CA1063263A - Continuous introduction of oxygen-containing gases into effluent containing activated sludge - Google Patents
Continuous introduction of oxygen-containing gases into effluent containing activated sludgeInfo
- Publication number
- CA1063263A CA1063263A CA 248281 CA248281A CA1063263A CA 1063263 A CA1063263 A CA 1063263A CA 248281 CA248281 CA 248281 CA 248281 A CA248281 A CA 248281A CA 1063263 A CA1063263 A CA 1063263A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- oxygen
- activated sludge
- effluent
- inlets
- 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
- 239000007789 gas Substances 0.000 title claims abstract description 87
- 239000001301 oxygen Substances 0.000 title claims abstract description 45
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 45
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 239000010802 sludge Substances 0.000 title abstract description 37
- 239000007788 liquid Substances 0.000 claims abstract description 26
- 230000001174 ascending effect Effects 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 238000000855 fermentation Methods 0.000 claims description 3
- 230000004151 fermentation Effects 0.000 claims description 3
- 230000002706 hydrostatic effect Effects 0.000 abstract description 10
- 238000000034 method Methods 0.000 abstract description 9
- 238000010521 absorption reaction Methods 0.000 abstract description 4
- 208000036366 Sensation of pressure Diseases 0.000 abstract 1
- 239000002912 waste gas Substances 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- 238000005276 aerator Methods 0.000 description 1
- 230000001580 bacterial effect Effects 0.000 description 1
- 230000031018 biological processes and functions Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000004332 deodorization Methods 0.000 description 1
- 230000001877 deodorizing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 101150115538 nero gene Proteins 0.000 description 1
- 238000010943 off-gassing Methods 0.000 description 1
- -1 oxygen per se Chemical compound 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 238000009931 pascalization Methods 0.000 description 1
- 230000005501 phase interface Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- C02F3/26—Activated sludge processes using pure oxygen or oxygen-rich gas
-
- 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
- B01F23/40—Mixing liquids with liquids; Emulsifying
- B01F23/45—Mixing liquids with liquids; Emulsifying using flow mixing
- B01F23/454—Mixing liquids with liquids; Emulsifying using flow mixing by injecting a mixture of liquid and gas
-
- 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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Biodiversity & Conservation Biology (AREA)
- Microbiology (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Activated Sludge Processes (AREA)
- Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)
Abstract
A SINGLE-STAGE PROCESS AND APPARATUS FOR CONTINUOUS INTRODUC-TION OF OXYGEN-CONTAINING GASES INTO EFFLUENT
CONTAINING ACTIVATED SLUDGE
Abstract of the Disclosure A process and apparatus for the continuous introduc-tion of air or oxygen-containing gases into an effluent contain-ing activated sludge, the oxygen-containing gas largely being consumed by the effluent containing activated sludge in a single absorption stage, comprising introducing through a plurality of gas inlets an oxygen-containing gas into an effluent containing activated sludge which is in a basin under its own hydrostatic pressure of at least about 0.9 bar, the gas pressure of the gas introduced being about 0.01 to 0.5 bar above the hydrostatic pres-sure prevailing at the gas inlet, each gas inlet having a gas-swept cross-sectional area of at least about 0.01 m2 which is loaded by at least about 100 effective cubic meters of gas per square meter of cross-sectional area per hour, and the individ-ual gas inlets being separated by a distance of at least about 0.5 meter, as measured from the middle point of a gas inlet.
The gas inlets may be nozzles, ejectors or apertured plates preferably spaced equidistantly from one another and each may be supplied with propulsion liquid comprising effluent containing activated sludge. Preferred ranges from the various parameters depend upon whether the gas introduced contains more or less than 50 % by volume of oxygen.
CONTAINING ACTIVATED SLUDGE
Abstract of the Disclosure A process and apparatus for the continuous introduc-tion of air or oxygen-containing gases into an effluent contain-ing activated sludge, the oxygen-containing gas largely being consumed by the effluent containing activated sludge in a single absorption stage, comprising introducing through a plurality of gas inlets an oxygen-containing gas into an effluent containing activated sludge which is in a basin under its own hydrostatic pressure of at least about 0.9 bar, the gas pressure of the gas introduced being about 0.01 to 0.5 bar above the hydrostatic pres-sure prevailing at the gas inlet, each gas inlet having a gas-swept cross-sectional area of at least about 0.01 m2 which is loaded by at least about 100 effective cubic meters of gas per square meter of cross-sectional area per hour, and the individ-ual gas inlets being separated by a distance of at least about 0.5 meter, as measured from the middle point of a gas inlet.
