Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F7/00—Aeration of stretches of water
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2331—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2331—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements
  • B01F23/23311—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements through a hollow stirrer axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2333—Single stirrer-drive aerating units, e.g. with the stirrer-head pivoting around an horizontal axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2335—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the direction of introduction of the gas relative to the stirrer
  • B01F23/23354—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the direction of introduction of the gas relative to the stirrer the gas being driven away from the rotating stirrer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2336—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer
  • B01F23/23366—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer the gas being introduced in front of the stirrer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/237—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media
  • B01F23/2376—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media characterised by the gas being introduced
  • B01F23/23761—Aerating, i.e. introducing oxygen containing gas in liquids
  • B01F23/237612—Oxygen
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/02—Aerobic processes
  • C02F3/12—Activated sludge processes
  • C02F3/20—Activated sludge processes using diffusers
  • C02F3/205—Moving, e.g. rotary, diffusers; Stationary diffusers with moving, e.g. rotary, distributors
  • C02F3/207—Moving, e.g. rotary, diffusers; Stationary diffusers with moving, e.g. rotary, distributors with axial thrust propellers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/05—Stirrers
  • B01F27/07—Stirrers characterised by their mounting on the shaft
  • B01F27/072—Stirrers characterised by their mounting on the shaft characterised by the disposition of the stirrers with respect to the rotating axis
  • B01F27/0725—Stirrers characterised by their mounting on the shaft characterised by the disposition of the stirrers with respect to the rotating axis on the free end of the rotating axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/05—Stirrers
  • B01F27/11—Stirrers characterised by the configuration of the stirrers
  • B01F27/113—Propeller-shaped stirrers for producing an axial flow, e.g. shaped like a ship or aircraft propeller
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/60—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis
  • B01F27/61—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a horizontal or inclined axis about an inclined axis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• the invention relates broadly to the treatment of water by aeration.
• the aeration treatment of water has been ;used to treat waste water within lagoons and to upgrade the quality of natural bodies of water, such as lakes.
• Waste water treatment aeration systems generally utilize either diffused air aerators or mechanical aerators.
• a diffused air type aerator introduces air or pure oxygen into water via submerged forced diffusers or nozzles.
• Mechanical type aerators generally agitate the water so as to promote solution of air from the atmosphere into the water.
• These conventional aerators are designed primarily from the standpoint of introducing a certain amount of oxygen into the water being treated. The mixing of the water and the introduced oxygen has not been a design criteria and, hence, conventional prior aerator systems have inefficient mixing capabilities.
• Mechanical surface aerators also exhibit an additional problem in that they have separate and gener ⁇ ally conflicting mixing vectors. That is, the force vectors from the aerators cannot generally be managed or manipulated and, hence, with closely spaced aerators, mixing vectors tend to cancel out.
• the method in accordance with the present inven ⁇ tion overcomes the above deficiencies of conventional systems by both aerating a body of water and causing mixing of the aerated water at efficient power levels.
• the present invention relates to a method for treating water.
• the method comprises the steps of: aerating a bounded body of water with a plurality of propeller-type aerators, each aerator having a hollow tube with opposite ends, a longitudinal axis extending between the ends, and a propeller adjacent one of the ends placing each of the aerators in the bounded body of water with the propeller and tube end adjacent thereto below the top surface of the water and with the longitudinal axis of each aerator disposed at an angle below the hori ⁇ zontal; driving the aerators to create individual circulating flow patterns around each of the aerators; mixing the water by arranging the aerators in a disposition to link the individual flow patterns created by adjacent aerators to one another to form a larger closed overall flow pattern; injecting oxygen from ambient air through the tube into the body of water adjacent the propeller at a rate greater than 1 pound of oxygen per horsepower-hour; inducing by means of the propellers of the aerators the closed overall flow pattern at an average linear velocity
• the method of the present invention includes the steps of injecting oxygen at a rate greater than 2.0 pounds of oxygen per horse ⁇ power-hour; and of inducing the closed overall flow pat ⁇ tern at a linear velocity greater than 0.5 feet per second by driving the propellers of the aerators in the bounded body of water at less than 0.1 horsepower per thousand cubic feet of water in the bounded body of water.
