JPH09138229A - Respiration rate meter with cleaning mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a respiration rate meter whose measuring accuracy is increased by eliminating an error cause due to aerobic microorganisms in an activated sludge liquid which is stuck to the inside of a respiration rate measuring tank. SOLUTION: In the respiration rate meter, the activated sludge liquid is introduced into the measuring tank 14 by the opening and shutting operation of an upper-part pinch valve V1 and a lower-part pinch valve V2 which are installed additionally at the measuring tank 14 and by an air lift action, and the breathing speed of the activated sludge liquid is measured by the aeration operation of the activated sludge liquid and by the measuring operation of a dissolved oxygen(DO) concentration. In this case, the respiration rate meter is constituted in such a way that an ozone injection port 22 is arranged and installed at the measuring tank 14, that the breathing speed of the activated sludge liquid is measured, that ozone gas is then supplied into the measuring tank 14 and that a sterilizing and cleaning operation is performed. A shutter 20a which prevents damage due to the ozone gas is attached to a part facing the measuring tank 14 of a DO electrode 20 as a dissolved-oxygen-concentration detection part. In addition, after the respiration rate of the activated sludge liquid has been measured, a surface-active agent as a cleaning liquid is injected so as to perform the cleaning operation of an inside wall surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a respiratory rate meter with a cleaning mechanism used for controlling activated sludge process.

[0002]

2. Description of the Related Art Various methods have conventionally been proposed for efficiently removing organic matter in wastewater such as sewage and removing nitrogen and phosphorus which are considered to be the causative agents of eutrophication in closed water areas. However, recently, it is required to increase the removal rate of nitrogen in particular, and regulations on nitrogen are expected to become stricter.Therefore, the number of facilities adopting advanced treatment processes that can remove this will increase. it is conceivable that.

In order to deal with such a situation, an activated sludge circulation modified method is attracting attention as a modified method of the conventional standard activated sludge method as a method for biologically removing nitrogen and phosphorus simultaneously. The modified activated sludge circulation method is, for example, as shown in FIG. 2, the biological reaction tanks are anaerobic tanks 1a and 1b in which dissolved oxygen (hereinafter abbreviated as DO) does not exist, and a plurality of aerobic tanks in which DO exists. Partitioned into 2a, 2b and 2c, this anaerobic tank 1a,
1b, the inflowing raw water 3 is agitated by an agitation mechanism 10 under anoxic condition to denitrify by denitrifying bacteria in the activated sludge, and then scattered inside the aerobic tanks 2a, 2b, 2c. By supplying air from the blower 5 to the trachea 4, oxidative decomposition of organic matter by activated sludge and nitrification of ammonia by nitrifying bacteria are performed in the presence of oxygen by aeration.
Then, the nitrification solution in the last-stage aerobic tank 2c is fed into the anaerobic tank 1a by using the nitrification solution circulation pump 6, whereby the anaerobic tank 1
The denitrification effect in a and 1b is promoted.

Since the activity of the above nitrifying bacteria decreases as the DO concentration decreases, the DO of the last aerobic tank 2c is measured and D
It is customary that the O controller 12 controls the drive of the blower 5.

Reference numeral 7 is a final sedimentation pond. This final sedimentation pond 7
The supernatant liquid is discharged as treated water 11 after passing through a disinfecting tank or the like (not shown), and a part of the sludge settled in the final settling tank 7 is returned to the anaerobic tank 1a by the sludge returning pump 8. Other sludge is sent from the excess sludge drawing pump 9 to an excess sludge treatment device (not shown) for treatment.

[0006] By using such a modified activated sludge circulation method, an effect comparable to the organic matter removal effect achieved by the ordinary standard activated sludge method can be obtained, and nitrogen and phosphorus can be removed more efficiently than the standard activated sludge method. Rate is achieved.

