JP6435108B2 - Denitrification device and method of operating denitrification device - Google Patents

Description

  The present invention relates to a denitrification apparatus that performs a denitrification reaction for decomposing nitrate nitrogen into nitrogen and carbon dioxide, and more specifically, an upward flow sludge bed reactor using granulated denitrification bacteria. The present invention relates to a denitrification apparatus having a treatment tower and a method for operating the denitrification apparatus.

  Wastewater from factories and the like contains ammonia nitrogen or nitrate nitrogen. Such drainage is not desirable if it is returned to nature as it leads to environmental destruction. Therefore, ammonia nitrogen or nitrate nitrogen is decomposed and then released to nature. And the decomposition process using microorganisms is performed for decomposition | disassembly of these nitrogen components.

  In the degradation treatment using microorganisms, nitrification treatment that decomposes ammonia nitrogen into nitrate nitrogen or nitrous oxide using aerobic bacteria, and nitrate nitrogen and nitrous oxide using nitrogen with anaerobic bacteria. In many cases, a denitrification process that decomposes into carbon dioxide is continuously performed.

  Anaerobic bacteria (denitrifying bacteria) tend to entangle with each other in an anaerobic atmosphere. A method has been proposed in which sludge containing the inoculum is acclimatized in an upward flow using this property to make the denitrifying bacteria into granules and dramatically increase the sludge concentration (Patent Document 1). This method is called an upflow sludge bed type (USB), and it is possible to make a denitrification device with a large amount of nitrate nitrogen and nitrous oxide even with relatively small equipment due to its high sludge concentration. it can.

In the denitrification reaction, when methanol is used as the carbon source, it is considered that nitrate nitrogen is decomposed by the reaction represented by the following formula (1).
^{_{6NO 3 - + 5CH 3 OH →}} 3N 2 + 5CO 2 + 7H 2 O + 6OH - ··· (1)

Further, nitrous oxide is considered to be decomposed by a reaction represented by the following formula (2).
3N ₂ O + CH ₃ OH → 3N ₂ + CO ₂ + 2H ₂ O (2)

  According to these reaction formulas, the amount of carbon source (methanol) required for nitrate nitrogen and nitrous oxide to be decomposed is determined. That is, excess methanol remains in the treated water. If a predetermined amount or more of methanol remains in the treated water, it must be removed. Therefore, the decomposition processing tank which has an aeration apparatus etc. in the back | latter stage of a denitrification tank is needed.

  However, the installation of the decomposition treatment tank is a factor of cost and location. Therefore, it is necessary to avoid adding as much carbon source as possible to the denitrification reaction. Patent Document 2 discloses a technique for directly removing methanol in treated water by aeration, etc., and reducing the amount of methanol to be mixed with the raw water to be treated if the amount of methanol exceeds a predetermined value.

Japanese Patent Application Laid-Open No. 07-290088 JP 2003-071492 A

  The fact that the amount of methanol in the treated water after the denitrification reaction has increased is presumed that the denitrification reaction did not proceed according to the equations (1) and (2). Thus, measures to reduce methanol may be correct. However, the increase or decrease in the amount of methanol in the treated water is not only due to the balance between the nitrate nitrogen amount and the methanol amount in equations (1) and (2), but also the activity of denitrifying bacteria.

  That is, there has been a problem that, based on the amount of methanol in the treated water, simply increasing or decreasing the amount of methanol introduced into the treated raw water may destroy the environment of the denitrification tank.

The present invention has been conceived in view of the above problems, and measures not only the concentration of the carbon source of the treated water but also the concentration of nitrous oxide (N ₂ O), and based on these, is added to the treated raw water It controls the amount of carbon source to be used, the amount of nutrients, and the amount of raw water fed to the denitrification tank.

More specifically, the denitrification apparatus according to the present invention is:
A conditioning tank into which the treated raw water is introduced;
PH adjusting agent addition means for adding a pH adjusting agent to the conditioning tank;
A processing tower communicated with the conditioning tank via a transfer pipe;
A drain pipe for flowing treated water discharged from the upper part of the treatment tower;
A first absorptiometer for detecting methanol in the treated water;
A second absorptiometer for detecting nitrous oxide in the treated water;
And methanol added unit and a methanol addition means for addition of methanol to the conditioning tank,
And the methanol addition means based on the output of the said first absorptiometer second absorption photometer and the pH adjusting agent adding means, adjusting Sumisho physical introduced from the conditioning tank through the transfer pipe to the treatment tower It has the controller which controls the transfer amount of raw | natural water, It is characterized by the above-mentioned.

