JP3907867B2 - Wastewater treatment system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waste water treatment system for effective utilization of phosphorus resources collected simultaneously efficiently the removal of phosphorus in waste water sewage or the like.
[0002]
[Prior art]
Conventionally, treated water obtained by, for example, biologically treating wastewater such as sewage has been required not to contain nitrogen or phosphorus for the purpose of preventing eutrophication of the discharge destination. .
[0003]
When removing phosphorus from wastewater by a coagulation sedimentation method or the like, which is a method for removing phosphorus, the amount of water to be treated is large, and chemical costs such as a coagulant such as polyaluminum chloride are required, resulting in an increase in running cost. In addition, since a large amount of agglomerated sludge is generated, disposal is difficult and disposal costs increase.
[0004]
Therefore, in recent years, there are many biological nitrogen and phosphorus simultaneous removal methods (hereinafter referred to as A ₂ O methods) that remove nitrogen and phosphorus from wastewater using anaerobic tanks, anoxic tanks, and aerobic tanks, both domestically and internationally. It has been put into practical use. A ₂ O means Anaerobic Anoxic Oxic, that is, anaerobic, anoxic, and aerobic, and refers to biological water treatment using this process.
[0005]
FIG. 5 is a flow sheet showing the configuration of a conventional wastewater treatment apparatus using the A ₂ O method. In FIG. 5, 1 is a first settling basin for solid-liquid separation prior to the main treatment of the inflowing wastewater, and 2 is a separation liquid introduced from the first settling basin 1 and BOD in the separated liquid is used. This is a floating sludge type reaction tank for simultaneous denitrification and dephosphorization. The reaction tank 2 is divided into an anaerobic tank 3, an oxygen-free tank 4, and an aerobic tank 5. 6 is an agitator disposed in the anaerobic tank 3, 7 is an agitator disposed in the anaerobic tank 4, and 8 is an aeration device disposed in the aerobic tank 5 and having both an agitating function and an aeration function, Reference numeral 9 denotes a final sedimentation basin that receives effluent water from the aerobic tank 5 and separates it into solid and liquid.
[0006]
10 is a circulation means for circulating the mixed liquid in the aerobic tank 5 to the anoxic tank 4, and 11 is an initial settling sludge pipe for drawing the first settling sludge from the first settling tank 1 to the sludge treatment process. , 12a is a return sludge pipe for returning a part of the sludge solid-liquid separated in the final sedimentation basin 9 to the anaerobic tank 3, and 12b is a part of the sludge separated solid-liquid in the final sedimentation basin 9. It is a surplus sludge conduit for drawing out to the first sedimentation basin 1 as surplus sludge.
[0007]
Next, the operation will be described.
The inflow wastewater is first solid-liquid separated in the settling tank 1, and the separated liquid is introduced into the anaerobic tank 3. In the anaerobic tank 3, the separation liquid is brought into contact with the return sludge returned from the final sedimentation tank 9 via the return sludge conduit 12a. At that time, the phosphorus accumulating bacteria contained in the return sludge are discharged into the waste water. Incorporates soluble BOD (mainly volatile organic acids) inside, and simultaneously releases phosphorus in the cells. Outflow water from the anaerobic tank 3 is introduced into the anoxic tank 4. Here, the oxidized nitrogen returned from the aerobic tank 5 is reduced to nitrogen gas by the denitrifying bacteria and removed. The effluent from the anaerobic tank 4 is introduced into the aerobic tank 5, the BOD in the wastewater is oxidatively decomposed under aerobic conditions, and ammonia nitrogen and organic nitrogen are nitrified by nitrifying bacteria. Excessive reuptake by accumulated bacteria and removal from the liquid phase. The outflow water from the aerobic tank 5 is solid-liquid separated in the final sedimentation tank 9, the treated water is discharged after disinfection, and a part of the sludge is returned to the anaerobic tank 3. Moreover, a part of sludge is sent to a sludge treatment process via the excess sludge pipe line 12b as excess sludge, and is processed.
