Method and apparatus for activated sludge compaction

Abstract

A method and apparatus for treating wastewater using a sequencing batch reactor in which biological solids are compacted by hydraulic and organic selective pressure. Wastewater is introduced into the reactor under anaerobic conditions near the end of a treatment cycle after a draw-off step and before the start of the next treatment cycle. A floating sludge draw-off device is used in conjunction with a floating surface mixer to selectively remove lighter flocculated solids and retain denser solids by temporarily reducing mixing energy during the discharge treatment.

Description

Technical Field

[0001] This invention relates to the biological treatment of wastewater containing organic matter and nutrients. More specifically, the invention provides techniques to improve the sequencing batch reactor (SBR) activated sludge process, thereby gradually forming a denser biological solid mass, which in particular improves the settling rate and provides higher treatment capacity per unit volume. Background Technology

[0002] The activated sludge process, developed over 100 years ago by Edward Arden and William Lockett, has been one of the most widely used wastewater treatment technologies. This treatment cultivates diverse populations of bacteria, protozoa, and microorganisms to promote the reduction of organic matter and the removal of various forms of nitrogen and phosphorus. Control of the biological environment often involves managing anaerobic, anoxic, and aerobic conditions to target specific pollutants or to redirect bacterial populations towards beneficial organisms and away from those that impair settling, hinder performance efficiency, or cause other operational problems. Aeration, anoxic, and anaerobic reactions can be carried out in dedicated tanks or in the same tank at different times of the day. This technology produces many byproducts, but most rely on gravity settling to separate the bacteria from the treated water before discharge.

[0003] The settling capacity of a system is typically measured using sludge volume settling (SSV), which is determined by recording the settling volume of sludge in a one-liter graduated cylinder after a specific time period. Typical sludge will settle to approximately 200 to 400 milliliters (mL) in a one-liter container after a 30-minute period. This settling rate will depend on the mass of solids present in the system, and SSV is usually measured in milliliters of settled sludge per liter of liquid (mL / L). A common value for gravity-dependent activated sludge plants is 2 to 4 grams of mixed liquor suspended solids (MLSS) per liter (L) of reactor volume. While maintaining higher MLSS concentrations (e.g., 5 or 6 g / L) may provide greater treatment capacity, this is generally not feasible due to settling limitations. A metric used to measure both settling rate and solids mass is the sludge volume index (SVI). SVI characterizes sludge mass by determining the volume of sludge (in mL) occupied by 1 gram of activated sludge after 30 minutes of settling. As an example, a well-functioning activated sludge plant, if observed to have an SSV of 300 mL / L and maintained at 3 g / L MLSS, will successfully operate with an SVI of 100 mL / g. In fact, the typical 30-minute SVI range expected for normal activated sludge is between 100 and 200 mL / g.

[0004] Treatment plants often encounter settling problems due to factors such as influent wastewater quality or flow conditions, equipment malfunctions, or improper operating parameters. In cases of poor settling, operators may observe a SVI of 250 mL / g at 3 g / L MLSS. In such situations, operators may notice that the sludge settles to only 750 mL in a 1-liter container. More importantly, they may also notice that the sludge layer height in the clarifier is approaching the effluent weir, or that the effluent quality contains suspended solids exceeding permissible limits. Sludge settling characteristics remain a critical operating parameter throughout the entire operation of the activated sludge process.

[0005] Recently, there has been increasing interest in sludge compaction. By increasing the specific gravity of MLSS (Mixed Flour Sulfate), sludge settles faster and achieves higher settling concentrations, typically targeting 60 to 80 mL / g 30-minute SVI (Sequencing Volume Index). An extreme example of sludge compaction is the Nereda® process, invented by Delft University of Technology and commercially developed by Royal Haskoning DHV. This technology employs a sequencing batch reactor (SBR) configuration to facilitate specific process conditions that cause activated sludge to gradually form a rapidly settling, tightly packed, spherical structure. The resulting particles can be described as microbial-based aggregates, forming in a layered particle morphology without the need for additional weighting materials and without agglomeration under reduced hydraulic shear. Particle sizes formed entirely during the process range from 0.2 mm to over 4.0 mm, with settling rates 8 to 10 times faster than conventional activated sludge. This process improvement, known as aerobic granular sludge (AGS), produces biomass in which granules comprise 70% to 80% or more of the total system mass, with the remainder consisting of a dense to lightweight flocculent sludge mixture. The tightly packed granules exhibit a sedimentation volume (SVI) of 30 to 60 mL / g at MLSS levels as high as 8 to 10 g / L. Therefore, the Nereda variant of activated sludge does indeed allow MLSS concentrations to reach 2 to 3 times that of conventional activated sludge, while exhibiting faster and more consistent settling characteristics. Currently, the Nereda process represents the only full-scale AGS technology with installation experience. With over 100 plants under design, construction, or operation, the Nereda process is one of the fastest-growing wastewater treatment technologies. However, it may not be ideally suited to every plant. In fact, many existing facilities are seeking incremental improvements to their existing settling or treatment capacity rather than the 2 to 3 times increase offered by the Nereda technology.

