WO2024044368A1

WO2024044368A1 - Granular activated sludge in a variable water level reactor

Info

Publication number: WO2024044368A1
Application number: PCT/US2023/031168
Authority: WO
Inventors: Nicholas Andrew BARCZEWSKI
Original assignee: Evoqua Water Technologies Llc
Priority date: 2022-08-26
Filing date: 2023-08-25
Publication date: 2024-02-29

Abstract

A method of operating a sequencing batch reactor process includes introducing wastewater to be treated into the sequencing batch reactor, and selectively removing a portion of biological flocs from the wastewater in the sequencing batch reactor that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor.

Description

GRANULAR ACTIVATED SLUDGE IN A VARIABLE WATER LEVEL REACTOR

BACKGROUND

1. Field of Disclosure

Aspects and embodiments disclosed herein are generally directed to wastewater treatment, and more specifically to the treatment of wastewater in sequencing batch reactors.

2 Discussion of Related Art

Methods for treating wastewater generated from industrial and municipal sources include biological, physical, and/or chemical processes. For instance, biological treatment of wastewater may include aerobic, anoxic, and/or anaerobic treatment units to reduce the total organic content and/or biochemical oxygen demand of the wastewater and nutrients such as nitrogen and phosphorus. Wastewater treatment may be performed as a continuous process or in batch mode. One form of batch mode of wastewater treatment utilizes a sequencing batch reactor.

SUMMARY

In accordance with an aspect, there is provided a method of operating a sequencing batch reactor process. The method comprises introducing wastewater to be treated into the sequencing batch reactor, and selectively removing a portion of biological flocs from the wastewater in the sequencing batch reactor that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor.

In some embodiments, selectively removing the portion of biological flocs from the wastewater in the sequencing batch reactor includes removing effluent and the portion of biological flocs from the sequencing batch reactor dunng performance of a Settle stage of operation of the sequencing batch reactor.

In some embodiments, the effluent and the portion of biological flocs is removed from the sequencing batch reactor immediately after termination of a React stage of operation of the sequencing batch reactor.

In some embodiments, the effluent and the portion of biological flocs is removed from the sequencing batch reactor after a non-zero predetermined amount of time after termination of a React stage of operation of the sequencing batch reactor.

In some embodiments, the method further comprises directing the effluent and the

I portion of biological flocs into a clarifier/equalization basin.

In some embodiments, the method further comprises discharging solids settled in the clarifier/equalization basin and directing effluent from the clarifier/equalization basin from which the solids have settled to a disinfection operation.

In some embodiments, the method further comprises monitoring at least one of turbidity or total suspended solids in the effluent, directing the effluent and the portion of biological flocs into one of a solids/liquid separation subsystem or digester if the one of the turbidity or the total suspended solids in the effluent is above a desired level, and directing the effluent and the portion of biological flocs into a tertiary disinfection subsystem if the one of the turbidity or the total suspended solids in the effluent is below the desired level.

In some embodiments, the method further comprises directing the effluent and the portion of biological flocs into one of a filter or a ballasted solids/liquid separation system.

In some embodiments, selectively removing the portion of biological flocs from the wastewater in the sequencing batch reactor includes removing settled solids from an upper portion of a sludge blanket formed in the sequencing batch reactor during a Settle stage of operation of the sequencing batch reactor.

In accordance with another aspect, there is provided a wastewater treatment system comprising a sequencing batch reactor including a vessel for receiving a wastewater for treatment and a controller configured to operate the sequencing batch reactor to selectively remove a portion of biological flocs from the wastewater in the sequencing batch reactor vessel that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor vessel.

In some embodiments, the sequencing batch reactor further includes a decanter and the controller is configured to cause effluent and the portion of biological flocs to be removed from the sequencing batch reactor vessel through the decanter during a Settle stage of operation of the sequencing batch reactor.

In some embodiments, the system further comprises a clarifier/equalization basin having an inlet configured to receive the effluent and the portion of biological flocs from the decanter and configured to settle the portion of biological flocs from the effluent.

In some embodiments, the clarifier/equalization basin includes one or more influent distribution manifolds.

In some embodiments, the effluent and the portion of biological flocs are fed into a flocculating energy dissipating well arrangement at the inlet of the clarifier/equalization basin.

