JPS5876189A - System for purification of water with active sludge - Google Patents

Abstract

PURPOSE:To stabilize the quality of purified water, while holding the total amount of sludge in the system at a predetermined value, in purifying sewage or the like, by setting the total amount of sludge at first, and using the set value and an estimated value for the total amount of sludge obtained from information at a specified point to set the amount of excess sludge to be withdrawn. CONSTITUTION:From the output of an MLSS meter 6 inserted into an aerating cell 1, the total amont of sludge is calculated by an arithmetic circuit 7 for the total amount of sludge. On the other hand, an estimated value for the total amount of sludge is calculated by an arithmetic circuit 8 taking into consideration the quality of water to be purified, the property of sludge, the amount of air blow and the amount of excess sludge to the withdrawn. The set value of the total amount of sludge from the arithmetic circuit 8 and the estimated value for the total amount of sludge from the arithmetic circuit 7 are inputted to an arithmetic circuit 9 to determine the amount of excess sludge to be withdrawn. In addition, the outputs of a flow meter 11 for excess sludge and a densitometer 10 for excess sludge are processed by an arithmetic unit 12 to calculate the actual amount of excess sludge to be withdrawn. The output of the arithmetic unit 12 and the output of the arithmetic circuit 9 are inputted to a controller 13 for withdrawing excess sludge, withdrawal is performed by the operation of an excess sludge-withdrawing pump 4, and the total amount of sludge is held constant.

Description

Detailed Description of the Invention The present invention is an activated sludge water treatment method for purifying sewage using activated sludge composed of aerobic microorganisms. Activated sludge containing aerobic microorganisms is mixed into the sewage at the inlet of tank (1). In the aeration tank (1), the sludge removes organic matter from the sewage.
Purify sewage by decomposing and absorbing water. The mixed liquid of sewage and sludge is solid-liquid separated into activated sludge and supernatant water in the final settling tank (2), and the supernatant water is discharged as treated water. On the other hand, the solid-liquid separated activated sludge is returned to the aeration tank (1) as return sludge by the return sludge pump (3). Also,
A portion of the total sludge volume is transferred to the excess sludge extraction pump (4).
It is pulled out of the system as surplus sludge and treated as sludge.

Conventionally, in the research field μ, a 77M ratio constant control method, an SRT control method, etc. have been devised as methods for managing the amount of sludge in an activated sludge process.

77 The constant M ratio control method is a method of keeping the IF/M ratio, which is the ratio between the amount of organic matter flowing in and the amount of microorganisms in the activated sludge process system, constant to improve and stabilize the quality of treated water.

Also, SR? The control method is the microbial retention time within the activated sludge process system.
With a control method that keeps the tionTime constant, multiple times, every day,
A certain percentage of the total amount of sludge (total amount of sludge/EI R (day)
) is extracted as surplus sludge, the sludge in the system is renewed, the properties of the sludge are maintained in good condition, and the quality of treated water is improved and stabilized.

However, in actual facilities, the 77M ratio constant control method requires continuous measurement or prediction of the concentration of inflowing organic matter, but there are many practical techniques for measuring or predicting this, and the amount of organic matter inflowing is difficult. Since the fluctuations in the amount of sludge are closely related to human life, they have considerable temporal fluctuations, whereas the total amount of sludge has small temporal fluctuations and cannot respond to fluctuations in the amount of inflowing organic matter, so it is currently impossible to achieve this goal. be.

In addition, in the EIRT control method, it is essential to estimate the total sludge amount by some method, and
A model-type buff meter that determines the quality of the treated water must be constantly searched for and updated, and there are drawbacks such as the transient response time required to change settings and values, which can take several days. Furthermore, in actual facilities, inflowing sewage water contains a considerable amount of sludge, but this is not taken into consideration at all.

In addition, since the above two control methods conventionally focus only on improving and stabilizing the quality of treated water, it is important to reduce operating costs such as air supply amount and surplus sludge generation amount (a part of sludge treatment amount). Effects cannot be expected directly.

For these reasons, in actual facilities, the 11M constant ratio control method and the 5RT constant control method are not used, and operation management is mainly based on the long experience and intuition of facility operators. This is the actual situation. For this reason, the treated water quality and sludge properties have not been improved or stabilized, and the amount of air supplied and the amount of excess sludge have not been reduced. In some cases, the activated sludge treatment process could even fail due to over- or under-operation.

In view of the above-mentioned actual situation, this invention is a method most suitable for actual facilities, in which the total amount of sludge, which is the sum of the amount of sludge stored in the aeration tank, the final settling tank, and the return sludge pipe, is reduced to a predetermined amount. We provide an activated sludge water treatment method that suppresses fluctuations in the Y/M ratio that determines treated water quality, improves and stabilizes treated water quality and sludge properties, and reduces treatment costs. It is intended to. The effects of keeping the total sludge volume constant will be discussed in detail.