[0006] There has been considerable interest in densification methods, which offer modest benefits to existing treatment facilities by improving system settling performance. These technologies can increase the SVI (Sediment Viscosity Index) of a wastewater treatment plant by 20% to 40%, while allowing for a similar increase in MLSS (Mixed Surface Suspension) concentration. A common technique for densifying MLSS is the selective discharge of lighter, less dense flocculent sludge while retaining faster-settling, denser flocculent sludge. For example, selective discharge can reduce a plant's SVI from 100 mL / g to 60 mL / g while increasing its MLSS from 3 or 4 g / L to 5 g / L or higher. In some systems that also employ biological nutrient removal, this selective discharge technique may actually promote the formation of small particles (greater than 0.2 mm), although these particles constitute only a small fraction of the total biomass. While it may not achieve the enhanced biomass characteristics exhibited by the Nereda process, process, mechanical, and electrical adjustments may be sufficient to meet the performance requirements of WWTP (Wastewater Treatment Plant). Selective discharge can be achieved through various gravity devices, such as hydrocyclones, phase separators, elevated sludge extraction pipes, and high-speed settling tanks.

[0007] Selective removal of lighter, flocculent sludge can increase the overall density of activated sludge MLSS without leading to the formation of aerobic granular sludge. Gradual granulation requires a complex and specific set of process conditions, and selective removal is only one contributing mechanism. Another important mechanism involves developing saturated-starved organic loading conditions, where a saturated period reflects a high food-to-mass (F / M) ratio, followed by a subsequent low F / M starvation period. Furthermore, high F / M periods are typically arranged under anaerobic conditions, where dissolved oxygen (DO) is absent and oxidized nitrogen, such as nitrates (NO3) and nitrites (NO2), is low. Anaerobic conditions and high F / M selectively favor the gradual formation of slower-growing biofilms, which are important for granular structure formation. Some bacteria are able to decompose more complex influent substrates under anaerobic conditions. In the absence of free DO as an electron acceptor, bacteria will extract energy from carbohydrates through enzymatic action using fermentation as an alternative metabolic pathway. The result of fermentation is readily degradable organic matter such as acetic acid, propionic acid, and butyric acid. These sludge fermentation products are collectively referred to as volatile fatty acids (VFAs). Organisms responsible for producing high-density biomass, such as phosphate-accumulating organisms (PAOs) or glycogen-accumulating organisms (GAOs), grow slowly and are less competitive in decomposing readily biodegradable organic matter in aerobic environments. The availability of VFAs under anaerobic conditions allows PAOs and GAOs to convert readily biodegradable organic matter into slowly degradable storage polymers. During this process, phosphate is released, leading to an increase in reactor concentration. However, aerobic treatment following the anaerobic period allows PAOs and GAOs to synthesize storage products in a higher-energy environment, where oxygen serves as the final electron acceptor. As a result, phosphate is rapidly absorbed by PAOs, achieving enhanced biological phosphorus removal. Furthermore, enzymatic reactions occurring in the saturated-anaerobic and starvation-aerobic sequences release specific extracellular polymers (EPS), which contribute to the gradual formation of high-density biomass. Therefore, developing anaerobic feed reactors combined with selective discharge is crucial for the gradual formation of dense biosolids. Similarly, this combination does not necessarily guarantee the gradual formation of completely granular sludge, although some particles may be present.

[0008] Several methods exist for densifying activated sludge. Moving bed bioreactors (MBBRs) use synthetic or natural weighting materials to support biofilm growth and increase the overall biomass level in existing activated sludge systems. Membrane bioreactors (MBRs) use microfiltration or ultrafiltration membranes to retain biological solids and discharge particulate-free effluent. While MBRs can handle MLSS levels up to 8 to 10 g / L without gravity settling, the membranes require additional tanks, energy, and operation and maintenance. Aerated membrane bioreactors (MABRs) use membranes to deliver oxygen to the biofilm to enhance reactor capacity, but rely on a separate solid-liquid separation unit.