The gas inlets may be nozzles, ejectors or apertured plates preferably spaced equidistantly from one another and each may be supplied with propulsion liquid comprising effluent containing activated sludge. Preferred ranges from the various parameters depend upon whether the gas introduced contains more or less than 50 % by volume of oxygen.
Description
In the operation of a biological effluent treatment plant, the ~lctivated-~ludge bnsin has to be ~upplied with the quantlty of oxygen required for the metabolism of the mlcroorganisms and a certain concentration o~` oxygen mu~t be ~aintalned to permlt nero~ic bacterial culture. The oxygen requir~d for this purpose is delivered to the litluid from the gas phase. The rate at which o~ygen is supplied to the liquid from the ga8 i8 ~ on the one h~nd, g~overned by the size of the interface between the gaR and liquid phase and by the turbulence prevailing there, while on the other hand it i~ directly proportional to the concentration difference ~ c between the oxygen saturation concentration and the concentration of 2 dissolved in the liquid.
The phase interface is increased inter alia by using sur-face aerators or by introducing a gas, generally air, into the liquid and dispersing it in the liquid, optionally by means of stirrers or liquid ~ets (ejectors; different kind of nozzles). In the first case, the pressure in the gas-treatment zone is normal, while in the second case basins from 3 to 7 meters deep are generally used, so that a slight hydrostatic 2C pressure prevails in the gas dispersion zone.
In general, the described method of gas treatment is carried out in open basins, with the result that the waste air escaping contains, in some cases in conslderable quantities, readily volatile foul-smelling constituents which pollute the surroundings. Since atmospheric oxygen is only very incompletely utilized in the described aeration processes, the quantity of air required to satisfy the oxygen demand and, hence, the quantity of waQte air as well i8 very considerable so that deodorization by heat treatment is very expensive.
The supply of oxygen to the liquid can be considerably accelerated by increasing the concentration difference ~ c .
Le A 16 290 - 1 -In practice, this increase in the concentration difference ~ c can only be obtained by increasing the 02-partial pre~sure in the gas. This can be done either by raising the system pressure or by changing from air to oxygen or an oxygen-enriched gas.
However, the use of pure oxygen or of an oxygen-enriched gas requires, ~or economic reasons, that the gas stream be largely deprived of oxygen as it passes through the installation. When working under normal pressure, this re~ult may be obtained by repeatedly introducing the gas stream into the li~uid and/or by passing the gas through successive absorption stages (a so-called "multistage activated-sludge basin"). The production of a narrow residence-time distribution of the gas throughput by cascading the treatment zones is the sub~ect of the process according to German Auslegeschrift No. 2,032,535.
The system pressure may be raised to increase the concen-tration difference ~ c by designing the activated sludge stage in the form of a shaft. However, this requires intensive circulation of the liquid in order to ensure that, on the one hand, the low-oxygen layers enter the intensive oxygen transport zone and, on the other hand, that the liquid is never saturated with oxygen in that zone in order to prevent outgassing and, hence, flotation of the activated sludge in areas where a lower hydrostatic pressure prevails. Circulation of the liquid may be obtained by dividing the shaft with partitions into an ascending path and a descending path (German Offenlegungsschrift No.
The phase interface is increased inter alia by using sur-face aerators or by introducing a gas, generally air, into the liquid and dispersing it in the liquid, optionally by means of stirrers or liquid ~ets (ejectors; different kind of nozzles). In the first case, the pressure in the gas-treatment zone is normal, while in the second case basins from 3 to 7 meters deep are generally used, so that a slight hydrostatic 2C pressure prevails in the gas dispersion zone.
In general, the described method of gas treatment is carried out in open basins, with the result that the waste air escaping contains, in some cases in conslderable quantities, readily volatile foul-smelling constituents which pollute the surroundings. Since atmospheric oxygen is only very incompletely utilized in the described aeration processes, the quantity of air required to satisfy the oxygen demand and, hence, the quantity of waQte air as well i8 very considerable so that deodorization by heat treatment is very expensive.
The supply of oxygen to the liquid can be considerably accelerated by increasing the concentration difference ~ c .
