JP6862594B2 - Wastewater treatment method - Google Patents

Description

The present invention relates to a method for bionitrifying and denitrifying wastewater having a high concentration of soluble evaporation residue and / or potassium ion in a final disposal site leachate treatment facility, urine treatment facility, industrial wastewater treatment facility, etc. The present invention relates to a wastewater treatment method in which the ammonia concentration in the nitrification tank is measured with an ammonium ion electrode and the amount of oxygen-containing gas supplied to the nitrification tank is controlled.

Conventionally, as the control of the nitrification reaction of the biological nitrification denitrification method, DO (dissolved oxygen) control and pH control of a biological reaction tank (hereinafter, also referred to as a nitrification tank) for performing a nitrification reaction have been used. In recent years, in sewage treatment, the introduction of ammonium ion electrodes ( _{also called ammonia sensor, NH 4} sensor, NH ₄ meter, and ammonia meter) is progressing to control the nitrification reaction.

Patent Document 1 and Patent Document 2 describe a method of controlling a gas supply amount or the like by using an ammonia sensor or the like for nitrification and denitrification treatment in a sewage treatment plant. Further, Patent Document 3 describes a method of controlling the amount of air blown by a fluorescence measurement sensor that measures the amount of fluorescence of a biological phosphor generated by a microorganism by irradiating the microorganism floc with ultraviolet rays, and uses an ammonia concentration as an auxiliary sensor. An ammonia sensor for measurement is used.

Further, Non-Patent Document 1 describes _{a method of using a NO X-} N meter and an NH _4- N meter for air volume control in sewage treatment, and describes simultaneous nitrification and denitrification treatment in the aerobic part of a deep aeration tank. There is. In Non-Patent Document 2, an NH _4- N meter is used to control the amount of air in sewage treatment, simultaneous nitrification and denitrification treatment in an aerobic tank, and the existence of an optimum _{NH 4-N value in the nitrification endonitrification method.} There is a description about the superiority of _{NH 4-} N control over DO control as an air volume control method. Further, in Non-Patent Document 3, an ion sensor of ammonia nitrogen, nitrate nitrogen, and potassium is installed as an automatic measuring instrument in the treatment plant of the OD method in which the dehydrated filtrate of human waste is diluted 7-fold and then mixed with sewage and accepted. However, there have been reports of cases where the processing status has been improved by visualizing operation data.

Japanese Unexamined Patent Publication No. 2012-135717 Japanese Unexamined Patent Publication No. 2015-16410 Japanese Patent No. 4381473

Takashi Kasai, Keiichi Sone, Shigehiro Suzuki, Hiroyuki Takahashi, Mitsuhiro Kurosumi, Ryohei Sakane: Development of new advanced treatment technology (simultaneous nitrification denitrification treatment) using denitrification in aerobic tank, Journal of Sewerage Association, Vol. 52, No. 635, pp. 114-121, (2015) Kazuko Kamachi, Yasuhiro Homma, Satoru Suzumura: Optimization of air volume control operation using an ammonia sensor using an activated sludge model, Journal of the Society "EICA", Vol. 20, No. 2 and 3 merger, pp. 3-10, (2015) Minoru Matsui, Junji Honda, Seiji Kiuchi: Lectures at the 50th Sewerage Research Presentation on the operating conditions for nitrogen removal in the OD method, pp. 811-813, (2013)

As described above, nitrification tank DO control and pH control have been used to control the nitrification reaction of the biological nitrification denitrification method. However, since the ammonia nitrogen concentration cannot be grasped by DO control or pH control, by supplying sufficient air to the nitrifying tank and setting the DO concentration to a high level of about 2 mg / L, almost all of the nitrifying bacteria act. Ammonia nitrogen was converted to nitrate nitrogen. Therefore, a large amount of air is required in the nitrification tank.

_{In sewage treatment, the adoption of NH 4} sensors is progressing in order to improve this problem, but the soluble evaporation residue to be treated at final disposal site leachate treatment facilities, urine treatment facilities, industrial wastewater treatment facilities, etc. In the case of wastewater with a high concentration of substances and / or potassium ions, it _{is difficult to apply the NH 4} sensor due to the influence of coexisting ions and / or potassium ions, and wastewater with a high concentration of soluble evaporation residue and / or potassium ions. There are no reported examples of _{NH 4} sensors that can be applied to.

According to the present invention, the ammonia concentration can be accurately measured even for wastewater having a high soluble evaporation residue and / or potassium ion concentration, and the stable progress of the nitrification reaction can be achieved without excessively increasing the DO value of the nitrification tank. It is an object of the present invention to provide a wastewater treatment method capable of enhancing the effect of removing nitrogen and reducing the concentration by causing simultaneous progress of nitrification and denitrification.

The wastewater treatment method according to the present invention removes wastewater having a soluble evaporation residue of 500 to 30,000 mg / L and / or a potassium ion concentration of 40 to 600 mg / L from at least a nitrification tank, a nitrification tank, and a secondary denitrification tank. As a liquid analyzer that measures the ammonia concentration in the nitrification tank in the wastewater treatment method that performs biological nitrification and denitrification treatment by introducing it into the re-absorption tank, it is inside the space that communicates with the outside through the liquid junction. A comparative electrode provided with a saturated potassium chloride solution which is a liquid and an Ag / AgCl electrode which is an internal electrode in contact with the internal liquid, and an ammonium chloride aqueous solution and the inside as an internal liquid in a space partitioned from the outside by a response film. A configuration including an ammonium ion electrode having an Ag / AgCl electrode as an internal electrode in contact with a liquid, and a potassium ion electrode for measuring the potential of potassium ions used for correcting interference of potassium ions with ammonium ions. The amount of oxygen-containing gas supplied to the nitrification tank is controlled so that the concentration of ammoniacal nitrogen in the nitrification tank measured by the liquid analyzer is 1 to 20 mg / L, and the DO of the nitrification tank is used. By controlling the value to 1 mg / L or less, the nitrification reaction and the denitrification reaction proceed simultaneously in the nitrification tank.
The measurable concentration range of the ammonium ion to be measured is preferably lower than the chloride ion concentration in the internal liquid of the comparative electrode. Further, the internal liquid of the ammonium ion electrode contains ammonium ions and chloride ions, and it is desirable that the internal liquid of the ammonium ion electrode has an isothermal intersection point with the osmotic pressure of the internal liquid of the ammonium ion electrode. The concentration of ammonium ion and the concentration of chlorine ion in the internal liquid of the ammonium ion electrode are adjusted so that the value becomes a value and the isothermal intersection point is included in the measurable concentration range. It is preferable that the concentration of the chlorine ion is different from the concentration of the chlorine ion in the internal liquid of the comparative electrode.
According to the above-mentioned liquid analyzer according to the present invention, the ammonia concentration can be accurately measured even for wastewater having a high soluble evaporation residue and / or potassium ion concentration without being affected by coexisting ions and / or potassium ions. It was confirmed by experiment that it can be done. Therefore, the amount of oxygen-containing gas supplied to the nitrification tank can be accurately controlled according to _{the NH 4 concentration of the nitrification tank.}
Then, _{by controlling the supply amount of the oxygen-containing gas according to the NH 4} concentration of the nitrification tank, it is not necessary to increase the DO value of the nitrification tank as in the conventional case. That is, the DO value of the nitrification tank can be kept lower than the conventional value of 1 mg / L or less, the nitrification reaction can proceed stably in the nitrification tank, and the nitrification and denitrification simultaneous progress in the nitrification tank occurs, and nitrogen. It is possible to enhance the effect of reducing the removal concentration.

Further, _{by controlling the supply amount of the oxygen-containing gas according to the NH 4} concentration of the nitrification tank, it is not necessary to increase the DO value of the nitrification tank as in the conventional case. That is, it is possible to keep the DO value of the nitrification tank lower than before, the nitrification reaction can proceed stably in the nitrification tank, and the nitrification denitrification simultaneous progress occurs in the nitrification tank, which enhances the effect of reducing the nitrogen removal concentration. It becomes possible.

Further, in the present invention, the nitrification tank is functionally divided into a plurality of parts, and the amount of oxygen-containing gas supplied to the nitrification tank is controlled so that the ammonia nitrogen concentration in the first half of the divided nitrification tanks is 1 to 20 mg / L. However, by setting the DO value of the first half of the nitrification tank to 1 mg / L or less, the nitrification reaction and the denitrification reaction proceed simultaneously in the first half of the nitrification tank, while the DO value in the second half of the divided nitrification tank. It is characterized _{in that NH 4-} N remaining in the first half of the nitrification tank is nitrified to NO _X- N by controlling the supply amount of oxygen-containing gas so that the value becomes 1 to 3 mg / L. As a result, the NH _4- N + NO _X- N value of the discharged water can be reduced, and even better nitrogen removal can be achieved.

According to the present invention, even for wastewater having a high soluble evaporation residue and / or potassium ion concentration, the ammonia concentration can be accurately measured without being affected by coexisting ions and / or potassium ions, as in the conventional case. The DO value of the nitrification tank is not excessively increased, the stable progress of the nitrification reaction in the nitrification tank and the simultaneous progress of nitrification and denitrification in the nitrification tank occur, and the effect of removing nitrogen and reducing the concentration can be enhanced.

