JPS6064698A - Controlling apparatus of activated sludge process - Google Patents

Abstract

PURPOSE:To keep desired quality of treated water stable over a long period of time, by providing a converter for converting the output of a redox electrometer to a nitration rate and a deviation detecting circuit for imparting the deviation value of the output of said converter and a preset value to a control part. CONSTITUTION:When an aeration tank 1 is a perfectly mixing type, a redox electrometer (OP meter) 31 avoids the vicinity of an introducing port for inflow water or return sludge and is arranged to a uniformly mixtured place. When the tank 1 is a forcible flow type, the OP meter 31 is arranged in the vicinity of an outflow port. The output of the OP meter 31 is inputted to a nitration rate converter 32 to obtain a nitration rate in output. This nitration rate is inputted to a deviation detecting circuit 33 and the deviation output with a set nitration rate is sent out from the circuit 33. A deviation output value is inputted to a DO control part 5 and the output of the nitration rate converter 32 is inputted to a SRT control part 8 while the set values of both control parts are altered by the aforementioned deviation output value and the nitration rate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an activated sludge process control device for biologically treating wastewater.

A conventional example of this type of control device will be described with reference to FIG.

Figure 1 shows the dissolved oxygen control method (hereinafter referred to as the DO control method)
This system adopts a sludge retention time control method (hereinafter referred to as the s + t 'r control method). In the figure, 1 is an aeration tank into which inflow water such as wastewater is introduced, and near the outlet of this tank 1 there is dissolved A modified wood meter (Do meter) 2 and a mixed suspended matter concentration meter (MLSSI) 6 are arranged, and a vibrator 1a to which oxygen is supplied from a blower to be described later is arranged at the bottom of the tank. The outflow water from the aeration tank 1 is introduced into the Saisha sedimentation tank 4. The output of the DO meter 2 is input to the DOi14 meter 5a in the Do control section 5.

The output of the DO controller 5a is given to the JR Sardine controller 5b. In this landscape controller 5b, the degree of opening and closing of a valve 5C inserted in the oxygen supply passage 6 is controlled by the output value of the Do controller 5a. In addition, 5d is a proa and 5e is a flowmeter. A sludge interface meter (SL meter) 7 (or sludge concentration distribution meter (SCD meter)) is disposed within the final settling tank 4. The output of this sludge interface meter 7 and the output of the mixed suspended matter concentration meter 3 are 5
) It is manually operated by the controller 8a of the tT control section 8. The output of a return sludge concentration meter (Ca meter) 9 is also input to the controller 8a. cz19 is provided in the return sludge path 10.

The return sludge path 10 is connected at one end to the final settling tank 4, has a return sludge pump 8b in the middle, and is connected at the other end to an aeration tank IK. 8C is a surplus sludge pump, and this pump 8C is for drawing out the sludge in the sedimentation tank 4 as surplus sludge. The return sludge pump 8b and excess sludge pump 8C are controlled by a controller 8a.

When wastewater, etc. is treated using the control device configured as described above, the quality of treated water is stabilized and the amount of power consumed is reduced compared to when O control q S RT control is not performed. Colander. However, the microbial activity of activated sludge, which plays the main role in purification, changes depending on factors such as water temperature, PL, inflowing sludge, and toxic substances. When operating, the quality of treated water,
Falling in love in a state of sludge! A: It may exhibit an aeration condition.

For example, it is known that when the water temperature increases by 10°C, the biochemical reactions of activated sludge microorganisms double. Therefore, if the operation continues with the same DO1SRT value, the reaction within the aeration tank 1 will proceed too much. Especially when using a forced flow type aeration tank, the air
Substrate decomposition ends near the middle of the 7-year tank, and from then on until the outlet, sludge decreases due to self-oxidation and power is wasted due to excessive aeration. FIG. 2 shows an explanation of the substrate concentration distribution state in the aeration tank as described above. In Figure 2, the inlet is the side where the inflow water of the aeration tank is introduced, and the outlet is the outflow water side.
The curve ('1+I IJ)''C is the reaction curve when the water temperature increases by 1θ°C as described above, and the excessive aeration area is the case when the water temperature increases by 10°C.

