Patent Grant
8758620
None.
Water and wastewater are commonly treated using a variety of techniques. Many conventional municipal and industrial wastewater treatment plants utilize lagoon technologies in treating wastewater. In many cases, these lagoon technologies are advantageous over alternative options because they require only minimal operator attention, they can be operated by a lower class operator and they require only a relatively small amount of mechanical equipment. Additionally, lagoon technologies are typically capable of minimizing sludge handling procedures.
However, some wastewater treatment systems utilizing lagoons are not without disadvantages. Regulatory agencies, such as the United States Environmental Protection Agency (EPA), have imposed regulations requiring increased nitrification in the treatment of wastewater. In many lagoon-type systems, nitrification sufficient for meeting these increased standards typically only occurs in warm temperatures. However, in many geographical locations, including the northern half of the United States, as the ambient temperature drops during the fall and winter months, the nitrification rate within the lagoons drops to such a low rate that not all of the nitrogen contained within the wastewater entering the lagoons is treated.
Thus, a need exists for a wastewater treatment system and method capable of utilizing and adapting existing lagoon technology such that enhanced or advanced lagoon technology is capable of meeting the increased nitrification and denitrification standards imposed by regulatory agencies. Additionally, a need exists for a lagoon-based wastewater treatment system that has increased treatment and filtration solids management capabilities to reduce the wastewater's solids content, biological oxygen demand and nitrogenous content. A further need exists for an improved wastewater treatment system that includes multiple treatment zones and baffling between those zones.
The present invention is directed to a wastewater treatment system that includes a vessel or reactor for containing a liquid such as wastewater, first and second bio media and an aeration system. The first and second bio media may each be a permeable hydraulic barrier and bio filtration device adapted for hosting a major fixed film biomass and allowing the wastewater to flow therethrough while generally preventing solids from passing therethrough. The first and second bio media may each be a rigid media, a flexible media or a combination thereof. The media are characterized by their ability to promote the growth and accumulation of microbes and/or complex biomass thereon while allowing flow of wastewater through the media.
The first bio medium is located proximate an inlet end of the reactor and is generally submerged and extending horizontally substantially between the reactor's left and right sidewalls and extending vertically substantially between a top water level and the reactor's floor. As such, the first bio medium is adapted so that the wastewater may not short circuit around the bio media and instead must pass therethrough. The first bio medium may be configured for acting as a bio baffle, causing wastewater to flow generally uniformly therethrough as the wastewater is transferred into a primary reactor zone. The primary bio baffle serves to control the flow distribution of the wastewater, perform fixed film bio treatment seeding waste for treatment in secondary zones, retain primary solids and enhance bio flocculation of minute particles in the wastewater.
The second bio medium is located proximate an opposite outlet end of the reactor and is generally submerged and extending horizontally substantially between the reactor's left and right sidewalls and extending vertically substantially between a bottom water level and the reactor's floor. As such, the second bio medium is adapted such that the wastewater is required to either flow over it or pass therethrough. The secondary bio media serves to direct clear treated water out of the reactor from the surface, act as a bio filtration for microscopic particles, retain sludge in the active zone between the two bio media and act as a final stage nitrification/denitrification zone just prior to discharge.
In one embodiment, the reactor includes a selector zone located between the reactor inlet end and the first bio medium, a primary reactor zone located between the first bio medium and said second bio medium and a discharge or decanter zone located between the second bio medium and the outlet end.
The aeration system may comprise a plurality of submerged diffusers. In one embodiment, at least one of the diffusers is located near or underneath the first and/or second bio media and is adapted for promoting the shaking or flexing of the bio media when activated in order to dislodge excessive biomass therefrom, thus preventing the bio media from accumulating excessive biomass, clogging unduly and inhibiting the flow and treatment of wastewater therethrough.
