JP2010264424A - Organic wastewater treatment facility and method for operating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and easily reduce the load on a wastewater treatment facility when the organic substance concentration increases in a short time in raw water flowing into the wastewater treatment facility. <P>SOLUTION: The organic wastewater treatment facility includes a former stage solid-liquid separation device for separating solids from the raw water, a biological treatment tank for decomposing with activated sludge an organic substance in the water separated in the former stage solid-liquid separation device, and a latter stage solid-liquid separation device for separating the biologically treated liquid obtained in the biological treatment tank into sludge and treated liquid. When the organic substance concentration is over a prescribed value in the raw water, part of the excess sludge obtained in the latter stage solid-liquid separation device is mixed with the raw water before the inlet port of the former stage solid-liquid separation device. The soluble organic substance in the raw water is adsorbed and/or biologically decomposed by the mixed excess sludge. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic wastewater treatment facility capable of suppressing an increase in the organic matter concentration of effluent water even when the concentration of soluble organic matter in raw water increases, and an operating method of such an organic wastewater treatment facility.

  In a general wastewater treatment method such as sewage, first, raw water to be treated is allowed to flow into an initial sedimentation tank (initial sedimentation basin), and solid matter is precipitated and separated. The solid is first settled at the bottom of the settling tank and then discharged out of the tank, and the supernatant water is discharged from the vicinity of the water surface and supplied to the biological treatment tank. Next, in the biological treatment tank, anaerobic and / or aerobic microorganisms are used to decompose organic substances in the treated water in the biological treatment tank. The biological treatment liquid in the biological treatment tank is supplied to a final sedimentation tank (final sedimentation tank) to precipitate and separate activated sludge. And supernatant water is taken out from the water surface vicinity of a final sedimentation tank, and is discharged | emitted out of a treatment facility as treated water.

  In such a wastewater treatment method, countermeasures against load fluctuations are also necessary. For example, Patent Document 1 discloses that a buffer tank is provided to cope with an increase in the amount of wastewater inflow. Further, in Patent Document 2, when the sewage flow rate suddenly increases due to rain or the like, the supernatant water of the final sedimentation tank is circulated between the front biological treatment tank for anaerobic treatment and the rear biological treatment tank for aerobic treatment. A method is disclosed in which the remaining supernatant is allowed to flow into the subsequent biological treatment tank without passing through the previous biological treatment tank.

  Surplus sludge generated in the final sedimentation tank is said to account for about half of industrial waste, and measures to reduce its volume have been studied. For example, in Patent Document 3, microbial electron acceptor adjustment water is mixed in raw wastewater, and the amount of dissolved oxygen is aerated under a condition of substantially 1 mg / L or less. A treatment apparatus has been proposed for carrying out a treatment method in which the amount of aeration is substantially 1 mg / L or less and the supernatant water is returned to the wastewater raw water as electron acceptor adjustment water.

  Moreover, in a biological treatment facility for organic wastewater, organic matter is decomposed by two biological treatment tanks, a first-stage biological treatment tank and a second-stage biological treatment tank, in order to cope with load fluctuations, and after being processed in the first-stage biological treatment tank. Lead the mixed water to the water quality measurement tank, and use the measured value of the dissolved oxygen sensor to determine the excess or deficiency of the mixed water flowing into the latter biological treatment tank with the treatment capacity of the latter biological treatment tank. A method for controlling the amount of aeration in the tank is disclosed in Patent Document 4.

JP-A-5-192688 JP 2005-262140 A Japanese Patent No. 3667254 JP 2008-161855 A

  If the organic matter concentration in the raw water increases, the aeration rate in the aerobic biological treatment tank is increased, or the organic matter concentration in the treated water is adjusted by adjusting the temperature, pH, etc. to activate the biological treatment of organic matter with activated sludge. It is possible to suppress the rise of However, depending on the source of the raw water, the concentration of soluble organic substances in the raw water may rise rapidly.

