JPS60122099A - Method for controlling biological nitrification process - Google Patents

Abstract

PURPOSE:To enable always stable nitrification by determining the difference in carbon dioxide concn. and the difference in oxygen concn. between the waste aeration gas and air in the rear stage part of an aeration treatment and controlling the nitrifying capacity per unit concn. of nitrifying bacteria. CONSTITUTION:The pH in an aeration tank 5 is measured by a pH meter and an alkali feed pump 16 is driven by the signal from a control panel 13 so as to attain the pH of the intended value in the case of controlling the pH. Alkalinity decreases on progression of nitrification and eventually a decrease in the pH is resulted and therefore the feeding of the alkali has also the purpose to make up the decreased pH. DO is measured by a DO meter 15 and the air discharge of an aeration blower 4 is controlled by the signal from the control panel 13 so as to attain the DO of the intended value in the case of controlling the DO. The sludge age is controlled by increasing or decreasing the discharge of an excess sludge pump 8 by the signal from the control panel 13.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to a method for biologically purifying wastewater containing dissolved nitrogen compounds such as sewage, human waste, and other industrial wastewater, and in particular to a method for biologically purifying wastewater containing dissolved nitrogen compounds, such as sewage, human waste, and other industrial wastewater. The present invention relates to a method for controlling a biological nitrification method of wastewater, in which dissolved nitrogen compounds are oxidized to oxidized nitrogen (hereinafter referred to as NOx-N) using nitrogen.

[Prior art and its problems]

In recent years, eutrophication of lakes and red tide in ocean trenches have become a problem, and for this reason, in the treatment of sewage and human waste, in addition to the conventional treatment of organic matter and suspended matter in wastewater, it is necessary to remove nitrogen compounds and phosphorus compounds. Removal of such nutrient salts V has become an important issue. Among these methods, biological removal methods, ammonia stripping methods, ion exchange methods, etc. are known as methods for removing nitrogen compounds, but biological removal methods are currently considered to be the most promising and are gradually becoming more popular. It is being put into practical use.

This biological removal method removes ammonia nitrogen (hereinafter referred to as N) (4-N) from wastewater by the action of nitrifying bacteria.
The nitrification process that oxidizes to N and the NO produced by this process
It is a denitrification method consisting of a denitrification process in which x-N is reduced to nitrogen gas by the action of denitrifying bacteria, and specifically, it is incorporated into treatment processes such as activated sludge method, fluidized bed method, and single rotating disk method. In particular, denitrification using the activated sludge method is considered to be the mainstream denitrification method in the future.

As mentioned above, the biological denitrification method consists of two steps: nitrification and denitrification. Therefore, in order to perform denitrification well, it is necessary to perform the nitrification in the first stage reliably. Conventionally, in denitrification using activated sludge method, the method for this purpose is to reduce the pH of the aeration tank to 1.
After controlling the dissolved oxygen concentration (hereinafter referred to as DO) to a constant value, the sludge age is controlled according to the water temperature, and the pH, DO, and activated sludge in the tank are checked while checking the water quality in the aeration tank. Methods have been used to control the amount. Also, attempts have been made to measure the nitrification rate of activated sludge in the tank and use this value for control.

The outline of the method of controlling the sludge age according to the water temperature after controlling the pH and DO of the aeration tank to a constant value is as follows: When nitrification is performed using nitrifying bacteria mixed in activated sludge, the conditions for maintaining the nitrifying bacteria in the aeration tank are as follows: It is generally well known that the growth rate is greater than or equal to the reciprocal of μ (1/μ). Since the specific growth rate of Nitrosomonas, a typical nitrifying bacterium, at a certain pH and DO is already known, using this value it is possible to determine the minimum necessary sludge age. In reality, if the sludge daily period is controlled to be a little longer than the calculated sludge daily period with allowances in mind, stable 4-day production is possible.

Control of the sludge age is usually performed by controlling the amount of excess sludge extracted. However, this method had various problems. For example, even if the pH2DO of the aeration tank is controlled constant, all parts of the aeration tank actually reach the target pH, D
It doesn't mean it's o.