[0009] SBR (Sequencing Batch Reactor) technology is one of the most successful activated sludge derivatives due to its ability to achieve biological treatment, settling, and clarification in a single unit. Furthermore, proper design of equipment, tank capacity, and controls allows for time-managed operation of anaerobic, anoxic, and aerobic phases to facilitate biological nutrient removal (BNR). SBR processes can be designed as a single tank, but are most commonly divided into two, three, four, or more smaller tanks. By using multiple reactors, SBR systems can provide continuous treatment of the flow while simultaneously offering batch treatment within individual reactors. With its ability to achieve all treatment objectives in a single tank, SBR configurations offer the highest treatment capacity per unit area among all activated sludge treatments. A preferred example of an SBR is AquaSBR®, first introduced to the wastewater treatment market by Aqua-Aerobic Systems in 1986, which features independent mixing and aeration to support anaerobic, anoxic, and aerobic treatment. Today, SBR technology is deployed in thousands of WWTPs and remains one of the most frequently chosen technologies due to its ability to effectively achieve total nitrogen levels as low as 3 mg / L and biological phosphorus levels below 1 mg / L. Some SBR systems operate as quasi-batch processes, where influent is received during settling and decanting steps. For true batch SBR systems that interrupt flow during the settling and decanting phases, the process can support slightly higher MLSS levels than conventional activated sludge systems. Despite this advantage, SBR processes can still benefit from compaction methods and systems to improve SVI and further increase MLSS concentrations. This invention modifies known physical and biological selection mechanisms to suit true batch SBR systems to promote the gradual formation of compacted biomass, thereby improving settling and increasing MLSS levels to increase treatment capacity per unit area. Summary of the Invention

[0010] This invention retains the advantages of known sequencing batch reactor systems and methods, and also provides new features and advantages.

[0011] This invention provides a method and apparatus for increasing biosolid density in a sequencing batch reactor (SBR) wastewater treatment system through physical and biological selection mechanisms to improve biosolid settling and reaction rates. The invention reconfigures the treatment cycle to promote saturated (high F / M) conditions in an anaerobic environment, followed by starvation (low F / M) conditions in an aerobic environment, favoring PAO growth and promoting higher biomass density. The invention also provides a method for selectively removing or discharging slower-settling biomass while retaining faster-settling, higher-density material.

[0012] This invention provides a floating sludge collection manifold combined with a floating downflow agitator assembly for densifying sludge in a tank or reactor. The system includes a downflow agitator assembly mounted on an annular float, the agitator assembly including a downwardly projecting discharge volute with a fluid inlet at its upper end and a propeller and outlet at its lower end. It also includes an agitator assembly frame attached to the upper side of the annular float, and multiple manifold support brackets having an upper end attached to the agitator assembly frame and a downwardly projecting lower end. A solid manifold, including multiple orifices, is attached to the lower end of the manifold support brackets around the outer periphery of the annular float. Multiple suction hoses are attached to and in fluid communication with the solid manifold, and a suction source is in communication with the suction hoses, wherein suction is applied to the suction hoses to cause less dense, flocculent sludge to pass through the solid manifold, the suction hoses, and then be removed from the reactor.

[0013] Those skilled in the art will understand that a float separate from the agitator float can be provided for the floating sludge collection manifold assembly. In this alternative embodiment, the solid manifold will be anchored to the float in a manner similar to that of a shared float. Methods for the removal or discharge of lightweight, flocculent sludge will be applicable. In yet another alternative embodiment, the sludge collection manifold assembly can be molded into the float structure.

[0014] The present invention also provides a method for treating wastewater and compacted sludge in a sequencing batch reactor, comprising the steps of: feeding influent substrate into the reactor, which contacts sludge particles containing microorganisms; providing oxygen to the sludge particles and agitating the reactor contents to distribute the liquid and sludge substrate material; and allowing heavier sludge to settle to the bottom of the reactor and decanting the top of the fluid to discharge treated effluent.

[0015] The preferred method further includes: performing a first anaerobic feed, wherein the influent substrate contacts the settled sludge particles; performing a second anaerobic agitation stage to further reduce the substrate; performing a third aeration reaction stage, wherein oxygen is delivered to the sludge particles in a fluidized state; at some point during the third aeration reaction stage, removing slowly settling sludge particles from the reactor using a sludge collection manifold and reduced agitation energy; performing a fourth stage, wherein the compacted sludge particles settle under static conditions, forming the upper region of the treated water; performing a fifth stage, wherein the clarified and treated water is decanted and discharged without introducing influent substrate; and performing a sixth stage, wherein the second anaerobic feed step delivers the influent substrate to the settled sludge particles. This effectively removes lighter, flocculent solids while retaining denser sludge at the bottom of the reactor.