In a method utilizing the wastewater system, influent wastewater is introduced into the reactor during a fill phase. In one embodiment, the influent wastewater is introduced in a substantially continuous manner The wastewater passes through the first bio medium and is retained in the primary reactor zone. During an aeration phase, aerators may be activated so as to aerate and mix the wastewater to reduce the biological oxygen demand of the wastewater and convert at least a portion of nitrogenous components in the wastewater to nitrate or nitrite components. The wastewater is then maintained in a quiescent state without aeration to allow solids contained therein to settle towards the bottom of the reactor. During the settling phase and solids separation, a highly treated and clarified upper layer and a stratified lower layer containing mixed liquor suspended solids (MLSS), including treatment microorganisms, are formed. During a decanting phase, the primary discharge of treated wastewater is passed over the second bio medium and is then discharged from the reactor via a decanter or other outlet device. A modest amount of the effluent discharged may pass through the second bio medium. The second bio medium is adapted for retaining settled solids within the primary reactor zone and/or trapping flocculated solids passing through the bio medium as the decanter is withdrawing the treated wastewater from the reactor.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.
In the accompanying drawings, which foam a part of the specification and are to be read in conjunction therewith in which like reference numerals are used to indicate like or similar parts in the various views:
The present invention relates generally to the field of treatment of wastewater, and more particularly to an improved system and method for treating wastewater containing contaminants The system and method can be employed to reduce the solids content, biological oxygen demand (BOD) and nitrogen content of wastewater. It may be implemented in new lagoons, concrete structures or other systems or may be implemented to upgrade existing concrete structures or earthen basin and lagoon type structures in order to bring those systems in conformance with regulations imposed by governmental bodies.
Referring now to the drawings and initially to
The reactor 12 may take the form of a lagoon, basin, pond, tank or other containment vessel. The reactor 12 may be constructed of concrete, earth, metal, plastic, natural or synthetic lining materials or combinations thereof. As shown, the reactor 12 includes a first or inlet end 20, a second or outlet end 22, a left side 24, a right side 26 and a generally flat bottom or floor 28. As is typical with a lagoon, the reactor 12 can include inwardly sloping walls associated with its ends 20 and 22 and sides 24 and 26. As will be discussed in more detail below, the reactor 12 comprises multiple chambers or zones through which the liquid flowing therethrough must pass during its treatment. The reactor 12 includes an inlet, which may comprise a pipe or conduit 36 forming an inlet opening 38, for introducing wastewater to the reactor 12 in an influent stream as depicted by arrow 40. The inlet opening 38 is generally proximate the inlet end 20 of the reactor and may be located near the floor 28, as shown in
The first and second bio media 14 and 16 are submerged in the liquid contained in the reactor 12. The bio media 14 and 16 should each create a permeable or porous hydraulic barrier so as to allow the liquid to flow therethrough. As such, the bio media 14 and 16 may be biological flocculation and filtering devices that are adapted to generally provide fixed film treatment and prevent solids from passing therethrough while still allowing liquids to flow therethrough.
The bio media 14 and 16 may be rigid or fixed media, a flexible media or a combination thereof The bio media 14 and 16, whether rigid or flexible, should provide a material and surface area suitable for effectively promoting the accumulation and growth of microbes thereon in a sufficient quantity to create a fixed film environment for treating the wastewater or other liquid that is undergoing treatment. When the bio media 14 and 16 includes rigid media, it may be in the form of film, sheets, disks, blocks, matrices or honeycombs and may be made of polythene, polyvinyl chloride (PVC), expanded polystyrene, natural or synthetic materials, as well as a wide variety of other materials. When the bio media 14 and 16 includes flexible media, it may be in the form of film, sheets or clusters of strips such as described in U.S. Pat. No. 7,713,415 to Tharp, et al. and marketed by Environmental Dynamics International, Inc. under the BioReef® or BioCurtain™ names. The entire disclosure of U.S. Pat. No. 7,713,415 to Tharp, et al. is hereby incorporated by reference.