[0008]
[Problems to be solved by the invention]
By the way, according to the conventional A ₂ O method as described above, a large amount of phosphorus is taken up by phosphorus accumulating bacteria in the excess sludge (solid phase) generated by biological dephosphorization treatment. When stored under anaerobic conditions, phosphorus-accumulating bacteria release phosphorus and shift from sludge (solid phase) to separated water (liquid phase). Furthermore, if separation water containing a large amount of phosphorus is returned to the wastewater treatment facility as return water, phosphorus is not discharged out of the wastewater treatment facility, resulting in a decrease in phosphorus removal rate. .
[0009]
The present invention has been made to solve the above problems, reviewing the conventional A ₂ O method, BOD, nitrogen, among phosphorus, in particular phosphorus efficiently removed, the waste water that can be recovered An object is to provide a processing system .
[0010]
[Means for Solving the Problems]
Waste water treatment system engaged Ru to the present invention includes a bioreactor for performing biological processes by introducing the waste water, and solid-liquid separator for separating the organism reactor mixture in the treated water and the separated sludge, the stirring the whole amount of the separated sludge separated in the solid-liquid separation device in under anaerobic and anaerobic device for returning anaerobic sludge obtained in said biological reactor, a portion of the anaerobic sludge was stirred at該嫌degasifier concentrated features and sludge concentrator for separating the sludge and concentrate separated liquid, that introducing the concentrate separated liquid separated in the sludge concentration device, and a phosphorus removal device for removing phosphorus contained in the concentrate separated liquid It is what.
[0011]
Waste water treatment system engaged Ru to the present invention includes a primary sedimentation of the solid-liquid separating the waste water into the upper supernatant water and the settled sludge, the bioreactor to perform biological treatment by introducing the upper supernatant water, the organism reaction A solid-liquid separation device that separates the tank mixture into treated water and separated sludge, an acid fermentation device that introduces the precipitated sludge to perform acid fermentation, and the acid fermentation device that separates the separated sludge separated by the solid-liquid separation device anaerobic device for returning to the bioreactor was stirred under anaerobic under with discharge liquid discharged from the sludge concentrating device for separating a portion of the stirred anaerobic sludge該嫌degasifier to the concentrated sludge and the concentration and separation liquid And a phosphorus removing device for removing phosphorus contained in the concentrated separation liquid.
[0012]
Waste water treatment system engaged Ru to the present invention includes a anoxic tank to the bioreactor was equipped with a stirring means, and aerobic tank provided with aeration means, circulation means for circulating該好gas tank mixture to the anoxic tank It is characterized by the following.
[0013]
Waste water treatment system engaged Ru in the present invention is characterized in that the bioreactor is intermittent aeration tank provided with aeration means and mixing means.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below.
Embodiment 1 FIG.
Figure 1 is a flow sheet showing the waste water treatment system that by the first embodiment of the present invention. In FIG. 1, 21 is a biological reaction tank, 22 is a solid-liquid separator that performs a solid-liquid separation process , 23 is an anaerobic apparatus that performs an anaerobic process , 24 is a sludge concentration apparatus that performs a sludge concentration process, and 25 is a phosphorus removal process . It is a phosphorus removal device to be performed . The biological reaction tank 21 is supplied with anaerobic sludge (return sludge) from the anaerobic device 23 and performs biological treatment of waste water represented by normal activated sludge treatment. Further, it may be a combination of aerobic tanks or an intermittent aeration tank provided with aeration stirring means. The solid-liquid separation device 22 performs solid-liquid separation on the effluent (mixed solution) from the biological reaction tank 21, discharges treated water to the outside of the system, and returns the separated sludge to the anaerobic device 23. As solid-liquid separation in the solid-liquid separation device 22, a gravitational precipitation type final sedimentation basin is used, but a membrane separation device can be used if necessary. The anaerobic device 23 reduces oxidized nitrogen in the separated sludge separated by the solid-liquid separation device 22 under anaerobic conditions by denitrifying bacteria and at the same time releases a large amount of phosphorus by the phosphorus accumulating bacteria. The resulting anaerobic sludge, while being fed to the biological reactor 21, a portion of the anaerobic sludge (5-30%) is fed to the sludge concentrating apparatus 24. Sludge concentrating apparatus 24 is intended to concentrate the portion of the anaerobic sludge obtained by the anaerobic device 23, concentration method is specifically separated by mechanical concentrator or separator film such as a centrifugal concentrator or centrifuge filtration concentrator However, when the amount of anaerobic sludge is large, a gravity concentration method may be used. The concentrated separation liquid separated by the sludge concentrating device 24 contains a high concentration of phosphorus. The separation liquid phosphorus containing large amounts are then introduced to the phosphorus removal device 25. As the phosphorus removal device 25, it is desirable to use a crystallization dephosphorization device that removes phosphorus by precipitating a phosphorus compound such as magnesium ammonium phosphate (MAP) in the crystal nucleus. Further, a coagulation precipitation apparatus using a coagulant such as polyaluminum chloride (PAC) may be used as appropriate.
[0015]
In the first embodiment, since the high concentration phosphorus-containing separation liquid concentrated and separated by the sludge concentrating device 24 is introduced into the phosphorus removing device 25, phosphorus is reliably removed without returning to the wastewater treatment system. Can be recovered. Moreover, phosphorus removal can be stably and efficiently performed regardless of the inflow situation of the wastewater and the biological treatment situation. Moreover, since the processing amount in the phosphorus removal apparatus 25 is limited to a small amount of concentrated separation liquid, the apparatus can be made compact and the running cost required for the processing can be reduced.
[0016]
Further, in the first embodiment, since sludge is withdrawn from the sludge concentrating apparatus 24 as excess sludge is already concentrated sludge containing little phosphorus after releasing phosphorus, clogging of piping due to MAP scale in the sludge treatment facilities And device troubles can be avoided.
[0017]
Furthermore, in this Embodiment 1, when the MAP removal apparatus by crystallization reaction is used for the phosphorus removal apparatus 25, the MAP particle | grains enlarged and discharged | emitted can be collect | recovered and can be used effectively as a fertilizer. In addition, even when a coagulation sedimentation processing apparatus is used, the amount of concentrated separation liquid is small, so that the running cost can be reduced and the amount of coagulated sludge generated can be suppressed.
[0018]
Embodiment 2. FIG.
Figure 2 is a flow sheet showing the waste water treatment system that by the second embodiment of the present invention. Features of the second embodiment, the sludge anaerobic sludge phosphorus starvation obtained by the concentrator 24 is supplied to the bioreactor 21, phosphorus removal water bioreactor 21 obtained in phosphorus removal device 25 It is in the point to return to. The concentrated sludge obtained by the sludge concentrating device 24 contains a large amount of phosphorus-starved phosphorus-accumulating bacteria that have already released phosphorus by the anaerobic device 23, so that the phosphorus contained in the wastewater is returned to the biological reaction tank 21. Can be efficiently removed. Moreover, since suspended substances and dissolved organic substances remain in the phosphorus-removed water, it is desirable to return them to the biological reaction tank 21.
[0019]
Embodiment 3 FIG.
3 is a flow sheet showing the main part of the waste water treatment system that by the third embodiment of the present invention. The feature of this third embodiment is that in the previous first or second embodiment, the waste water before being introduced into the biological reaction tank 21 is first introduced into the settling basin 26 and the first settling effluent as the precipitation supernatant. Is introduced into the biological reaction tank 21, and the sedimented sludge (primary sedimented sludge) first separated in the sedimentation tank 26 is introduced into the acid fermentation apparatus 27, and the acid fermentation liquid is separated with the sludge separated from the solid-liquid separation apparatus 22. The point is that it is introduced into the anaerobic device 23.