  The denitrification apparatus according to the present invention uses methanol as a carbon source, and based on the methanol concentration in the treated water and the nitrous oxide concentration, the amount of additive to the treated raw water and the denitrification tank (in the present invention, the treatment tower) Control the feed rate (transfer rate) of raw water. Therefore, the denitrification apparatus can be operated without greatly changing the environment of the denitrifying bacteria in the denitrification tank.

  Further, since the methanol concentration and nitrous oxide concentration in the treated water are measured using an absorptiometer, it can be measured at a very high speed and can be fed back to the adjustment of the treated raw water quickly.

It is a figure which shows the structure of the denitrification apparatus which concerns on this invention. It is a figure which shows the structure of partial deformation | transformation of a denitrification apparatus. It is a figure which shows the signal line of the denitrification apparatus which concerns on this invention. It is a figure which shows the driving | running flow of the denitrification apparatus which concerns on this invention.

  Hereinafter, a denitrification apparatus according to the present invention will be described with reference to the drawings. In addition, the following description shows an example of the denitrification apparatus based on this invention, and is not limited to the following description. The following examples can be modified without departing from the spirit of the present invention.

  The denitrification apparatus 1 according to the present invention includes a conditioning tank 10, a processing tower 20, a hydrogen donor addition unit 30, and a regulator addition unit 40. The adjusting agent addition unit 40 may include a controller 50. The treated raw water 4 is introduced into the conditioning tank 10.

  The conditioning tank 10 is provided with a circulation pump 11 and a transfer pump 12. The conditioning tank 10 is also provided with a regulator addition unit 40. The circulation pump 11 is a pump for stirring the treated raw water 4 in the conditioning tank 10. Therefore, it may be replaced with a stirrer. The transfer pump 12 is disposed in a transfer pipe L <b> 1 that communicates between the conditioning tank 10 and the processing tower 20.

  In addition, the conditioning tank 10 is provided with a pH meter 13, a thermometer 14, and a heater 15.

  The adjusting agent adding unit 40 includes a pH adjusting agent adding means 41, a nutrient additive adding means 42, and a nitric acid additive adding means 43. The pH adjusting agent adding means 41 includes a pH adjusting agent tank 41a and a valve 41b. The nutrient solution adding means 42 includes a nutrient solution tank 42a and a valve 42b. The nitric acid addition means 43 includes a nitric acid tank 43a and a valve 43b. Each valve 41b, 42b, 43b is desirable if it can be opened and closed by an external signal.

  Further, the valves 41b, 42b, 43b may be replaced with pumps 41c, 42c, 43c (see FIG. 2). That is, each adjusting agent may be pumped by the pumps 41c, 42c, and 43c. In FIG. 2, the operation of each pump 41 c, 42 c, 43 c is controlled by the controller 50.

  Further, the pumps 41c, 42c, and 43c shown in FIG. 2 may be provided between the pH adjusting agent tank 41a and the valve 41b shown in FIG. 1, the nutrient tank 42a and the valve 42b, and the nitrate agent tank 43a and the valve 43b.

  The processing tower 20 has a substantially cylindrical shape or a rectangular parallelepiped. On the outside, a water jacket 21 for temperature control is provided. Water whose temperature is controlled by a temperature controller 21a is caused to flow through the water jacket 21. This is for keeping the inside of the processing tower 20 at a constant temperature. The water jacket 21 may be another heating method using a steam heat source or the like. In the present embodiment, the jacket type heating method is exemplified, but there is no particular limitation as long as the method can maintain the processing tower 20 at a constant temperature.

  A transfer pipe L <b> 1 communicating with the conditioning tank 10 is connected to the lower part of the processing tower 20. The treatment tower 20 is filled with granular denitrifying bacteria described later. A gas-solid-liquid separator 22 is provided at the upper part of the processing tower 20. The gas-solid-liquid separator 22 prevents the granular denitrifying bacteria in the processing tower 20 from being washed out, discharges the treated water 6 that has passed through the processing tower 20, and generates gas (nitrogen) in the processing tower 20. Etc.) into the atmosphere.