In one embodiment, the flexible bio media 14 and 16 are in the form of one or more clusters 42 constructed of a plurality of individual ribbons or strips 44 bunched together to form the clusters, as illustrated in
As shown, the strips 44 are preferably arranged closely together along a length dimension L of one or more clusters 42. Each cluster 42 has a thickness dimension T that is preferably at least one inch thick and may be up to three feet thick or more in some applications. In any event, the thickness T should be substantial so that the liquid that is being treated will be exposed to a significant biomass contained on a relatively large number of strips 44 as the liquid passes through the thickness T. The bunching of the strips 20 throughout the thickness dimension T also arranges the strips such that they create a baffling effect to increase the distribution and exposure of the liquid to the surfaces of the discrete strips 20 as the liquid passes through the thickness dimension T.
While
As depicted in
As mentioned above, the bio media 14 and 16 are fully or partially submerged in the liquid being treated within the reactor and are positioned at certain heights, as illustrated in
As illustrated in the figures, the system 10 includes five zones, namely, a pre-react or selector zone 30, a first bio media zone 31, a primary reactor zone 32, a second bio media zone 33 and a discharge or decanter zone 34. However, other embodiments, including those that comprise more that two bio media zones, may have more than five zones. The selector zone 30 is generally defined between the reactor first end wall 20 and the first bio media 14. The first bio media zone 31 is located within the first bio media 14. The primary reactor zone 32 is generally defined between the first bio media 14 and the second bio media 16. The second bio media zone 33 is located within the second bio media 16. The decanter zone 34 is generally defined between the second bio media 16 and the reactor second end wall 22.
The selector zone 30 may, during all or part of the liquid treatment process, be operated in an anoxic or anaerobic condition (with little to no aeration). As such, the selector zone 30 may be adapted for providing a denitrification environment for sludge and mixed liquor suspended solids (MLSS). However, during other parts of the treatment process, the selector zone 30 may be operated in an oxic or aerobic condition. The barrier nature of the first bio media 14 has the benefit of retaining gross solids within the selector zone 30 for continued breakdown and treatment thereby maximizing the performance of the reactor 12. The selector zone 30 may comprise between approximately 5% and 50% of the overall reactor 12.
In one embodiment, the inlet sector zone 30 is of sufficient size to allow continuous influent wastewater flow into the reactor 12 even during the decanting phase. In this embodiment, the selector zone 30 is of a large enough size and the first bio media 14 acts as a baffle to provide hydraulic distribution of the wastewater into the primary reactor zone 32 such that decanting can occur over a relatively short period of time without drawing liquid from the selector zone 30 to the outlet end 22. This provides a benefit over other previous treatment systems in that that the influent flow to the reactor may be continuous and need not be stopped during the treatment cycle. When influent flow is stopped, a storage or balance tank is generally necessary in order to hold the influent until it may be released into the reactor 12. Thus, in this embodiment of the present invention where the influent flow is continuous, no storage or balance tank is required.
The first bio media zone 31 is the zone occupied by the first bio media 14. This zone 31 acts as a permeable or porous hydraulic barrier. Again, as the wastewater passes through this zone, it is exposed to the microbial biomass that grows and accumulates on the individual strips 44 or other elements of the first bio media 14 such that the microbes are able to remove suspended and soluble solids from the wastewater. The first bio media 14 and zone 31 provide a baffling effect which directs the wastewater from strip to strip to increase the exposure and contact time of the liquid with the biomass. In one embodiment, this baffling effect causes the wastewater to flow generally uniformly from the selector zone 30 to the primary reactor zone 32. As such, the first bio media 14 is able to dampen peak flows, as an adjustment. Depending upon various factors, including the thickness of the first bio media 14, the flow through the first bio media may be oxic, anoxic, anaerobic and/or aerobic. The first bio media zone 31 may, at least partially, be in an anoxic condition thereby providing a denitrification environment for the sludge and returned MLSS.
In one embodiment, the first bio media 14 are arranged in the first bio media zone 31 such that an upper portion of the zone 31 is of a higher density of media 14 and a lower portion of the zone 31 is of a lower density of media 14 in order to allow most of the wastewater to pass into the primary reactor zone 32 near the bottom of the reactor 12. Such an embodiment keeps the influent flow at a point under or into the sludge layer that typically settles near the bottom 28 of the reactor 12 during the settling and decant phases. The flow of the wastewater through the sludge layer is effective in treating the wastewater and preventing escape of waste during the decant phase, which removes clarified liquid off the top of the body of liquid in the reactor 12.
