JP3538960B2 - Respiratory rate meter with washing mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Various methods have heretofore been proposed for efficiently removing organic matter in wastewater such as sewage and removing nitrogen and phosphorus, which are considered to be substances causing eutrophication in closed water bodies. However, recently it has been required to increase the nitrogen removal rate in particular, and it is expected that regulations on nitrogen will be stricter, so the number of facilities adopting advanced treatment processes capable of removing nitrogen will increase. it is conceivable that.

In order to cope with such a situation, as a method of biologically removing nitrogen and phosphorus at the same time, a circulating nitrification and denitrification method is receiving attention as a modification of the conventional standard activated sludge method. This circulation type nitrification denitrification method is, for example, as shown in FIG. 2, a biological reaction tank is composed of 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. 2a, 2b, and 2c.
1b, the inflowing raw water 3 is agitated by the agitation mechanism 10 under anoxic condition to perform denitrification by denitrifying bacteria in the activated sludge, and then dispersed in the aerobic tanks 2a, 2b, 2c. By supplying air from the blower 5 to the trachea 4, oxidative decomposition of organic substances by activated sludge and nitrification of ammonia by nitrifying bacteria are performed in the presence of oxygen by aeration.
The nitrification liquid in the last aerobic tank 2c is fed into the anaerobic tank 1a by using the nitrification liquid circulation pump 6, whereby the anaerobic tank 1c is discharged.
The denitrification effect in a and 1b is promoted.

Since the activity of the nitrifying bacteria decreases as the DO concentration decreases, the DO of the last aerobic tank 2c is measured to determine
Generally, the drive of the blower 5 is controlled by the O control device 12.

[0005] Reference numeral 7 denotes a final sedimentation basin.
The supernatant is discharged as treated water 11 through a disinfection tank or the like (not shown), and part of the sludge settled in the final sedimentation basin 7 is returned to the anaerobic tank 1a by the sludge return pump 8; Other sludge is sent from the surplus sludge extraction pump 9 to a surplus sludge treatment device (not shown) and processed.

By using such a recirculation type nitrification and denitrification method, the same effect as the organic substance removal effect achieved by the ordinary standard activated sludge method can be obtained, and nitrogen and phosphorus can be removed at a higher removal rate than the standard activated sludge method. Rate is achieved.

The operation of the above-mentioned recirculation type nitrification and denitrification method includes the denitrification reaction in the anaerobic tanks 1a and 1b and the aerobic tank 2
The nitrification reaction can be roughly classified into the nitrification reactions in a, 2b, and 2c, and the latter, that is, the nitrification reaction, is the rate-determining reaction. In particular, in order to efficiently remove nitrogen by the above-mentioned circulating nitrification denitrification method, it is necessary to maintain denitrification in an anaerobic tank and nitrification in an aerobic tank under optimal operating conditions. Since the degree of influence by the process is high, it is necessary that the nitrification process be performed well in order to perform good nitrogen removal.

As an evaluation of the activity in such an activated sludge process, a respiratory rate meter for activated sludge (hereinafter referred to as "Rr meter") is used. Conventionally, an apparatus shown in FIG. 3 has been used to automatically measure the respiration rate [Rr]. Briefly describing this structure and operation, 13a is a water sampling port, 13b is a drain port, 14 is a measuring tank, and tubes 15 and 16 forming a water passage are connected to the inlet and outlet sides of the measuring tank 14. I have. V ₁ is the upper pinch valve, V ₂ is the lower pinch valve, 17, 18, 1
Reference numeral 9 denotes an air inlet, and the tubes 15 and 16 are brought into a pinched state and a released state by the injection and exhaust of air from the air inlets 17 and 19, so that opening and closing operations are performed. Reference numeral 20 denotes a DO electrode as a dissolved oxygen concentration detection unit, and 21 denotes a stirrer.