[0020]
In the third embodiment, unlike the first or second embodiment, the supernatant water (primary sediment separation water) and the solid precipitate are not introduced directly into the biological reaction tank 21 but passed through the first sedimentation basin 26. Separated into things. The precipitated solid is then introduced into the acid fermentation apparatus 27 and subjected to acid fermentation to produce an easily decomposable organic acid. The acid fermentation broth containing a large amount of readily degradable organic acid is introduced into the anaerobic device 23, but when the phosphorus accumulating bacteria release phosphorus with the anaerobic device 23, the organic matter is ingested. Easily degradable low molecular organic acids are more effective than high molecular organic substances such as carbohydrates. Therefore, by providing the acid fermentation device 27, it becomes possible to efficiently release phosphorus in the anaerobic device 23. This is particularly effective when the load in the wastewater is large.
[0021]
Embodiment 4 FIG.
Figure 4 is a flow sheet showing the waste water treatment system that by the fourth embodiment of the present invention. The feature of this fourth embodiment is that, in the previous second embodiment, the biological reaction tank 21 is composed of an anaerobic tank 28 and an aerobic tank 29, and the effluent from the aerobic tank 29 is passed through the anoxic tank 28. In this point, a circulation means 30 for circulating and returning is provided. The circulation means 30 is mainly composed of a transfer device such as an air lift pump or a submersible pump and a transfer pipe line.
[0022]
In the fourth embodiment, the initial settling effluent flowing out from the first settling basin 26 is introduced into the anoxic tank 28 of the biological reaction tank 21, and the circulating liquid and anaerobic device 23 circulated from the aerobic tank 29 by the circulation means 30. is mixed anaerobic sludge supplied, and with thickened sludge returned from the sludge concentrator 24. Oxidized nitrogen contained in the circulating liquid is reduced by denitrifying bacteria in the sludge in the anoxic tank 28 and discharged out of the system as nitrogen gas. The mixed solution in the anaerobic tank 28 flows into the aerobic tank 29 and the organic matter is decomposed by a biological reaction, and phosphorus is excessively ingested by the phosphorus-accumulating bacteria in the phosphorus-starved state. Mixture aerobic tank 29 is introduced into solid-liquid separator 22, although the separation liquid is discharged after disinfection as treated water, separated sludge is returned to the anaerobic unit 23, acid fermentation from acid fermentation apparatus 27 Mixed with liquid in anaerobic condition. The anaerobic sludge obtained by the anaerobic device 23 is introduced into the anoxic tank 28, but a part of the anaerobic sludge is sent to the sludge concentrating device 24 and concentrated. The concentrated separation liquid containing phosphorus in a high concentration is sent to the phosphorus removal apparatus 25, and phosphorus is removed from the concentrated separation liquid using, for example, a MAP removal apparatus by crystallization reaction. In addition, the MAP particle | grains selected by the phosphorus removal by a MAP removal apparatus can be reused for an agricultural fertilizer or an industrial material. As described above, suspended substances and dissolved organic substances remain in the phosphorus-removed water from which phosphorus is removed and discharged. In this case, it is desirable that the phosphorus-removed water be returned to the aerobic tank 29.
[0023]
Here, in FIG. 4, the total amount of waste water and treated water and the total phosphorus concentration are shown for each process (each device) as material balance data regarding phosphorus. As shown in FIG. 4, the wastewater primary sedimentation 26 and be introduced at a flow rate of Qm ³ / day, when the total phosphorus concentration in the waste water with 3.0 mg / L, the treated water from the solid-liquid separator 22 Is discharged at a flow rate of 0.995 Qm ³ / day, the total phosphorus concentration at that time is 0.5 mg / L, and the phosphorus removal rate is about 83% or more. Incidentally, the separation sludge returned from the solid-liquid separator 22 to the anaerobic apparatus 23 is 20-50% of the inlet waste water quantities and transfer amount anaerobic sludge from an anaerobic apparatus 23 to the sludge concentrating apparatus 24 of the inflow amount of waste water A range of 5 to 20% is desirable. Anaerobic sludge the total amount, with it is not bad practical efficiency of concentrated sludge concentrating apparatus 24, it is possible to perform a sufficient phosphorus removal in an amount described above. In addition, the phosphorus concentration in the concentrated separation liquid introduced into the phosphorus removal device 25 is about 30 mg / L, which is approximately 10 times the phosphorus concentration in the inflow wastewater, and the phosphorus removal device 25 ensures phosphorus from the inflow wastewater. It can be seen that it can be efficiently removed and recovered.
