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APPARATUS AND METHOD FOR TREATING SEWAGE AND WASTEWATER BIOLOGICALLY
BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an apparatus and method for treating sewage and wastewater biologically, and more particularly relates to the apparatus and method for sewage and wastewater treatment which, by means of microorganisms, each of an oxidization reaction of organic matter, a removal of nitrogen and phosphorous under an anoxic and anaerobic condition, and a precipitation of the microorganisms can be performed in a single reactor having multi-tube structure.
2. Description of the Related Art
Generally, In biological treatment of sewage and wastewater, an apparatus comprises an aeration tank for oxidizing organic matter contained in sewage and wastewater, and a sedimentation tank for precipitating microorganisms grown up in the aeration tank during an oxidization reaction and removing the sediment precipitated in the form of sludge. In order to remove nitrogen and phosphorous as well as organic matter from sewage and wastewater, the treatment apparatus may further comprise an denitrification
tank and an anaerobic tank, each arranged nearby the aeration tank in a transverse stream configuration.
However, in the conventional plant employed in the treatment process of wastewater, there exists several problems and disadvantages as follows: This conventional biological treatment plant requires a large installation area because each tank thereof must be arranged in a transverse stream configuraction to one another, and high construction costs because each tank structure is executed with concrete.
Further, an air-diffuser tube in the conventional aeration tank, which has a ceramic, cloth and resin-combined porous plate or tube, is arranged at the bottom portion of the aeration tank to generate and provide with relative large air-bubbles, thereby transferring oxygen to microorganisms in the aeration tank. However, since oxygen-consumed rate of microorganisms is higher than a air-supplied rate when the density of microorganisms is kept at a high level in the treatment tank, this method can't supply sufficient oxygen for the oxidization reaction in the treatment tank, thus causing a dissolved oxygen deficiency. Therefore, the density of microorganisms can't be kept at above 4,000 mg// in the treatment tank, due to the limitation of oxygen transfer rate, in case that it is required to treat a high concentration of organic wastewater.
Further more, since the secondary sedimentation tank of the
conventional treatment plant is independently installed, with separated from the aeration tank, there must be installed a pump for returning sedimentary sludge to the aeration tank.and a scrapper for preventing sedimentary sludge from stopping up a returning pipe of the plant. In this case, a much complex and high-priced mechanical and electronic apparatuses, related to these scrapper and returning pump, must be required additionally.
On the other hand, in order to remove organic matter from wastewater, in the conventional activated sludge process, there is arranged only aeration tank as a reaction bath for an oxidization treatment of
n
organic matter. However, in A /O process (having anaerobic-anoxic-aerobic conditions) and Bardenpho process (having anaerobic-anoxic-aerobic-anoxic-aerobic conditions) for discharging phosphorous and removing nitrogen from wastewater in an anaerobic condition, there are installed an anaerobic tank and a denitrification tank in addition to the aeration tank. In this case, in order to remove nitrate-nitrogen generated in the aeration tank, an inner circulation pump for returning sludge-suspended liquid from the aeration tank to the denitrification tank must be installed in the denitrification tank, which may has a flow rate of 2~6 times as much as the amount of influent wastewater. Further, several agitators may be also required in each
reaction tank such as the anaerobic tank, the electrification tank. Therefore, in case that the removal processes of nitrogen and phosphorous in addition to that of organic matter are performed, the processing steps and the mechanic construction thereof become much more complex as compared to the- conventional activated sludge process.
As stated above, since the conventional biological treatment plant has its reaction tanks installed in a same plane site, that is, each of reaction tank, such as the denitrification tank for removing nitrogen under the anoxic condition, the anaerobic tank for discharging phosphorous, the sedimentation tank for precipitating sludge therein and the like, is arranged with separated from one another respectively, the treatment plant occupies a larger installation area. In addition, since the agitator, the returning pump, the scrapper and the like should be installed in each reaction tank and the movement of sludge to each reaction should be performed by the pump, the mechanical structure of the plant becomes further complex, thus requiring high-installation expenses.
