CA1194623A - Method and apparatus for treating organic wastewater - Google Patents
Method and apparatus for treating organic wastewaterInfo
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- CA1194623A CA1194623A CA000432733A CA432733A CA1194623A CA 1194623 A CA1194623 A CA 1194623A CA 000432733 A CA000432733 A CA 000432733A CA 432733 A CA432733 A CA 432733A CA 1194623 A CA1194623 A CA 1194623A
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- 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
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Abstract
Method And Apparatus for Treating Organic Wastewater Richard W. Heil, Clarendon Hills, IL and Thomas A. Rose, La Grange, IL
Abstract of the Disclosures A method and apparatus for treating a continuous stream of organic wastewater using highly concentrated activated sludge (10,000 mg/? MLSS), elevated atmospheric pressure, and high levels of dissolved oxygen. The apparatus consists of three pressurized vessels linked in series by piping, and maintained at equal pressure by means of a common manifold.
The first vessel receives the mixed liquor consisting of macerated sewage and return activated sludge and thoroughly aerates it with diffused air bubbles. The liquor then flows by gravity into the second pressurized vessel where flocculation and further aeration occur.
From an overflow/transfer box in vessel 2, the liquor flows by gravity into the bottom tier of the third vessel which functions as a cyclone seperator. The concentrate is drawn from the bottom of the vessel by a return sludge pump and recycled to the first vessel. The centrate rises into the upper tier of the third vessel where it is clarified and discharged as tertiary quality effluent.
Abstract of the Disclosures A method and apparatus for treating a continuous stream of organic wastewater using highly concentrated activated sludge (10,000 mg/? MLSS), elevated atmospheric pressure, and high levels of dissolved oxygen. The apparatus consists of three pressurized vessels linked in series by piping, and maintained at equal pressure by means of a common manifold.
The first vessel receives the mixed liquor consisting of macerated sewage and return activated sludge and thoroughly aerates it with diffused air bubbles. The liquor then flows by gravity into the second pressurized vessel where flocculation and further aeration occur.
From an overflow/transfer box in vessel 2, the liquor flows by gravity into the bottom tier of the third vessel which functions as a cyclone seperator. The concentrate is drawn from the bottom of the vessel by a return sludge pump and recycled to the first vessel. The centrate rises into the upper tier of the third vessel where it is clarified and discharged as tertiary quality effluent.
Description
Princiea!s Upon ~hich the Invention is Based Parameters for the invention derive from experi~ce gained in operating a 43 year old activated sludge plant that handles peak wastewater flows of up to 1440 MGD (million gallons per day~O In l9Jl, just prior to commencement of a vigorous program to optimize quality~ the treated eff?uent for the plant contained an average BOD5 of 23 mg/Q~ 30 mg/~ suspended solids and 11.8 mg/Q ammoriaO
Since then9 treatment quality has been steadily impr~ved~ Last year ~1~81)~ the treated effluent contained a residual impurity of only 6 mg/Q BOD5, 6 mg/Q suspended solids and 1.4 mg/~ ammonia.
Lessons derived thereby are as follows:
(1) Maintain a minimum dissolved oxygen (D.O.) content of 4 mg/~
throughout the treatment system. (In our invention, pressuri~ation enhances oxygen transfer and helps maintain high levels of D.O.)
Since then9 treatment quality has been steadily impr~ved~ Last year ~1~81)~ the treated effluent contained a residual impurity of only 6 mg/Q BOD5, 6 mg/Q suspended solids and 1.4 mg/~ ammonia.
Lessons derived thereby are as follows:
(1) Maintain a minimum dissolved oxygen (D.O.) content of 4 mg/~
throughout the treatment system. (In our invention, pressuri~ation enhances oxygen transfer and helps maintain high levels of D.O.)
(2) Avoid degredation of activated sludge by minimizing its retention time in the clarifier. (In our invention, the sludge floc is removed from the separator/clarifier vessel within eight minutes.)
(3) Food to micro-organism ratio (F:M ratio) should be kept under 0.2, wherein "food" is computed as pounds per day of wastewater BOD5, and "micro-organisms" are computed as total dry pounds of mixed liquor suspended solids (MLSS). To : stay within that ratio, mixed liquor in the 43 year old plant is maintained at a concentration of 2500 mg/Q MLSS during the summer, and upwards of 3500 mg/Q MLSS in the winter when bacterial action is slow. (Our invention is designed to safe1y handle lO,OOQ mg/ Q MLSS)
(4) Provide ample mixing action to enhance assimilation of the waste by the floc, restricting sedimentation of solids to the clarifier units. (In our invention, the!location of air diffuser heads, the shape of the process vessels, the rate of sludge return, and piping arrangements combine to provide excellent mixing.)
(5) Prevent excessive turbulence so as to avoid tearing the fragile bacteria floc. (In our invention there is a gentle gravity flow between the three process vessels. The only place in the systPm with substantial turbulence is in the sludge return pump.) i6~3 In summation, we learned from the old treatment plant that:
"high quality biological treatment requires a favorable environment wherein useful organisms proliferate and undesirable types regress."
Existing Limitations in Treatment Facilities In theory, the size requirement of an activated sludge aeration tank is inversely proportional to the concentration of a mixed liquor. In other words, if an aeration tank is designed to operate at a concentration of 5000 mg/~ MLSS instead of 2500 mg/~, its size can be reduced by half and still have the same capacity. Due to certain practical limitations however, it is extremely difficult to operate at concentrations above 4000 mg/~. The problems have been:
(a) Poor Ox~ygen Transfer Efficiency:
The oxygen demand of liquor concentrations higher than 4000 mg/Q MLSS usually exceed the capacity of the aeration system.
The two exceptions to this limitation have been pure oxygen systems (which offer good transfer efficiency but are plagued with mechanical problems) and pressurized aeration systems . (which tend to be difficult to regulate and service, as per experience with U.S. Patent #3,560,376 by R. W. Heil). Our invention rectifies this problem with a simplified pressure system that is self regulating and easy to service.
(b) Vulnerability to Upset: /!
Conventional clarifiers are easily upset when they are fed high concentrations of mixed liquor. The sludge blanket may rise too fast and/or density currents may sweep floc over the effluent wier.
This vulnerability to upset is due to design compromise wherein three (not altogether compatible) functions are performed in the clarifier:
1. flocculation of the micro-organisms.
2. separation and removal of the effluent.