The operation mode in the above circulation type nitrification denitrification method is the denitrification reaction in the anaerobic tanks 1a and 1b and the aerobic tank 2
It can be roughly divided into nitrification reactions in a, 2b, and 2c, but the rate of the reaction is the latter, that is, the nitrification reaction. In particular, in order to efficiently remove nitrogen by the above circulation type nitrification denitrification method, it is required to maintain the denitrification in the anaerobic tank and the nitrification in the aerobic tank under the optimum operating conditions, and the nitrogen removal step is performed in the nitrification step. Since it is highly influenced by the process, it is necessary that the nitrification process is performed well in order to perform good nitrogen removal.

As an evaluation of activity in such an activated sludge process, a respiration rate meter for activated sludge (hereinafter referred to as "Rr meter") is used. The present applicant has previously proposed, in Japanese Patent Application No. 5-104158, an activated sludge treatment device for monitoring the promotion of nitrification using an Rr meter. In this proposal, an Rr meter is installed on the inflow side of the aerobic tank and the change in the nitrification reaction is detected from the measured value.

The measuring principle of the Rr meter is to measure the decrease in dissolved oxygen concentration due to oxygen consumption by aerobic microorganisms accompanying stirring of activated sludge liquid and injection of air, and the least squares method from the rate of decrease of the dissolved oxygen concentration. Respiration rate of activated sludge [R
r] is calculated.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
If the aerobic microorganisms in the activated sludge adhere to the measuring tank, the respiration rate [Rr] will be higher than the actual value and the measurement accuracy will decrease because the respiration rate of the microorganisms will add as an error. There is a fear. In particular, when contaminants such as sludge adhere to the DO electrode that is a detector of dissolved oxygen (DO), auxiliary equipment such as a stirrer, or the measuring tank itself and multiply, the sludge concentration in the sample water apparently increases. This may cause a measurement error. Therefore, in the standard activated sludge method, it is usually necessary to perform sterilization and cleaning work in the measuring tank once a day using a chemical such as sodium hypochlorite.

However, the optimum injection rate of the above chemicals is determined by the concentration of activated sludge in the test water, the concentration of ammonia nitrogen, or the pH.
Since it changes depending on the conditions, etc., it is often injected excessively, and since the activated sludge liquid is contained in the measuring tank after washing, the liquid in the measuring tank is returned to the aeration tank in order to process this. Since the method is used, the amount of chemicals used is large, and the influence of chemicals on the process becomes a problem.

Further, when carrying out sterilization cleaning using chemicals, it is necessary to raise the Rr meter once from the aeration tank to frequently clean the DO electrode portion in the measuring tank, especially in the aerobic tank. When the Rr meter is installed on the side, dirt does not easily come off, which requires complicated maintenance and has the drawback that a stable measurement value cannot always be obtained.

[0013] Therefore, an object of the present invention is to provide a respiration rate meter with a cleaning mechanism, in which the error factor of the respiration rate due to aerobic microorganisms in the activated sludge adhering to the measuring tank is eliminated to improve the measurement accuracy. Is.

[0014]

In order to achieve the above object, the present invention introduces an activated sludge liquid into the measuring tank by opening / closing operation of an upper pinch valve and a lower pinch valve attached to the measuring tank and an air lift action. In the device for measuring the respiration rate of the activated sludge liquid by aerating the activated sludge liquid and measuring the dissolved oxygen concentration, an ozone inlet is provided in the measuring tank as claimed in claim 1, The respiratory rate meter with a cleaning mechanism is configured such that the ozone gas obtained by the ozone generator is supplied into the measuring tank after the respiratory rate is measured to perform the cleaning operation. A shutter for preventing damage due to ozone gas at the time of cleaning is attached to a portion of the DO electrode serving as the dissolved oxygen concentration detecting portion facing the measuring tank.

According to a third aspect of the present invention, there is provided a respiration rate meter with a cleaning mechanism, which comprises measuring the respiration rate of the activated sludge solution and then injecting a surfactant as a cleaning solution to clean the inner wall surface of the measuring tank. To do.