Further, in treatment process of the high-densifled organic matter, the air-supplying method in the conventional treatment plant has a limitation of oxygen transfer rate between air and microorganism when the oxygen-consumed rate of microorganisms is higher than air-supplied rate in the aeration tank. Therefore, in the conventional treatment plant, it is
difficult to keep the concentration of the microorganism at high level in the aeration tank.
SUMMARY OF THE INVENTION
Accordingly, the present invention is proposed to solve the above described problems, and it is the primary object of the invention to provide an apparatus and method for treating sewage and wastewater by biological reaction comprising reaction bath which volume thereof can be further reduced than that of the prior art and the density of microorganisms can be kept at 10,000 mg/i or more in the reaction bath by improving a oxygen transfer rate to the microorganisms, that is accomplished by generating extremely fine bubble of air or soluble oxygen, employing a Membrane such as a microfiltration (formed with its pores having 0.1-100 µm in diameter) and ultrafiltration (formed with its pores having 1.5-10 µm in diameter), this increasing a contact efficiency between air-bubbles and the microorganism in the reaction tank.
Further, it is another object of the invention to provide an apparatus and method for treating sewage and wastewater which can provide the optimum environments for removing organic matter, nitrogen and phosphorous from wastewater effectively in a minimum flow-distance of wastewater to be treated. Minimum flow distance is
tank, and then oxidizing and removing organic matter, nitrogen and absorbing phosphorous by microorganisms, which have not been treated completely through said steps and still remained within returned sludge; mixing sludge formed in aeration tank after performing the returning step with influent wastewater flown into the aeration tank from the open, and then circulating sludge-suspended wastewater through said steps again; and separating microorganisms of sludge-suspended wastewater, which are received in the sedimentation tank after performing the mixing step, into solid and liquid state, and then precipitating sludge and discharging treated water to the open through the overflow weir.
In the present invention there is disclosed an apparatus for treating sewage and wastewater biologically, comprising:
an aeration tank for receiving influent wastewater and activated sludge therein and oxidizing organic matter contained in influent wastewater; an air-bubble generating means such as herein described, which is positioned at the bottom of the aeration tank, for providing influent wastewater and sludge received in the aeration tank with air and/or oxygen for an oxidization reaction in air-bubbles form, said air-bubbles gushing out of the air-bubble generating means such as herein described and having a propelling force enough to raise upward and circulate sludge-suspended liquid in the aeration tank;
an anoxic and anaerobic tank, which is arranged outside the aeration tank, for receiving sludge-suspended liquid overflowing the aeration tank in a space defined between the aeration tank and the anoxic and anaerobic tank, and then performing removal of nitrogen and discharge of phosphorus from sludge-suspended liquid; and
a sedimentation tank, which is arranged outside the anoxic and anaerobic tank, for receiving sludge-suspended liquid flown into the sedimentation tank after circulating through the aeration tank and the anoxic and anaerobic tank.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which: Fig. 1 is a schematic view showing the construct of the present invention.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENT
Hereinafter, an embodiment of the invention will be described referring to Fig. 1.
According to the invention, an apparatus for biological sewage and wastewater treatment, as shown in Fig. 1, has an aeration tank 2, an anoxic and aerobic tank 3, and a sedimentation tank 4.
The aeration tank 2 have a inner space receiving activated sludge and influent wastewater which relative large suspended solid and foreign matter were removed therefrom and then permitting influent wastewater to contact with air-bubbles provided through an air-diffusing tube 5. Here, the air-diffusing tube 5 is arranged at the bottom portion of the aeration tank 2, for generating fine air-bubbles by gushing out open air provided by a blower (will be described later) into the inner space of the tank 2. And an blower or compressor 11 is connected to an end of the air-diffuser 5 for providing with open air. At this time, the air-bubbles gushed out through the air-diffusing tube 5 provides sludge-suspended liquid (or the mixed liquid of sludge and influent wastewater) with its rising force, thus permitting sludge-suspended liquid to overflow the aeration tank 2.
In the desirable embodiment of the present invention, there is a need that the density of microorganisms must be kept at high level when wastewater or excrementitious matter, as an example, occurred from the stockbreeding site, comes into the aeration tank 2. In this case, a Membrane such as a microfiltration, ultrafiltration may be employed instead of the air-diffuser 5. Also a pump 8 for agitating sludge-suspended
liquid on the water may be arranged at upper side of the aeration tank 2, for providing sludge suspended liquid with an additional circulation force in case that air-bubbles gushing out through Membrane can't induce sufficient propelling force enough to permit sludge-suspended liquid to rise upward and overflow the tank 2.