Note that the 'r°C curve is for ideal control.

As mentioned above, conventionally, problems occur in the biochemical reaction process in the aeration tank when the water temperature rises by 10℃. was not possible and +30
This is because the relationship between water quality factors such as DrW conversion and nitrification and the DO1SRT control set value was not clear.

This invention was made in view of the above circumstances, and employs the nitrification rate as the finger gland of the biochemical reaction in the aeration tank, and 1) 0 system to 1, -S It 'l' control valley. Modify the specified value chronologically so that it becomes the target nitrification rate -1
The purpose is to provide an activated sludge process IFI control system 1 that is designed to

Hereinafter, an embodiment of the present invention will be described with reference to the drawings, and the same parts as in FIG. 1 will be described with the same reference numerals.

In FIG. 3, an oxidation-reduction potential needle (ORP needle) 61 is provided at a predetermined location within the aeration tank 1. This O
If the aeration tank 1 is of a complete mixing type, the RP meter 61 is placed in the vicinity of the inlet of inflow water, returned sludge, etc., where it is uniformly mixed. Furthermore, if the tank 1 is of a forced flow type, it is placed near the outlet. Said OR
The output of the P meter 61 is input to a nitrification rate converter 62, and the nitrification rate is obtained as an output. This nitrification rate is input to a deviation detection circuit 66, and the deviation output from the set nitrification rate is also sent to this circuit 66. 1'(
The i difference output value is input to the Do control section 5.

In addition, the sit'r control unit 8 is connected to the nitrification rate converter 6.
The output of No. 2 is manually input, and the set value of Illm is changed according to the deviation output value and the nitrification rate.

Fig. 4 is a system configuration diagram showing the longitudinal path configuration of the sandwich portion of the embodiment shown in Fig. 3. To describe the operation of Fig. 3 using Fig. Nitrification rate calculation output ■ is optimal 1) 0, U (supplied to the setting value determining unit 40 where the SRT setting value is determined. This determining unit 40
The DO set value (DOsgt) determined in is given to the DO control unit 5, and the SRT set value ('S RT SET
) (RI is given to S R'l' it control group 8.1) 0 control++1 part 5 controls once of square 5C by D OSET determined by mononitrifier 1i11 L
.

to control the amount of air blown to the aeration tank 1. Note that the DOi+i11?1141 section 5 is supplied with the DO by the DOO20, the quality measurement and the air flow rate measurement 11σ■ from the treatment process group 41. Measured values f of this treatment process, μ41, MLSS by the MLS total 6, return sludge openness by the CR total 9, sludge #degree by the SL total 7, etc. are supplied to the 5ILT control unit 8. SRT control unit 8
116 from the S R' SET and the treatment process unit 41 give the value g of the amount of surplus sludge, surplus sludge pump 8C0) start-up, stop, etc. to the treatment process unit 41.

FIG. 5 is a flowchart for describing the above-mentioned operation in more detail. In FIG. 5, first, OIt P measurement l1lJ and reading are performed (indicated by ORP).

Thereafter, ottp is converted into a nitrification rate (ρM), and the deviation (Δρ) between the set nitrification rate (ρS) and ρ is calculated. Then Δ
1) Obtain the 0 set value (D OS ) from ρ. In the diagram, 0R
PC is sampling type o it p, J! A four-section meter is shown. After the upper and lower limits of Dos are checked using the maximum value [)OX and the minimum value DON, I) the Os value is changed. The Dos value is within the Do setting range D ON (Dos (1
') Qx 17) liil LC, I) when I)
O measurement value is read (1) Or, ().

If the range is exceeded, the process moves to the process described later.