It is a perspective view of the liquid analyzer (NH _{4 sensor) 100.} It is a figure which shows the use state of NH _{4 sensor 100.} It _{is a figure which shows the tip surface of the NH 4} sensor 100 (however, the state where the sensor S2 is removed). FIG. 3 is a cross-sectional view taken along the line AA of FIG. FIG. 1 is a sectional view taken along the line BB (or a sectional view taken along the line CC) of FIG. It is a figure which shows an example of the processing flow by a standard denitrification treatment method. It is a figure which shows an example of the processing flow by the membrane separation high load denitrification treatment method. It is a figure which shows an example of the processing flow by the pre-dehydration + standard denitrification treatment method. It is a schematic block diagram which shows an example of the aeration type aeration apparatus 400. It is a schematic block diagram which shows an example of a pump circulation type aeration apparatus 430. It is a schematic block diagram which shows an example of the air injection type aeration apparatus 460. It is a figure which shows the comparison of the NH _{4 sensor measurement value and the water quality analysis result.} It is a figure which shows the performance measurement result of NH _{4 sensor 100.} It is a figure which shows the result of the air amount control operation by the NH _4- N concentration using the NH _{4 sensor 100.} It is a figure which compares and shows the result of the air amount control by a nitrification tank NH _{4-N concentration, and the air amount control by a nitrification tank DO concentration.} It is a figure which compares and shows the result of the air amount control by a nitrification tank NH _{4-N concentration, and the air amount control by a nitrification tank DO concentration.} It is a figure which shows each measured value when the DO value of the nitrification tank 270 is set to 1 mg / L or less by reducing the flow rate of human waste which flows into a biological reaction tank. It is a figure which shows each measured value at the time of raising the NH _4- N set value of a nitrification tank 270, and setting the DO value of a nitrification tank 270 to 1 mg / L or less. It is a figure which shows the test result of the test performed on NH _{4 sensor 100.} It is a figure which shows an example of the processing flow by the standard denitrification treatment method which divided the function of a nitrification tank. It is a figure which shows an example of the treatment flow by the pre-dehydration + standard denitrification treatment method which divided the function of a nitrification tank. Compare the results of air volume control based on the nitrification tank DO concentration, air volume control based on the nitrification tank NH _4- N concentration, and air volume control that divides the nitrification tank into two zones according to the DO concentration in the standard denitrification treatment method. It is a figure which shows. Pre-dehydration + standard denitrification treatment method, air volume control by nitrification tank DO concentration, air volume control by nitrification tank NH _4- N concentration, and air volume control by dividing the nitrification tank into two zones according to DO concentration. It is a figure which compares and shows the result.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
The water to be treated (liquid to be analyzed) to be treated in the present invention is water to be treated having a high concentration of soluble evaporation residue and / or potassium ion. Examples include wastewater discharged to human waste treatment facilities and industrial wastewater treatment facilities. In the present invention, the treatment of sewage containing human waste and septic tank sludge is referred to as "human waste treatment", and is a conventional human waste treatment plant or sludge regeneration treatment center (organic waste such as kitchen waste in addition to human waste and septic tank sludge). Means the processing in). In addition, sewage containing human waste and septic tank sludge to be treated at a human waste treatment plant or a sludge recycling treatment center is also referred to as “human waste, etc.”.

In recent years, _{the soluble evaporation residue in the reaction vessel of the sewage treatment plant where the NH 4} sensor according to the present invention is to be introduced is about 100 to 400 mg / L, and the potassium ion concentration is about 10 to 30 mg / L. In addition, the soluble evaporation residue in the final disposal site leachate may reach 60,000 mg / L, but in the case of biological nitrification denitrification treatment, the soluble evaporation residue in the reaction vessel is 30,000 mg. Dilute to less than / L. The potassium ion concentration in the reaction tank of the final disposal site leachate is approximately 10 to 60 mg / L. In the urine treatment, the soluble evaporation residue in the reaction vessel is about 500 to 10,000 mg / L, and the potassium ion concentration is about 40 to 600 mg / L. That is, in the present invention, a high soluble evaporation residue means a case where the soluble evaporation residue is about 500 mg / L or more, and a high potassium ion concentration means that the potassium ion concentration is about 40 mg / L or more. Let's say the case.

Figure 1 is a perspective view of a liquid analyzer (hereinafter referred to as "NH ₄ sensor") 100 for use in the present invention, FIG, 3 2 showing a state of use of NH ₄ sensor 100 indicates a distal end surface of the NH ₄ Sensor 100 FIG. 4 is a sectional view taken along the line AA of FIG. 3 and FIG. 5 is a sectional view taken along the line BB (or a sectional view taken along the line CC) of FIG. As shown in these figures, the NH ₄ sensor 100 is a combination of three sensors S1, S2, and S3, and is a reference electrode for measuring a reference potential as the sensors S1, S2, and S3. Comparative electrode) S3, an ammonium ion electrode S1 for measuring the potential due to ammonium ions, and a potassium ion electrode S2 for measuring the potential due to potassium ions used for correcting the interference of potassium ions with ammonium ions. I have. When the potassium ion concentration of the solution to be measured is high, the influence of potassium ion interference on the ammonium ion concentration measurement becomes large, which may interfere with the ammonium ion measurement.

The NH ₄ sensor 100 has a substantially thin cylindrical housing, a chain for carrying is provided on the base end side (lower side in FIG. 1), and three sensors S1 are provided on the tip surface on the opposite side. The sensor surfaces SP1, SP2, and SP3 of S2 and S3 are installed so as to be exposed to the outside. In the present embodiment, the sensor surfaces SP1, SP2, and SP3 refer to the surfaces on which the response films S11, S21 and the liquid junction S31 of each electrode are formed.

Then, as shown in FIG. 2, _{the tip surface of the NH 4} sensor 100 is immersed in the analysis target liquid (processed liquid) L so as to face vertically downward, and the sensor surfaces SP1, SP2, SP3 of each of the sensors S1, S2, and S3. Each potential is measured while being immersed in the analysis target liquid L, and the ammonium ion concentration in the analysis target liquid L is measured. As can be seen from FIGS. 1 and 2, two of the three sensors S1, S2, and S3 have the sensor surfaces SP1 and SP2 of the housing in order to prevent bubbles from accumulating on the sensor surfaces SP1 and SP2 during analysis. It is provided at an angle with respect to the axial direction. Further, the two inclined sensor surfaces SP1 and SP2 are configured so that their directions face the same predetermined direction.

The tip surface of the NH ₄ sensor 100 is formed in a circular shape, and the sensor surface SP3 of the reference electrode S3 and the thermometer protection tube P described later are arranged side by side on the center line thereof. Further, the tip portion of the ammonium ion electrode S1 and the tip portion of the potassium ion electrode S2 are arranged side by side in a line at a position slightly deviated from the center line orthogonal to the center line.

As shown in FIGS. 4 and 5, the NH ₄ sensor 100 is inserted into the body 1 having a substantially cylindrical shape having a hollow portion on the base end side and a solid portion formed on the tip end side, and the body 1. It is configured to include three sensors S1, S2, and S3, and a cap-shaped pressing mechanism 2 provided so as to cover the tip end side of the body 1. The pressing mechanism 2 presses and fixes the three sensors S1, S2, and S3 against the body 1.

Four insertion holes PH1, PH2, PH3, and PH4 extending in the axial direction are formed in the body 1, and three sensors S1, S2, and S3 having a substantially cylindrical shape correspond to the thermometer protection tube P, respectively. It is inserted into the insertion holes PH1, PH2, PH3, and PH4. Further, no female screw is formed in the insertion holes PH1, PH2, and PH3, and the sensors S1, S2, and S3 are simply inserted. The thermometer protection tube P is fixed to the insertion hole PH4 so as not to come off. Further, inside the thermometer protection tube P, a temperature sensor TS for measuring the temperature used for temperature compensation for the measured values of the sensors S1, S2, and S3 is housed.

Explaining the common parts of the three sensors S1, S2, and S3, as can be seen from each figure, the sensors S1, S2, and S3 are resin support tubes S12, S22, and S32 formed in a substantially cylindrical shape. The internal liquids S13, S23, and S33 and the internal electrodes S1E, S2E, and S3E immersed in the internal liquids S13, S23, and S33 are housed inside the support pipes S12, S22, and S32. .. An opening is formed at the tip of the support pipes S12, S22, and S32, and a response film S11, S21, or a liquid connection portion S31 is provided so as to close the opening. Further, an O-ring is provided on the outer peripheral surfaces of the support tubes S12, S22, and S32, and is configured to form a shaft seal between the insertion holes PH1, PH2, and PH3. Further, the base ends of the sensors S1, S2, and S3 come into contact with the electrode terminal D at the innermost part of the insertion holes PH1, PH2, and PH3, and the acquired potentials are transmitted from the electrode terminals D to an external arithmetic unit. It is designed to be done. Further, the parts common to the appearance shapes of the support tubes S12, S22, and S32 will be described in more detail. The tips of the support tubes S12, S22, and S32 of the sensors S1, S2, and S3 are closer to the base end side than the base end side. It has thick cylindrical portions S14, S24, S34 having a large diameter, and the end faces on the base end side of the thick cylindrical portions S14, S24, S34 engage with the step portions formed in the insertion holes PH1, PH2, and PH3. It functions as body contact surfaces S17, S27, and S37 that come into contact with the body 1. Further, ring-shaped protrusions S15, S25, and S35 protruding in the radial direction are formed in the central portion of the outer peripheral surface of the thick cylindrical portions S14, S24, and S34, and the tip-side planes of the protrusions S15, S25, and S35 are formed. It is configured as engaging portions S16, S26, and S36 that engage with the pressing mechanism 2. That is, when the engaging portions S16, S26, and S36 are pushed toward the body 1 by the pressing mechanism 2, the body contact surfaces S17, S27, and S37 are pressed against the body 1, and the sensors S1 and S2 are pressed. , S3 is fixed to the body 1 with a predetermined force.

Of the three sensors S1, S2, and S3, the reference electrode S3 has a sensor surface SP3 formed in a direction perpendicular to the center line (extension axis) of the reference electrode S3. Is configured to be removable from the tip of the support tube S32, and can be replaced when the function as the liquid connection portion S31 deteriorates due to dirt or the like due to continuous use.

As shown in FIG. 5, the ammonium ion electrode S1 and the potassium ion electrode S2 are provided with response films S11 and S21, and the sensor surfaces SP1 and SP2 thereof are relative to the central axes (stretched axes) of the sensors S1 and S2. It is provided at an angle. The shapes of both sensors S1 and S2 are substantially the same.