When measuring the respiration rate of activated sludge,
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 introduced into the measuring tank 14 from the water sampling port 13a. Next, the lower pinch valve V ₂ is closed by injecting air from the air inlet 17, and air is sent from the air inlet 18 into the measuring tank 14 to be aerated, so that the DO concentration becomes a certain value, for example, 5 (mg / mg). l).

When the DO concentration rises to the set value, the aeration is stopped, and the upper pinch valve V ₁ is closed by injecting air from the air inlet 19 to start stirring by the stirrer 21. Then, the DO concentration decreases with oxygen consumption by activated sludge (aerobic microorganisms).
The respiration rate [Rr] is calculated by the least squares method from the rate of decrease of DO measured by the electrode 20 and a DO meter (not shown).

[0011]

SUMMARY OF THE INVENTION Such a conventional Rr
When the aerobic microorganism in the activated sludge adheres to the measuring tank, the respiration rate of the microorganism is added as an error, so that the respiration rate [Rr] value becomes higher than the actual value and the measurement accuracy is reduced. There is fear. In particular, if contaminants such as sludge grow on attached equipment such as the DO electrode 20 or the stirrer 21 which is a detector in the measuring tank 14 or the measuring tank 14 itself,
The sludge concentration in the apparently sampled water has increased, which may cause measurement errors. Therefore, in the standard activated sludge method, the sterilization and cleaning operation in the measuring tank 14 must usually be performed once a day using a chemical such as sodium hypochlorite.

However, the optimum injection rate of the above chemicals depends on the concentration of activated sludge, ammonia nitrogen concentration or pH
In general, excessive injection is often performed, and activated sludge liquid is contained in the measurement tank 14 after washing. Therefore, the liquid in the measurement tank 14 is supplied to the aeration tank in order to treat the activated sludge liquid. Since the means of returning is used, the amount of use of the chemical increases, and the influence of the chemical on the process becomes a problem.

Further, when performing sterilization cleaning using chemicals, the Rr meter must be once pulled out of the aeration tank to frequently clean the DO electrode portion in the measurement tank 14, which requires complicated maintenance. In addition, there is a problem that a stable measurement value cannot always be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a respiratory rate meter with a washing mechanism which has improved measurement accuracy by eliminating an error factor of respiratory rate due to aerobic microorganisms in activated sludge adhering to a measuring tank. It is.

[0015]

In order to achieve the above object, the present invention introduces an activated sludge liquid into a measuring tank by opening and closing an upper pinch valve and a lower pinch valve attached to the measuring tank and by an air lift action. In the apparatus for measuring the respiration rate of the activated sludge by aerating the activated sludge and measuring the dissolved oxygen concentration, an ATU liquid injection pipe and tap water are connected to the measurement tank via a third pinch valve. By connecting the injection pipe and the cleaning liquid injection pipe, after measuring the respiration rate of the activated sludge liquid, the cleaning tank and the tap water were injected to wash the inner wall surface of the measuring tank, and then the measuring tank was filled with tap water. Provided is a configuration of a respiratory rate meter with a washing mechanism, which keeps the state of being kept ready for the next measurement.

The respiration rate is measured by measuring the decrease in the dissolved oxygen concentration due to the consumption of oxygen by the aerobic microorganisms accompanying the stirring of the activated sludge and the injection of air. This is a value obtained by subtracting the oxygen consumption rate associated with the nitrification reaction from the total oxygen consumption rate by performing an operation for calculating the respiration rate [Rr] of the sludge and further performing aeration and stirring after injecting ATU (N-allylthiourea) [ ATU
-Rr] value, and from the difference between [Rr] and [ATU-Rr], [Nit-Rr], which is the oxygen consumption rate associated with nitrification, was determined, and the activated sludge suspended matter concentration during water sampling and [ATU-Rr] And [Nit-Rr], the respiration rate per unit sludge amount is determined.

[0017]

According to the respiration rate meter with the washing 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. After measuring the activated sludge suspended solids concentration of this activated sludge, aeration is performed, the dissolved oxygen concentration is increased, and then the aeration is stopped and agitation is performed. Since it decreases, this is measured by a DO meter, and the respiration rate of the activated sludge is calculated by the least square method from the DO reduction rate.