[0016]

[Function] According to such a respiratory rate meter with a cleaning mechanism, an air lift is formed in the measuring tank with the introduction of air, and then the activated sludge liquid is introduced into the measuring tank by opening and closing the upper pinch valve and the lower pinch valve. When the dissolved oxygen concentration is increased by aeration and then the aeration is stopped and the stirring is performed, the dissolved oxygen concentration decreases with the oxygen consumption by the aerobic microorganisms of the activated sludge. The respiration rate of activated sludge is calculated from the decrease rate by the method of least squares.

After that, the shutter of the DO electrode and the lower pinch valve are closed to open the ozone inlet, and the ozone gas obtained by the ozone generator is fed into the measuring tank through the ozone inlet, and the stirring operation by the stirrer is performed inside the measuring tank. Perform the sterilization and washing step of. As a result, the aerobic microorganisms in the activated sludge adhering to the inside of the measuring tank are killed by performing the cleaning process using ozone gas having a sterilizing action, so that the accuracy of the next measurement can be improved.

Furthermore, the cleaning effect can be further enhanced by using a surfactant instead of the conventional chemical such as sodium hypochlorite as the cleaning liquid.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, each embodiment of a respiration rate meter with a cleaning mechanism according to the present invention will be described in detail with reference to the drawings, in which the same reference numerals are given to the same components as the above-mentioned conventional components. FIG. 1 is a vertical sectional side view of the first embodiment, in which 13a is a water collecting port, 13
Reference numeral b is a drainage port, 14 is a measuring tank, and tubes 15 and 16 forming a water passage on the inlet and outlet sides of the measuring tank 14.
Are connected.

V ₁ is an upper pinch valve, V ₂ is a lower pinch valve, and 17, 18 and 19 are air inlets. The tubes 15 and 16 are in a pinch state by injecting and exhausting air from the air inlets 17 and 19. Then, the activated sludge liquid is opened and closed. Reference numeral 20 is a DO electrode as a dissolved oxygen concentration detector, and 21 is a stirrer. A shutter 20 a is attached to the DO electrode 20 so as to face the measuring tank 14.

Further, in this embodiment, the ozone inlet 22 is provided in the measuring tank 14 so that the ozone gas O ₃ obtained by the ozone generator (not shown) is supplied into the measuring tank 14.

Although not shown in the drawing, an injection box for the ATU chemical liquid or the cleaning liquid, a compressor for supplying air, and a control panel are arranged outside the respiration rate meter.

When measuring the respiration rate of activated sludge,
As a basic operation, first, air is introduced from the air inlet 18 to form an air lift, the pinch valves V ₁ and V ₂ are opened, and the activated sludge liquid in the aerobic tank (not shown) is used as the sample water from the water sampling port 13a. It is introduced into the measuring tank 14. Next, the air inlet 17
After closing the lower pinch valve V ₂ by injecting air from the inside, air is sent from the air inlet 18 into the measuring tank 14 for aeration, and the DO concentration is kept at a certain constant value, for example, 5 (mg / mg / mg).
up to l).

When the DO concentration rises to the set value, the aeration is stopped, the upper pinch valve V ₁ is closed by the injection of air from the air injection port 19, and the stirring by the stirrer 21 is started. Then, the DO concentration decreases as oxygen is consumed by the activated sludge (aerobic microorganisms).
The respiration rate [Rr] is calculated by the least square method from the rate of decrease of DO measured by the electrode 20. At the time of this measurement, the ozone inlet 22 is closed.

At the time of measurement, an ATU (N-allylthiourea) reagent is injected into the measuring tank 14, air is again aerated from the air inlet 18 to increase the DO concentration to a set value, and then the aeration is stopped. The upper pinch valve V ₁ was closed and stirring was performed by the stirrer 21 to measure the decrease in DO concentration due to oxygen consumption due to activated sludge.
r] and [ATU-Rr] value by calculation,
From the difference between the obtained [Rr] value and [ATU-Rr] value, [N
It-Rr] is calculated.

