Liquid purification or separation – Flow – fluid pressure or material level – responsive
Reexamination Certificate
2002-02-25
2004-05-11
Barry, Chester T (Department: 1724)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
C210S188000, C210S202000, C210S150000, C210S151000, C210S532100, C210S220000, C210S143000, C210S197000, C210S196000, C210S194000
Reexamination Certificate
active
06733662
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and devices for wastewater treatment. More specifically, the invention relates to vertical shaft bioreactor wastewater treatment apparatus and methods for operating and constructing same.
BACKGROUND OF THE INVENTION
High efficiency wastewater treatment has become increasingly important as the world's population continues to grow. The quantity of water needed for human consumption and other uses has increased at a rapid pace, while the amount of naturally available water remains unchanged. The ever-increasing demand for usable, clean water has made reclamation of wastewater an essential component of growth and development of human populations.
In the United States and other developed nations, as existing metropolitan areas become overcrowded, developers are encouraged or required to construct new housing in previously undeveloped areas. Many of these undeveloped areas lack sufficient water for consumption, irrigation and similar purposes, necessitating reclamation and reuse of available water resources. For development in these areas to be successful, sewage from the residential use of water, commonly referred to as wastewater, is therefore a primary target for reclamation.
Residential wastewater has a high water content, but requires substantial processing before it can be reused because of the human waste and other contaminants mixed with it. To achieve reclamation of residential wastewater in many new development areas, isolated from existing sewage treatment facilities, on-site wastewater treatment and reclamation is highly advantageous or essential.
A wide variety of different wastewater treatment systems have been proposed for reclaiming residential sewage and other categories of wastewater. One such system disclosed in U.S. Pat. No. 2,528,649, incorporates a simple sedimentation tank for separating solid waste, or “sludge”, from wastewater. After sedimentation, the sludge is passed to a digestion system where it is allowed to settle so that clear aqueous liquid separates from the sludge. The clarified liquid is redirected back to the sedimentation tank. Unfortunately, this system suffers from a number of shortcomings that make it inefficient. In particular, the system incorporates a relatively crude sedimentation system that merely allows the influent sewage to separate and does not aerate or facilitate processing of the sewage in any other way.
A number of wastewater treatment processes comprise “biological” systems utilizing microorganisms contained in an activated biomass, or sludge for the removal of COD, phosphorous and/or nitrogen from wastewater. These treatment processes typically incorporate multiple treatment phases or “zones”, namely: (1) a preliminary treatment area; (2) a primary treatment area; and (3) a secondary treatment area. Preliminary treatment is primarily concerned with the removal of solid inorganics from untreated wastewater. Typically, this preliminary treatment encompasses a two-stage treatment process in which the debris is removed by screens and/or settling. Organic matter is carried out in the fluid stream for subsequent treatment. Primary treatment entails a physical process wherein a portion of the organics, including suspended solids such as feces, food particles, etc. is removed by flotation or sedimentation. Secondary treatment typically encompasses a biological treatment process where microorganisms are utilized to remove remaining organics, nitrogen and phosphorous from the wastewater fluid stream. Microorganism growth and metabolic activity are exploited and controlled through the use of controlled growth conditions.
In large scale municipal or industrial applications, biological treatment processes typically utilize a basin or other reservoir in which the wastewater is mixed with a suspension of biomass/sludge. Subsequent growth and metabolism of the microorganisms, and the resultant treatment of the wastewater, is carried out under aerobic and/or anaerobic/anoxic conditions. In most large scale municipal or industrial treatment systems, the various components of the treatment process are performed in discrete basins or reactors. As such, there is a continuous flow of the wastewater from one process step to the next. Biomass containing the active microorganisms may be recycled from one process step to another. The conditioning of such biomass to enhance growth of particularized subgroups of microorganisms possessing a proclivity for performing a specific type of metabolic process, e.g. phosphate removal, nitrogen removal has been the subject matter of numerous patents, including: U.S. Pat. No. 4,056,465; U.S. Pat. No. 4,487,697; U.S. Pat. No. 4,568,462; U.S. Pat. No. 5,344,562. The optimization of other components or aspects of biological wastewater treatment has also engendered a variety of patents, including: U.S. Pat. No. 2,788,127; U.S. Pat. No. 2,875,151; U.S. Pat. No. 3,440,669; U.S. Pat. No. 3,543,294; U.S. Pat. No. 4,522,722; U.S. Pat. No. 4,824,572; U.S. Pat. No. 5,290,435; U.S. Pat. No. 5,354,471; U.S. Pat. No. 5,395,527; U.S. Pat. No. 5,480,548; U.S. Pat. No.4,259,182; U.S. Pat. No. 4,780,208; U.S. Pat. No 5,252,214; U.S. Pat. No. 5,022,993; U.S. Pat. No. 5,342,522; U.S. Pat. No. 3,957,632; U.S. Pat. No. 5,098,572; U.S. Pat. No. 5,290,451; Canadian Patent # 1,064,169; Canadian Patent # 1,096,976; Canadian Patent # 1,198,837; Canadian Patent # 1,304,839; Canadian Patent # 1,307,059; Canadian Patent # 2,041,329.
Biological removal of organic carbon, nitrogen and phosphorus compounds from waste water requires attention to special environmental conditions within the processing equipment. For instance, for bacteria and other microbes to convert organic carbon compounds (measured as BOD) to carbon dioxide and water, a well mixed aerobic environment is required. Approximately one pound of oxygen is required for each pound of BOD removed. To convert nitrogen compounds to nitrogen gas and carbon dioxide, nitrosomas and nitrobacter operate in an aerobic environment consuming inorganic carbon. Approximately 4.6 pounds of oxygen is required for each pound of ammonia-N converted to nitrate-N (assuming alkalinity is sufficient). Subsequently, facultative bacteria operate in an anoxic environment consuming organic carbon and liberating nitrogen gas. Approximately 2.6 pounds of oxygen is recovered for each pound of nitrate-N converted to nitrogen gas. To biologically tie up phosphate in the cell mass, an anaerobic step to produce volatile fatty acids is required. This is followed by Poly P microbes consuming large amounts of phosphorus required to metabolize the volatile fatty acids in an aerobic environment thus concentrating the phosphate in the biomass (see, e.g., Abstract by Dr. W. Wilson Western Canada Water and Wastewater Conference Calgary AB. January 2002.)
The combination of these many biological processes ideally results in a Biological Nutrient Removal (BNR) process, sometimes called tertiary treatment. However, a well-designed tertiary treatment operation requires coordination and sequencing of a complex assemblage of components, processes and conditions. Each of the constituent biological processing steps proceeds at its own rate, with specific environmental parameters required. Efficient tertiary processing also requires the correct amounts of specialty microbes to sustain the microbial populations and perform specific processing functions.
Current wastewater treatment systems which attempt to provide tertiary treatment include Upflow Sludge Bed Filter (USBF), Sequencing Batch Reactor (SBR) and Membrane Separation Activated Sludge (MSAS) systems. The Sequencing Batch Reactor (SBR) process is a modification of the conventional activated sludge process. U.S. Pat. No. 5,503,748 discloses a long vertical shaft aerator applied to the SBR technology. The SBR process employs a number of discrete steps, typically comprising sequential fill, reaction, settlement and decantation of wastewater with biomass in an enclosed reactor. In the initial step
Barry Chester T
Graybeal Jackson Haley LLP
V.A.I. Ltd.
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