  In such a case, in the methods disclosed in Patent Documents 1 to 3, it is difficult to suppress an increase in the organic matter concentration of the discharged water of the wastewater treatment facility when the concentration of the soluble organic matter in the raw water increases rapidly. It is. In addition, even in the method disclosed in Patent Document 4, it is impossible to increase the biological treatment capacity suddenly even if the aeration amount of the previous biological treatment tank is increased, so the concentration of soluble organic matter in the raw water has increased rapidly. In some cases, the organic matter concentration in the discharged water becomes high, and the water quality is inevitably deteriorated.

  An object of the present invention is to provide an organic wastewater treatment facility that can easily and quickly cope with a rapidly increasing concentration of dissolved organic matter in raw water, and an operation method of such an organic wastewater treatment facility.

  The present inventor has the ability to adsorb soluble organic matter in the activated sludge, so that it is possible to reduce the load on the biological treatment tank by mixing the excess sludge, which is the surplus of activated sludge, with the raw water and separating the solid content. The headline and the present invention have been completed.

Specifically, the present invention
A first-stage solid-liquid separation device for separating solids in raw water;
A biological treatment tank for decomposing organic matter in the separated water obtained by the former solid-liquid separator with activated sludge;
A subsequent solid-liquid separation device for separating the biological treatment liquid obtained in the biological treatment tank into sludge and treated water;
In an organic wastewater treatment facility comprising
When the organic matter concentration of the raw water exceeds a predetermined concentration, a part of the excess sludge obtained in the latter-stage solid-liquid separator is mixed with the raw water before the inflow portion of the former-stage solid-liquid separator. The present invention relates to a method for operating an organic wastewater treatment facility.

The present invention also provides:
A first-stage solid-liquid separation device for separating solids in raw water;
A biological treatment tank for decomposing organic matter in the separated water obtained by the former solid-liquid separator with activated sludge;
A subsequent solid-liquid separation device for separating the biological treatment liquid obtained in the biological treatment tank into sludge and treated water;
An organic wastewater treatment facility comprising:
Provide a surplus sludge supply path for mixing a part of the surplus sludge obtained in the latter solid-liquid separator with the raw water,
Normally, the surplus sludge supply route is closed,
The present invention relates to an organic wastewater treatment facility characterized in that when the organic matter concentration of raw water exceeds a predetermined concentration, the surplus sludge supply path is opened and a part of the surplus sludge is mixed with raw water.

  In the latter-stage solid-liquid separator, the sludge in the biological treatment tank is separated, and the excess is removed by being extracted as excess sludge. This surplus sludge contains aerobic microorganisms that adsorb and / or decompose soluble organic matter.

  In the present invention, during normal times (that is, when the organic matter concentration of the raw water is equal to or lower than the design concentration of the organic wastewater treatment facility), excess sludge extracted from the subsequent solid-liquid separation device is discarded and exceeds a predetermined concentration ( If the organic matter concentration in the raw water exceeds the design concentration of the organic wastewater treatment facility), a part of the excess sludge extracted from the solid-liquid separator is mixed with the raw water, and the excess sludge is adsorbed and removed by the excess sludge. To do.

  Moreover, since the excess sludge has a low soluble organic substance concentration, it can exhibit a high treatment capacity for raw water having a high soluble organic substance concentration. For this reason, in this invention, it is possible to adsorb | suck and / or decompose | disassemble efficiently the soluble organic substance in raw | natural water with the excess sludge mixed with raw | natural water.

  The excess sludge mixed with the raw water is adsorbed and / or decomposed with the soluble organic matter in the raw water, and then separated into solids and separated water by the former solid-liquid separator. The separated solids are extracted from the former solid-liquid separation device and discarded together with the organic solids contained in the raw water, so that the dissolved organic matter adsorbed on the excess sludge is the latter aerobic biological treatment tank. Will not flow into. For this reason, since the increase in the organic substance load to the biological treatment tank can be suppressed, deterioration of the treated water quality can be suppressed, and in the case of aerobic biological treatment, an increase in the aeration amount (an increase in the aeration electric energy associated therewith) can also be suppressed. .

