JPS5814836B2 - Device for measuring dynamic properties of activated sludge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is suitable for the desired purpose in fields such as sanitary engineering and fermentation engineering that use microorganisms under aerobic conditions, such as sewage treatment systems using activated sludge methods. This invention relates to a device for measuring dynamic properties of activated sludge for operational management.

Here, a case of a sewage treatment system using the activated sludge method will be explained as an example.

Figure 1 shows the flowchart. First, sedimentation tank 1
At pump P, suspended solids with relatively good settling properties are collected together with sewage.
1, the sewage is discharged to the concentration tank, and the remaining sewage is introduced into the next aeration tank 2.

Here, microorganisms present in the activated sludge take in organic pollutants (hereinafter referred to as substrates) contained in the sewage.

That is, a part of it is used to synthesize new cells, thereby multiplying themselves, and the rest is consumed as energy for their life support.

When carrying out these metabolic activities, they use the oxygen dissolved in the water.

For this reason, air is blown into the aeration tank 2 by an air pressure feeder B or a blower device 3 so that the necessary oxygen is always present in the water.

Thereafter, activated sludge and water are separated in the final settling tank 4, and the supernatant water is sterilized with chlorine and released as treated water.

On the other hand, the settled activated sludge is returned to the aeration tank 2 as return sludge by pump P2, but at this time, a part of the return sludge is first drawn out to settling tank 1 by pump P3 as surplus sludge, and remains in the system. The amount of sludge produced is kept at an appropriate level.

Appropriate operational management in such a treatment system using activated sludge means always ensuring conditions for activated sludge to efficiently remove substrates.

There are two conditions for this. One of these is to maintain the dissolved oxygen concentration in the aeration tank at an appropriate value and allow the metabolic activities of microorganisms to proceed smoothly. /M ratio) is maintained at an appropriate value.
The objective is to maximize the amount of substrate removed per operation in the system and obtain a large amount of high-quality treated water in a shorter time.

Here, the former has already been put into practical use, so
The problem lies in the latter.

Excess sludge control is generally said to be effective for appropriate and constant control of the F/M ratio.

That is, the activated sludge performs the growth effect as described above.

Therefore, in order to maintain an appropriate F/M ratio, it is necessary to extract an appropriate amount of excess sludge from the total amount of sludge present in the system.

Therefore, if the amount of inflowing substrate (or inflowing load) and the dynamic properties (activity, etc.) of activated sludge are constant, the rate of sludge growth is constant, so the amount of sludge existing in the system By removing excess sludge at a constant rate, an appropriate F/M ratio can be maintained.

However, if there are fluctuations in the inflow load, the conventional appropriate F/
In order to maintain the M ratio, the amount of excess sludge must be changed accordingly.

In addition, even if the inflow load remains unchanged, if the dynamic properties of activated sludge change, the appropriate F/M ratio specific to that activated sludge should also change, so by appropriately drawing out the sludge accordingly, It is necessary to maintain a suitable F/M ratio.

That is, it is necessary to detect inflow load fluctuations or changes in the dynamic properties of activated sludge by some method, and to control excess sludge according to the detection results.

However, until now, the detection and measurement technology of these parameters or the automatic control method of activated sludge based on the variation of each parameter has not yet reached the stage of practical use, and even if it exists, it is difficult to test the quality of treated water (for example, transparency). Therefore, it is not possible to quickly and accurately reflect the effects of sudden changes in the process on the control factors.

In view of the above points, the present invention provides a measuring device that can accurately (quantitatively) measure the dynamic properties of activated sludge, which should be used as control or management indicators in the live pouring sludge method, etc. be.

FIGS. 2 and 3 are a block diagram and a sectional view of essential parts, respectively, showing an embodiment of the present invention.

In FIG. 2, reference numeral 5 denotes a general oxygen consumption meter (hereinafter referred to as a γ meter) that is immersed in an activated sludge reaction tank 6 such as the aeration tank 2, for example, as shown in FIG. It has a structure equipped with a detection mechanism, an aeration mechanism, a cleaning mechanism, and an injection stirring mechanism.