  The gas-solid-liquid separator 22 is provided with a drain pipe L2 for transferring the treated water 6 to the next step. In addition, a return pipe L3 for returning a part of the treated water 6 to the conditioning tank 10 is provided. The processing tower 20 may be provided with a pH meter 23 and a thermometer 24.

A hydrogen donor addition unit 30 is connected to the drain pipe L2. The hydrogen donor addition unit 30 samples a part of the treated water 6 in the drain pipe L2, nitrous oxide (hereinafter referred to as “N ₂ O”) in the treated water 6, and a hydrogen donor. A measuring device for measuring the content of (here methanol) is arranged. The measuring device is not particularly limited as long as the contents of N ₂ O and methanol can be measured.

Here, a UV absorptiometer 32 for measuring N ₂ O and an infrared absorptiometer 31 for measuring methanol are shown. The infrared absorptiometer 31 is called a first absorptiometer, and the UV absorptiometer 32 is also called a second absorptiometer.

  The hydrogen donor addition unit 30 includes a hydrogen donor addition means 33. The hydrogen donor addition means 33 includes a hydrogen donor tank 33a, a valve 33b, and a pipe 33L. The end of the pipe 33L communicates with the conditioning tank 10. The valve 33b can be controlled to open and close by an external signal.

  The valve 33b may be replaced with a pump 33c (see FIG. 2). Alternatively, the pump 33c of FIG. 2 may be provided between the hydrogen donor tank 33a of FIG. 1 and the valve 33b. That is, the hydrogen donor may be pumped by the pump 33c. It is assumed that the pump 33c is configured so that the operation stop can be controlled by an external signal. Further, the description will be continued assuming that the valves 33b, 41b, 42b, and 43b are configured so that the opening and closing can be controlled by a signal from the outside (the controller 50).

  FIG. 3 is a diagram in which each signal is written in FIG. The outputs of the UV absorptiometer 32, the infrared absorptiometer 31, the pH meter 13, the thermometer 14, the pH meter 23, and the thermometer 24 are connected to the controller 50. Then, the UV absorptiometer 32, the infrared absorptiometer 31, the pH meter 13, the pH meter 23, the thermometer 14 and the thermometer 24 represent the measured values as signal Suv, signal Sir, signal Sp13, signal Sp23, The signal St14 and the signal St24 are transmitted to the controller 50.

  The controller 50 includes instruction signals Cb33, Cb41, Cb42, Cb43, Cp12, Ch15, and Ch21, opens and closes the valves 33b, 41b, 42b, and 43b, the operation of the transfer pump 12, the heater 15, and the temperature controller. 21a is controlled.

Operation | movement of the denitrification apparatus 1 which has the above structure is demonstrated. The denitrification apparatus 1 according to the present invention treats treated raw water 4 containing nitrate nitrogen (hereinafter referred to as “NO ₃ —N”). Ammonia nitrogen (hereinafter referred to as “NH ₄ -N”) may be contained, but the denitrification apparatus 1 hardly decomposes. Therefore, when it is necessary to decompose NH ₄ -N, it is desirable to arrange an aerobic tank having an aeration device or the like in front of the denitrification device 1 and perform nitrification treatment on the raw water 4 to be treated.

  First, the processing tower 20 is filled with granular denitrifying bacteria. You may fill up to 70% of the height of the processing tower 20. That is, the denitrification apparatus 1 constitutes an upward flow sludge bed (USB) type reactor.

The granulated denitrifying bacteria may be preliminarily acclimatized elsewhere, or granules may be formed by charging the inoculum into the processing tower 20 and acclimatizing in the processing tower 20. Granules are obtained by giving NO ₃ -N and hydrogen donors including phosphorus (P) and calcium (Ca), bringing the pH to around 7 to 8.5 and maintaining the water temperature at 30 to 45 ° C. Can do.

When granulated denitrifying bacteria are formed in the treatment tower 20, the treated raw water 4 is introduced into the conditioning tank 10. In the conditioning tank 10, the pH of the treated raw water 4 is adjusted to a range of 6.5 to 9, preferably 7 to 8.5 by the pH meter 13 and the pH adjusting agent adding means 41. As the pH adjuster, sulfuric acid (H ₂ SO ₄ ) can be used when the raw raw water 4 is adjusted to the acidic side, and sodium hydroxide (NaOH) can be used when the raw water is adjusted to the alkali side.