The deviation (Δ1)0) from the Dos value is taken from the DOM, and the air blower setting (Gs) is set. The upper and lower limits 11η of this (is) are checked using the maximum value Gsx and the minimum value GSN. After checking, the air blowing amount is set to i. After that, the air blowing amount is read (Gsv). This 08 M is the deviation from the set value. (ΔGs) is taken, and the valve opening degree (M V) of the wind cover controller (G s C) is controlled by this ΔGs.

Processing that deviates from the DO setting range is 1) O3 = I) ON
Or 1 in DOs=DOx comparison section. b tif,
D Calculate the cumulative time (ts) for deviation from the upper and lower limits. In addition, 1
)r is the DO upper/lower limit deviation elapsed time. When this ts exceeds the set time (Ts), sl 1, 11
1 group, the operation moves to correcting the SILT setting f+&. The change range ΔSRT is determined by the deviation (Δψ) P[Equation 11, etc. The determined S l't T setting value (S
After the upper and lower limits of i'LTs) are checked using the maximum value 5RTx and the minimum value 5rtTN, S RT s is set and the 5FLT8 is supplied to the SRT control unit 8.

As mentioned above, 1) 0 and SRT control is performed, but the change period of the Do setting value is usually about 30 to 60 minutes, while the change period of the 5 IFT setting value is the same as the current Slt'r setting value. It's the same or more. Thinking about this, IJ
ill (The m1 part may be controlled only by <Do based on the nitrification rate deviation, and the S RT setting value may be manually corrected. In this case, the configuration of Fig. 4 is changed to the one shown in Fig. 6. Saiyo will be 5 years old.

Next, the reason why the nitrification rate by JItPil was used as a control index as described above is as follows.

(Al In a normal urban sewage treatment plant) iε people!
4 quality B 01. ):Nitrogen:N:L@P ratio is said to be a proper ratio of 100:5:1, but N and P are excessive, resulting in a tail. Konotame, Law of the Minimum (Liel)
ig, 1843), BOD components are removed to near the limit of biological treatment. However, N and P
is not removed and flows out with the treated water. Of these, N is mainly stored in the aeration tank.
7. Change 1-ro as shown in Figures 7 and 8. 71st Bi1
is a schematic explanation of nitrification and denitrification, and in the figure, 71 is the d element and 72 is the inorganic phoneme. Protein-g71a is divided into amino acids 71b by proteolytic bacteria 76. 1jfl ; Self! Indecency room, room 72 is NH472a, N0272b, N0a
Consisting of 72 c.

75 is Nitrosomonas,
76 is Nitrobacter (N1trobacter),
77 is nitrogen gas.

Figure 8 is a schematic explanatory diagram of the distribution characteristics of the oxidation and nitrification processes in the aeration tank of the live pouring sludge method. show,
The hatched area represents ammonia, and the vertical line area represents BOD. The left side of the figure is the aeration tank inlet, and the right side of the figure is the aeration tank outlet.

712;1 and as shown in FIG. 8, nitrogen N ha'j 8 rel. -N 1c, NH4-N Kara N
The reaction to O2-N and N0T-N is called nitrification, and the conversion rate is indicated in red as nitrification ASρ, which is defined by the following equation.

Generally, due to excessive N content, ρ at the aeration tank outlet (or treated water) is 10 to 100%. For this reason, components 1301) that have been sufficiently removed are often treated as treated water without being nitrified. Further, since No''-N is detected as COD, it appears that the C01) component is not removed much.

(B) The nitrification rate ρ is the most −11 in the activated sludge process.
(Send with a chivalrous operation/!I!LhL and Sosashi Sludge++t
It is closely related to "S it i".

Figure 9 A-D shows VO installation short leg 11α
Figure 9A shows D L) '+irl side 1 set value is set to 1,3.5(I)l/l).
This figure shows the changes over time in each water quality index when
As shown in FIG. 13, there is almost no change in the OI component.