Therefore, it has been difficult to accurately determine the specific growth rate μ of Nitrosomonas, which varies greatly depending on pH and Do.

Therefore, in order to ensure reliable nitrification, it is necessary to set a sludge age that is considerably larger than the calculated sludge age in order to provide some margin, and this will lead to an increase in the activated sludge concentration. This resulted in an increase in power and a deterioration in water quality. Furthermore, in order to grasp the sludge age, it is necessary to frequently measure the activated sludge concentration in the aeration tank and the amount of excess sludge extracted, and this work is also complicated.

Next, there is a method of controlling the amount of sludge in the aeration tank while checking the water quality in the tank. ，
-N concentration, NOx -N concentration changes are monitored, and Nk■, -N almost disappears near the outlet of the tank. 4: A method to adjust the nitrification rate of sea urchin, specifically 1) Il, ,
I:) 0, adjust the excess sludge extraction song. However, this method also has N ) i4-N concentration, N0x-N
There was no process analyzer available to accurately and continuously measure the concentration. V'), Ht,'l has the disadvantage of having to rely on expensive human labor for many analyses, and also
i(,DO,excess sludge removal fi'r,"71 (/,)
The problem was that adjustments had to be made manually based on the analysis results.

Furthermore, in an attempt to measure the nitrification rate of activated sludge in the tank and use this value for control, for example, the consumption rate of oxygen (hereinafter referred to as 0) and carbon dioxide (hereinafter referred to as CO7) in the aeration tank is The nitrification rate is measured from the difference in the production rate, and this value is compared with the nitrification rate required for complete nitrification, which has been calculated in advance.If the measured value of the nitrification rate is small, a certain pH, DO A method has been proposed for controlling nitrification by reducing the amount of excess sludge extracted and increasing the amount of activated sludge in the aeration tank, and vice versa.

However, in this method, the nitrification rate is calculated by calculating the mass balance from the 0° concentration in the aerated exhaust gas, the CO2 concentration, and the exhaust gas flow rate, so in principle, all the exhaust gas is collected and mixed, and the average
It is necessary to measure the CO2 concentration and the CO2 concentration, which is extremely impractical in the sense that the entire aeration tank must be sealed with a cover. In addition, in this method, the required nitrification rate is calculated in advance, but this is based on the assumption that the desired nitrogen load in the aeration tank is constant. Since that assumption does not hold, this control method cannot be applied, which is a very big drawback.

[Purpose of the invention]

The present invention solves the problems of these conventional methods at once, and enables stable nitrification at all times by accurately grasping the nitrification situation in the aeration tank and controlling the activity or concentration of nitrifying bacteria according to the situation. The purpose of this invention is to provide a method for controlling the biological nitrification process using the activated sludge method.

[Key points of the invention]

The present invention aims to reduce the CO2 concentration in the aeration exhaust gas near the outlet of the aeration tank to 0 in the biological nitrification process using the activated sludge method.
．． The concentration was analyzed using the CO2 concentration and 02 concentration in the air as standards, and the difference in carbon dioxide concentration (hereinafter referred to as ΔCO2) and the difference in oxygen concentration (hereinafter referred to as Δ0□) were calculated. Alternatively, the difference is calculated, the nitrification situation in the aeration tank is determined from the calculation result, and the pH and D in the aeration tank are determined based on the determination result.

By controlling the activity of nitrifying bacteria, that is, the nitrifying ability per unit concentration of nitrifying bacteria, or by controlling the amount of excess sludge extracted and changing the concentration of nitrifying bacteria, stable nitrification can be achieved at all times. This is what we are trying to achieve.

[Embodiments of the invention]

The principle of the present invention will now be explained in detail. In general, in nitrification using the activated sludge method, BOD oxidizing bacteria, which constitute the main body of activated sludge, oxidize and remove BOD components in wastewater in an aeration tank, and nitrifying bacteria oxidize N1 (4-H to NOx-N, i.e. Nitrification is proceeding at the same time.The stoichiometric equations for these reactions are as follows.

