JP2001314892A - Method for controlling denitrification apparatus of wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a denitrification apparatus of wastewater, capable of preventing the deterioration of denitrification capacity caused by the temporal fluctuations of water quality. SOLUTION: In the method for controlling the denitrification apparatus of wastewater by a biological denitrification treatment apparatus, the denitrification apparatus is equipped with a first sedimentation basin, a denitrification tank, a nitrification tank, a final sedimentation basin and an automatic analyser for measuring the total nitrogen concentration, ammonia nitrogen and chemical oxygen demand of the outlet water of the first sedimentation basin and organic matter is injected in the denitrification tank. The total nitrogen concentration, ammonia nitrogen and chemical oxygen demand of the outlet water of the first sedimentation basin are measured by the automatic analyser to obtain measured values and treatment estimate caliculation due to simulation constituted of a numerical value model is performed on the basis of the measured values in a short time and, when the deterioration of a nitrogen removing ratio is estimated, the injection amount of the organic matter is controlled on the basis of the simulation result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating wastewater such as sewage, and more particularly to a method for controlling nitrogen removal from wastewater such as sewage.

[0002]

2. Description of the Related Art Activated sludge process is known as a conventional representative treatment process for removing organic matter from wastewater, and biological treatment is used as a conventional method for simultaneously removing nitrogen compounds and organic matter. There is a nitrification denitrification method.

FIG. 5 shows an example of a wastewater treatment apparatus based on the biological nitrification and denitrification method. The illustrated wastewater treatment apparatus includes a settling basin 2, a nitrification tank 4 for oxidizing (nitrifying) nitrogen compounds in the wastewater to nitrate nitrogen or nitrite nitrogen, and a nitrate nitrogen or nitrite nitrogen gas. And a final settling basin 7.

The wastewater to be treated is first introduced into a sedimentation basin 2, where relatively large and heavy solids are removed.
Nitrogen in the wastewater is removed from the wastewater by reacting with the nitrification tank 4 and the denitrification tank 3 and finally being released into the atmosphere in the form of nitrogen gas. Organic matter in the wastewater is removed in both the denitrification tank 3 and the nitrification tank 4.

[0005] The following is known as a conventional technique relating to an operation control method of a wastewater treatment apparatus by a biological nitrification and denitrification method. For example, a method of measuring the concentration of dissolved oxygen in a nitrification tank and controlling the amount of air blown to the nitrification tank based on the measured value (Japanese Patent Laid-Open No. 7-80494), a method of controlling nitrite nitrogen in a denitrification tank and a nitrification tank A method of measuring the concentration and nitrate nitrogen concentration and controlling the volume ratio between the denitrification tank and the nitrification tank based on the measured values (Japanese Patent Application Laid-Open No. Hei 7-136687), and the COD of inflow water introduced into the denitrification tank A method of measuring the concentration and the concentration of ammonia nitrogen and controlling the injection amount of an organic substance such as methanol based on the measured values (JP-A-61-249597).

[0006]

In the removal of nitrogen from wastewater using a wastewater treatment apparatus by a biological nitrification and denitrification method, the wastewater treatment apparatus responds to the time variation of the quality of the wastewater flowing into the wastewater treatment apparatus. It is necessary to maintain and manage the processing performance well. For this purpose, the operating conditions of the wastewater treatment device must be controlled so as to have an appropriate value corresponding to the quality of the wastewater. In particular, of the nitrification and denitrification reactions that constitute the biological nitrogen removal reaction, in the denitrification reaction, when nitrate nitrogen or nitrite nitrogen is reduced to nitrogen (denitrification), the organic matter in the wastewater is reduced. Is consumed as a hydrogen donor in the reduction reaction. Therefore, when the organic matter concentration of the wastewater is smaller than the nitrogen concentration, there is a problem that a desired amount of denitrification reaction cannot be obtained due to an insufficient hydrogen donor concentration.

Accordingly, the present invention proposes a specific method of controlling a device for solving the above-mentioned problems, and a device for removing nitrogen from wastewater capable of preventing deterioration of the nitrogen removal performance due to temporal fluctuation of water quality. The purpose of the present invention is to provide a control method.