• the injection of the oxygen and the inducement of the flow pattern at the above low horsepower rates results in efficient treatment of waste water and an efficient reduc- tion of effluent is biological oxygen demand (BOD). It is believed that the efficient treatment of waste water is due to the capability of both inducing the flow pattern to maintain solids in suspension and the injection of oxygen both at efficient power ratings.
• the overall flow pattern within a bounded body of water is attained by linking the circulating flow patterns of adjacent aerators together.
• a single ' series or set of aerators is arranged in a single closed overall path.
• a second set of aerators is arranged adjacent to the first set to create a second closed flow pattern within the body of water.
• a second set of aerators forms a closed flow pattern within the closed flow pattern formed by a first set of aerators.
• one or more aerators can be displaced out of the overall flow pattern toward the center of the overall flow pattern. This displacement of one or more aerators creates a sub-flow pattern to avoid a void flow area.
• a controlled and efficient waste water treatment system By injecting oxygen at a controlled rate and by simultaneously controlling the flow and flow patterns of the waste water, a controlled and efficient waste water treatment system can be maintained.
• the suspended solids levels in various lagoons and effluent may be manipulated with proper control of the mixing lagoon through a series system. Actually, any form of seasonal control discharge can be provided for suitable solids while maintaining a flow-through condition for the liquid.
• aeration is tapered down during the winter as temperatures fall. This is appropriate since less oxygen is required as the rate of exertion of oxygen demand declines with temperature and oxygen transfer efficiency is improved with increasing saturation values for dissolved oxygen.
• An additional benefit of this procedure is that solids are allowed preferentially to drop from suspension and the lagoon provides essentially for solids' storage and holding during winter operations. Solids then accumu ⁇ late as a thin aerobic sludge blanket for slow digestion through winter. As noted above, a reduced level of aera- tion may be provided during winter to assure that the lagoon surface remains at least partially open to the atmosphere or, at least, that aerobic conditions prevail throughout the water volume. Thin sludge layers held for an extended period under aerobic condition may be expecte to undergo composting and to waste away.
• FIGURE 1 is a side elevational view illustrating a single propeller-type aerator for use in the method of the present invention
• FIGURE 2a is a plan view diagrammatically illustrating the specific placement of a number of pro ⁇ peller-type aerators within a bounded body of water and the overall flow path induced by the aerators;
• FIGURE 2b is a plan view similar to FIGURE.2a illustrating the specific placement of propeller-type aerators within a different bounded body of water;
• FIGURE 3a is a diagram illustrating velocity measurements taken at various locations within the body of water illustrated in FIGURE 2a;
• FIGURE 3b is a diagram illustrating velocity measurements taken at various locations within the body of water illustrated in FIGURE 2b;
• y fi ⁇ yAZ FIGURE 4 is a diagrammatic plan view illus ⁇ trating individual horizontal circulating flow patterns induced by propeller-type' 'aerators and the linking of adjacent circulating flow patterns in accordance with the method of the present invention;
• FIGURE 5 is a diagrammatic plan view illus ⁇ trating another arrangement of propeller-type aerators and the resulting adjacent overall flow paths;
• FIGURE 6 is a diagrammatic plan view illus- trating an arrangement of propeller-type aerators in encircling overall paths wherein a subflow path is created by displacing a number of aerators out of the overall flow path;
• FIGURE 7 is a diagrammatic plan view illus- trating the placement of a plurality of propeller-type aerators in a single overall flow path wherein a number of aerators are displaced from alignment with the overall flow path to create a subflow path.
• FIG. 1 a propeller-type aerator 10 for use in the method of the present invention.
• the aerator 10 is shown dis ⁇ posed within a liquid 12, preferably water or waste water.
• the aerator 10 has an outer tubular housing 14 and an inner tube 16 rotatably carried within the outer tubular housing 14.
• the inner tube 16 extends within the tubular housing 14 to a level above the top surface of the liquid 12 and is drivingly coupled to a motor carried within a motor housing 18.
