CA1135883A - Method of treating water - Google Patents
Method of treating waterInfo
- Publication number
- CA1135883A CA1135883A CA000333866A CA333866A CA1135883A CA 1135883 A CA1135883 A CA 1135883A CA 000333866 A CA000333866 A CA 000333866A CA 333866 A CA333866 A CA 333866A CA 1135883 A CA1135883 A CA 1135883A
- Authority
- CA
- Canada
- Prior art keywords
- aerators
- water
- propeller
- aerator
- flow path
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
Abstract
ABSTRACT
A method for treating water is disclosed. The method is applicable for the treatment of waste water within lagoons and ponds wherein the treatment of the waste water is accomplished m mainly through aeration. The method comprises 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 ad-jacent 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 horizontal; 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 one pound of oxygen per horsepower/hour; and inducing by means of the propellers of the aerators the closed overall flow pattern at an average linear velocity in a generally horizontal direction through a cross section to flow at the rate of at least 0.25 feet per second.
A method for treating water is disclosed. The method is applicable for the treatment of waste water within lagoons and ponds wherein the treatment of the waste water is accomplished m mainly through aeration. The method comprises 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 ad-jacent 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 horizontal; 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 one pound of oxygen per horsepower/hour; and inducing by means of the propellers of the aerators the closed overall flow pattern at an average linear velocity in a generally horizontal direction through a cross section to flow at the rate of at least 0.25 feet per second.
Description
~ ;i883 Background of the Invention The invention relates broadly to the treatment o~ water by aeration. The aeration txeatment o water has been used to , treat waste water within lagoons and to upgrade'the'quality of ~ ~"
natural bodies of water, such as lakes.
In the majority o~ pxior design critexia evaluations ~or aerated lagoons, focus has been placed almost entirely on the satisfaction of waste biochemical oxygen demand (~OD). That is, the amount o~ supplemental aexation or oxygen which was to be supplied to a lagoon was caIculated by the amount which the waste strength exceeded the oxygen available from photosyntheses and atmospheric aeration. The mixing O:e the waste water to main-tain solids in suspension while aerating the body of water was i~nored until recently. In an article entitled "How To Design Aerated Lagoon Systems to Meet 1977 E~luent 5tandards-Soluble ,~,,;," ~, Substrate Removal Relationships" by Sam C. White and Linvil G.
Rich at pages 82-83 of WATER AND SEW~GE WORKS, April 1976, mixing was included as a design parameter for an aerated lagoon. ;
Waste water treatment aeration systèms generally utilize either dif~used aîr aerators or mechanical aerators. A diffused air type aeratox introduces air or pure oxygen into water via ~-submerged ~orced 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 prim~rily from the standpoint of introducin~ a cer- ;~
tain amount of oxygen into the water being txeated. The mixing ~' ' of the water and the introduced oxygen has not been a design criteria and, hence, conventional Prlox aerator systems have ~nef~icient mixin~ capabilities~ For example, in a one acre ,
natural bodies of water, such as lakes.
In the majority o~ pxior design critexia evaluations ~or aerated lagoons, focus has been placed almost entirely on the satisfaction of waste biochemical oxygen demand (~OD). That is, the amount o~ supplemental aexation or oxygen which was to be supplied to a lagoon was caIculated by the amount which the waste strength exceeded the oxygen available from photosyntheses and atmospheric aeration. The mixing O:e the waste water to main-tain solids in suspension while aerating the body of water was i~nored until recently. In an article entitled "How To Design Aerated Lagoon Systems to Meet 1977 E~luent 5tandards-Soluble ,~,,;," ~, Substrate Removal Relationships" by Sam C. White and Linvil G.
Rich at pages 82-83 of WATER AND SEW~GE WORKS, April 1976, mixing was included as a design parameter for an aerated lagoon. ;
Waste water treatment aeration systèms generally utilize either dif~used aîr aerators or mechanical aerators. A diffused air type aeratox introduces air or pure oxygen into water via ~-submerged ~orced 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 prim~rily from the standpoint of introducin~ a cer- ;~
tain amount of oxygen into the water being txeated. The mixing ~' ' of the water and the introduced oxygen has not been a design criteria and, hence, conventional Prlox aerator systems have ~nef~icient mixin~ capabilities~ For example, in a one acre ,
- 2 -~ 13~ 3 :~
aerated pond for treating dome~tic waste. wa.ter, a pond which has ~ `
a depth of ten feet and a 3:1 side wall slope:and a volume of ~.
432,000 cubic feet, conventional aerator sizing procedures would require approximately 200-400 horsepower of sur~ace area capacity or over 1,000 horsepower ~or a di~fused alr system~ Such high power systems result in the oxygen requirement of the pond being satisfied fourfold, while probably not causing a complete mixing of the pond so as to assure scouring velocities of 0.5 ~eet per second throughout the pond~
Mechanical sur~ace aerators also exhibit an additional problem in that they ha~e separate and genera].ly conflicting mix~
ing vectors. That is, the force vectors from the aerators cannot generally be managed or manipulated and, hence, with closely spac-ed aerators, mixin~ vectors tend to cancel out. `
Another problem with most conventlonal aerator systems is that their oxygen transfer is ef~ectively limited by their inability to Properly mix the waste. .Most conventional aerator systems tend to have a very limited core of influence, that is, the conventional aerators cause a high dissolved oxygen concentra~
tion close to the units themsel~es because of the inability of the . ~:
units to mix. Thus, such conventional systems tend to create a ::
condition of oxygen oversaturation instea`d of under saturation, which would promote oxy~en trans~er. Many con~entional aerators ~ :~
are tested in small tanks and the test measured oxygen transfer :
rate at zero DO is then reported as a standard for comparision. .
This standard, however, iS not accurate in field apPlications since ln field applicatlons, the dissolved oxygen is required in a ~uch larger volume. In field installations, the conventional ~
~ :
~- ' :"
~gL35~ 3 ., .,~ .
. units tend to overaerate the nearby region and, thereby, to .
effectively work agains;t themselves. The di.ssolved oxygen is not effectively reaching outlying regions.
; Other problems also arise due to the fai.lure of the prior art aeration syætems to adequately mix the waste water being treated.
Without adequate mi~i.ng, for example, when 0.5 ps horizontal velo~
city is not attained, aerated lagoons may develop adverse conditions that effect performance:such as hydrauli.c short circuiting and/or .
sludge solids build-up. ~s waste water enter~ an uhmixed lagoon, a certain fraction of waste.may move directly to the outlet without adequate time Q i.nteracti.on with other lagoon contents for adequate .
treatment. If the pond is completely stagnate,in1uent velocity ' e~ects or momentum may set up such a "short circuit" current and ~:
i this: prohlem may be. exasperated by thermal stratification effects.
. Another prohlem is a s.ludge blanket build-up. Under mixed lagoons, ;' cells may develop aerobi.c-anaerobic regions analogous to a fac.ul-tative ~ond. ~naerobic ~ludge deposits found in undermixed lagoons ~:
may produce noxious odors such as H2S and/or NH3 gase~
. These gases may carry a high concentration of ox~dizable organi.c material (~..e.,BOD) into the water. Finally, the release of these gas.es to~ether with:the CH4 and N2 may contribute to float-ing solids and a tendency to "belch" these into the lagoon or .;
ceIl outlet. This mas~ of material may be transported into sub- -sequent txeatme.nt ceIls or out as a final e1uent.
51udge. deposits deposited in a lagoon must be regarded as lo~t ~xom control. Anaerobic digestion may :occur when tempera-.. tures pexmit, wi.th. the. result that perormance may become ~easonal~
The ~y~tem i`s e~e.cti.ve.ly out of operational control, when effluent ~uspended ~olids- in BOD concentrations become a function ~:
a ~:
~ ~L35i~83 of such factors. Such a system cannot reliably assure the degree of performance needed to meet the ordered quality standards of today.
The method in accordance with the present invention over-!' ., comes the above defic.iencies of conventional systems by both aera-~, ting a body of water and causing mixing of the aerated water at efficient power levels.
SUMMAR~ OF THE INVENTION .