In addition, if the activity of the denitrifying bacteria in the treatment tower 20 increases and the decomposition of NO ₃ —N proceeds, the treated water 6 exhibits alkalinity. Therefore, an alkali source can be obtained by returning a part of the treated water 6 to the conditioning tank 10. The controller 50 can adjust the pH.

  Further, the controller 50 uses the signal St14 received from the thermometer 14 and the instruction signal Ch15 transmitted to the heater 15 to set the temperature of the treated raw water 4 in the conditioning tank 10 to 20 to 45 ° C, preferably 30 to 35 ° C. Adjust to ° C. The controller 50 can adjust the water temperature of the treated raw water 4 by adjusting the thermometer 14 and the heater 15.

  The controller 50 further adds a nutrient to the treated raw water 4 by the nutrient addition means 42. Specifically, the controller 50 transmits the instruction signal Cb42 to the valve 42b of the nutrient solution adding means 42, and adds the nutrient solution to the treated raw water 4. The nutrient can include inorganic substances such as phosphorus, calcium, magnesium, iron, copper, manganese, molybdenum, zinc, and cobalt. It is desirable to increase the proportion of phosphorus and calcium. This is because it is effective for the formation of granules.

  The transfer pump 12 transfers the adjusted raw water 5 adjusted in the conditioning tank 10 to the processing tower 20 via the transfer pipe L1. The transfer pump 12 is driven by an instruction signal Cp12 from the controller 50. The flow rate of the adjusted treated raw water 5 in the processing tower 20 is determined by the transfer flow rate of the transfer pump 12 and the cross-sectional area of the processing tower 20. The hydraulic retention time (HRT) is determined by the transfer flow rate of the transfer pump 12 and the volume of the processing tower 20. That is, it can be said that the controller 50 controls the transfer amount of the adjusted treated raw water 5 introduced from the conditioning tank 10 to the treatment tower 20 via the transfer pipe L1.

Denitrifying bacteria form granules in an upward flow in an anaerobic environment. The granule is a mass of denitrifying bacteria, and the sludge concentration can be made higher than when the denitrifying bacteria are supported on the inorganic support. The granules in Le shaped upflow sludge bed reactor using a denitrifying bacteria, can be decomposed almost close to 100% of the NO 3 _-N.

In other words, as the operating state of the denitrification apparatus 1 increases the decomposition rate of NO 3 _-N close to 100%, to adjust the transfer pump 12 so as to shorten the HRT until no longer maintain its decomposition rate. By doing in this way, the nitrogen capacity load of the denitrification apparatus 1 can be obtained. Note that operating at the scale, in a single treatment tower, the nitrogen volume loading, it is desirable to design the capacity of about _{7~15 (kg-NO 3 -N /} m 3 / day).

NO ₃ —N in the adjusted treated raw water 5 introduced from the lower portion of the treatment tower 20 is decomposed while rising between the granular denitrifying bacteria. Then, water containing nitrogen, carbon dioxide, and hydroxyl groups (treated water 6) is discharged from the top of the treatment tower 20. The gas-solid-liquid separator 22 provided at the top of the processing tower 20 releases nitrogen and carbon dioxide into the atmosphere and discharges the treated water 6.

  The treated water 6 is sent to the next treatment from the drain pipe L2. A part of the treated water 6 is returned to the conditioning tank 10 via the return pipe L3. The reason why a part of the treated water 6 is returned to the conditioning tank 10 is to relieve the acidity of the treated raw water 4 with the hydroxyl groups in the treated water 6. Moreover, there is an effect that the water quality fluctuation of the adjusted treated raw water 5 flowing into the treatment tower 20 can be reduced.

The hydrogen donor addition unit 30 provided in the drain pipe L2 samples a part of the treated water 6 in the drain pipe L2. Then, the content of the hydrogen donor and the content of N ₂ O in the treated water 6 are measured. The hydrogen donor is a carbon source for denitrifying bacteria, and hydrocarbons such as methanol and acetic acid can be suitably used. Here, explanation is continued as methanol.

In the denitrification reaction, the chemical equivalent of methanol required for NO ₃ —N to be decomposed is determined. However, in practice, it is not easy to add methanol corresponding to the chemical equivalent amount due to the activity of denitrifying bacteria and the fluctuation of the amount of NO ₃ —N in the treated raw water 4. Therefore, an excessive amount of methanol is added to the conditioning tank 10. Therefore, the treated water 6 contains methanol.