• the inner tube 16 has at least one hole at its upper end above the top level of the liquid 12 for admitting air into the interior of the tube 16.
• the inner tube 16 extends outwardly beyond the lower end of the tubular housing 14 and has a propeller 20 fixedly attached thereto.
• a diffusion tube 22 is also attached to the inner tube 16 and has a hollow interior which communicates with the hollow interior of the inner tube 16.
• the propeller 20 is also rotated. As the propeller 20
• O PI WIPO rotates, it causes a directional, turbulent flow field in the liquid 12.
• the reduced pressure zone created by this flow downstream of the propeller aspirates or draws air down the hollow tube 16 and causes air to enter the liquid through an open end of the diffusion tube 22 as air bubbles 24.
• the air bubbles 24 are thereafter dispersed by the turbulence caused by the propeller.
• the propeller-type aerator 10 aerates while it mixes.
• aerators 10 can be arranged to provide a directional flow with the aerators 10 installed to contribute additively to the uniform mixing patterns involving an entire bounded body of water. Liquid flow can thus be directed and circulation patterns can be developed to assure desire velocity vectors throughout an entire volume of a body of water being treated.
• the inner tube 16 has a longitudinal axis indi ⁇ cated by line 26.
• the aerator 10 is supported in the liquid 12 by a platform or boom 28.
• the aerator 10 is attached to the platform 28 in any conventional manner, such as by a bracket 30.
• the aerator 10 is supported in the liquid 12 such that the longitudinal axis 26 forms an angle with the horizontal between 15 and 25 degrees. Preferably the angle is set at 22 degrees. In this manner, the mixing energy caused by the rotating propeller tends to promote circulation and flow over a larger area than is typical of conventional turbine aerators. If the angle is increased past 25 degrees so that the tube 14 becomes more vertical, to some degree higher oxygen trans- fer is obtained at the expense of mixing.
• the method of the present invention finds its primary use in aerated lagoons or ponds used as a portion of an overall waste water treatment process.
• Aerated lagoons systems can be designed for three different levels of mixing. Levels of mixing are generally determined by the degree of pollution in the water or the BOD require- ment. For most waste water treatment lagoons receiving relatively dilute domestic wastes, the power required to satisfy oxygen demand through most of the year is markedly less than required to maintain solids in suspension. The lowest level of power input must transfer sufficient oxygen to satisfy demand exerted by the satisfaction of BOD in the waste. Aeration sufficient to transfer 0.7 to 1.4 pounds of oxygen per pound BOD exerted is typical.
• An intermediate level of power input must provide for uniform oxygen dispersion throughout a lagoon volume in addition to merely supplying a specified quantity of oxygen. Hence, additional power over that required to merely inject the oxygen is needed so that minimal circulation effects are created to ensure uniform distribution of oxygen throughout a lagoon volume. However, at such an intermediate level, sufficient turbulence is not created to maintain solids in suspension.
• the highest level of power input that would reasonably be necessary would provide for oxygen dispersion as well as minimum scouring velocities, such as 0.4 to 0.5 feet per second (fps).
• Prior art aeration systems have required at least 0.5
• the method of the present invention accomplishes both adequate oxygen injection into waste water and mixing of the aerated waste water at efficient power levels.
• the present invention permits management or control of oxygen injection and mixing velocities at efficient power levels under numerous water pollution conditions.
• the method includes the steps of providing a plurality of propeller-type aerators where each aerator has a hollow tube with opposite ends and a longitudinal axis extending between the ends and a propeller adjacent one of the ends.
• the aerator 10 is specially suited for the present method.
• the aerators are placed in a bounded body of water, such as a pond or a lagoon, with the propeller and tube end adjacent thereto below the top surface of the water and with a longitudinal axis of each aerator disposed at an angle below the horizontal.
• the water is mixed by arranging and driving the aerators in a disposition so that individual circulating flow patterns are created around each of the aerators and the individual flow patterns link to one another to form a larger closed overall flow pattern.
