JPH01242196A - Control of operation of batch apparatus for treating activated sludge - Google Patents

Abstract

PURPOSE:To stabilize water quality treated in the title apparatus by operating the title apparatus by completing the treatment at a time point when a gradient of increase of the concn. of dissolved oxygen, which increases in accompany with the lapse of time, attains a value predetermined under above a fixed valve of concn. of dissolved oxygen. CONSTITUTION:Waste water 1 is received in a pump pit 2, then pumped up to a batch aeration tank 4 with a storage pump 3. The waste water is mixed in the aeration tank 4 intimately with activated sludge in the aeration tank 4 by the effect of air discharged from a blower 5 and fed through an air diffusing pipe 6, and treated. A value of DO is sensed by a sensor 8 in the aeration tank 4, and an end point of treatment is determined basing on the result of computeric 7 analysis. When aeration is ceased due to completion of treatment, the activated sludge settles to the bottom of the aeration tank 4. Supernatant liquid is discharged as treated water 9 with a discharge pump 10, and excess sludge is withdrawn into an excess sludge storage tank 12 by means of a discharge pump 11, and stored therein. Thus, the treatment is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the operation of a batch type activated sludge treatment apparatus.

Conventionally, the operation management of batch-type activated sludge treatment equipment was carried out based on the experience of operation managers with technical skills above a certain level, but with the present invention, it is possible to always operate batch-type activated sludge treatment equipment under optimal conditions. As a result, the present invention can be used in industries where it is not expected to have a full-time operation manager for activated sludge treatment equipment, such as small and medium-sized food manufacturing industries, and can also be used in all industries. This method is very effective in improving the environment as a method of controlling the operation of wastewater treatment equipment that always provides the best water quality in a stable manner.

[Conventional technology]

Batch activated sludge treatment of wastewater has a long history, but this treatment has traditionally been viewed as a simple device among activated sludge treatment equipment. However, this treatment has recently been evaluated for its effectiveness in suppressing filamentous bacteria, removing phosphorus, and removing nitrogen, and the batch activated sludge treatment method is being actively reviewed.

The conventional general batch activated sludge treatment is basically a system that performs raw water inflow, mixing and agitation, aeration treatment, solid-liquid sedimentation separation, and treated water discharge in one tank, and is extremely simple. It is a device. Operational control of such batch activated sludge treatment includes water level control, timer control, and dissolved oxygen concentration (hereinafter referred to as D).
This is often done using a control system (referred to as ``o''), but basically it relies entirely on the experience of the operation manager.

[Problem to be solved by the invention]

The batch activated sludge process is usually operated according to the steps shown in Figure 1. That is, in Figure 1, the om person process (1)
As factories operate, wastewater is discharged and flows into the wastewater treatment system.

(2) Water caused by rising water level in the pump pit The water pump that senses the level Be in operation.

oIIi Air process (3) The aeration device starts by starting the timer.

(4) Water pumps will be installed upon completion of factory operations The program stops.

(5) Operation of aeration equipment after a certain period of time has passed or stop the DO meter. Aeration equipment is installed when DO level is achieved. stop operating.

(Note) In the limited aeration batch activated sludge method, which is a variation of the batch method, aeration is not carried out until 16:00 as shown in the time chart in Figure 1, and aeration is started when the inflow is finished.

0 Sedimentation Separation Step (6) The settling time is set using a timer or a combination of a timer and a sludge interface meter.

0 discharge process (7) The discharge of treated wastewater is controlled using a timer or a combination of a sludge interface meter and a water level meter.

Conventional batch activated sludge methods are generally operated in the manner described above, but due to fluctuations in concentration on the raw water side, fluctuations in water quality, fluctuations in water volume, seasonal fluctuations, fluctuations in MLSS 1 degree, etc. On the other hand, since the operating conditions do not follow suit, the operation of batch type activated sludge treatment equipment has always had the problem of unstable treatment performance. For this reason, timer settings, DO levels, etc. are always changed based on the judgment of the operation manager, but the quality of treated water is affected by fluctuations in the raw water and lacks stability.

Therefore, the present invention eliminates the problems of the prior art described above,
It is an object of the present invention to provide a method for controlling the operation of a batch type activated sludge treatment device, which has stable treatment performance and can obtain stable treated water quality without being affected by fluctuations on the raw water side.