The aeration tank 2 is arranged inside the anoxic and anaerobic tank 3 having larger its diameter than that of the aeration tank 2. In a space defined between the aeration tank 2 and the anoxic and anaerobic tank 3. influent wastewater and sludge with a high concentration of nitrate-nitrogen, which overflow the aeration tank 2 and come into the space by the propelling force of air-bubbles gushing out of the air-diffuser 5, are received and treated therein, that is, in the space, a removal of nitrogen and a discharging of phosphorous by biological reaction is performed. On the inner wall of the anoxic and anaerobic tank 3, there are mounted a plurality of plate members 7 in a zigzag arrangement so that influent wastewater and sludge which overflow the aeration tank 2 and come into the anoxic and anaerobic tank 3 can collide against the plate members 7, thus mixed completely and uniformly .
As stated above, the aeration tank 2 and the anoxic and anaerobic tank 3 consist of two cylindrical body which have their the upper and the lower end portion opened, the one arranged inside the other in co-axial
relation and then supported and spaced out a predetermined distance apart from the other by a plurality of first supporting members 9. In above description, it has been described that the tanks 2 and 3 have constructed with cylindrical body having circular-section, but not limited to the above statement, the two tanks 2 and 3 may be constructed by employing the box-body having a polygonal or an oval cross section.
The two tanks 2 and 3 are also supported inside the sedimentation tank 4, as a cylindrical tube-shaped body having its lower end portion closed and its upper end portion opened, by a plurality of second supporting members 14 in the same way as the arrangement of the two tanks 2 and 3. In the space defined between the sedimentation tank 4 and the anoxic and anaerobic tank 3, sludge-suspended liquid which circulated through the aeration tank 2 and the anoxic and anaerobic tank 3 is received. Then sludge of sludge-suspended liquid is precipitated in the sedimentation tank 4.
In the present embodiment, the lower portion of each tank is formed with its wall become narrow inward with 1/10 — 1/20 of a slope. Therefore, since the lower wall body of the aeration tank 2 takes the form of a flow path expended upward, outflow sludge through the opening of the bottom portion of the anoxic and anaerobic tank 3 and sludge at the bottom of the sedimentation tank 4 can obtain their rising force from the inertia force
of air-bubbles gushing out of the air-diffuser 5, thus being propelled upward and flowing into the aeration tank 2 effectively.
Since sludge in the sedimentation tank 4 absorbs nitrogen gas or air-bubbles and increases its surface-area ratio, thus rising upward in the sedimentation tank undesirably, in the middle portion of inner space between the anoxic and anaerobic tank 3 and the sedimentation tank 4, as shown Fig. 1, there is mounted a net 13 for preventing sludge with its surface-area ratio increased from rising upward in the sedimentation tank 4. On the periphery of the upper portion of the sedimentation tank 4, there is arranged a overflow weir 6 for releasing treated water to the outside of the apparatus after temporarily receiving treated water which overflowed the sedimentation tank 4. The upper end portion of the sedimentation tank 4 is covered with an lid 15 for preventing rainwater, foreign matters and the like from coining into the tanks.
Hereinafter, the operation of the present invention having the above stated construct will be described, with reference to Fig. 1.
If influent wastewater 1, which relative large suspended solids and foreign matter were removed therefrom by the screen(not shown), flows into the aeration tank 2, influent wastewater(or inflow water) 1 is mixed with sludge raised upward by the propelling force of air-bubbles gushing out of the air-diffusing tube 5 in the aeration tank 2 and becomes into
sludge-suspended liquid. Then sludge-suspended liquid overflows the aeration thank 2 and flows into the anoxic and anaerobic tank 3 uniformly before organic matter of influent wastewater is oxidized in an aerobic condition of the aeration tank 2. As a result, organic matter contained in influent wastewater can be used as a source of Carbon for a removal reaction of nitrogen and a discharging reaction of phosphorous in the anoxic and anaerobic tank 3.