First, regarding BOD oxidation prisoners, the oxidation of organic matter, the BOD
Regarding the synthesis of the cellular substance of the oxidizing bacteria itself, and the oxidation of the intracellular substances (hereinafter referred to as cellular substances) of the BOD oxidizing bacteria themselves (also referred to as endogenous respiration), the following formulas (1),
(2) and (3) hold true.

Cx Hy Oz + 02-+ C02+H20(I
ICz Hy Oz + NH3+ 02 → (Cellular matter 'i&) + CO, +H20 (21 (Cellular matter) +02 →
CO2 + 1120 ten NH3 (3) The important thing here is:
0. The ratio of CO2 consumption to CO2 production, that is, the respiratory quotient, is 1, and this has been experimentally confirmed.

Next, the nitrification of N144-N by nitrifying bacteria causes Ni44
+ 1.502υ4) i f) 21ke+H20+NO2-
+4) NO, -+0.50x Omenyamabu>NO, -(5)
Kinari, total N H4-+ 202-Chi No, -+211++H20
(6) Good luck.

N)i in the formulas +4) and +6) indicates the type of nitrifying bacteria in which the Nl-muN contained in the wastewater and the organic nitrogen in the wastewater are treated by BOD oxidizing bacteria.

When nitrifying bacteria utilizes the energy of these oxidation reactions, they are expressed by the following formulas (7) and (8), respectively.

15C02+13NIN4+-+1ONO2++, 3F
4jS,N,02. +231('+41-40 (ka5
c02 +H)I,'+ICN07--14,0-+1
ONOs-+C5117NQ! +H'' (8) is Trobacter) Therefore, by combining both equations (8), the following equation (9) is obtained as a whole.

20C02+ x4NHJ'→4C, Ii NO6+1O
On the other hand, the production coefficient of nitrifying bacteria has been determined experimentally, and NH
, -NIg, 0.04-0.1:l of Nitrosomonas is produced, and nitrite nitrogen (hereinafter N02-N
0.02 to 007 g of nitro butter is added for 11 oxidation. These values indicate the oxidation reaction (4)
, (5) and (6), proliferative response (7), (
This shows that the proportions of 81 and (9) are very small, and by combining equations (6) and (9) in consideration of these production coefficients, the following equation (10
) is obtained.

Nl(+ 1.8302+ 0.1c02→0.021
By the way, in the normal biological nitrification method, the No. of NH4-H is
, -N is the so-called rate-determining step, so NH4
-N is mostly nitrate nitrogen (hereinafter referred to as No, -N)
Therefore, the following discussion uses 200).

Using the above reaction, ΔCO2゜Δ0 of aeration exhaust gas
The fact that the state of nitrification can be determined based on 2 is explained next using FIG. 1.

, In the following diagrams X, the same reference numerals indicate the same or corresponding parts.

Figure i'01 shows an aeration tank 5 for the activated sludge method, an aeration blower 4 that sends air to the aeration tank 5, an exhaust gas collector 1 that collects part of the aeration exhaust gas, and a system that measures the CO concentration in the exhaust gas. , compared with the CO6 concentration in the air, ΔC (J2 is included in the carbon dioxide concentration B12, and the O7a degree in the exhaust gas is similarly measured and the O
6 Oxygen cf that subtracts Δ02 from the concentration! FIG. 3 is a schematic diagram of aeration exhaust gas analysis using a temperature meter 3.

This situation! First, consider the case where nitrification has not progressed in the lower part of the exhaust gas collector 1 in a river. Exhaust waste collector 1
is installed near the outlet of the aeration tank 5, so in this case, the activated sludge in the lower part of the exhaust gas collector 1 may be considered to be undergoing endogenous respiration.

Therefore, the reaction is expressed by equation (3), in which O7 in the aerated air is consumed and CO7 is produced. If we consider the material balance with respect to o, co, in the shaded area in FIG. 1, that is, in the lower part of the exhaust gas collector 1, it will be as follows.

