JPH0691294A - Operation control method of batch type active sludge treatment - Google Patents

Abstract

PURPOSE:To obtain easily data on the factors of a reactor and to provide an operation control method for maintaining the reactor under an optimum condition. CONSTITUTION:In a batch type active sludge treatment apparatus, waste water charged to a reactor 1 equipped with a pH meter and a dissolved-oxygen concentration meter 21 is denitrified under an anaerobic condition and then nitrified by nitrification bacteria under an aerobic condition with air supplied, and the supernatant liquid and the precipitate of sludge in the reactor 1 are extracted by pumps. An oxidation-reduction potentiometer 22 is attached to the reactor 1, and the conditions of denitrification and nitrification are judged by measuring the difference between the oxidation-reduction potentials in an anaerobic state and an aerobic state under cultivation. On the basis of this judgment, factors of the reactor 1 are obtained, providing an operation control method. The factors of the reactor 1 include denitrification time, aeration time, amount of air supplied, and amount of sludge extracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control method for determining the denitrification and nitrification state of wastewater in a batch type activated sludge treatment by using an oxidation-reduction potentiometer and controlling a factor affecting the operation state of a reaction tank. It is about.

[0002]

2. Description of the Related Art Conventionally, a batch type activated sludge treatment method has been known as one of the treatment processes for sewage and the like. This batch type activated sludge treatment method is mainly a method of repeating the cycle of inflowing wastewater into a single biological reaction tank, aeration, precipitation, and discharge, and the nitrogen component in raw water is decomposed into ammoniacal nitrogen. To be done. Then, the ammoniacal nitrogen is changed into nitrite nitrogen and nitrate nitrogen by the nitrification reaction under the condition that nitrifying bacteria are present and dissolved oxygen (abbreviated as DO hereinafter) is abundant.

The distribution of the set time of each process in the above-mentioned one cycle can be arbitrarily changed, and for example, the anaerobic state and the aerobic state can be created by stopping or restarting the aeration in the reaction tank. It can biologically remove nitrogen and phosphorus. In particular, in the case of small-scale sewerage, the above-mentioned method has attracted attention as a practical treatment technology and is being put into practice.

[0004]

In order to perform efficient and economical operation in such a wastewater treatment method using the conventional activated sludge treatment method, a factor that influences the operating state of the reaction tank is required. The denitrification time, the optimum aeration time, the amount of air inflow, and the amount of sludge withdrawal can be controlled, but at present the control including monitoring of nitrification reaction is not implemented. .

The present invention has been made in view of the above circumstances, and provides an operation control method capable of easily obtaining data relating to factors that influence the operating state of a reaction tank and maintaining the operating state of the reaction tank optimally. It is intended to be provided.

[0006]

In order to achieve the above-mentioned object, the present invention denitrifies the wastewater flowing into a single reaction tank equipped with a pH meter and a dissolved oxygen concentration meter under anaerobic conditions. In a batch type activated sludge treatment device in which nitrification by nitrifying bacteria is carried out under aerobic conditions by sending in air, and the supernatant of the reaction tank and sludge as a precipitate are pumped out. A redox potential meter is installed in the tank to determine the denitrification and nitrification state of the treated water by measuring the difference between the redox potentials in the anaerobic state and the aerobic state during acclimation. Provided is an operation control method for batch activated sludge treatment, which controls a factor that influences an operation state.

The factors that influence the operating state of the reaction tank are:
It is characterized by the denitrification time, aeration time, the amount of air sent in and the amount of sludge drawn out.

[0008]

According to such an operation control method, by denitrifying waste water in an anaerobic state and then performing aeration, decomposition of organic substances and nitrification based on the action of microorganisms are performed. At this time, the dissolved oxygen concentration meter installed in the reaction tank measures the dissolved oxygen concentration of the wastewater, and the oxidation-reduction potential meter measures the oxidation-reduction potential of the wastewater to maintain the dissolved oxygen concentration above the set value. The feed rate of is controlled. Furthermore, the redox potential value in the anaerobic state and the redox potential in the aerobic state are measured by an oxidation-reduction potentiometer, and a change amount, which is the difference between them, is obtained. The change amount and the total nitrogen (TN) removal rate The state of TN removal of treated water is grasped from the correlation diagram with, and denitrification time, aeration time, which are factors that influence the operating state of the reaction tank,
The control is performed so that the air flow rate is optimum.

