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CA-3109511-C - BIOMASS SELECTION AND CONTROL FOR CONTINUOUS FLOW GRANULAR/FLOCCULENT ACTIVATED SLUDGE PROCESSES

CA3109511CCA 3109511 CCA3109511 CCA 3109511CCA-3109511-C

Abstract

A continuous flow granular/flocculent sludge wastewater process selects for granule biomass capable of nitrogen and phosphorus removal and controls granule size and concentration of granular and flocculent sludge for optimal nutrient, organic, and solids removal in a smaller footprint. It includes anaerobic, anoxic, and aerobic process zones, a high soluble biodegradable COD loaded first reactor in anaerobic or anoxic zones, a granular sludge classifier with recycle of underflow granular sludge to the first reactor, a secondary clarifier to settle flocculent sludge and particulates and recycle of flocculent sludge from the secondary clarifier underflow to an aerobic process zone. Wasting of sludge from the two separate recycle lines controls the bioprocess flocculent and granular sludge concentrations and CRTs. Bypass around and recycle flow to the classifier to maintain desired flow under various influent flow conditions aid control of granule size. On/off mixer operation of anaerobic and anoxic reactors may be used.

Inventors

  • H. David Stensel
  • Hiren Trivedi
  • John Vorwaller
  • Tyson Beaman

Assignees

  • OVIVO INC.

Dates

Publication Date
20260505
Application Date
20190809
Priority Date
20180813

Claims (20)