In some embodiments, the system further comprises at least one of a TSS monitor or a turbidimeter disposed on an effluent conduit of the sequencing batch reactor.

In some embodiments, the controller is configured to selectively direct the effluent and the portion of biological flocs to a solids/liquid separation unit operation or to bypass the solids/liquid separation unit operation based on a reading from the one of the TSS monitor or turbidimeter.

In some embodiments, the system further comprises a disinfection subsystem, the controller configured to direct effluent that bypasses the solids/liquid separation unit operation into the disinfection subsystem.

In some embodiments, the system further comprises one of a tertiary filter or a ballasted solids/liquid separation system, the controller configured to direct the effluent and the portion of biological flocs into the one of the tertiary filter or ballasted solids/liquid separation system.

In some embodiments, the system further comprises a first set of sludge waste outlets disposed at a bottom of the vessel and a second set of sludge waste outlets disposed at a location above the bottom of the vessel.

In some embodiments, the controller is configured to cause sludge to be discharged from the vessel primarily through the second set of sludge waste outlets.

In accordance with another aspect, there is provided a method of retrofitting a sequencing batch reactor. The method comprises programming a controller of the sequencing batch reactor to operate the sequencing batch reactor to selectively remove a portion of biological flocs from wastewater in the sequencing batch reactor that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor.

In some embodiments, the method further comprises mounting at least one of a TSS monitor or a turbidimeter on an effluent conduit of the sequencing batch reactor.

In some embodiments, the method further comprises programming the controller to selectively direct the effluent and the portion of biological flocs to a solids/liquid separation unit operation or to bypass the solids/liquid separation unit operation based on a level of TSS or turbidity in the effluent and the portion of biological flocs.

Still other aspects, embodiments, and advantages of these example aspects and embodiments, are discussed in detail below. Moreover, it is to be understood that both the foregoing information and the following detailed description are merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Embodiments disclosed herein may be combined with other embodiments, and references to “an embodiment,” “an example,” “some embodiments,” “some examples,” “an alternate embodiment,” “various embodiments,” “one embodiment,” “at least one embodiment,” “this and other embodiments,” “certain embodiments,” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects of at least one embodiment are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide an illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of any particular embodiment. The drawings, together with the remainder of the specification, serve to explain principles and operations of the described and claimed aspects and embodiments. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the figures:

FIG. 1 illustrates steps typically performed in a conventional sequencing batch reactor;

FIG. 2 is a simplified schematic diagram of a sequencing batch reactor (SBR);

FIG. 3 is a schematic diagram of one embodiment of a system for selectively increasing a concentration of more quickly settling biological floc as compared to less quickly settling biological floc in an SBR;

FIG. 4A is a schematic diagram of another embodiment of a system for selectively increasing a concentration of more quickly settling biological Hoc as compared to less quickly settling biological floc in an SBR;

FIG. 4B is a schematic diagram of another embodiment of a system for selectively increasing a concentration of more quickly settling biological Hoc as compared to less quickly settling biological floc in an SBR; FIG. 5A is a schematic diagram of another embodiment of a system for selectively increasing a concentration of more quickly settling biological floc as compared to less quickly settling biological floc in an SBR;

FIG. 5B is a schematic diagram of another embodiment of a system for selectively increasing a concentration of more quickly settling biological floc as compared to less quickly settling biological floc in an SBR; and

FIG. 6 is a schematic diagram of another embodiment of a system for selectively increasing a concentration of more quickly settling biological floc as compared to less quickly settling biological floc in an SBR.

DETAILED DESCRIPTION

Wastewater treatment systems use various processes for treating wastewater generated from municipal and industrial sources. Wastewater treatment typically includes three general phases. The first phase, or primary treatment, involves mechanically separating dense solids from less dense solids and liquids in the wastewater. Primary treatment is typically performed in sedimentation tanks using gravity separation. The second phase, or secondary treatment, involves biological conversion of ammonia and carbonaceous and nutrient material in the wastewater to more environmentally friendly forms. Secondary treatment is typically performed by promoting the consumption of the ammonia and carbonaceous and nutrient material by bacteria and other types of beneficial organisms already present in the wastewater or that are mixed into the wastewater. The third phase, or tertiary treatment, involves removing the remaining pollutant material from the wastewater. Tertiary treatment is typically performed by filtration or sedimentation with the optional addition of chemicals, UV light, and/or ozone to neutralize harmful organisms and remove any remaining pollutant material.