[0016] The apparatus of this invention includes a floating sludge collection manifold assembly used in conjunction with a mixing device to selectively discharge lighter biosolids. This invention utilizes a typical floating high-speed axial-flow agitator that generates a high-speed jet directed to the bottom of the reactor (tank) and subsequently produces a flow vector toward the reactor walls. The mixed flow turns vertically upward upon impact with the walls until it reaches the reactor surface, where it turns again back to the mixing device for re-mixing. With sufficient energy, the floating agitator achieves homogeneity of biosolids, both light and heavy, throughout the tank. In a preferred method, the mixing energy is temporarily reduced during the aeration phase to allow the heavy, denser solids to settle, while maintaining sufficient energy to suspend the lighter, flocculent solids. During these low-energy conditions, the floating sludge collection manifold assembly removes the lighter solids from the tank, while leaving the denser solids in the reactor. The mixing energy is then increased after the solids discharge event to regain the non-homogeneity of the remaining denser solids within the reactor and promote an improved treatment reaction. The preferred apparatus according to the invention represents a significant improvement over the prior art because it can float with the variable water depth in the SBR, thereby providing consistent and predictable solids removal characteristics to simplify operation. The preferred method also allows for adjustments in time and energy to enable operational optimization, resulting in the desired biomass consistency. This improvement eliminates the need for a network of sludge collection pipes distributed throughout the tank to collect lighter, slower-settling materials. Instead, the flow pattern imparted by the floating agitator causes these lighter materials to be conveyed to a centrally located sludge collection manifold assembly.

[0017] According to a preferred method of the invention, a relative hydraulic loading rate is sensed and compared to the maximum design conditions to optimize the cycle structure by increasing substrate availability for the anaerobic treatment phase when the actual flow rate is below its peak design. A well-designed SBR system includes an effluent decanting system sized to discharge treated water within the maximum decanting time under peak flow conditions. Typically, the actual flow rate is below the peak design, and the time required to discharge effluent will be less than the programmed decanting phase time, resulting in a complementary idle phase equal to this time difference. The optional idle phase is important for maintaining equal total cycle times across multiple reactors to ensure proper treatment occurs in each reactor. While idle phases are beneficial for enabling SBR systems to respond aggressively to peak flow conditions, many SBR systems are designed to advance to the next cycle when the decanting reactor reaches a low operating level and do not include an idle phase. Furthermore, many of these systems are not designed with sufficient reactor depth to maintain the desired cycle time when flow rates exceed average conditions. Therefore, those systems not designed to handle peak flow rates without shortening treatment cycle times cannot benefit from the utility of modifying the idle phase to gain process advantages. This invention allows the introduction of influent substrate contained in the wastewater stream into the reactor during idle phases to promote effective anaerobic feed conditions required for the formation of a high-density microbial community. An influent distribution system is used to deliver the substrate to the high-density biomass to generate saturated (high F / M) conditions without stirring or aerating the reactor. The method according to the invention is an improvement over the prior art because it increases substrate availability during anaerobic treatment under most conditions, while preserving the full cycle time to cope with unexpected peak flow conditions.

[0018] Therefore, one object of the present invention is to provide a system and method for compacting sludge in a sequencing batch reactor.

[0019] Another object of the present invention includes a floating downflow agitator assembly and an associated floating sludge collection manifold assembly to remove lighter, slower-settling solids while retaining dense solids in the reactor.

[0020] Another object of the present invention is to provide a method that allows denser solids to settle and remain in the reactor while removing lighter, flocculent sludge.

[0021] Another object of the present invention is to provide a method for densifying sludge in a sequencing batch reactor by feeding substrate into the reactor, supplying oxygen to the contents, agitating the contents, allowing heavier sludge to settle, and decanting the upper part of the fluid for discharge.

[0022] Another object of the present invention is to provide a floating sludge collection manifold that removes lighter sludge by suction.

[0023] Another object of the present invention is to provide a method for temporarily reducing agitation to allow denser sludge to settle, while maintaining sufficient energy to suspend lighter flocculent solids for removal.

[0024] Another object of the present invention is to eliminate the need for a sludge collection pipe network throughout the reactor tank to collect lighter, slower-settling sludge.

[0025] Inventor's definition of terminology The following terms, which may be used in the claims and / or specification of this patent, are intended to have the broadest meaning consistent with their legal requirements: Settled sludge volume This refers to a measurement determined by recording the volume (in milliliters) of sludge in a graduated cylinder after a specified time period. A typical time period is 30 minutes.

[0026] Mixture suspended solids This refers to the concentration of suspended solids in the aeration tank of an activated sludge process during wastewater treatment. A common value for typical activated sludge plants that rely on gravity settling is 2-4 grams of mixed liquor suspended solids (g / L) per liter of reactor volume.

[0027] Volatile suspended solids in the mixture The biologically active portion of MLSS refers to the concentration of suspended solids in the activated sludge aeration tank during wastewater treatment. MLVSS concentration is typically about 75% of the MLSS concentration.