  1. WE CLAIM: 1. A wastewater treatment system for biological treatment of wastewater including organic sewage, the system including a liquid process configuration for removal of at least nitrogen and for concentrating biomass, in a continuous flow process, comprising: a plurality of process zones, including a first process zone receiving influent wastewater in continuous flow and mixing the influent wastewater with biomass to produce a mixed liquor in the first process zone, and including bacteria in the first process zone effective to produce granular biomass as well as flocculent biomass, the first process zone being anaerobic or anoxic to encourage formation of granular biomass, the plurality of process zones including at least a second process zone receiving mixed liquor in continuous flow from the first process zone, including granular biomass and flocculent biomass, one of the plurality of process zones being an aerobic zone, a biomass classifier downstream of the process zones, receiving mixed liquor with granular and flocculent biomass, the classifier having separation means for separating out most of the granular biomass from the mixed liquor, so that the classifier produces a first effluent with predominantly flocculent biomass and a second effluent with predominantly granular biomass, a gravity settling clarifier downstream of the classifier 41 Date Re9ue/Date Received 2024-04-07 and receiving said first effluent from the classifier, the clarifier having a bottom where settled sludge is collected and can be discharged, a first recycle means carrying said second effluent from the classifier back to the first process zone, while at least periodically wasting a portion of the second effluent, a second recycle for moving a major portion of settled sludge collected in the clarifier bottom to the aerobic process zone, while a waste outlet of the clarifier at least periodically wastes another portion of the settled sludge from the bottom of clarifier, flow balancing means for adjusting flow into the classifier to allow for variations in influent flow rate into the system when influent flow is below a desired range, either by recycling a selected portion of said first effluent from downstream of the classifier to upstream of the classifier or by increasing flow at said second recycle, and a bypass line for moving a selected portion of biomass from the process zones in a bypass around the classifier, in an amount to allow for variations in influent flow rate to the system above the desired range.
  2. 2. The wastewater treatment system of claim 1, wherein the plurality of process zones includes at least one anaerobic process zone, and wherein the second recycle delivers a further portion of settled sludge from the clarifier bottom to said at least one anaerobic process zone. 42 Date Re9ue/Date Received 2024-04-07
  3. 3. The wastewater treatment system of claim 1, wherein the biomass classifier includes an energy dissipating inlet directing said mixed liquor into the classifier, the mixed liquor flowing into and through the classifier at a generally consistent flow rate, such that mostly granular biomass, having a greater density than floe biomass, settles and collects at the bottom of the classifier to be discharged as said second effluent, while floe biomass exits the classifier near an upper end of the classifier as said first effluent.
  4. 4. The wastewater treatment system of claim 1, wherein the classifier has a wasting outlet connected to a bottom of the classifier, so that wasting of settled sludge at both the clarifier and the classifier can be adjusted to provide desired proportions of granular sludge and of floe sludge in the process zones.
  5. 5. The wastewater treatment system of claim 1, wherein said first process zone is an anaerobic zone and the process zones including said aerobic zone located downstream of the anaerobic zone, and wherein primarily granular sludge from said second effluent of the classifier is recycled in said first recycle to the anaerobic zone, while primarily floe sludge from the clarifier is recycled in said second recycle to the aerobic zone. 43 Date Re9ue/Date Received 2024-04-07
  6. 6. The wastewater treatment system of claim 1, wherein the process zones include an anaerobic zone, an anoxic zone downstream of the anaerobic zone, and said aerobic zone located downstream of the anoxic zone.
  7. 7. The wastewater treatment system of claim 1, wherein the first process zone is an anoxic zone, and wherein primarily granular sludge from the classifier is recycled to the anoxic zone, while primarily floe sludge from the clarifier is recycled to the aerobic zone.
  8. 8. The wastewater treatment system of claim 1, wherein the flow balancing means comprises means for recycling a selected portion of said first effluent from downstream of the classifier to upstream of the classifier.
  9. 9. The wastewater treatment system of claim 1, wherein the first process zone is receiving influent wastewater at a soluble bCOD loading rate of at least 4.8 g/L/day.
  10. 10. The wastewater treatment system of claim 1, wherein the mixed liquor in the first process zone has a flocculent biomass concentration in the range of 500 to 2,000 mg/L.
  11. 11. The wastewater treatment system of claim 1, wherein the mixed liquor in the first process zone has a granular biomass concentration in the range of 2,000 to 12,000 mg/L. 44 Date Re9ue/Date Received 2024-04-07
  12. 12. The wastewater treatment system of claim 15, wherein the mixed liquor in the first process zone has a granular biomass concentration in the range of about 3,000 to about 9,000 mg/L.
  13. 13. The wastewater treatment system of claim 1, wherein the granular biomass in the process zones is at a granule size in the range of about 0.2 to about 4.0 mm.
  14. 14. The wastewater treatment system of claim 1, wherein mixed liquor flow through the biomass classifier is at a rate greater than 1 meter per hour.
  15. 15. The wastewater treatment system of claim 14, wherein mixed liquor flow through the biomass classifier is at a velocity in the range of 5 to 20 meters per hour.
  16. 16. The wastewater treatment system of claim 1, wherein granular biomass concentration in the first process zone is two to three times floe biomass concentration.
  17. 17. A biological wastewater treatment system with a series of process zones for processing a waste stream, and including a classifier for separating granular sludge from flocculent sludge, comprising: a tank or vessel, having an infeed of biomass sludge to the tank including both granular and flocculent sludge, an energy dissipating inlet (EDI) in the tank and receiving the infeed and dispersing it into the tank at a Date Re9ue/Date Received 2024-04-07 reduced velocity, the tank having a bottom and having an effluent outflow near the top of the tank, causing a flow pattern in the tank ultimately upwardly toward the outflow, such that the upward flow carries primarily floe biomass of less density than granular biomass to the outflow, while primarily granular biomass, with higher density than the floe biomass, settles toward the bottom of the tank to accumulate on the bottom of the tank, and at the bottom of the tank, a bottom outflow for removal or recycle of granular biomass, whereby a majority of biomass at the bottom outflow of the tank is granular biomass, and a majority of biomass effluent exiting the outflow near top of the tank is floe biomass.
  18. 18. The system of claim 17, wherein the energy dissipating inlet is submerged, positioned within 30% of the tank height from center.
  19. 19. The system of claim 17, wherein the energy dissipating inlet is submerged deeply in the tank, approximately 1/3 to approximately 2/3 down through the depth of the tank, and configured to direct a current of sludge outwardly and upwardly from the energy dissipating outlet. 46 Date Re9ue/Date Received 2024-04-07
  20. 20. The system of claim 17, wherein the energy dissipating inlet comprises a generally circular body with a top having a sludge inlet leading to an interior of the body, a bottom defining a lower boundary of the body, and a series of vertically extending baffle plates extending between the bottom and top of the body to disperse sludge and establish a generally even distribution of sludge entering the tank.

