JP2966166B2 - Anaerobic water treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anaerobic water treatment apparatus for anaerobically treating wastewater such as raw water and industrial wastewater.

[0002]

2. Description of the Related Art An anaerobic water treatment method using methane bacteria, which is an anaerobic bacterium, has a problem that it takes a long time to treat wastewater due to a low decomposition rate of organic substances. However, in order to solve such a problem, a carrier having a size of about 0.1 to 1 mm to which bacteria (methane bacteria) are attached is filled in the reactor, and raw water introduced from a lower portion of the reactor is partially mixed with the carrier. BACKGROUND ART A fluidized bed anaerobic water treatment apparatus that performs wastewater treatment by flowing a carrier by circulating treated water has been proposed.

[0003] Since this fluidized bed anaerobic water treatment apparatus can attach a large amount of bacteria to a carrier, good wastewater treatment can be performed with a short residence time.

However, methane bacteria are obligately anaerobic bacteria,
The activity is lost by touching very little oxygen. Therefore, the reactor is required to have high airtightness. However, the gas piping of the reactor is often opened for maintenance or the like, and the inadequacy of the maintenance may cause an air mixing accident. In particular, methanogens are responsible for the final stage of anaerobic fermentation and are extremely sensitive to oxygen. Acid will accumulate and the pH of the reaction system will drop,
Since the optimum pH for growth of methanogens is near neutrality, such a drop in pH may be inhibited by pH. For this reason, if there is an air mixing accident,
Due to the synergistic adverse effects of the above-mentioned inhibiting factors, the water treatment efficiency is extremely deteriorated.

In a conventional anaerobic water treatment apparatus, when air enters the reactor system and methane bacteria are deactivated by contact with oxygen, nitrogen gas or the like is sealed in the reactor system to purge oxygen. The reactor system must be returned to the anaerobic state again, the load must be stopped, and the recovery of the bacterial cell activity must be waited.In the worst case, the seed cells must be re-introduced and the reactor must be restarted. did not become.

[0006]

In the above-described anaerobic water treatment apparatus, the load must be stopped or the reactor must be restarted if there is an accident of air in the reactor. However, the operation requires a lot of time and a large amount of cost, and the wastewater that cannot flow into the wastewater treatment facility must be separately treated.

The present invention has been made in view of such conventional problems, and has as its object to automatically cope with the incorporation of air into the reactor system and to maintain an anaerobic state in the reactor system. It is another object of the present invention to provide an anaerobic water treatment apparatus capable of maintaining a good water treatment state without lowering the cell activity by lowering the input load.

[0008]

In order to achieve the above object, an anaerobic water treatment apparatus according to the present invention comprises: a reactor for holding anaerobic bacteria inside and purifying introduced wastewater; A treated water tank for storing the treated water that overflows, a circulating pump that circulates a portion of the treated water in the treated water tank to the bottom of the reactor, and stores wastewater, and a part of the wastewater is stored in the bottom of the reactor. A raw water pump to be introduced, a fermentation gas holder for storing the fermentation gas generated in the reactor, and one end opened to the gas phase of the fermentation gas holder, and the other end to the liquid phase of the reactor and the treatment water tank. A fermentation gas introduction pipe provided so as to open to the liquid phase part of the above, a gas introduction blower disposed on the fermentation gas introduction pipe, and oxidation reduction in the liquid phase part of the reactor and the treatment water tank. A measuring device for measuring the position, and an arithmetic and control unit for controlling the activation of the blower when the oxidation-reduction potential of the measuring device is equal to or higher than a preset reference value, and for reducing and controlling the flow rate of the raw water pump. It is provided with.

Further, the anaerobic control device according to the present invention is characterized in that the arithmetic and control unit determines whether the blower has been activated when the oxidation-reduction potential measured by the measuring device is larger than a set value and the time derivative thereof is positive. The flow rate of the raw water pump may be reduced, and the blower may be stopped and the flow rate of the raw water pump may be increased when the oxidation-reduction potential is smaller than a set value and the time derivative is negative. it can.

[0010]

In the anaerobic water treatment apparatus according to the present invention, the oxidation-reduction potential of the liquid phase portion of the reactor is measured at any time by a measurement device for the oxidation-reduction potential, and the fluctuation of the oxidation-reduction potential is calculated and monitored by the arithmetic and control unit.