3. Concentration and return of the micro-organisms.
Performances of all these functions within one compart-ment necessitates use of a relatively large surface area and substantial holding capacity. Above all, the inventory of solids (micro-organsims) must be managed with great care. If not retained long enough, the return sludge will be dilute and thus too voluminous for the system to handle. However, if the solids are retained too long, the dissolved oxygen will be depleted and the micro-organisms deteriorate.
In our invention9 vulnerability to clarifier upset is resolved by handling each of the above functions in separate specialized compartments.
(c) Voluminous Clarifier Sizes:
To function properly, conventional clarifiers require 100 substantial depth and surface area. Much of the volume provided is used for dissipation of density currents and for transition space between function zones. The small diameter gravity clarifiers are especially plagued by poor settling performance (not enough volume tc dissipate density currents). Large 105 clarifiers perform better but do not lend the~selves to a pressurized treatment system, being too difficult and too expensive to enclose. As a result, most préssurized aeration systems use an open flotation tank for separation of sludge and effluent (as in U.S. Patent #3,4443076 by Sekikawa et al.) 110 Flotation separators have the advantage of compactness, low capital cost9 qwick separation and high solids concentration.
However, upon release of a pressurized mixed liquor to atmospheric conditions the explosive release of dissolved gas tends to tear-up the organic floc and produce a muddy effluent.
115 Our invention solves these problems with a two stage pressurized separator/clarifier unit.
(d) Inadequate Monitoring of MLSS
To maintain a proper concentration of activated sludge in the aeration tanks, a treatment plant operator needs to 120 know his mixed liquor suspended solids (MLSS). With this information, he can determine the rate at which the sludge should be wasted to maintain d proper concen~ration. If his waste rate is too low, the solids concentration will become excessive and overflow the clarifier. If too many solids 125 are wasted, treatment quality declines because of insufficient bacteria to assimilate the waste.
The operator can draw a sample and determine the MLSS by labora~ory analysis, but the procedure is slow and requires considerable skill and equipment. Alternatively, there are 130 various commercial denisty meters that can provide an approximation of the MLSS on a continuous basis. Most of them employ some means of penetrating the MLSS with an energy source (sonic waves, light beams, gamma rays, etc.) and measuring the attenuation. Unfortunately, such meters require 135 frequent calibration, their cost is high and their reliability is low.
In our invention we utilize the rheol~gtcal properties of the sludge to obtain an instant, close approximation of MLSS. Unlike exi~ting density meters, the rheological method 140 is low in first C05t and upkeep.
Rheologically, activated sludge is a "thixotropic pseudo-plastic"O Simply put, its flow behavior is more like tooth paste than water. The term "thixotropic" indicates it stiffens or gels when at rest, but breaks down and becomes 145 fluid when subjected to aggitation or high shear stress.
In our invention, the sludge is kept in constant motion (offerin~ no opportunity for gel) therefore thixotropy can be ignored.
As the MLSS concentration of activated increases, it 150 becomes increasingly resistive to flow. If the sludge is pumped into a small tube of fixed length and diameter, and maintained at a constant pressure differential; its velocity will be an inverse function of MLSS concentration.
When velocity (ordinate) is plotted on a graph as a function 155 of MLSS ~abscissa), the resulting curve is nearly horizontal at low concentrations of MLSS, descending in a downward spiral as the MLSS increases. At some critical concentration, flow velocity will cease altogether. If the SVI ~sludge volume index) of the sludge is relatively constant, the graph 160 is dependably repeatable.
~ith such a graph, a treatment plant operator can readily determine his MLSS simply by reading a magnetic flow meter.
Furthermore he need concern himself with only two velocity limits, minirnum (indicating upper permissible concentration), 165 and maximum (indicating the thinnest permissible concentration).
Due to very high dissolved oxygen levels, our invention provides unusually low and fairly uniform SVI's (ranging from about 40 to 60). Thus the relationship betwfen rheological behavior and MLSS concentration is dependably consistent.
170 Furthermore, the only instrument or sensor required for our solids monitor is a magnetic flow meter, and experience has shown such meters to be one of the few instruments used in pollution control that can give maintenance free perfor-mance in a troublesome fluid like sewage sludge.
175 Design ObJect _es The object of our invention is to provide a treatment process for organic wastewater that is compact (relative ~o capacity), simple to construct and operate, is energy efficient, requires little maintenance, and achieves tertiary quality.
180 To accomplish this, all major components of the apparatus are pressurized equally (upwards of 35 psi). For ease of maintenance, all moving parts are placed outside the pressure vessels, and the interior of the vessels are clear of anything that can clog or foul with slime growth. An air diffuser head in each of the aeration vessels provides 185 mixing and Dromotes oxygen transfer.
The size of the clarifier unit has been minimized by providing a unique two tier cyclone separator that utilizes density currents to affect rapid centrifugal separation. Solids are drawn from the bottom (as return sludge) and the clear centrate is displaced by 150 gravity into the vortex, where it flows upward into the top tier for final clarification. Detention time for the sludge is only eight minutes, thereby eliminating the risk of oxygen depletion. Of key importance, the separator-clarifier vessel's compact size substantially reduces the cost for pressurized containment.
195 Within the entire process, there is only one component that causesenough turbulence to damage the sludge floc, namely the return sludge pump. However, due to it's location in the process system, the floc has ample opportunity to recover. It therefore enters the separator unit in excellent condition, ideal for effecting rapid separation.
200 The rate of return sludge in our invention (300% of the design capacity flow) is unnusually high, however use of a 'constant high return flow provides a number of advantages:
(1) Aids in maintaining a gentle cyclone action within the separator unit.
205 (27 Minimizes sludge detentio, ~ime, thus reducing oxygen depletion in the clarifier.
(37 Minimizes the amount of sludge thickening needed to sustain high MLSS concentrations.
(4) Self regulates the thickening and removal process, thereby 2lO eliminating need for costly sludge blanket control.
(5) ~romotes better mixing action.