Secondary treatment of wastewater may be performed in a continuous flow process or in a batch process, for example, in a sequencing batch reactor. Sequencing batch reactors (SBR) or sequential batch reactors are a type of activated sludge process for the treatment of wastewater. A SBR performs a type of activated sludge process for the treatment of water/ wastewater in a single basin or vessel without return or recycle of activated sludge from downstream processes. An SBR system may include one or more SBR vessels which contain large populations of microorganisms that ingest contaminants in the influent wastewater to form biological flocs and treat the wastewater. SBRs are flexible in the sense that they can handle a wide range of wastewater flows (for example, 25,000 gpd - 100 MGD). SBR reactors treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches. Oxygen is bubbled through the mixture of wastewater and activated sludge to reduce the organic matter (measured as biochemical oxygen demand (BOD) and chemical oxygen demand (COD)). The treated effluent may be suitable for discharge to surface waters or possibly for use on land.

While there are several configurations of SBRs, the basic process is similar across the different configurations. The SBR installation includes one or more vessels that can be operated as plug flow or completely mixed reactors. The vessels have a “flow through” system, with raw wastewater (influent) coming in at one end and treated water (effluent) flowing out the other. In systems with multiple vessels, while one vessel is operating in settle/ decant mode another may be aerating and filling.

There are five stages in the treatment process:

1. Fill

2. React

3. Settle

4. Decant or Draw

5. Idle (optional)

In the Fill stage, an inlet valve of the SBR vessel opens and the vessel is filled with wastewater to be treated while mixing is provided by mechanical means (no air). The influent wastewater mixes with activated sludge remaining in the SBR vessel from treatment of a prior wastewater batch to form a mixed liquor. This stage is also called the anoxic fill stage. The anoxic fill stage may be followed by an aerobic fill stage. The Fill stage may, in one example, take about three hours to complete.

Aeration of the mixed hquor is performed during the second stage (the React stage) by the use of fixed or floating mechanical pumps or by transferring air into fine bubble diffusers fixed to the floor of the vessel. Aeration times vary according to the plant size and the composition/quantity of the incoming wastewater but are typically 60 to 90 minutes. The addition of oxygen to the mixed liquor encourages the multiplication of aerobic bacteria as they consume nutrients in the mixed liquor. This process encourages the conversion of nitrogen from its reduced ammonia form to oxidized nitrite and nitrate forms, a process known as nitrification. During the React stage biological oxygen demand (BOD) in the wastewater in the SBR is converted to microorganisms that form biological flocs. To remove phosphorus compounds from the mixed liquor, aluminum sulfate (alum) is often added during this period. It reacts to form non-soluble compounds, which settle into the sludge in the next stage.

No aeration or mixing is provided in the third stage (the Settle stage) and the settling of suspended solids starts. The Settle stage may be allowed to take place for between about 30 minutes and 60 minutes in some examples. During the Settle stage the biological flocs (also referred to simply as sludge) formed by the bacteria are allowed to settle to the bottom of the vessel. The aerobic bacteria continue to multiply until the dissolved oxygen is all but depleted. Conditions in the vessel, especially near the bottom, are now more suitable for the anaerobic bacteria to flourish. Many of these, and some of the bacteria which would prefer an oxygen environment, now start to use oxidized nitrogen instead of oxygen gas (as an alternate terminal electron acceptor) and convert the nitrogen to a gaseous state, as nitrogen oxides or, ideally , molecular nitrogen (dinitrogen, N2) gas. This is known as denitrification. The sludge is allowed to settle until clear water/supematant liquid is on the top 20 to 30 percent of the vessel contents in some examples.

During the fourth stage (the Decant stage) an outlet valve of the SBR vessel opens and the “clean” supernatant liquid exits the vessel In some implementations, the decanting stage may involve the slow lowering of a scoop or “trough” into the basin. The scoop or trough may have a piped connection to a lagoon where the final effluent is stored for disposal or to discharge if the requirements for discharge to the environment are met.