The pressing mechanism 2 collectively presses all the sensors S1, S2, and S3 against the body 1. In the cross-sectional view, it is shown as a roughly U-shaped member on the tip surface of the ammonia meter 100, and substantially covers the tip portion of the body 1. Further, through holes TH1 for exposing the sensor surfaces SP1, SP2, SP3 of the sensors S1, S2, S3 and the tip of the thermometer protection tube P to the outside while covering the tip of the body 1. It has four TH2, TH3, and TH4.

The internal liquid S13 of the ammonium ion electrode S1 of the present embodiment contains ammonium chloride, and an Ag / AgCl electrode is used as the internal electrode S1E. Further, the response membrane S11 is a membrane that selectively responds to ammonium ions and has properties as a semipermeable membrane. Specific examples of the film corresponding to each of such ions include those made of an organic solvent and a polyvinyl chloride resin or silicone rubber that supports them. On the other hand, a supersaturated potassium chloride solution is used as the internal liquid S33 of the reference electrode S3, and an Ag / AgCl electrode is used as the internal electrode S3E.

The membrane potential (mV) of the response film S11 of the ammonium ion electrode S1 can be represented by the following formula (1).

Here, each parameter in the equation (1) is as follows.
E: Membrane potential (mV) of the response film S11 of the ammonium ion electrode S1
E ^O Ion: Standard electrode potential (mV) of ammonium ion electrode S1
R: Gas constant F: Faraday constant T: Absolute temperature (K)
a _{N, Sample:} analyte solution NH ₄ ⁺ ion activity in L (moL / L)
a _N , _{Ion : Ion activity of NH 4} ⁺ in the internal liquid S13 of the ammonium ion electrode S1 (moL / L)
a _Cl , _Ref ^{: Ion activity of Cl − in} the internal liquid S33 of the reference electrode S3 (moL / L)
a _Cl , _Ion ^{: Ion activity of Cl − in} the internal liquid S13 of the ammonium ion electrode S1 (moL / L)

In the present embodiment, the ion activity (ion concentration) of each ion is adjusted so that the point where the entire B term surrounded by the solid line in the formula (1) becomes 1 is within the measurable concentration range. As a result, an isothermal intersection can be obtained within the concentration range of ammonium ions in the solution L to be analyzed, that is, within the measurement range. Further, in the present embodiment, the concentration of ammonium ion and the concentration of chloride ion in the internal liquid S13 are adjusted so that the osmotic pressure of the internal liquid S13 becomes the same as the osmotic pressure of the liquid L to be analyzed. .. A simulation may be performed based on the equation (1), and the internal liquid may be prepared so that the isothermal intersection is within the measurement range.

According to the ammonium meter 100 of the present embodiment configured as described above, the osmotic pressure of the internal liquid S13 is increased by varying the concentration of ammonium ions and the concentration of chloride ions in the internal liquid S13 of the ammonium ion electrode S1. While adjusting the osmotic pressure to the same level as the osmotic pressure of the solution L to be analyzed, an isothermal intersection point can be obtained within the concentration range of ammonium ions in the solution L to be analyzed, so that the concentration of soluble evaporation residue and / or potassium ion can be increased. The inventor of the present application has found that the ammonia concentration can be accurately measured without being affected by coexisting ions and / or potassium ions even when targeting high waste water.

The following tests have been performed on the _{NH 4 sensor 100.} That is, as the reference electrode (comparison electrode) S3, a solution in which the internal solution S33 was 3.33 M potassium chloride solution was used. On the other hand, the internal liquid S13 of the ammonium ion electrode S1 was prepared so that the isothermal intersection was 0.0000714M (1ppm · N) and the osmotic pressure was the same as that of the aqueous solution having a salt concentration of 0.03M. Using the reference electrode S3 and the ammonium ion electrode S1 having the above configuration, it was confirmed whether or not the response of the electrode according to the calculation formula (1) while changing the temperature. As a result, as shown in FIG. 19, it is confirmed that the ammonium ion concentration has an isothermal intersection at 0.0000714M (1ppm · N). If the isothermal intersection deviates from the measurable concentration range, and the measured value E within the measurable concentration range does not completely follow the equation (1), the E expected from the equation (1) is actually used. Since the deviation from the measured value E of is large, the measurement error becomes large.

That is, in the NH ₄ sensor 100, the measurable concentration range of the ammonium ion to be measured is preferably lower than the chloride ion concentration in the internal liquid S33 of the reference electrode (comparative electrode) S3. Further, the internal liquid S13 of the ammonium ion electrode S1 contains ammonium ions and chloride ions, and the internal liquid S13 of the ammonium ion electrode S1 has an isotherm with the osmotic pressure of the internal liquid S13 of the ammonium ion electrode S1. The concentration of ammonium ions and the concentration of chlorine ions in the internal liquid S13 of the ammonium ion electrode S1 are adjusted so that the desired value is obtained and the isothermal intersection point is within the measurable concentration range. It is preferable that the concentration of the chlorine ions is different from the concentration of the chlorine ions in the internal liquid S33 of the reference electrode S3.

By the way, conventionally, as a treatment method for removing biological nitrogen, an activated sludge method using planktonic organisms, a carrier utilization treatment method using planktonic organisms and a fluid biofilm, and a catalytic oxidation method using a biofilm are used. The above-mentioned method for controlling the amount of air in a nitrification tank using _{the NH 4} sensor 100 for wastewater having a high concentration of soluble evaporation residue and / or potassium ion of the present invention can be applied to any treatment method.

As described above, when the potassium ion concentration of the solution to be measured is high, the influence of potassium ion interference on the ammonium ion concentration measurement is large, which hinders the ammonium ion measurement. It seems that it will be more difficult to measure the ammonia concentration with the NH _{4 sensor 100.} Therefore, a detailed explanation will be given regarding the treatment of human waste.

As an example, the main properties of urine and the like are pH: 7 to 8, SS: 5,000 mg / L to 15,000 mg / L, BOD: 2,000 to 15,000 mg / L, and ammoniacal nitrogen: 500 to 5,000 mg / L.

As a biological denitrification treatment method for human waste treatment, a circulating nitrification denitrification method, which is an activated sludge method, is applied, and a standard denitrification treatment method, a high-load denitrification treatment method, a membrane separation high-load denitrification treatment method, A denitrification treatment method with a high mixing ratio of septic tank sludge, a pre-dehydration + standard denitrification treatment method, etc. are applied.

[Standard denitrification method]
FIG. 6 is a diagram showing an example of a processing flow by the standard denitrification treatment method. As shown in the figure, in the treatment flow by this standard denitrification treatment method, a denitrification tank 210, a nitrification tank 220, a secondary denitrification tank 230, a reaeration tank 240, and a settling basin 250 are installed. Therefore, the processing is performed in this order.

That is, the pretreated human waste and septic tank sludge (hereinafter, also referred to as “human waste”) from which the residue and the like have been removed by a screen or the like are supplied to the denitrification tank 210 together with the diluted water. Diluted water that flows into the denitrification tank 210 and is 1 to 10 times the amount of human waste is supplied. Well water or the like is used as the diluted water, but in addition to this, miscellaneous wastewater (drainage generated in the field such as dehydration filtrate and equipment washing water) is also supplied together with the diluted water. Hereinafter, it will be referred to as diluted water including miscellaneous wastewater. The returned sludge returned from the settling basin 250 and the nitrification liquid (nitrification circulation liquid) circulated from the end of the nitrification tank 220 also flow into the denitrification tank 210. The denitrification tank 210 is agitated under anoxic conditions, and nitrate nitrogen and nitrite nitrogen in the nitrifying liquid circulated while utilizing the BOD component in the denitrifying bacteria urine and septic tank sludge (hereinafter, NO _X- Perform denitrification treatment to convert N) to nitrogen gas.

Next, the mixed solution flowing out of the denitrification tank 210 is introduced into the nitrification tank 220 and aerated. Here, BOD that could not be completely removed in the denitrification tank 210 is removed, and ammoniacal nitrogen (hereinafter referred to as "NH _4- N") is oxidized to _{NO X-N by the action of nitrifying bacteria.} The nitrification tank 220 is equipped with a DO meter 223, a pH meter 225, and the NH ₄ sensor 100, and air is supplied by the aeration device described below.

Most of the mixed liquid in which nitrification has progressed in the nitrification tank 220 is circulated to the denitrification tank 210 by the nitrification liquid circulation pipe 221 and the rest flows into the secondary denitrification tank 230. In the secondary denitrification tank 230, which is in an oxygen-free state like the denitrification tank 210, NO _X- N flowing from the nitrification tank 220 is denitrified. In the denitrification here, endogenous respiratory denitrification is also performed, but it is preferable to improve the efficiency of the denitrification reaction by adding a hydrogen donor such as methanol.

Next, organic substances such as methanol remaining in the secondary denitrification tank 230 are removed by aeration treatment in the re-aeration tank 240.

Next, the effluent from the reaeration tank 240 is guided to the settling basin 250, where it is separated into sludge and treated water. A part of the sludge concentrated in the settling basin 250 is sent to the denitrification tank 210 as return sludge by the sludge return pipe 251 and the rest is treated as excess sludge. The treated water overflowing from the settling basin 250 is discharged after undergoing advanced treatment such as coagulation sedimentation treatment.

MLSS (Mixed Liquor Suspended Solids), which is a standard denitrification treatment method, is often operated at about 6000 mg / L.

The liquid temperature of each reaction tank in the biological nitrification denitrification method is higher than that of human waste or diluted water. This is because the nitrification reaction and denitrification reaction are exothermic reactions, and the heat generated by the biological reaction in each reaction tank and the heat flowing into the reaction tank such as the amount of heat of the blown air generated by the aeration device are due to aeration. This is because the amount of heat taken out by the exhaust gas is larger than the heat flowing out from the reaction tank. The activity of nitrite bacteria increases up to 38 ° C, but decreases above 38 ° C. Therefore, in order to stabilize the treatment of the nitrification tank 220, the upper limit of the liquid temperature for the biological nitrification denitrification treatment is 38 ° C. Is preferable.