When the oxidation-reduction potential in the reactor system exceeds a preset value, or when the oxidation-reduction potential exceeds the preset value and the time derivative of the oxidation-reduction potential is positive, the preset value is set. The blower is started by the arithmetic and control unit so as to adjust the oxidation-oxidation-reduction potential to a value obtained in the above-mentioned manner, and is adjusted so as to reduce the inflow of the raw water pump. This makes it possible to maintain the cell activity by controlling the oxidation operation potential in the reactor system to be equal to or lower than the set value and reduce the organic substance load applied to the cells, thereby maintaining the water treatment efficiency.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention. An anaerobic water treatment apparatus shown in FIG. 1 includes a raw water tank 1 for temporarily storing waste water, a raw water pump 2 for advancing the waste water in the raw water tank 1, and a waste water from the raw water tank 1 And a reactor 3 for introducing the gas into the inside.

The reactor 3 has a high concentration of methane bacteria therein and decomposes organic matter contained in wastewater into methane and carbon dioxide via lower fatty acids.

The anaerobic water treatment apparatus also includes wastewater (treated water) in which organic substances contained are decomposed and purified in the reactor 3.
Water tank 4 for temporarily storing the overflow of water, a circulating pump 5 for returning part of the processing water stored in the water tank 4 to the bottom of the reactor 3, and fermentation of methane, carbon dioxide, etc. generated in the reactor 3. A gas holder 6 for temporarily storing gas is provided.

The anaerobic water treatment apparatus further includes a measuring device 7 mounted inside the reactor 3 and the treatment water tank 4 for measuring the oxidation-reduction potential (ORP) of each liquid phase.
a, 7b, receiving signals from these measuring devices 7a, 7b, performing an arithmetic processing described later, giving a control signal to the blower 8, and transferring the fermentation gas stored in the gas holder 6 to the reactor 3 and the treatment water tank 4. An arithmetic and control unit 9 for controlling the amount to be sent to the liquid phase unit is provided.

Next, the operation of the anaerobic water treatment apparatus having such a configuration will be described.

After the wastewater is temporarily stored in the raw water tank 1,
The raw water pump 2 introduces the reactor 3 from the bottom into the inside, and the organic matter in the wastewater is decomposed into methane and carbon dioxide via lower fatty acids by the methane bacteria group maintained at a high concentration. It is stored once in the holder 6.

On the other hand, the purified wastewater overflows from the upper part of the reactor 3 and is discharged through the treated water tank 4. A part of the purified wastewater is returned from the treated water tank 4 to the bottom of the reactor 3 by the circulation pump 5.

The outputs of the oxidation-reduction potential measuring devices 7a and 7b installed in the reactor 3 and the treatment water tank 4 for measuring the oxidation-reduction potential of each liquid phase are supplied to the arithmetic and control unit 9. And this arithmetic and control unit 9
Performs a calculation process as described below based on signals from the oxidation-reduction potential measuring devices 7a and 7b, outputs a control signal to the blower (B) 8, and transfers the fermentation gas stored in the gas holder 6 to the reactor 3 or The amount sent to the liquid phase portion of the treatment water tank 4 is controlled.

Next, the operation of the arithmetic and control unit 9 will be described.

The oxidation-reduction potential inside the reactor 3 and the treatment water tank 4 is measured at any time by the oxidation-reduction potential measuring devices 7a and 7b, and the arithmetic and control unit 9 monitors the change of the oxidation-reduction potential. The arithmetic and control unit 9 outputs a flow control signal to the blower 8 so as to maintain a preset oxidation-reduction potential and controls the flow control signal. At the same time, the arithmetic and control unit 9 controls the flow rate of the raw water pump 2 according to the change rate of the oxidation-reduction potential.

The control of the blower 8 and the raw water pump 2 will be described in more detail. The oxidation-reduction potential of the liquid phase portion of the reactor 3 and the treated water tank 4 is measured at regular intervals by the oxidation-reduction potential measuring devices 7a and 7b, and the arithmetic and control is performed. The time differential value of the oxidation-reduction potential at each time is obtained by the device 9.

Therefore, when the time derivative is positive and the oxidation-reduction potential value at each time exceeds a preset value, the oxidation-reduction potential in the reactor system has increased, that is, It is determined that mixing has occurred, and the arithmetic and control unit 9
To drive the blower 8 to introduce the fermentation gas stored in the gas holder 6 into the liquid phase portion of the reactor 3 and the treatment water tank 4 to lower the oxidation-reduction potential in the reactor system. At the same time, the flow rate of the raw water pump 2 is reduced according to the change rate of the oxidation-reduction potential.

Conversely, if the time derivative is negative and the oxidation-reduction potential value at each time falls below a preset value, it is determined that the oxidation-reduction potential in the reactor system has decreased, The blower 8 is stopped by the arithmetic and control unit 9 to stop the introduction of the fermentation gas. At this time, the flow rate of the raw water pump 2 is again adjusted by the arithmetic and control unit 9 to a value before the flow rate is reduced, after a predetermined time from the time when it is determined that the oxidation-reduction potential has returned to the set value.