Sludge-suspended liquid, which overflows the aeration tank 2 and flows into the anoxic and anaerobic tank 3, comes to strike against the plate members 7 mounted on the inner wall of the anoxic and anaerobic tank 3, thus is mixed further completely and uniformly. In a space between the upper and middle portion of the anoxic and anaerobic tank 3, an anoxic condition which oxygen has been exhausted out by microorganisms is formed, and then there is performed a nitrogen removal reaction which deoxidizes nitrate-nitrogen contained in mixed liquid into nitrogen gas by using organic matter of influent wastewater as a source of Carbon. And in a space between the middle and lower portion of the anoxic and anaerobic tank 3, an anaerobic condition due to the exhaustion of dissolved oxygen and nitrate-nitrogen is formed, and then there is performed a reaction for discharging phosphorous from the cell of microorganisms by using organic matter of mixed liquid as a carbon source, which remained still after used
in the removal reaction of nitrogen. At this time, a detention time in the anoxic and anaerobic tank 3 is set within about 1 hour in response to the flow rate of influent wastewater.
Outflow sludge through the opening formed at the bottom of the tank 2 and sedimentary sludge in the sedimentation tank 4 flow upward and return into the aeration tank 2 by the propelling force of air-bubbles gushing out of air-diffusing tube 5. At this time, since the lower wall of each tank is slanted inward at 1/10 — 1/20 of a slope and the lower wall of the aeration tank 2 forms the flow path expended upward, outflow sludge from the anoxic and anaerobic tank 3 and sedimentary sludge of the sedimentation tank 4 can flow up to the aeration tank 2 effectively, by obtaining the rising force from the propelling force of air-bubbles gushing out of the air-diffuser 5.
After the above process is completed, in the aeration tank 2, there is performed the reaction for additionally oxidizing organic matter which has not been removed yet in the anoxic and anaerobic tank 3 and the nitrogen contained in influent wastewater, and there is also performed the absorption reaction of phosphorous by microorganisms, which are discharged in the anoxic and anaerobic tank 2 and contained in influent wastewater. Sludge of the aeration tank 2 is mixed with influent wastewater, and then mixed liquid of sludge and influent wastewater(or, sludge-suspended liquid; overflows the tank 2 and flows into the anoxic and anaerobic tank 3 again
by the propelling force of the air-bubble gushing out of air-diffuser 5. This circulation is continuously repeated, and sedimentary sludge of the sedimentation tank 4 is intermittently removed by microorganisms grown up after taking up organic matter.
'Here, in the aeration tank 2, the hydraulic retention time (HRT) is kept for 4~8 hours and also F/M (Food/Microorganism) ratio is kept at about 0.1 kgBOD/kgMLSS • d.
Further, in the treatment of wastewater having a high concentration of organic matter, such as wastewater or excrementitious matter from the stockbreeding site, the aeration tank 2 must be kept to have the density of microorganisms at a high level. This can be accomplished by employing Membrane and providing with sufficient dissolved oxygen. However, if sludge of the tanks 3 and 4 doesn't obtain sufficient force enough to move upward into the aeration tank 2 by air-bubbles gushing out through the Membrane, There is employed the agitator 8 for promoting to mix sludge of the aeration tank 2 with influent wastewater, thereby providing sludge-suspended liquid with additional propelled force required to its upward-flow. While, if the density of microorganism in the aeration tank 2 is at 4,OOOmg/ł or less, there may be employed the conventional air-diffuser 5, thus providing with oxygen for oxidization of organic matter and a propelled force of sludge'-subpenaed liquid.Sludge suopenaed liquid, which flowed into the sedimentation tank 4 after circulating through the aeration tank 2 and the anoxic and anaerobic tank 3, is retained for 2~3 hours of the detention time in the sedimentation tank 4, thus the microorganisms passed through the aeration tank 2 and the anoxic and anaerobic tank 3 are separated into the solid body of sludge and the treated water, and then sludge is precipitated in the sedimentation tank 4 and the treated water 12 overflows the upper of the tank 4 and releases outside through the overflow weir 9.
Hereinafter, the comparable experiments of the present invention to the conventional apparatus are will be described.