[0028] sludge volume index This refers to an indicator used to measure the settling characteristics of activated sludge. It is equivalent to the volume (in mL) occupied by 1 gram of activated sludge after a specified time period. A time period of 5 to 60 minutes is typically used; shorter time periods are used for denser sludge, and longer time periods are used for slower-setting, flocculent sludge.

[0029] Where alternative meanings may exist in the specification or claims, the broadest meaning consistent with the understanding of a person skilled in the art is intended to be used. All terms used in the claims are intended to be used in accordance with normal, customary, and industry-specific English usage. Attached Figure Description

[0030] The stated and unstated objects, features, and advantages of the invention (sometimes used in the singular, but not excluding the plural) will become apparent from the following description and drawings, wherein like reference numerals denote like elements in the various views, and in which: Figure 1 This is a graphical representation of a typical SBR cycle structure, showing the expected water level under maximum daily flow conditions with no idle phases; Figure 2It is a graphical representation of a typical SBR cycle structure, showing the expected water level changes under average daily flow conditions, and including the idle phase when there is no feed. Figure 3 This is a graphical representation of the improved SBR cycle structure, showing how the sludge compaction of the present invention is promoted by replacing the non-feed idle stage with the anaerobic feed stage. Figure 4 This is a cross-sectional view of a typical floating downflow agitator in a tank, showing the flow pattern generated by the agitator, as well as the typical inlet distribution system and aerator structure; Figure 5 This is a schematic diagram of a floating downflow agitator including the sludge collection manifold assembly of the present invention; Figure 6 This is a top view of a preferred embodiment of the floating downflow agitator and sludge collection manifold assembly of the present invention; Figure 7 This is a side perspective view of the floating agitator and sludge collection manifold assembly of the present invention; Figure 8 yes Figure 7 Another side perspective view of the floating agitator and sludge collection manifold assembly; Figure 9 This is a perspective view of an alternative embodiment of the present invention, wherein the sludge collection manifold assembly is molded into the floating structure. Detailed Implementation

[0031] The following description is of what is currently considered to be a preferred embodiment or best representative example of the claimed invention. Future and present alternatives and modifications to the embodiments and preferred embodiments are contemplated. Any alternatives or modifications that do not substantially alter the function, purpose, structure, or result are intended to be covered by the claims of this patent.

[0032] The system and method of the present invention will be described for a typical SBR with three reactors (tanks). Figure 1 This shows the typical cycle structure that may be expected at peak design flow (“PDF”) or maximum daily flow, or for now at high water level 25.

[0033] like Figure 1As shown, reactor 1 300 begins its treatment cycle at its low water level (LWL) 24, starting with the stirred feed (MF) stage 10. Influent wastewater is introduced into reactor 1 300 at the start of MF stage 10 and continues until the end of the reaction feed (RF) stage 12, at which point the reactor depth is at its high water level (HWL) 25 or maximum daily flow. As those skilled in the art will understand, using valves, the influent flow is then diverted to reactor 2, which is beginning its MF stage 10. This allows reactor 1 to proceed to the extended reaction stage (R) 14 without flow into the tank. Reactor 1 then proceeds to the settling stage (S) 16 to allow biosolids to settle to the bottom, at a position of 30% to 40% of the reactor 300 depth. The upper 60% to 70% of the liquid volume contains high-quality treated water, ready for discharge. As those skilled in the art will understand, at the end of the settling phase (S) 16, the mechanical decanter opens and lowers the water level to its original low water level (LWL) 24 operating conditions during the decanting phase (D) 18. In a classic SBR, excess biological solids are removed from the bottom of the tank within minutes of the end of the cycle. This operation is then repeated one to eight times per reactor per day. The number of cycles per day depends on the influent waste intensity and effluent target.

[0034] This example shows three tanks using the same periodic structure, but they are offset by 1 / 3 of the total cycle time. By offsetting the cycle, the flow can be received continuously, and in some cases, discharged continuously from the system. SBR systems can operate in any number of reactors, but the most common configuration is two, three, or four tanks. The cycle offset is typically set to 1 / n of the total cycle time, where n equals the number of tanks.

[0035] Figure 2 The same cycle structure is shown, but with an increased average design flow level (ADF), or for now, low water level 24 conditions, which are typically combined with the maximum monthly average design flow. In this case, the cycle duration and stage times are exactly the same as during PDF 25 conditions, but the reactor depth does not reach HWL at the end of the RF stage. As a result, the starting depth of decanting stage (D) 18 is lower than during PDF, thus requiring less time to reach LWL 24. The reactor does not terminate the cycle prematurely, but instead enters idle stage (I) 20 to allow its ancillary reactors to complete their feed. Therefore, idle stage (I) 20 simply extends decanting stage (D) 18 as needed to maintain a fixed cycle time.