  The outlet side of the surplus sludge supply path is connected to the raw water supply path of the former solid-liquid separator, and if raw water and surplus sludge are mixed and supplied into the former solid-liquid separator, the flow force of the raw water can be used. Therefore, it is possible to sufficiently stir excess sludge without a special device such as a stirrer.

Excess sludge concentration to be added to the raw water to flow into the front solid-liquid separator is preferably adjusted to be 0.03 kg-SS / m ³ or more 0.2kg-SS / m ³ or less.

  According to the organic wastewater treatment facility and the method of operating the same of the present invention, it is possible to easily and quickly reduce the load on the biological treatment tank even when the concentration of organic matter in the raw water increases rapidly.

It is a figure which shows the processing flow at the normal time in an example of the organic wastewater treatment facility of this invention. It is a figure which shows the processing flow at the time of load increase in an example of the organic wastewater treatment facility of this invention. It is a figure explaining the structure of the organic waste water treatment facility of Embodiment 2. FIG. It is a graph showing the TOC measurement result of supernatant water when changing the stirring time and the excess sludge mixing ratio. It is a graph showing the S-TOC measurement result of supernatant water in the case of changing stirring time and excess sludge mixing rate. It is a graph showing the TOC measurement result of supernatant water in stirring time 1 minute. It is a graph showing the S-TOC measurement result of supernatant water in stirring time 1 minute. It is a graph showing the amount of TOC removal by excess sludge. It is a graph showing the TOC removal rate by excess sludge. It is a graph showing the amount of S-TOC removal by excess sludge. It is a graph showing the S-TOC removal rate by excess sludge. It is a graph showing the amount of TOC removal per unit weight of excess sludge. It is a graph showing the TOC removal rate per unit weight of excess sludge.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The present invention is not limited to the following description.

<Embodiment 1>
(Normal time)
First, FIG. 1 shows a treatment flow in a sewage treatment plant as an organic wastewater treatment facility equipped with a first settling tank, an aerobic biological treatment tank as a first-stage solid-liquid separation apparatus, and a final settling tank as one latter-stage solid-liquid separation apparatus. This will be explained based on. The raw water (organic waste water) is temporarily stored in the raw water tank 2 from the path 1 and then supplied to the first sedimentation tank 4 via the path 3. In the first settling tank 4, suspended substances and the like are removed by precipitation.

  First, the supernatant water of the sedimentation tank 4 is supplied to the aerobic biological treatment tank 6 via the path 5. In the aerobic biological treatment tank 6, air is blown into the wastewater by the blower 7, and the organic matter in the wastewater is aerobically biodegraded by the activated sludge. After the treatment for a certain time, the biological treatment liquid in the aerobic biological treatment tank 6 is supplied to the final sedimentation tank 9 via the path 8.

  Since the activated sludge from the aerobic biological treatment tank 6 flows into the final sedimentation tank 9, the activated sludge gradually settles at the bottom of the final sedimentation tank 9. The supernatant water of the final sedimentation tank 9 is discharged via the path 10 as treated water. Part of the sludge that has settled at the bottom of the final sedimentation tank 9 is returned to the aerobic biological treatment tank 6 through the sludge return path 12 as return sludge. By this return, the amount of activated sludge in the aerobic biological treatment tank 6 can be maintained within a certain range.

  Moreover, the excess of the sludge settled at the bottom of the final sedimentation tank 9 is appropriately extracted from the path 11 as excess sludge and discarded.

  The surplus sludge supply path 13 is also connected to the path 11, and the side opposite to the connection portion with the path 11 (the surplus sludge outlet side) is connected to the path 3. Although the valve 14 is provided in the sludge return path 12, the valve 14 is normally closed, and a part of the excess sludge taken out from the path 11 is not supplied to the raw water.

(When load increases)
Next, the supply of surplus sludge to the raw water when the concentration of soluble organic matter in the raw water rises to a level exceeding the treatment capacity of the organic wastewater treatment facility will be described with reference to FIG. In addition, the part regarding the supply to the raw | natural water of the excess sludge by the excess sludge supply path | route 13 which is a difference with the normal time is demonstrated here.