[0024]
In the case of operation of the oxygen-free tank 28 in the fourth embodiment, an ORP sensor for measuring the oxidation-reduction potential ORP in the mixed solution is installed in the oxygen-free tank 28, and this value (the range of the ORP is approximately It is desirable to adjust the operation so that the oxygen-free state in the oxygen-free tank 28 can be suitably maintained using ± 0 to -300 mV) as an index. As a stirrer (not shown) in the oxygen-free tank 28, a mechanical stirrer mainly equipped with stirring blades is used, but any means can be used as long as it can suppress the oxygen supply and generate a water flow, and is not particularly limited.
[0025]
In addition, when the mixed solution flowing out from the anaerobic tank 28 is introduced into the aerobic tank 29, the mixed solution is transferred so that the mixed solution in the aerobic tank 29 does not flow back to the anaerobic tank 28. Flow). In the operation of the aerobic tank 29, a DO sensor (dissolved oxygen concentration meter) is installed in the tank, and the DO meter, computer based on the measured value (DO value range is approximately 0.5 to 5 mg / L). Therefore, it is desirable to automatically control the rotation speed of the aeration blower and adjust the air flow rate. In this case, when the DO concentration is low, the blowing amount is increased, and when the DO concentration is high, the blowing amount is decreased. This index can also be performed by ORP or pH. In the case of ORP, in the range of approximately +50 to +300 mV, the amount of air flow is increased when it is low as in the case of DO, and the amount of air flow is decreased when it is high. In the case of pH, it is generally in the range of 6.4 to 7.2. In contrast to DO and ORP, when it is low, the sending amount is decreased, and when it is high, the blowing amount is increased. By performing such an operation, stable and efficient oxidative decomposition of residual BOD, nitrification of nitrogen component, and excessive intake removal of phosphorus can be performed in the aerobic tank 29. In addition, you may adjust ventilation volume not only by the rotation speed of an aeration blower but by operation of a motor operated valve or the number of blower operation.
[0026]
Further, in the fourth embodiment, instead of the solid-liquid separator 22, an immersion type membrane membrane separation means of the separating device or the like (not shown) into the aerobic tank 29 may be provided. As the separation membrane, various separation membranes such as a microfiltration membrane can be used as long as they can separate and filter suspended microorganisms, SS, and the like in the mixed solution in the aerobic tank 29. Specifically, for example, a Zenon membrane process “MacBio” (Nishihara Institute for Environmental Health) that uses a hollow fiber membrane based on an organic polymer is suitable. This membrane separation means is disposed in the aerobic tank 29 by a submerged membrane separator, so that the sludge adhering to the surface of the membrane can be efficiently peeled off by the air diffuser in the aerobic tank 29. Sometimes, by performing the backwash operation, stable separation performance can be maintained over a long period of time. As the membrane separation means, a membrane separation apparatus installed outside the tank may be used instead of the submerged membrane separation apparatus.
[0027]
In the fourth embodiment, a carrier (not shown) holding microorganisms such as denitrifying bacteria and nitrifying bacteria in sludge at a high concentration may be suspended in the anaerobic tank 28 and the aerobic tank 29. This carrier is mainly made of polyurethane having a three-dimensional shape with a side or diameter of 5 to 30 mm. However, the carrier is not limited to the above shape as long as it has a function of flowing in the tank and holding microorganisms by aeration and stirring. . The microorganisms may be held in a fixed manner by attaching and fixing the microorganisms on the surface or inside of the carrier, or by entrapping and fixing with a carrier material. Furthermore, the material of the carrier can be either an inorganic substance or an organic substance. Of course, the carrier is returned from the aerobic tank 29 to the anoxic tank 28 by the circulation means 30 and circulated. In addition, you may circulate only the aerobic tank liquid mixture except a support | carrier to an anoxic tank.
[0028]
【The invention's effect】
As described above, according to the present invention, the anaerobic sludge is separated into the concentrated sludge and the concentrated separation liquid containing high-concentration phosphorus by the sludge concentration apparatus , and this separation liquid is introduced into the phosphorus removal apparatus . The phosphorus can be reliably removed and recovered without returning to the wastewater treatment system. Moreover, phosphorus removal can be stably and efficiently performed regardless of the inflow situation of the wastewater and the biological treatment situation. In addition, since the amount of processing in the phosphorus removal apparatus is limited to a small amount of concentrated separation liquid, the apparatus can be made compact and the running cost required for the processing can be reduced.
[0029]
Further, according to the present invention, since the sludge drawn out as excess sludge from the sludge concentrating apparatus is already concentrated sludge containing little phosphorus after releasing phosphorus, piping by MAP in the sludge treatment facilities obstruction or equipment Trouble can be avoided in advance.
[Brief description of the drawings]
1 is a flow sheet showing the waste water treatment system that by the first embodiment of the present invention.
2 is a flow sheet showing the waste water treatment system that by the second embodiment of the present invention.
3 is a flow sheet showing the main part of the embodiment waste water treatment system that by the third embodiment of the present invention.
4 is a flow sheet showing the waste water treatment system that by the fourth embodiment of the present invention.
FIG. 5 is a flow sheet showing a conventional wastewater treatment apparatus.
[Explanation of symbols]
1 First sedimentation tank (solid-liquid separation means)
2 Floating sludge reaction tank 3 Anaerobic tank 4 Oxygen-free tank 5 Aerobic tank 6, 7 Stirrer 8 Air diffuser 9 Final sedimentation tank (precipitation separation means)
10 circulating means 11 primary sludge conduit 12a return sludge pipe 12b excess sludge pipe 21 biological reactor 22 solid-liquid separator 23 anaerobic device 24 sludge concentrator 25 phosphorus removal device 26 primary sedimentation 27 acid fermentation apparatus 28 anoxic Tank 29 Aerobic tank 30 Circulation means

Claims (4)

A biological reactor for biological treatment by introducing wastewater;
A solid-liquid separator which separates the organism reactor mixture in the treated water and the separated sludge,
The total amount of the separation sludge separated by the solid-liquid separator was stirred at under anaerobic
An anaerobic device for returning the obtained anaerobic sludge to the biological reaction tank;
A sludge concentrating device for separating a portion of the stirred anaerobic sludge and concentrated sludge and the concentrate separated liquid at該嫌air device,
Introducing the separated concentrated separated solution with the sludge concentrating apparatus,
Waste water treatment system that is characterized in that a phosphorus removal device for removing phosphorus contained in the concentrate separated liquid. An initial sedimentation basin for solid-liquid separation of waste water into supernatant water and precipitated sludge, a biological reaction tank for biological treatment by introducing the supernatant water, and a mixture of the biological reaction tank into treated water and separated sludge A solid-liquid separation device for separation, an acid fermentation device that introduces the precipitated sludge for acid fermentation, and a separation sludge separated by the solid-liquid separation device is stirred under anaerobic together with the effluent discharged from the acid fermentation device An anaerobic device that is returned to the biological reaction tank, a sludge concentrating device that separates a portion of the anaerobic sludge stirred by the anaerobic device into a concentrated sludge and a concentrated separated liquid, and phosphorus contained in the concentrated separated liquid. waste water treatment system that is characterized in that a phosphorus removal apparatus for removing. The biological reaction tank comprises an anaerobic tank provided with stirring means, an aerobic tank provided with aeration means, and a circulation means for circulating the aerobic tank mixed solution to the anoxic tank. waste water treatment system according to 1 or claim 2. Biological reactor is a waste water treatment system of claim 1 or claim 2, characterized in that the intermittent aeration tank provided with aeration means and mixing means.

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