Thus, [Rr] and [ATU-R]
After the measurement of the [r] value, the shutter 20a of the DO electrode 20 and the lower pinch valve V ₂ are closed to open the ozone inlet 22, and ozone gas obtained by an ozone generator (not shown) is supplied from the ozone inlet 22 to the measuring tank 14 Send in. Then, the stirring by the stirrer 21 is performed to perform the sterilizing and cleaning step in the measuring tank 14. The reason for closing the shutter 20a of the DO electrode 20 is to prevent the thin film forming the DO electrode from being damaged by ozone gas.

After the cleaning process is completed, air is introduced again from the air inlet 18 to form an air lift, and the pinch valve V
₁ , open V ₂ and introduce the activated sludge liquid as sample water into the measuring tank 14 from the water sampling port 13a, close the lower pinch valve V ₂ by injecting air from the air injecting port 17, and then from the air injecting port 18. The operation of sending air into the measuring tank 14 and aerating is repeated.

As described above, in the present embodiment, by cleaning the inside of the measuring tank 14 with ozone gas having a sterilizing action, the aerobic microorganisms in the activated sludge adhering to inside the measuring tank 14 are killed and the next time. The measurement accuracy of can be improved.

Next, a second embodiment of the present invention will be described. The second embodiment is characterized in that a surfactant is used as the cleaning liquid instead of the conventional chemical such as sodium hypochlorite. As described above, the respiration rate [Rr] and [ATU-
After measuring the Rr] value, the lower pinch valve V ₂ is closed, a surfactant is introduced into the measuring tank 14, and stirring is performed by the stirrer 21 to carry out the washing step in the measuring tank 14.

After the cleaning step, air is again introduced from the air inlet 18 to form an air lift to drain the mixed solution of the surfactant and the activated sludge from the drain 13b, and when the drain is finished, the lower pinch valve V ₂ is closed and the washing process is completed.

The measurement operation using the above ATU solution will be briefly described. The oxygen utilization rate (Rr) is the amount of oxygen consumed during the oxidative decomposition of organic matter and the endogenous respiration of activated sludge. The amount of oxygen consumed and the amount of oxygen consumed in the nitrification reaction are included, and this value is the respiratory rate due to removal of organic substances and endogenous respiration, that is, the total oxygen consumption rate minus the oxygen consumption rate associated with the nitrification reaction. It is expressed as a value. Therefore, the progress of the nitrification reaction should be determined from the difference [Rr] and the Rr difference [ATU-Rr] measured by adding the nitrification inhibitor N-allylthiourea (chemical formula C ₄ H ₈ N ₂ S, ATU). You can

If the above difference is [Nit-Rr], then generally [Nit-Rr] = [Rr]-[ATU-Rr] (1). That is, the [Nit-Rr] value is the oxygen consumption rate associated with nitrification, and if this value is small, the nitrification reaction will end,
If it is larger, it can be judged that the nitrification reaction has not ended. Since the above [Nit-Rr] represents the oxygen consumption based on the nitrification reaction, it is possible to estimate the nitrification rate in the aerobic tank from this value.

[0033] Normally, the sample water sampled from the aerobic tank [AT
The oxygen consumption rate [Nit-Rr] value involved in the nitrification reaction is measured by the [U-Rr] value.
Based on the value, it is determined whether or not the nitrification reaction has ended. That is, when the nitrification reaction proceeds smoothly and the concentration of ammonia nitrogen decreases, the above [Nit-Rr] value also sharply decreases, which indicates that the nitrification reaction in the aerobic tank is completed.