[High-load denitrification treatment method, membrane separation high-load denitrification treatment method]
High-load denitrification treatment method and membrane separation In the high-load treatment method of high-load denitrification treatment method, pretreated urine is treated with a high-volume load nitrification denitrification facility without dilution, and separation after solid-liquid separation. This is a method in which water is discharged after undergoing advanced treatment such as coagulation sedimentation treatment. In the high load processing method, it is necessary to maintain MLSS at 8,000 to 20,000 mg / L in order to enable high volume load operation. As a solid-liquid separation method for activated sludge with high MLSS, a mechanical separation method such as a centrifugal concentrator is generally adopted in the high-load denitrification treatment method, and microfiltration in the membrane separation high-load denitrification treatment method. A membrane separation method using a membrane (MF membrane) or an ultrafiltration membrane (UF membrane) is adopted.

FIG. 7 is a diagram showing an example of a processing flow by the membrane separation high load denitrification treatment method. As shown in the figure, the treatment flow by this membrane separation high load denitrification treatment method is as follows: denitrification tank 260, nitrification tank 270, membrane separation raw water tank 280, secondary nitrification tank 290, and secondary denitrification. A tank 300, a re-aeration tank 310, and a settling basin 320 are installed, and the treatment is performed in this order. The basic principle of the treatment is based on the standard denitrification treatment method.

That is, the pretreated human waste and the like are allowed to flow into the denitrification tank 260. _{In the denitrification tank 260, NO X-} N in the circulating fluid from the nitrification tank 270 is denitrified under anaerobic conditions using BOD such as human waste. The effluent from the denitrification tank 260 flows into the nitrification tank 270, and NH _4- N is nitrified to _{NO X-N under aerobic conditions.} The _{mixed liquid containing NO X-} N is circulated to the denitrification tank 260 by the nitrifying liquid circulation pipe 271. In this treatment flow, the flow is circulated from the membrane separation raw water tank 280 to the denitrification tank 260, but a method of circulating from the nitrification tank 270 to the denitrification tank 260 may be used.

The effluent from the nitrification tank 270 is solid-liquid separated by the membrane separation device 281 via the membrane separation raw water tank 280. The permeated water separated by the membrane separation device 281 flows into the secondary nitrification tank 290 in the subsequent stage, part of the sludge concentrated by the membrane is returned to the denitrification tank 260 as return sludge, and the rest is treated as excess sludge. Will be done. The MLSS of the denitrification tank 260 and the nitrification tank 270 is often operated at 8,000 to 12,000 mg / L. Since the high-load denitrification treatment method does not use diluted water having a water temperature lower than the reaction liquid temperature, a cooling device is provided to keep the reaction tank liquid temperature at 38 ° C. or lower.

The permeated water separated by the membrane separation device 281 flows into the secondary nitrification tank 290 together with the miscellaneous wastewater. In the secondary nitrification tank 290, NH _4- N is nitrified to _{NO X-N under aerobic conditions.} The functions of the secondary denitrification tank 300, the reaeration tank 310, the settling basin 320, and the sludge return pipe 321 are the same as those of the standard denitrification treatment method. The MLSS of the secondary nitrification tank 290, the secondary denitrification tank 300, and the reaeration tank 310 is operated at 4,000 to 6,000 mg / L.

[Denitration treatment method with high mixing ratio of septic tank sludge, pre-dehydration + standard denitrification treatment method]
In the denitrification treatment method and the pre-dehydration + standard denitrification treatment method, which have a high mixing ratio of septic tank sludge, before the biological nitrification denitrification treatment, concentration of human waste after pretreatment and solid-liquid separation treatment of dehydration are performed. Remove solids. As a result, the properties of the inflow water to the biological treatment are stabilized, and the load of the biological nitrification denitrification treatment can be reduced. Further, in the case of a method of dehydrating excess sludge together with human waste after pretreatment, the sludge dewatering equipment can be unified.

FIG. 8 is a diagram showing an example of a treatment flow by the pre-dehydration + standard denitrification treatment method. As shown in the figure, the treatment flow by this pre-dehydration + standard denitrification treatment method includes a dehydrator 330, a denitrification tank 340, a nitrification tank 350, a secondary denitrification tank 360, and a re-aeration tank 370. , A settling basin 380 is installed, and processing is performed in this order. The basic principle of the treatment is based on the standard denitrification treatment method.

In the case of this treatment flow, the pre-treated human waste and the like are dehydrated by the dehydrator 330 (hereinafter referred to as pre-dehydration), and the dehydrated separation liquid flows into the denitrification tank 340. It is preferable to use an inorganic flocculant and a polymer flocculant in combination for preparing sludge during dehydration.

In the pre-dehydration treatment, since the load in the biological nitrification denitrification treatment is reduced, wastewater generated in the site such as equipment washing water is often supplied as miscellaneous wastewater without using diluted water such as well water. Since the functions after the denitrification tank 340 are the same as the treatment flow in the standard denitrification treatment method shown in FIG. 6, the description thereof will be omitted.

Examples of the aeration device used in the vitrification tank and the re-aeration tank include an aeration type aeration device, a pump circulation type aeration device, and an air injection type aeration device. The aeration device is a device that dissolves oxygen in the liquid in the tank for biologically removing BOD in urine and nitrifying nitrogen compounds, and can supply the oxygen required in the nitrification tank as uniformly and sufficiently as possible. , Sludge, sand, etc. shall not settle, and the sludge concentration in the tank shall have a stirring ability to maintain sufficient uniformity for practical use. In the nitrification tank, in addition to removing BOD in human waste, ammonia nitrogen is nitrified, so a much larger amount of oxygen is required for the same amount of human waste treated than in the aeration tank of the general activated sludge method. In addition, in order to keep the total nitrogen-MLSS load and the aerobic sludge age within the required range, it is necessary to maintain a high MLSS concentration. Therefore, the aeration device must be capable of sufficiently supplying the necessary oxygen to the liquid in the tank having a high MLSS concentration, and also requires a large amount of oxygen as described above, thus saving energy. From this point of view, a product with high oxygen dissolution efficiency is required.

In the aeration type aeration device, the air sent from the blower through the air supply tube is discharged into the liquid in the tank by the aeration device, and the inside of the tank is agitated and oxygen is dissolved at the same time. The air diffuser makes the air sent from the blower into fine bubbles and blows them into the nitrification tank, and the air lift effect of the bubbles rising toward the water surface forms a swirling flow in the tank to stir and mix the liquid in the tank. And the oxygen is dissolved by the contact between the liquid and the air bubbles. The air injection type aeration device also supplies air to the aeration tank by a blower. In the pump circulation method, air is supplied to the aeration tank by sucking air with an ejector or the like in the pump circulation flow path. The amount of air is controlled by adjusting the valve opening in the piping and controlling the output by the inverter of the blower or pump, but the power reduction effect by the output control by the inverter is large.

9 is a schematic configuration diagram showing an example of an aeration type aeration device 400, FIG. 10 is a schematic configuration diagram showing an example of a pump circulation type aeration device 430, and FIG. 11 is a schematic configuration diagram showing an example of an air injection type aeration device 460. Is. The aeration type aeration device 400 shown in FIG. 9 has a configuration in which the air sent from the blower 405 to the tank (nitrification tank or the like) 401 via the air supply pipe 407 is discharged into the liquid in the tank by the air diffuser 403. ing. In the pump circulation type aeration device 430 shown in FIG. 10, the liquid in the tank (nitration tank or the like) 431 is taken out to the circulation pump pipe 435 and circulated by the circulation pump 433, and at the same time, the liquid is circulated in the circulation pump pipe 435 on the downstream side of the circulation pump 433. Air is taken into the liquid circulated by the installed ejector 437, and bubbles of this air are supplied into the tank 431. In the air injection type aeration device 460 shown in FIG. 11, the air sent from the blower 463 through the air supply pipe 465 into the tank (nitrification tank or the like) 461 is put into the liquid in the tank as bubbles rotating by the rotating air separator 467. It is configured to be released. In addition to this rotary air dispersion type, the air injection type aeration device includes a draft tube type, a pressurized aeration type, a deep shaft type, and the like.

NH ₄ sensor 100 described above is installed for the purpose of grasping the NH ₄ -N concentration of the nitrification tank, its installation location is preferably NH ₄ -N concentration can grasp the position of the nitrification tank, nitrification tank (terminal (Preferably), or in the nitrification liquid circulation pipe, in the water quality measuring instrument installation tank (not shown) installed at the branch position of the nitrification liquid circulation pipe, or in the circulation pump pipe 435 of the pump circulation type air exposure device 430, or circulation. It is preferable to use a water quality measuring instrument installation tank (not shown) in which the pump pipe 435 is branched, a water quality measurement pipe (not shown) provided separately, or a water quality measuring instrument installation tank (not shown) in which the water quality measurement pipe is branched. The state in which the _{NH 4} sensor is installed is also called the " _{NH 4 sensor in the nitrification tank").}

NH ₄ pH meter or DO meter other than the sensor can also be placed in the same position as the NH ₄ sensors. By the way, a diaphragm polaro type DO meter or an optical DO meter is used as the DO meter, and it is possible to perform good DO measurement even for the soluble evaporation residue and / or the wastewater having a high potassium ion concentration, which is the subject of the present invention. is there.

In the high-load denitrification treatment method shown in FIG. 7, the NH ₄ sensor can also be installed in the secondary nitrification tank 290. However, since many overwhelmingly air amount in the nitrification tank 270 than in the secondary nitrification tank 290, the air amount reduction effect by NH ₄ sensor installation is largely overwhelmingly contribution NH ₄ sensors installed in the nitrification tank 270 ..