Reference numeral 7 denotes a drive section connected to a predetermined air piping group 8 and injection pipe 32 of this gamma meter 5, and this drive section 7 receives instructions from the calculation control section 9 to drive each part of the r total 5, which will be described later. Drive control according to the sequence.

On the other hand, the signal line 24 of the detector 21 of the γ meter γ is connected to the calculation control section 9.

The arithmetic and control unit 9 determines the dynamic properties of the activated sludge from the results measured by the detector 21, that is, the changes over time in the dissolved oxygen concentration (DO value) in the sample water.

The results are sent to the desired indicator recorder 10.

Next, a specific measurement sequence of the gamma meter 5 will be explained with reference to FIG.

The measurement sequence is performed as shown in Figure 4.
First, open the lower air valve 15 and sample water (
(for example, sewage, etc.).

When the test chamber 17 is filled with a predetermined amount of test water, the lower air valve 15 is closed.

At this time, the upper air valve 18 is open and the test water is exposed to the outside air via the drain pipe 19.

In this state, air is then injected into the sample water through the bubble generation hole 20 to aerate the sample.

At that time, the dissolved oxygen concentration in the sample water is measured with the detector 21,
When it detects a predetermined value, the air is stopped and the upper air valve 18 is closed at the same time.

While keeping the sample water sealed in this way, turn on the air motor 2.
Measurement is performed while rotating the magnetic stirrer 23 by driving the magnetic stirrer 23.

If you are measuring general oxygen consumption, please use the water sampling section 16 after measurement.
The measurement is completed by opening the valve and draining the water, but this is different now.After the measurement, the upper air valve 18 is opened again and the measurement is carried out in the same way as before, and this is repeated many times.

The above sequence is automatically performed by the calculation control section 9 and the drive section 7, and the respiration rate of the activated sludge at each time detected by the detection section 21 (more precisely, the dissolved oxygen concentration in the sample water changes over time). change) is sent to the arithmetic and control unit 9, and the dynamic properties of the activated sludge are calculated.

In the figure, 25 to 28, 30, 31, and 33 are air pipes, 32 is an injection pipe, and 29 and 34 are rubber pipes.

Next, we will explain the reason why the dynamic properties are determined from the temporal characteristics of the respiration rate of activated sludge, which is the measurement result, and the calculation process.

Here, the endogenous respiration rate constant b and the autooxidation rate kd, which are important factors among the dynamic properties of activated sludge, are determined.

Both are indicators that express the activity of activated sludge, but the former indicates the ratio of active and inactive substances in activated sludge, and the latter indicates the rate of death due to self-oxidation of activated sludge and the activation state of activated sludge. They differ in that they represent the speed of transition to an inactive state.

By the way, in general, the growth of activated sludge in a reaction tank is expressed by the following equation.

ΔM △S −=Y・−ka−M (1) △T
△T However, △M/△T is the amount of sludge growth, M is the amount of sludge existing in the system, △S/△T is the amount of substrate removed, Y is the yield coefficient, kd
is the autooxidation rate.

Further, the required amount of oxygen consumption in the biological oxidation system is defined as the following equation.

,,, △S r-r+r:a・10b-M (2)△T However, r is the total oxygen consumption, r' is the oxygen consumption due to substrate removal, and r'' is the oxygen due to endogenous respiration. consumption, a is the oxygen consumption rate constant per unit substrate removal, and b is the endogenous respiration rate constant.

Now, considering the case where there is no substrate removal in equations (1) and (2), that is, (△S/△T) = 0, regarding sludge growth, △M/△T = -kdM (3) When this is integrated, M(t)=Moe-kdt (However, when 1=0, M=M0) (4).

It can be seen that the amount of activated sludge decreases due to self-oxidation due to endogenous respiration.

On the other hand, the amount of oxygen consumed at that time is r=r'=b·M (5).

Substituting equation (4) into equation (5) to determine the temporal characteristics of oxygen consumption of live fish sludge in the case of no substrate removal, the following is obtained: 7'' (t) = bM0e-kdt (6).