Thereafter, the inner wall surface of the measuring tank is washed by injecting a washing liquid and tap water, and the measuring tank is filled with tap water, so that the measuring tank is always filled with tap water during a time when measurement is not being performed. Therefore, the inner wall surface of the measuring tank is not in contact with activated sludge or other contaminants, so that a decrease in measurement accuracy due to the contaminants is prevented.

The respiration rate is calculated by injecting the ATU (N-allylthiourea) reagent from the ATU liquid injection tube and performing aeration by injecting air again to measure the decrease in DO concentration due to oxygen consumption by activated sludge. While repeatedly performing the step of performing, the [ATU-Rr] value, which is a value obtained by subtracting the oxygen consumption rate accompanying the nitrification reaction from the total oxygen consumption rate at the same time, is calculated, and the difference between [Rr] and [ATU-Rr] is calculated. [Nit-Rr], which is the rate of oxygen consumption due to nitrification, is determined, and the respiration rate per unit sludge amount is determined from the activated sludge suspended matter concentration at the time of water sampling and [ATU-Rr] and [Nit-Rr].

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view showing an embodiment of a respiration rate meter with a washing mechanism according to the present invention. FIG. 1 is a vertical sectional side view of the present embodiment, in which 13a is a water sampling port, 13b.
Is a drain port, and 14 is a measuring tank. Tubes 15 and 16 forming a water passage are connected to the inlet and outlet sides of the measuring tank 14.

V ₁ is an upper pinch valve, V ₂ is a lower pinch valve, 17, 18 and 19 are air inlets, and tubes 15 and 16 are in a pinched state by injecting and exhausting air from air inlets 17 and 19. Then, the opening and closing operation of the activated sludge liquid is performed. Reference numeral 20 denotes a DO electrode as a dissolved oxygen concentration detection unit, and 21 denotes a stirrer.

Reference numeral 22 denotes an ATU liquid injection pipe, 23 denotes a tap water injection pipe, 24 denotes a cleaning liquid injection pipe, and the ATU liquid injection pipe 22 is connected to an ATU adding device (not shown). The third pinch valve V ₃ and the air inlet 25 is disposed between each injection tube 22, 23, 24 and the upper pinch valve V _1. Thus the ATU solution injection tube 22, the tap water injection pipe 23 and the washing liquid filling tube 24 is connected to the measuring vessel 14 by interposing a third pinch valve V _3.

The operation method for measuring the respiration rate of the activated sludge according to this embodiment is as follows. First, as a basic operation, air is introduced from the air inlet 18 into the measurement tank 14 to form an air lift, and the upper pinch valve V ₁ and the lower pinch valve V ₂ are opened to open the water sampling port 1 as in the conventional example.
The activated sludge liquid in the aerobic tank (not shown) is introduced into the measuring tank 14 from 3a.

After a certain period of time, the lower pinch valve V ₂ is closed by injecting air from the air inlet 17, and the MLSS (activated sludge suspended matter concentration) of the activated sludge is measured by a separately provided MLSS meter.

Next, air is sent from the air inlet 18 into the measuring tank 14 to aerate the collected activated sludge to increase the DO concentration to a set value, for example, 5 (mg / l).

When the DO concentration rises to the set value, the aeration is stopped, and the upper pinch valve V ₁ is closed by injecting air from the air inlet 19 to start stirring by the stirrer 21. Then, the DO concentration decreases with the oxygen consumption of the activated sludge by the aerobic microorganisms. The DO concentration is measured by the DO electrode 20 and a DO meter (not shown), and the [Rr] of the activated sludge is calculated from the DO decreasing rate by the least square method. Is calculated.