  When the organic matter concentration in the raw water increases, the treatment capacity of the aerobic biological treatment tank 6 is insufficient, and the organic matter cannot be sufficiently biodegraded. For this reason, the biological treatment liquid having a high concentration of dissolved organic matter flows into the final sedimentation tank 9, and as a result, the concentration of soluble organic matter in the treated water discharged from the path 10 also becomes higher than the reference value, and the quality of the treated water is deteriorated. It will be. If the aeration amount of the aeration apparatus 18 is increased, the treatment capacity of the aerobic biological treatment tank 6 can be improved to some extent. However, when the organic substance concentration is rapidly increased, the treatment is performed due to biodegradation using aerobic microorganisms. It is difficult to improve ability suddenly.

  Therefore, in the present invention, if the organic substance concentration exceeds a predetermined value, the valve 14 is opened, and a part of the excess sludge extracted from the path 11 is passed through the excess sludge supply path 13 and the path 3 to the initial settling tank 4. Return it. The organic matter concentration of the raw water is measured by an organic matter concentration meter 16 installed in the raw water tank 2 in FIG. The signal of the organic substance concentration meter 16 is transmitted to the valve 14 through the path 17 and the opening / closing of the valve 14 is adjusted.

  The dissolved organic matter concentration of raw water is preferably measured in real time with an organic matter concentration meter, but the COD (chemical oxygen demand) specified in JIS K0102 (Factory Wastewater Test Method) is regularly measured. It is also possible to adjust the opening / closing of the valve 14 according to the measurement result. Further, the correlation between the soluble organic substance concentration and the electric conductivity may be grasped in advance, and the organic substance concentration may be calculated by measuring the electric conductivity.

  Since the excess sludge supply path 13 and the path 3 are connected, the raw water and the excess sludge are supplied in a mixed state from the path 3 to the first settling tank 4 by the force of the raw water flow. For this reason, in the first settling tank 4, raw water and excess sludge can be stirred without a stirring device. In addition, it is preferable that the time from mixing raw water and excess sludge to supplying it to the first settling tank 4 is 30 seconds or more.

  About 30 seconds are required to mix the raw water and surplus sludge to the best mixing state with the power of the raw water flow, but even if it is less than that, mixing proceeds after the feed to the first settling tank 4, The organic substance removal effect is exhibited.

  The surplus sludge mixed with the raw water adsorbs the soluble organic matter in the raw water while first flowing into the settling tank 4, and settles to the bottom of the first settling tank 4 after flowing into the first settling tank 4. At this time, surplus sludge has the ability to biodegrade organic matter in the sedimentation tank 4 at the beginning, so that dissolved oxygen in raw water is used even in the absence of aeration treatment other than adsorption and removal of organic matter. Biodegradation of organic matter can be expected.

  At this time, the excess sludge that has first settled at the bottom of the settling tank 4 is extracted from the sludge discharge path 15 while adsorbing the organic matter. It does not flow into the aerobic biological treatment tank 6 at the subsequent stage.

  First, the organic matter in the raw water is adsorbed and / or biodegraded in the sedimentation tank 4, so that the organic matter concentration in the supernatant water supplied to the aerobic biological treatment tank 6 via the path 5 is reduced and the raw water is dissolved. Even when the concentration of the organic organic substance is rapidly increased, it is possible to suppress the rapid increase in the load of the aerobic biological treatment tank 6.

The supply of excess sludge through the excess sludge supply path 13 is preferably performed when the organic matter concentration of raw water exceeds 10% of the design treatment concentration of the organic wastewater treatment facility. At this time, the amount of excess sludge added to the raw water flowing into the preceding solid-liquid separator is 0.03 to 0.2 kg-SS of excess sludge per 1 m ^{3 of} raw water. That is, excess sludge concentration in the raw water after the addition is preferably adjusted to be 0.03 kg-SS / m ³ or more 0.2kg-SS / m ³ or less.

