean, and the process is extremely inefficient because enormous quantities of fresh water are necessary. Moreover, the procedure does not obviate the wastewater disposal problem, but actually enhances wastewater problems.
The industry has further dealt with the problem of pathogenic contamination by constructing chillers with an overflow feature that acts as a skimmer to remove water containing fat particles (floating on top) from the chiller. However, chillers constructed with such overflow features still require enormous amounts of fresh water, and further require a floor drain. Because dirty water flows out onto the floor of the

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