The primary reactor zone 32 is the zone in which the majority of the solids remaining in the wastewater upon passing through the first bio media 14 will settle. The primary reactor zone 32 may comprise between 30% and 90% of the overall reactor 12. The primary reactor zone 32 may include an outlet and a waste activated sludge (WAS) pump 78 for removing waste sludge and MLSS from the primary reactor zone 32 to a separate digester (not shown). Optionally, the primary reactor zone 32 may also include an outlet and pump 80 for recycling waste sludge or MLSS back to the selector zone 30. As such, the nitrified sludge or MLSS is returned to the anoxic selector for denitrification. The recycled sludge, once returned back to the selector zone 30 can also be used to seed incoming sludge.
In one embodiment, the system 10 of the present invention is designed to retain all bio solids and, thus, minimize the management of biomass in an activated sludge system. The system 10 can be self-balancing. As such, an operator does not have to measure the amount of solids generated, the concentration of the solids in the reactor 12 or the return rate of solids from the primary reactor zone 32 in order to maintain a given population of organisms.
The second bio media zone 33 is the zone occupied by the second bio media 16. Like the first bio media zone 31, this zone 33 acts as a permeable or porous hydraulic barrier. As illustrated in
The decanter zone 34 is located downstream of the second bio media zone 33. This zone 34 includes an outlet through which the treated wastewater or other liquid is discharged from the reactor 12. In one embodiment, the outlet comprises a decanter 70 for removing clarified and treated water from a top portion of the reactor 12 at a high rate. As shown in
Though not shown, the system 10 may further include an optional polishing pond or maturation lagoon for solids capture to reduce effluent biological oxygen demand (BOD) and suspended solids (SS) within the treated wastewater. In such an embodiment, the effluent discharged from the reactor 12 would be introduced to the polishing pond. The polishing pond may further be used in sludge management if no sludge waste is removed from reactor via pump 78. When no waste sludge is removed from the reactor 12, sludge and MLSS can build in the reactor 12 and the reactor 12 may take on a high degree of stabilization. When then reactor 12 reaches an equilibrium solids concentration, a large percentage of solids exit with the effluent equal to the net biomass growth. In such a case, the polishing pond is in place to separate those solids from the effluent. Systems that do not include sludge pumping and wasting from the reactor 12 will generally require a larger polishing pond. Additionally, a polishing pond can provide the system 10 with flow equalization of the intermittent decanting of the treated wastewater. This equalization allows for smaller ancillary equipment, such as chlorinators or UV disinfection, as well as smaller post-aeration or subsequent filtration or subsequent biological processes. Systems 10 utilizing a lagoon-type technology will typically include a polishing pond. In another embodiment, the effluent discharged from the reactor 12 is of suitable condition to be discharged directly into a stream.
In another embodiment, the system 10 does not have a polishing pond. In this embodiment, the decanter 70 may be designed to prevent the entry or accumulation of solids when the decanter is opened or operated. In this design, the reactor 12 may include an outlet and a waste activated sludge (WAS) pump 78 for removing waste sludge and MLSS from the reactor 12 to a separate digester (not shown), sludge-holding tank (not shown) or solids disposal or management system (not shown). Systems 10 utilizing a concrete-type tank will typically include a decanter 70 and waste sludge pumps 78 as described above.