As the bacteria multiply and die, the sludge within the vessel increases over time and a waste activated sludge (WAS) pump removes some of the sludge during the settle or idle stage to a digester for further treatment. The quantity or “age” of sludge within the vessel is closely monitored, as this can have a marked effect on the treatment process.

The Decant stage may be followed immediately by another Fill stage to begin treatment of another batch of wastewater. In some examples, the end of a Decant stage may be separated from the beginning of a Fill stage by an Idle stage during which settled waste sludge is removed from the bottom of the SBR.

While these systems vary in nature, a typical SBR process will be time or flow based. Conventionally, each of the Fill, React, Settle, Decant, and optional Idle steps is done independently of each other. These steps are outlined in FIG. 1.

One potential operational issue with an SBR system is that the sludge does not settle well during the Settle stage of the process. Aspects and embodiments disclosed herein may include modifications to the control methodology for a standard SBR (also referred to herein as a variable level batch reactor) to selectively waste sludge such that granular activated sludge is produced or selectively retained within the SBR vessel, enhancing settling characteristics of the system. This helps alleviate the problem of excessive settle times in the variable level batch reactor process due to poorly settling sludge. The generation or selective retention of granular activated sludge as compared to other less quickly settling forms of sludge or biological floc in an SBR may decrease the time needed to perform a desired amount of solids settling, in some examples a reduction in settling time of up to 50% or more. The production and selective retention of granular activated sludge in an SBR in accordance to aspects and embodiments disclosed herein may also increase the wastewater treatment efficiency or effectiveness of the SBR, for example, to provide for the SBR to operate with solids loadings of up to 8,000 mg/L or more, and may allow the SBR to provide as much treatment capacity as an SBR with up to four times the volume if operating in a conventional manner without production and selective retention of granular activated sludge as described herein.

A simplified diagram of a SBR that may be utilized in various aspects and embodiments disclosed herein is illustrated in FIG. 2, indicated generally at 100. The SBR 100 may include a vessel 105 that receives wastewater 110 from a source of wastewater at an inlet 115 of the vessel 105, for example, via a wastewater pump 120 and control valve 125. A decanter 130, which may include a portion that floats on liquid 135 in the vessel 105 may drain effluent 140 through an outlet 145 of the vessel 105, optionally controlled by an output control valve 150. An oxygen-containing gas 155, for example air, may be provided to the liquid 135 in the vessel 105 via an air pump 160 to a series of aerators 165. Aerators 165 are illustrated as bubbler-type aerators located at the floor of the vessel 105, but it should be appreciated that in other embodiments other forms of aerators, for example, surface aerators may also or additionally be utilized.

A waste sludge conduit/outlet 190 and associated pump 195 may be used to remove settled waste sludge 200 from the bottom of the vessel and direct it to, for example, a sludge thickener and/or anaerobic digester for treatment or to other unit operations and disposal. Although only one waste sludge conduit/outlet 190 is illustrated in FIG. 2, it is to be appreciated that multiple waste sludge conduits/outlets 190 may be provided at different locations at the bottom of the SBR vessel 105. At least one sensor 170, for example, any one or more of a DO, ORP, or nitrogen (or nitrate or nitrite) concentration sensor may be utilized to provide data to a controller 175 that may utilize such data to control the various sub-systems of the SBR 100, for example, to control the air pump 160 to achieve or maintain a desired level of DO or ORP in the liquid 135 in the vessel 105. The indication of sensor 170 may collectively refer to at least one sensor configured to measure an oxygen demand (COD or BOD) of the liquid 130 (e.g., and ORP or nitrate concentration sensor) and at least one sensor configured to measure a concentration of dissolved oxygen in the liquid 130.

The controller 175 may be implemented using one or more computer systems which may be, for example, a general-purpose computer such as those based on an Intel® CORE™- type processor, a Motorola PowerPC® processor, a Hewlett-Packard PA-RISC® processor, a Sun UltraSPARC® processor, or any other type of processor or combination thereof. Alternatively, the computer system may include specially -programmed, special-purpose hardware, for example, an application-specific integrated circuit (ASIC), a programmable logic controller (PLC), or another form of controller intended for water treatment systems.