The methanol concentration in the treated water 6 is adjusted to fall within the allowable lower limit value Nd to the allowable upper limit value Nu depending on the concentration allowed for the treated water 6 when the denitrification apparatus 1 is in a steady operation. The The methanol concentration can be detected by the infrared absorptiometer 31 with a wave number near 3600 cm ⁻¹ .

When the methanol concentration in the treated water 6 is higher than the allowable upper limit Nu, the amount of methanol added is excessive with respect to NO ₃ -N in the treated raw water 4 and the activity of denitrifying bacteria decreases for some reason. There may be cases. Whether or not the activity of denitrifying bacteria is reduced can be determined by examining the N ₂ O content in the treated water 6. This is because in the denitrification reaction, when denitrification is insufficient, NO ₃ —N cannot be decomposed to N ₂ , and N ₂ O that is an intermediate product is generated. N ₂ O can be measured by observing a peak near a wavelength of 190 nm with the UV absorptiometer 32.

If the methanol concentration is not less than the allowable upper limit Nu and N ₂ O is sufficiently low, the activity of denitrifying bacteria is rather active, and the amount of methanol added is excessive relative to NO ₃ -N in the treated raw water 4 I can judge. In this case, the concentration of methanol added in the conditioning tank 10 can be reduced. However, a nitric acid agent such as sodium nitrate (NaNO ₃ ) may be added to the treated raw water 4 in the conditioning tank 10 in order not to change the state in the treatment tower 20 as much as possible. The addition of the nitric acid agent can be performed by the nitric acid agent adding means 43.

Further, when the methanol concentration is higher than the allowable upper limit Nu and the amount of N ₂ O is large, it is suspected that the activity of denitrifying bacteria is reduced for some reason. In this case as well, the concentration of methanol added in the conditioning tank 10 can be reduced.

  However, it is desirable not only to reduce the methanol concentration but also to increase nutrients and optimize pH. It is because it is necessary to start over from acclimatization when the activity of denitrifying bacteria is reduced. Therefore, it is desirable to return to manual.

On the other hand, when the methanol concentration in the treated water 6 is less than or equal to the allowable lower limit Nd, the amount of methanol added is insufficient relative to NO ₃ -N in the treated raw water 4 and the activity of denitrifying bacteria is increased Can be considered.

When the concentration of N ₂ O in the treated water 6 is sufficiently low, it is considered that the treatment amount increased due to the growth of denitrifying bacteria. Therefore, the load can be increased (the amount of the transfer pump 12 can be increased).

When the concentration of N ₂ O in the treated water 6 is large, the activity of denitrifying bacteria is reduced, and it is considered that methanol is also deficient with respect to NO ₃ -N in the treated raw water 4. Therefore, it is necessary to increase the amount of methanol added and activate the denitrifying bacteria. Also in this case, if the state continues, it is returned to manual.

  The controller 50 receives signals (Suv, Sir) representing the measurement results from the UV absorptiometer 32 and the infrared absorptiometer 31 and, based on the above case classification, the valve 33b of the hydrogen donor addition means 33. The amount of methanol added to the conditioning tank 10 is increased or decreased. Further, the pH adjusting agent adding means 41 and the nutrient adding means 42 of the adjusting agent adding unit 40 are operated.

  Next, the processing of the controller 50 after steady operation will be described more specifically with reference to the flow of FIG. Note that FIG. 1 is referred to as appropriate. The start of the flow of FIG. 4 (step S100) is assumed to be a state in which the processing tower 20 is filled with granular denitrifying bacteria and the raw water for treatment 4 is decomposed into post-treatment water 6.

  In the flow of FIG. 4, the allowable upper limit Nu and the allowable lower limit Nd are determined for the methanol concentration in the treated water 6. If the methanol concentration in the treated water 6 is between the allowable lower limit value Nd and the allowable upper limit value Nu as the allowable upper limit value Nu and the allowable lower limit value Nd, the denitrification apparatus 1 is operating steadily. It is a value indicating the range that can be determined.