On the other hand, when the measured oxygen consumption rate [Nit-rr] value for the nitrification reaction is large, the [ATU-Rr] value is one in which the nitrification reaction in the aerobic tank is not completed. Is judged. At this time, the driving of the stirring mechanism of the anaerobic tank is stopped and the amount of air blown to the aerobic tank is controlled to carry out aeration so as to reach the ideal nitrification rate.

[0035]

As described in detail above, according to the respiratory rate meter with a cleaning mechanism according to the present invention, an air lift is formed in the measuring tank to introduce the activated sludge liquid into the measuring tank for aeration, After increasing the dissolved oxygen concentration, aeration is stopped and agitation is performed, and the dissolved oxygen concentration decreased with the oxygen consumption by the aerobic microorganisms of the activated sludge is measured. After calculating the respiratory rate, D
By closing the shutter of the O electrode and opening the ozone injection port, and feeding ozone gas into the measuring tank and stirring, the sterilizing and cleaning step in the measuring tank can be performed. In particular, the aerobic microorganisms in the activated sludge adhering to the inside of the measuring tank are killed during the cleaning process using ozone gas having a bactericidal action, so that the accuracy of the next measurement can be improved. Furthermore, the cleaning effect can be further enhanced by using a surfactant instead of a conventional chemical such as sodium hypochlorite as the cleaning liquid.

Therefore, the respiration rate of the aerobic microorganisms in the activated sludge adhering to the measuring tank does not cause an error, and contaminants may adhere to the DO electrode as a detector or an auxiliary device such as a stirrer. Since it is prevented, frequent cleaning work as in the conventional case is unnecessary, maintenance can be simplified, and adverse effects on the process due to excess chemicals can be eliminated.

From the obtained respiration rate of the activated sludge, the establishment of an efficient operation control method for sufficiently enhancing both the nitrification efficiency in the aerobic tank used in the sewage treatment plant and the denitrification efficiency in the anaerobic tank associated therewith Can be measured,
It can be used not only as a modified activated sludge circulation method but also as monitoring for promoting the denitrification reaction in the standard activated sludge method.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional side view showing a respiratory rate meter with a cleaning mechanism according to an embodiment.

FIG. 2 is a schematic diagram showing an example of a normal circulation type nitrification denitrification method.

[Explanation of symbols]

13a ... Water sampling port 13b ... Drain port 14 ... Measuring tank 15, 16 ... Tube V ₁ ... Upper pinch valve V ₂ ... Lower pinch valve 17, 18, 19 ... Air injection port 20 ... DO electrode 20a ... Shutter 21 ... Stirrer 22 ... Ozone inlet

Claims (3)

[Claims] 1. An activated sludge liquid is introduced into the measuring tank by opening and closing operations of an upper pinch valve and a lower pinch valve attached to the measuring tank and an air lift action, and aeration operation to the activated sludge liquid and measurement of dissolved oxygen concentration are performed. In an apparatus for measuring the respiration rate of activated sludge liquid by operation, an ozone inlet is provided in the above-mentioned measurement tank, and after measuring the respiration rate of the activated sludge liquid, ozone gas obtained by an ozone generator is supplied into the measurement tank. Respiratory rate meter with a cleaning mechanism, characterized in that it is designed to perform cleaning work. 2. The respiratory rate meter with a cleaning mechanism according to claim 1, wherein a shutter for preventing damage due to ozone gas during cleaning is attached to a portion of the DO electrode as the dissolved oxygen concentration detecting section facing the measuring tank. 3. The activated sludge liquid is introduced into the measurement tank by the opening / closing operation of the upper pinch valve and the lower pinch valve attached to the measurement tank and the air lift action, and the aeration operation to the activated sludge liquid and the measurement of the dissolved oxygen concentration are performed. In the device for measuring the respiration rate of the activated sludge liquid by operation, after measuring the respiration rate of the above activated sludge liquid, a surfactant was injected as a cleaning liquid to perform the cleaning work on the inner wall surface of the measurement tank. Respiratory rate meter with a characteristic cleaning mechanism.