[Means to solve the problem]

According to the present invention, when operating a batch type activated sludge treatment device, the dissolved oxygen concentration in the aeration tank, which changes as the wastewater treatment progresses in the aeration tank, is measured and analyzed, and the concentration of dissolved oxygen exceeding a certain value is determined. The rising gradient of dissolved oxygen that increases with time under
A method for controlling the operation of a batch type activated sludge apparatus is provided, which controls the operation of the apparatus by determining that the treatment is completed when the amount reaches mg/l/hr.

[Effect]

Experience has shown that Do in the aeration tank is deeply involved in processability. In continuous activated sludge equipment, the DO in the aeration tank is controlled to a constant value to ensure stability of treatment. However, in the case of the batch type, the DO varies depending on changes in processability, elapse of processing time, etc., so controlling with a fixed DO value as in the continuous type does not have much effect. In the case of the batch activated sludge method, the treatability of Do in the aeration tank and wastewater is particularly remarkable.

Figure 2 shows the D inside the aeration tank when treated with the batch activated sludge method.
It shows changes in O and residual COD over time. It can be seen that there is a clear correlation between DO and COD, and that the processing is completed when Do has completely increased. It is estimated that stable processing performance can be obtained by focusing on this and controlling the operation. However, in order to control this, it is not possible to judge based on the DO value. The A value of DO in Figure 2 is not always constant and varies from day to day by 8■/! or 6
mg/l and always fluctuates.

Such fluctuation factors include aeration air volume, water temperature, and MLSS.
Examples include load amounts such as degree I, COD, and BOD. These factors are constantly changing, and it is difficult to stabilize them at wastewater treatment sites.

Therefore, if DO is controlled at a constant level, DO may still be in the process of reaching its upper limit, and pollutants in wastewater such as COD and BOD may remain undecomposed, or in some cases equilibrium may not be reached without reaching the set DO value. As a result, unnecessary aeration may have to be continued indefinitely, and DO
There were problems with using values as control indicators. Therefore, it was determined that control would be possible by grasping the point at which DO stabilized at a certain level instead of the DO value and using that point as the processing end point. Q control is based on the increasing slope of DO (Oz mg/e/hr)
, the rising slope gradually becomes smaller, for example 0.15
mg/1. /hr, preferably 0.1-0.2 mg/
The point at which the temperature reached 1/hr was defined as the end point of the treatment.

However, as is clear from the graph in Figure 2, the increasing slope of DO is 0.1 to 0.2 mg/I! , /hr appears twice. The first time is when the DO starts to gradually increase from a low level, and the second time is when the increased DO converges to a constant value. The processing end point is at the point where the temperature rises the second time, not at the first time.

This first rising slope always appears at a low level of DO value (approximately 3 mg#! or less), so it is a constant value (DO#!
The rising slope of DO of 3 mg/1 or more is 0.1 to 0.2 ■/
The control point may be set at the time when it reaches l/hr.

According to the present invention, by performing control using the treatment end point as an index, the aeration air amount, water temperature, MLSSe
It has become easy to always obtain a constant and stable treated water quality without being affected by fluctuations due to load amounts such as It degree, COD, BOD, etc.

FIG. 6 is an example of an apparatus for carrying out the present invention. After the wastewater to be treated (■) is once received in the pump pit (■), the water is pumped to the batch type aeration tank (■) using the water pump (■). The wastewater that has entered the aeration tank is thoroughly mixed with the activated sludge in the aeration tank and treated by the air discharged from the blower (1) and blown through the aeration pipe (2). Do, which is an index of treatability, is detected by Do sensor (2) in the aeration tank, and the end point of the treatment is determined based on the analysis results of computer (2). When the treatment is completed and aeration is stopped, activated sludge settles to the bottom of the aeration tank. The supernatant water is discharged as treated water (■) using a discharge pump [phase]. At this time, the surplus sludge is drawn out by the surplus sludge extraction pump (2) into the surplus sludge storage tank (2) and stored there, completing the treatment.