Further, a threshold value Tu is determined for the N ₂ O concentration in the treated water 6. This threshold Tu is a value at which it can be determined that the activity of denitrifying bacteria is reduced if the N ₂ O concentration is higher than this value. On the other hand, if the N ₂ O concentration is smaller than Tu, the denitrifying bacteria activity is a value indicating a range in which it can be determined as normal.

  When the process starts (step S100), it is determined whether or not to cancel the automatic operation (step S102). The cancellation of the automatic operation by the controller 50 may be a case where it is recognized that the activity reduction of the denitrifying bacteria has exceeded a certain level. If the carbon source (hydrogen donor) is slightly unbalanced with nitrate nitrogen or ammonia nitrogen in the treated water to be treated, the balance can be restored by automatic control.

  However, there is a case where a large decrease in activity of the denitrifying bacteria itself cannot be recovered by automatic operation. Moreover, if it is forced to recover by automatic operation, the denitrifying bacteria themselves may be killed. There are various causes of the denitrifying activity reduction, and it is often impossible to program in advance, such as removing bacteria and acclimatizing while giving nutrients. Therefore, in such a case, it is considered better to return the process to manual.

  When the automatic operation is canceled (step S150), an alarm may be given, or a process to that effect may be performed on an operation panel (not shown) of the denitrification apparatus 1.

Next, the controller 50 receives the signal Suv from the UV absorptiometer 32 and the signal Sir from the infrared absorptiometer 31 and contains nitrous oxide (N ₂ O) and methanol in the treated water 6. A rate is obtained (step S104). Then, it is determined whether or not the methanol concentration is larger than the allowable upper limit Nu (step S106).

If the concentration of methanol is higher than the allowable upper limit Nu (Y branch of step S106), it is determined whether N ₂ O is greater than a threshold value Tu (step S120). If N ₂ O is higher than the threshold value Tu (Y branch of step S120), the flow is transferred to process 1 (step S130). The fact that the flow has moved to the process 1 means that the methanol concentration is higher than the allowable upper limit Nu and the N ₂ O concentration is higher than the threshold Tu. This is considered to be a case where the supply of methanol is excessive and there is a high possibility that the activity of denitrifying bacteria is also reduced. Process 1 is a process for dealing with such a case.

  In the process 1 (step S130), it is preferable to perform a process for reducing the amount of methanol supplied and improving the activity of the denitrifying bacteria (hereinafter referred to as “denitrifying bacteria activation process step”). Means for improving the activity of denitrifying bacteria are not particularly limited, and means for supplementing nutrient sources and increasing the temperature in the processing tower 20 are conceivable. Moreover, you may perform the means of temporarily raising pH in the processing tower 20 in order to exclude miscellaneous bacteria other than denitrifying bacteria. However, since these processes become complicated, automatic control is canceled.

If the N ₂ O concentration is not higher than the threshold value Tu in step S120 (N branch of step S120), the flow moves to process 2 (step S132). The fact that the flow has moved to treatment 2 means that methanol is higher than the allowable upper limit Nu and the N ₂ O concentration is lower than the threshold Tu.

  In this case, it can be judged that the activity of denitrifying bacteria is normal. Therefore, in process 2 (step S132), the methanol concentration is suppressed.

In this case, it means that methanol is higher than the allowable upper limit Nu and the N ₂ O concentration is equal to or lower than the threshold value Tu. This is probably because the activity of denitrifying bacteria is normal and there is simply too much methanol. Therefore, in process 2 (step S132) in which the flow is transferred, the amount of methanol added is reduced. The amount of methanol added is reduced by the hydrogen donor addition means 33.

If the methanol concentration is not greater than the allowable upper limit Nu in step S106 (N branch in step S106), the flow proceeds to step S108. In step S108, it is determined whether the methanol concentration is smaller than the allowable lower limit value Nd. If the methanol concentration is smaller than the allowable lower limit value Nd (Y branch of step S108), the flow moves to step S122, and it is determined whether N ₂ O is larger than the threshold value Tu (step S122).

When N ₂ O is larger than the threshold value Tu (Y branch in step S122), the control shifts to process 3 (step S136). The fact that the flow has moved to the process 3 means that the methanol concentration is smaller than the allowable lower limit value Nd and the N ₂ O concentration is higher than the threshold value Tu.

  This may be due to the low activity of denitrifying bacteria or the lack of methanol. Therefore, in the treatment 3, it is preferable to increase the amount of methanol supplied and perform the “denitrifying bacteria activation treatment step”. However, since these processes are complicated, the automatic control is canceled (jumps to step S150).