The computer system can include one or more processors 180 typically connected to one or more memory devices 185, which can comprise, for example, any one or more of a disk drive memory, a flash memory device, a RAM memory device, or other device for storing data. The memory may be used for storing programs and data during operation of the system. For example, the memory may be used for storing historical data relating to the parameters over a period of time, as well as operating data. Software, including programming code that implements embodiments of the invention, can be stored on a computer readable and/or writeable nonvolatile recording medium, and then copied into memory wherein it can then be executed by one or more processors. Such programming code may be written in any of a plurality of programming languages, for example, Java, Visual Basic, C, C#, or C++, Fortran, Pascal, Eiffel, Basic, or any of a variety of combinations thereof.

Components of the computer system may be coupled by one or more interconnection mechanisms, which may include one or more busses, e.g., between components that are integrated within a same device, and/or a network, e.g., between components that reside on separate discrete devices. The interconnection mechanism may enable communications, e.g., data and/or instructions, to be exchanged between components of the system. The computer system can also include one or more input devices, for example, a keyboard, mouse, trackball, microphone, touch screen, and other man-machine interface devices as well as one or more output devices, for example, a printing device, display screen, or speaker. In addition, the computer system may contain one or more interfaces that can connect the computer system to a communication network, in addition or as an alternative to the network that may be formed by one or more of the components of the system.

According to one or more embodiments of the invention, the one or more input devices may include the previously described sensor(s) 170 for measuring any one or more parameters of the liquid 135 in the SBR vessel 105. Alternatively, the sensors, and/or other components of the system, such as valves and pumps, may all be connected to a communication network that is operatively coupled to the computer system. Any one or more of the above may be coupled to another computer system or component to communicate with the computer system over one or more communication networks. Such a configuration permits any sensor or signal-generating device to be located at a significant distance from the computer system and/or allow any sensor to be located at a significant distance from any subsystem and/or the controller, while still providing data therebetween. Such communication mechanisms may be affected by utilizing any suitable technique including but not limited to those utilizing wireless protocols.

The controller 175 can include one or more computer storage media 185 such as readable and/or writeable nonvolatile recording medium in which signals can be stored that define a program to be executed by one or more processors. The medium may, for example, be a disk or flash memory. In typical operation, the one or more processors can cause data, such as code that implements one or more embodiments of the invention, to be read from the storage medium into a memory that allows for faster access to the information by the one or more processors than does the medium.

Although the computer system is described by way of example as one type of computer system upon which various aspects of the invention may be practiced, it should be appreciated that the invention is not limited to being implemented in software, or on the computer system as exemplarily shown. Indeed, rather than implemented on, for example, a general-purpose computer system, the controller, or components or subsections thereof, may alternatively be implemented as a dedicated system or as a dedicated programmable logic controller (PLC) or in a distributed control system. Further, it should be appreciated that one or more features or aspects of the invention may be implemented in software, hardware or firmware, or any combination thereof. For example, one or more segments of an algorithm executable by the controller 175 can be performed in separate computers, which can be in communication with one another through one or more networks.

One method of increasing the concentration of aerobic granular sludge in a SBR to enhance solids settling in the SBR includes utilizing the decanter 130 to selectively waste poorly settling biological flocs instead of non-selectively wasting all settled biological flocs/sludge from the SBR vessel via waste pumps 195 as is conventionally done. This is done by beginning decanting of liquid from the SBR 100 prior to completion of the Settle stage, for example, after about 5-10 minutes from the end of the React stage to allow some sei ection/ separation of the desired quickly settling biological flocs (the aerobic granular sludge) from the slower rate settling forms of biological flocs/sludge/particles. The denser, quickly settling biological flocs will tend to consolidate to form aerobic granular biological flocs or sludge particles. This causes selective formation/accumulation of quickly settling granular biological flocs within the SBR vessel and reduces the settle times to allow for more hydraulic throughput of the SBR. This method may thus also include shortening the Settle stage duration by about 50%, for example, to between 5-15 minutes. In addition to reducing the time required for the Settle stage and increasing the treatment efficiency/effectiveness of the SBR 100, this method may reduce the cost and complexity of decanters 130 by eliminating the need for the solids excluding valves on the decanters 130 since now the process is intentionally removing poorly settling solids from the SBR reactor via the decanters 130.