On the other hand, the nitrification rate ρ is 25 to 7 as shown in Figure 9.
5 (%) and human lid,!. Furthermore, the correspondence and reproducibility of the nitrification rate ρ to changes in the DO set value are also extremely poor. Diagram C
represents the relationship between NH, q -N, NOa -N and N. "f~('l 1s41.

Figure 10 is a characteristic diagram showing the relationship between 811 'I' and nitrification rate. This indicates that it is a rate-limiting factor in the reaction.

From these facts, as a method to increase the nitrification rate ρ to 1iIlIIIIII, for short-term aill 4dll, 1) Correcting the 0 setting value (or changing the air flow rate), and for long-term SR
, T setting values are effective.

(The q nitrification reaction is +, compared to the BOD 14i reaction.
The oxygen requirement for IQ - 1 - 1 is 3 to 4 times greater.

For the 111i<1, the nitrification rate ρ is 30? Figures 1 and 2 show the changes over time in the amount of air required when controlled at 70 z and 70 z, respectively.

As is clear from FIG. 11, operating at a nitrification rate higher than necessary is not preferable from the standpoint of energy conservation.

(D) When the nitrification rate is extremely low (for example, 10% or less)
It is known that the BOD removal rate also decreases. On the other hand, in extreme cases (for example, 90% or more), the denitrification phenomenon shown in FIG. 7 occurs in the final settling tank, and activated sludge tends to float to the surface.

(12) The nitrification reaction is shown in Figure 7.
This is a German oxidation derivative reaction. Therefore, the nitrification rate ρ, which is the conversion ratio, is in a tangential relationship with OR,P. FIG. 12 is a characteristic diagram showing this relationship. This figure 8 shows the actual processing/A
It is a characteristic diagram showing the relationship between ORP and nitrification rate measured in the aeration tank of ie. As is clear from this characteristic diagram, the relationship between OIt P and nitrification rate is
It changes almost linearly up to 80%.

However, the straight line range and slope may vary depending on the treatment facility. Therefore, it is possible to calculate the nitrification rate ρ shown in the previous 6-dimensional formula if the nitrogen N of each texture can be measured continuously, but for this purpose at least 3 detection sensor is required. However, from the viewpoint of measurement, it is not preferable to use three sensors. Here, if the 01 (P meter) is used, there is an advantage that ρ can be measured with one detection sensor, which is extremely advantageous in terms of maintenance.

For the five reasons mentioned above, the nitrification rate measured by an ORP meter is used in this light.

Finally, No. 131 AF shows oral changes in various indicators when S 11 T was changed stepwise from day 5 to day 10 according to the example shown in FIG. Figure 13A is an inflow water characteristic diagram, Figure 13 is a 5kLT setting value characteristic diagram, Figure 13C is an oral change characteristic diagram of M L S S 4 degrees, and the 13th diagram is an oral change characteristic diagram of DO(, 5J degrees). The custom-made diagram, FIG. 13E, is a characteristic diagram of oral change in air flow rate, and No. 131AF is a characteristic diagram of oral change in nitrification rate.

Each of the above characteristic diagrams assumes that S It 'I' is a disturbance factor, and (a) constant air dish operation (Gs = 6000+f/br
), (b) D 0 constant control (DOs value == 2.5
IL)/l, (C) Constant nitrification rate control (ρ8-50%)
This figure shows the daily changes in hil, SS concentration, Do concentration, air flow rate, and nitrification rate in each case.

From the above results, since SRT has doubled, Ml, S
SS variation increases, (a) Under constant airflow operation, endogenous respiration increases, l) 0 concentration gradually decreases, (b) D 0
5jA 1irll It can be seen that nitrification is gradually increasing in the groaning. This means that in constant air flow operation, the reaction rate decreases more strongly due to the decrease in DO value than the increase in reaction rate due to increase in sludge, so the nitrification rate gradually decreases.
．． -(: <.On the other hand, in the constant nitrification rate 1tlJ control, the 1) 0 value is lowered by the increase in the removal rate due to the increase in sludge, so the nitrification rate remains the same as before the change. It is maintained within the range of 50±5%. As mentioned above,
However, with the constant air flow operation and I) 0-f control that had been implemented, it was not possible to maintain the treated water quality, especially the nitrogen component, constant due to disturbance (here, 5ILT). However, by feeding back the nitrification rate and correcting it over time to the appropriate 1) 0 to 7 c, the above has become possible.