Le A 16 290 - 1 -In practice, this increase in the concentration difference ~ c can only be obtained by increasing the 02-partial pre~sure in the gas. This can be done either by raising the system pressure or by changing from air to oxygen or an oxygen-enriched gas.
However, the use of pure oxygen or of an oxygen-enriched gas requires, ~or economic reasons, that the gas stream be largely deprived of oxygen as it passes through the installation. When working under normal pressure, this re~ult may be obtained by repeatedly introducing the gas stream into the li~uid and/or by passing the gas through successive absorption stages (a so-called "multistage activated-sludge basin"). The production of a narrow residence-time distribution of the gas throughput by cascading the treatment zones is the sub~ect of the process according to German Auslegeschrift No. 2,032,535.
The system pressure may be raised to increase the concen-tration difference ~ c by designing the activated sludge stage in the form of a shaft. However, this requires intensive circulation of the liquid in order to ensure that, on the one hand, the low-oxygen layers enter the intensive oxygen transport zone and, on the other hand, that the liquid is never saturated with oxygen in that zone in order to prevent outgassing and, hence, flotation of the activated sludge in areas where a lower hydrostatic pressure prevails. Circulation of the liquid may be obtained by dividing the shaft with partitions into an ascending path and a descending path (German Offenlegungsschrift No.
2,423,085).
The ob~ect of the present invention is to develop a single-stage process for the treatment of effluent in activated-sludge basins, in which the advantage of a high hydrostatic pressure is combined with the advantage of the absence of backmixing Le A 16 290 - 2 -in regard to the gas phase so that the oxygen present in the gas is utilized to a high degree during only a single passage through the effluent containing activated sludge. In the single-stage activated-sludge basin, the oxygen-containing gas is passed into only a single absorption stage where it is largely deprived of oxygen. It has been found that, in the case of large treatment plants, it is not economical to carry out gas treatment outside the activated sludge basins, for example in a deep ~haft, because in that case the supply of dissolved oxygen requires a liquid circuit that is almost imposæible to establish. Thus, the input of oxygen must of necessity take place within the activated sludge stage. However, cost factors preclude designing the entire activated sludge stage in the form of a deep shaft.
Accordingly, the present invention rel ates to an apparatus for the biological treatment of effluent or for fermentation processes in a basin having a height of about 10 to 40 m, a height to diameter ratio between about 5:1 and 0.5:1, comprising a plurality of gas-inlets with an individual cross-sectional areas of from about 0.1 to 0.5 m2 arranged substantially equidis-tantly from another at a height up to about 1 m above the base of the basin and separated from one another by a distance of about 2 to 10 m, as measured from the middle point of each gas-inlet, wherein each gas-inlet is loaded with 100 to 300 effective m3 of gas/m2 of cross-sectional area per hour of gas, containing at least 50% by volume of oxygen, thereby obtaining the formation of chimneys with intensive ascending and descending circulation of liquid.
The apparatus of the invention is useful in a process for the continuous introduction of air or oxygen-containing gases into an effluent containing activated sludge, the oxygen-containing gas largely being consumed by the effluent containing activated sludge in a single absorption stage, distinguished by the fact that the oxygen-containing gas is introduced into the effluent containing activated sludge, which is under its own hydrostatic 3Q presaure, in zones where a hydrostatic pressure of at least about 0.9 bar prevails, the gas pressure of the gas introduced being about 0.01 to 0.5 bar above the hydrostatic pressure prevailing at the gas inlet, each gas inlet having a gas-swept cross-sectional area of at least about 0.01 m2 which is loaded by at least about 100 effective cubic meters of gas per square meter of cross-sectional area per hour.
The gas inlets are conveniently arranged substantially equidistantly from one another in the base or just above the base, preferably up to about 0.5 to l meter above the base.
It has been found that, to absorb oæygen to a high degree (80 to 90 %) in a single stage, it is essential to ensure, through intenslve circulation of the liquid and through rapid ascent of the swarm of gas bubbles, that no appreciable oxygen concentration gradients occur in the activated-sludge basin, and that the liquid entrained by the swarm of gas bubbles on the air-lift pump principle is not saturated with oxygen to such an eætent that degassing can occur in zones where a relatively low hydro-static pressure prevails. The measures taken in accordance with the invention provide for the treatment of effluent containing activated sludge in a single stage during which the oxygen is consumed.