Summary According to an aspect of the invention there is provided the method of treating organic waste water with activated sludge comprising the steps of: establish~
iny an enclosed continuous flow way for the organic waste water and the activated sludge in a mixed liquor form including several aeration chambers, and a separator chamber that are air pressurized to a predetermined pres-sure, that contain organic waste water and activated sludge, and that are consecutively connected in a continuous flow circuit through the aeration chambers, -the separator chamber, and return Elow to the one aeration chamber, mi.~ing acti~ated sludge and fresh organic waste water in the return flow, passing the return flow into the one aeration chamber adjacent the lower end thereof, d~sing the hody of the liquor of the one aeration chamber with air in diffused bubble form for flocculating and air sa~uration of the sludge, passing continuously from the liquor body a flow of the liquor to a subsequent of the aeration chambers having a second liquor body while diffusing air into the second body from the lower end of same for pro-viding a liquor flow in which the flocculated sludge has assimilated the organic waste in the liquor flow, con-tinuously passing in a gravity f10W to the separator chamber the organic waste assimilated liquor flow; and establishing and maintaining in the separator chamber and in the organic waste assimilated liquor flow a cyclone separating action effecting centrifugal force and gravity induced settling out of the sludge flow thereof to provide the return flow, and a rising eEfluen-t centrate flo~, continuously clarifying and discharging the cen-trate flow as tertiary quali-ty effluent, and continuo-lsly pumping t'" - 7a -the return flow to effect the mixing and the first mentioned passing steps.
According -to a further aspect of the inven-tion there is provided an apparatus :Eor continuously treating organic waste water with activated sludye as a mixed liquor, the apparatus comprising: first and second vessels disposed at substantially ~he same horizontal level respectively defining first ~nd second aeration chambers, a third vessel disposed substantially at the horizontal level and defining a separator chamber, the first and second vessels containing the liquor up to a predetermined horizontal level, therein in each, with the first vessel being in liquid flow communication with the second vessel below the predetermined level, the second vessel being connected to the -third vessel chamber ~or gravity induced liquid flow of the liquor thereinto from the second vessel by condui-t r.~eans extending from about the predetermined level of the second ~essel to a lower level in the third vessel for imparting a velocity head to the liquor flow in the separator, the third vessel defining at its lower end a funnelli.n~ liquid flow discharge outlet and defining an internally centered frusto-conical divider baffle that depends in circumambient relation about the third chamber from above to below the lower level thereof and defines at its lower end a liquid upflow port, the third vessel above the baffle having means for effluent draw off therefrom, return conduit means connected between the third ~ressel. outle-t and -the lower end of the first vessel for returning slud~e from the separator chamber to the Eirst chamber includin~
pump means, inlet conduit means connected to the ret.urn condui-t means adjacent the first c`namber for supplyin~
- 7b -mab/ J, ~
organic waste water thereto, the chambers being manifold connected at their upper ends and being cor~only pressurized at a level in range of up to about 35 psig 7 fixst means for diffusing air into the liquor of the first chamber at the lower end of the first chamber~
and second means for diffusing air into the liquor of the second chamber at the lower end of the second chamber, the liquor concentration in the first and second chambers being about 10,000 mg/l MLSS, the pump means and the return conduit means effecting the return of the sludge therethrough at a rate approximating three hundred per-cent of the effluent draw off flow.
- 7c -mah~
Detailed Description Referring now to the drawing of the apparatus9 all standard components sho~ln~ such as thP valves, pumps, blower, air compressor 215 assembly, liquid level controller and piping (~,/hich are no-t des~ribed in the claims) are conven~ional and their uses and functions are well kno~n in the art.
The configuration shown in Figure #l is sized for a sewage strength of 200 rng/~ BOD5 and a treatment rate of 12,000 gallons per 220 day (gpd). The normal mixed liquor concentration will be 10,000 mg/~ SS, making a food to micro-organism (F:M) ratio of 0.20 Sizing and dimensions are only approximate and could be scaled upward or downward, depending on the strength and quantity of sewage to be treated.
225 Organic waste water that has been screened and degritted (or macerated) is pumped cont;nuously or intermittently (as needed~
into the aerator unit (vessel #l) by means of a single stage centrifugal pump 4, through a flap gate check valve 5 into the re~urn sludge pipeline 6, where it intermixes with the return s1udge 230 and enters into vessel #1.
Mixed liquor ~return sludge mixed with incoming sewage) from cDnduit 6~ is dosed with a continuous stream of air bubbles rising from aerator head 7 located in the bottom of pressure ~essel #1. The diffused air bubbles 8 became attached to ~he sludge floc and 235 bouy it upward to the interface of the air dome 9, where the floc is further saturated with air before sinking downward along the walls of vessel #1.
Oxygen trans-~r to the mixed liquor occurs through diffusion of air bubbles from aerator head 7 into the liquor and from a rolling 240 interface of the liquor with the air dome 9. Elevated pressure within the containment vessel #l (up to 35 pounds per square inch) provides an extremely efficient driving force for transfer of oxygen into the mixed liguor. The mixed liquor in vessel ~1 cycles continuously ~ - 8 -upward at the center and downward near the perimeter, eventually flowing 245 out (by gravity) ~hrough conduit 10 into aeration vessel #2.
As receiving unit for sewage influent, the first stage aerator (vessel #l) sustains the highest oxygen demand. After being partially satiated in the first stage, the oxygen demand of the mixed 1iq~or tapers off sharply in the second stage unit (vessel #2). In accordance 2~0 therewith~ we have provided an adjustable throttle valve 11 on air supply line 34 to air diffuser head 12 in vessel #2. Whereas full air flow to diffuser head 7 creates a vigorous boil in vessel #l; the throttled air supply to diffuser head 12 produces only a gentle rolling action that enhances flocculation yet is sufficient to satiate 255 oxygen demand. When the sludge floc finally leaves vessel #2, it is strong and dense, settles easily, and has virtually assimilated all the organic waste in the wastewater.
The level of mixed liquor in vessels #1 and #2 is controlled by the overflow/transfer box 13 (located in vessel #2) from whence the fully 260 aerated mixed liquor enters conduit 14 and flows into the cyclone separator compartment 15 of vessel #3. The dif~erential head between liquid levels in vessels #2 and #3 imparts a velocity head to the flow in cyclone separator compartment 15. The mixed liquor spins in a descending spiral along the wall of the bottom cone. The floc (being 265 heavier than water) is spun to the outside and the centrate (consisting of water and pin floc) is displaced to the center (thé vortex of the cyclone). The heavy sludge floc descends to the bottom of the cone where it is continuously drawn off into suction line 16 of the sludge return pump 26.