[0009]

EXAMPLES Examples and comparative examples of the present invention were examined based on the batch type activated sludge treatment device shown in FIG. In the figure, 1 is a reaction tank, and this reaction tank 1 is arranged in a constant temperature tank 2. The reaction tank 1 is provided with a diffusing pipe 4 that diffuses the air sent from the blower 3, and a stirring mechanism including a stirrer body 5 and blades 6.

On the other hand, 7 is a raw water preparation tank, and this raw water preparation tank 7 has a stirring mechanism composed of a stirrer body 8 and blades 9,
A liquid level gauge 10 is provided. Reference numeral 11 is a stock solution, and 12 is tap water. The stock solution pump 13 and the water pump 14 respectively supply the stock solution and the tap water to the raw water preparation tank 7. Reference numeral 15 is a pump for discharging the supernatant from the reaction tank 1, and 16 is a pump for extracting excess sludge.

The reaction tank 1 has a pH meter 20 as a measuring instrument and a dissolved oxygen concentration meter 21 for measuring the dissolved oxygen concentration.
(Hereinafter abbreviated as DO meter 21) and redox potentiometer 22 (Ox
idation reduction potential, hereinafter abbreviated as ORP total 22). Then, the values detected by the pH meter 20, the DO meter 21, and the ORP meter 22 are input to a sequence controller (not shown), and the controller 3 causes the blower 3, the supernatant liquid discharging pump 15 and the excess sludge drawing pump 16 to be input. The operating state of is controlled.

The redox potential, which is the measurement principle of the ORP meter 22, refers to the potential difference that occurs when a standard hydrogen electrode and a platinum electrode are placed in a solution containing an oxidizing state and a reducing state, and the oxidizing or reducing power of the solution. It can be used as an index to know the strength of. This redox potentiometer is usually called "redox
"meter" is used. The present Example is characterized in that the measured change amount of the redox potential was used as a monitor of the total nitrogen removal rate.

In the present embodiment, the stock solution 11 is a meat extract,
An artificial sewage mainly composed of peptone and sodium acetate is prepared, and it is put into the raw water preparation tank 7 together with the tap water 12, and the stirring mechanism is operated to stir the raw water, and then the raw water is allowed to flow into the reaction tank 1 through the pipe line 17. The operation pattern of the reaction tank 1 is 15 minutes for raw water, 1 hour for anaerobic stirring, 4 hours for aeration with the blower 3 operating, 30 minutes for precipitation, and 15 minutes for discharging (50% of the total amount is discharged) for a total of 6 hours for one cycle. And operated for 4 cycles a day.

That is, stirring the raw water for 1 hour in an anaerobic state after the raw water has flowed into the reaction tank 1 and then performing aeration by aeration from the air diffusing tube 4 as the blower 3 is driven, the action of microorganisms is improved. Based on this, organic matter in the raw water is decomposed, and at the same time, organic nitrogen in the raw water is ammonia nitrogen (N
Becomes H ₄ -N), the ammonium nitrogen is oxidized to nitrite nitrogen (NO ₂ -N) by nitrifying bacteria in the activated sludge under aerobic conditions (Nitrosomonas), further nitric acid bacteria (Nitro
bacter) by being oxidized to nitrate nitrogen (NO ₃ -N).

NH ₄ −N ← → NO ₂ −N ← → NO ₃ −N (1) During the above operation, the DO meter 2 arranged in the reaction tank 1
1 measures the dissolved oxygen concentration of raw water and
The redox potential of the raw water is measured by the RP meter 22.
Then, a controller (not shown) as a control means calculates the amount of excess sludge drawn out, controls the operation of the excess sludge drawing pump 16, and controls the operation of the blower 3 to keep the DO at or above the set value. Furthermore, the supernatant liquid is discharged by the supernatant liquid discharge pump 15.

In this embodiment, a predetermined amount of the activated sludge mixed liquid is drawn out during aeration once a day, so that the sludge retention time (SRT) of the embodiment 1
The sample was acclimated to have 3.6 days, SRT 9 days as Comparative Example 1 and SRT 5.6 days as Comparative Example 2.

Then, the above-mentioned three kinds of samples were used to sample and analyze the mixed solution once a week to analyze the nitrogen in the treated water.

On the other hand, the redox potential value in the anaerobic state (anaerobic O
RP) and the redox potential in the precipitated state (treated water ORP) were measured, and the difference in ORP, which was the difference, was calculated. Table 1 shows the results of the acclimation for about one month.