(Comparable Experiment 1)
The present experiment have compared the concentration values of dissolved oxygen according to the density of the microorganism when a general air-diffusing apparatus (having a air-diffusing tube with a ceramic disk) has employed, to those when a Hollow Fiber Membrane air-diffusing apparatus (with polysulphone fabrics having 0.2 /M of pore size) has employed. At this time, each apparatus had a 30 m£/min of air-flow rate. The resultant of experiment will be shown in Table 1.
As shown in Table 1, in case that the experiment was performed with the general air-diffusing apparatus employed, the proper concentration of
dissolved oxygen in the aeration tank 2 was decreased below 2.5 mg/ £ when the density of the microorganism (MLSS) was above 6,OOOmg/e While, in case that the experiment was performed with a Membrane air-diffusing apparatus employed (such as a microfiltration or an ultrafiltration), the proper1 concentration of dissolved oxygen in the tank 2 was kept at above 2.5 mg/ e in range of above 6, OOOmg/ e of the MLSS density.
Therefore, it shows that the Membrane air-diffusing apparatus can increase the oxygen transfer rate further higher than the general air-diffusing apparatus, thus permitting the density of microorganisms to be kept at a high level in the aeration tank 2.
[Table 1]
Dissolved Oxygen Density according to Density of Microorganism
(Table Removed)(Comparable Experiment 2)
In the present experiment, a standard activated sludge process and
M
an A /O process (comprising anaerobic, anoxic and aerobic condition) have been operated along with the present invention in order to compare the removal efficiency of organic matter, nitrogen and phosphorous in the present invention to those in the conventional processes.
•Further, in the present experiment, wastewater and excrementitious matter from the stockbreeding site, which having a high concentration of organic matter, nitrogen and phosphorous, was used as influent wastewater to be treated in each process, the treatment flow rate in each process was 500 e/d, and each process was operated in a row.
Table 2 shows operation conditions applied to each process in the present experiment.
[Table 2] Operation ondition
O Standard Activated Sludge Process
- F/M ratio in Aeration tank: 0.1 kg BOD/kg MLSS • d
- Detention Time in Aeration tank: 6 hours
- Density of MLSS: 4,000 mg/ e
0 A2/0 Process
- Detention Time in Anaerobic tank: l hours
- Detention Time in Anoxic tank: 2 hours
- F/M ratio in Aeration tank: 0.1 kg BOD/kg MLSS • d
- Detention Time in Aeration tank: 6 hours
- Density of MLSS: 4,000 mg/ I
O Present Invention
- Detention Time in Anoxic and Anaerobic tank: 30 minutes
- F/M ratio in Aeration tank: 0.1 kg BOD/kg MLSS • d
- Detention Time in Aeration tank: 6 hours
- Density of MLSS: 8,000-10,000 mg/ e
As shown in Table 2, in the standard activated sludge process and
n
A/O process, the density of microorganism was set at about 4,000 mg/ I , and in the process of the present invention, a Hollow Fiber Membrane, with polysulphone fabrics having 0.2 im of pore size, was employed in the air-diffusing apparatus and the density of microorganism was kept at 8,00 0-10,000 mg/ i, .
Table 3 shows the change values of the constituent of treated water
2
after respectively performed by the standard activated sludge process, A /O process and the process of the present invention, which averaged resultants of operation in each process for about 6 months.
[Table 3]
Comparison of Removal Efficiency in each process
(Table Removed
(Table Removed
(Table Removed Wherein, COD, TKN, N03-N, T-P and T-N- respectively indicate Chemical Oxygen Demand, Total Kjeldahl Nitrogen, Nitrite-Nitrogen, Total-Phosphorus, Total-Nitrogen
As shown in Table 3, the removal rates of organic matter, nitrogen and phosphorous in the A2/0 process, . having the anaerobic and denitrification processes in addition to the aeration process, were superior to those of the standard activated sludge process. And the removal
ates of organic matter, nitrogen and phosphorous in the process according to the present invention, which can keep the high density of microorganism at high level, were further superior to those of said two processes.
Table 4 shows a sludge volume Index (SVI:
Sf-
-) and
a phosphorous content of sludge of the aeration tank in each process, the
n
standard activated sludge process, the A /O process and the process of the
present invention.