270 Centrate f-~", the v.ortex flows up through opening 18 at the bottom of the upper cone 20 and flows into the settling compartment 19 of vessel ~3. In the settling compartment 19, the pin floc deposits out along the sides of the upper cone 20 and slides downward through the opening 18 into the lower chamber and is withdrawn with the return 275 sludge 16. The effluent spills over V-notch weirs into four radial draw-off troughs 21. Thence into a collec~or pocket 22, to a discharge pipe 23, past valve 24 which is regulated by a conventional liquid level controller 25 and discharge.
Return sludge 16 from vessel #3 is drawn into a conventional 280 volute pump 26 and pumped through check valve 28, into conduit 6, thence back into aeration vessel #1. Pump 26 is designed for a 300% volume of return sludge (300% of treatment flow capacity~. In the specific example shown on the drawing, the design capacity of the return sludge pump is (12,000 gpd) X (300/100) = 36,000 gpd which is 25 gpm (gallons per 285 minute). The static head against which it pumps is relatively constant,namely the elevation difference between the crest of weir 13 in vessel #2 and the crest of effluent weir 21 in vessel #3, plus a small dynamic head loss in pipe 6.
Supply air for the aeration bubbler heads 7 and 12 and air dome's 9 is 290 provided by a rotary compressor 31 capable of achieving pressures of up to 35 psi. In addition to a low volume of fresh supply air from compressor 31, there is a high volume of recycle air from air manifold 35 to diffuser heads 7 and 12 via the feed lines 34. Because blower 32 draws previously pressurized air from manifold 35, it need only 295 develop enough pressure to overcome the differential liquid head in vessels #l and #3, about 4 psi, thus providing high volume air movement at a minimum expenditure of energy. The higher pressure rotary com-pressor (35 psi) accordingly need supply only enough volume of fresh air to satisfy oxygen up-take plus a small allowance For wa~tage.
300 Pressure manifold 35 prsvides equalization of air pressure betweenall three pressure vessels #1, #2, #3, thereby creating a comlnon atmosphere within the process system in which the liquid can move by gravity flow without necessitating complex valve controls. Spent air in the system is exhausted through pressure relief valve 36 which 305 also serves to regulate air pre~sure in the system.
Approximate MLSS determinations are obtained by taking readings from the modified tubular viscometer 27 and extrapolating from a chart.
The viscometer consists of only two components: a 1~2 inch diameter by 30 foot long tube, and a 1~2 inch magnetic flow meter connected near 310 the mid-point of the tube. The 1~2 inch tube is about the minimum practical diameter that can handle sludge without plugging-up. The length of tube selected provides maximum sensi~ivity to change in MLSS (for the given diameter of pipe, differential head, and working range of MLSS).
315 As shown in the drawing, one end of the tube is connected to the discharge pipe 6 of sludge return pump 26 and the other end is connected to the suction line 16 of the return pump 26. The differential head between the two connection points is determined by the differential in liquid levels between vessels #2 and #3 plus the head losses in 320 pipes 6, lO, and 16. For reasons previously stated, the differential head across pump 26 is relatively constant, therefore all variations in flo~ rate through the meter 27 are due to changes in flow resistance of the return sludge, which result from changes in MLSS. By taking four or more samples of different return sludge concentrations, 325 recording their meter readings and obtaining a lab analysis of the suspended solids concentration, a graph is produced by plotting the meter readings (ordinate) as a function of suspended solids (abscissa).
The plot points will be interconnected with a curved line that can be used to extrapolate suspended solids from future mete~ readings.
330 The meter measures only the return sludge suspended solids, not the mixed liquor suspended solids MLSS. However, there being a continuous fixed rate of return sludge (300% of influent design capacity), the MLSS itself will merely be 3/4's of the return sludge SS. This calculation is slightly in error when the system is 335 operating at less than design capacity, but will be adequate for control purposes.
Sludge wasting is accomplished by cracking open valve 30 when magnetic flow meter 27 reaches its mirlimum allowable reading (indicating maximum allowable concentration of MLSS!. Wasting is continued until 340 the meter reading rises to the allowable maximum (indicating minimum allowable concentration of MLSS)~ whereupon waste valve 30 is either throttled or closed completelyO The waste system can be either.operated manually by -the trea~ment operator, or au~omatically with a conventional micro-processo~f~ ~rogranlmed ~o respor,d to limit signals ~rom the 345 magnetic flow meter~
The curved junction of pipe 6 with waste line 29 provides a means of selectively extracting grit and other heavy particles from the sludge recirculation system. Due to the curve in the junction, the heavy particles continue tangentially into the waste line draw-off stub 29 350 displacing any sluGge floc that become trapped thereinO Whenever valve 30 is opened, the captured grit flows out with the waste sludge.
-lla-
"high quality biological treatment requires a favorable environment wherein useful organisms proliferate and undesirable types regress."
Existing Limitations in Treatment Facilities In theory, the size requirement of an activated sludge aeration tank is inversely proportional to the concentration of a mixed liquor. In other words, if an aeration tank is designed to operate at a concentration of 5000 mg/~ MLSS instead of 2500 mg/~, its size can be reduced by half and still have the same capacity. Due to certain practical limitations however, it is extremely difficult to operate at concentrations above 4000 mg/~. The problems have been:
(a) Poor Ox~ygen Transfer Efficiency:
The oxygen demand of liquor concentrations higher than 4000 mg/Q MLSS usually exceed the capacity of the aeration system.
The two exceptions to this limitation have been pure oxygen systems (which offer good transfer efficiency but are plagued with mechanical problems) and pressurized aeration systems . (which tend to be difficult to regulate and service, as per experience with U.S. Patent #3,560,376 by R. W. Heil). Our invention rectifies this problem with a simplified pressure system that is self regulating and easy to service.
(b) Vulnerability to Upset: /!
Conventional clarifiers are easily upset when they are fed high concentrations of mixed liquor. The sludge blanket may rise too fast and/or density currents may sweep floc over the effluent wier.
This vulnerability to upset is due to design compromise wherein three (not altogether compatible) functions are performed in the clarifier:
1. flocculation of the micro-organisms.
2. separation and removal of the effluent.
3. Concentration and return of the micro-organisms.
Performances of all these functions within one compart-ment necessitates use of a relatively large surface area and substantial holding capacity. Above all, the inventory of solids (micro-organsims) must be managed with great care. If not retained long enough, the return sludge will be dilute and thus too voluminous for the system to handle. However, if the solids are retained too long, the dissolved oxygen will be depleted and the micro-organisms deteriorate.