[0019]

[Table 1]

According to Table 1, the amount of change in ORP gradually increases from 311 mv to 398 mv in the embodiment,
Along with that, the TN (total nitrogen) removal rate is also increasing.
On the other hand, in Comparative Examples 1 and 2, the amount of change in ORP is 30.
At the first half of 0 mv, there was no further increase and the TN removal rate remained at 40%.

FIG. 2 shows the amount of change in ORP and T- in this embodiment.
It is a correlation diagram with N removal rate. According to the figure, it was confirmed that as the amount of change in ORP increased, the removal rate of TN also increased. Therefore, the TN removal state of the treated water can be grasped by observing the ORP value in the anaerobic state and the change amount of the ORP at the time of precipitation. When the removal rate of TN is increased, the aeration time, the air flow rate, and the denitrification time in that cycle are almost optimal, so that it is possible to shorten these times for operation.

Therefore, from the start of acclimation, the ORP value in the anaerobic state and the ORP value in the precipitated state are measured and the amount of change is calculated,
If the amount of change is 350 mv or less, it is assumed that nitrification is insufficient, and the amount of air blown from the blower 3 is increased to increase the activity of nitrifying bacteria, or the amount of excess sludge withdrawn is decreased to increase the SRT. As a result, nitrification is promoted by increasing nitrifying bacteria. In addition, the change amount is 35
If it is 0 mv or more, nitrification is sufficiently performed and the TN removal rate is also increased, and it is considered that the treatment is stable, and the aeration time and denitrification time are shortened, and the total cycle time is shortened accordingly. can do.

Therefore, according to the method of the present invention, the nitrification and stability of the treated water can be judged from the amount of change in ORP, and an appropriate operation method of the reaction tank 1 can be set based on these judgment results. Is possible.

[0024]

As described above in detail, according to the operation control method for batch type activated sludge treatment according to the present invention, by denitrifying waste water in an anaerobic state and then performing aeration, the action of microorganisms can be improved. Based on the decomposition and nitrification of organic substances, the oxidation-reduction potential of the wastewater is measured by the oxidation-reduction potentiometer at this time, and in particular, the oxidation-reduction potential value in the anaerobic state and the oxidation-reduction potential in the aerobic state are measured. It becomes possible to understand the TN removal state of the treated water from the correlation diagram between the change amount which is the difference and the total nitrogen (TN) removal rate, and the desorption which is a factor that influences the operating state of the reaction tank. It is possible to control the nitriding time, the aeration time, and the air flow rate to the optimum states.

Therefore, it becomes possible to easily obtain data relating to the factors that affect the operating state of the reaction tank, and based on this data, when the nitrification of waste water is insufficient, the air flow rate is increased or excess sludge is drawn out. If the amount is reduced to promote nitrification, and if nitrification is performed sufficiently, it can be considered that the treatment is stable and the aeration time and denitrification time can be shortened to shorten the total cycle time. As a result, efficient and economical operation of the reaction tank can be maintained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic embodiment of the present invention.

FIG. 2 is a correlation diagram between the ORP change amount and the TN removal rate in the present embodiment.

[Explanation of symbols]

 1 ... Biological reaction tank 2 ... Constant temperature tank 3 ... Blower 4 ... Air diffuser 7 ... Raw water adjusting tank 11 ... Stock solution 12 ... Tap water 13 ... Stock solution pump 14 ... Water pump 15 ... Supernatant discharge pump 16 ... Excess sludge extraction Pump 20 ... pH meter 21 ... Dissolved oxygen concentration meter (DO meter) 22 ... Redox potential meter (ORP meter)

Claims (2)

[Claims] 1. A wastewater flowing into a single reaction tank equipped with a pH meter and a dissolved oxygen concentration meter is subjected to denitrification under anaerobic conditions and nitrification by nitrifying bacteria under aerobic conditions by feeding air. In a batch type activated sludge treatment device in which the supernatant liquid of the reaction tank and sludge as a precipitate are pulled out by a pump, an oxidation-reduction potentiometer is provided in the reaction tank to obtain an anaerobic state during acclimation. And a nitrification state of treated water are determined by measuring the difference between the redox potentials in aerobic and aerobic conditions, and the batch type characterized by controlling the factors that affect the operating state of the reaction vessel from the results of this determination. Operation control method for activated sludge treatment. 2. The operation control method for batch activated sludge treatment according to claim 1, wherein the factors that affect the operation state of the reaction tank are denitrification time, aeration time, air feed amount and sludge withdrawal amount. .