Next, the upper pinch valve V ₁ and the third pinch valve V ₃ are opened, and the ATU (N
(Allylthiourea) reagent is injected into the measuring tank 14. Then, aeration with air from the air inlet 18 is performed again, and D
Aeration from increasing the O concentration to a set value is stopped, a decrease in DO concentration due to oxygen consumption by activated sludge performs agitation by stirrer 21 closes the upper pinch valve V ₁ of the unshown D
The value of [ATU-Rr] is obtained by calculation at the same time as [Rr] while repeatedly performing the step of measuring [Rr] from the DO reduction rate by measuring with an O meter.

Then, the obtained [Rr] value and [ATU-R
[Nit-Rr] was determined from the difference between the [ML] r] values, the MLSS concentration determined at the time of water sampling, and [ATU-Rr] and [Nit-R]
r], the respiration rate per unit sludge amount [Kr], [AT
U-Kr] and [Nit-Kr].

To explain this further, the measured [AT
The U-Rr] value is generally used to monitor the progress of the nitrification reaction in an aerobic tank. That is, the oxygen utilization rate (Rr) includes the amount of oxygen consumed in the oxidative decomposition of organic matter, the amount of oxygen consumed in the endogenous respiration of activated sludge, and the amount of oxygen consumed in the nitrification reaction. This value is expressed as a value obtained by subtracting the oxygen consumption rate associated with the nitrification reaction from the respiration rate due to the removal of organic substances and endogenous respiration, that is, the total oxygen consumption rate. Therefore, the progress of the nitrification reaction is determined by [Rr] and N-allylthiourea (chemical formula C ₄ H ₈ N ₂ S,
(ATU) and the difference in Rr measured [ATU-Rr]
Can be obtained from

If the above difference is [Nit-Rr], [Nit-Rr] = [Rr]-[ATU-Rr] (1) That is, the [Nit-Rr] value is an oxygen consumption rate accompanying nitrification, and if this value is small, the nitrification reaction ends,
If it is larger, it can be determined that the nitrification reaction has not been completed. Since [Nit-Rr] represents the oxygen consumption based on the nitrification reaction, the nitrification rate in the aerobic tank can be estimated from this value.

Normally, a sample of water sampled from an aerobic tank [AT
The oxygen consumption rate [Nit-Rr] value for the nitrification reaction is measured based on the [U-Rr] value.
It is determined whether the nitrification reaction has been completed based on the value. That is, when the nitrification reaction proceeds smoothly and the concentration of ammoniacal nitrogen decreases, the [Nit-Rr] value also sharply decreases, indicating that the nitrification reaction in the aerobic tank has been completed.

On the other hand, when the measured oxygen consumption rate [Nit-rr] is large, the [ATU-Rr] value indicates that the nitrification reaction in the aerobic tank has not been completed. Is determined. At this time, the drive of the stirring mechanism of the anaerobic tank is stopped, and the amount of air blown to the aerobic tank is controlled, so that aeration is performed to reach an ideal nitrification rate.

Thus, the respiration rate [Rr] and [AT
After measuring the [U-Rr] value, the washing step is performed. In this case, first, the lower pinch valve V ₂ and the upper pinch valve V ₁
Introducing tap water from the tap water injection pipe 23 from the opening, the measuring vessel 14 by closing the lower pinch valve V ₂ after discharging the sewage in the measuring tank 14 to the aeration tank, not shown replaced by tap water .

[0034] Then the cleaning liquid such as sodium next chlorate introduced into the measurement chamber 14 through the cleaning solution injection tube 24, to open the lower pinch valve V ₂ after the lapse a certain time, measuring tank 14
Fill with tap water until there is no cleaning solution inside. When the draining of the washing water is finished by closing the lower pinch valve V ₂ ends the washing process.

After the completion of the cleaning step, the lower pinch valve V ₂ is opened again to send air from the air inlet 18 into the measuring tank 14 for a predetermined time. Then since the measuring chamber 14 is filled with only air, wherein feeding the tap water from the third pinch valve V ₃ tap water injection pipe 23 through closing the lower pinch valve V ₂ in the measuring chamber 14, the condition While preparing for the next measurement.