[0008]

According to the present invention, there is provided a method for controlling nitrogen removal of wastewater by a biological nitrogen removal treatment apparatus, the biological nitrogen removal treatment apparatus comprising: Solid-liquid separator, denitrification tank, nitrification tank, second solid-liquid separator, total nitrogen concentration of outlet water of the first solid-liquid separator, ammonia nitrogen and chemical oxygen demand. (1) the first solid-liquid separation device has at least 2
An apparatus that satisfies at least one of the following conditions: (1) the first solid-liquid separation device, and (2) the injection of organic matter into the denitrification tank. Measure the total nitrogen concentration of the outlet water, ammonia nitrogen and chemical oxygen demand to obtain a measured value, based on the measured value, perform a process prediction calculation by a simulation configured by a numerical model in a short time, When it is predicted that the nitrogen removal rate is deteriorated, at least one of the number of operation ponds of the first settling basin constituting the first solid-liquid separation device and the organic substance injection amount is determined based on the simulation result. Provided is a method for controlling nitrogen removal of wastewater, which is characterized by controlling.

The biological nitrogen removal treatment apparatus may further include an anaerobic tank. In this case, the organic substance can be injected into the anaerobic tank.

In the control method of the present invention, the water quality of the outlet water of the sedimentation basin is first analyzed, and the process prediction calculation by a simulation model constituted by a numerical model such as a biological kinetic model is shortened based on the analyzed value. Do it in time. As a result, NO ₂ into the denitrification tank ^- or NO ₃ ^- in the case where the residual is large injection volume of organic material such as methanol to a denitrification tank or anaerobic tank. Alternatively, the amount of organic matter flowing into the wastewater treatment apparatus is increased by reducing the number of operation ponds in the first settling basin. Thereby, the rate of the denitrification reaction in the denitrification tank can be increased, and the amount of the denitrification reaction can be increased.

[0011] The inflow of organic matter and the number of operation pond reduction ponds of the first settling basin are set to the minimum values that can be expected to be effective by calculation using this simulation model.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for controlling nitrogen removal according to the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a biological nitrogen removal treatment apparatus for wastewater to which the method of the present invention can be applied.

The illustrated apparatus mainly includes a first settling tank (first settling tank 2a and first settling tank 2b), a denitrification tank (denitrification tanks 3a and 3b), a nitrification tank (nitrification tanks 4a and 4b),
And the final sedimentation basin 7. In the denitrification tank 3a and the denitrification tank 3b, air is not diffused by the diffusion device 5, but only stirring is performed. An organic substance such as methanol is supplied to the denitrification tank 3a by an organic substance injection pump 11 from an organic substance injection device 10 as needed. In the subsequent nitrification tank 4a and nitrification tank 4b, oxygen is supplied by the air diffuser 5, and agitation is performed by a water flow generated by the air diffusion.

The wastewater 1 is first subjected to solid-liquid separation in the first sedimentation basin 2a and the first sedimentation basin 2b, and then subjected to water quality analysis by the automatic analyzer 14. Thereafter, the denitrification tanks 3a and 3b and the nitrification tank 4
Water is sequentially passed to a and b4b. The effluent flowing out of the nitrification tank 4b and flowing into the final sedimentation basin 7 is separated into treated water 9 and activated sludge in the final sedimentation basin, and at least a part of the activated sludge separated and concentrated in the final sedimentation basin is It is sent to the denitrification tank 3a as activated sludge 8. A part of the effluent flowing out of the nitrification tank 4b is sent to the denitrification tank 3a as the nitrification circulating liquid 6. In the nitrification tank, the activated sludge oxidizes nitrogen compounds in the wastewater to nitrate nitrogen or nitrite nitrogen (= nitrification reaction), and oxidatively decomposes and removes organic substances.

In the denitrification tank, the activated sludge is first treated with the outlet water 16 of the sedimentation basin and the organic matter such as methanol supplied from the organic matter injecting device 10 to the outlet water 1 of the sedimentation basin.
6. The nitrate nitrogen or nitrite nitrogen contained in the returned sludge 8 and the nitrification circulating liquid 6 is reduced to nitrogen gas (= denitrification reaction), and denitrification treatment is performed. Examples of the organic substance injected into the denitrification tank 3a include, for example, methanol, ethanol, acetic acid, and formic acid. However, considering cost, it is preferable to use methanol.

In the apparatus shown in FIG. 1, two initial settling ponds 2a and 2b are provided, and an organic substance is injected into the denitrification tank 3a. These two conditions are simultaneously satisfied. This is not always necessary in the present invention. It suffices if at least one is satisfied.

In the control method of the present invention, the treatment result is first simulated based on the quality of the outlet water of the sedimentation basin,
The operating conditions related to nitrogen removal are automatically controlled using the results. Specifically, in the nitrogen removal treatment apparatus as shown in FIG. 1, the automatic analyzer 14 installed at the outlet of the first settling basin firstly sets the total nitrogen concentration of the outlet water of the first settling basin, ammonia nitrogen and chemical oxygen. The required amount is measured, and the analysis result is automatically input to the control device 15. In addition,
The measurement can be performed continuously or intermittently.