The wastewater treatment method according to the present invention is a method of controlling the amount of air according to the _{NH 4- N measurement value by the NH 4} sensor of the nitrification tank. Specifically, when the value measured by the NH ₄ sensor is larger than the value set in the nitrification tank NH _4- N set to a predetermined value, it is supplied to the nitrification tank by controlling the output of an inverter such as a blower by the aeration device. _{If the value measured by the NH 4} sensor is smaller than the predetermined value of the nitrification tank NH _4- N, the amount of air supplied to the nitrification tank is controlled by the inverter output control of the blower or the like by the aeration device. Control to reduce. As a result, the NH _4- N concentration of the _{liquid to be treated in the nitrification tank becomes the NH 4-} N set concentration of the nitrification tank.

In addition, the DO value of the nitrification tank changes according to the amount of air supplied to the nitrification tank, and when the amount of air supplied to the nitrification tank is increased, the DO value of the nitrification tank tends to be high and is supplied to the nitrification tank. When reducing the amount of air to be used, the DO value of the nitrification tank tends to be low.

NH ₄ During the nitrification reactor NH ₄ -N measurement at the sensor, in addition to the nitrification tank NH ₄ -N setpoint, set the nitrification tank NH ₄ -N alarm value is higher than the nitrification tank NH ₄ -N setpoint It is preferable to do so. This is because _{the measured value of NH 4-} N in the nitrification tank _{exceeds the set value of NH 4-} N in the nitrification tank, and the amount of air supplied to the nitrification tank increases, even though a sufficient amount of air is supplied to the nitrification tank. If the NH _4- N in the nitrification tank gradually increases and _{reaches the NH 4-} N alarm value in the nitrification tank, the nitrogen concentration of urine, etc. that flows into the nitrification tank is high, or the urine, etc. that flows into the biological reaction tank. It is considered that the nitrogen load in the biological reaction tank is high due to the high flow rate of. In such a case, the nitrogen load in the biological reaction tank is reduced by reducing the inflow of urine, etc. that flows into the reaction tank, and the nitrogen load in the biological reaction tank is adjusted so that the nitrification tank NH _4- N becomes the nitrification tank NH ₄ This is because the value can be lower than the -N alarm value, and stable biological nitrification and denitrification treatment can be continued. On the other hand, when the same operation is performed with the conventional DO control, when the nitrogen load flowing into the reaction tank becomes high, the DO in the nitrification tank drops below a predetermined value, so that the amount of air in the nitrification tank is increased. Restore DO in the nitrification tank. However, if the nitrogen load into the reaction vessel exceeds the capacity of the nitrifying bacteria, the NH _4- N flowing into the nitrifying vessel cannot be completely nitrified into _{NO X- N, and NH 4-} N remains. Regardless, since the amount of air required for nitrification is supplied, the DO of the nitrification tank may be maintained at 2 mg / L or more. Therefore, it is difficult for DO control to cope with the inflow nitrogen load into the reaction vessel, which may lead to deterioration of the treated water quality. From this point of view, as in the present invention, the NH _4- N of the _{nitrification tank is monitored by the NH 4} sensor, and the nitrogen load flowing into the reaction tank is appropriately adjusted to perform the biological nitrification denitrification treatment. Stabilization is preferable in terms of operation management.

In the conventional DO control, the DO value of the nitrification tank was maintained at 2 to 3 mg / L, and almost all ammoniacal nitrogen was oxidized to nitrate nitrogen. On the other hand, according to the present invention, since the amount of air can be controlled by the concentration of ammoniacal nitrogen, a stable nitrification reaction can be achieved even if the DO value of the nitrification tank is 1 mg / L or less. It was confirmed that when the DO value of the nitrification tank was 1 mg / L or less in the urine treatment, a denitrification reaction occurred at the same time as the nitrification reaction in the nitrification tank, and NO _{X-N in the nitrification tank was clearly reduced as compared with the conventional method.} In the urine treatment, the liquid temperature in the reaction tank is as high as 25 to 38 ° C, and the MLSS concentration is as high as 6,000 to 20,000 mg / L. Conceivable. When the nitrification reaction and the denitrification reaction proceed in the nitrification tank, the concentration of _{NH 4-} N + NO _{X-N flowing out from the nitrification tank decreases.} As a result, it becomes possible to reduce the amount of methanol required in the secondary denitrification tank after the nitrification tank.

_{Simultaneous progress of nitrification and denitrification in the nitrification tank can be achieved by installing an NH 4} sensor in the nitrification tank and controlling the ammonia nitrogen concentration in the nitrification tank as in the present invention. When nitrification and denitrification proceed simultaneously in the nitrification tank, there is a risk of residual ammoniacal nitrogen in the nitrification tank, and there is a high possibility that the quality of treated water will deteriorate. _{In addition, the NO X-} N concentration of the inflow water into the secondary denitrification tank is measured with a nitric acid sensor, and the amount of methanol injected into the secondary denitrification tank is controlled to control the amount of methanol injected into the secondary denitrification tank. It is expected that the amount of methanol used will be further reduced in order to optimize the amount of nitrogen used.

_{The method of installing the NH 4} sensor in the nitrification tank of the present invention and controlling the amount of air by the ammonia nitrogen concentration in the nitrification tank is the nitrification method in which the NH ₄ sensor 100 is installed as in the high-load denitrification treatment method shown in FIG. When applied to a flow equipped with a secondary nitrification tank 290 and a secondary denitrification tank 300 after the tank 270, the NH remaining at the nitrification tank outlet even if _{the NH 4-N setting value of the nitrification tank 270 is increased. Since 4-} N is removed in the secondary nitrification tank 290 and the secondary denitrification tank 300 in the subsequent stage, the effect on the discharged water quality is small.

On the other hand, in the standard denitrification treatment method and the pre-dehydration + standard denitrification treatment method, NH _4- N remaining at the outlet of the nitrification tank can cause an increase in the nitrogen concentration of the discharged water. In other words, since the treatment flow consists of a denitrification tank, a nitrification tank, a secondary denitrification tank, and a re-absorption tank, NH _{4-remaining at the nitrification tank outlet depending on the ammonia concentration set value in the nitrification tank. This NH 4-} N + NO because N is not removed in the secondary denitrification tank and remains in the discharged water in a state where part or all _{of NH 4- N is nitrified to NO X-N in the re-absorption tank.} There is a possibility that the nitrogen concentration of the discharged water will be increased by the amount of _{X-N concentration.}

_{An NH 4} sensor is installed in the nitrification tank of the present invention in the standard denitrification treatment method or pre-dehydration + standard denitrification treatment method, the amount of air is controlled by the ammonia nitrogen concentration in the nitrification tank, and the DO value of the nitrification tank is 1 mg /. When the method is applied in which the concentration is set to L or less, the nitrification reaction and the denitrification reaction proceed in the nitrification tank, and the _{concentration of NH 4-} N + NO _X- N flowing out from the nitrification tank is reduced, the function of the nitrification tank may be divided. That is, as shown in FIGS. 20A and 21A, the nitrification tank is functionally divided into a nitrification tank (1) and a nitrification tank (2), and the nitrification tank (1) is divided into ammonia in the nitrification tank. The amount of air is controlled by the concentration of sex nitrogen, the DO value of the nitrification tank is set to 1 mg / L or less, and the _{concentration of NH 4-} N + NO _X- N flowing out of the nitrification tank as the nitrification reaction and denitrification reaction proceed in the nitrification tank is controlled. It will be a "nitrification denitrification simultaneous progress zone" to reduce, and a "nitrification zone" in which the nitrification tank (2) is maintained at a DO value of 1 to 3 mg / L and almost all nitrification nitrogen is oxidized to nitrate nitrogen. Since the nitrate nitrogen remaining at the outlet of the nitrification tank (2) is removed by denitrification in the secondary denitrification tank, the effect on the nitrogen concentration of the discharged water is small.

The division of the nitrification tank (1) and the nitrification tank (2) is performed in addition to the case where the tank is partitioned by the tank wall and the case where the tank is structurally divided by a partition for giving structural strength to the tank. As shown in 20 (b) and 21 (b), zones with different DO concentrations can be created by adjusting the amount of air and changing the model of the air diffuser, even if they are not structurally divided by the tank wall or partition. It may be functionally divided by forming. In short, at least the nitrification tank may be functionally divided.

The tank capacities of the nitrification tank (1) and the nitrification tank (2) are such that the nitrification tank (1) <nitrification tank (2) can also exert the effect of the present invention, but the nitrification tank (1)> nitrification tank (2). This is preferable because the effect of reducing _{the NH 4-} N + NO _X- N concentration in the outflow of the nitrification tank (1) due to the simultaneous progress of the nitrification reaction and the denitrification reaction in the nitrification tank (1) of the present invention is increased. It is more preferable that the nitrification tank (2) is one-third or less of the nitrification tank (1).

The NH ₄ sensor is preferably installed at the end of the nitrification tank (1), and the DO meter is preferably installed at the nitrification tank (2). Further, it is more preferable to install a DO meter in the nitrification tank (1).

When the nitrifying liquid is circulated, it is preferable to take the nitrifying liquid from the nitrifying tank (2).

In the denitrification treatment method and the pre-dehydration + standard denitrification treatment method, which have a high mixing ratio of septic tank sludge, before the biological nitrification denitrification treatment, concentration of human waste after pretreatment and solid-liquid separation treatment of dehydration are performed. Remove solids. In this solid-liquid separation, especially in the dehydration treatment, the organic matter is removed at the same time as the solid matter is removed. Therefore, in the separation liquid after the solid-liquid separation, the organic matter used as a hydrogen donor in the denitrification treatment is used with respect to the nitrogen concentration. Insufficient, usually requires excessive addition of a hydrogen donor such as methanol to the denitrification tank or secondary denitrification tank.