First, the quality of treated water is determined by the 77M ratio as shown in FIG. As shown in the figure, in the region where the IF/M ratio is low, the quality of the treated water is good and stable, but as the F/M ratio increases, the quality of the treated water suddenly deteriorates. In the present invention, since the total amount of sludge that determines the F/M ratio is used as the control amount, it is possible to promptly respond to fluctuations in the amount of inflowing organic matter. However, as mentioned above, due to fluctuations in inflow organic matter,
It is almost impossible to control the total amount of sludge, and near the dormitory,
P/M based on changes in inflow organic matter and the total amount of sludge
The ratio changes, and the quality of the treated water also changes. However, according to the present invention, by keeping the total amount of sludge and sludge in the system constant, fluctuations in the 77M ratio, which determines the quality of treated water, can be suppressed to the extent of fluctuations in the inflow organic matter load.

(See Table 1) Table 1 Unit: Average value of inflow COD load ζ Standard 11i1! I (
t/day) Mean value of COD-35, standard deviation (1/day)
As a result, fluctuations in treated water quality are kept to a minimum, and IF/
Almost the same effect as M ratio control is obtained. This effect is 77M
The higher the ratio, the greater the effect (see Figure 2). The properties of sludge are also closely related to the IF/M ratio, and generally become worse if the F/M ratio is too high or too low. Therefore, the total amount of sludge is
If the 77M ratio is kept constant and within a certain range, the sludge properties will not deteriorate.

In general, regarding treated water quality and sludge properties, 1! M ratio 0
It is said that 1-0.8 is good. Tsumashi FZM ratio is 0
．． The most expensive part of the activated sludge water treatment process is that the treated water quality, sludge properties, and air flow rate will be stabilized if maintained at 1 to 0.8 (1! day).

This is the air flow rate and sludge treatment part.

As shown in FIG. 8, the amount of air supplied increases linearly as the total amount of sludge increases. Further, as shown in FIG. 4, the amount of excess sludge drawn decreases linearly as the total amount of sludge increases.

The broken lines in FIGS. 8 and 4 are the results obtained from the microbial respiration rate model and growth model, respectively. From these, it is possible to understand the air supply amount and excess sludge extraction amount using each model.

By creating an evaluation function that takes these items into account, determining the set value for the total sludge volume, and operating the activated sludge process, the quality of treated water and sludge properties can be improved and stabilized, and treatment costs can also be reduced. It becomes possible to do so.

Furthermore, the response time due to fluctuations in inflow load is shorter than that of SRT. (FIG. 5) That is, in SRT control, excess extraction is not stopped, whereas in total sludge amount control, excess extraction is stopped, and the set value can be changed in a short time.

Next, an embodiment of the present invention is shown in FIG.

In Figure 6, (6) is an MLS that is inserted at a specific point in the aeration tank and obtains information to understand the total amount of sludge in the system.
It is an S meter. (7) is the sludge total amount calculation circuit υMLBB
Using the output of total (6), calculate the total amount of sludge. (8)
is a calculation circuit for the total sludge volume set value, which calculates and determines the set value in consideration of the treated water quality, sludge properties, air supply amount, and excess sludge extraction amount. (9) is the surplus sludge extraction amount calculation circuit, and the total sludge tank setting value which is the output of the calculation circuit (8) and the calculation circuit (7)
The amount of excess sludge to be extracted is determined using the total sludge amount control value that is the output of . αQ is a surplus sludge concentration meter, (b) is a surplus sludge flowmeter, @ is a calculator. Processes the outputs of the surplus sludge concentration meter αq and surplus sludge flowmeter (b), and calculates the amount of excess sludge extracted. . (To) is an excess sludge extraction controller, which operates the excess sludge extraction bonder (4) according to the output of the computing unit (2) and the computing unit 1 (8), and performs excess sludge extraction to keep the total amount of sludge constant. Keep it.

Next, the operation of this device will be explained.

The total amount of sludge (ST) in the activated sludge treatment process system is expressed by the following formula.

8rIllIS1+S2+S,・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・ IIJ(
In equation 1), Sl, sl, and s3 are the amounts of sludge stored in the aeration tank, final settling tank, and return sludge pipe (5), respectively.

Furthermore, in actual facilities, the relationship between Ss<<Syu and B2 and horses can be almost ignored. Sludge constantly circulates between the aeration tank (1), the final settling tank (2), and the return sludge pipe (5), and if the amount of inflowing sewage is constant, the ratio of 4 to 4 remains constant. , ST is shown as the following equation.

STW A-8!・・・・・・・・・・・・・・・
(2) However, if the amount of inflowing sewage changes, the amount of sludge pushed out from the aeration tank (1) to the final settling tank (2) will also change. The ratio changes.

Considering this, the total amount of sludge 6T can be expressed as follows.

8T= a −flQJ ・S□・・・・・・・・・
・River・・・・・・・・・ (3) Here, Q is the amount of inflowing sewage.

In this device, an MLB-8 meter (6) is inserted at a specific point in the aeration tank (1) to estimate the total dry amount of sludge, and the MLSS
is being measured. Further, on a steady basis, the following equation holds between the sludge concentration tc) inflow sewage volume IQ,) at a specific point in the sludge circulation pipe and the total sludge volume (BT).

BT-A @flQ, )・C・・・・・・・・・・・・
・・・・・・・・・・・・ (4) Here, M is a constant of proportionality.