In the control device 15, processing prediction calculation is performed in a short time by a simulation model constituted by a numerical model such as a biological dynamics model. Since the treatment of wastewater by the apparatus as shown in FIG. 1 is usually performed in about eight hours, the treatment prediction calculation must be performed in a shorter time. Specifically, it is desired to perform the process prediction calculation within one hour. In the present invention, NO ₂ in the denitrification tank ^- and NO ₃ ^- the sum is 0 mg / L next, and the case where reduction pond number becomes minimum injection volume or the first sedimentation tank of the organic material, using a model calculation I do.

If NO ₂ ^- or NO ₃ ^- is predicted to remain in the denitrification tank by numerical calculation, the controller 15
, At least one of the following operating conditions (1) and (2) is performed.

(1) The flow rate of the organic substance injection pump 11 for injecting organic substances into the denitrification tank 3a is increased.

(2) By increasing the opening of the valve 12a and decreasing the opening of the valve 12b, the flow rate of wastewater flowing into the denitrification tank 3a bypassing the sedimentation basin 2b at first is increased. .

Such control can be performed manually. Alternatively, in the apparatus shown in FIG. 1, the organic substance injection pump 11 and the valves 12a and 12b
By providing an automatic control line, it is also possible to carry out automatically.

The operation cost can be minimized by setting the methanol injection amount and the flow rate of the wastewater flowing into the denitrification tank by bypassing the first sedimentation basin 2b to the minimum values that can be expected by numerical calculation. .

The wastewater treatment apparatus used in the present invention includes:
In addition to the denitrification step and the nitrification step, another step may be included. For example, the nitrogen removal method according to the present invention can be applied to a wastewater treatment apparatus including an anaerobic step, a denitrification step (anoxic step), and a nitrification step (aerobic step). In addition, when the properties and the amount of the wastewater to be treated do not significantly change, even if the analysis by the automatic analyzer is intermittent, the actual reaction control is not hindered.

FIG. 2 shows another example of a biological nitrogen removal treatment apparatus to which the method of the present invention can be applied. The illustrated apparatus is the same as that shown in FIG. 1 except that an anaerobic tank 17 is provided upstream of the denitrification tank 3a. That is, the apparatus shown in FIG. 2 is initially composed of the sedimentation basins 2a and 2b, the anaerobic tank 17, the denitrification tanks 3a and 3b, the nitrification tanks 4a and 4b, and the final sedimentation basin 7.

In the biological nitrogen removal treatment apparatus shown in FIG. 2, the anaerobic tank 17 is a tank in which only stirring is performed, and wastewater 1 and returned sludge 8 are introduced into the anaerobic tank. In the anaerobic tank 17, the activated sludge uses the organic matter in the wastewater 1 to reduce nitrate nitrogen or nitrite nitrogen contained in the settling pond outlet water 16 and the return sludge 8 to nitrogen gas (= denitrification). Reaction) and denitrification. Further, in this anaerobic tank, activated sludge releases phosphate ions accumulated in cells into wastewater (= biological phosphorus release reaction). In the denitrification tanks 3a and 3b and the nitrification tanks 4a and 4b, the activated sludge takes in phosphate ions in the wastewater into cells (biological phosphorus uptake reaction).

In the apparatus shown in FIG. 2, an organic substance such as methanol supplied from the organic substance injector 10 may flow into the anaerobic tank 17.

[0029]

Now, the present invention will be described in further detail with reference to specific examples.

The simulation model to be constructed is a kinetic model capable of reproducing the actual apparatus, and the amount of suspended sludge in the mixed solution, the concentration of returned sludge, and the amount of excess sludge are always corrected based on the measurement results of the actual apparatus. I will add it. Calibration is also performed on kinetic constants as necessary.

As the kinetic reaction rate equation, a microorganism growth rate equation based on the Monod equation is used.

In this embodiment, the nitrogen removal performance was examined under the following operating conditions using the wastewater treatment apparatus having the flow shown in FIG.

Inflow water volume: 80 L / day Nitrification circulating water volume: 135 L / day Returned sludge volume: 25 L / day Denitrification tank volume: 20 L Nitrification tank volume: 20 L Water temperature: 15 ° C. MLSS: 3000 mg / L Blow volume: 480 L / day The parameters for the simulation in the example and the changes over time of the processing results and the like are shown in the graphs of FIGS.