• the aerators are arranged such that when the propellers of the aerators are driven at sufficiently high speeds to inject ambient air into the water, individual flow patterns are created around each of the aerators and are linked together to form a larger closed overall flow pattern.
• FIG. 4 The individual flow patterns and the linking of adjacent individual flow patterns is illustrated in Figure 4.
• Three aerators 10a, 10b, 10c are illustrated diagram- matically in Figure 4.
• Horizontal flow vectors indicating a horizontal flow of the water are shown emanating about each of the aerators 10a, 10b, and 10c.
• a plurality of forward horizontal flow vectors 32 indicate a horizontal flow of fluid forward of the propeller of aerator 10a.
• Negative horizontal flow of vectors 34 indicate a hori- zontal flow of fluid which is drawn toward the propeller of operator 10a from the area rearward of the propeller.
• Horizontal flow vectors 36 indicate a diffuse horizontal flow of fluid bending backward from the forward flow indicated by vectors 32 and interconnecting or forming a portion of the flow indicated by negative vectors 34.
• numbered flow vectors are indicated about aerators 10b and 10c.
• the aerators 10a, 10b and 10c are arranged relative to one another so that at least some of the flow indicated by the negative flow vectors 34 of one of the aerators links with at least some of the forward flow vectors 32 of an adjacent aerator. In this manner, an overall horizontal flow is created in the general direction of the forward flow vectors 32
• OMPI Figures 2a and 2b illustrate a plurality of propeller-type aerators 10 supported on platforms or booms 28 within a-pair of waste water treatment lagoons in which studies of the present invention were made.
• Flow vectors or arrows 40, 38 indicate a closed overall horizontal flow pattern or path of the waste water.
• the outer set or circle of aerators 10 creates the overall flow pattern indicated by vectors 38.
• the overall flow pattern indi ⁇ cated by vectors 40 is created by an inner set or cicle of aerators 10.
• the overall flow pattern indicated by vectors 40 circulates within the overall flow pattern indicated by vectors 38.
• FIGs 2a and 2b diagrammatically represent a plan view of two lagoons or ponds that form a portion of a waste water treatment plant within which the present method was utilized.
• The. water treatment plant also included a primary sedimentation unit, a roughing filter and a clarifier followed by a pond or lagoon system having four ponds, which Figures 2a and 2b, respectively, illus- trate first and second ponds of the pond system.
• Each of these first two ponds has a surface area of approximately 3/4 of an acre and a water volume of approximately 275,000 cubic feet.
• the ponds are approximately 175 feet wide and 190 feet long.
• the pond of Figure 2a has a plurality of propeller-type aerators 10 installed with a total power of 36 hp.
• the pond represented by Figure 2b has a plurality of aerators 10 installed with a combined power of 20 hp.
• the booms 28 extend inwardly from approximately the middle of each side of each pond.
• Each of the outer aerators is disposed approximately 30 feet from a respective side wall and each of the inner aerators is disposed approximately 60 feet from a respective side wall.
• Figure 3a illustrates a profile or vertical section through the pond illustrated in Figure 2a along the 195 foot line passing between SE and NW.
• Figure 3b illustrates a similar profile or vertical section along
• Figures 3a and 3b specify the velocity measurements in feet per second (fps) taken at various depths within the ponds, along the cross section, when the aerators 10 were operating to create the overall flow patterns indicated by arrows 38, 40.
• the measured velo ⁇ cities in Figure 3a result in average linear velocity in a generally horizontal direction through the cross section of the first pond of 0.77 fps and the velocities measured in Figure 3b result in average linear velocity in a gener- ally horizontal direction through a cross section of the second pond of 0.58 fps.
• These calculated average pond velocities are also the average velocity of the closed overall flow pattern in the ponds.
• the average pond velocity of 0.77 fps is ' attained, utilizing 0.13 hp per 1000 cubic feet of water.
• the second pond also has an approximate volume of 275,000 cubic feet and, hence, an average pond velocity in the second pond of 0.58 fps is attained, utilizing 0.07 hp per 1000 cubic feet of water.
