JPH03224696A - Control method of anaerobic/aerobic waste water treating device - Google Patents

Abstract

PURPOSE:To maintain good effluent water quality throughout the year regardless of the concn. of the org. matter in waste water by controlling an aeration air flow rate so as to be proportional to the amt. of the generated gaseous methane. CONSTITUTION:An anaerobic treating device 4 which utilizes immobilized anaerobic microorganisms 3 and an aerobic treating device 6 which is supplied with oxygen by aeration air and utilizes the aerobic microorganisms 5 are disposed successively in this order. The amt. M of the generated gaseous methane is determined by measuring the flow rate G of a digester gas 13 generated from the device 4 and the concn. C of the gaseous methane in the digester gas 13 and calculating the value of GXC as the product thereof at the time of subjecting a specified flow rate of the org. waste water to a cleaning treatment. The aeration air of the flow rate proportional to this value M is sent to the device 6. As a result, the good effluent water quality is maintained throughout the year regardless of the concn. of the org. matter during dehydration and the aeration of the aerobic treatment method is executed by the min. required aeration energy.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to biological treatment of organic industrial wastewater and sewage, particularly when performing wastewater treatment using both anaerobic and aerobic microorganisms. This invention relates to a method for controlling the amount of aeration air.

[Conventional technology]

Wastewater treatment using anaerobic microorganisms has long been applied to organic wastewater with extremely high concentrations, but in recent years, advances have been made in the development of technology to immobilize anaerobic microorganisms. It has also come to be applied to industrial wastewater. Upflow anaerobic sludge blanket method (UAS) using self-immobilization is an anaerobic treatment technology for low-concentration organic wastewater.
B method).

Anaerobic fluidized bed method, anaerobic fixed bed method, etc. are known.

However, even if such treatment methods are used, it is difficult to purify wastewater to a high level, and usually an aerobic treatment device that supplies oxygen is connected in series to finish the treatment with aerobic microorganisms. The aerobic treatment methods used for this purpose include the activated sludge method and the aerobic fixed bed method.

FIG. 4 is a schematic diagram showing the arrangement of the main components of a fixed bed type anaerobic and aerobic wastewater treatment apparatus, and arrows represent the water travel route and the power transmission route from the control panel. This device is equipped with an adjustment tank 1 to equalize the flow rate and a raw water pump 2 in it. 6. Aerobic biological reactor filled with aerobic fixed bed 5 for finishing treatment. Furthermore, it is comprised of a final sedimentation tank 7 in which the final solid-liquid separation step is performed. In addition, an inverter for adjusting the air flow rate8. QI air blower 9 air flow meter 10. A control panel 11 is also provided.

Next, the process of treating wastewater 12 in this device will be described. The wastewater 12 first enters the regulating tank 1, where the flow rate is equalized, and the raw water pump 2 causes a constant flow rate to flow into the bottom of the anaerobic biological reaction tank 4. Since the aerobic biological reaction tank 4 initially also serves as a settling tank, the wastewater 12 is subjected to solid-liquid separation treatment to remove coarse solids, and then slowly flows in an upward flow through the anaerobic fixed bed 3. #s The air fixed bed 3 is filled with microbial carriers made of nonwoven fabric, porous ceramics, etc.
Since the anaerobic fixed bed is fixed, the organic matter in the wastewater 12 undergoes methane fermentation here, and the digestion gas 13 is generated, which is released from the upper part of the anaerobic biological reaction tank 4.

By removing coarse solids and methane fermentation, 50 to 70% of the organic matter in the wastewater 12 is removed in the anaerobic biological reaction tank 4. The anaerobic treated water 14 that exits here then flows into the aerobic biological reaction tank 6. In the aerobic biological reaction tank 6, most of the remaining organic matter is removed by the action of aerobic microorganisms immobilized on the aerobic fixed bed 5 made of nonwoven fabric, corrugated plastic plate, or the like. The amount of aerated air for supplying oxygen to the aerobic biological reaction tank 6 is set assuming the case where the load on the aerobic fixed bed 5 is the highest, and is set on the assumption that the load on the aerobic fixed bed 5 is the highest. The amount of air is determined using an inverter 8, and the air flow rate sent from the aeration block is monitored by an air flow meter 10.The treated water that has been purified in this way then flows into the final settling tank 7, where it is Solid matter such as microbial flocs is removed by gravity sedimentation, and effluent water 15 is obtained.Furthermore, each reaction tank 4,
6. Sludge generated from the final settling tank 7 is extracted from the bottom as surplus sludge 16 and treated separately.