[Table 4]
SVI and Phosphorous Contents of Sludge in Aeration tank
(Table Removed As shown in Table 4, Sludge of the aeration tank in the present invention has the highest phosphorous content, and SVI in the present invention is also better than those in other processes.
According to the present invention having the construction as described above, various advantages and effects can be obtained as follows:
Since phosphorous content of sludge in the present invention, which anaerobic and aerobic conditions are repeated, is in range of 6~8%, while
that of the conventional process, which has only aerobic condition, is below 2%, therefore, the mineral content of sludge in the present invention is high than that in the conventional process, a sedimentary property of sludge in the present invention is better than that of the conventional process.
In the present invention, since the space except for biological reaction tank is separated from air-supply, thus preventing a vortex flow from occurring in the space, said space can be used as a sedimentation basin.
Further, since the present invention employes Membrane such as microfiltration and ultrafiltration, which can generate fine air-bubbles, instead of the conventional air-diffusing apparatus which forming relative large air-bubbles, oxygen transfer rate in the present invention can be increased much more than that of the prior art, therefore the present invention can have the density of microorganism kept at a high level in the biological reaction tank, the present invention can effectively treat not only the domestic swage and wastewater but also the excrementitious matter and wastewater from the stockbreeding site, which have the higher concentration of organic matter, nitrogen and phosphorous than that of the conventional process. Also this treatment can be performed in a single biological reaction place.
In the present invention, since sludge-suspended liquid moves between the tanks by obtaining its propelled force from air-bubbles gushing out of the Membrane, there are no needs that the pump for moving sludge between the tanks and the facilities related to the pump should be installed additionally.
Therefore, it should be understood that the present invention is not limited to the particular embodiment disclosed herein as the best mode contemplated for carrying out the present invention, but rather than the present invention is not limited to the specific embodiments described in this specification except as defined in the appended claims.
we claim;
1. An apparatus for treating sewage and wastewater
biologically, comprising:
an aeration tank for receiving influent wastewater and activated sludge therein and oxidizing organic matter contained in influent wastewater;
an air-bubble generating means such as herein described, which is positioned at the bottom of the aeration tank, for providing influent wastewater and sludge received in the aeration tank with air and/or oxygen for an oxidization reaction in air-bubbles form, said air-bubbles gushing out of the air-bubble generating means such as herein described and having a propelling force enough to raise upward and circulate sludge-suspended liquid in the aeration tank;
an anoxic and anaerobic tank, which is arranged outside the aeration tank, for receiving sludge-suspended liquid overflowing the aeration tank in a space defined between the aeration tank and the anoxic and anaerobic tank, and then performing removal of nitrogen and discharge of phosphorus from sludge-suspended liquid; and
a sedimentation tank, which is arranged outside the anoxic and anaerobic tank, for receiving sludge-suspended liquid flown into the sedimentation tank after circulating through the aeration tank and the anoxic and anaerobic tank.
2. An apparatus as claimed in claim 1, comprising a plurality of plate members(9), which are mounted on the inner wall of the anoxic and anaerobic tank.
3. An apparatus as claimed in claim 1, wherein each of said
aeration tank, said anoxic and aerobic tank, and said
sedimentation tank has its lower shape become narrow inward
with 1/10~1/20 of slant.
4. An apparatus as claimed in claim 1, comprising an
agitation means, which is installed at the upper side of the
.aeration tank.
5. An apparatus as claimed in any one of claims 1 to 4,
wherein said air-bubble generating means is constructed with
Membrane having a plurality of minute pores with
microfiltration and ultrafiltration.
6. An apparatus as claimed in any one of claims 1 to 4,
wherein said air-bubble generating means is constructed with
an air-diffusing tube.
7. An apparatus as claimed in claim 1, wherein said
aeration tank and said anoxic and anaerobic tank take the
form of a single body, which consists of coaxial multi-tube
in one inside the other relation, each tube having its upper
and bottom portions opened with a circle or a polygonal
cross section.
8. An apparatus as claimed in claim 1, comprising a
plurality of first support members (14) for locating the
aeration tank in place inside the anoxic and anaerobic tank
so that a predetermined space can be formed between the
aeration and the anoxic and anaerobic tank.