In this way, the oxidation-reduction potential in the reactor system is brought close to a preset value, and the load applied to the cells is adjusted.

According to the present embodiment, since the oxidation-reduction potential in the reactor system can be maintained in a range suitable for methane fermentation, it is possible to maintain the bacterial cell activity even when an accident such as air mixing occurs. In addition, when the oxidation-reduction potential increases, the load on the cells is reduced, and conversely, the load is increased after a certain period of time when the oxidation-reduction potential returns to the set value. Can be prevented from being deactivated. In this way, good water treatment can be maintained.

The present invention can be applied to any of a fluidized bed type and a fixed bed type as long as a part of the treated water is circulated to the reactor.

The set value of the oxidation-reduction potential in the reactor system is approximately -250 mV, but it may vary depending on the plant. Therefore, it is desirable to determine the value by conducting preliminary experiments and the like. In addition, since the rate of decrease in the flow rate of raw water and the time interval until the load is restored also differ depending on the plant and the organic matter load at that time, it is desirable to determine in detail by preliminary experiments, etc. The reduction rate of the raw water flow rate is 20 to 50%, and the time required to restore the load is several hours to several days.

Further, in the above embodiment, the blower and the raw water pump are controlled in consideration of both the measured value of the oxidation-reduction potential itself and the time derivative thereof, but a simple and strict control is not required. If the measured value of the oxidation-reduction potential is higher than the set value, start the blower, reduce the flow rate of the raw water pump, and conversely, restore the oxidation-reduction potential to another lower set value. For example, a control method that returns to the original control may be adopted.

[0031]

As described above, according to the present invention, the oxidation-reduction potential of the liquid phase portion of the reactor is measured at any time by the oxidation-reduction potential measuring device, and the fluctuation of the oxidation-reduction potential is calculated and monitored by the arithmetic and control unit. Therefore, when the oxidation-reduction potential in the reactor system exceeds a preset value and the time derivative of the oxidation-reduction potential is positive, the arithmetic and control unit adjusts the oxidation-reduction potential to the preset value. Control the blower and quickly and automatically adjust it to reduce the flow rate of the raw water pump, thereby reducing the oxidation-reduction potential in the reactor system even if an air mixing accident occurs in the reactor system. The degree of oxygen inhibition given to methane bacteria can be suppressed to the minimum by controlling to automation below the set value. In addition, by reducing the organic substance load applied to the cells that have been subjected to oxygen inhibition, the cell activities can be maintained, and good water treatment can always be maintained.

Further, in the present invention, since the fermentation gas generated in the water treatment is used as the gas for purging oxygen introduced into the reactor system, the cost as the purging gas is not required, and it is economical.

Further, since the fermentation gas is directly introduced into the reactor system from the gas tank by a blower, the equipment can be simplified and the construction cost is economical.

[Brief description of the drawings]

FIG. 1 is a flowchart of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water tank 2 Raw water pump 3 Reactor 4 Treatment water tank 5 Circulation pump 6 Gas holder 7a, 7b Oxidation reduction potential measuring instrument 8 Blower 9 Arithmetic controller

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-270792 (JP, A) JP-A-62-160193 (JP, A) JP-A-5-50088 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C02F 3/28-3/34

Claims (2)

(57) [Claims] 1. A reactor for holding anaerobic bacteria therein and purifying introduced wastewater, a treated water tank for storing treated water overflowing from above the reactor, and one of treated water in the treated water tank. A circulation pump that circulates a part to the bottom of the reactor, a raw water pump that stores wastewater, and introduces a part of the wastewater to the bottom of the reactor, and a fermentation gas holder that stores fermentation gas generated in the reactor. A fermentation gas introduction pipe provided such that one end is opened in a gas phase portion of the fermentation gas holder and the other end is opened in a liquid phase portion of the reactor and a liquid phase portion of the treated water tank; A gas introduction blower disposed on a gas introduction pipe, a measuring device for measuring an oxidation-reduction potential in a liquid phase portion of the reactor and the treatment water tank, and an oxidation-reduction potential set by the measurement device is preset. And the blower start control and when it becomes more than the reference value is, and the reducing control the flow rate of the raw water pump operation control device and anaerobic water treatment device including a. 2. The arithmetic and control unit according to claim 1, wherein when the oxidation-reduction potential measured by the measuring device is larger than a set value and the time derivative thereof is positive, the blower is started and the raw water pump flow rate is reduced. The anaerobic water treatment apparatus according to claim 1, wherein when the oxidation-reduction potential is smaller than a set value and a time derivative thereof is negative, the blower is stopped and the flow rate of the raw water pump is increased.