With continued reference to the figures, the bio media 14 and 16 may be used with an aeration system 18 adapted for mixing and aerating the wastewater. The aeration system 18 may comprise a plurality of diffusers 64. In the case of suspended diffusers, the aeration system 18 may include a floating air lateral (pipe) 60 which is located at the water level and is secured in place at its opposite ends. One or both ends of each air lateral 60 receives air under pressured air from a pump or blower 57 via a main air supply line 58. The aeration devices may take the form of submerged tubular diffusers that may be suspended from the air lateral 60 on flexible hoses 62. The diffusers 64 are preferably located slightly above the bottom 28 of the reactor 12 and function in a well-known manner to diffuse air into the liquid in the reactor 12 in the form of fine bubbles which provide aeration and circulation of the liquid. In one embodiment, at least one diffuser 64 is located proximate either one or both of the first and second bio media 14 and 16. More specifically, at least one diffuser may be located underneath or directly to the side of the lower ends 50 of the first and second bio media 14 and 16. The diffusers may be adapted for promoting the shaking or flexing of the bio media 14 and 16 when activated in order dislodge excessive biomass therefrom, thus preventing the bio media 14 and 16 from excessive biomass accumulation, clogging unduly and inhibiting the flow of wastewater therethrough. It should be understood that other types of aeration devices can be employed in connection with the bio media 14 and 16, including floor mounted or surface mounted aerators. The diffusers 64 may be selectively operated (supplied with air) in order to aerate the liquid at such times and such intensities and durations as appropriate for the particular result that is desired.
The present invention is also directed to a method for treating wastewater or other liquid in order to reduce its solids content, biological oxygen demand and/or nitrogenous content. In one embodiment, the method includes four steps or phases, as each illustrated in
During the fill phase, influent wastewater to be treated is introduced into the reactor 12. As set forth above, the influent wastewater may be introduced to the reactor 12 via an inlet located 38 located proximate the reactor's inlet end 20. During the fill phase, the level of the liquid in the reactor 12 may rise from a bottom water level BWL to a top water level TWL. As the influent wastewater is introduced into the reactor 12, a portion of the water passes through the first bio media 14. Due to the first bio media's 14 baffling capabilities, this may occur in a generally uniform fashion, as represented by arrows 52. While passing through the first bio media 14, the wastewater is exposed to the fixed film microbial biomass that grows and accumulates on the individual strips 44 or other elements of the bio media 14 such that the microbes are able to remove suspended solids and soluble organics from the wastewater. It will be appreciated that the influent wastewater may be pretreated prior to be introduced to the reactor 12, for example, through screening and/or settling to remove gross solids and organics therefrom or through chemical or thermal treatment in a manner known to those of skill in the art.
During the aeration phase, some or all of the diffusers 64 are activated. The aeration system 18 may be pulsed or sequenced on a timed cycle in order to achieve aerobic and anoxic conditions on a temporal or continuous basis within the reactor 12. The aerating and mixing of the wastewater is undertaken, in part, to reduce the biological oxygen demand of the water and convert at least a portion of the nitrogenous components to nitrate components. As set forth above, the aeration system 18 includes a pump 57 for supplying air, oxygen or enriched oxygen to the diffusers 64 located at the bottom of the reactor 12. As will be appreciated, during the aeration phase, the liquid will be both aerated and mixed.
Upon termination of air or oxygen being supplied through the aerators 64, the settling phase commences. During the settling phase, the wastewater is maintained in a quiescent state such that the solids within the water will settle toward the bottom of the reactor 12 as illustrated in
Once a sufficient amount of solids settle or trend toward the bottom of the reactor 12, or least below the bottom water level BWL (i.e., below the top of the second bio media 16), the decanting phase may begin. During the decanting phase, clarified liquid is withdrawn from the reactor 12. The treated effluent may be withdrawn from the reactor 12 via a decanter 70 or other outlet device. Due to the placement of the decanter in conjunction with the second bio media 16, the decanter 70 skims only the top clarified layer of treated liquid from the reactor 12. As depicted in
From the foregoing it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.
Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5554289 | Grounds | Sep 1996 | A |
| 5736047 | Ngo | Apr 1998 | A |
| 6905602 | Dobie et al. | Jun 2005 | B1 |
| 7097767 | Gunderson, III | Aug 2006 | B2 |
| 7713415 | Tharp et al. | May 2010 | B2 |
| 20030136731 | Mandt | Jul 2003 | A1 |
| 20070119763 | Probst | May 2007 | A1 |
| 20090261027 | Elefritz, Jr. et al. | Oct 2009 | A1 |
| 20120152832 | Johnson et al. | Jun 2012 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20130270182 A1 | Oct 2013 | US |