Description

WO 2020/036832 PCT/0S2019/046037 BIOMASS SELECTION AND CONTROL FOR CONTINUOUS FLOW GRANULAR/FLOCCULENT ACTIVATED SLUDGE PROCESSES S P E C I F I C A T I O N Background of the Invention This application claims benefit of provisional application No. 62/718,313, filed August 13, 2018. The application involves reactor process configurations 5 and a granular sludge classifier process to control granular sludge size and relative fractions of granular and flocculent activated sludge in a combined continuous flow wastewater treatment system for biological nutrient removal. The activated sludge process has been used since the 10 early 1900s for the treatment of domestic and industrial wastewater by microorganisms. The basic features of the traditional process are 1) mixing and aeration of the wastewater in a reactor with a flocculent mass containing active microorganisms and influent particulates, 2) a 15 liquid/solids separation step to separate and discharge the treated effluent from the flocculent mass, 3) wasting of excess mass produced from removal of wastewater particulates and biomass growth from the removal of influent substances, 4) return of settled flocculent mass from an external 20 liquid/solids separation step to the bioreactor or use of the 1 WO 2020/036832 PCT/0S2019/046037 settled flocculent mass in the bioreactor for continuous or batch treatment of wastewater. The process was first developed as a batch treatment process in which the above steps of biological contact, 5 liquid/solids separation, and flocculent mass return are done in a single tank. Continuous flow versions of the process followed soon after and are the most common version used today. Continuous flow activated sludge treatment involves single or multiple bioreactors used in series and an external 10 liquid-solids separation step with recycle of the solids to the bioreactors. The process may involve the use of configurations with anaerobic, anoxic, and aerobic zones to meet treatment objectives. Gravity settling of solids in a clarifier is the most common liquid-solids separation method. 15 The clarifier also provides high removal efficiency of suspended solids to produce a relatively clear effluent low in suspended solids. Due to excess sludge production, a waste solids stream routinely removes solids from the system to control the bioreactor mixed liquor suspended solids (MLSS) 20 concentration. The traditional activated sludge process has a flocculent biomass that in addition to consuming waste provides capture of particulate and fine solids to produce an effluent from the liquid/solids separation process that is low total suspended 25 solids (TSS). The flocculent biomass has a very diffused structure and a floe size commonly from 0.05-0.30 mm (Figure 1). Flocculent biomass is created by production of extracellular polymeric substances during biomass growth which binds other bacteria and also traps and contains colloidal and 30 suspended particulates from the influent wastewater. Biomass growth in aerobic activated sludge processes is the result of assimilation and oxidation of influent organic substrate with a suitable electron acceptor such as oxygen, nitrate, or 2 WO 2020/036832 PCT/0S2019/046037 nitrite. Biomass growth can also occur from oxidation of inorganic substrates such as ammonia, nitrite, reduced sulfur compounds, and reduced iron with a suitable electron acceptor. For the latter, the carbon needed for biomass growth is 5 derived from carbon dioxide. The wastewater organic concentration is commonly measured in a batch bioassay using bacteria and is referred to as the BOD or biochemical oxygen demand concentration. Treatment discharge standards require that the effluent BOD is below 10 some specified value, typically~ 20 mg/L. The effluent BOD consists of soluble organic biodegradable substrate and biodegradable colloidal and particulate solids. Treatment discharge standards also require a low effluent total suspended solids (TSS) with values typically~ 20 mg/L. More 15 stringent treatment requirements are often required with effluent BOD and TSS concentrations~ 10 mg/L. The physical characteristics of flocculent activated sludge is effective in capturing free bacteria, and nondegraded colloidal and particulate solids to meet permit limits for effluent TSS. 20 Different process tank configurations or batch treatment operation modes are also used in activated sludge processes to provide biological nitrogen removal and/or enhanced biological phosphorus removal (EBPR) to achieve low effluent concentrations of phosphorus and nitrogen (Tchobanoglous et 25 al., 2014). Effluent nitrogen soluble inorganic species are ammonia (NH3), nitrate (NO3), and nitrite (NO2). The activated sludge processes are designed with special configurations, including anaerobic, anoxic, and aerobic zones and operational methods to select for bacteria with specialized metabolic 30 capability important for nutrient removal. These processes include nit