The graph of FIG. 3 shows the time-dependent changes in the COD concentration in the outlet water of the precipitation tank and the NO _x -N concentration in the aerobic tank. In the graph of FIG. 3, curve a represents the COD concentration of the outlet water of the settling basin at the beginning, curve b represents the NO _x -N concentration when the control of the present invention is not performed, and curve c represents the control of the present invention. Represents the NO _x -N concentration in the case of the above.

In this embodiment, the treatment results are obtained by simulation based on the COD concentration, total nitrogen concentration and ammonia nitrogen concentration of the outlet water of the settling basin at first, and the amount of methanol as an organic substance is adjusted according to the results. Control. The graph in FIG. 4 shows the change over time in the amount of methanol added during control according to the present invention. The amount of methanol added increases in response to the decrease in the COD concentration of the influent water and the increase in the NO _x -N concentration in the aerobic tank shown in FIG.

By increasing the amount of methanol added as described above, it was possible to suppress the increase in the NO _x -N concentration as shown by the curve c in the graph of FIG.

Table 1 below shows the results of the treatment in the case of the conventional operation and the results of the operation in which the control of the present invention was performed, for COD, total nitrogen concentration and NO _x -N concentration in the treated water. Put together.

[0038]

[Table 1]

As shown in Table 1, by controlling the present invention, the total nitrogen concentration in the treated water could be reduced.

In the above-mentioned example, the target treated nitrogen concentration was achieved by controlling the amount of methanol as an organic substance.
It is possible to prevent deterioration of the nitrogen removal performance due to the time variation of the quality of the wastewater.

[0041]

As described above, according to the present invention, there is provided a method for controlling the nitrogen removal treatment of wastewater, which can prevent the deterioration of the nitrogen removal performance due to the time variation of water quality. By using the method of the present invention, it is possible to appropriately replenish the organic matter even when the concentration of the organic matter in the wastewater is insufficient due to the time variation of the quality of the wastewater and a desired nitrogen reaction amount cannot be obtained. Therefore, it is possible to prevent deterioration of the nitrogen removal performance due to the time variation of the wastewater quality. INDUSTRIAL APPLICABILITY The present invention can be effectively used for treating sewage containing nitrogen, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an example of a biological nitrogen removal treatment apparatus for wastewater to which a control method of the present invention is applied.

FIG. 2 is a schematic diagram showing the configuration of another example of the biological nitrogen removal treatment apparatus for wastewater to which the control method of the present invention is applied.

FIG. 3. COD concentration in influent water and NO _{x in} aerobic tank
FIG. 4 is a graph showing a change over time in -N concentration.

FIG. 4 is a graph showing the change over time in the amount of methanol added.

FIG. 5 is a schematic diagram illustrating a configuration of a conventional wastewater treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inflow wastewater 2, 2a, 2b ... First sedimentation basin 3, 3a, 3b ... Denitrification tank 4, 4a, 4b ... Nitrification tank 5 ... Aeration device 6 ... Nitrification circulating liquid 7 ... Final sedimentation basin 8 ... Returned sludge 9 ... Treated water 10 ... Organic substance injection device 11 ... Organic substance injection pump 12a, 12b ... Valve 14 ... Automatic analyzer 15 ... Control device 16 ... First settling pond outlet water 17 ... Anaerobic tank

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Miyata 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Toshiaki Inventor Bureau 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Kei Baba Kei 1-2-1 Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan Co., Ltd. (72) Kenichiro Mizuno 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan (72) Inventor Tatsuo Takechi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4D040 BB05 BB12 BB22 BB57 BB65 BB91 BB93 5H004 GB08 HA04 HB04 JB08 JB18 KA12 KC02 KC27 LA19

Claims (1)

[Claims] 1. A method for controlling nitrogen removal of wastewater by a biological nitrogen removal treatment apparatus, wherein the biological nitrogen removal treatment apparatus comprises a first solid-liquid separation device, a denitrification tank, a nitrification tank, And (2) an automatic analyzer for measuring the total nitrogen concentration, ammonia nitrogen and chemical oxygen demand of outlet water of the first solid-liquid separator. The first solid-liquid separation device includes at least two primary sedimentation basins; and (2) an organic substance is injected into the denitrification tank.
An apparatus that satisfies at least one of the following conditions: The automatic analyzer is used to measure the total nitrogen concentration of the outlet water of the first solid-liquid separator, the ammonia nitrogen, and the chemical oxygen demand to obtain measurement values, Based on the measured values, a process prediction calculation by a simulation constituted by a numerical model is performed in a short time, and when it is predicted that the nitrogen removal rate is deteriorated, the first solid-liquid separation device is configured. A method for controlling nitrogen removal of wastewater, wherein at least one of the number of operating ponds of the first settling basin and the amount of injected organic matter is controlled based on the simulation result.