The required amount of hydrogen donor during denitrification treatment with respect to nitrogen concentration is often indicated by the BOD / N ratio, and generally, the organism has a BOD / N ratio of 3 or more and does not supply an external hydrogen donor. Biochemical oxygen demand treatment is performed.

In the separation solution after dehydration of human waste, etc., or in the case of dehydrating excess sludge together with urine, etc. (hereinafter, both are collectively referred to as the dehydration separation solution of human waste, etc.), the nitrogen concentration is subject to denitrification treatment. Since the hydrogen donor BOD / N ratio of human waste is 3 or less, and in many cases 2 or less, it is necessary to add an excessive amount of hydrogen donor such as methanol.

When the present invention is applied to the pre-dehydration + standard denitrification treatment method, the nitrification reaction and the denitrification reaction by endogenous denitrification proceed simultaneously in the nitrification tank, so that the BOD / N ratio of the dehydration separation solution such as urine is increased. Even if it is low, the _{effect of reducing the NH 4-} N + NO _{X- N concentration at the nitrification tank outlet can be exhibited, so the NH 4-} N + NO _X- N nitrogen concentration at the nitrification tank outlet using the conventional pre-dehydration + standard denitrification treatment method. The amount can be reduced, and the amount of hydrogen donor such as methanol added to the denitrification tank or the secondary denitrification tank can be reduced.

_{Even when operating with the nitrification tank NH 4-} N set value, which is the standard for air volume control, the DO of the nitrification tank may be 1 mg / L or more. Even in this case, stable biological nitrification and denitrification treatment can be performed without any problem, but the nitrogen load in the biological reaction tank is reduced by reducing the flow rate of urine, etc. that flows into the biological reaction tank under these conditions. The amount of air in the nitrification tank for operating at a predetermined nitrification tank NH _4- N value can be reduced, and the DO of the nitrification tank can be kept at 1 mg / L or less. That is, by lowering the human waste etc. flow entering the biological reactor, while maintaining a nitrification tank NH ₄ -N nitrification tank NH ₄ -N setting value, the DO of the nitrification tank can be below 1 mg / L, The nitrification reaction and denitrification reaction can proceed in the nitrification tank, and the concentration of _{NH 4-} N + NO _{X-N flowing out of the nitrification tank can be reduced.}

_{In addition, a nitrification tank NH 4- N set value (2) higher than the nitrification tank NH 4-} N set value (1), which is the standard for controlling the amount of air, is set, and the nitrification tank NH _4- N set value (1) is used. If a situation you are driving nitrification DO is equal to or greater than 1 mg / L, by changing the nitrification tank NH ₄ -N settings to nitrification tank NH ₄ -N setpoint (2), a predetermined nitrification tank NH ₄ - The amount of air in the nitrification tank for operating at the N value can be reduced, and the DO of the nitrification tank can be kept below 1 mg / L. Therefore, while keeping the nitrification tank NH ₄ -N nitrification tank NH ₄ -N setting value, the DO of the nitrification tank can be below 1 mg / L, since the nitrification and denitrification reaction proceeds in the nitrification tank, It is possible to reduce the concentration of _{NH 4-} N + NO _X- N flowing out of the nitrification tank. Here, the nitrification tank NH _4- N setting has been described as two stages, but the nitrification tank NH _4- N setting value can be set in multiple stages of three or more stages.

In the whole invention of the present application, the NH _4- N set value of the nitrification tank is appropriately set in consideration of the discharged water quality, the effect of reducing the amount of air, the stirring condition in the nitrification tank, the value of the nitrification tank DO, the effect of reducing the amount of methanol used, and the like. It is preferable to do so.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

<Preliminary study 1: NH ₄ sensor performance measurement>
The measured values _{of the NH 4} sensor when human waste after pretreatment was treated by the membrane separation high-load denitrification treatment method shown in FIG. 7 were examined.

The main water quality (mean value) of the water to be treated was NH _4- N: 1,000 mg / L and BOD: 4,000 mg / L. The inflow water volume was 30 m ³ / d, and the nitrifying solution circulation volume was 600 m ³ / d. The MLSS of the nitrification tank 270 was 12,000 mg / L, and the water temperature of the nitrification tank was 35 ° C. _{NH 4- N was measured by the NH 4} sensor 100 of the nitrification tank 270 and compared with the result of the water quality analysis conducted separately. At this time, the concentration of the soluble evaporation residue in the nitrification tank 270 was 2,000 to 4,000 mg / L, and the concentration of potassium ion was 150 to 350 mg / L. FIG. 12 is _{a diagram showing a comparison between the NH 4} sensor measurement value and the water quality analysis result. As shown in the figure, since the _{measured values of the NH 4} sensor and the water quality analysis results are almost the same, the NH ₄ sensor 100 shown in FIGS. 1 to 5 has a high concentration of soluble evaporation residue and a high concentration of K +. It was confirmed that it is applicable to wastewater.

<Preliminary study 2: NH ₄ sensor performance measurement>
_{NH 4} sensor 100 in wastewater with high solubility residue concentration and K + concentration when human waste after pretreatment is treated by the membrane separation high load denitrification treatment method shown in FIG. 7 as in Preliminary Study 1. We examined the application of. _{That is, NH 4- N was measured by the NH 4} sensor 100 of the nitrification tank 270 at the A treatment plant, the B treatment plant, and the C treatment plant described below, and compared with the results of the water quality analysis conducted separately.
Treatment plant A: Same as in Preliminary Study 1, urine treatment facility, nitrification tank 270 has a soluble evaporation residue concentration of 2,000 to 4,000 mg / L and a potassium ion concentration of 150 to 350 mg / L.
Treatment plant B: Soluble evaporation residue concentration in urine treatment facility, nitrification tank is 3,000 to 6,000 mg / L, potassium ion concentration is 300 to 450 mg / L
Treatment plant C: Final disposal site Leachate treatment facility, concentration of soluble evaporation residue in nitrification tank is 10,000 to 20,000 mg / L, concentration of potassium ion is 10 to 40 mg / L

The result is shown in FIG. _{As shown in the figure, the NH 4} sensor measurement values and the water quality analysis results were almost the same at all of the A treatment plant, B treatment plant, and C treatment plant. In the B treatment plant where the potassium ion concentration was high, NH _4- N was 5 mg / L or less, and the NH _4- N sensor measurement value tended to be high, but it was within the range that did not hinder the operation management. _{As a result, it was confirmed that the NH 4} sensor 100 shown in FIGS. 1 to 5 can be applied to wastewater having a high concentration of soluble evaporation residue and a high concentration of K +.

<Example 1: Example of air volume control by _{nitrification tank NH 4-N concentration>}
The pretreated human waste and septic tank sludge were treated by the standard denitrification treatment method shown in FIG. Measurement of NH ₄ -N concentration was with NH ₄ sensors 100 shown in FIG. 1 to FIG. The main water quality (mean value) of the water to be treated (target water) was NH _4- N: 500 mg / L and BOD: 2,000 mg / L. The amount of inflow water was 60 m ³ / d, the amount of diluted water was 140 m ³ / d, the amount of nitrified liquid circulation was 300 m ³ / d, and the amount of returned sludge was 200 m ³ / d. The MLSS of the nitrification tank 220 was set to 6,000 mg / L, and the water temperature of the nitrification tank was set to 29 to 31 ° C. Then, the amount of air to the nitrification tank 220 was controlled by _{the NH 4} sensor 100 of the nitrification tank 220 so that the NH _{4-N of the nitrification tank 220 was 1 mg / L.}

FIG. 14 is a diagram showing the result of an air amount control operation based on the NH _{4- N concentration using the NH 4 sensor 100.} As shown in the figure, the result of the air volume control operation by the NH _{4- N concentration using the NH 4 sensor 100 is the nitrification tank NH 4-} N: 0.6 to 1.3 mg / L (average 1.0 mg / L), nitrification. Tank DO: 0.7 to 1.8 (average 0.9 mg / L). From this, _{by performing the air amount control operation based on the NH 4- N concentration using the NH 4} sensor 100, the DO value lower than that of the conventional method, that is, the progress of the good nitrification reaction in the nitrification tank 220 with a small amount of air. Was confirmed to be achievable.

<Example 2: _{Comparison of air volume control by nitrification tank NH 4-} N concentration and nitrification tank DO concentration>
A comparison was made between air volume control based on the nitrification tank NH _4- N concentration (invention of the present application) and air volume control based on the nitrification tank DO concentration (conventional method).

The pretreated human waste and septic tank sludge were treated by the standard denitrification treatment method shown in FIG. The main water quality (mean value) of the liquid to be treated (target water) was NH _4- N: 500 mg / L and BOD: 2,000 mg / L. The amount of inflow water was 60 m ³ / d, the amount of diluted water was 140 m ³ / d, the amount of nitrified liquid circulation was 300 m ³ / d, and the amount of returned sludge was 200 m ³ / d. The MLSS of the nitrification tank 220 was 6,000 mg / L, and the water temperature of the nitrification tank was 29 to 31 ° C.

FIG. 15 is a diagram showing a comparison between the results of air amount control based on _{the nitrification tank NH 4-N concentration and air amount control based on the nitrification tank DO concentration.} The condition (1) shown in the figure is the result of the first embodiment, and _{the air to the nitrification tank 220 is adjusted so that the NH 4-} N concentration of the nitrification tank 220 becomes 1 mg / L by _{the NH 4} sensor 100 of the nitrification tank 220. The measurement results of various numerical values when the amount is controlled are shown. Similarly, the condition (2) according to the present invention shows the measurement results of various numerical values when the amount of air to the nitrification tank 220 is controlled so that _{the NH 4-N concentration of the nitrification tank 220 is 2 mg / L.} On the other hand, under the condition (3) by the conventional method, the measurement results of various numerical values when the DO value of the nitrification tank 220 is set to 2 mg / L and the amount of air is controlled are shown. The comparison condition (4) shows the measurement results of various numerical values when the DO value of the nitrification tank 220 is set to 0.9 mg / L and the amount of air is controlled. The NH ₄ sensor 100 and the DO total 223 were installed at the same location under each condition.

_{As shown in FIG. 15, the concentration of NH 4-} N in the nitrification tank under the conditions (1) and (3) was about 1 mg / L or less, and good progress of nitrification was confirmed. Under condition (3), NH _4- N may remain due to insufficient air volume. Under condition (4), the average value was 6 mg / L, but it reached a maximum of 30 mg / L, causing deterioration of the treated water quality. Under condition (2), the _{concentration of NH 4-} N in the nitrification tank was 2 mg / L as set. Since the nitrification tank NH _4- N was stable at 2 mg / L, the effluent water quality standard value was fully satisfied. The amount of air in the nitrification tank 220 was about 10% less in the condition (1) than in the condition (3). The value of the nitrification tank NO _X- N was lower than that of the condition (3) under the condition (1) and the condition (2). This is considered to be the effect of simultaneous nitrification and denitrification in the nitrification tank 220 because the DO value was as low as 0.8 to 0.9 mg / L on average. _{Further, under the condition (2) in which the NH 4-} N set value of the nitrification tank 220 was higher than that of the condition (1), the amount of air in the nitrification tank was small and the nitrification tank DO was low. Under the condition (2) in which the nitrification tank DO was lower than that in the condition (1), the denitrification reaction was more likely to proceed, so that the value of the _{nitrification tank NO X-N was lower.} Further, under the condition (1), the nitrification tank DO value is 0.7 to 1.8 mg / L, and even if the DO value of the nitrification tank 220 is not always 1 mg / L or less, nitrification in the nitrification tank 220 is an average value during the period. Simultaneous denitrification was confirmed. _{Under the conditions (1) and (2) where the NO X-} N of the nitrification tank 220 is low, the amount of methanol used in the secondary denitrification tank 230 is reduced, so that the chemical cost can be reduced.

<Example 3: _{Comparison of air volume control by nitrification tank NH 4-} N concentration and nitrification tank DO concentration>
As shown in FIG. 7 (membrane separation high load denitrification treatment method / high load denitrification treatment method), the secondary nitrification tank 290 and the secondary denitrification tank are located after the nitrification tank 270 in _{which the NH 4 sensor 100 is installed.} in the flow equipped with 300, with NH ₄ be enhanced -N setpoint, NH ₄ -N is in the subsequent stage the secondary nitrification tank 290 and secondary denitrification tank 300 remaining in the nitrification tank outlet of the nitrification tank 270 Since it is removed, it has little effect on the quality of discharged water.

Then, in Example 3, in the treatment flow shown in FIG. 7, the water quality of the nitrification tank and the amount of air _{in the nitrification tank according to the NH 4-N set value of the nitrification tank 270 were compared.} Under the same operating conditions as in the preliminary study 1, the conditions (5) to (7) shown in FIG. 16 are _{the measurement results under the air amount control by the NH 4-} N concentration (invention of the present application), and the condition (8) is the DO concentration. The measurement result by the air amount control (conventional method) by the above is shown. As shown in the figure, under the conditions (5) to (7), the concentration of the _{nitrification tank NH 4-} N + NO _{X-N was lower than that under the condition (8).} Since the DO value was low, it is considered that this is the effect of simultaneous nitrification and denitrification in the nitrification tank 270. It was suggested that there is an optimum nitrification tank NH _4- N that reduces the concentration of nitrification tank NH _4- N + NO _{X-N. By reducing NH 4-} N + NO _X- N in the nitrification tank, the amount of methanol used in the secondary denitrification tank 300 can be reduced.

<Example 4>
The pre-treated human waste and the like were operated under the conditions of Cases 1 and 2 below at the A treatment plant where the human waste and the like after the pretreatment were treated by the membrane separation high-load denitrification treatment method shown in FIG. The main water quality (mean value) of the target water was NH _4- N: 1,000 mg / L and BOD: 4,000 mg / L. The inflow water volume was 36 m ³ / d, and the nitrifying solution circulation volume was 720 m ³ / d. The MLSS of the nitrification tank 270 was 12,000 mg / L, and the water temperature of the nitrification tank was 35 ° C. When the _{amount of air to the nitrification tank 270 was controlled so that the NH 4- N of the nitrification tank 270 was 1 mg / L with the NH 4} sensor 100 of the nitrification tank 270, the DO value of the nitrification tank 270 was about 1.5 mg / L. there were.

Case 1: When the DO value of the nitrification tank 270 is set to 1 mg / L or less by reducing the flow rate of human waste that flows into the biological reaction tank. As shown in FIG. 17, the NH _4- N setting value of the nitrification tank 270 is Without changing at 1 mg / L, the flow rate of human waste, etc. flowing into the biological reaction tank is gradually increased in the ^{period (1): 36 m 3} / d, the period (2) 33 m ³ / d, and the period (3) 32 m ^{3 / d.} By lowering it, the operation of maintaining the DO value of the nitrification tank 270 at 1 mg / L or less was performed. The amount of nitrified liquid circulating was set to 20 times the flow rate of human waste flowing into the biological reaction tank. The DO value of the nitrification tank 270 is about 1.5 mg / L in the period (1), 1.1 to 1.3 mg / L in the period (2), 0.7 to 1.0 mg / L in the period (3), and nitrification in the period (3). The DO value of the tank could be maintained below 1 mg / L. _{In period (3), the effect of reducing NH 4-} N + NO _X- N can be expected by the simultaneous progress of nitrification and denitrification in the nitrification tank 270.

Case 2: When the NH _4- N setting value of the nitrification tank 270 is increased and the DO value of the nitrification tank 270 is set to 1 mg / L or less. _{Nitrification by gradually increasing the NH 4-} N setting value of the nitrification tank 270 in the period (4): 1 mg / L, period (5) 1.5 mg / L, and period (6) 2 mg / L without change. The operation was performed to maintain the DO value of the tank 270 at 1 mg / L or less. The DO value of the nitrification tank 270 is about 1.5 mg / L in the period (4), 1.1 to 1.4 mg / L in the period (5), 0.7 to 1.0 mg / L in the period (6), and nitrification in the period (6). The DO value of the tank could be maintained below 1 mg / L. _{In period (6), the effect of reducing NH 4-} N + NO _X- N can be expected by the simultaneous progress of nitrification and denitrification in the nitrification tank 270.

<Example 5>
Air volume control by nitrification tank DO concentration (conventional method), _{air volume control by nitrification tank NH 4-} N concentration (see the present invention, FIG. 6), and nitrification tank functionally by DO concentration in the standard denitrification treatment method. , A comparison was made with an air amount control method (invention of the present application, see FIG. 20) that divides into a "nitrification denitrification simultaneous progress zone" and a "nitrification zone".

The pretreated human waste and septic tank sludge were treated by the standard denitrification treatment method shown in FIG. The main water quality (mean value) of the water to be treated (target water) was NH _4- N: 500 mg / L and BOD: 2,000 mg / L. The amount of inflow water was 50 m ³ / d, the amount of diluted water was 140 m ³ / d, the amount of nitrified liquid circulation was 300 m ³ / d, and the amount of returned sludge was 200 m ³ / d. The MLSS of the nitrification tank 220 was set to 6,000 mg / L, and the water temperature of the nitrification tank was set to 29 to 31 ° C. Measurement of NH ₄ -N concentration was with NH ₄ sensors 100 shown in FIG. 1 to FIG.

Under the condition (9) of the conventional method, the amount of air in the nitrification tank was set so that the DO of the nitrification tank was 3 mg / L.

Under condition (10), the amount of air was adjusted so that _{the NH 4-N concentration in the nitrification tank was 5 mg / L.}

Under condition (11), about two-thirds of the first half of the nitrification tank is designated as a "nitrification denitrification simultaneous progress zone" (hereinafter, also referred to as nitrification tank (1)), and the NH _4- N concentration at the end of the nitrification tank (1). The amount of air is adjusted to 5 mg / L, and the latter half of the nitrification tank is designated as the "nitrification zone" (hereinafter, also referred to as nitrification tank (2)), and the DO of the nitrification tank (2) is 2 mg. Adjusted to be / L. As shown in FIG. 20 (b), the nitrification tank (1) and the nitrification tank (2) have no structural divisions or partitions, and are functionally divided due to the difference in the amount of air.

In condition (9), a DO meter was installed in the nitrification tank. Under condition (10), an NH ₄ sensor was installed in the nitrification tank as shown in FIG. Under the condition (11), as shown in FIG. 20 (b), the NH ₄ sensor was installed in the nitrification tank (1) and the DO meter was installed in the nitrification tank (2). In condition (10) and condition (11), a DO meter was also installed at the location where the _{NH 4 sensor was installed to monitor DO.}

Since most of the nitrification tank outlet NO _X- N was NO _3- N, the amount of methanol injected into the secondary denitrification tank was set according to the _{nitrification tank outlet NO 3-N concentration.}

From the measured value of the nitric acid sensor installed at the outlet of the nitrification tank, methanol was injected into the secondary denitrification tank so that the amount was 3 times that of _{NO 3-N.}

The operation result is shown in FIG. Under the conditions (10) and (11) of the present invention in which the amount of air in the nitrification tank _{was adjusted by the set value of the NH 4 sensor, the effect of simultaneous nitrification and denitrification in the nitrification tank caused NH 4-} N at the outlet of the nitrification tank. The + NO _X- N concentration was reduced to about 60% of the conventional condition (9). The DO of the nitrification tank under the condition (10) was 0.7 mg / L on average, which was approximately 1 mg / L or less. The DO of the nitrification tank (1) under the condition (11) was 0.8 mg / L on average, which was approximately 1 mg / L or less. _{Under the conditions (10) and (11) that made it possible to reduce the NO X-} N concentration at the outlet of the nitrification tank, the amount of methanol injected into the secondary denitrification tank was 50 to 60% compared to the condition (9) of the conventional method. It was possible to reduce it.