As described above, the inside of the measuring tank 14 during the non-measurement time period is always filled with the tap water sent from the tap water injection pipe 23, and therefore the inner wall surface of the measuring tank 14 is activated sludge or the like. Thus, an operation mode in which no contaminant adheres to the DO electrode 20 without contact with the contaminant is obtained.

[0037]

As described above in detail, according to the respiratory rate meter with a washing mechanism according to the present invention, an air lift is formed in the measuring tank to introduce the activated sludge into the measuring tank, and the activated sludge floats. The aeration is performed after measuring the concentration of dissolved matter, the aeration is stopped after increasing the dissolved oxygen concentration, and the stirring is performed. The dissolved oxygen concentration reduced with the oxygen consumption of the activated sludge by the aerobic microorganisms is measured to reduce the DO. After calculating the respiration rate of activated sludge from the velocity by the least squares method, cleaning the inner wall of the measuring tank by injecting the washing liquid and tap water, and then filling the measuring tank with tap water, during which time is not measured Is always filled with tap water, and therefore the inner wall surface of the measurement tank is not in contact with activated sludge or other contaminants, thereby preventing a decrease in measurement accuracy due to the contaminants.

In particular, the respiration rate of the aerobic microorganisms in the activated sludge adhering to the measuring tank does not become an error factor, and contaminants adhere to the detector such as the DO electrode or an accessory such as a stirrer. As a result, frequent sterilization and cleaning operations as in the related art are unnecessary, so that maintenance can be simplified and adverse effects on the process due to excessive chemicals can be eliminated.

Based on the obtained respiration rate of the activated sludge, it is necessary to establish an efficient operation control method for sufficiently increasing 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 for the circulation type nitrification denitrification method but also for monitoring for promoting the denitrification reaction in the standard activated sludge method.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a respiratory rate meter with a washing mechanism according to the present embodiment.

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

FIG. 3 is a vertical sectional side view showing an example of a conventional respirometer.

[Explanation of symbols]

13a ... adopted Mizuguchi 13b ... drain outlet 14 ... measuring tank 15, 16 ... tube V ₁ ... upper pinch valve V ₂ ... lower pinch valves 17,18,19,25 ... Air inlet 20 ... DO electrodes 21 agitator 22 ... ATU liquid injection pipe 23 ... tap water injection pipe 24 ... cleaning liquid injection pipe V ₃ ... third pinch valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 33/18 G01N 27/416

Claims (2)

(57) [Claims] 1. An activated sludge liquid is introduced into a measuring tank by an opening / closing operation and an air lifting action of an upper pinch valve and a lower pinch valve attached to the measuring tank, and the activated sludge is aerated and the dissolved oxygen concentration is measured. An apparatus for measuring a respiration rate of an activated sludge liquid by an operation, wherein an ATU liquid injection pipe, a tap water injection pipe, and a cleaning liquid injection pipe are connected to the measurement tank via a third pinch valve, whereby the activated sludge liquid is measured. After measuring the respiration rate, the inner wall of the measuring tank was washed by injecting the washing liquid and tap water, and then the measuring tank was kept filled with tap water to prepare for the next measurement. A respiratory rate meter with a washing mechanism. 2. The respiration rate is measured by measuring a decrease in dissolved oxygen concentration due to consumption of oxygen by aerobic microorganisms caused by agitation of activated sludge and injection of air. The respiration rate of activated sludge [R
[ATU-Rr] value, which is a value obtained by subtracting the oxygen consumption rate accompanying the nitrification reaction from the total oxygen consumption rate by performing aeration and stirring after injecting ATU (N-allylthiourea) and further injecting ATU (N-allylthiourea). [Rr] and [ATU-R
r], which is the rate of oxygen consumption due to nitrification [Nit−
Rr], the activated sludge suspended matter concentration at the time of water sampling and [ATU
The respiratory rate meter with a washing mechanism according to claim 1, wherein a respiratory rate per unit sludge amount is obtained from [-Rr] and [Nit-Rr].