As described above, according to the present invention, the nitrification rate is adopted as a water quality index for grasping the anti-16 process, and in order to maintain it constant, 1) the 0 set value and the 81 jr set value are set to appropriate values. Since it is made to stand still in chronological order, the following effects occur.

(1) Since the nitrification reaction process itself is used as an indicator, it is important to maintain the desired treated water quality stably for a long period of time.

(2) In addition to the conventional method of maintaining the environmental factors of the treatment process (1) (J value F/M ratio constant), it is also possible to adequately respond to changes in other factors such as water temperature and inflow load. ,
The desired quality of treated water can be maintained.

(3) The amount of oxygen consumed in the nitrification reaction is 3 to 4 times higher than that in the BOD removal reaction per substrate removed at the -C114i position. This has the advantage that monitoring and controlling the nitrification reaction (174) can save the power of the blower IB.

(4) Nitrification is closely related to bulking, and is good l.
[To maintain the treatment status ((ORP monitoring of nitrification)
If the bottle 1 is used, maintenance and inspection will be easy.

(5) Since the nitrification reaction is a one-bleed arrangement reduction reaction, the same effect as described above can be obtained by using the Ort p meter as one indicator of nitrification.

[Brief explanation of the drawings] Fig. 1 is an explanatory diagram of the configuration of a conventional activated sludge process control device, Fig. 2 is a characteristic diagram of the substrate concentration distribution in the air tank, and Fig. 3 is an example of the h11I embodiment of the present invention. 4 is a system configuration diagram of the main part of the present invention, FIG. 5 is a flowchart for explaining the operation of FIG. 3, and FIG. 6 is only the DO control of the system configuration in FIG. 4. Figure 7 is a schematic explanatory diagram of nitrification and denitrification, Figure 8 is a distribution characteristic diagram of 801) d oxidation and nitrification processes in a standard activated sludge method aeration tank, Figure 9 A to 1) are 1) ]0 setting++
Figure 10 is a characteristic diagram showing the relationship between sit'r and nitrification rate, Figure 11 is a characteristic diagram of nitrification 4 setting value and air flow rate, and Figure 12 is a characteristic diagram showing the relationship between sit'r and nitrification rate.
Characteristics related to ap and nitrification rate IX+, ・Hemp 13
Figures A to 1- are characteristic diagrams showing changes over time in each individual finger collar when SRT was changed stepwise from 5 days to 10 days. 1...Aeration tank, 4...Final sedimentation tank,
5... DOi+III control section, 8... Sl'tT control section, 31... ORP meter, 62... Nitrification rate converter, 3
3... Deviation detection circuit. Fig. 6 Fig. 71 8th BOD Wandering Cotton 4-Sui 1 Ihi J Entrance Airley Gin Shinonk Sho, Mouth i Fig. 3 MLSS; tJl==IE & 4L-day Fig. 13

Claims (1)

[Claims] (1) It has a dissolved oxygen control unit that detects dissolved oxygen in the aeration tank into which wastewater is introduced and controls the dissolved oxygen in the tank, and also controls the detected value of the mixed suspended matter concentration in the tank and the final settling tank. In a biochemical reaction process control device having a sludge retention time control unit that controls a sludge concentration distribution value and a return sludge concentration value returned from a final settling tank to an aeration tank, a converter that converts the output of this electrometer into a nitrification rate, and a deviation detection circuit that obtains the deviation between the output of this converter and a preset value and provides this deviation value to the control section. An activated sludge process control device comprising: