JPH06206093A - Method and device for accelerating nitrification for treatment with anaerobic-aerobic activated sludge - Google Patents

Abstract

PURPOSE:To provide method and device for accelerating nitrification for treatment with anaerobic-aerobic activated sludge to improve the nitrification efficiency of an aerobic tank and thereby enhance the denitrification efficiency of an anaerobic tank. CONSTITUTION:The method and device for accelerating nitrification for treatment with the anaerobic-aerobic activated sludge features the treating process of enhancing the nitrification efficiency of an aerobic tank in a manner wherein the alkalinity and ammonia concn. of the waste liquors are measured by an alkalinity meter 12 and an ammonia concn. meter 13 respectively in an aerobic tank 2a, the alkaline component required for the nitrification is obtained by the computation of a controller 14 made from the measured values and the alkaline component is introduced from a tank 15 into the aerobic tank 2a by a fluid pump 16 serving as a pouring means to make up for a lack of the alkaline component. Sodium hydrogencarbonate (NaHCO3) is used as the alkaline component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrification accelerating method and device for highly efficiently removing organic matter and nitrogen in wastewater using an anaerobic-aerobic activated sludge treatment device.

[0002]

2. Description of the Related Art Various methods have conventionally been proposed for efficiently removing organic matter in wastewater such as sewage and removing nitrogen and phosphorus which are considered to be the causative agents of eutrophication in closed water areas. . This eutrophication refers to an increase in the concentration of nutrient salts such as N and P in the water area, which activates biological activities using these nutrients as nutrients and changes the ecosystem. In particular, it is known that the above-mentioned eutrophication rapidly progresses when a large amount of domestic wastewater or industrial wastewater flows into lakes and the like.

Recently, it has been required to increase the removal rate of nitrogen, and it is expected that the regulations on nitrogen will be stricter. Therefore, the number of facilities adopting an advanced treatment process capable of removing this will increase. it is conceivable that.

Although physicochemical methods and biological methods have been proposed as means for removing nitrogen and phosphorus in wastewater, physicochemical methods are not widely used because of the high cost. For example, a phosphorus removal method which has been put into practical use as a physicochemical method includes a coagulation precipitation method and a crystallization method, but this method has a drawback in terms of cost and maintenance.

On the other hand, as a biological biological method for simultaneously removing nitrogen and phosphorus, an anaerobic method is a modification of the conventional activated sludge method.
The aerobic activated sludge method is drawing attention. (See, for example, Water Pollution Research, Vol. 12, No. 7, 441-448, 1989.) This anaerobic-aerobic activated sludge method is, for example, as shown in FIG. (Abbreviated as DO)
Is divided into anaerobic tanks 1a and 1b in which no DO exists and aerobic tanks 2a, 2b and 2c in which DO exists, and the inflowing wastewater 3 is stirred by the stirring mechanism 10 under anoxic condition by the anaerobic tanks 1a and 1b. Denitrification by denitrifying bacteria in the activated sludge, and then by supplying air from the blower 5 to the air diffuser 4 arranged inside the aerobic tanks 2a, 2b, 2c, in the presence of oxygen by aeration. Oxidative decomposition of organic matter by activated sludge and nitrification of ammonia by nitrifying bacteria. Then, the nitrification solution in the last-stage aerobic tank 2c is sent to the anaerobic tank 1a by using the nitrification solution circulation pump 6, whereby the anaerobic tank 1a,
The denitrifying effect of 1b is promoted.

The above-mentioned denitrifying bacterium refers to a bacterium that reduces N0 ₂ -N and N0 ₃ -N to N ₂ and NO ₂ by respiration of nitric acid under anaerobic conditions. Also, phosphorus in wastewater is anaerobic tanks 1a, 1b.
It is released inside and is taken in and removed by the activated sludge in the aerobic tanks 2a, 2b and 2c. Reference numeral 7 denotes a final settling basin, and the supernatant of the final settling basin 7 is discharged after passing through a disinfecting tank not shown in the figure, and a part of the sludge settled in the final settling basin 7 is a sludge return pump. The other sludge is returned to the anaerobic tank 1a by 8 and the other sludge is sent from the excess sludge pump 9 to an excess sludge treatment device (not shown) for treatment.

By using such an anaerobic-aerobic activated sludge treatment device, an effect comparable to the organic substance removal effect achieved by the usual standard activated sludge method can be obtained, and nitrogen and phosphorus are more effective than the activated sludge method. A high removal rate is achieved.

[0008]

However, in such a conventional anaerobic-aerobic activated sludge treatment method, it is difficult to sufficiently enhance both the nitrification efficiency in the aerobic tank and the denitrification effect in the anaerobic tank. There was a problem of being there.

That is, the operation mode in the anaerobic-aerobic activated sludge method can be roughly classified into a denitrification reaction in the anaerobic tanks 1a and 1b and a nitrification reaction in the aerobic tanks 2a, 2b and 2c. The latter, that is, the nitrification reaction, is the rate-determining reaction.

In particular, in order to efficiently remove nitrogen by the anaerobic-aerobic activated sludge treatment method, it is required to maintain denitrification in the anaerobic tank and nitrification in the aerobic tank under optimum operating conditions. Since the nitrogen removal process is highly influenced by the nitrification process, it is necessary that the nitrification process is performed well in order to perform good nitrogen removal. This nitrification reaction is caused by nitrifying bacteria as described above,
It is known that the activity of this nitrifying bacterium is easily affected by subtle changes such as pH and water temperature.

Furthermore, the nitrification reaction itself has a lower reaction rate than the organic substance removal reaction, and a large reaction tank must be prepared to cover it, but a large site must be secured for that purpose. In particular, in an area where it is difficult to secure a land, such as an urban area, it is difficult to introduce an anaerobic-aerobic activated sludge treatment method and device in combination with a space problem.

Therefore, the present invention solves the problems of the anaerobic-aerobic activated sludge treatment, improves the nitrification efficiency in the aerobic tank, and accordingly enhances the denitrification effect in the anaerobic tank. It is an object of the present invention to provide a nitrification accelerating method and device for treating anaerobic-aerobic activated sludge, which can be obtained.

[0013]

In order to achieve the above object, the present invention performs a step of denitrifying wastewater such as sewage with denitrifying bacteria in an anaerobic tank, and nitrifying with nitrifying bacteria in an aerobic tank. In the anaerobic-aerobic activated sludge treatment, which comprises a step and a step of solid-liquid separating in a settling tank and discharging the supernatant as treated water,
Measure the alkalinity and ammonia concentration of the liquid with the alkalinity meter and ammonia concentration meter installed in the aerobic tank,
From this measurement result, the alkalinity component required for nitrification is calculated, and by injecting the insufficient alkalinity component into the aerobic tank, operation control is performed so as to increase the nitrification efficiency in the aerobic tank. A method and apparatus for promoting nitrification in the treatment of anaerobic-aerobic activated sludge. Further, sodium hydrogen carbonate is used as the alkalinity component.

[0014]

According to the method and apparatus for promoting nitrification, the wastewater is denitrified in the anaerobic tank, aeration is performed in the aerobic tank and nitrification based on the effects of nitrifying bacteria is performed, and the nitrification is set in the aerobic tank as an index. The alkalinity and ammonia concentration of the liquid are measured by the alkalinity meter and the ammonia concentration meter, the controller calculates the alkalinity component required for nitrification based on this measurement result, and based on this calculation result, the injection means can improve the The insufficient alkalinity component is supplied to the air tank.

As a result, the nitrification rate is prevented from lowering due to lack of alkalinity, the nitrification reaction in the aerobic tank is promoted, and the nitrogen removal rate in the anaerobic tank is improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The anaerobic of the present invention will be described below with reference to the drawings.
An embodiment of the method and apparatus for promoting nitrification in aerobic activated sludge treatment will be described in detail by assigning the same reference numerals to the same components as the conventional components. In the schematic diagram shown in FIG. 1, 1
a, 1b are anaerobic tanks for denitrifying wastewater, 2a, 2
b and 2c are aerobic tanks for performing nitrification, and the anaerobic tanks 1a and 1b and the aerobic tanks 2a, 2b and 2c are formed by partitioning the same biological reaction tank with a partition plate 11. Anaerobic tank 1
Stirring mechanisms 10 and 10 are arranged inside a and 1b. Further, air diffusers 4, 4, 4 as air blowing members are arranged at the bottoms of the aerobic tanks 2a, 2b, 2c, and a blower 5 for supplying air is provided outside.

6 is a nitrification solution circulation pump for feeding the nitrification solution from the aerobic tank 2c to the anaerobic tank 1a, 7 is a final settling tank as a settling tank, and 8 is a part of the sludge settled in the final settling tank 7 The sludge return pumps 8 and 9 for returning to 1a are surplus sludge pumps.

In this embodiment, an alkali meter 12 and an ammonia concentration meter 13 are installed in the aerobic tank 2a of such an anaerobic-aerobic activated sludge treatment apparatus, and the alkali meter 1 is further installed.
2 and a controller 14 to which the measurement data of the ammonia concentration meter 13 is input. Reference numeral 15 is a tank filled with sodium hydrogencarbonate (NaHCO ₃ ) as an alkalinity component, and a predetermined amount of sodium hydrogencarbonate from the tank 15 is aerobic by the action of the fluid pump 16 operated by the control output from the controller 14. It is configured to be injected into the tank 2a.

The basic operation of the anaerobic-aerobic activated sludge treatment device is as follows. As shown in FIG. 1, first, the wastewater 3 as waste flows into the anaerobic tank 1a, based on the stirring action and the action of denitrifying bacteria stirring mechanism 10 in the water, NO ₃ -N, NO ₂ - Reduction of N ions to N ₂ , that is, denitrification, is performed. Next, the wastewater flows into the aerobic tanks 2a, 2b, 2c, and aeration by aeration from the diffuser pipe 4 is performed as the blower 5 is driven. Based on the action of nitrifying bacteria, ammonia nitrogen NH ₄ -N NO ₂ -N or NO ₃ -
Oxidation to N, that is, nitrification is performed.

The nitrification solution in the aerobic tank 2c is sent to the anaerobic tank 1a by using the nitrification solution circulation pump 6 and is transferred to the anaerobic tank 1a,
The denitrifying effect of 1b is promoted. Anaerobic tank for phosphorus in wastewater 1
It is released in a and 1b and taken in and removed by activated sludge in aerobic tanks 2a, 2b and 2c. A part of the sludge settled in the final settling basin 7 is returned to the anaerobic tank 1a by the sludge return pump 8 and the other sludge is sent from the excess sludge pump 9 to an excess sludge treatment device (not shown) for treatment. . The supernatant of the final settling basin 7 is discharged after passing through a disinfecting tank (not shown).

In the present embodiment, while such anaerobic-aerobic activated sludge treatment is in progress, the alkalinity meter 12 and the ammonia concentration meter 13 installed in the aerobic tank 2a as indicators are used to measure the alkalinity of the liquid. And the ammonia concentration are measured, the controller 14 calculates the amount of sodium hydrogen carbonate required for nitrification based on the measurement result, and the fluid pump 16 as the injection means is driven based on the calculation result, and the tank Injecting a shortage of sodium hydrogen carbonate (NaHCO ₃ ) from 15 into the aerobic tank 2a is a major operational feature. This prevents the nitrification rate from decreasing due to lack of alkalinity, and the aerobic tanks 2a, 2
The nitrification reaction in b and 2c can be promoted, and the nitrogen removal rate in the anaerobic tanks 1a and 1b can be improved.

Theoretical explanation of this is as follows. That is, nitrifying bacteria that cause nitrification (Nitrosomonas, Nit
robacter) is an autotrophic bacterium, which is a bacterium that oxidizes ammonia or nitrite to nitric acid among bacteria having the ability of carbon assimilation. Oxidation is NH ₃ + 3O ₂ → HNO ₂ + H ₂ O ・ ・ ・ ・ ・ ・ ・ ・ (1) HNO ₂ +1/2 ・ O ₂ → HNO ₃・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2) It takes the form of (1) performed by Nitrosomonas and Nitrosococcus, and (2) performed by Nitrobacter.

Nitrifying bacteria acquire energy required for growth by oxidizing inorganic nitrogen compounds, and are used for cell synthesis of inorganic carbon. This can be expressed by the following reaction formula.

The ^{_{NH 4 + + 1.86O 2 + 1.98HCO}} 3 - → 0.021C 5 H 7 NO 2 + 1.041H 2 O + 0.98NO 3 - + 1.88H The ₂ CO ₃ ··· ₍₃₎ one of alkalinity , OH ⁻ , CO ₃ ²⁻ , HCO ₃ ^−, etc. are used as an example of a method of expressing how much an acid consuming component is contained, and a sample solution is usually brought to a constant pH which is an acid standard solution. Neutralization titration was performed up to, and the titration amount required at that time was converted into mg equivalent per 1 liter of the sample solution or equivalent mg of CaCO ₃ and expressed. There are many kinds of alkalinity depending on the pH up to which the neutralizing ability is expressed, but generally "pH 4.8 alkalinity" is treated as a measure of HCO ₃ ⁻ .