That is, for 02, the following formula (11) holds true.

ΔO, −F=Rr−X−4−Q(DouT−Do, N
) (11) where F is airflow-i% Rlr is the respiration rate of activated sludge.

In other words, 02 consumption rate, X is activated sludge company, Q is activated sludge flow passing through the shaded area, DO, N, DOo. A is 1) 0 of activated sludge flowing in and flowing out, respectively. Since Do is relatively stable near the outlet of the aeration tank 5, DOot,
Assuming that T=DO8N, the following equation (12) can be obtained from equation (11).

Δ0. =(X/F)-Rr (12) Equation (12) shows that Δ02 is proportional to the respiration rate of activated sludge.

On the other hand, the following formula (13) also holds true for C02.

Δco,・F2 (co, generation rate) X +Q (”O
t ot+r-6%) “Here C02□N # CO
2otl? respectively flow into the shaded areas.

This is the dissolved CO2 concentration of activated sludge flowing out. (Aeration tank 5
If the pH is stable near the outlet of the activated sludge, the CO in the activated sludge will
2 concentration is a saturation concentration that roughly corresponds to the CO2 concentration in the air, and is relatively stable, so CO,. L+1
=0021N, the following equation (14) can be obtained from equation (13).

ΔCQ2= (X/F) (Co, production rate') (
14) Since it is known from equation (3) that the 02 consumption rate and the CO2 production rate of activated sludge are equal, the following relationship is derived: These equations (15) and (16) show the basic relationship between ΔCO7 and Δ02 when nitrification is not progressing.

Next, regarding the reaction where nitrification is progressing at the bottom of the exhaust gas collector 1, the endogenous respiration of activated sludge and nitrification progress simultaneously, so the reaction is expressed by equations (3) and (1), formula(
In 3), 02 is consumed and CO, is generated, and the equation (1
0), both O2 and CO2 will be consumed.

Here, we will examine their quantitative relationship based on the respiration rate of activated sludge.

When sewage, which is a typical wastewater, is treated by the activated sludge method Lq, the O3 consumption rate (endogenous respiration rate) of activated sludge in an endogenous respiration state is 2 to 8 m9/j9 ·ML88'-hr, that is, 0. 06~0.25mmo7/,! 9-MLS'
It is well known that S-hr. On the other hand, the 02 consumption rate (respiration rate during nitrification) of activated sludge undergoing nitrification under endogenous respiration is 10 to 30 mg/g・MLS.
S-hrl i.e. 0.31-0.94 mmol/j
Tails was told it was i-MLSS-hr.

Therefore, the endogenous respiration rate e O, 12 mmoI! /, 9-M
LSS-hr.

Respiration rate during nitrification 0.63 mmol/g・MLss-hr
Assume that activated sludge exhibits

Considering CO2, CO2 caused by formula (3)
The production rate is equal to the endogenous respiration rate and is 0.12 m
mol/17-MLSS-hr. Next, equation (10)
In order to calculate this value, we focus on the respiration rate of activated sludge during nitrification. The respiration rate during nitrification is Q, 53 rnmol! /gIVLSS-hr, but endogenous respiration is 0.12 mmol/ji-MLss
-hr is included, so the respiration rate for nitrification alone is 0.51 mmol/g・MLSS -hr
It is. This value corresponds to 0, consumption, in equation (10). Therefore, from this relationship, the CO2 consumption rate 0.
028 mmol/g・ML8B4r is obtained. As a result, the CO2 production rate of activated sludge during nitrification based on equations (3) and (10) is 0.12-0.028
:0.09 mmol! /, 9-MLSS-hr.

In this case as well, the same relationships as in equations (12) and (14) hold, so the following equations (17) and (18) are derived.

Δ02/ΔCo2=0.6310.0! ] >> 1 (1
, 7) or Δ02−ΔCo2e O(], 8) ΔC02 and Δ shown in equations (17) and (18)
The relationship of 02 is the equation (15) shown in the above-mentioned case where nitrification is not progressing.