In one embodiment, the slower rate settling solids/flocs 205 are decanted out of the SBR 100 through the decanter 130, outlet 145, and valve 150 as shown in FIG. 2 with a portion of the clean SBR effluent 140 to another basin 210 that acts as a combined clarifier and equalization (clanfier/eq) basin. (See FIG. 3) This basin 210 is designed such that the slower rate settling solids 205 have ample time to settle and from there are discharged from the system through a waste outlet 215. The portion of the effluent 140 and slower rate settling solids 205 from the SBR decant 130 may enter the clarifier/eq basin 210 via a series of influent distribution manifolds (ID Manifolds) 220. Depending on the hydraulics this could be singular or multiple manifolds. Alternatively, the portion of the effluent 140 and slower rate settling solids 205 from the SBR decant 130 could be fed into a flocculating energy dissipating well arrangement 225 (for example, a FEDWA Energy Dissipating Inlet available from Evoqua Water Technologies LLC) at an inlet of the basin 210. In either embodiment, the goal is that the influent including the clean effluent 140 and more slowly settling solids 205 from the SBR decanter 130 does not disturb the settling capability of the basin 210. The flow of effluent 230 from the clarifier/ eq basin 210 may be achieved by volumetric displacement with the new incoming flow displacing an equal volume over weirs 235. Alternatively, a second decanter 240 may be used to continuously pull effluent from this basin 210 at a lower rate, equalizing the effluent flowrate and reducing overall costs for downstream tertiary or disinfection equipment 245.

In another embodiment, illustrated in FIG. 4 A, a TSS monitor or turbidimeter 255 is used in the SBR decant effluent conduit 250 that allows clean effluent 140 to bypass a solids recovery tank and proceed to the tertiary or disinfection step 245. The TSS monitor and/or turbidimeter may be any appropriate device such as, e.g., the ViSolid® and/or VisoTurb® sensors from Xylem, the ATS430 sensor system from ABB Inc., etc. The Decant stage may begin immediately after the end of the React stage. While the TSS or NTU readings remain high, for example, a TSS of 10 mg/L or above or a turbidity of 20 NTU or above, this is an indication of slowly settling solids remaining in the effluent decanted from the SBR and the effluent from the SBR decanter 130 is diverted to a clarifier or sludge thickener (which may be similar to basin 210) for solids processing. Effluent from which solids have settled in the clarifier or sludge thickener may be directed to the tertiary or disinfection step 245. When the TSS or NTU readings drop to an acceptable level, for example, a TSS of below 10 mg/L or a turbidity of below 20 NTU, this is an indication that the slowly settling solids have settled to below the level of the decanter and the effluent from the SBR is clean enough to be sent directly to the tertiary or disinfection step 245. The controller 175 may operate one or more valves 260, 265 and/or associated pumps (not shown) to direct effluent from the SBR vessel 105 with high TSS or turbidity to the clarifier or sludge thickener and to direct effluent from the SBR vessel 105 with low TSS or turbidity to the tertiary or disinfection step/unit operations 245. Communication lines between controller 175, TSS monitor or turbidimeter 255, and valves 260, 265 are not shown in FIG. 4A for clarity.

In an alternative to the configuration shown in FIG. 4A, the SBR decant effluent may be directed into an anaerobic digester 285 for treatment rather than to a clarifier or sludge thickener while the TSS or NTU level in the SBR decant effluent is above an acceptable level, and then into the tertiary or disinfection step 245 when the TSS or NTU level in the SBR decant effluent drops to an acceptable level. Decant of liquid from the digester may be returned to the SBR 100 through a conduit 287. Such a configuration is illustrated in FIG.

4B.

In other embodiments, the TSS monitor or turbidimeter 255 may not be utilized and the controller will direct effluent from the SBR vessel 105 to the clarifier or sludge thickener for a set period of time following the beginning of the Decant stage and then direct the effluent from the SBR vessel 105 to the tertiary or disinfection step/unit operations 245 for the remaining portion of the Decant stage.