As shown in the equation (3), the reaction is stoichiometrically at a ratio of NH ₄ ⁺ : HCO ₃ ⁻ = 1: 1.98 ... (4) However, in reality, the reaction rate is small because biological reactions are involved.

In one embodiment of the invention, the "pH4.8 alkalinity" is HCO ₃ ^-
However, it also contains some CO ₃ ²⁻ , OH ^{− and the} like. Therefore, the main point of the present invention is to supply sodium hydrogen carbonate (NaHCO ₃ ) until NH ₄ ⁺ : HCO ₃ ⁻ = 1: 3.

Sodium hydrogencarbonate used as an alkalinity component is also called sodium bicarbonate or sodium bicarbonate, and is produced in large quantities as an intermediate product of sodium carbonate production by the ammonia soda method. Carbon dioxide is passed through a saturated aqueous solution to precipitate crystals, which is then filtered and dried in a stream of carbon dioxide to obtain crystals. Since it has sodium chloride and ammonium chloride as impurities, it is generated by recrystallization from an aqueous solution.

When heated, carbon dioxide and water are released to decompose and become anhydrous sodium carbonate at 270 ° C. or higher. The aqueous solution is slightly alkaline due to hydrolysis.

NaHCO ₃ + H ₂ O → H ₂ CO ₃ + NaOH (5) Therefore, by supplying sodium hydrogencarbonate (NaHCO ₃ ) to the aerobic tank 2a, the aerobic tanks 2a, 2b, Two
The lack of alkalinity in c is eliminated, and the nitrification reaction in the aerobic tank can be promoted as described above.

[0030]

As described in detail above, according to the method and apparatus for promoting nitrification in anaerobic-aerobic activated sludge treatment according to the present invention, denitrification in an anaerobic tank and aeration and nitrifying bacteria in an aerobic tank are performed. While nitrification is performed based on the action of, the alkalinity and ammonia concentration in the aerobic tank are measured, the controller calculates the alkalinity component required for nitrification based on the measurement results, and based on this calculation result Insufficient alkalinity component is supplied to the aerobic tank by the injection means, which prevents the decrease in nitrification rate due to lack of alkalinity and is the rate-determining reaction. Is promoted, and along with this, the nitrogen removal rate in the anaerobic tank can be improved.

Further, since it is not necessary to prepare a particularly large reaction tank for increasing the nitrification reaction rate and a large land is not required, anaerobic-aerobic activated sludge is required even in an area where it is difficult to secure a land such as an urban area. It has a great effect that a processing device can be introduced.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing a specific example of conventional anaerobic-aerobic activated sludge treatment.

[Explanation of symbols]

 1a, 1b ... Anaerobic tank 2a, 2b, 2c ... Aerobic tank 4 ... Diffuser pipe 5 ... Blower 6 ... Nitrification liquid circulation pump 7 ... Final sedimentation tank 8 ... Sludge return pump 9 ... Excess sludge pump 10 ... Stirring mechanism 12 ... Alkaline Degree meter 13 ... Ammonia concentration meter 14 ... Controller 15 ... (Alkalinity component) tank 16 ... Fluid pump

Claims (3)

[Claims] 1. A step of denitrifying wastewater such as sewage with denitrifying bacteria in an anaerobic tank, a step of nitrifying with nitrifying bacteria in an aerobic tank, and solid-liquid separation in a precipitation tank to treat a supernatant. In the anaerobic-aerobic activated sludge treatment including a step of discharging as water, the alkalinity and ammonia concentration of the liquid are measured by the alkalinity meter and the ammonia concentration meter installed in the aerobic tank,
From this measurement result, the alkalinity component required for nitrification is calculated, and the insufficient alkalinity component is injected into the aerobic tank to control the operation so as to increase the nitrification efficiency in the aerobic tank. A method for promoting nitrification in treating anaerobic-aerobic activated sludge, which is characterized. 2. The nitrification promoting method for anaerobic-aerobic activated sludge treatment according to claim 1, wherein the alkalinity component is sodium hydrogen carbonate. 3. An alkalinity meter and an ammonia concentration meter installed in an aerobic tank, and a controller for calculating an alkalinity component required for nitrification based on the measurement data of the alkalinity meter and the ammonia concentration meter. A nitrification accelerating device for anaerobic-aerobic activated sludge treatment, comprising: an injection means for supplying a lacking alkalinity component to the aerobic tank according to the control output of the controller.