  When the concentration of the dissolved organic matter in the raw water decreases and returns to the normal concentration, the valve 14 is closed by a signal from the organic matter concentration meter 16 installed in the raw water tank 2 and the return of excess sludge through the sludge return path 13 is stopped. Thus, the normal operation is resumed.

  The first settling tank 4 may be replaced with a membrane separator, and the final settling tank 9 may be replaced with a membrane separator.

<Embodiment 2>
In the first embodiment, the aerobic biological treatment tank and the final sedimentation tank (the latter solid-liquid separation device) are independent structures, but as shown in FIG. 3, the aerobic biological treatment tank, the solid-liquid separation device, May be an integrated structure. In the example of FIG. 3, the supernatant of the sedimentation tank 22 supplied via the path 5 is filtered by the submerged membrane separation device 19 after the organic matter is biodegraded by the activated sludge method in the membrane separation activated sludge treatment device 21. Then, the permeated water is drained from the path 20 as treated water.

  Although the sludge concentration of the treatment liquid gradually increases by filtration by the submerged membrane separation device 19, the excess sludge in the membrane separation activated sludge treatment device 21 is appropriately extracted from the sludge passage 11, so that the sludge concentration is within a certain range. It is possible to adjust. Note that the sludge return route is not required in the organic wastewater treatment facility of FIG.

  A portion of the excess sludge extracted from the sludge path 11 is mixed into the raw water via the excess sludge supply path 13 and the path 3 as in the first embodiment when the concentration of soluble organic matter in the raw water increases. The

  In addition, as the submerged membrane separation device 19 of the membrane separation activated sludge treatment device 21, a known membrane separation device such as a precision membrane separation device or an ultrafiltration membrane separation device can be used. Moreover, you may replace the precipitation tank 22 with a membrane separator.

  The operation method of the organic wastewater treatment facility of the present invention can also be implemented in an existing organic wastewater treatment facility by a simple modification of providing an excess sludge supply path.

  In the first embodiment and the second embodiment, the case where the biological treatment is performed in the aerobic biological treatment tank alone has been described. However, the anaerobic biological treatment tank and the aerobic biological treatment tank may be combined.

(Load reduction experiment using excess sludge)
In an organic wastewater treatment facility, it was assumed that surplus sludge was mixed with raw water when the concentration of dissolved organic matter in the raw water increased, and the raw water and surplus sludge from the final sedimentation tank were charged into a beaker and stirred for a certain time with a stirring blade. After standing for 60 minutes, the supernatant water was collected. Then, the suspended solids concentration (SS), total organic carbon concentration (TOC), and soluble total organic carbon concentration (S-TOC) were measured. Table 1 shows SS, TOC and S-TOC of raw water and excess sludge.

  Moreover, as shown in Table 2, the mixing ratio of excess sludge (raw sludge extracted from the final sedimentation tank) to the raw water was set to 0 to 20% by volume. The stirring time of the raw water and excess sludge was 1 to 20 minutes.

  First, the measurement results of the TOC concentration and S-TOC concentration of the filtrate when the stirring time of raw water and excess sludge is 1 to 20 minutes and the excess sludge mixing ratio is 1 to 20% by volume are shown in FIG. As shown in FIG. It was confirmed that the higher the excess sludge mixing ratio, the lower the TOC concentration and S-TOC concentration of the filtrate, but almost no influence was found due to the stirring time. The same experiment was conducted with a stirring time of 30 seconds, but the TOC concentration and S-TOC concentration of the filtrate were almost the same as the stirring time of 1 minute.

Next, the measurement results of the TOC concentration and S-TOC concentration of the filtrate when the excess sludge concentration in the raw water is changed from 0.03 to 0.8 kg-SS / m ³ and the stirring time is 1 minute are shown in the figure. 6 and FIG. The higher the excess sludge concentration, the lower the TOC and S-TOC of the filtrate. In addition, when the stirring time was in the range of 30 seconds to 20 minutes, the TOC and S-TOC of the filtrate did not change much.

Next, the TOC removal amount and the TOC removal rate when the excess sludge concentration in the raw water is changed from 0.03 to 0.8 kg-SS / m ³ and the stirring time is 1 minute are shown in FIGS. 8 and 9, respectively. . The S-TOC removal amount and the S-TOC removal rate are shown in FIGS. 10 and 11, respectively. The behavior of TOC and S-TOC concentration changes was similar, and no significant difference was observed regarding whether the organic matter was solid or soluble. As the excess sludge concentration increased, the removal amount and removal rate of TOC and the like increased.

Next, when the excess sludge concentration in the raw water is changed from 0.03 to 0.8 kg-SS / m ³ and the stirring time is 1 minute, the TOC removal amount and S-TOC removal amount per unit weight of excess sludge They are shown in FIGS. 12 and 13, respectively. As the excess sludge concentration increased, the removal efficiency of TOC and S-TOC per unit weight of excess sludge decreased rapidly.

Therefore, as excess sludge concentration in the first settling tank is 0.03kg-SS / m ³ or more 0.8kg-SS / m ³ or less, mixing the raw water and excess sludge, the TOC and S-TOC removal rate It was considered practical to drive at around 15%.

  The organic wastewater treatment facility and the operation method thereof according to the present invention are useful in the wastewater treatment field as an organic wastewater treatment facility and an operation method thereof in which the organic matter concentration of raw water is likely to vary.

1,3,5,8,10,20: Path 2: Raw water tank 4: First sedimentation tank (front solid-liquid separation device)
6: Aerobic biological treatment tank 7: Blower 9: Final sedimentation tank (second-stage solid-liquid separator)
11, 15: Sludge route 12: Surplus sludge supply route 13: Sludge return route 14: Valve 16: Organic substance concentration meter 17: Route (electric route)
18: Aeration device (aeration device)
19: Submerged membrane separation device 21: Membrane separation activated sludge treatment device (aerobic biological treatment tank + solid-liquid separation device)
22: Settling tank

Claims (5)

A first-stage solid-liquid separation device for separating solids in raw water;
A biological treatment tank for decomposing organic matter in the separated water obtained by the former solid-liquid separator with activated sludge;
A subsequent solid-liquid separation device for separating the biological treatment liquid obtained in the biological treatment tank into sludge and treated water;
In an organic wastewater treatment facility comprising
When the organic matter concentration of the raw water exceeds a predetermined concentration, a part of the excess sludge obtained in the latter-stage solid-liquid separator is mixed with the raw water before the inflow portion of the former-stage solid-liquid separator. , Operation method of organic wastewater treatment facility. Adjusting the excess sludge concentration to be added to the raw water to flow into the front solid-liquid separation device such that 0.03 kg-SS / m ³ or more 0.2kg-SS / m ³ or less, an organic waste water treatment according to claim 1 How to operate the facility. A first-stage solid-liquid separation device for separating solids in raw water;
A biological treatment tank for decomposing organic matter in the separated water obtained by the former solid-liquid separator with activated sludge;
A subsequent solid-liquid separation device for separating the biological treatment liquid obtained in the biological treatment tank into sludge and treated water;
An organic wastewater treatment facility comprising:
Provide a surplus sludge supply path for mixing a part of the surplus sludge obtained in the latter solid-liquid separator with the raw water,
Normally, the surplus sludge supply route is closed,
An organic wastewater treatment facility characterized in that when the organic matter concentration of raw water exceeds a predetermined concentration, the surplus sludge supply path is opened and a part of the surplus sludge is mixed with raw water.   The organic wastewater treatment facility according to claim 3, wherein an outlet side of the surplus sludge supply path is connected to a raw water supply path of a preceding solid-liquid separator. Adjusting the excess sludge concentration to be added to the raw water to flow into the front solid-liquid separation device such that 0.03 kg-SS / m ³ or more 0.2 kg-SS / m ³ or less, organic according to claim 3 or 4 Wastewater treatment facility.

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