[0036] The optional idle phase (I) 20 exists in a settling solids bed in a static environment pretreated by nutrient removal and settling for up to two hours under static conditions. It is well known that bacteria will continue to respire, with a typical endogenous respiration rate of 4–8 mg dissolved oxygen (DO) per gram of mixed liquor volatile suspended solids (MLVSS) per hour, where MLVSS refers to the organic or volatile portion of the MLSS. The previously treated and settling biomass typically contains 4–7 g MLVSS / L and exhibits an oxygen consumption rate (OUR) of approximately 30–40 mg DO / L / hour (0.5 to 0.7 mg / L / min) in the sludge layer at the bottom of the reactor. The reactor DO content is typically 0 to 2 mg / L before aeration and settling, depending on the specific operating settings. Therefore, if oxygen is present at the start of settling (S) phase 16, the dissolved oxygen contained in the sludge layer will be consumed within minutes (typically less than 5 minutes). If designed for nutrient removal, oxidized nitrogen compounds, including nitrates (NO3) and nitrites (NO2), will be at low levels (< 3-5 mg / L) at the start of settling stage 16. With no DO and low NO3 and NO2 levels, the sludge layer in settling stage 16 will approach anaerobic conditions within approximately 10 to 15 minutes after initiation. The oxidation-reduction potential (ORP) will be below -200 mV, and anaerobic fermentation will begin and persist throughout the remaining settling stage 16, decanting stage 18, and idle stage 20. If the system is not designed for nutrient removal, higher levels of NO3 and NO2 may be present, and the sludge will be considered anoxic, where free DO is absent, but bacteria can acquire bound oxygen via NO3 and NO2 molecules. Anoxic ORP is typically between 0 and -100 mV, but it decreases (improves) as denitrifying bacteria reduce NO3 and NO2 concentrations and form molecular nitrogen (N2). Because there are no soluble organic carbon substrates typically available in the influent feed, the denitrification process slows down in the settling 16, decanting 18, and idle 20 stages, and the total time available for anaerobic conditioning is reduced.

[0037] This invention recognizes that introducing organic substrates to the bottom of the settled sludge layer ( Figure 4 This selective feeding method can selectively promote the growth and gradual formation of heavier biosolids with higher density. This selective feeding results in a steeper substrate concentration gradient, and the preferred, denser sludge is exposed to the substrate for a longer period. Conversely, bacteria present in lighter sludge near the top of the sludge layer are at a disadvantage because the substrate concentration in this region of the reactor will be significantly reduced. This control over substrate availability will selectively reduce the gradual formation of lighter, flocculent sludge. Figure 3Key embodiments and objectives of the invention are illustrated. When the control system detects that LWL 24 has been reached during decanting stage 18, it terminates decanting 18 and closes the outlet valve. Alternatively, as follows... Figure 2 and Figure 3 In the idle phase 20 shown, the reactor inlet valve is opened while the inlet valve of the ancillary reactor is closed. This effectively creates an anaerobic feed (AF) phase 22 at the end of the cycle, replacing the static idle phase 20, and delivers substrate to the bottom of the reactor where the denser biological sludge has settled. The influent volume received during the anaerobic feed phase 22 will raise the water level in the reactor without significantly expanding the sludge layer. The substrate delivered to the reactor will be isolated to the bottom portion of the reactor, and the high F / M ratio is only available for denser sludge. By directing the influent substrate to the anaerobic feed phase 22, it also terminates the influent feed to the ancillary reactor in the reaction feed 12, thereby reducing substrate availability for flocculent sludge that might otherwise proliferate under the aerobic reaction feed 12 phase. This invention optimizes the desired saturation and starvation conditions and effectively selects for denser sludge while inhibiting the gradual formation of lighter flocculent sludge.

[0038] As mentioned above, Figure 3 A preferred cycle structure of the invention is shown, wherein influent is introduced only in the non-aeration, non-stirring phase. In this example, when reactor 1 decans the treated effluent to a low level 24, its influent valve opens, while the influent valve of reactor 3 closes, allowing it to enter reaction phase 14, where its reactor is aerated but not fed. As previously mentioned, the actual time required for decanting phase 18 will vary based on current flow conditions. Therefore, the available time for anaerobic feeding phase 22 at the end of the cycle may be insufficient to gradually establish a suitable substrate-biomass relationship, requiring additional time. In this invention, by replacing part or all of the previous stirred feeding phase 10, anaerobic feeding phase 22 can be extended to the beginning of the treatment cycle, such as... Figure 3 As shown. In some cases, it may be necessary to agitate the reactor contents by implementing a stirring feed stage 10 at the end of anaerobic feed stage 22 before aeration, to further reduce substrate levels before aerating the reactor via reaction stage 14. In cases where the plant's waste load is particularly high and more aeration is required, it may be necessary to aerate the reactor before the end of the planned feed period. To address this, a reaction feed stage 12 can be inserted before the unfeeded reaction stage 14 to avoid excessive anaerobic feed conditions. The control system will attempt to limit the aeration feed 22 (reaction feed 12) conditions as much as possible to control the growth of lighter flocculent sludge.