(This is completely different from the relationship in 1. Therefore, by comparing ΔC02 and ΔO3 of the aerated exhaust gas from the above results, it can be determined whether nitrification is progressing or not.

The following explanation was made using equation (10) on the assumption that nitrification progresses to No. -N, but even when nitrification reaches No.2-N, that is, when the nitrification ratio is 1 to nitrous, Using a similar concept, it is possible to determine whether nitrification is progressing or not.

A wastewater treatment system as an embodiment of the present invention based on the above principle will be explained next with reference to FIGS. 2 and 3.

FIG. 2 shows a specific device for carrying out the biological nitrification process control method according to the present invention, including an aeration tank 5 into which wastewater 10 to be treated flows, and an aeration tank 5 in which sludge is precipitated from the aerated wastewater. Sedimentation tank 1 that separates and flows out as treated water 12
1. Aeration blower 4 for sending air to the aeration tank 5, DO meter 15 for measuring I)O in the aeration tank 5, sludge (return sludge 7)
), an excess sludge pump 8 for extracting excess sludge 9, an exhaust gas collector 1 for collecting aeration waste, and an exhaust gas collector 1 for collecting CO2, 0 and 9 degrees in the exhaust gas. , a carbon dioxide concentration meter 2 that measures Δ02, an oxygen concentration meter 3, a pH meter 14 for controlling the pH in the aeration tank 5, an alkali injection pump 16, and an alkali storage tank 1.
7, a control panel 13 that controls the entire wastewater treatment system. In this embodiment, the wastewater 10 containing nitrogen compounds such as NH4-N or organic nitrogen and organic pollutants flows into the aeration tank 5, and the biodegradable organic matter contained in the wastewater tank 0 flows into the aeration tank 5. In No. 5, N1-14-N contained in wastewater 10 and NH, - converted from organic nitrogen by the action of BOD oxidizing bacteria, were decomposed and removed by the action of BOD oxidizing bacteria, which accounted for most of the activated sludge. 'N
is also oxidized to NOx-N in the aeration tank 5 by the action of nitrifying bacteria mixed in the activated sludge. Next1cNOx
The activated sludge containing -N flows into the settling tank 11, where the sludge is separated by gravity settling and the treated water system 2 is obtained.

Most of the separated sludge is returned to the aeration tank 5 as return sludge 7 by the return sludge pump 6, but a part of it is removed from the system as surplus sludge 9 via the surplus sludge pump 8.

Nitrification is controlled as follows. Nitrification can be controlled by a method of controlling the activity of nitrifying bacteria and a method of controlling the concentration of nitrifying bacteria in activated sludge, and control is usually achieved by a combination of these two methods. Control of the activity of nitrifying bacteria is specifically achieved by controlling the pIl and Do temperatures. For example, for pH, N1-1. The activity of Nitrosomonas to oxidize -N to NO and -N reaches its maximum at around pa 8.5, and the pH
This method takes advantage of the fact that the activity of pt-I decreases when the temperature is higher or lower, and it is generally used to save alkali.
It is controlled at about 6.5 to 7.8. Regarding Do, we use the fact that the active force of Nitrosomonas SDo concentration is set at 2η/1 and does not change above that level, but decreases below that level, and usually 1 to 2
control so that mq/l. Furthermore, the activity of Nitrosomo and eggplant is inhibited at temperatures above 40°C, but below that temperature, the activity increases as the temperature rises, and the activity can be changed by changing the temperature. However, in regular wastewater treatment, changing the temperature of wastewater requires a huge amount of energy cost, so except for one special case, the temperature side (
goods) will not be carried out.

On the other hand, the concentration of nitrifying bacteria is determined by controlling the sludge age. This is based on the fact that when the amount of nitrogen flowing into the aeration i5 on -day is approximately the same, the concentration of nitrifying bacteria increases as the sludge age increases.