In actual facilities, there is little time for the steady state to occur, so the measured values and
If it is smoothed in about one day and used, it becomes possible to estimate the total amount of sludge with kanasi accuracy.

Using the outputs of these types of calculations MX and BBftf (6), a total sludge amount estimation calculation circuit (7) performs the calculation, and an estimated total amount of sludge is obtained as an output of the calculation circuit (7).

The sludge total amount setting calculation circuit (8) determines the sludge total amount setting value, but at this time, the inflow organic matter load, the microbial respiration model, and the microbial growth model μ are required.

These may be determined by performing manual analysis intermittently, or may be determined using a computer or the like by arranging a measuring device to measure the state every moment.

Based on the inflow organic matter amount and microbial respiration model 1 growth model, the relationship between the total amount of sludge, the 77M ratio, the air supply amount, and the amount of excess sludge can be obtained as shown in FIG.

These are appropriate / y ratio value, i.e. 0.1 to 0
．． 8 (1/day), and then determine the total amount of sludge that minimizes the sum of the air supply amount, the electricity cost based on the excess sludge amount, and the sludge treatment cost within that range.

Next, using the outputs of the calculation circuits (7) and (8), the excess sludge amount calculation circuit (9) calculates the target value of the surplus drawn sludge amount.
□ (SW) is determined.

sW ” G (Sr -8?) ””””””=
(6) In equation (6), G is the proportional integral gain, ST
is the estimated total sludge volume S is the set value of the total sludge volume.

The output of the arithmetic circuit (9) is connected to the surplus withdrawal controller (to) as a set value input, and the surplus sludge withdrawal bonder (3) is operated depending on the output of the surplus withdrawal controller (to) to set a predetermined value. Excess sludge is removed to keep the total amount of sludge constant.

If this device responds to fluctuations in the amount of inflowing sewage and controls the return sludge flow rate so as to keep the MLSS in the aeration tank constant, the MLSS in the aeration tank will be kept more constant, and the quality of the treated water will be even better. Stabilize.

As described above, according to the present invention, since the total amount of sludge is maintained at the set value of the amount of sludge a taking into consideration the quality of treated water, sludge properties, and sewage treatment cost, the quality of treated water and sludge properties are also improved and stabilized. This has the effect of reducing wastewater treatment costs.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an overview of the activated sludge sewage treatment process;
Figure 2 is a diagram showing the relationship between F/y ratio and treated water quality.
Figure 4 shows the relationship between total sludge dry amount and air supply amount, Figure 4 shows the relationship between total sludge dry amount and surplus sludge dry amount, and Figure 6 shows the relationship between total sludge dry amount and excess sludge dry amount.
The figure is a diagram showing the relationship between the control method and the response time, and FIG. 6 is a schematic configuration diagram showing an embodiment of the activated sludge water treatment method according to the present invention. (1)... Aeration tank, (2)... Final settling tank, (3)
... Return sludge pump, (4) ... Excess sludge extraction pump s' (5) ... Return sludge pipe, (6) ... ML
SSli”47) Preliminary sludge amount calculation circuit, (8)...Total sludge amount setting calculation circuit, (9)...Excess sludge extraction amount calculation l
Abbreviation, QQ...excess sludge extraction controller, (b)...excess sludge concentration meter, @...excess sludge flow meter, (to)...excess sludge amount calculation circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Makoto Kuzuno (1 other person) 2nd figure ratio (VB) Figure 4 Figure 3 Figure 4 Special)/I\
〆r) 7th
Figure - F/M ratio - - - Transmission Frf - - Continuation of Chapter Surplus 55 Shingenkai, page 1 ■ Applicant Mitsubishi Electric Corporation 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Procedural amendment (Method) % formula % 2. Name of the invention Activated sludge water treatment method 3. Person making the amendment 5. Date of procedural amendment order (method) February 28, 1980 (1) Sharp parts] (2) The column for the brief explanation of the drawings in the specification and Etsube Yoshida's section will be supplemented as shown in the attached sheet. (2) In the Meiho' book, in the second line of page 13, the phrase ``This is a schematic configuration diagram.'' was replaced with ``Schematic configuration diagram. , total sludge dry amount, and sludge properties.'' 8. List of attached documents (1) Power of attorney (for Mizushima Misumi) 1 copy (2) Power of attorney (for Etsube Yoshida) 1 copy or more

Claims (1)

[Claims] In the activated sludge treatment method, inflowing sewage is purified using aerobic microorganisms in an aeration tank, the activated sludge mixture flowing out from the aeration tank is separated into solid and liquid in a final settling tank, and the precipitated sludge is returned to the aeration tank. The set value is the total amount of sludge, which is the sum of the amount of sludge in the aeration tank, the final settling tank, and the return sludge pipe, taking into account water quality, sludge properties, air supply amount, and excess sludge extraction amount.
In addition, the total amount of sludge is estimated based on one or more pieces of information from one or more specific points in the system, and the amount of excess sludge to be extracted is derived by combining the estimated value and the set value.
The activated sludge water treatment method is characterized in that the total amount of sludge is maintained at a set amount by performing sludge extraction according to the derived amount of excess sludge.