JPS6028889A - Controlling device for activated sludge amount - Google Patents

Abstract

PURPOSE:To enable to maintain mean residence time of sludge at fixed value by operating result of operation of a measuring device of sludge volume index, amt. of feed water, amt. of returned sludge, and amt. of excess sludge, etc., and drawing controlled amt. of excess sludge from the final settling basin. CONSTITUTION:A sludge settling curve is prepd. using a sludge volume meter (SV meter) 10a, and the volume of sludge STt after (t) min from the beginning of measurement and the volume of sludge V30 after 30min from the beginning of measurement are determined. Both values SVt and SV30 are inputted to an operating device 10b of sludge volume index (SVI). SVI is determined from the value of WLSS of a WLSS meter 6 inputted from the device 10b. The output of the SVI measuring device 10 is inputted to a device 12 for operating the amt. of returned sludge and SV1 is used for the control of the amt. of operated results. The value of (t) is 20-60min. Furthermore, sludge is supplied from an aeration tank by a pump 11 to the above described SV meter 10a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an activated sludge sewing control device used in a sewage treatment system.

Conventionally, a surplus sludge control method has been used in F water treatment systems. This control method is shown in FIG. 1, and this method has been conventionally generally implemented as sludge LJ order (SA) control. In the following, referring to the Fm1 diagram, this method is a method in which a certain percentage of the sludge amount (MA) in the aeration tank is extracted as surplus sludge (MW), and the settling characteristics of the sludge (sludge volume index SV) are It is known that good control results can be obtained if the total sludge in the treatment system is stable and is approximately equal to the amount of sludge in the aeration tank. In the figure, 2 is the final sedimentation tank, and 3 is the final sedimentation tank where the sludge is returned from the final sedimentation tank λ.
1 is a return sludge pump that returns excess sludge to the final settling tank. S is the sludge in the aeration tank (MA) and excess sludge extraction @ (M
W) and r), and this arithmetic and control device 5 includes a mixed suspended matter concentration meter (MLS Sil), <
MLSS value of return sludge concentration meter 7 sludge age value (s A
), the number of times the surplus sludge has been pulled out by the surplus sludge pump ♂, the aeration tank volume (m”) (VA), and the time of withdrawal (T) can be seen.

Note that MA and MW are each performed using the following formulas.

MA=MLSSXVA, MW-1/NXMA/SA The output of the arithmetic control device S is supplied to the surplus sludge pump, and its pump is controlled.

Using the control method configured as described above, if the sedimentation characteristics of °C sludge are stable and the total amount of sludge in the treatment system is equal to the amount of sludge in the aeration tank t1#χ, the control is performed as described above. Well done. However, when the settling characteristics (SVI) of sludge fluctuates, the sludge distribution state in the aeration tank (MA) and the final settling tank λ changes due to this fluctuation. It becomes impossible to represent the amount of sludge in the system (aeration/sludge amount in the tank + sludge N in the final settling tank) by the internal sludge claw (MA).

For example, as the SVI increases to the upper hole (generally speaking, if the svr is 200 or more, it is called bulking sludge), the sedimentation rate of the sludge in the final settling tank 2 decreases. In addition, the concentration of the settled sludge (consolidated concentration) also decreases, and the sludge interface becomes upper punch during quantitative return. As a result, the amount of accumulated sludge in the final settling tank λ increases, and the sludge in the aeration tank f! t, (MA) decreases. In such a case, the excess sludge drawing stitch (MW) decreases even before sv■ rises, so the sludge daily age (SA) becomes longer than the set value. As a result of the above, when the SVZ fluctuates, the SA control method cannot control the sludge age (SA) at a constant level. At night, return sludge only (or return sludge rate: return sludge amount /
SVI also changes when the inflow sewage concentration changes. Similar to Kamoai, the inside of the aeration tank l and the final settling tank λ
With the sh control method, it becomes impossible to keep the sludge age (sA) constant.