Devices for these controls will be explained using the embodiment shown in FIG. The alkali injection pump 16 is driven by the signal. Note that the injection of alkali also has the purpose of compensating for the consumption of the 7-gamma Luca IJ 11, which is undergoing nitrification, and the alkalinity of the activated sludge in the aeration tank 5 is reduced, resulting in a decrease in pH. Regarding Do, measure 1) 0 with Do total 15, and DO
The air discharge amount of the aeration blower 4 is adjusted according to a signal from the control panel 13 until the target value t is achieved. The sludge daily date is controlled by increasing or decreasing the discharge amount of the excess sludge pump 8 using a signal from the control panel 13.

Next, the UK1 method will be explained in detail. In the present invention, the state of nitrification is determined by analyzing the exhaust gas.

The exhaust gas collector 1 is installed relatively close to the outlet of the aeration tank 5, and continuously analyzes the exhaust gas to determine ΔCO2 and Δ0.
Get 2. This analysis value is sent to the control panel 13, where Δ
The quotient and difference between CO2 and ΔO1 are calculated.

Since the device shown in this example is for nitrification, as long as nitrifying bacteria exist in the aeration tank 5, nitrification will naturally occur (it is possible to easily confirm this by water quality analysis). ), the calculation result is Δ02/ΔCO, middle 1 or Δ0
．． -ΔCo2=I=Q, and we will consider four more cases in which it is determined that "nitrification is not progressing." In addition, pH, Do
It is assumed that PL-1,7 and DO1 were controlled at 1m9/l. In that case, this judgment is that if the nitrification is being carried out normally, the nitrification is completed on the mainstream surface rather than at a certain position where the exhaust gas collector 1 is installed, and directly below the exhaust gas collector 1, Iflj, q. 'q (means not y).

Next, the meaning of this and the control method 1 will be explained in more detail with reference to FIG. FIG. 3 schematically shows the change in N1-14-N9 degrees in the aeration tank 5 in the actual sister example shown in FIG. The gas collector 1 is installed above point b. Therefore, if nitrification is completed upstream of point b, for example at point 0, it is determined that "nitrification is not progressing." If this judgment continues for the same period, the nitrification capacity is excessive compared to the amount of nitrogen inflow. In this case, pH, D
Leave O as it is, control the sludge period, reduce the concentration of nitrifying bacteria by 10-1, and adjust the nitrification by 1M.

Specifically, the discharge amount of the excess sludge pump 8 is increased by 1.5 of the opening side plate 3 to increase the amount of excess sludge 9 to be extracted. If you pull it that way, the amount of activated sludge in 5 decreases and nitrification fit: The force decreases, so the point where nitrification is completed shifts to the exit flllll, and if ff1l, it moves to point b. do. Since there is a waste extractor 1 on point b, at this point the control panel 13 (51ΔCo2.Δ02
) - From the results, it is determined that nitrification is progressing.

Therefore, now (g5 does not increase the nitrification capacity), the discharge of the 4z size sludge pump 8: lowers the fall, and the excess sludge i +'-, 9 extraction 1 □ 1 is chanted. As a result, nitrification', 11
1I (point becomes 0 point, +1g q s 1. In other words, the nitrification completion point goes back and forth between 1) point and 0 point, so nitrification is stable and 1f (goes, R is well controlled. It is.

By the way, such control is effective for the amount of water flowing into the aeration tank 5.
It is effective when the number of 74 peaks is not very large, or when the variable 1 pattern is repeated in almost the same shape even if it fluctuates. This is because, of course, when the nitrogen load does not change, but even when the nitrogen load fluctuates, if the fluctuation pattern is almost the same, the nitrification completion point in the aeration tank 5 is determined at the point when the nitrogen load is highest at b - control between c points ω11
1- It's good.

In wastewater treatment along the street, the amount of inflow is relatively stable as mentioned above, or the same change/bυ pattern is repeated.However, for example, the amount of inflow suddenly increases at Nakazuke. In fact, there may be cases where this occurs.Next, the eleventh control method for such cases will be explained.