Therefore, if the aforementioned measurement method of repeating long-term measurements without adding substrate to sludge is used, the characteristics shown in equation (6) can be obtained, and the endogenous respiration rate constant b and autooxidation rate kd
Therefore, it is possible to obtain the following.

FIG. 5 is a graph plotting on a semi-logarithmic scale the changes over time in the sludge oxygen consumption r actually measured using the above-described repeating sequence.

From the above equation (6), the slope of the curve should be -kd, so the self-oxidation rate can be determined from this.

Also, as shown by the dotted line in the figure, the point extrapolated to t=0 is bMo
Therefore, this is a known quantity, M, which is the amount of sludge in the test water at t=0.

By dividing by, the endogenous respiration rate constant b is obtained.

Note that Mo may be replaced by the sludge concentration of the sample water, so it can be easily determined using a desired sludge concentration meter during measurement.

In addition, in the same figure, the reason why the oxygen consumption after the start of measurement is larger than bM, that is, the oxygen consumption due to endogenous respiration, is because the activated sludge in the sampled water was initially endogenous 1
This indicates that there was no respiration, and this phenomenon occurs when substrates have accumulated in activated sludge.

Therefore, in order to obtain results in a short time, sludge that contains as little substrate as possible, for example, sludge near the outlet of the aeration tank in FIG. 1, should be taken as a sample.

Furthermore, each of the figures in FIGS. 6a to 6b is an oxygen consumption meter that can be replaced with the meter 5 in FIG. 3, respectively.

In the figure, 4θa and 40b are an upper valve and a lower valve, respectively, 41 is a valve drive mechanism, 42 is a power pipe for the valve 7 drive mechanism, 43 is a bubble generation hole, 44 is an air pipe, 45 is a magnet motor, 4
6 is a power pipe for driving the mork, 47 is a stirrer, 48 is a detector, 49 is a signal line, 50 is a drain pipe, and 51 is an injection pipe.

The functions of each part are the same as in FIG.

In the r meter in Figure 4, all the valve mechanisms etc. are 1 due to the action of air pressure.
However, the measuring device of FIG. 6 differs in that it is electrically driven.

As explained above, according to the present invention, (1) a detection unit that measures changes in dissolved oxygen concentration in test water over time;
(2) An aeration section that intermittently aerates the sample water and raises it to a predetermined oxygen concentration each time; and (3) a detection section that performs predetermined calculations using the results from the detection section to determine the dynamics of activated sludge. Since it has a calculation unit that calculates the physical properties, it is possible to accurately grasp one dynamic property of activated sludge in a short time, and
Since the output from the calculation unit has a quantitative value, it can be displayed and recorded or directly used as human power in other control devices, and can be used as an appropriate operation management index in a wide range of fields such as sanitary engineering and fermentation engineering. It has various excellent effects such as:

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing a sewage treatment system using a general activated sludge method, Figs. 2 and 3 are block diagrams and sectional views of essential parts showing one embodiment of the present invention, and Figs. 4 and 5. The figure is a graph for explaining the embodiment, and FIGS. 6a and 6d are sectional views showing different examples of the measuring device forming a part thereof. 1...First sedimentation tank, 2...Aeration tank,
3... Air diffuser, 4... Final sedimentation tank,
5...Oxygen consumption correction (r meter), 6...
Reaction tank, 7... Drive unit, 8... Air piping, 9... Arithmetic control unit, 10... Indication recorder, 21... ...Detector, 24...Signal line, 32...Injection tube.

Claims (1)

[Claims] 1. A detection unit that measures the dissolved oxygen concentration in the test water collected from the activated sludge reaction tank over time, and an operation that stops aeration after the dissolved oxygen concentration in the test water reaches a predetermined value. Activated sludge power comprising: an aeration section that repeatedly performs aeration, and a calculation section that performs predetermined calculations using the measurement results from the detection section to determine the dynamic properties of the activated sludge contained in the sample water. Scientific property measuring device.