Classifying – separating – and assorting solids – Sifting – With liquid treatment
Reexamination Certificate
1999-04-05
2001-06-26
Nguyen, Tuan N. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
With liquid treatment
C209S307000, C209S380000, C209S390000, C210S396000, C210S400000, C210S783000
Reexamination Certificate
active
06250476
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to apparatus and methods for separating solid particles form fluids or fluid slurries and more particularly to apparatus and methods for cleaning waste water by removing suspended solids.
BACKGROUND OF THE INVENTION
Municipal wastewater is the flow of used water from a community. Although the characteristics of the wastewater vary from location to location depending on various factors, municipal waste water is typically considered as a mixture of storm water and sanitary wastewater. Storm water is runoff from precipitation, and accordingly, reflects the composition of the precipitation and the surfaces with which it comes into contact. Sanitary wastewater is a combination of domestic wastewater and other wastewater such as that discharged form commercial, institutional, and other such facilities. Domestic wastewater includes typical wastes form the kitchen, bathroom and laundry, as well as any other wastes that people may accidentally or intentionally pour down the drain.
The purpose of municipal wastewater treatment is to strip large volumes of wastewater of as much of its harmful elements as possible before releasing it to the receiving environment. Wastewater processing for large municipalities is typically divided into stages: pre-treatment, primary treatment, secondary treatment, tertiary treatment, and additional treatment. Pretreatment comprises screening the municipal wastewater to remove large solid debris such as gravel, wood, plastic and other miscellaneous trash from the wastewater. This step prevents the debris form damaging or interfering with the operation of the downstream equipment. This debris may be disposed of in a landfill or ground up and recycled.
Primary treatment involves encouraging sedimentation by slowing the flow rate of the wastewater and allowing the larger suspended particles to settle naturally due to gravity. This permits floating solids, oils, and greases o be skimmed off the surface. The sedimented contaminants (often referred to as “sludge”) may be disposed of in a variety of ways, or “activated” and used as fertilizer. Secondary treatment involves aeration of the wastewater to encourage bacteria and other micro-organisms to grow and consume dissolved organic matter. A second sedimentation step with the addition of a metal salt solution may be employed to remove phosphorus and more of the suspended particles. Chlorine or ozone may also be added to kill harmful micro-organisms. Tertiary treatment employs sand filtration or mechanical filtration to further reduce the suspended particle concentration. Additional treatment such as nutrient removal and dechlorination of the wastewater may be performed subsequent to this step. Although the cleanest water is obtained using the tertiary and additional treatment stages, they are not performed by all wastewater treatment facilities.
In general, screening solid particles from fluid streams by passing a fluid through a screen or sieve having performations of such size the solid particles are retained on the screen surface instead of passing through is well known. In the municipal wastewater pretreatment process however, it is not simply a matter of passing solid particles carried in a fluid stream across a screening device to obtain a separation. The nature of the carried-along debris may often cause blinding of the filter screen. “Blinding” is the clogging of the screens and the reduction of their open area. Further, much of the debris, such as plastic bags, rags, and string, does not lend itself to vibratory screening methods.
Consequently, the debris tends to reduce the capacity of municipal waste separation equipment by clogging the screens and reducing their open area. As more wastewater is received for processing, the debris tends to accumulate in the screening equipment. This obviously further reduces the ability of the screening equipment to screen the wastewater. Eventually, this accumulation threatens the ability of the equipment to effectively screen the wastewater and may even force an overflow or bypass of the pretreatment stage, with detrimental effects on downstream equipment. This undesirable accumulation may result in system shutdown or the need for extra equipment.
Wastewater treatment is essential to the health of the community and the environment. Unless it can be done efficiently, the cost of wastewater treatment may result in higher taxes or increased pollution. Screening equipment which operates efficiently and reliably can reduce the cost of the pre-treatment stage and thereby free up revenue for tertiary treatment or other additional treatment stages which reduce pollution.
SUMMARY OF THE INVENTION
Accordingly, there is provided herein a municipal waste separator comprising a vessel which is roughly rectangular in plan, having side plates, a back plate, and an open base upon which the vessel rests. The vessel has a fluid inlet port through which debris-laden municipal wastewater passes, a wastewater outlet through which screened municipal wastewater passes, and a debris discharge outlet through which the debris and large particles screened from the municipal wastewater pass for disposal. The separator includes a continuous inclined screening belt which passes over an upper roller and a lower roller to screen the debris from the municipal wastewater and convey it to the debris discharge outlet. A puddle of debris-laden wastewater is encouraged to form to provide a hydrostatic pressure head on the upper surface of the screening belt to assist in forcing the wastewater through the screening belt. Wastewater which passes through the apertures in the screening belt is deflected by a deflector plate which shields the return path of the screening belt. The screened wastewater is then directed to the wastewater outlet.
In a preferred embodiment, a belt-cleaning brush disposed along the return path brushes clinging debris from the screening belt toward the debris discharge outlet. Additionally, the screening belt rides on and is supported by a perforated backing plate as it travels from the lower roller to the upper roller. Overflow ports are provided to allow wastewater from the puddle to bypass the screening belt if the screening belt becomes blinded. This prevents the wastewater from exiting the separator via the debris discharge port.
The screening belt preferably includes a backing belt which provides low sliding friction and excellent wear resistance, and one or more fine screens mounted on the backing belt. Any one of the fine screens may be easily replaced in the event of damage. The fine screens separate particles larger than the aperture size from the incoming wastewater, and the wastewater that passes through the apertures is directed through the wastewater outlet for further cleaning.
In one specific embodiment, a secondary screening belt is disposed so as to catch debris conveyed by he primary screening belt. This secondary screening belt conveys the debris through a press roller, whereby the excess water is removed from the debris.
Important features of the present invention have been broadly summarized above in order that the following detailed description thereof may be better understood, and in order that the contribution to he art may be better appreciated. There are, of course, many additional features of the present invention that will be described in detail hereinafter and which will form the subject of the claims appended hereto.
REFERENCES:
patent: 985809 (1911-03-01), Hoyt
patent: 2408191 (1946-09-01), Barnett et al.
patent: 4350591 (1982-09-01), Lee
patent: 5921399 (1999-07-01), Bakula et al.
patent: 9312321 (1993-06-01), None
Bakula John J.
Kroon Scott M.
Conley & Rose & Tayon P.C.
Derrick Manufacturing Corporation
Nguyen Tuan N.
LandOfFree
Municipal waste separator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Municipal waste separator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Municipal waste separator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2465136