It has surprisingly been found that, in cases where air is used, a waste gas containing about 8 % by volume of oxygen can be obtained. By virtue of the effective utilization of oxygen in the activated sludge basin, the input of air and, hence, the quantity of waste gas as well can be reduced to one half to one third of the level normally encountered in conventional processes using air. This factor also enables the fuel demand (for example fuel oil) required for thermally deodorizing the waste air at around 1000C
to be reduced to between one half and one third of the quantity which would normally be necessary for combustion.
In accordance with one embodiment of the invention, oxygen-contain-ing gases containing more than S0 % by volume of oxygen, including oxygen per se, are only introduced through a certain number of gas inlets, preferably through more than about 5 gas inlets. These gas inlets may be arranged eith~r in the bottom of the activated sludge basin or just above it, prefer-ably up to about 1 meter above the bottom of the activated-sludge basin. The gas enters the effluent containing activated sludge through these gas inlets, 1~63Z63 preferably vertically upwards, in the form of a swarm of gas bubbles. This results in the formation of "chimneys" with intensive ascending and descend-ing circulation of liquid, the effect of which does not ha ve to be supported by any fittings.
sased on the cross-sectional area of the activated sludge basin, one gas inlet is provided for every 0.2 to 15 m2 of cross-sectional area.
These gas inlets for the oxygen-containing gas are preferably circular or annular in shape. However, they may also assume other forms, for example a quadratic or equilateral triangular form. The oxygen-containing gas is introduced through these gas inlets into the activated sludge basin in throughputs of about 100 to 300 effective cubic meters per unit area (m2) and per unit of time (hours) (cross-sectional load of a gas inlet).
The gas inlets may be designed in known manner in the form of nozzles, ejectors, perforated plates, etc., which enable the oxygen-contain-ing gas introduced to be effectively dispersed into fine gas bubbles.
Eiectors are preferred. All the gas inlets are preferably situated in zo~es of equal hydrostatic pressure and are spaced at a distance of about 2 to 10 meters (as measured from the middle point of a gas inlet). In addition, the gas inlets should be arranged as uniformly as possible over the entire cross-sectional area of the activated sludge basin.
In accordance with ~ertain preferred combination of conditions, in `~ one set of conditions of which~Rxample ~ hereinbelow is illustrative, each gas inlet has a gas-swept cross-sectional area of about 0.1 to 0.5 m2, pre-ferably about 0.1 to 0.3 m , which is loaded by about 100 to 300, preferably about 150 to 250, effective cubic meters of gas per square meter of cross-sectional area per hour, the gas inlets being spaced from one another by about 2 to 10 meters, preferably about 3 to 6 meters. One gas inlet is provided for about every 8 to 12 m2 of cross-sectional area. The gas introduced con-tains more than 50 % by volume of oxygen.
The finene~s of the gas bubbles initially produced in the gas-treatment zone is governed by the energy applied for dispersing the gas throughput into gas bubbles. In the case of eiectors and single-orifice plates (Chemie-Ingenieur-Technik) 43 (1971) 6, 329-335), this energy is generally applied by a certain liquid througllput through the gas dispersion unit. In one special embodiment, therefore, a liquid acting as propulsion liquid is introduced through the gas inlet together with the oxygen-contain-ing gas. This liquid throughput amounts to between about 10 and 30 % by volume of the gas throughput under normal conditions. It is particularly advantageous to use the effluent containing activated sludge as the propelling li~uid.
While the present invention will be set forth with special regard to biological treatment of effluent it easily can be performed similarly in other biological processes, where oxygen supply is necessary, e.g. fermentation processes.
The invention is further described in the accompanying schematic drawing of an apparatus for carrying out the treatment of effluent.
In the drawing, 10 is a cylindrical activated sludge basin provided with numerous gas e~ectors 12 to which oxygen containing gas is supplied via 14. Waste gas escapes at 16, passing to a burner (not shown). Effluent overflows at 18 and through a pump 20 part of this effluent is delivered to the ejectors 12 as the propulsion liquid.
The invention is further described in the following illustrative example relating to a process carried out with an apparatus as described.