In our invention9 vulnerability to clarifier upset is resolved by handling each of the above functions in separate specialized compartments.
(c) Voluminous Clarifier Sizes:
To function properly, conventional clarifiers require 100 substantial depth and surface area. Much of the volume provided is used for dissipation of density currents and for transition space between function zones. The small diameter gravity clarifiers are especially plagued by poor settling performance (not enough volume tc dissipate density currents). Large 105 clarifiers perform better but do not lend the~selves to a pressurized treatment system, being too difficult and too expensive to enclose. As a result, most préssurized aeration systems use an open flotation tank for separation of sludge and effluent (as in U.S. Patent #3,4443076 by Sekikawa et al.) 110 Flotation separators have the advantage of compactness, low capital cost9 qwick separation and high solids concentration.
However, upon release of a pressurized mixed liquor to atmospheric conditions the explosive release of dissolved gas tends to tear-up the organic floc and produce a muddy effluent.
115 Our invention solves these problems with a two stage pressurized separator/clarifier unit.
(d) Inadequate Monitoring of MLSS
To maintain a proper concentration of activated sludge in the aeration tanks, a treatment plant operator needs to 120 know his mixed liquor suspended solids (MLSS). With this information, he can determine the rate at which the sludge should be wasted to maintain d proper concen~ration. If his waste rate is too low, the solids concentration will become excessive and overflow the clarifier. If too many solids 125 are wasted, treatment quality declines because of insufficient bacteria to assimilate the waste.
The operator can draw a sample and determine the MLSS by labora~ory analysis, but the procedure is slow and requires considerable skill and equipment. Alternatively, there are 130 various commercial denisty meters that can provide an approximation of the MLSS on a continuous basis. Most of them employ some means of penetrating the MLSS with an energy source (sonic waves, light beams, gamma rays, etc.) and measuring the attenuation. Unfortunately, such meters require 135 frequent calibration, their cost is high and their reliability is low.
In our invention we utilize the rheol~gtcal properties of the sludge to obtain an instant, close approximation of MLSS. Unlike exi~ting density meters, the rheological method 140 is low in first C05t and upkeep.
Rheologically, activated sludge is a "thixotropic pseudo-plastic"O Simply put, its flow behavior is more like tooth paste than water. The term "thixotropic" indicates it stiffens or gels when at rest, but breaks down and becomes 145 fluid when subjected to aggitation or high shear stress.
In our invention, the sludge is kept in constant motion (offerin~ no opportunity for gel) therefore thixotropy can be ignored.
As the MLSS concentration of activated increases, it 150 becomes increasingly resistive to flow. If the sludge is pumped into a small tube of fixed length and diameter, and maintained at a constant pressure differential; its velocity will be an inverse function of MLSS concentration.
When velocity (ordinate) is plotted on a graph as a function 155 of MLSS ~abscissa), the resulting curve is nearly horizontal at low concentrations of MLSS, descending in a downward spiral as the MLSS increases. At some critical concentration, flow velocity will cease altogether. If the SVI ~sludge volume index) of the sludge is relatively constant, the graph 160 is dependably repeatable.
~ith such a graph, a treatment plant operator can readily determine his MLSS simply by reading a magnetic flow meter.
Furthermore he need concern himself with only two velocity limits, minirnum (indicating upper permissible concentration), 165 and maximum (indicating the thinnest permissible concentration).
Due to very high dissolved oxygen levels, our invention provides unusually low and fairly uniform SVI's (ranging from about 40 to 60). Thus the relationship betwfen rheological behavior and MLSS concentration is dependably consistent.
170 Furthermore, the only instrument or sensor required for our solids monitor is a magnetic flow meter, and experience has shown such meters to be one of the few instruments used in pollution control that can give maintenance free perfor-mance in a troublesome fluid like sewage sludge.
175 Design ObJect _es The object of our invention is to provide a treatment process for organic wastewater that is compact (relative ~o capacity), simple to construct and operate, is energy efficient, requires little maintenance, and achieves tertiary quality.
180 To accomplish this, all major components of the apparatus are pressurized equally (upwards of 35 psi). For ease of maintenance, all moving parts are placed outside the pressure vessels, and the interior of the vessels are clear of anything that can clog or foul with slime growth. An air diffuser head in each of the aeration vessels provides 185 mixing and Dromotes oxygen transfer.
The size of the clarifier unit has been minimized by providing a unique two tier cyclone separator that utilizes density currents to affect rapid centrifugal separation. Solids are drawn from the bottom (as return sludge) and the clear centrate is displaced by 150 gravity into the vortex, where it flows upward into the top tier for final clarification. Detention time for the sludge is only eight minutes, thereby eliminating the risk of oxygen depletion. Of key importance, the separator-clarifier vessel's compact size substantially reduces the cost for pressurized containment.
195 Within the entire process, there is only one component that causesenough turbulence to damage the sludge floc, namely the return sludge pump. However, due to it's location in the process system, the floc has ample opportunity to recover. It therefore enters the separator unit in excellent condition, ideal for effecting rapid separation.
200 The rate of return sludge in our invention (300% of the design capacity flow) is unnusually high, however use of a 'constant high return flow provides a number of advantages:
(1) Aids in maintaining a gentle cyclone action within the separator unit.
205 (27 Minimizes sludge detentio, ~ime, thus reducing oxygen depletion in the clarifier.
(37 Minimizes the amount of sludge thickening needed to sustain high MLSS concentrations.
(4) Self regulates the thickening and removal process, thereby 2lO eliminating need for costly sludge blanket control.
(5) ~romotes better mixing action.
Summary According to an aspect of the invention there is provided the method of treating organic waste water with activated sludge comprising the steps of: establish~
iny an enclosed continuous flow way for the organic waste water and the activated sludge in a mixed liquor form including several aeration chambers, and a separator chamber that are air pressurized to a predetermined pres-sure, that contain organic waste water and activated sludge, and that are consecutively connected in a continuous flow circuit through the aeration chambers, -the separator chamber, and return Elow to the one aeration chamber, mi.~ing acti~ated sludge and fresh organic waste water in the return flow, passing the return flow into the one aeration chamber adjacent the lower end thereof, d~sing the hody of the liquor of the one aeration chamber with air in diffused bubble form for flocculating and air sa~uration of the sludge, passing continuously from the liquor body a flow of the liquor to a subsequent of the aeration chambers having a second liquor body while diffusing air into the second body from the lower end of same for pro-viding a liquor flow in which the flocculated sludge has assimilated the organic waste in the liquor flow, con-tinuously passing in a gravity f10W to the separator chamber the organic waste assimilated liquor flow; and establishing and maintaining in the separator chamber and in the organic waste assimilated liquor flow a cyclone separating action effecting centrifugal force and gravity induced settling out of the sludge flow thereof to provide the return flow, and a rising eEfluen-t centrate flo~, continuously clarifying and discharging the cen-trate flow as tertiary quali-ty effluent, and continuo-lsly pumping t'" - 7a -the return flow to effect the mixing and the first mentioned passing steps.