[Problem to be solved by the invention]

Above, we have explained the outline of the equipment and treatment process for treating organic wastewater using a combination of anaerobic treatment method and aerobic treatment method, but this wastewater treatment process still has the following problems to be solved. There is. In order to obtain good treated water quality using this equipment, it is necessary to adjust the operating conditions of the equipment to effectively respond to fluctuations in water quality.For example, factory cafeteria wastewater is an example of organic industrial wastewater. Since the number of employees in a factory is constant, the amount of wastewater does not change much, but the concentration of organic matter contained in it is greatly influenced by the daily menu. In this way, when treating wastewater whose water quantity does not change much but whose water quality fluctuates, the wastewater treatment equipment is also required to have an operating method that accommodates the fluctuations in water quality.

However, wastewater treatment equipment incorporating an anaerobic treatment method has not yet been developed, and an effective operation control method has not yet been established. Therefore, when treating wastewater with equipment that combines anaerobic fixed bed method and aerobic fixed bed method, it is currently possible to maintain the specified treated water quality even when the mobile concentration of wastewater is at its highest. Set operating conditions,
It continues to operate under these conditions. That is, regardless of whether the organic matter concentration in wastewater is high or low, the reality is that the equipment is always operated in accordance with the conditions when the organic matter concentration is high. Looking at the aeration air flow rate for supplying oxygen to the aerobic biological reaction tank 6 in the latter stage, as mentioned above, it is set assuming the highest load, so it usually results in overaeration. There is. Therefore, although the amount of aeration air can be reduced when the concentration of organic matter in wastewater is low, in reality, a considerable amount of aeration energy is wasted. In addition, in a state of excessive aeration, the biofilm on the aerobic fixed bed 5 is likely to peel off, and this becomes suspended solids (SS), resulting in the inconvenience of deteriorating the quality of the treated water.

Another different example is when wastewater from a food factory with varying water quality is treated using a combination of the UASB method and the activated sludge method. ing. Therefore, in this case as well, overaeration often occurs and aeration energy is wasted.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, to maintain good effluent quality throughout the year regardless of the concentration of organic matter in wastewater, and to utilize the aerobic treatment method using minimal aeration energy. An object of the present invention is to provide a method for controlling an anaerobic and aerobic wastewater treatment device that can perform aeration.

Means for Solving Problem C11] In order to solve the above problems, the control method of the present invention includes an anaerobic treatment method that uses immobilized anaerobic microorganisms in the first stage, and a floating state or immobilized state in the second stage. When treating wastewater using an anaerobic and aerobic wastewater treatment system that combines an aerobic treatment method that uses aerobic microorganisms to supply oxygen through aeration, the flow of digestion gas generated from an anaerobic biological reaction tank! (G), methane gas concentration in digestion gas (C)
, and calculate the product GxC of these values to determine the amount of methane gas generated (M), and determine the flow rate of air aerated to the aerobic biological reaction tank in proportion to the value of M. .

[Effect]

From the relationship between the amount of methane gas generated and the BOD of anaerobically treated water obtained through research by the present inventors, it was found that there is a proportional relationship between them. Since the relationship diagram with the load can also be regarded as a straight line, the control method of the present invention is performed as follows.

That is, the relationship holds that the anaerobic treated water BOD is determined from the amount of methane gas generated, the aerobic fixed bed BODjL load is determined from the anaerobic treated water BOD, and once the aerobic fixed bed BOD load is determined, the aeration air flow rate is determined. In other words, a good proportional relationship is established between the amount of methane gas generated and the flow rate of warm air, and in the present invention, by controlling the flow rate of aeration air so that it is proportional to the amount of methane gas generated, a good proportional relationship is established. Water quality is maintained.