Example 1 (using technical pure 2 as aerating gas):
An activated sludge basin with a liquid volume of 6200 m3 is charged with 800 m3/h of effluent. me oxygen demand of this installation amounts to 45,6 tons/day. The oxygen concentration of the liquid amou~ts to 6 mg/l and the water temperature to 30C. The liquid level in the activated sludge basin amounts to 20 meters, the cylindrical ac~ivated sludge basin having a diameter of also 20 meters (cross-sectional area of the activ-ated sludge basin 314 m2). According to the invention, oxygen is introduced into the liquid containing activated sludge at only 30 inlets (one inlet to about every 10 m2), these gas in-lets being arranged equidistantly (imagined as being at the corners of equilateral triangles). Ejectors (cross-sectional area: 0.1 m2) arranged about 0.5 meter above the bottom of the basin are used as the gas inlets. The throughput per ejector amounts to 19.4 effective cubic meters /h of gas and 6 m3/h of effluent containing activated sludge. This effluent containing activated sludge is taken from the activated sludge basin and delivered to the e~ectors as the propulsion liquid through delivery pump(s). The excess pressure of the gas introduced at the gas inlet amounts to about 0.01 bar above the hydrostatic pressureO The degree of utilization amounts to 80 % of the quan-tity of oxygen introduced.
It will be appreciated that the instant specification andexamples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.
Le A 16 290
The ob~ect of the present invention is to develop a single-stage process for the treatment of effluent in activated-sludge basins, in which the advantage of a high hydrostatic pressure is combined with the advantage of the absence of backmixing Le A 16 290 - 2 -in regard to the gas phase so that the oxygen present in the gas is utilized to a high degree during only a single passage through the effluent containing activated sludge. In the single-stage activated-sludge basin, the oxygen-containing gas is passed into only a single absorption stage where it is largely deprived of oxygen. It has been found that, in the case of large treatment plants, it is not economical to carry out gas treatment outside the activated sludge basins, for example in a deep ~haft, because in that case the supply of dissolved oxygen requires a liquid circuit that is almost imposæible to establish. Thus, the input of oxygen must of necessity take place within the activated sludge stage. However, cost factors preclude designing the entire activated sludge stage in the form of a deep shaft.
Accordingly, the present invention rel ates to an apparatus for the biological treatment of effluent or for fermentation processes in a basin having a height of about 10 to 40 m, a height to diameter ratio between about 5:1 and 0.5:1, comprising a plurality of gas-inlets with an individual cross-sectional areas of from about 0.1 to 0.5 m2 arranged substantially equidis-tantly from another at a height up to about 1 m above the base of the basin and separated from one another by a distance of about 2 to 10 m, as measured from the middle point of each gas-inlet, wherein each gas-inlet is loaded with 100 to 300 effective m3 of gas/m2 of cross-sectional area per hour of gas, containing at least 50% by volume of oxygen, thereby obtaining the formation of chimneys with intensive ascending and descending circulation of liquid.
The apparatus of the invention is useful in a process for the continuous introduction of air or oxygen-containing gases into an effluent containing activated sludge, the oxygen-containing gas largely being consumed by the effluent containing activated sludge in a single absorption stage, distinguished by the fact that the oxygen-containing gas is introduced into the effluent containing activated sludge, which is under its own hydrostatic 3Q presaure, in zones where a hydrostatic pressure of at least about 0.9 bar prevails, the gas pressure of the gas introduced being about 0.01 to 0.5 bar above the hydrostatic pressure prevailing at the gas inlet, each gas inlet having a gas-swept cross-sectional area of at least about 0.01 m2 which is loaded by at least about 100 effective cubic meters of gas per square meter of cross-sectional area per hour.
The gas inlets are conveniently arranged substantially equidistantly from one another in the base or just above the base, preferably up to about 0.5 to l meter above the base.
It has been found that, to absorb oæygen to a high degree (80 to 90 %) in a single stage, it is essential to ensure, through intenslve circulation of the liquid and through rapid ascent of the swarm of gas bubbles, that no appreciable oxygen concentration gradients occur in the activated-sludge basin, and that the liquid entrained by the swarm of gas bubbles on the air-lift pump principle is not saturated with oxygen to such an eætent that degassing can occur in zones where a relatively low hydro-static pressure prevails. The measures taken in accordance with the invention provide for the treatment of effluent containing activated sludge in a single stage during which the oxygen is consumed.
It has surprisingly been found that, in cases where air is used, a waste gas containing about 8 % by volume of oxygen can be obtained. By virtue of the effective utilization of oxygen in the activated sludge basin, the input of air and, hence, the quantity of waste gas as well can be reduced to one half to one third of the level normally encountered in conventional processes using air. This factor also enables the fuel demand (for example fuel oil) required for thermally deodorizing the waste air at around 1000C
to be reduced to between one half and one third of the quantity which would normally be necessary for combustion.