In another embodiment, with variants illustrated in FIGS. 5A and 5B, the clean effluent 140 from the SBR decant, along with the slower rate settling solids 205, is sent to a tertiary step such as a tertiary filter 270, for example, a Forty-X® disc filter from Evoqua Water Technologies LLC or a Davco™ continuous backwash sand filter (FIG. 5A) or a ballasted solids/hquid separation system 275 (FIG. 5B) such as the CoMag® system available from Evoqua Water Technologies LLC. The slower rate settling solids 205 captured in the tertiary filter 270 can either be returned to an upstream biological treatment operation of the system via the filter backwash or sent to a sludge thickener 280 and/or anaerobic digester 285 for treatment and then wasted. The slower rate settling solids 205 separated in the ballasted solids/liquid separation system 275 are separated in a tertiary clarifier 290 and wasted.

In a further embodiment, illustrated in FIG. 6, the SBR 100 may include not just a single set of sludge waste outlets 190 located at the bottom of the SBR vessel 105, but also a second sludge waste outlet or set of outlets 300 (only one shown in FIG. 6) and associated pump 305 disposed at a location above the bottom of the vessel 105 at a level below the top of the sludge blanket 310 that forms when the Settle stage is allowed to proceed to completion as shown in FIG. 6. The second sludge waste outlet or set of outlets may be located, for example, between about 0.01 feet and 10 feet below the top of the sludge blanket depending on factors such as system size and desired product quality. After the sludge settles to the bottom of the SBR vessel 105, the slower rate settling biological flocs/solids will tend to be located in the upper portion of the sludge blanket 310 while the more quickly settling granular biological flocs will tend to be located in the lower portion of the sludge blanket 310. The sludge may be wasted/ discharged from the SBR vessel 105 primarily or exclusively through the second sludge waste outlet or set of outlets 300 to selectively waste the slower rate settling biological flocs/solids as compared to the more quickly settling granular biological flocs. The lower set of sludge waste outlets 190 may be utilized when it is desired to remove all sludge from the SBR vessel 105, for example, during maintenance. The utilization of the second sludge waste outlet or set of outlets 300 may be performed in combination with any of the other embodiments disclosed herein.

Prophetic Example:

An example application of this technology could be for construction of a new treatment system in a facility with limited space. A treatment system with a capacity of one million gallons per day might take 3,500 ft² of land for two SBR tanks using standard methods for SBR design at, for example, 3,000 mg/1 biomass concentration. With the utilization of granular sludge in the SBRs as disclosed herein, the area required for two SBR tanks may potentially be reduced by one half to 1,750 ft² due to the increased mixed liquor concentration treatment capability with granular sludge in the SBRs of 6,000 mg/1. In addition to reduced space, construction costs may also be reduced.

Alternatively, a reduction in effluent concentrations of nitrogen and phosphorus, which are harmful to lakes and rivers, may be desired to meet treatment goals. Application of this technology could be added to an existing SBR system. The increased settleabihty of the mixed liquor with granular sludge would result in an effluent with reduced concentration of certain chemicals such as nitrogen and phosphorus compared to the same SBR system operated without granular sludge. Some of the lighter floc that typically enters the effluent may be eliminated, reduced, or redirected as disclosed herein. Reducing total suspended solids (TSS) in the effluent results in reduction of nitrogen and phosphorus since most of the TSS is composed of single cell organisms which contain nitrogen and phosphorus in their cells.

The aspects disclosed herein in accordance with the present invention, are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. These aspects are capable of assuming other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, components, elements, and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiments.

Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. In addition, in the event of inconsistent usages of terms between this document and documents incorporated herein by reference, the term usage in the incorporated reference is supplementary to that of this document; for irreconcilable inconsistencies, the term usage in this document controls.

Having thus described several aspects of at least one example, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. For instance, examples disclosed herein may also be used in other contexts. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the examples discussed herein. Accordingly, the foregoing description and drawings are by way of example only.

Claims

What is claimed is: CLAIMS

1. A method of operating a sequencing batch reactor process comprising: introducing wastewater to be treated into the sequencing batch reactor; and selectively removing a portion of biological flocs from the wastewater in the sequencing batch reactor that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor.

2. The method of claim 1, wherein selectively removing the portion of biological flocs from the wastewater in the sequencing batch reactor includes removing effluent and the portion of biological flocs from the sequencing batch reactor during performance of a Settle stage of operation of the sequencing batch reactor.