〔Example〕

The control Do gradient of the present invention and the processing situation in the DO gradient region before and after the control Do gradient are shown in the following Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Processability and treatment status in the area of 0.0 to 0.05 mg/l/hr of real 1 secondary low control DO gradient (the point where Do rises and almost reaches equilibrium) Disaster Control I Control DO gradient 0. 1~0.2111g/l/hr
Processability and processing status in the region (point 2 of the present invention control region where Do rises and is slightly before reaching equilibrium) Disaster control main control Do gradient 0.3 to 0.4 mg/l/hr
Processability and processing status in the area (Do increases linearly,
Points within the curved area) 0 Results Using synthetic sewage, a treatment test was conducted under the following conditions and the treatment properties were compared.

(1) Water to be treated BOD concentration 800mg//! (
2) Water to be treated COD concentration 550■/n(3)M
LSS concentration 3200■/1 (41B OD
M L S S load 0.25 kg/kg
-D results are shown in Figures 3, 4 and 5, as well as Tables 1, 2 and 3.

Comparison of 0 margin processability (1) SVI value The SVI value at the start of the test was 80Ild! /g, but in Example 3, it gradually started to rise and became unstable. In the latter half of the test, the sludge began to become slightly viscous,
A tendency towards viscous bulking has emerged. Under the microscope, almost no filamentous bacteria were observed. Comparing Example 1 and Example 2, Example 2 was extremely stable and good, but Example 1 showed a tendency for the SVI value to increase, albeit slightly, and the treatment was not continued. It was estimated that the price would rise further as it progressed.

(2) Treatability of BOD In Example 3, the raw water BOD concentration was 800 ■/L, and the treatment was performed well at around 10 ■/P at the beginning of the test, but the BOD value increased orally and 2 In the second week, it exceeded 20 ■/l and continued to rise further. Ability troublesome 2 is lO■/
Although it is stable at less than 1, Example 1 had a tendency to become higher, albeit slightly.

(3) Treatability of COD Although the tendency is almost the same as that of BOD, the removal rate in Example 3 was abnormally high and became 90% or less. Examples 1 and 2 were almost unchanged.

From the above, when looking at DO at the end of aeration, all three conditions are in the range of 6 to Bmg/l, which is the most conditional control concentration for Do control in conventional batch activated sludge treatment. It has a good concentration. However, as far as we can see from the examples, in Example 1, the activated sludge was in the autolysis region, so the activated sludge was dispersed in the aeration tank, and there was a tendency for the flocs to become fine. Furthermore, the water quality was unstable. In Example 3, although the DO value was 6/1 or more, the treatment was not completed, the quality of the treated water deteriorated, and the properties of the activated sludge also deteriorated. In Example 2, the treated water quality was good and stable, and the activated sludge separation and flocculation properties were also good.
It was confirmed that this was the most excellent control region in terms of conditions compared to the other two cases.

[Effects of the invention] Conventionally, the operation of batch-type activated sludge treatment equipment largely relied on the experience of the operation manager, but with the present invention, the optimal treatment conditions have been confirmed, and automatic control using a DO meter has become possible. This was also easily possible.

As a result, the best processability is always obtained, and since there is no need for excessive aeration, operation and automatic control are possible with minimal running costs.

[Brief explanation of the drawing]

Figure 1 is a time chart showing the normal operation and treatment process of the conventional batch activated sludge method, and Figure 2 is a time chart showing the DO and residual COD in the aeration tank when treated with the batch activated sludge method. FIG. 3 is a graph showing the oral change in SVI value using the control Do gradient as a parameter, and FIG. 4 is a graph showing the oral change in COD treatment property using the control Do gradient as a parameter. FIG. 5 is a graph showing oral changes in BOD treatment using the control Do gradient as a parameter, and FIG. 6 is a drawing showing an example of an apparatus for carrying out the present invention. . ■・・・Wastewater to be treated ■・・・Pump pit■・
・・Storage pump ■・・Aeration tank ■・・Proa ■・・Diffuser pipe ■・・Computer
■・・・DO sensor■・・・Treatment water [
Phase]...Discharge pump 0...Excess sludge extraction pump■...Excess sludge storage tank

Claims (1)

[Claims] 1. When operating a batch-type activated sludge treatment equipment, the dissolved oxygen concentration in the aeration tank, which changes as the wastewater treatment progresses in the aeration tank, is measured and analyzed, and when the concentration of dissolved oxygen exceeds a certain value, A method for controlling the operation of a batch type activated sludge treatment equipment, in which the operation of the equipment is controlled with the time when the upward slope of dissolved oxygen that increases over time reaches a predetermined value as the treatment being completed.