In accordance with one embodiment of the invention, oxygen-contain-ing gases containing more than S0 % by volume of oxygen, including oxygen per se, are only introduced through a certain number of gas inlets, preferably through more than about 5 gas inlets. These gas inlets may be arranged eith~r in the bottom of the activated sludge basin or just above it, prefer-ably up to about 1 meter above the bottom of the activated-sludge basin. The gas enters the effluent containing activated sludge through these gas inlets, 1~63Z63 preferably vertically upwards, in the form of a swarm of gas bubbles. This results in the formation of "chimneys" with intensive ascending and descend-ing circulation of liquid, the effect of which does not ha ve to be supported by any fittings.
sased on the cross-sectional area of the activated sludge basin, one gas inlet is provided for every 0.2 to 15 m2 of cross-sectional area.
These gas inlets for the oxygen-containing gas are preferably circular or annular in shape. However, they may also assume other forms, for example a quadratic or equilateral triangular form. The oxygen-containing gas is introduced through these gas inlets into the activated sludge basin in throughputs of about 100 to 300 effective cubic meters per unit area (m2) and per unit of time (hours) (cross-sectional load of a gas inlet).
The gas inlets may be designed in known manner in the form of nozzles, ejectors, perforated plates, etc., which enable the oxygen-contain-ing gas introduced to be effectively dispersed into fine gas bubbles.
Eiectors are preferred. All the gas inlets are preferably situated in zo~es of equal hydrostatic pressure and are spaced at a distance of about 2 to 10 meters (as measured from the middle point of a gas inlet). In addition, the gas inlets should be arranged as uniformly as possible over the entire cross-sectional area of the activated sludge basin.
In accordance with ~ertain preferred combination of conditions, in `~ one set of conditions of which~Rxample ~ hereinbelow is illustrative, each gas inlet has a gas-swept cross-sectional area of about 0.1 to 0.5 m2, pre-ferably about 0.1 to 0.3 m , which is loaded by about 100 to 300, preferably about 150 to 250, effective cubic meters of gas per square meter of cross-sectional area per hour, the gas inlets being spaced from one another by about 2 to 10 meters, preferably about 3 to 6 meters. One gas inlet is provided for about every 8 to 12 m2 of cross-sectional area. The gas introduced con-tains more than 50 % by volume of oxygen.
The finene~s of the gas bubbles initially produced in the gas-treatment zone is governed by the energy applied for dispersing the gas throughput into gas bubbles. In the case of eiectors and single-orifice plates (Chemie-Ingenieur-Technik) 43 (1971) 6, 329-335), this energy is generally applied by a certain liquid througllput through the gas dispersion unit. In one special embodiment, therefore, a liquid acting as propulsion liquid is introduced through the gas inlet together with the oxygen-contain-ing gas. This liquid throughput amounts to between about 10 and 30 % by volume of the gas throughput under normal conditions. It is particularly advantageous to use the effluent containing activated sludge as the propelling li~uid.
While the present invention will be set forth with special regard to biological treatment of effluent it easily can be performed similarly in other biological processes, where oxygen supply is necessary, e.g. fermentation processes.
The invention is further described in the accompanying schematic drawing of an apparatus for carrying out the treatment of effluent.
In the drawing, 10 is a cylindrical activated sludge basin provided with numerous gas e~ectors 12 to which oxygen containing gas is supplied via 14. Waste gas escapes at 16, passing to a burner (not shown). Effluent overflows at 18 and through a pump 20 part of this effluent is delivered to the ejectors 12 as the propulsion liquid.
The invention is further described in the following illustrative example relating to a process carried out with an apparatus as described.
Example 1 (using technical pure 2 as aerating gas):
An activated sludge basin with a liquid volume of 6200 m3 is charged with 800 m3/h of effluent. me oxygen demand of this installation amounts to 45,6 tons/day. The oxygen concentration of the liquid amou~ts to 6 mg/l and the water temperature to 30C. The liquid level in the activated sludge basin amounts to 20 meters, the cylindrical ac~ivated sludge basin having a diameter of also 20 meters (cross-sectional area of the activ-ated sludge basin 314 m2). According to the invention, oxygen is introduced into the liquid containing activated sludge at only 30 inlets (one inlet to about every 10 m2), these gas in-lets being arranged equidistantly (imagined as being at the corners of equilateral triangles). Ejectors (cross-sectional area: 0.1 m2) arranged about 0.5 meter above the bottom of the basin are used as the gas inlets. The throughput per ejector amounts to 19.4 effective cubic meters /h of gas and 6 m3/h of effluent containing activated sludge. This effluent containing activated sludge is taken from the activated sludge basin and delivered to the e~ectors as the propulsion liquid through delivery pump(s). The excess pressure of the gas introduced at the gas inlet amounts to about 0.01 bar above the hydrostatic pressureO The degree of utilization amounts to 80 % of the quan-tity of oxygen introduced.