In the SA control method described above, there were cases where the average residence time of sludge could not be maintained at -2, and the reason for this is as follows. In other words, changes in the return sludge rate and sedimentation characteristics of activated sludge (Bv
The distribution of sludge in the sharing tank and the final settling tank changes due to changes in the sludge NCMA) in the aeration tank. t
This is because the SA control calculates (MW), so one average residence time cannot be maintained at the set value.

Therefore, the sludge fv (MA) in the aeration tank/
It is necessary to control the total amount of sludge in the treatment system, including the final sedimentation tank λ, rather than the amount of sludge in the final settling tank λ. For this, the final precipitation r1. Although it is necessary to calculate the sludge t in lx J, it is known that the behavior of sludge in the final settling tank λ is very rough, and the sludge N Exactly 9. To do this, use F5. It was not possible to perform the calculation using the conventional control device Ff, which requires a numerical value n1n that is ','jli.

This invention was made in view of my own circumstances, and it is possible to measure the sedimentation of activated sludge using the sludge customer index nr+1tjt device i'Y (sv engineering measuring device).
As a result of this calculation, the amount of inflow wood grain and return sludge is calculated, and the return sludge is prohibited.
28 V engineering measurement equipment bond results, MLSS value, inflow water J
ft, collected sludge and surplus sludge are pulled out from the final settling tank under control.

It is an object of the present invention to provide an activated sludge airflow control device that can control the average residence time of sludge at a constant level using a simple control device.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings (Example 1). Parts that are the same as those in FIG.

In Figure 2, IO is the sludge amount Jet:it (s v
Total) 10a and sludge customer index (SV engineering) performance equipment In
There is an SV construction measuring device consisting of +1. Said S V i
'ii/(j A is supplied with sludge from the construction tank/ by a pump/l, and the SVI computing unit Fi,
10b is supplied with the MLSEI value and the measured value of 7a from M TJ SS ii A.
The mechanical measurement head 10 is an SV meter/(described later in 7a (Fig. 3)).
sludge sedimentation curve, sludge volume ri after t minutes from the start of measurement
svt, sludge volume sv after 80 minutes! SVi is measured from 1, , and ML8S1N. This measurement result is the return sludge circuit 19. The wandering control device 12 is operated manually. This control device f
l/co has an inflow water flow membrane tit/,? Inflow of water 1・
Support and return sludge circuit/'71c installed 7Fi...
,;Hγυ mudflow ji'(11"3 pieces of returned sludge # cost is manual labor I+,, tiiJ itJ I"I V I 1
It is calculated along with the fixed result and the result is given to the limiter/6K IJ%.

Output L, J of limiter/A: Near i, :J is detected by J sludge pump 3, and the pump is not controlled, and the amount of return sludge to return sludge circuit "1i74" is controlled.

/7i, I'm N'lj sludge man Y4 calculation! 41 device 1, and this control device toy 17 has S V I ilj settings 4. q li'j 10 (Q ll1l constant output bu J,
MLBB value from MLFJS total t, Himeiri water flow I) total 73
Sludge returned from inflow water rl'i degree meter 7 sludge i-
'% jf (value, sludge flow from sludge flow H1 old/3)
・Support and excess sludge circuit/gK installed extra 4i [11
Excess sludge from sludge v1 and tn1g is supplied respectively, and each of these values is controlled by the total surplus sludge calculation system 17, and the control output is supplied to the surplus sludge pump l via the on/off circuit iq. Control this. UO is a pipe for treated water flowing out from the final settling tank.

Next, let's talk about the operation of the second embodiment. first.