Incidentally, NH ₄ -N remaining NH ₄ nitrification tank outlet in conditions of -N concentration was set to 5mg / L (10) of the nitrification tank is not removed by the secondary denitrification tank, NH ₄ re aeration tank - Since part or all of _{N remains nitrified to NO X} -N at the outlet of the settling pond, the nitrogen concentration in the discharged water may be increased by the amount of _{this NH 4-} N + NO _{X -N concentration.} ..

On the other hand, under the condition (11) in which about one-third of the latter half of the nitrification tank was set in the nitrification zone, the amount of NH _4- N remaining at the nitrification tank outlet was extremely small, and NH _4- N + NO _{X at the sedimentation basin outlet.} -N was 1 mg / L or less, and good nitrogen removal was achieved.

<Example 6>
Air volume control by nitrification tank DO concentration (conventional method), _{air volume control by nitrification tank NH 4-} N concentration (see the present invention, FIG. 8), and DO concentration in the nitrification tank in the pre-dehydration + standard denitrification treatment method. Therefore, a comparison was made with an air amount control method (invention of the present application, see FIG. 21) that is functionally divided into a "nitrification denitrification simultaneous progress zone" and a "nitrification zone".

The pre-treated human waste and septic tank sludge were treated by the pre-dehydration + standard denitrification treatment method shown in FIG. The conventional method and the present invention were compared with each other for a dehydrated separation solution obtained by aggregating mixed sludge obtained by adding excess sludge generated by biological treatment to human waste or the like with a polymer flocculant and then dehydrating it with a screw press dehydrator. The main water quality (mean value) of the dehydrated separation solution such as human waste, which is the water to be treated, was NH _4- N: 400 mg / L and BOD: 700 mg / L. _{The BOD / NH 4-} N ratio of the dehydrated isolate of urine, etc., which is the target of this treatment, is 1.75, and the organic matter used as a hydrogen donor during the denitrification treatment is insufficient for the nitrogen concentration. It is necessary to add excess methanol to the secondary denitrification tank. The amount of inflow water was 50 m ³ / d, the amount of miscellaneous wastewater was 10 m ³ / d, the amount of nitrified liquid circulation was 600 m ³ / d, and the amount of returned sludge was 200 m ³ / d. The MLSS of the nitrification tank 350 was set to 6,000 mg / L, and the water temperature of the nitrification tank was set to 31 to 33 ° C. Measurement of NH ₄ -N concentration was with NH ₄ sensors 100 shown in FIG. 1 to FIG.

Under the condition (12) of the conventional method, the amount of air in the nitrification tank was set so that the DO of the nitrification tank was 3 mg / L.

Under condition (13), the amount of air was adjusted so that _{the NH 4-N concentration in the nitrification tank was 5 mg / L.}

Under condition (14), about two-thirds of the first half of the nitrification tank is used as the nitrification tank (1) in the "nitrification denitrification simultaneous progress zone" so that the NH _4- N concentration of the nitrification tank (1) is 5 mg / L. The amount of air was adjusted so that the latter half of the nitrification tank was used as the nitrification tank (2) in the "nitrification zone", and the DO of the nitrification tank (2) was adjusted to 2 mg / L. As shown in FIG. 21 (b), the nitrification tank (1) and the nitrification tank (2) have no structural divisions or partitions, and are functionally divided due to the difference in the amount of air.

In condition (12), a DO meter was installed in the nitrification tank. Under condition (13), an NH ₄ sensor was installed in the nitrification tank as shown in FIG. Under the condition (14), as shown in FIG. 21 (b), the NH ₄ sensor was installed in the nitrification tank (1) and the DO meter was installed in the nitrification tank (2). In condition (13) and condition (14), a DO meter was also installed at the location where the _{NH 4 sensor was installed to monitor DO.}

Since most of the nitrification tank outlet NO _X- N was NO _3- N, the amount of methanol injected into the secondary denitrification tank was set according to the _{nitrification tank outlet NO 3-N concentration.}

From the measured value of the nitric acid sensor installed at the outlet of the nitrification tank, methanol was injected into the secondary denitrification tank so that the amount was 3 times that of _{NO 3-N.}

The operation result is shown in FIG. Under the conditions (13) and (14) of the present invention in which the amount of air in the nitrification tank _{was adjusted by the set value of the NH 4 sensor, the effect of simultaneous nitrification and denitrification in the nitrification tank caused NH 4-} N at the outlet of the nitrification tank. The + NO _X- N concentration was reduced to about 50% of the conventional condition (12). The DO of the nitrification tank under the condition (13) was 0.7 mg / L on average, which was approximately 1 mg / L or less. The average DO of the nitrification tank (1) under the condition (14) was 0.8 mg / L, which was approximately 1 mg / L or less. _{Under the conditions (13) and (14) that made it possible to reduce the NO X-} N concentration at the outlet of the nitrification tank, the amount of methanol injected into the secondary denitrification tank was 30 to 50% compared to the condition (12) of the conventional method. It was possible to reduce it.

Incidentally, NH ₄ -N remaining NH ₄ nitrification tank outlet in conditions of -N concentration was set to 5mg / L (13) of the nitrification reactor is not removed by the secondary denitrification tank, NH ₄ re aeration tank - Since part or all of _{N remains nitrified to NO X} -N at the outlet of the settling pond, the nitrogen concentration in the discharged water may be increased by the amount of _{this NH 4-} N + NO _{X -N concentration.} ..

On the other hand, under the condition (14) in which about one-third of the latter half of the nitrification tank was set in the nitrification zone, the amount of NH _4- N remaining at the nitrification tank outlet was extremely small, and NH _4- N + NO _{X at the sedimentation basin outlet.} -N was 1 mg / L or less, and good nitrogen removal was achieved.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of claims and the technical ideas described in the specification and drawings. It is possible. It should be noted that any configuration not directly described in the specification and drawings is within the scope of the technical idea of the present invention as long as the action and effect of the present invention are exhibited. In addition, the above description and the embodiments shown in each figure can be combined with each other as long as there is no contradiction in the purpose, configuration, and the like. Further, the above description and the description contents of each figure can be independent embodiments even if they are a part thereof, and the embodiment of the present invention is one embodiment in which the above description and each figure are combined. It is not limited to.

1 Body 2 Pressing mechanism 100 NH ₄ Sensor (liquid analyzer)
S1, S2, S3 Sensor S1 Ammonium Ion Electrode S11 Response Membrane S2 Potassium Ion Electrode S21 Response Membrane S3 Reference Electrode (Comparison Electrode)
S31 Liquid connection part L Analysis target liquid (water to be treated)
SP1, SP2, SP3 Sensor surface TS temperature sensor S12, S22, S32 Support tube S13, S23, S33 Internal liquid S1E, S2E, S3E Internal electrode (internal electrode)
210 Denitrification tank 220 Nitrification tank 221 Nitrification liquid circulation pipe 230 Secondary denitrification tank 240 Re-aeration tank 250 Sedimentation pond 251 Sewage return pipe 260 Nitrification tank 270 Nitrification tank 271 Nitrification liquid circulation pipe 280 Film separation Raw water tank 281 Film separation device 290 Secondary nitrification tank 300 Secondary denitrification tank 310 Re-aeration tank 320 Sedimentation pond 321 Sludge return pipe 330 Dehydrator 340 Denitrification tank 350 Nitrification tank 360 Secondary denitrification tank 370 Re-aeration tank 380 Sedimentation pond 400 Dispersive aeration Equipment 401 tank (nitrification tank, etc.)
403 Air diffuser 405 Blower 407 Air supply pipe 430 Pump circulation type aeration device 431 tank (nitrification tank, etc.)
433 Circulation pump 435 Circulation pump piping 437 Ejector 460 Air injection type aeration device 461 Tank (nitrification tank, etc.)
463 Blower 465 Air supply pipe 467 Rotating air separator

Claims (2)

By introducing at least 500 to 30,000 mg / L of soluble evaporation residue and / or wastewater with a potassium ion concentration of 40 to 600 mg / L from the denitrification tank into the nitrification tank, secondary denitrification tank, and reaeration tank. In a wastewater treatment method that performs biological nitrification and denitrification treatment,
As a liquid analyzer that measures the ammonia concentration in the nitrification tank, a saturated potassium chloride solution, which is an internal solution, and an Ag / AgCl electrode, which is an internal electrode that comes into contact with the internal solution, are provided in a space that communicates with the outside via a liquid junction. An ammonium ion electrode equipped with an ammonium chloride aqueous solution as an internal liquid and an Ag / AgCl electrode as an internal electrode in contact with the internal liquid in a space partitioned from the outside by a response film, and an ammonium ion electrode. Using a liquid analyzer configured to include a potassium ion electrode for measuring the potential of potassium ions used to correct potassium ion interference,
The amount of oxygen-containing gas supplied to the nitrification tank is controlled so that the ammonia nitrogen concentration in the nitrification tank measured by the liquid analyzer is 1 to 20 mg / L, and the DO value of the nitrification tank is 1 mg / L or less. A wastewater treatment method characterized in that a nitrification reaction and a denitrification reaction proceed at the same time in a nitrification tank by controlling so as to be. In the wastewater treatment method according to claim 1,
The nitrification tank is functionally divided into a plurality of pieces.
The amount of oxygen-containing gas supplied to the nitrification tank is controlled so that the ammonia nitrogen concentration in the first half of the divided nitrification tank is 1 to 20 mg / L, and the DO value of the first half of the nitrification tank is 1 mg / L or less. By doing so, the nitrification reaction and the denitrification reaction proceed simultaneously in the first half of the nitrification tank.
On the other hand, in the latter half of the divided nitrification tank, the amount of oxygen-containing gas supplied is controlled so that the DO value becomes 1 to 3 mg / L, and NH _4- N remaining in the first half of the nitrification tank is nitrified to _{NO X -N.} A wastewater treatment method characterized by the fact that.

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