3. The method of claim 2, wherein the effluent and the portion of biological flocs is removed from the sequencing batch reactor immediately after termination of a React stage of operation of the sequencing batch reactor.

4. The method of claim 2, wherein the effluent and the portion of biological flocs is removed from the sequencing batch reactor after a non-zero predetermined amount of time after termination of a React stage of operation of the sequencing batch reactor.

5. The method of claim 2, further comprising directing the effluent and the portion of biological flocs into a clarifier/equalization basin.

6. The method of claim 5, further comprising discharging solids settled in the clarifier/equalization basin and directing effluent from the clarifier/equalization basin from which the solids have settled to a disinfection operation.

7. The method of claim 2, further comprising: monitoring at least one of turbidity or total suspended solids in the effluent; directing the effluent and the portion of biological flocs into one of a solids/liquid separation subsystem or a digester if the one of the turbidity or the total suspended solids in the effluent is above a desired level; and directing the effluent and the portion of biological flocs into a tertiary disinfection subsystem if the one of the turbidity or the total suspended solids in the effluent is below the desired level.

8. The method of claim 2, further comprising directing the effluent and the portion of biological flocs into one of a filter or a ballasted solids/liquid separation system.

9 The method of claim 1, wherein selectively removing the portion of biological flocs from the wastewater in the sequencing batch reactor includes removing settled solids from an upper portion of a sludge blanket formed in the sequencing batch reactor during a Settle stage of operation of the sequencing batch reactor.

10. A wastewater treatment system comprising a sequencing batch reactor including a vessel for receiving a wastewater for treatment and a controller configured to operate the sequencing batch reactor to selectively remove a portion of biological flocs from the wastewater in the sequencing batch reactor vessel that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor vessel.

11. The system of claim 10, wherein the sequencing batch reactor further includes a decanter and the controller is configured to cause effluent and the portion of biological flocs to be removed from the sequencing batch reactor vessel through the decanter during a Settle stage of operation of the sequencing batch reactor.

12. The system of claim 11, further comprising a clarifier/equalization basin having an mlet configured to receive the effluent and the portion of biological flocs from the decanter and configured to settle the portion of biological flocs from the effluent.

13. The system of claim 12, wherein the inlet of the clarifier/equalization basin includes one or more influent distribution manifolds.

14. The system of claim 12, wherein the effluent and the portion of biological flocs are fed into a flocculating energy dissipating well arrangement at the inlet of the clarifier/equalization basin.

15. The system of claim 11, further comprising at least one of a TSS monitor or a turbidimeter disposed on an effluent conduit of the sequencing batch reactor.

16. The system of claim 15, wherein the controller is configured to selectively direct the effluent and the portion of biological flocs to a solids/liquid separation unit operation or to bypass the solids/liquid separation unit operation based on a reading from the one of the TSS monitor or turbidimeter.

17. The system of claim 16, further comprising a disinfection subsystem, the controller configured to direct effluent that bypasses the solids/liquid separation unit operation into the disinfection subsystem.

18. The system of claim 10, further comprising one of a tertiary filter or a ballasted solids/liquid separation system, the controller configured to direct the effluent and the portion of biological flocs into the one of the tertiary filter or ballasted solids/liquid separation system.

19. The system of claim 10, further comprising a first set of sludge waste outlets disposed at a bottom of the vessel and a second set of sludge waste outlets disposed at a location above the bottom of the vessel.

20. The system of claim 19, wherein the controller is configured to cause sludge to be discharged from the vessel primarily through the second set of sludge waste outlets.

21. A method of retrofitting a sequencing batch reactor, the method comprising programming a controller of the sequencing batch reactor to operate the sequencing batch reactor to selectively remove a portion of biological flocs from wastewater in the sequencing batch reactor that settles at a slower rate than another portion of biological flocs in the sequencing batch reactor.

22. The method of claim 21, further comprising mounting at least one of a TSS monitor or a turbidimeter on an effluent conduit of the sequencing batch reactor.

23. The method of claim 22, further comprising programming the controller to selectively direct the effluent and the portion of biological flocs to a solids/liquid separation unit operation or to bypass the solids/liquid separation unit operation based on a level of TSS or turbidity in the effluent and the portion of biological flocs.