Using the SV meter 10af, plot the sludge settling curve shown in Figure 3, and calculate the sludge volume (5Vt) after t minutes from the start of σ1 determination, and 3
Measure the sludge volume (Ov, .) after 0 minutes. Directly placed g,' (
Svt, ) + (Sv+o) is SVI fraud M [
ML that is input to to b and input to this device @tab
Measure the SV work with the ML13S value of SS meter A. S.V.
i The output of the measuring device 10 is the return sludge amount calculation n, and the control device l
111 will be paid to Ko. At this time, the above svt is used to control the return sludge Mj=. In general, f+et in (1)
t 20 minutes to (approximately 10 minutes.) Here, the target value of the 871. sludge return rate (l-) is calculated by the following formula.

r, −r′+ k,・・・・・・・・・・・・
(2) However, r H sludge return rate, r'=intermediate sludge return rate, SVl; : E bond sludge MM, k1+kll: human power constant Substitute the sludge return rate (r) into equations (1) and (2) above. After the rf operation, the return rate (rl sum i1''(s ty Calculate the moving average of (r), and determine the return rate based on the moving average value (from season to season) based on equation (3). Perform the amount rIrII.

However, srj? l'l @ r lump... Upper and lower limits of the return rate However, QR tank, QR Yu... Upper and lower limits of the amount of returned sludge In actual control, the above moving average is
For example, a 24-hour moving average value ('F) is used.

This target value of the return rate (r) is held until the next moving average value is calculated. In order to prevent frequent fluctuations in the return rate or the ill value, a dead zone as shown in equation (3) above may be provided. A target return sludge amount is obtained from the return rate target value and the inflow water amount, and the rotation speed of the return sludge pump 3 or a control valve (not shown) is adjusted so as to reach the desired value. The actual amount of returned sludge is determined by the limiter/B according to the above equation (4).

No. 41e is a flowchart of the above-mentioned return sludge amount calculation control device 12. In the figure, T is OV time, N is the number of calculations, SUM t;J:ailb TS angle T is the moving average time, and The surplus sludge T^ calculation control will be described. Trench.

The SVl value is read at regular time intervals by the 8V engineering calculation device lOb. However, the return * (r) is calculated based on the inflow water volume (Qs) and the return sludge volume (litter) using the following formula.

After that, the distribution ratio (k
lfi - Determine, #l) Number of songs tl in Figure 5 - Determine (k) using formula (6).

k= t (SVI, r)−・−−−−・・−(
a) Let us now briefly discuss Figure 5. Figure '65 is a characteristic diagram showing the relationship between the weight ratio of final sedimentation tank sludge pieces (MP) to sludge mass (MA) in the aeration tank (MF/MA) and sludge return rate (r) as SVI changes. be. This rl! Figure 5 shows that as SVI increases, the increase rate (slope) for the sludge return rate (r) increases, and when 8Vi rises, the sludge return rate increases and the residence time of sludge in the settling tank increases. This indicates that the term must be shortened.

After determining the distribution ratio (k) t-, the aeration tank/
The sludge in the aeration tank (Mh) is calculated using the following equation based on the output of MLSSilA installed in the aeration tank.

MA-ML8S・Vt,... Old... (7) However, vA... Aeration tank volume (
7) Calculate the final sludge shell (MF) in the IT basin from the MA calculated by the formula and the distribution ratio (kl) using the following formula.

MF=ni-MA ・・・・・・・・・・・・(8) Filled in this equation (8)) 4 F and previous i! (Calculate the sludge h'r (io) in the treatment system using the following equation with 3M A.

M = MA + MF ・・・・・・・・・・・・(9) The value of λi calculated by this equation (9) is the inflow water; Moving average value 0 seasonal AN
) are commonly used. This average value CM (1)) is obtained by dividing the sum i1 by the number of calculations (N), and this average value (TJXi)) is calculated using the following 0.1 formula when the preset extraction time comes Good, target sludge for extraction
(M W ) 2 performances 1'g6.

Blue (1) MW-□ ・・・・・・・・・・・・(tQn-SE
T However, 1 is the drawing start time, n is the number of drawings, and SRT's average sludge retention time.

The remaining 11 sludge control is performed according to the MW value requested by the above Q□ formula. In this control, the surplus sludge pump l is activated at the withdrawal start time, and the amount of withdrawn sludge is calculated from the surplus sludge (Qw) and the concentration of the withdrawn sludge (normally, the return sludge concentration is used). Thereafter, this value is integrated, and the pump is stopped when the amount becomes equal to or larger than the target sludge amount (MW) to be drawn. This pump stop is performed when the following equation holds.