The present i.nventi,on.relates to a method for treating :~
, 10 water. The method compxises:the steps of:
aexati,ng a bounded body of water wi.th a plurality of ~ ~
propeller-type aerators, each aerator having a hollow tube ~;:
.~ wi.th.opposite.ends,~ longitudinal axis extending between ';
,1 the. ends, and a propeller adjacent one of the ends;
placing e.ach of the aerators in the bvunded body of " ~atex with. the propeller and tuhe end adjacent thereto .1 below the'top s.urface Qf the water and with the longitu~
dinal ax~s of each'aeratox disposed at an angle below ' the, hori,zontal;
',' 20 drii,vi,ng the' aerators to create individual ci.rculating ,~
flo~ patterns around each'of the aerators;
~ mi~ing the water by axranging the aerators in a ; d,i`~positi~on to link the indivi,dual flow patterns created adjacent aerators to one another to ~orm a larger closed ve~all flo,~ pattern; :-iniecting Qxygen from ambient ai.r th.rough the tube into the ~ody of ~atex adjacent th.e propeIler at a rate gxeater than 1 pound of oxygen per horsepow.er-hour;
inducing by me.an~ of the: pxopellers of the aerators ' 30 the'closed ovexall flo~ pattern at an average linear .
.~
,:
~.~L3~ 3 .~
. .
velocity in a ~ener~lly horizontal directi~n through a cross section to flow at a rate o~ at least 0,25 feet per second.
In the preferred embodiment, the method of the present method includes the steps of injecting oxy~en at a rate ~reater than 2.0 pounds of oxygen per horsepower~hour; and of inducin~
the closed ov`erall flow pattern 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 than0.1 horsepower per .~ .
thousand cubic feet of water ln 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 e~ficient treatment of waste water and an efficient reduction of effluent is biological oxygen demand (BOD). It is believed that the efficient treatment ;~
, of waste water is due to the capability of both indu~ing the flow pattern to maintain solids in suspension and the iniection of oxygen both at efficient power ratings.
The o~erall flow pattern within a bounded body of water ;; ;
is attained by linking the circulating flow patterns of adjacent . .
aerators together. In one embodiment, a sin~le series or set of aerators is arranged in a single closed overall path. In ;
another embodiment a second set of aerators is arranged adjacent to the ~irst set to create a second closed flow pattern within the body of water. In another embodiment, a second set of aerators forms a closed flow pattern within the closed flow pattern formed b~ a first set of aerators.
In order to prevent v~id flow areas within the center of an overall flow pattern, one or more aerators can be displaced out of the overall flow pa-tteXn toward the center of the overall
aerated pond for treating dome~tic waste. wa.ter, a pond which has ~ `
a depth of ten feet and a 3:1 side wall slope:and a volume of ~.
432,000 cubic feet, conventional aerator sizing procedures would require approximately 200-400 horsepower of sur~ace area capacity or over 1,000 horsepower ~or a di~fused alr system~ Such high power systems result in the oxygen requirement of the pond being satisfied fourfold, while probably not causing a complete mixing of the pond so as to assure scouring velocities of 0.5 ~eet per second throughout the pond~
Mechanical sur~ace aerators also exhibit an additional problem in that they ha~e separate and genera].ly conflicting mix~
ing vectors. That is, the force vectors from the aerators cannot generally be managed or manipulated and, hence, with closely spac-ed aerators, mixin~ vectors tend to cancel out. `
Another problem with most conventlonal aerator systems is that their oxygen transfer is ef~ectively limited by their inability to Properly mix the waste. .Most conventional aerator systems tend to have a very limited core of influence, that is, the conventional aerators cause a high dissolved oxygen concentra~
tion close to the units themsel~es because of the inability of the . ~:
units to mix. Thus, such conventional systems tend to create a ::
condition of oxygen oversaturation instea`d of under saturation, which would promote oxy~en trans~er. Many con~entional aerators ~ :~
are tested in small tanks and the test measured oxygen transfer :
rate at zero DO is then reported as a standard for comparision. .
This standard, however, iS not accurate in field apPlications since ln field applicatlons, the dissolved oxygen is required in a ~uch larger volume. In field installations, the conventional ~
~ :
~- ' :"
~gL35~ 3 ., .,~ .
. units tend to overaerate the nearby region and, thereby, to .
effectively work agains;t themselves. The di.ssolved oxygen is not effectively reaching outlying regions.
; Other problems also arise due to the fai.lure of the prior art aeration syætems to adequately mix the waste water being treated.
Without adequate mi~i.ng, for example, when 0.5 ps horizontal velo~
city is not attained, aerated lagoons may develop adverse conditions that effect performance:such as hydrauli.c short circuiting and/or .
sludge solids build-up. ~s waste water enter~ an uhmixed lagoon, a certain fraction of waste.may move directly to the outlet without adequate time Q i.nteracti.on with other lagoon contents for adequate .
treatment. If the pond is completely stagnate,in1uent velocity ' e~ects or momentum may set up such a "short circuit" current and ~:
i this: prohlem may be. exasperated by thermal stratification effects.
. Another prohlem is a s.ludge blanket build-up. Under mixed lagoons, ;' cells may develop aerobi.c-anaerobic regions analogous to a fac.ul-tative ~ond. ~naerobic ~ludge deposits found in undermixed lagoons ~:
may produce noxious odors such as H2S and/or NH3 gase~
. These gases may carry a high concentration of ox~dizable organi.c material (~..e.,BOD) into the water. Finally, the release of these gas.es to~ether with:the CH4 and N2 may contribute to float-ing solids and a tendency to "belch" these into the lagoon or .;
ceIl outlet. This mas~ of material may be transported into sub- -sequent txeatme.nt ceIls or out as a final e1uent.
51udge. deposits deposited in a lagoon must be regarded as lo~t ~xom control. Anaerobic digestion may :occur when tempera-.. tures pexmit, wi.th. the. result that perormance may become ~easonal~
The ~y~tem i`s e~e.cti.ve.ly out of operational control, when effluent ~uspended ~olids- in BOD concentrations become a function ~:
a ~:
~ ~L35i~83 of such factors. Such a system cannot reliably assure the degree of performance needed to meet the ordered quality standards of today.
The method in accordance with the present invention over-!' ., comes the above defic.iencies of conventional systems by both aera-~, ting a body of water and causing mixing of the aerated water at efficient power levels.
SUMMAR~ OF THE INVENTION .
The present i.nventi,on.relates to a method for treating :~
, 10 water. The method compxises:the steps of:
aexati,ng a bounded body of water wi.th a plurality of ~ ~
propeller-type aerators, each aerator having a hollow tube ~;:
.~ wi.th.opposite.ends,~ longitudinal axis extending between ';
,1 the. ends, and a propeller adjacent one of the ends;
placing e.ach of the aerators in the bvunded body of " ~atex with. the propeller and tuhe end adjacent thereto .1 below the'top s.urface Qf the water and with the longitu~
dinal ax~s of each'aeratox disposed at an angle below ' the, hori,zontal;
',' 20 drii,vi,ng the' aerators to create individual ci.rculating ,~
flo~ patterns around each'of the aerators;
~ mi~ing the water by axranging the aerators in a ; d,i`~positi~on to link the indivi,dual flow patterns created adjacent aerators to one another to ~orm a larger closed ve~all flo,~ pattern; :-iniecting Qxygen from ambient ai.r th.rough the tube into the ~ody of ~atex adjacent th.e propeIler at a rate gxeater than 1 pound of oxygen per horsepow.er-hour;
inducing by me.an~ of the: pxopellers of the aerators ' 30 the'closed ovexall flo~ pattern at an average linear .
.~
,:
~.~L3~ 3 .~
. .
velocity in a ~ener~lly horizontal directi~n through a cross section to flow at a rate o~ at least 0,25 feet per second.
In the preferred embodiment, the method of the present method includes the steps of injecting oxy~en at a rate ~reater than 2.0 pounds of oxygen per horsepower~hour; and of inducin~
the closed ov`erall flow pattern 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 than0.1 horsepower per .~ .
thousand cubic feet of water ln 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 e~ficient treatment of waste water and an efficient reduction of effluent is biological oxygen demand (BOD). It is believed that the efficient treatment ;~
, of waste water is due to the capability of both indu~ing the flow pattern to maintain solids in suspension and the iniection of oxygen both at efficient power ratings.
The o~erall flow pattern within a bounded body of water ;; ;
is attained by linking the circulating flow patterns of adjacent . .
aerators together. In one embodiment, a sin~le series or set of aerators is arranged in a single closed overall path. In ;
another embodiment a second set of aerators is arranged adjacent to the ~irst set to create a second closed flow pattern within the body of water. In another embodiment, a second set of aerators forms a closed flow pattern within the closed flow pattern formed b~ a first set of aerators.
In order to prevent v~id flow areas within the center of an overall flow pattern, one or more aerators can be displaced out of the overall flow pa-tteXn toward the center of the overall
3 f low pattern. This displacement ~f one or more aerators creates a sub-flow pattern to avoid a void flow area. ~
' ' .`
- 6 - ~
L35~3 ! , By injectin$ oxygen at a contrQlled xate and by simultane-ously controlling the flow and flow patterns of the w~s~e water~
a controlled and e~ficient waste water treatment system can be maintained. The suspended solids levels in various lagoons and effluent may be manipulated with proper c~ntrol of the mixing lagoon by lagoon through a series systeme ~tually~ any form of seasonal control discharge can be provided for suitable solids while maintaining a flow-through condition ~or the li~uid~ In order to implement this strategy with aerator and turbulence ~; ;
(mixing) control, 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 in-; creasing 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 accumulate~as a thin aerobic sludge blanket for slow digestion through winter. As noted above, a reduced level of aeration may be provided during winter to assure that the lagoon surface remains at least par~
tially open to the atmosphere or, at least, that aerobic con~
ditions prevail throughout the water volumeO Thin sludge layers held for an extended period under aerobic condition may be expected to undergo composting and to waste away. ~hen the ~ ;
~` lagoon begins to form again, aeration and turbulence levels may be restored early and gradually to resuspend solids and to in-crease treatment wh~le providing for a~ flow proportloned discharg~ -:~' ~3S8~
.
of solids as runoff occurs and stream le~els are hi~h.' Thus, by utilizing the present method, a year round cont~olled system '' of waste water treatment can be attained at e~icient power levels.
Various advantages and features of novelty whl'ch charac-terize -the invention are pointed out with particularity in the claims annexed hereto and formin~ a part hereof~ However, ~or a better understanding of -the invention, its advantages, and objects obtained by its use, reference should be had to the drawings which form a further part hereof, and to the accompanying de-scriptive ~atter, in which there is illustr~ted and described a preferred embodiment of the invention.
Brief Description of the Drawin~s ' PIGURE 1 is a side elevational view illustrating a single '~
propeller-type aerator ~or use in the method of the present invention; ~` `
FIGURE 2a is a plan view diagrammatically illus-trating ~; ~
; the specific placement o~ a number o~ propeIler-type'aerators ~; ;
within a bounded body of water and the overall flow path in- ' ;-duced by the aerators; ~-FIGURE 2b is a plan view similar to FIGURE 2a illustra~
ting the specific placement of propeller-type aerators within a different bounded body of water;
FIGURE 3a is a diagra~ 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 i~ FIGURE 2b;
~ 30 " ' : ~ ' - . . . ~ . , . . ~ ~ , ~1:3SS13~
. FIGURE 4 i.s a diagrammatic plan view illustrating individ-ual horizontal circulating flow patterns induced by propeller-type i 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 illustrating another arrangement of propeller-type aerators and the resulting adjacent , overall flow paths; .
; FIGURE 6 is a diagrammatic plan view illustrating an `
arrangement of propeIler-type aerators in encircling overall ~, ~ 10 paths ~herein a subflo~ path.is created by displacing a number of ,,', aerators out of the oYerall flow path;
:, FIGURE 7 is, a diagrammatic plan view illustratiny the :: , placement of a plurality of propeller-type'aerators in a single : oYerall flow path ~herein a number of aerators are displaced from '~
~ alignment ~i.th the overall flo~ path to create a subflow path.
I DETAILED DE~SCRIPTION OF THE INVENTION
~.!, Re.ferriny to the dra~ings, there is shown i.n Figure 1 a , ' ;
'~ propeller-type aerator 10 for use'in the method of the present invention. The' aerator 10 i.s shown disposed ~ithin a li~uid 12 , 20 preferab.ly ~ater or ~aste ~ater. The aerator 10 has an outer tubular housin~ 14 and an inner tube 16 rotatably carried within ', the outer tubular housing 14. The inner tube 16 ex-tends ~ithin ' the tub.ular housing 14 to a leveI above the top surface of the :, uid 12 and is dri.vingly coupled to a motor carried ~lthin a ` ~.
. motor housin~ 18. The, inner tube 16 has at least one hole at its i~
:. upper end abo~e'the top leveI of the li.qui.d 12 for admitting air into the.'interior of the tube 16. The inner tube 16 extends . out~ardly ~eyond the lo~er end of the tubular housing 14 and has :.:
'', a prope.Iler 20 ~ixedly attached thereto. A di.ffusion tube 22 is ~' ', 30 ::
8~
also attached to the inner tube 16 and has a hollow interior which communicates with the hollo~ interior of the inner tube 16. ::
~hen the inner tube 14 is rotated by the motor, the .
propeller 20 is also rotated. As the propellex 20 rotates, it causes a directional, turbulent flow field in the liquid 12. The reduced pressur~ zone created by this flow downstxeam of the pro-peller aspirates: or draws air do~n the hollow tube 16 and causes :
air to enter the li.quid through an open end of the diffusion tube 22 as air b.ub~les 24. The air bubbles 24 are thereafter dispersed ' : ' .~ .
by the turbulence caused by the propeller. In this manner, the ' propeIler-type aerator lO aerates while it mixes. As will be ..
: explained more fully hereinafter, aerators 10 can be arranged to proYide a directional flo~ ~ith the aerators 10 installed to ~:
contri.bute addi.tiYeIy to the uniform mixing patterns involving an .
. entire. bounded body of ~ater. Liquid flow can thus be directed '.
and circulation pattern~ can be developed to assure desired velocity vectors throughout an entire Yolume of a body of water being .'.~' :. treated. :
The inner tube'16 has a Iongitudinal axis indicated by :' line 26. The:aerator 10 i.s supported in the liquid 12 by a ~"
platform or ~oom 28. The aerator 10 is attached to the plat~orm :~ 28 in any conyentional manner, such as by a bracket 30. The i~'. aerator 10 is sup~Qrted in.the liquid 12 .such that the longitudinal axis 26 fo.rma an an~le ~ith:the horizontal ~etween 15 and 25 ~.
~ de~ree~. ~refer~bl~ the angle is set at 22 degrees. In this .' manner, th~: mi~in~ ene.r~y caused by the rotati.ng propeller tends .
to ~romote ci.xculation and flow over a larger area than is ~-typical Q~ conve~tional turbine aerators. I.~ the angle is in~
crea~ed past 25 degxees so that the tube 14 ~ecomes more vertical, to some'degre.e hl.~her oxygen trans~er is obtainea at the expense .' ~ ;
1~35~83 of mixing. As the angle is decreased below 15 degrees to~ard the horizontal, mixing i.s increased at the expense of oxygen transfer. It has ~een found that the range of 15 to 25 degrees for the angle of inclination is an optimum compromise of mixing and aeration and that the 22 degree angle of :inclination is preferahle.
The method of the present inventi.on finds its primary use in aerated lagoons or ponds used as a portion of an overall waste ~ater treatment process. Aerated lagoons systems can be 10 desi.gned for thxee different leveIs of mixing. LeveIs of mixing :
are generally determi.ned by the degree of pollution in the water or the BOD requi.rement. For most waste water treatment lagoons receiYing reIativel~ di.lute domestic wastes, the power required to satis.fy oxygen demand through:most of the year is markedly less than requi.red to maintain 501ids in suspension. The lowest.level .
of pow.er input must txansfer s.uffici.ent oxygen to satisfy demand exerted by the satisfaction of BOD in the waste. Aeration suffici.ent : to transfer 0.7 to 1.4 pounds of oxygen per pound BOD exerted is typi.cal. ~n intermedi.ate level of power input must provide for uni.form oxy~en di.spers.ion throughout a lagoon volume in addition to mereIy ~upplying a specified quantity of oxy~en. He.nce, addi~
tional pow.er over that required to merely i.nject the oxygen is ~ ;
needed ~o that minimal circulation effects are created to ensure uniform distribution of oxygen throughout a la~oon volume.
j~ :,. ..
. Howeyer, at such.an i.ntermediate leveI, sufficient turhulence is ; not created to mai.ntain solids in suspens.i.on. The highest level of power i.nput that would reasonably be necessary would provide for o~gen dispers~l.on as ~ell as minimum s.couring veloci.ties, such as~ Q.4 to 0.5 feet per second (fpsl. Prior art aeration systems h.a~e re~uir~ed at l~ast ~ 5 hp/10~:3.o.f wa~er and hl.gher ~ower `,~!. :
.~ .
: densities to attain ~uch.flow velocities.
The method of the present invention accompli.shes both ~ ;~
adequate oxygen injection into waste water and mi~ing of the ;~
aerated ~a~te water at ef~icient power levels. The present inven-tion permits management or control of oxygen injection and mixing velocities at effi.cient power levels under numerous water pollution :.
- condi.tion~. ~he method includes the steps of providing a plurality ; .~
of propeIler-t~pe aerators where each. aerator has a hollow tube ; ~`
wi.th opposite ends and a longitudinal axis extendi.ng bet~een the ends and a propeIler adjacent one of the ends. The aerator 10 is . s.peci.all~ 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 beIo~ the top surface of the ;~ ~:
: water and ~i.th.a longitudinal axis of each.:aera-tor disposed at an angle beIo~ the horizontal. The water i.s mixed by arranginy and driving the. aeratars i.n a di~position so that indi.vidual circulating flow patterns are created around each.of the aerators and the ~ indiyidual flow patterns-link to one another to form a larger .: closea overall flo~ pattern. That is, the. aerators are arranged ~ .
such.that ~hen:the propellers-of the aerators are driven at suffi-ciently hi:gh. ~peeds to inject ambient air i.nto the water, indivi- ~
. dual ~low patterns are created around each.of the aerators and ~:
: are linked to~th~r to form a larger closea overall flow pattern. ;~
The individual flo~ patterns and the linki.ng of adjacent indivi.dual flow-pattern~ is illustrated in Fi.gure 4. Three aeratoxs laa, 10~, lOc a~e il:lustrated diagrammaticall~ i.n Fig. 4.
Horizontal flo.~ vectors indi.cating a horizontal flow of the water are sho~n emanati.n~ about each. of the aerators lOa,.lOb, and lOc.
A plurali.ty of forward hbrizontal flow vector~ 32 indicate a ~
~ :
- 12 - ~:
1~3$Bi~
~ j horizontal flow of fluid forward of the propellar of aerator lOa.
Negative horizontal flow of vectors 34 indicate a horizontal flow of fluid which i5 drawn toward the propeller of operator lOa from the area rearward of the propeller. Horizontal flow vectors 36 indicate a diffuse hbrizontal flow of fluid bending backward from the forward flow indicated bv vectors 32 and interconnecting or forming a portion of the flow indicated by negative vectors 34.
Similarly numbered flow vectors are indicated about aerators lOb and lOc. As seen în Figure 4 -the aerators lOa, lOb, and lOc are ~ , arranged relati.ve to one another so that at least some of the flow indi.cated by the negative flow vectors 34 of one of the aerators. link.s 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 yeneral direction of the forward flow vectors 32.
Fi~ure~ 2a and 2~ illustrate a plurality of propeller~
type aerators 10 supported on platforms or booms 28 wi.thin a pair ~
of waste water treatment lagoons in which studies of the present ~ ::
lnventiQn ~ere made. Flow vectors or arrows 4G, 38 indicate a closed oYerall horizontal flo~ pattern or path.of the waste water.
The outex set or ci.rcle of aerators 10 creates the overall flow ,~
pattern indi.cated by vectoxs.38. The overall flow pattern indicated hy vectors 40.is, create.d by an inner set or circle of aerators 10, The oYexall flo~ pattern indi.cated by vector~ 40 circulates within the over~ll flo~ pattexn indicated by vectors 38.
Fi~u,res 2a and 2b dia~rammatically represent a plan view ~ .:
of two la~oon~ or ponds that form a portion of a waste water treat~lent plant ~ithi.n ~hi,ch the present method was utilized~ .
ThR water treatment plant also included a primary sedimentation unit, a ,roughin~ filter and a clari~ier follo~.ed by a pond or ~35~3 ` ~
lagoon system having four ponds, which Figs. 2a and 2b,respectively, illustrate first a~d second ponds of the pond system. Each of these first two ponds ha~ a surface area of approximately 3/4 of an acre and a water volume of approximately 275,000 cubic fee. The ponds are approximately 175 ft. wi,de and 190 ft. long.
' The pond of Fi,g.2a has a plurality of propeller-type ~
aerators 10 installed ~i,th,a total power of 36 hp. The pond repre- ' ~,' sented by Fig.2b has a plurali-ty of aerators 10 installed with a . .
combined po~er of 20 hp. The booms 28 extend inwardly from approxi-mately the'middle of each,side of each,~pond.Each of the outer ' ;
;aerators ia dispo~ed approximately 30ft. from a respective side wall ~;-and each'of the, inner aerators is disposed approximately 60 ft.
from a respective side wall.
; Fi~. 3a illustrate~ a profile or verti,cal section through ~, the pond illustrated in Fi,b.2a along the 195 ft. line passing " between SE and N~. Flg.3b i,llustrates a similar profile or vertical , section alang 195 ft. li,ne passing SW to NE in the pond illustrated -', ~' in Fig.2b. Figs. 3a and 3b specify the veIocity measurements in ;~
., : .
~eet per second ~fps~ taken at various depths within the ponds,along ~' ' the'cross section, when the aerators 10 were'operaking to create " the overall flow patterns indicated by arrows 38,40. The measured ~' veloci,ties in Fig.3a result in average linear velocity in a gener~
ally horizontal directian through th,é cross ~ection of the first ' ~, .,. ~ ~.
pond o~ 0.77 fps and the veIocities measured in Flg.3b result in average linear veIocity in a ~enerally horizontal direction through ~-;, a cross section of the second pond o~ 0.58 ~ps. These calculated average pond YeIocitie~ are also the avera~e velocity of the closed , ,~
overall ~low-patkern in the ponds. Since a total of 36 hp is used ' in the ~ir~t pond and the ~irst pond has a yolume of approximately ~;
,, 30 275,000 cuhic ~eet, the avera~e pond veloci,ty of 0~77 ~ps is attained, utili,zin~ 0~13 hp per lOOQ cubic ~k. of ~ater. The second pond also has an approximate volume o~ 275,000 cubic ~eet .
.~ .
,~ - 14 ~, L3~8~3 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.
When a 5 horsepower propeller-type aerator is used and the aerator is disposed approximately 22 degrees below the horizontal, a horizontal flow sufficient to maintain solicLs in suspension extends forwardly at least 60 feet and a diffuse flow field approximately 60 feet wide is formed. ~hen a 2 horsepower propeller-type aerator is used and is disposed at an angle approximately 22 degrees below the horizontal, a horizontal forward flow field sufficient to maintain solids in suspension extends for~ardly at least 30 feet and a diffuse flow field has ; a width bet~een approximateIy 30 and 40 feet.
It is~ generally -.,, ~.~
.' ':
! ~ ~
- .
~5~
recognized, an average pond 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.
As mentioned above, 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 flo~ velocities wherein solids may be only partially suspended. However, the present invention con~
lQ templates an average pond veIocity of greater thanlQ25 fps for the `
purpose of mixing the waste water. In the preferréd embodiment, an average pond velocity of greater than Q.5 fps is used. An average pond velocity of yreater than 0.5 fps shbuld be sufficient -~
; to maintain solids in complete suspension~
In the ponds illustrated by Figures 2a and 2b, oxygen was injected at a rate greater than 2.0 pounds of oxygen per horsepo~er. The method of the present invention contemplates ~ ~
injectiny oxygen at a rate of at least 1 pound of oxygen per horse- -power hour and preEera~ly at a rate ~reater than 2 pounds of oxygen per horsepower hour. In the present method, utilizing propeller-type aerators as illustrated in Figure 1, oxygen injection rates exceeding 3 pounds of oxygen per horsepower ~ ~-hour can be obtained.
While some conventional aerators claim a capability of injectîn~ oxy~en at the above rate, Applicants are una~are of any aeration system which can combine both the oxygen injection and inducement of flow velocîty in accordance wîth the method of the present in~ention.
Fî~ures 2a and 2b illustrate one form of an overall flow pattern in accordance with the method of the present invention.
~.
.
- .. . .. ~.. . ~
~.~.35~
The overall flow pattern illustrated in Fi.gs. 2a and 2b includes ::.
': a closed overall flow pattern, illustrated by vectors 40, which : flows within a closed overall flow pattern indicated by vectors 33.
.~ Fi.g. 5 illus:trate~ an alternate overall flow pattern of water . wherein tw.o sets of aerator~ 10 are utilized to form a pair of closed overall flo~ patterns or paths side-by-si.de or adjacent to one another. The adjacent closed overall flo~ paths are indlcated by h.orizontal flow vectors 44, 46.
F~g. 6 i.llustrates: an overall flow pattern system similar to that i.llu~trated in Fi.gs. 2a and 2b wherein an outer closed overall flo~ path'is indicated by horizont.al flow vectors 50. An , inner cloaed overall flow path is indicated by horizontal flow :
'~ vectors 52. The'outer flow indicated by vectors 50 is created by an outer $et of aerators l0 and the inner flow path is created by ~:
. ~ - .
two aeratoxs 10. One or more aerators, two are shown in Fig. 6 and are desi:gnated by the number 54, are displaced out of alignment .. with the inner flo~ path'toward the center thereof. The aerators - ~:
54 which.'are di.sposed out of the closed overall flow path are ori.entatea to~ards the:center of the flow path for the purpose of 20 creatin~ a subflow path of ~ater to prevent tha formation of void ;' flow areas in -the center of the pond. The subflow path is indicated by horizontal flow vectors 56.
Fig. 7 illustrates a variation of aerator orientation simi-lar to Fig. 6 wherein only a single set of aera-tors 10 is utilized .'~
', to form a closed overall flow path, indicated by horizontal flow :.'.
vector~ 58. A number of aerators, designated by the number 60, in .
~ Fig. 7 are disposed out of alignment with the close~d overall flow '~
i to :Eorm a subflow path, indicated by horizontal flow vectors 62, for the purpose of preventin~ the formation of a void flow path in the center of the~pond. While four aerators 60 are'shown disposed out of alignment, it shbuld be understood that any number of ''~ aerators may be ~o disposed.
,.... ,- ~ ':
.: - 17 - ~ ~
1 : :
. ,~ . , ~3S~3 Numerous characteristics and advantages of o~ invention have been set forth in the foregoing description, together with :
details of the structure and function of the invention, and the novel features thereof are pointed out in the appended claims.
The disclosure, ho~.ever, is illustrative only" and changes may be made in detail, especially in ma~ters of shape, size, and arrange-ment of parts, ~ithin the principle of the invention, to the full . :
extent indicated by the broad general meaning of the terms in ;~ ~hich. the appended claims are expressed.
;, ~ '' ' ,~. ',' ;' ''~, `;
, :,~"
.. ;~.
;,''` '';' ::: .
`~'~',.
, ' . .. ~
' ., - 18 - .
' ' .`
- 6 - ~
L35~3 ! , By injectin$ oxygen at a contrQlled xate and by simultane-ously controlling the flow and flow patterns of the w~s~e water~
a controlled and e~ficient waste water treatment system can be maintained. The suspended solids levels in various lagoons and effluent may be manipulated with proper c~ntrol of the mixing lagoon by lagoon through a series systeme ~tually~ any form of seasonal control discharge can be provided for suitable solids while maintaining a flow-through condition ~or the li~uid~ In order to implement this strategy with aerator and turbulence ~; ;
(mixing) control, 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 in-; creasing 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 accumulate~as a thin aerobic sludge blanket for slow digestion through winter. As noted above, a reduced level of aeration may be provided during winter to assure that the lagoon surface remains at least par~
tially open to the atmosphere or, at least, that aerobic con~
ditions prevail throughout the water volumeO Thin sludge layers held for an extended period under aerobic condition may be expected to undergo composting and to waste away. ~hen the ~ ;
~` lagoon begins to form again, aeration and turbulence levels may be restored early and gradually to resuspend solids and to in-crease treatment wh~le providing for a~ flow proportloned discharg~ -:~' ~3S8~
.
of solids as runoff occurs and stream le~els are hi~h.' Thus, by utilizing the present method, a year round cont~olled system '' of waste water treatment can be attained at e~icient power levels.
Various advantages and features of novelty whl'ch charac-terize -the invention are pointed out with particularity in the claims annexed hereto and formin~ a part hereof~ However, ~or a better understanding of -the invention, its advantages, and objects obtained by its use, reference should be had to the drawings which form a further part hereof, and to the accompanying de-scriptive ~atter, in which there is illustr~ted and described a preferred embodiment of the invention.
Brief Description of the Drawin~s ' PIGURE 1 is a side elevational view illustrating a single '~
propeller-type aerator ~or use in the method of the present invention; ~` `
FIGURE 2a is a plan view diagrammatically illus-trating ~; ~
; the specific placement o~ a number o~ propeIler-type'aerators ~; ;
within a bounded body of water and the overall flow path in- ' ;-duced by the aerators; ~-FIGURE 2b is a plan view similar to FIGURE 2a illustra~
ting the specific placement of propeller-type aerators within a different bounded body of water;
FIGURE 3a is a diagra~ 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 i~ FIGURE 2b;
~ 30 " ' : ~ ' - . . . ~ . , . . ~ ~ , ~1:3SS13~
. FIGURE 4 i.s a diagrammatic plan view illustrating individ-ual horizontal circulating flow patterns induced by propeller-type i 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 illustrating another arrangement of propeller-type aerators and the resulting adjacent , overall flow paths; .
; FIGURE 6 is a diagrammatic plan view illustrating an `
arrangement of propeIler-type aerators in encircling overall ~, ~ 10 paths ~herein a subflo~ path.is created by displacing a number of ,,', aerators out of the oYerall flow path;
:, FIGURE 7 is, a diagrammatic plan view illustratiny the :: , placement of a plurality of propeller-type'aerators in a single : oYerall flow path ~herein a number of aerators are displaced from '~
~ alignment ~i.th the overall flo~ path to create a subflow path.
I DETAILED DE~SCRIPTION OF THE INVENTION
~.!, Re.ferriny to the dra~ings, there is shown i.n Figure 1 a , ' ;
'~ propeller-type aerator 10 for use'in the method of the present invention. The' aerator 10 i.s shown disposed ~ithin a li~uid 12 , 20 preferab.ly ~ater or ~aste ~ater. The aerator 10 has an outer tubular housin~ 14 and an inner tube 16 rotatably carried within ', the outer tubular housing 14. The inner tube 16 ex-tends ~ithin ' the tub.ular housing 14 to a leveI above the top surface of the :, uid 12 and is dri.vingly coupled to a motor carried ~lthin a ` ~.
. motor housin~ 18. The, inner tube 16 has at least one hole at its i~
:. upper end abo~e'the top leveI of the li.qui.d 12 for admitting air into the.'interior of the tube 16. The inner tube 16 extends . out~ardly ~eyond the lo~er end of the tubular housing 14 and has :.:
'', a prope.Iler 20 ~ixedly attached thereto. A di.ffusion tube 22 is ~' ', 30 ::
8~
also attached to the inner tube 16 and has a hollow interior which communicates with the hollo~ interior of the inner tube 16. ::
~hen the inner tube 14 is rotated by the motor, the .
propeller 20 is also rotated. As the propellex 20 rotates, it causes a directional, turbulent flow field in the liquid 12. The reduced pressur~ zone created by this flow downstxeam of the pro-peller aspirates: or draws air do~n the hollow tube 16 and causes :
air to enter the li.quid through an open end of the diffusion tube 22 as air b.ub~les 24. The air bubbles 24 are thereafter dispersed ' : ' .~ .
by the turbulence caused by the propeller. In this manner, the ' propeIler-type aerator lO aerates while it mixes. As will be ..
: explained more fully hereinafter, aerators 10 can be arranged to proYide a directional flo~ ~ith the aerators 10 installed to ~:
contri.bute addi.tiYeIy to the uniform mixing patterns involving an .
. entire. bounded body of ~ater. Liquid flow can thus be directed '.
and circulation pattern~ can be developed to assure desired velocity vectors throughout an entire Yolume of a body of water being .'.~' :. treated. :
The inner tube'16 has a Iongitudinal axis indicated by :' line 26. The:aerator 10 i.s supported in the liquid 12 by a ~"
platform or ~oom 28. The aerator 10 is attached to the plat~orm :~ 28 in any conyentional manner, such as by a bracket 30. The i~'. aerator 10 is sup~Qrted in.the liquid 12 .such that the longitudinal axis 26 fo.rma an an~le ~ith:the horizontal ~etween 15 and 25 ~.
~ de~ree~. ~refer~bl~ the angle is set at 22 degrees. In this .' manner, th~: mi~in~ ene.r~y caused by the rotati.ng propeller tends .
to ~romote ci.xculation and flow over a larger area than is ~-typical Q~ conve~tional turbine aerators. I.~ the angle is in~
crea~ed past 25 degxees so that the tube 14 ~ecomes more vertical, to some'degre.e hl.~her oxygen trans~er is obtainea at the expense .' ~ ;
1~35~83 of mixing. As the angle is decreased below 15 degrees to~ard the horizontal, mixing i.s increased at the expense of oxygen transfer. It has ~een found that the range of 15 to 25 degrees for the angle of inclination is an optimum compromise of mixing and aeration and that the 22 degree angle of :inclination is preferahle.
The method of the present inventi.on finds its primary use in aerated lagoons or ponds used as a portion of an overall waste ~ater treatment process. Aerated lagoons systems can be 10 desi.gned for thxee different leveIs of mixing. LeveIs of mixing :
are generally determi.ned by the degree of pollution in the water or the BOD requi.rement. For most waste water treatment lagoons receiYing reIativel~ di.lute domestic wastes, the power required to satis.fy oxygen demand through:most of the year is markedly less than requi.red to maintain 501ids in suspension. The lowest.level .
of pow.er input must txansfer s.uffici.ent oxygen to satisfy demand exerted by the satisfaction of BOD in the waste. Aeration suffici.ent : to transfer 0.7 to 1.4 pounds of oxygen per pound BOD exerted is typi.cal. ~n intermedi.ate level of power input must provide for uni.form oxy~en di.spers.ion throughout a lagoon volume in addition to mereIy ~upplying a specified quantity of oxy~en. He.nce, addi~
tional pow.er over that required to merely i.nject the oxygen is ~ ;
needed ~o that minimal circulation effects are created to ensure uniform distribution of oxygen throughout a la~oon volume.
j~ :,. ..
. Howeyer, at such.an i.ntermediate leveI, sufficient turhulence is ; not created to mai.ntain solids in suspens.i.on. The highest level of power i.nput that would reasonably be necessary would provide for o~gen dispers~l.on as ~ell as minimum s.couring veloci.ties, such as~ Q.4 to 0.5 feet per second (fpsl. Prior art aeration systems h.a~e re~uir~ed at l~ast ~ 5 hp/10~:3.o.f wa~er and hl.gher ~ower `,~!. :
.~ .
: densities to attain ~uch.flow velocities.
The method of the present invention accompli.shes both ~ ;~
adequate oxygen injection into waste water and mi~ing of the ;~
aerated ~a~te water at ef~icient power levels. The present inven-tion permits management or control of oxygen injection and mixing velocities at effi.cient power levels under numerous water pollution :.
- condi.tion~. ~he method includes the steps of providing a plurality ; .~
of propeIler-t~pe aerators where each. aerator has a hollow tube ; ~`
wi.th opposite ends and a longitudinal axis extendi.ng bet~een the ends and a propeIler adjacent one of the ends. The aerator 10 is . s.peci.all~ 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 beIo~ the top surface of the ;~ ~:
: water and ~i.th.a longitudinal axis of each.:aera-tor disposed at an angle beIo~ the horizontal. The water i.s mixed by arranginy and driving the. aeratars i.n a di~position so that indi.vidual circulating flow patterns are created around each.of the aerators and the ~ indiyidual flow patterns-link to one another to form a larger .: closea overall flo~ pattern. That is, the. aerators are arranged ~ .
such.that ~hen:the propellers-of the aerators are driven at suffi-ciently hi:gh. ~peeds to inject ambient air i.nto the water, indivi- ~
. dual ~low patterns are created around each.of the aerators and ~:
: are linked to~th~r to form a larger closea overall flow pattern. ;~
The individual flo~ patterns and the linki.ng of adjacent indivi.dual flow-pattern~ is illustrated in Fi.gure 4. Three aeratoxs laa, 10~, lOc a~e il:lustrated diagrammaticall~ i.n Fig. 4.
Horizontal flo.~ vectors indi.cating a horizontal flow of the water are sho~n emanati.n~ about each. of the aerators lOa,.lOb, and lOc.
A plurali.ty of forward hbrizontal flow vector~ 32 indicate a ~
~ :
- 12 - ~:
1~3$Bi~
~ j horizontal flow of fluid forward of the propellar of aerator lOa.
Negative horizontal flow of vectors 34 indicate a horizontal flow of fluid which i5 drawn toward the propeller of operator lOa from the area rearward of the propeller. Horizontal flow vectors 36 indicate a diffuse hbrizontal flow of fluid bending backward from the forward flow indicated bv vectors 32 and interconnecting or forming a portion of the flow indicated by negative vectors 34.
Similarly numbered flow vectors are indicated about aerators lOb and lOc. As seen în Figure 4 -the aerators lOa, lOb, and lOc are ~ , arranged relati.ve to one another so that at least some of the flow indi.cated by the negative flow vectors 34 of one of the aerators. link.s 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 yeneral direction of the forward flow vectors 32.
Fi~ure~ 2a and 2~ illustrate a plurality of propeller~
type aerators 10 supported on platforms or booms 28 wi.thin a pair ~
of waste water treatment lagoons in which studies of the present ~ ::
lnventiQn ~ere made. Flow vectors or arrows 4G, 38 indicate a closed oYerall horizontal flo~ pattern or path.of the waste water.
The outex set or ci.rcle of aerators 10 creates the overall flow ,~
pattern indi.cated by vectoxs.38. The overall flow pattern indicated hy vectors 40.is, create.d by an inner set or circle of aerators 10, The oYexall flo~ pattern indi.cated by vector~ 40 circulates within the over~ll flo~ pattexn indicated by vectors 38.
Fi~u,res 2a and 2b dia~rammatically represent a plan view ~ .:
of two la~oon~ or ponds that form a portion of a waste water treat~lent plant ~ithi.n ~hi,ch the present method was utilized~ .
ThR water treatment plant also included a primary sedimentation unit, a ,roughin~ filter and a clari~ier follo~.ed by a pond or ~35~3 ` ~
lagoon system having four ponds, which Figs. 2a and 2b,respectively, illustrate first a~d second ponds of the pond system. Each of these first two ponds ha~ a surface area of approximately 3/4 of an acre and a water volume of approximately 275,000 cubic fee. The ponds are approximately 175 ft. wi,de and 190 ft. long.
' The pond of Fi,g.2a has a plurality of propeller-type ~
aerators 10 installed ~i,th,a total power of 36 hp. The pond repre- ' ~,' sented by Fig.2b has a plurali-ty of aerators 10 installed with a . .
combined po~er of 20 hp. The booms 28 extend inwardly from approxi-mately the'middle of each,side of each,~pond.Each of the outer ' ;
;aerators ia dispo~ed approximately 30ft. from a respective side wall ~;-and each'of the, inner aerators is disposed approximately 60 ft.
from a respective side wall.
; Fi~. 3a illustrate~ a profile or verti,cal section through ~, the pond illustrated in Fi,b.2a along the 195 ft. line passing " between SE and N~. Flg.3b i,llustrates a similar profile or vertical , section alang 195 ft. li,ne passing SW to NE in the pond illustrated -', ~' in Fig.2b. Figs. 3a and 3b specify the veIocity measurements in ;~
., : .
~eet per second ~fps~ taken at various depths within the ponds,along ~' ' the'cross section, when the aerators 10 were'operaking to create " the overall flow patterns indicated by arrows 38,40. The measured ~' veloci,ties in Fig.3a result in average linear velocity in a gener~
ally horizontal directian through th,é cross ~ection of the first ' ~, .,. ~ ~.
pond o~ 0.77 fps and the veIocities measured in Flg.3b result in average linear veIocity in a ~enerally horizontal direction through ~-;, a cross section of the second pond o~ 0.58 ~ps. These calculated average pond YeIocitie~ are also the avera~e velocity of the closed , ,~
overall ~low-patkern in the ponds. Since a total of 36 hp is used ' in the ~ir~t pond and the ~irst pond has a yolume of approximately ~;
,, 30 275,000 cuhic ~eet, the avera~e pond veloci,ty of 0~77 ~ps is attained, utili,zin~ 0~13 hp per lOOQ cubic ~k. of ~ater. The second pond also has an approximate volume o~ 275,000 cubic ~eet .
.~ .
,~ - 14 ~, L3~8~3 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.
When a 5 horsepower propeller-type aerator is used and the aerator is disposed approximately 22 degrees below the horizontal, a horizontal flow sufficient to maintain solicLs in suspension extends forwardly at least 60 feet and a diffuse flow field approximately 60 feet wide is formed. ~hen a 2 horsepower propeller-type aerator is used and is disposed at an angle approximately 22 degrees below the horizontal, a horizontal forward flow field sufficient to maintain solids in suspension extends for~ardly at least 30 feet and a diffuse flow field has ; a width bet~een approximateIy 30 and 40 feet.
It is~ generally -.,, ~.~
.' ':
! ~ ~
- .
~5~
recognized, an average pond 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.
As mentioned above, 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 flo~ velocities wherein solids may be only partially suspended. However, the present invention con~
lQ templates an average pond veIocity of greater thanlQ25 fps for the `
purpose of mixing the waste water. In the preferréd embodiment, an average pond velocity of greater than Q.5 fps is used. An average pond velocity of yreater than 0.5 fps shbuld be sufficient -~
; to maintain solids in complete suspension~
In the ponds illustrated by Figures 2a and 2b, oxygen was injected at a rate greater than 2.0 pounds of oxygen per horsepo~er. The method of the present invention contemplates ~ ~
injectiny oxygen at a rate of at least 1 pound of oxygen per horse- -power hour and preEera~ly at a rate ~reater than 2 pounds of oxygen per horsepower hour. In the present method, utilizing propeller-type aerators as illustrated in Figure 1, oxygen injection rates exceeding 3 pounds of oxygen per horsepower ~ ~-hour can be obtained.
While some conventional aerators claim a capability of injectîn~ oxy~en at the above rate, Applicants are una~are of any aeration system which can combine both the oxygen injection and inducement of flow velocîty in accordance wîth the method of the present in~ention.
Fî~ures 2a and 2b illustrate one form of an overall flow pattern in accordance with the method of the present invention.
~.
.
- .. . .. ~.. . ~
~.~.35~
The overall flow pattern illustrated in Fi.gs. 2a and 2b includes ::.
': a closed overall flow pattern, illustrated by vectors 40, which : flows within a closed overall flow pattern indicated by vectors 33.
.~ Fi.g. 5 illus:trate~ an alternate overall flow pattern of water . wherein tw.o sets of aerator~ 10 are utilized to form a pair of closed overall flo~ patterns or paths side-by-si.de or adjacent to one another. The adjacent closed overall flo~ paths are indlcated by h.orizontal flow vectors 44, 46.
F~g. 6 i.llustrates: an overall flow pattern system similar to that i.llu~trated in Fi.gs. 2a and 2b wherein an outer closed overall flo~ path'is indicated by horizont.al flow vectors 50. An , inner cloaed overall flow path is indicated by horizontal flow :
'~ vectors 52. The'outer flow indicated by vectors 50 is created by an outer $et of aerators l0 and the inner flow path is created by ~:
. ~ - .
two aeratoxs 10. One or more aerators, two are shown in Fig. 6 and are desi:gnated by the number 54, are displaced out of alignment .. with the inner flo~ path'toward the center thereof. The aerators - ~:
54 which.'are di.sposed out of the closed overall flow path are ori.entatea to~ards the:center of the flow path for the purpose of 20 creatin~ a subflow path of ~ater to prevent tha formation of void ;' flow areas in -the center of the pond. The subflow path is indicated by horizontal flow vectors 56.
Fig. 7 illustrates a variation of aerator orientation simi-lar to Fig. 6 wherein only a single set of aera-tors 10 is utilized .'~
', to form a closed overall flow path, indicated by horizontal flow :.'.
vector~ 58. A number of aerators, designated by the number 60, in .
~ Fig. 7 are disposed out of alignment with the close~d overall flow '~
i to :Eorm a subflow path, indicated by horizontal flow vectors 62, for the purpose of preventin~ the formation of a void flow path in the center of the~pond. While four aerators 60 are'shown disposed out of alignment, it shbuld be understood that any number of ''~ aerators may be ~o disposed.
,.... ,- ~ ':
.: - 17 - ~ ~
1 : :
. ,~ . , ~3S~3 Numerous characteristics and advantages of o~ invention have been set forth in the foregoing description, together with :
details of the structure and function of the invention, and the novel features thereof are pointed out in the appended claims.
The disclosure, ho~.ever, is illustrative only" and changes may be made in detail, especially in ma~ters of shape, size, and arrange-ment of parts, ~ithin the principle of the invention, to the full . :
extent indicated by the broad general meaning of the terms in ;~ ~hich. the appended claims are expressed.
;, ~ '' ' ,~. ',' ;' ''~, `;
, :,~"
.. ;~.
;,''` '';' ::: .
`~'~',.
, ' . .. ~
' ., - 18 - .
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of treating a bounded body of water with a propeller type aerator comprising the steps of:
(a) 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;
(b) placing each of said aerators in the bounded body of water with said propeller and tube end adjacent thereto below the top surface of said water and with the longi-tudinal axis of each aerator disposed at an angle below horizontal;
(c) driving the aerators to create individual flow patterns around each of the aerators;
(d) 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, (e) injecting oxygen through said tube into the body of water adjacent said propeller at a rate greater than 1 pound of oxygen per horsepower-hour; and (f) inducing by rotating the propellers of said aerators said closed overall flow pattern at an average linear velocity in a generally horizontal direction through a cross section to flow at least 0.25 feet per second.
(a) 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;
(b) placing each of said aerators in the bounded body of water with said propeller and tube end adjacent thereto below the top surface of said water and with the longi-tudinal axis of each aerator disposed at an angle below horizontal;
(c) driving the aerators to create individual flow patterns around each of the aerators;
(d) 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, (e) injecting oxygen through said tube into the body of water adjacent said propeller at a rate greater than 1 pound of oxygen per horsepower-hour; and (f) inducing by rotating the propellers of said aerators said closed overall flow pattern at an average linear velocity in a generally horizontal direction through a cross section to flow at least 0.25 feet per second.
2. A method in accordance with claim 1 wherein step (e) includes injecting oxygen at a rate greater than 2.0 lbs. of oxygen per horsepower-hour and step (f) includes inducing said closed overall flow pattern at a linear velocity greater than 0.5 feet per second.
- Page 1 of Claims -
- Page 1 of Claims -
3. A method in accordance with claim 1 wherein step (f) includes inducing said closed overall flow pattern by driving the propellers of said aerators in the bounded body of water at less than 0.5 horsepower per 1,000 cubic feet of water in said bounded body of water.
4. A method in accordance with claim 3 wherein step (f) includes inducing said closed overall flow pattern by driving the propeller of said aerator in the bounded body of water at less than 0.1 horsepower per 1,000 cubic feet of water in said bounded body of water.
5. A method in accordance with claim 1 or 2 wherein step (f) includes maintaining said linear velocity to a depth of at least ten feet in said body of water.
6. A method in accordance with claim 1 wherein step (b) includes placing each aerator with said longitudinal axis at an angle between 12 degrees and 25 degrees with respect to the horizontal.
7. A method in accordance with claim 6 wherein said angle is set at substantially 22 degrees with respect to the horizontal.
8. A method in accordance with claim 1 wherein step (d) includes arranging said plurality of aerators to form a plurality of said larger closed overall flow patterns.
9. A method of treating a bounded body of water with a propeller type aerator comprising the steps of:
- Page 2 of Claims -(a) 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 said ends, said propeller being rotatably driven and said end of the tube adjacent the propeller including means for injecting air into the water;
(b) placing each of said aerators into a bounded body of water with said propeller and tube end adjacent thereto below the top surface of said water and with the longi-tudinal axis of each aerator disposed at an angle below the horizontal;
(c) arranging and driving a first of said aerators to induce a first fluid flow path about said first aerator, said first fluid flow path having forward horizontal flow vectors in a direction forward of the propeller of said first aerator, negative horizontal flow vectors in a direc-tion toward the propeller of said first aerator from an area rearward of said last-mentioned propeller, and a diffuse horizontal flow field interconnecting the forward and negative flow vectors;
(d) arranging and driving a second of said aerators to induce a second fluid flow path about said second aerator, said second fluid flow path having forward hori-zontal flow vectors in a direction forward of the propeller of said second aerator, negative horizontal flow vectors in a direction toward the propeller of said second aerator from an area rearward of said last-mentioned propeller, and a diffuse horizontal flow field interconnecting the forward and negative flow vectors of said second fluid flow path;
and - Page 3 of Claims -(e) disposing said first aerator relative to said second aerator so that at least some of the negative flow vectors of said second aerator link with at least some of the forward flow vectors of said first aerator to create an overall flow path in the general direction of the forward flow vectors of said first and second aerators.