〔Example〕

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

First, we will describe the progress that led to the achievement of the present invention. The present inventors have been conducting research on anaerobic and aerobic wastewater treatment for many years, and have studied its treatment characteristics. 1st
The figure is a diagram showing the relationship between the amount of methane gas generated and the BOD of anaerobically treated water, as a result obtained by the present inventors from a Viloft plant experiment (processed water amount: 36 g+''/day) aimed at treating domestic wastewater. Figure 1 shows the amount of methane gas generated by the anaerobic fixed bed method and the anaerobic treatment BOD when the water temperature is almost constant.
A certain proportional relationship holds true between the two, indicating that the greater the amount of methane gas generated, the higher the BOD. From this relationship, the present inventors came up with the idea that the amount of methane gas generated is a powerful indicator of the quality of water treated by the anaerobic fixed bed method.

On the other hand, Figure 2 shows the processing characteristics of the aerobic fixed bed method.

In Figure 2, the vertical axis represents the air flow rate F required to maintain good treated water quality, multiplied by the amount of treated water to make it dimensionless, and the horizontal axis represents the BOD load in the aerobic fixed bed method. FIG.

FIG. 2 shows that the required air amount F changes from Fl to Ft along a curve a. Here, if b is a straight line connecting points PI+Pg corresponding to F+ and Pg on curve a, the straight line can be treated as being very close to curve a within the range of Pl and P8. This means that when the load changes from t to z, there is no problem in practice even if the air flow rate F is changed along a straight line.

To summarize the above ideas, as shown in Figures 1 and 2, the anaerobic treated water BOD is determined from the methane gas generation amount M, and the aerobic fixed bed BOD load can be determined from the anaerobic treated water BOD, so the aerobic fixed bed BOD load is Once this is determined, the aeration air amount F is determined. In other words, there is a good proportional relationship between the methane gas generation amount M and the aeration air amount F, and if the aeration air amount F is controlled in proportion to the methane gas generation amount M, good water quality can be maintained. The conclusion was reached.

The arrangement of the main components of the fixed bed type anaerobic and aerobic wastewater treatment equipment to which the method of the present invention is applied is shown in the schematic diagram of Figure 3.The equipment of Figure 3 is basically the same as that of Figure 4. 4, the same reference numerals are used for the same parts as in Fig. 4. However, the parts that differ from Fig. 4 in terms of device configuration are the digestion gas 13 coming out of the anaerobic biological reaction tank 4 as measurement control related parts. Gas flow meter 17. to measure the amount of gas generated. A methane gas analyzer 18 is added to analyze the methane gas concentration in the digestion gas 13,
Also, the control signal path is shown by a dotted arrow.

Here, with reference to FIG. 3, only the steps necessary for the present invention will be described below. In implementing the method of the present invention based on the above-mentioned idea of the present inventors, it is first necessary to determine the amount of methane gas generated. Therefore, the gas flow rate (G) is measured with the gas flow meter 17, and the methane gas analyzer 18 is used to measure the gas flow rate (G). Measure the methane gas concentration (C). At this time, for example, a wet gas meter with an oscillator is used as the gas flow meter 17,
As the methane gas analyzer 18, it is appropriate to use, for example, an infrared process gas analyzer. Each measurement result is sent to the control panel 11, where the amount of methane gas generated can be determined as GXC-M.

In addition, in FIG. 1, M is the amount of methane gas generated per amount of treated water, but in this example, since the flow rate of the waste water 12 is constant, the total amount of methane gas generated may be taken as M. The amount of air (F) is calculated according to the following formula.

F=αM + F m1nt However, F m1ni
≦F≦F malα is a proportionality constant specific to the device and can be determined experimentally. F m1ni is the lower value of the aeration air amount, and F aa is the upper limit value. F□1
, is set as the minimum flow rate to maintain the aerobic biological reaction tank 6 normally. On the other hand, F, . . . is a value corresponding to the assumed maximum value of M. α, F, 8ゎ, IF! 1m
There is no need to change g if the water temperature is almost constant throughout the year, but if the water temperature changes, for example, it should be divided into high water temperature periods and low water temperature periods and set accordingly. This is a measure taken because the treatment characteristics of each biological reaction tank change as the water temperature changes, but it can be done relatively easily by a person familiar with the target water treatment equipment.

When the aeration air amount F is determined as described above, the inverter 8. Aeration blower9. Air flow meter 10. A feedback loop consisting of the control panel 11 controls the amount of aerated air F, and air aeration for supplying oxygen to the aerobic biological reaction tank 6 is performed.

The control method according to the present invention for an anaerobic and aerobic wastewater treatment apparatus has been described above using a fixed bed type as an example, but the present invention can also be applied to apparatuses other than fixed bed type. Similar effects can be obtained using the UASB method or the anaerobic fluidized bed method. This is because, like the fixed bed method, these methods utilize immobilized anaerobic microorganisms, so the relationship shown in Figure 1 is observed between the amount of methane gas generated and the BOD of treated water. This is because it will be done. On the other hand, an activated sludge method can also be applied to the latter aerobic treatment. It is generally known that in the activated sludge method, it is desirable to increase or decrease the amount of aeration air depending on the load.
Since the aeration air flow rate curve can be approximated as shown in the figure, the control method of the present invention is also effective in this case.

〔Effect of the invention·〕

An anaerobic treatment system has an anaerobic treatment device that uses immobilized anaerobic microorganisms in the first stage, and an aerobic treatment device that uses suspended or immobilized aerobic microorganisms in the second stage and supplies oxygen through aeration, arranged in this order. By pneumatic wastewater treatment equipment,
When purifying wastewater, an operation control method when the water quality fluctuates has not yet been established, and conventionally, the amount of aeration air is determined in response to the highest load conditions, and the flow rate is maintained regardless of load fluctuations. However, this resulted in a large waste of aeration energy and caused a deterioration in the quality of the treated water. In contrast, the control method of the present invention, which was made to solve this problem, has the following advantages.

The present invention was obtained as a result of deep research into anaerobic wastewater treatment methods, and measures the amount of methane gas generated from an anaerobic treatment device, and adjusts the amount of air aerated to the aerobic treatment device in proportion to the amount of methane gas generated. Because we used a method of controlling the flow rate, when the amount of methane gas generated increases, the air flow rate also increases to cope with the increase in load, and when the amount of methane gas generated decreases, the air flow rate also decreases, resulting in an overaeration state. This greatly contributes to energy conservation. This also has the great effect of consistently maintaining good water quality during the treatment period.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the amount of methane gas generated and the BOD of anaerobic treated water, Figure 2 is a diagram showing the relationship between the required amount of aeration air and the BOD of the aerobic fixed bed method, and Figure 3 is a diagram showing the relationship between the amount of methane gas generated and the BOD of anaerobic treated water. A schematic diagram showing the arrangement of the main components of a fixed bed type anaerobic and aerobic wastewater treatment equipment to which the method is applied. Figure 4 shows the main components of a conventional fixed bed type anaerobic and aerobic wastewater treatment equipment. It is a schematic diagram showing the arrangement of. 1: 1 Jii tank, 2: Raw water pump, 3: Anaerobic fixed bed, 4: Anaerobic biological reaction tank, 5: Aerobic fixed bed, 6: Aerobic biological reaction tank, 7: Final sedimentation tank, 8: Inverter , 9:
Aeration blower, 10: Air flow meter, u: Control panel, 12: Waste water, 13: Digestion residue, 14: tl! Air treatment air hydraulic water 5: Effluent water, 16: Excess sludge, 17: Gas flow meter, 18: Methane gas analysis needle. Anaerobic and water-rehydration BOD (哩l) 1st fertilization and aerobic f'i Shu'B Hiroshi BOD Yuka L (reduction price 'g) Fig. 2

Claims (1)

[Claims] 1) Using an anaerobic and aerobic wastewater treatment device in which an anaerobic treatment device that uses immobilized anaerobic microorganisms and an aerobic treatment device that supplies oxygen with aeration air and uses aerobic microorganisms are arranged in series in this order. When purifying a constant flow rate of organic wastewater, the flow rate (G) of the digestion gas generated from the anaerobic treatment device and the methane gas concentration (C) in the digestion gas are measured, and the product of these is G×C. A method for controlling an anaerobic and aerobic wastewater treatment device, characterized in that the amount of methane gas generated (M) is determined by calculating the value of M, and the aerated air at a flow rate proportional to the value of M is sent to the aerobic treatment device. .