9. An apparatus as claimed in claim 1, comprising a
plurality of second support members (14) for locating the
anoxic and anaerobic tank in place inside the sedimentation
tank so that a predetermined space can be formed between the
anoxic and anaerobic tank and the sedimentation tank.
10. An apparatus as claimed in any one of claims 1 to 4,
-comprising means (13) for preventing sludge of the
sedimentation tank from rising up therein when treated water is released out, which is mounted at predetermined position in a space between the sedimentation tank and the anoxic and anaerobic tank.
11. An apparatus as claimed in any one of claims 1 to 4,
comprising a overflow weir (6), which is mounted on the
upper periphery wall of the sedimentation tank, for
releasing out treated water after receiving it temporally.
12. An apparatus as claimed in claim 1, comprising a lid
for preventing inflow of rain water or foreign matter,
which is installed on the upper end of the sedimentation
tank.
13. A method for treating, sewage and wastewater
biologically comprising the steps of:
receiving influent wastewater which relatively large suspended solid and foreign matters are removed therefrom by a screen;
forming minute air-bubbles through the air-bubbles generating means in the aeration tank and providing influent wastewater and sludge in the aeration tank with air and/or oxygen.
overflowing influent water and sludge of the aeration tank and sending them to the anoxic and aerobic tank;
discharging phosphorous and removing nitrogen from sludge-suspended wastewater received in the anoxic and aerobic tank;
returning sludge from the sedimentation tank and the anoxic and aerobic tank to the aeration tank, and then oxidizing and removing organic matter, nitrogen and absorbing phosphorous by conventional microorganisms , which have not treated completely through said steps and still remained within returned sludge;
mixing sludge formed in aeration tank after performing the returning step with influent wastewater flown into the aeration tank from the open, and then circulating sludge-suspended wastewater through said steps again; and
separating microorganisms of sludge-suspended wastewater, which are received in the sedimentation tank after performing the mixing step, into solid and liquid state, and then precipitating sludge and discharging treated water to the open through the overflow weir (6).
14. A method as claimed in claim 13, wherein said foaming
step is performed by employing the air-diffusing tube in
case that the density of microorganism is 4,000mg/j or
less in the reaction tanks, while by employing the
Membrane having minute pores, such as a microfiltration or
a ultrafiltration, in case density of microorganism is
4,000 mg/l or more.
15. A method as claimed in claim 13 or 14, wherein said
overflowing step is performed by circulating sludge-
suspended liquid of the aeration tank upward and permitting
it to overflow the aeration tank, using a propelling force of air-bubbles gushing out of the air-diffusing tube or by means of agitation means.
16. A method as claimed in claim 13 or 14, wherein said
discharging step is performed by reducing nitrate-nitrogen
of sludge-suspended liquid into nitrogen-gas in the upper
portion of the anoxic and anaerobic tank and degasing the
nitrogen-gas therefrom, and by discharging phosphorous
from the cell of microorganisms under the anaerobic
condition of the lower portion of the anoxic and anaerobic
tank, using organic matter of influent wastewater as a
carbon source, which remained after removal reaction of
nitrogen.
17. A method as claimed in claim 13 or 14, wherein said
discharging step includes a process mixing sludge-suspended
liquid flowing into the anoxic and anaerobic tank further
completely by permitting influent liquid to collide against
the plate members mounted on the inner wall of the anoxic
and anaerobic tank.
18. A method as claimed in claim 13 or 14, wherein detention
time in the anoxic and anaerobic tank is upto one hour.
19. A method as claimed in claim 13 or 14, wherein returning
of sludge from the sedimentation tank is performed by using
the propelling force of air-bubbles gushing out of the air-
generating means.
20. A method as claimed in claim 13 or 14, wherein hydraulic
detention time in sedimentation tank is in the range of 4~8
hours and Food/Micro organism ratio is 0.1 kgBOD/kgMLSS.d (Mixed Liquor Suspended Solid) in the aeration tank.
21. An apparatus for treating sewage and wastewater
biologically, substantially as herein described with
reference to the foregoing description and the accompanying
drawing.
22. A method for treating sewage and wastewater
biologically, substantially as herein described with
reference to the foregoing description and the accompanying
drawing.
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