According -to a further aspect of the inven-tion there is provided an apparatus :Eor continuously treating organic waste water with activated sludye as a mixed liquor, the apparatus comprising: first and second vessels disposed at substantially ~he same horizontal level respectively defining first ~nd second aeration chambers, a third vessel disposed substantially at the horizontal level and defining a separator chamber, the first and second vessels containing the liquor up to a predetermined horizontal level, therein in each, with the first vessel being in liquid flow communication with the second vessel below the predetermined level, the second vessel being connected to the -third vessel chamber ~or gravity induced liquid flow of the liquor thereinto from the second vessel by condui-t r.~eans extending from about the predetermined level of the second ~essel to a lower level in the third vessel for imparting a velocity head to the liquor flow in the separator, the third vessel defining at its lower end a funnelli.n~ liquid flow discharge outlet and defining an internally centered frusto-conical divider baffle that depends in circumambient relation about the third chamber from above to below the lower level thereof and defines at its lower end a liquid upflow port, the third vessel above the baffle having means for effluent draw off therefrom, return conduit means connected between the third ~ressel. outle-t and -the lower end of the first vessel for returning slud~e from the separator chamber to the Eirst chamber includin~
pump means, inlet conduit means connected to the ret.urn condui-t means adjacent the first c`namber for supplyin~
- 7b -mab/ J, ~
organic waste water thereto, the chambers being manifold connected at their upper ends and being cor~only pressurized at a level in range of up to about 35 psig 7 fixst means for diffusing air into the liquor of the first chamber at the lower end of the first chamber~
and second means for diffusing air into the liquor of the second chamber at the lower end of the second chamber, the liquor concentration in the first and second chambers being about 10,000 mg/l MLSS, the pump means and the return conduit means effecting the return of the sludge therethrough at a rate approximating three hundred per-cent of the effluent draw off flow.
- 7c -mah~
Detailed Description Referring now to the drawing of the apparatus9 all standard components sho~ln~ such as thP valves, pumps, blower, air compressor 215 assembly, liquid level controller and piping (~,/hich are no-t des~ribed in the claims) are conven~ional and their uses and functions are well kno~n in the art.
The configuration shown in Figure #l is sized for a sewage strength of 200 rng/~ BOD5 and a treatment rate of 12,000 gallons per 220 day (gpd). The normal mixed liquor concentration will be 10,000 mg/~ SS, making a food to micro-organism (F:M) ratio of 0.20 Sizing and dimensions are only approximate and could be scaled upward or downward, depending on the strength and quantity of sewage to be treated.
225 Organic waste water that has been screened and degritted (or macerated) is pumped cont;nuously or intermittently (as needed~
into the aerator unit (vessel #l) by means of a single stage centrifugal pump 4, through a flap gate check valve 5 into the re~urn sludge pipeline 6, where it intermixes with the return s1udge 230 and enters into vessel #1.
Mixed liquor ~return sludge mixed with incoming sewage) from cDnduit 6~ is dosed with a continuous stream of air bubbles rising from aerator head 7 located in the bottom of pressure ~essel #1. The diffused air bubbles 8 became attached to ~he sludge floc and 235 bouy it upward to the interface of the air dome 9, where the floc is further saturated with air before sinking downward along the walls of vessel #1.
Oxygen trans-~r to the mixed liquor occurs through diffusion of air bubbles from aerator head 7 into the liquor and from a rolling 240 interface of the liquor with the air dome 9. Elevated pressure within the containment vessel #l (up to 35 pounds per square inch) provides an extremely efficient driving force for transfer of oxygen into the mixed liguor. The mixed liquor in vessel ~1 cycles continuously ~ - 8 -upward at the center and downward near the perimeter, eventually flowing 245 out (by gravity) ~hrough conduit 10 into aeration vessel #2.
As receiving unit for sewage influent, the first stage aerator (vessel #l) sustains the highest oxygen demand. After being partially satiated in the first stage, the oxygen demand of the mixed 1iq~or tapers off sharply in the second stage unit (vessel #2). In accordance 2~0 therewith~ we have provided an adjustable throttle valve 11 on air supply line 34 to air diffuser head 12 in vessel #2. Whereas full air flow to diffuser head 7 creates a vigorous boil in vessel #l; the throttled air supply to diffuser head 12 produces only a gentle rolling action that enhances flocculation yet is sufficient to satiate 255 oxygen demand. When the sludge floc finally leaves vessel #2, it is strong and dense, settles easily, and has virtually assimilated all the organic waste in the wastewater.
The level of mixed liquor in vessels #1 and #2 is controlled by the overflow/transfer box 13 (located in vessel #2) from whence the fully 260 aerated mixed liquor enters conduit 14 and flows into the cyclone separator compartment 15 of vessel #3. The dif~erential head between liquid levels in vessels #2 and #3 imparts a velocity head to the flow in cyclone separator compartment 15. The mixed liquor spins in a descending spiral along the wall of the bottom cone. The floc (being 265 heavier than water) is spun to the outside and the centrate (consisting of water and pin floc) is displaced to the center (thé vortex of the cyclone). The heavy sludge floc descends to the bottom of the cone where it is continuously drawn off into suction line 16 of the sludge return pump 26.
270 Centrate f-~", the v.ortex flows up through opening 18 at the bottom of the upper cone 20 and flows into the settling compartment 19 of vessel ~3. In the settling compartment 19, the pin floc deposits out along the sides of the upper cone 20 and slides downward through the opening 18 into the lower chamber and is withdrawn with the return 275 sludge 16. The effluent spills over V-notch weirs into four radial draw-off troughs 21. Thence into a collec~or pocket 22, to a discharge pipe 23, past valve 24 which is regulated by a conventional liquid level controller 25 and discharge.