M W (1)≦ΣQwxOR・・・・・・・・・−・
OI) However, Qw is the excess sludge amount % axis is the return sludge concentration.

Note that the pump pressure is T - Ts, T(i), and is turned off when the equation (11) is established.

FIG. 6 is a flowchart of the above-mentioned surplus sludge amount calculation and control device, and T, N, and 5ulvlij in the figure have the same meaning as FIG. 4. As mentioned above, calculation control of the remaining sludge is performed from 1 to 1, but the moving average time interval at that time is 24 hours (
1), excess sludge removal interval, etc. 1 (1e #J: l ) J When pulling out n times at equal time intervals (j
1, and the number of times of extraction (n), the 61st moving average time becomes K as shown in FIG. Using this Fig. 7, we will further discuss starting and stopping the pump ψ.

At the start of excess sludge extraction, the sludge i in the treatment system becomes L1].
[1t1)] is determined, and the first drawn sludge Jl (M wU ) is determined by equation s (t'). , and the excess sludge pump l is started. Then, by formula 00, the product n
When the actual amount of sludge drawn becomes equal to or larger than the target value MW(1), the pump is stopped.

As described above, according to the present invention, the following effects can be obtained.

(1) It is possible to measure the negative changes in the amount of sludge in the aeration tank and the sludge in the final settling tank due to changes in the settling characteristics of activated sludge (changes in SV work).

(2) Since it is incorporated into the surplus sludge amount calculation control device N as a return heavy metal parameter, mutual interference between the return sludge concentration tllu and surplus sludge control does not occur.

(3) Since the total amount of sludge in the system (the amount of sludge in the aeration tank and the amount of sludge in the final settling tank + In) is subject to control, the influence of fluctuations in the SV process and return rate cannot be ignored.

(4) With conventional sludge daily control, the sludge daily age during bulking (when SV work is 200 or more) is longer than the set value.
Sludge tends to overflow from the final settling tank, but with the control of the present invention, the sludge retention time (BRT) does not change even during pulging, so the above problem does not occur.

(5) From the above, it is possible to completely improve the removal of COD, nitrogen, and fi.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional sludge H total control system, Figure 2 is a diagram showing an example of this HatsuJ, Figure 3 is a sedimentation curve diagram using an SV meter, and Figure 4 is a diagram showing an example of this method. A flowchart to describe the operation of return sludge control, Figure 5 shows the sludge distribution ratio (1 t)
Characteristic diagram for determining the
Detailed 70-booyat describing the operation of a1+, Figure 7 tel, Explanation 1 describing the number of times of sludge extraction and moving average time
It is Δ. /...Aeration tank, Co...Final sedimentation tank,
3...Return sludge pump, V...Interest rate sludge pump, 6
...MLSB meter, F...excess sludge circuit 6F%
IO...FIVI measurement device @, io a -・-s
v meter, lOb...SvI performance JT device, /co...return sludge amount calculation control device, l,? ... Inflow water eater I's"
... Return sludge circuit, /3 ... Return sludge circuit 1. ψmeter,
/7... Surplus 1 sludge amount calculation control device, lza... Excess sludge circuit.

Claims (1)

[Claims] (1) A sludge volume index measurement device that determines the sedimentation characteristics of activated sludge in the aeration tank from the sludge volume and the measured value of mixed suspended chest n'-nl after a predetermined time has elapsed from the start of measurement. , the measured value from this device, the inflow water flowing into the aeration tank and the return sludge R returned to the aeration tank are supplied, and this f
: Roast 31. A return sludge amount calculation control device that controls the amount of sludge returned from the final settling tank to the aeration tank;
1111 constant value from the measuring device, the inflow water measure flowing into the aeration tank, the mixed suspended matter power r11
The R1 measurement value, the return sludge air, and the surplus sludge pieces pulled out from the final settling tank are supplied, and each of these is operated to control the amount of surplus sludge pulled out from the final settling tank. Did you have equipment? :, Activated sludge slope control device 1j0 with pipe CR