It will be appreciated that the instant specification andexamples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention.
Le A 16 290
Claims (2)
PROPERTY OR PRIVILEDGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for the biological treatment of effluent or for fermentation processes in a basin having a height of about 10 to 40 m, a height to diameter ratio between about 5:1 and 0.5:1, comprising a plurality of gas-inlets with an individual cross-sectional areas of from about 0.1 to 0.5 m2 arranged substantially equidistantly from another at a height up to about 1 m above the base of the basin and separated from one another by a distance of about 2 to 10 m, as measured from the middle point of each gas-inlet, wherein each gas-inlet is loaded with 100 to 300 effective m3 of gas/
m2 of cross-sectional area per hour of gas, containing at least 50% by volume of oxygen, thereby obtaining the formation of chimneys with intensive ascend-ing and descending circulation of liquid.
m2 of cross-sectional area per hour of gas, containing at least 50% by volume of oxygen, thereby obtaining the formation of chimneys with intensive ascend-ing and descending circulation of liquid.
2. An apparatus as claimed in claim 1, and including gas introduction nozzles, ejectors or single-aperture plates spaced equidistantly from one another.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2512815A DE2512815C2 (en) | 1975-03-22 | 1975-03-22 | Device for biological waste water treatment |
| DE19752516914 DE2516914A1 (en) | 1975-04-17 | 1975-04-17 | Biological treatment of effluent contg. activated sludge - involves continuously introducing oxygen (contg. gas) and feeding the outlet gas to a burner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1063263A true CA1063263A (en) | 1979-09-25 |
Family
ID=25768677
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 248281 Expired CA1063263A (en) | 1975-03-22 | 1976-03-19 | Continuous introduction of oxygen-containing gases into effluent containing activated sludge |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS51117453A (en) |
| AU (1) | AU524259B2 (en) |
| CA (1) | CA1063263A (en) |
| CH (1) | CH614683A5 (en) |
| DK (1) | DK121176A (en) |
| FR (1) | FR2305400A1 (en) |
| GB (1) | GB1527424A (en) |
| NL (1) | NL7602978A (en) |
| SE (1) | SE7602245L (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2705243A1 (en) * | 1977-02-09 | 1978-08-17 | Bayer Ag | SINGLE-STAGE PROCESS FOR THE CONTINUOUS ENTRY OF OXYGEN-CONTAINING GASES INTO ANIMATED SLUDGE-CONTAINING WASTEWATER |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS49113463A (en) * | 1973-03-01 | 1974-10-29 |
-
1976
- 1976-02-24 SE SE7602245A patent/SE7602245L/en not_active Application Discontinuation
- 1976-03-17 AU AU12094/76A patent/AU524259B2/en not_active Expired
- 1976-03-18 CH CH343376A patent/CH614683A5/en not_active IP Right Cessation
- 1976-03-19 CA CA 248281 patent/CA1063263A/en not_active Expired
- 1976-03-19 GB GB1113076A patent/GB1527424A/en not_active Expired
- 1976-03-19 DK DK121176A patent/DK121176A/en unknown
- 1976-03-19 JP JP2935776A patent/JPS51117453A/en active Pending
- 1976-03-22 NL NL7602978A patent/NL7602978A/en not_active Application Discontinuation
- 1976-03-22 FR FR7608259A patent/FR2305400A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2305400B1 (en) | 1982-03-05 |
| CH614683A5 (en) | 1979-12-14 |
| JPS51117453A (en) | 1976-10-15 |
| NL7602978A (en) | 1976-09-24 |
| FR2305400A1 (en) | 1976-10-22 |
| AU524259B2 (en) | 1982-09-09 |
| AU1209476A (en) | 1977-09-22 |
| DK121176A (en) | 1976-09-23 |
| GB1527424A (en) | 1978-10-04 |
| SE7602245L (en) | 1976-09-23 |
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