Return sludge 16 from vessel #3 is drawn into a conventional 280 volute pump 26 and pumped through check valve 28, into conduit 6, thence back into aeration vessel #1. Pump 26 is designed for a 300% volume of return sludge (300% of treatment flow capacity~. In the specific example shown on the drawing, the design capacity of the return sludge pump is (12,000 gpd) X (300/100) = 36,000 gpd which is 25 gpm (gallons per 285 minute). The static head against which it pumps is relatively constant,namely the elevation difference between the crest of weir 13 in vessel #2 and the crest of effluent weir 21 in vessel #3, plus a small dynamic head loss in pipe 6.
Supply air for the aeration bubbler heads 7 and 12 and air dome's 9 is 290 provided by a rotary compressor 31 capable of achieving pressures of up to 35 psi. In addition to a low volume of fresh supply air from compressor 31, there is a high volume of recycle air from air manifold 35 to diffuser heads 7 and 12 via the feed lines 34. Because blower 32 draws previously pressurized air from manifold 35, it need only 295 develop enough pressure to overcome the differential liquid head in vessels #l and #3, about 4 psi, thus providing high volume air movement at a minimum expenditure of energy. The higher pressure rotary com-pressor (35 psi) accordingly need supply only enough volume of fresh air to satisfy oxygen up-take plus a small allowance For wa~tage.
300 Pressure manifold 35 prsvides equalization of air pressure betweenall three pressure vessels #1, #2, #3, thereby creating a comlnon atmosphere within the process system in which the liquid can move by gravity flow without necessitating complex valve controls. Spent air in the system is exhausted through pressure relief valve 36 which 305 also serves to regulate air pre~sure in the system.
Approximate MLSS determinations are obtained by taking readings from the modified tubular viscometer 27 and extrapolating from a chart.
The viscometer consists of only two components: a 1~2 inch diameter by 30 foot long tube, and a 1~2 inch magnetic flow meter connected near 310 the mid-point of the tube. The 1~2 inch tube is about the minimum practical diameter that can handle sludge without plugging-up. The length of tube selected provides maximum sensi~ivity to change in MLSS (for the given diameter of pipe, differential head, and working range of MLSS).
315 As shown in the drawing, one end of the tube is connected to the discharge pipe 6 of sludge return pump 26 and the other end is connected to the suction line 16 of the return pump 26. The differential head between the two connection points is determined by the differential in liquid levels between vessels #2 and #3 plus the head losses in 320 pipes 6, lO, and 16. For reasons previously stated, the differential head across pump 26 is relatively constant, therefore all variations in flo~ rate through the meter 27 are due to changes in flow resistance of the return sludge, which result from changes in MLSS. By taking four or more samples of different return sludge concentrations, 325 recording their meter readings and obtaining a lab analysis of the suspended solids concentration, a graph is produced by plotting the meter readings (ordinate) as a function of suspended solids (abscissa).
The plot points will be interconnected with a curved line that can be used to extrapolate suspended solids from future mete~ readings.
330 The meter measures only the return sludge suspended solids, not the mixed liquor suspended solids MLSS. However, there being a continuous fixed rate of return sludge (300% of influent design capacity), the MLSS itself will merely be 3/4's of the return sludge SS. This calculation is slightly in error when the system is 335 operating at less than design capacity, but will be adequate for control purposes.
Sludge wasting is accomplished by cracking open valve 30 when magnetic flow meter 27 reaches its mirlimum allowable reading (indicating maximum allowable concentration of MLSS!. Wasting is continued until 340 the meter reading rises to the allowable maximum (indicating minimum allowable concentration of MLSS)~ whereupon waste valve 30 is either throttled or closed completelyO The waste system can be either.operated manually by -the trea~ment operator, or au~omatically with a conventional micro-processo~f~ ~rogranlmed ~o respor,d to limit signals ~rom the 345 magnetic flow meter~
The curved junction of pipe 6 with waste line 29 provides a means of selectively extracting grit and other heavy particles from the sludge recirculation system. Due to the curve in the junction, the heavy particles continue tangentially into the waste line draw-off stub 29 350 displacing any sluGge floc that become trapped thereinO Whenever valve 30 is opened, the captured grit flows out with the waste sludge.
-lla-
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. The method of treating organic waste water with activated sludge comprising the steps of:
establishing an enclosed continuous flow way for the organic waste water and the activated sludge in a mixed liquor form including several aeration chambers, and a separator chamber that are air pressurized to a predetermined pressure, that contain organic waste water and activated sludge, and that are consecutively connected in a continuous flow circuit through said aeration chambers, said separator chamber, and return flow to said one aeration chamber, mixing activated sludge and fresh organic waste water in said return flow, passing the return flow into said one aeration chamber adjacent the lower end thereof, dosing the body of the liquor of said one aeration chamber with air in diffused bubble form for flocculating and air saturation of the sludge, passing continuously from said liquor body a flow of the liquor to a subsequent of said aeration chambers having a second liquor body while diffusing air into said second body from the lower end of same for providing a liquor flow in which the flocculated sludge has assimilated the organic waste in the liquor flow, continuously passing in a gravity flow to said separator chamber the organic waste assimilated liquor flow, and establishing and maintaining in said separator chamber and in said organic waste assimilated liquor flow a cyclone separating action effecting centrifugal force and gravity induced settling out of the sludge flow thereof to provide said return flow, and a rising effluent centrate flow, continuously clarifying and discharging the centrate flow as tertiary quality effluent, and continuously pumping said return flow to effect said mixing and said first mentioned passing steps.
establishing an enclosed continuous flow way for the organic waste water and the activated sludge in a mixed liquor form including several aeration chambers, and a separator chamber that are air pressurized to a predetermined pressure, that contain organic waste water and activated sludge, and that are consecutively connected in a continuous flow circuit through said aeration chambers, said separator chamber, and return flow to said one aeration chamber, mixing activated sludge and fresh organic waste water in said return flow, passing the return flow into said one aeration chamber adjacent the lower end thereof, dosing the body of the liquor of said one aeration chamber with air in diffused bubble form for flocculating and air saturation of the sludge, passing continuously from said liquor body a flow of the liquor to a subsequent of said aeration chambers having a second liquor body while diffusing air into said second body from the lower end of same for providing a liquor flow in which the flocculated sludge has assimilated the organic waste in the liquor flow, continuously passing in a gravity flow to said separator chamber the organic waste assimilated liquor flow, and establishing and maintaining in said separator chamber and in said organic waste assimilated liquor flow a cyclone separating action effecting centrifugal force and gravity induced settling out of the sludge flow thereof to provide said return flow, and a rising effluent centrate flow, continuously clarifying and discharging the centrate flow as tertiary quality effluent, and continuously pumping said return flow to effect said mixing and said first mentioned passing steps.