• the 20 hp utilized in the second pond attained a velocity sufficient to maintain solids in a complete suspension.
• a horizontal flow sufficient to maintain ' solids in suspension extends forwardly at least 60 feet and a diffuse flow field approximately 60 feet wide is formed.
• a horizontal forward flow field sufficient to maintain solids in suspension extends forwardly at least 30 feet and a diffuse flow field has a width between approximately 30 and 40 feet.
• an average velocity of 0.50 fps should be sufficient to maintain solids in suspension within a waste water treatment facility.
• the higher power used within the first pond was utilized because of increased BOD loading to the pond system.
• the average pond velocities attained in the ponds illustrated in Figures 2a and 2b maintained solids totally in suspension. It is also within the contemplation of the present invention to utilize lower flow . velocities wherein solids may be only partially suspended.
• the present invention contemplates an average pond velocity of greater than 0.25 fps for the purpose of mixing the waste water. In the preferred embodiment, an average pond velocity of greater, than 0.5 fps is used. An average pond velocity of greater than 0.5 fps should be sufficient to maintain solids in complete suspension.
• oxygen was injected at a rate greater than 2.0 pounds of oxygen per horsepower.
• the method of the present inven ⁇ tion contemplates injecting oxygen at a rate of at least 1 pound of oxygen per horsepower hour -and preferably at a rate greater than 2 pounds of oxygen per horsepower hour.
• oxygen injection rates exceed ⁇ ing 3 pounds of oxygen per horsepower hour can be ob ⁇ tained.
• Figures 2a and 2b illustrate one form of an overall flow pattern in accordance with the method of the present invention.
• the overall flow pattern illustrated in Figures 2a and 2b includes a closed overall flow pattern, illustrated by vectors 40, which flows within a closed overall flow pattern indicated by vectors 38.
• Figure 5 illustrates an alternate overall flow pattern of water wherein two sets of aerators 10 are utilized to form a pair of closed overall flow patterns or paths side-by-side or adjacent to one another.
• the adjacent closed overall flow paths are indicated by horizontal flow vectors 44,
• Figure 6 illustrates an overall flow pattern system similar to that illustrated in Figures 2a and 2b wherein an outer closed overall flow path is indicated by horizontal flow vectors 50.
• the outer flow indicated by vectors 50 is created by an outer set of aerators 10 and the inner flow path is created by two aerators 10. One or more aerators, two are shown in
• the aerators 54 which are disposed out of the closed overall flow path are orientated towards the center of the flow path for the purpose of creating a subflow path of water to prevent the formation of void flow areas in the center of the pond.
• the subflow path is indicated by horizontal flow vectors 56.
• Figure 7 illustrates a variation of aerator orientation similar to Figure 6 wherein only a single set of aerators 10 is utilized to form a closed overall flow path, indicated by horizontal flow vectors 58.
• a number of aerators, designated by the number 60, in Figure 7 are disposed out of alignment with the closed overall flow to form a subflow path, indicated by horizontal flow vectors 62, for the purpose of preventing the formation of a void flow path in the center of the pond. While four aerators 60 are shown disposed out of alignment, it should be understood that any number of aerators may be so disposed.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Organic Chemistry (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Microbiology (AREA)
• Biodiversity & Conservation Biology (AREA)
• Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)
• Dot-Matrix Printers And Others (AREA)
• Character Spaces And Line Spaces In Printers (AREA)
• Activated Sludge Processes (AREA)

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• 1979
  • 1979-08-16 CA CA000333866A patent/CA1135883A/en not_active Expired
  • 1979-08-17 WO PCT/US1979/000619 patent/WO1980000435A1/en unknown
  • 1979-08-17 JP JP50138779A patent/JPH0314520B2/ja not_active Expired - Lifetime
  • 1979-08-17 GB GB8011124A patent/GB2058593B/en not_active Expired
  • 1979-08-17 DE DE2953063A patent/DE2953063C1/de not_active Expired
• 1980
  • 1980-03-25 EP EP79901064A patent/EP0020388A1/en not_active Withdrawn

Non-Patent Citations (1)

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