[0039] Physical selection is necessary to preferentially retain dense, large solids rather than lighter, flocculent solids. Physical selection utilizes the low settling velocities of poorly flocculated activated sludge and filamentous bacteria to capture and remove these solids during the initial settling phase. Conversely, denser biological solids with faster settling characteristics are retained in the system. Various techniques are used to separate high-density and low-density biological materials by gravity, including devices such as hydrocyclones, inclined plate settlers, phase separators, and elevated solids discharge manifolds.

[0040] Figure 4 A typical floating downflow agitator assembly 100 and its associated float 102 in a typical reactor tank 300 are shown. A typical inlet distribution system 302 is also shown, which may include conduit 304 and orifice 306 for conveying substrate to the system. A typical aeration system 400 is also shown, which may also include conduit 402 and orifice 404.

[0041] Figure 4 The diagram also shows a typical circulation 500 generated in the tank 300 during operation of the agitator 100. As shown, during the mixing pattern of operation, the agitator volute and its associated outlet 106 direct the jet 500 to the bottom (ground) 308 of the reactor 300, subsequently generating a flow vector 500 toward the reactor 300 wall 310. After impacting the wall, the flow 500 is then guided back to the agitator 100 for re-mixing and recirculation 502.

[0042] As described above, the present invention preferably uses the flow pattern generated by a high-speed axial-flow direct-drive agitator to select lightweight solids from denser biomass. Floating direct-drive agitator (DDM) 100 ( Figure 4A relatively small axial impeller is used to generate a high-speed jet discharge 500 of approximately 12 to 18 feet per second. When a large volume of liquid is introduced, the high-speed jet effectively entrains the bulk liquid in the flow direction. The preferred DDM 100 directs the turbulent jet discharge to flow vertically downward toward the container floor 308. Within a distance equivalent to approximately 10 to 100 impeller diameters, the entrained volume increases, resulting in a total flow rate many times greater than the actual pumped flow rate. The resulting entrained flow reflects off the container floor at a distance of less than 100 impeller diameters and is redirected horizontally toward boundary conditions, such as the vertical wall 310 or an opposing flow from another agitator. Upon reaching the boundary conditions, the flow is redirected vertically toward the container surface 502. The water surface represents another boundary and redirects the flow horizontally away from the vertical wall. The agitator 100 is located at the center of the tank, and the generated flow is directed to the agitator's suction inlet 107, which is adjacent to the high-speed impeller. The water is then recirculated within the tank to achieve complete suspension of dense and lighter biological solids. Due to the entrainment effect of the flow, only about 3% of the mixing reactor flow passes through the high-speed impeller. The remaining 97% of the hydraulic circulation occurs outside the impeller, and the velocity is significantly reduced, which helps to reduce floc shear.

[0043] The preferred floating downflow agitator 100 was first described by Aqua-Aerobic Systems in patent number 4,422,771 and has proven to be one of the most efficient agitation devices for biological solid suspension, particularly in activated sludge. A key component of efficient DDM agitation is the resulting circulation path 500 (see...). Figure 4 The DDM produces a uniform distribution of suspended solids from the surface to the ground 308, with sludge movement near the surface guided in a 360-degree direction toward the agitator 100. When the DDM agitator 100 is turned off, the recirculated energy remains in the reactor for several minutes (1 to 3 minutes) as the velocity gradually decreases. When this occurs, heavier solids will settle first, while lighter, less dense materials will require a longer settling time.

[0044] Figure 5 This diagram illustrates a preferred embodiment of the present invention, showing a method for selectively removing light, flocculent sludge from reactor 300 by reducing agitation energy. The invention includes a floating sludge collection manifold assembly 200 located near the agitator 100 and preferably six to twenty-four inches below the water surface (partially shown). Figure 5 The sludge collection manifold assembly 200 can be fixed to the float 102 of the agitator or supported by a separate buoyancy device. Solid removal can be accomplished by gravity using valves or by pumping the material out of the system.

[0045] The preferred sludge collection manifold assembly 200 of the present invention is shown in the figure. Figure 6-8The reactor 300 includes a typical downflow agitator assembly 100, which has an annular float 102 that supports the agitator on the surface of the fluid to be agitated. Due to the float 102, the agitator assembly 100 moves up and down depending on the water level in the reactor 300.