2. The method set forth in claim 1 wherein:
said flow way is pressurized to have a uniform pressure of up to about 35 psig.
said flow way is pressurized to have a uniform pressure of up to about 35 psig.
3. The method set forth in claim 2 wherein:
said return flow is at a rate of approximately three hundred percent of said effluent centrate flow.
said return flow is at a rate of approximately three hundred percent of said effluent centrate flow.
4. The method set forth in claim 2 wherein:
the concentration of the liquor approximates 10,000 mg/1 of mixed liquor suspended solids.
the concentration of the liquor approximates 10,000 mg/1 of mixed liquor suspended solids.
5. The method set forth in claim 4 wherein:
said pumping step is effected across a relatively constant differential head.
said pumping step is effected across a relatively constant differential head.
6. The method set forth in claim 5 wherein:
the concentration of suspended sludge solids of said return flow at the site of said pumping step is monitored, and the return flow is sludge wasted to approximately maintain said liquor concentration.
the concentration of suspended sludge solids of said return flow at the site of said pumping step is monitored, and the return flow is sludge wasted to approximately maintain said liquor concentration.
7. The method set forth in claim 2 wherein:
the flow of the liquor in said aeration chambers and in said cyclone separating action is quiescent.
the flow of the liquor in said aeration chambers and in said cyclone separating action is quiescent.
8. Apparatus for continuously treating organic waste water with activated sludge as a mixed liquor, said apparatus comprising:
first and second vessels disposed at sub-stantially the same horizontal level respectively defining first and second aeration chambers, a third vessel disposed substantially at said horizontal level and defining a separator chamber, said first and second vessels containing the liquor up to a predetermined horizontal level, therein in each, with said first vessel being in liquid flow communication with said second vessel below said pre-determined level, said second vessel being connected to said third vessel chamber for gravity induced liquid flow of the liquor thereinto from said second vessel by conduit means extending from about said predetermined level of said second vessel to a lower level in said third vessel for imparting a velocity head to the liquor flow in said separator, said third vessel defining at its lower end a funnelling liquid flow discharge outlet and defining an internally centered frusto-conical divider baffle that depends in circumambient relation about said third chamber from above to below said lower level thereof and defines at its lower end a liquid upflow port, said third vessel above said baffle having means for effluent draw off therefrom, return conduit means connected between said third vessel outlet and the lower end of said first vessel for returning sludge from said separator chamber to said first chamber including pump means, inlet conduit means connected to said return conduit means adjacent said first chamber for supplying organic waste water thereto, said chambers being manifold connected at their upper ends and being commonly pressurized at a level in range of up to about 35 psig, first means for diffusing air into the liquor of said first chamber at the lower end of said first chamber, and second means for diffusing air into the liquor of said second chamber at the lower end of said second chamber, said liquor concentration in said first and second chambers being about 10,000 mg/1 MLSS, said pump means and said return conduit means effecting the return of the sludge therethrough at a rate approximating three hundred percent of the effluent draw off flow.
first and second vessels disposed at sub-stantially the same horizontal level respectively defining first and second aeration chambers, a third vessel disposed substantially at said horizontal level and defining a separator chamber, said first and second vessels containing the liquor up to a predetermined horizontal level, therein in each, with said first vessel being in liquid flow communication with said second vessel below said pre-determined level, said second vessel being connected to said third vessel chamber for gravity induced liquid flow of the liquor thereinto from said second vessel by conduit means extending from about said predetermined level of said second vessel to a lower level in said third vessel for imparting a velocity head to the liquor flow in said separator, said third vessel defining at its lower end a funnelling liquid flow discharge outlet and defining an internally centered frusto-conical divider baffle that depends in circumambient relation about said third chamber from above to below said lower level thereof and defines at its lower end a liquid upflow port, said third vessel above said baffle having means for effluent draw off therefrom, return conduit means connected between said third vessel outlet and the lower end of said first vessel for returning sludge from said separator chamber to said first chamber including pump means, inlet conduit means connected to said return conduit means adjacent said first chamber for supplying organic waste water thereto, said chambers being manifold connected at their upper ends and being commonly pressurized at a level in range of up to about 35 psig, first means for diffusing air into the liquor of said first chamber at the lower end of said first chamber, and second means for diffusing air into the liquor of said second chamber at the lower end of said second chamber, said liquor concentration in said first and second chambers being about 10,000 mg/1 MLSS, said pump means and said return conduit means effecting the return of the sludge therethrough at a rate approximating three hundred percent of the effluent draw off flow.
9. The apparatus set forth in claim 8 including means shunted across said pump means for monitoring the mixed liquor suspended solids factor of the return sludge from the rheological properties thereof, and means for wasting sludge from said return sludge for controlling the concentration therein of the such mixed liquor suspended solids.
10. The apparatus set forth in claim 8 wherein: said first and second air diffusing means are air supplied from the air pressurizing said chambers.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000432733A CA1194623A (en) | 1983-07-19 | 1983-07-19 | Method and apparatus for treating organic wastewater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000432733A CA1194623A (en) | 1983-07-19 | 1983-07-19 | Method and apparatus for treating organic wastewater |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194623A true CA1194623A (en) | 1985-10-01 |
Family
ID=4125701
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000432733A Expired CA1194623A (en) | 1983-07-19 | 1983-07-19 | Method and apparatus for treating organic wastewater |
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| Country | Link |
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| CA (1) | CA1194623A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN120463332A (en) * | 2025-05-26 | 2025-08-12 | 华能东莞燃机热电有限责任公司 | A sewage treatment device with integrated biological aeration filter for circulating cooling water in a power plant |
-
1983
- 1983-07-19 CA CA000432733A patent/CA1194623A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN120463332A (en) * | 2025-05-26 | 2025-08-12 | 华能东莞燃机热电有限责任公司 | A sewage treatment device with integrated biological aeration filter for circulating cooling water in a power plant |
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