In this case, it is not enough to control the concentration of nitrifying bacteria by reducing the amount of time required to extract the excess sludge 9. Since the concentration of nitrifying bacteria changes relatively slowly, 1. If the nitrogen load suddenly increases, it cannot be followed. As a countermeasure to this problem, an effective method is to increase the activity of nitrifying bacteria.

For example, if you are operating at pLI7, Do l m]/l, and the signal J indicating that nitrification is progressing is displayed, but this signal does not disappear even if you reduce the amount of excess sludge 9 to be extracted. Suppose. In such a case, p)-1,DO
Change the settings for pl, i 7.5.

1) 02ml? //'c! = do. Then, even though the concentration does not change much, the activity of nitrifying bacteria increases rapidly, allowing it to perform nitrification at high speed and cope with the sudden increase in nitrogen load. Specifically, the pH is measured with the pi-meter 14, the alkali injection pump J6 is moved based on the signal from the control panel 13 so that the pH reaches the set value, and the DO is measured with the DO meter 15. (2) The air discharge amount of the aeration blower 4 is controlled by the signal from the ridge 1 board 13 so that 0 becomes the set value.

Once a signal indicating that nitrification is not progressing is obtained, the sudden increase in the nitrification load is often temporary, so the p
Gradually lower the set value of l(,l)0 until the predetermined value p
l-T 7 , 1) Just return it to 01 m9/l. Thus, even when the nitrogen load increases rapidly, good nitrification can be maintained by controlling the activity of nitrifying bacteria.

〔Effect of the invention〕

As described above, in the present invention, in biological nitrification using the activated sludge method, an exhaust sludge collector is installed at the exit 11 of the aeration tank, and the CO2 concentration in the aeration exhaust gas, 02 concentration 1 yen, is Analyze the CO2 Vek l 02 concentration in the aeration tank as a reference, calculate the quotient or difference of each concentration difference after determining ΔC02 and Δ02, and determine the nitrification status in the aeration tank from the calculation result, Since the concentration or activity of nitrifying bacteria is controlled depending on the situation, stable nitrification is always possible. In addition, since the nitrification situation within the premises can be accurately controlled, there is no need to worry about increasing the nitrification capacity excessively in anticipation of a margin, and an appropriate activated sludge concentration can be maintained, which is different from the conventional nitrification system. Compared to the wholesale method, it reduces aeration power and improves the quality of treated water.

Furthermore, the 1H1] control method according to the present invention can be easily applied to existing activated sludge treatment equipment, since it is possible to perform total DLL control (installation deviation of several devices) without adding Inuki II modification to a general activated sludge treatment equipment. It can be introduced to

The control method according to the present invention can be applied to the control 11 of nitrification by activated sludge method of water containing N114-N, especially sewage, human waste, RLK & wastewater, and garbage leachate.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of aeration exhaust gas analysis for detailed explanation of the present invention, Fig. 2 is a flow sheet showing a specific example of the wastewater treatment system of the present invention, and Fig. 3 is the same as Fig. 2. , is a schematic diagram showing an increase in the concentration of NH, -N in the aeration tank. 1 Exhaust sludge collector, 2-- = carbon oxide to a1.3 oxygen concentration meter, 4 Aeration blower, 5 (Aeration tank, 8. Sludge pump, 9. Excess sludge, 10. Waste water, 13-? t
ill also ((1 disc, l 4,, pT (total, 15.
■) O'1 (10 Fig. 1

Claims (1)

[Claims] 1) In the biological nitrification process of wastewater using the activated sludge method, which oxidizes ammonia nitrogen and organic nitrogen in wastewater to nitrite nitrogen or nitrate nitrogen, carbon dioxide in the aeration exhaust gas in the latter stage of the aeration treatment process Calculate the quotient or difference of each concentration difference based on the difference between carbon dioxide concentration, oxygen concentration, and carbon dioxide concentration and oxygen concentration in the air. A method for controlling a biological nitrification process, which comprises controlling the concentration of nitrifying bacteria in an aeration tank or the nitrifying ability per unit concentration of nitrifying bacteria.