[0046] The agitator 100 includes a drive motor 104 mounted on a float 102. A discharge volute 106 extends downward from the motor 104. The upper end includes an intake port 107. The lower end 108 of the discharge volute 106 houses a propeller (not shown) and terminates at a discharge end 110.

[0047] In operation, due to the position of the propeller, the fluid to be stirred enters the inlet 107 and exits from the outlet 110 to achieve stirring in the pool or tank. The foregoing describes a typical downflow agitator 100 that can be used with or as part of this invention.

[0048] The preferred sludge collection manifold assembly 200 of the present invention can be Figure 6-8 As seen in the image, in addition to the typical downflow agitator 100, there is also an agitator assembly frame 202. Figure 6 It is shown as a square. Those skilled in the art will understand that the component frame 202 can take other shapes. The component frame 202 can be fixed to the top of the float 102.

[0049] Four manifold support brackets 204 are attached to the stirrer assembly frame 202 and project downwards. Attached to the lower end of the manifold support brackets 204, preferably and generally surrounding the outer periphery of the float 102, is a solid manifold 206. In a preferred embodiment, the solid manifold 206 is a tubular member having orifices 208.

[0050] Solid waste or suction hose 210 is in fluid communication with the solids manifold 206. When operated in the manner discussed herein, suction is applied to the suction hose 210, and certain types of desired solids are drawn into the solids manifold 206 through orifice 208 and removed via the suction hose 210.

[0051] This removes lighter solids while allowing denser biosolids to settle to the bottom of the reactor. Using a sludge collection manifold assembly removes less dense, flocculent sludge, shifting the biomass density characteristics towards the heavier sludge, thus causing it to compact. It also increases the reactor's processing capacity.

[0052] The foregoing description is not intended to limit the meaning or scope of the terms used to define the invention in the following claims. Rather, non-substantial changes in structure, function, or outcome are anticipated in the future, and all such non-substantial changes claimed in the claims are intended to be covered by the claims. Therefore, while preferred embodiments of the invention have been described and illustrated, it should be understood that changes and modifications can be made without departing from the claimed invention. Furthermore, although the terms “claimed invention” or “the present invention” are sometimes used herein in the singular, it should be understood that multiple inventions exist as described and claimed.

[0053] The various features of the present invention are set forth in the appended claims.

Claims

1. A floating sludge collection manifold, combined with a floating downflow agitator assembly, for densifying sludge in a tank or reactor, said floating sludge collection manifold comprising: A downflow agitator assembly is mounted to an annular float. The agitator assembly includes a downwardly projecting discharge volute, the upper end of which includes a fluid inlet, and the lower end of which includes a propeller and an outlet. A stirrer assembly frame is attached to the upper side of the annular float; Multiple manifold support brackets have an upper end attached to the stirrer assembly frame and a lower end protruding downwards; A solid manifold is attached to the lower end of the manifold support bracket around the outer periphery of the annular float, and the solid manifold includes multiple orifices; Multiple suction hoses are attached to and in fluid communication with the solid manifold; as well as A suction source, connected to the suction hose, wherein suction is applied to the suction hose to cause low-density flocculent sludge to pass through the solids manifold, the suction hose, and be removed from the reactor.

2. The floating sludge collection manifold according to claim 1, wherein, The solid manifold is molded into the floating structure.

3. A method for treating wastewater and compacting sludge in a sequencing batch reactor, the method comprising the following steps: The influent substrate is fed into the reactor and comes into contact with sludge particles containing microorganisms. Oxygen is supplied to the sludge particles; The contents of the stirred reactor are distributed liquid and sludge substrate materials; Heavier sludge is allowed to settle to the bottom of the reactor; Decant the upper part of the fluid for discharge; and This includes the following further steps: a) The first anaerobic feed is carried out, in which the influent substrate comes into contact with the settled sludge particles; b) Before aeration begins, a second anaerobic stirring stage is performed to further reduce substrate; c) The third aeration reaction stage is carried out, in which oxygen is delivered to the sludge particles in a fluidized state; d) The fourth stage is carried out, in which denser sludge particles settle under static conditions, creating an upper zone of treated water that is decanted and discharged without introducing influent substrate. e) The fifth stage is carried out, in which the clarified and treated water is decanted and discharged as treated effluent without introducing influent substrate; f) Proceeding to the sixth stage, in which the second anaerobic feed step conveys the influent substrate to the settled sludge particles; and, e) During the third aeration reaction stage, a sludge collection manifold assembly is used to remove slowly settling sludge particles from the reactor.

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