- Page 2 of Claims -(a) 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 said ends, said propeller being rotatably driven and said end of the tube adjacent the propeller including means for injecting air into the water;
(b) placing each of said aerators into a bounded body of water with said propeller and tube end adjacent thereto below the top surface of said water and with the longi-tudinal axis of each aerator disposed at an angle below the horizontal;
(c) arranging and driving a first of said aerators to induce a first fluid flow path about said first aerator, said first fluid flow path having forward horizontal flow vectors in a direction forward of the propeller of said first aerator, negative horizontal flow vectors in a direc-tion toward the propeller of said first aerator from an area rearward of said last-mentioned propeller, and a diffuse horizontal flow field interconnecting the forward and negative flow vectors;
(d) arranging and driving a second of said aerators to induce a second fluid flow path about said second aerator, said second fluid flow path having forward hori-zontal flow vectors in a direction forward of the propeller of said second aerator, negative horizontal flow vectors in a direction toward the propeller of said second aerator from an area rearward of said last-mentioned propeller, and a diffuse horizontal flow field interconnecting the forward and negative flow vectors of said second fluid flow path;
and - Page 3 of Claims -(e) disposing said first aerator relative to said second aerator so that at least some of the negative flow vectors of said second aerator link with at least some of the forward flow vectors of said first aerator to create an overall flow path in the general direction of the forward flow vectors of said first and second aerators.
10. A method in accordance with claim 9 including the steps of:
(f) injecting oxygen from the ambient air through the tubes of said aerators into the body of water at a rate greater than 1 pound of oxygen per horsepower-hour; and (g) inducing by means of the propellers of said aerators the overall flow path of the water having an aver-age linear velocity through a cross-section to flow at least 0.25 feet per second.
(f) injecting oxygen from the ambient air through the tubes of said aerators into the body of water at a rate greater than 1 pound of oxygen per horsepower-hour; and (g) inducing by means of the propellers of said aerators the overall flow path of the water having an aver-age linear velocity through a cross-section to flow at least 0.25 feet per second.
11. A method in accordance with claim 10 wherein step (f?
includes injecting oxygen at a rate greater than 2.5 pounds of oxygen per horsepower-hour and step (c) includes inducing said overall flow path of water at a linear velocity greater than 0.5 feet per second.
includes injecting oxygen at a rate greater than 2.5 pounds of oxygen per horsepower-hour and step (c) includes inducing said overall flow path of water at a linear velocity greater than 0.5 feet per second.
12. A method in accordance with claim 11 wherein step (g) includes inducing said overall flow path of water by driving the propellers of said plurality, of aerators in the body of water at less than 0.5 horsepower per 1,000 cubic feet of water in said body of water.
- Page 4 of Claims -
- Page 4 of Claims -
13. A method in accordance with claim 10 including the steps of:
(h) arranging and driving a series of additional aerators to induce a fluid flow path about each additional aerator, each of said last-mentioned fluid flow paths having forward horizontal flow vectors in a direction forward of the propeller of an associated aerator, nega-tive horizontal flow vectors in a direction toward the propeller of said associated aerator from an area rearward of said last-mentioned propeller, and a diffuse horizontal flow field interconnecting the last-mentioned forward and negative flow vectors; and (i) disposing said series of additional aerators and said first and second aerators to create a closed overall flow path by linking some of the negative and forward flow vectors of successively. disposed aerators
(h) arranging and driving a series of additional aerators to induce a fluid flow path about each additional aerator, each of said last-mentioned fluid flow paths having forward horizontal flow vectors in a direction forward of the propeller of an associated aerator, nega-tive horizontal flow vectors in a direction toward the propeller of said associated aerator from an area rearward of said last-mentioned propeller, and a diffuse horizontal flow field interconnecting the last-mentioned forward and negative flow vectors; and (i) disposing said series of additional aerators and said first and second aerators to create a closed overall flow path by linking some of the negative and forward flow vectors of successively. disposed aerators
14. A method in accordance with claim 13 including the steps of:
(j) providing at least a second set of a plurality of propeller type aerators; and (k) performing steps (a), (b), (c), (d), (e), (h) and (i) with said second set of aerators to create at least a second closed overall flow path in the bounded body of water adjacent to and separate from the first closed overall flow path.
(j) providing at least a second set of a plurality of propeller type aerators; and (k) performing steps (a), (b), (c), (d), (e), (h) and (i) with said second set of aerators to create at least a second closed overall flow path in the bounded body of water adjacent to and separate from the first closed overall flow path.
15. A method in accordance with claim 13 including the steps of:
(1) providing an additional set of a plurality of propeller type aerators;
- Page 5 of Claims -(m) performing steps (a), (b), (c), (d), (e), (h) and (i) with said additional set of aerators to create an addi-tional closed overall path within the first closed overall flow path.
(1) providing an additional set of a plurality of propeller type aerators;
- Page 5 of Claims -(m) performing steps (a), (b), (c), (d), (e), (h) and (i) with said additional set of aerators to create an addi-tional closed overall path within the first closed overall flow path.
16. A method in accordance with claim 15 including the step of:
(n) displacing at least one of the aerators of said additional set out of alignment with the additional closed overall flow path toward the center of the additional closed overall flow path to create a sub-flow path for reducing the tendency of formation of a void flow area in the center of said additional closed overall flow path.
(n) displacing at least one of the aerators of said additional set out of alignment with the additional closed overall flow path toward the center of the additional closed overall flow path to create a sub-flow path for reducing the tendency of formation of a void flow area in the center of said additional closed overall flow path.
17. A method in accordance with claim 13 including the step of:
(o) displacing at least one of the aerators of the series of aerators nut of alignment with the closed overall flow path toward the center of the closed overall flow path to create a subflow path for reducing the tendency of formation of a void flow area in the center of said closed overall flow path.
- Page 6 of Claims -
(o) displacing at least one of the aerators of the series of aerators nut of alignment with the closed overall flow path toward the center of the closed overall flow path to create a subflow path for reducing the tendency of formation of a void flow area in the center of said closed overall flow path.
- Page 6 of Claims -
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US93441278A | 1978-08-17 | 1978-08-17 | |
| US934,412 | 1978-08-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1135883A true CA1135883A (en) | 1982-11-16 |
Family
ID=25465523
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000333866A Expired CA1135883A (en) | 1978-08-17 | 1979-08-16 | Method of treating water |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0020388A1 (en) |
| JP (1) | JPH0314520B2 (en) |
| CA (1) | CA1135883A (en) |
| DE (1) | DE2953063C1 (en) |
| GB (1) | GB2058593B (en) |
| WO (1) | WO1980000435A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3434114C2 (en) * | 1984-09-17 | 1994-12-01 | Ekato Ind Anlagen Verwalt | Fumigation device for absorber tanks in wet flue gas desulfurization |
| AU2002224231B2 (en) * | 2000-11-08 | 2006-10-12 | Philadelphia Mixing Solutions, A Division Of Philadelphia Gear Corporation | Improved aerator and mixer |
| NZ528434A (en) * | 2003-09-24 | 2005-07-29 | Philadelphia Mixing Solutions | Improved aerator and mixer |
| CN115432836B (en) * | 2022-09-09 | 2023-09-29 | 长江生态环保集团有限公司 | Uniform aeration robot and track planning method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2116023A (en) * | 1936-12-31 | 1938-05-03 | Stanislous J Gwidt | Aerator |
| US3614072A (en) * | 1969-01-02 | 1971-10-19 | James H Brodie | Hydraulic flow inducer |
| US3778233A (en) * | 1971-04-20 | 1973-12-11 | Fairfield Eng Manuf Co | Apparatus for liquid composting |
| AT335381B (en) * | 1974-01-23 | 1977-03-10 | Hubert Fuchs | MIXING UNIT FOR GASING AND ROLLING LIQUIDS - ESPECIALLY FOR MIXING AIR INTO FREE WATERS OR IN WATER IN LARGE-SCALE TANK |
| DE2505898A1 (en) * | 1974-02-13 | 1975-08-14 | Nebiker Hans Ag | DEVICE FOR VENTILATION OF AN AQUATIC SUSPENSION TENDING TO FLOATING CEILINGS AND FOAMING |
| US4070279A (en) * | 1976-09-13 | 1978-01-24 | Armstrong Edward T | Eductor for dissolving gases in liquids |
-
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 GB GB8011124A patent/GB2058593B/en not_active Expired
- 1979-08-17 DE DE2953063A patent/DE2953063C1/en not_active Expired
- 1979-08-17 JP JP50138779A patent/JPH0314520B2/ja not_active Expired - Lifetime
-
1980
- 1980-03-25 EP EP79901064A patent/EP0020388A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB2058593B (en) | 1983-02-09 |
| EP0020388A1 (en) | 1981-01-07 |
| DE2953063C1 (en) | 1985-09-26 |
| JPS55500581A (en) | 1980-09-04 |
| GB2058593A (en) | 1981-04-15 |
| WO1980000435A1 (en) | 1980-03-20 |
| JPH0314520B2 (en) | 1991-02-26 |
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