If the N ₂ O concentration is smaller than the threshold value Tu in step S122 (N branch in step S122), the process proceeds to process 4 (step S138). When the process moves to step S138, it means that the methanol concentration is less than the allowable lower limit value Nd and the N ₂ O concentration is a normal value. This is considered that the activity of the denitrifying bacteria is normal and methanol is simply deficient. Accordingly, in process 4, the amount of methanol added is increased. The increase in the amount of methanol added is performed using the hydrogen donor addition means 33.

  If the methanol concentration in step S108 is not smaller than the allowable lower limit value Nd (N branch in step S108), the process proceeds to step S110. The process shifts to step S110 means that the methanol concentration is larger than the allowable lower limit value Nd and smaller than the allowable upper limit value Nu. That is, the methanol concentration is normal.

Step S110 checks whether or not the N ₂ O concentration is higher than the threshold value Tu. If the N ₂ O concentration is higher than the threshold value Tu (Y branch of step S110), the flow moves to process 5 (step S140). In this case, it is considered that only the activity of denitrifying bacteria is reduced. However, the cause must be examined individually and specifically. Therefore, in this case, automatic control is canceled (jumps to step S150).

  It should be noted that the processing from processing 1 to processing 5 is returned to step S102 when the work is completed. However, it takes time for the work performed in each treatment to appear as an effect in the treatment tower 20. Therefore, after shifting to each process and performing work in each process, it may be possible to wait for a certain period of time. Further, it is determined that the N branch in step S110 is normal (step S112), and the process returns to step S102 again.

As described above, the state of denitrifying bacteria in the treatment tower 20 can be estimated by detecting the concentration of methanol as the hydrogen donor (carbon source) in the treated water 6 and the concentration of N ₂ O. it can. And the environment in the processing tower 20 can be maintained so that the activity of denitrifying bacteria may be maintained.

As described above, the denitrification apparatus 1 according to the present invention detects the concentrations of methanol and N ₂ O in the treated water 6 and then controls the additive to the treated raw water 4 and the transfer pump 12. The operation can be continued without greatly changing the environment of the denitrifying bacteria in the processing tower 20.

  The denitrification apparatus according to the present invention can be suitably used not only for wastewater from factories and the like, but also for denitrification treatment of household wastewater and the like.

1 Denitrification equipment 4 Processed raw water 5 Processed raw water adjusted by conditioning tank (adjusted processed raw water)
6 Water after treatment 10 Conditioning tank 11 Pump for circulation 12 Pump for transfer 13 pH meter 14 Thermometer 15 Heater 20 Treatment tower 21 Water jacket 21a Temperature controller 22 Gas-solid-liquid separator 23 pH meter 24 Thermometer 30 Hydrogen donor addition Unit 31 Infrared absorptiometer (first absorptiometer)
32 UV absorptiometer (second absorptiometer)
33 Hydrogen donor addition means 33a Hydrogen donor tank 33b Valve 33L Piping 33c Pump 40 Adjustment agent addition unit 41 pH adjustment agent addition means 41a pH adjustment agent tank 41b Valve 41c Pump 42 Nutrition agent addition means 42a Nutrition agent tank 42b Valve 42c Pump 43 Nitric acid agent adding means 43a Nitric acid agent tank 43b Valve 43c Pump 50 Controller L1 Transfer pipe L2 Drain pipe L3 Return pipe

Claims (6)

A conditioning tank into which the treated raw water is introduced;
PH adjusting agent addition means for adding a pH adjusting agent to the conditioning tank;
A processing tower communicated with the conditioning tank via a transfer pipe;
A drain pipe for flowing treated water discharged from the upper part of the treatment tower;
A first absorptiometer for detecting methanol in the treated water;
A second absorptiometer for detecting nitrous oxide in the treated water;
A methanol addition unit having methanol addition means for adding methanol to the conditioning tank;
Adjusted treated raw water introduced from the conditioning tank to the treatment tower via the methanol addition means, the pH adjuster addition means, and the transfer pipe based on the outputs of the first and second absorptiometers A denitrification apparatus comprising a controller for controlling a transfer amount of the denitrification. Furthermore, it has a nutrient addition means and a nitrate addition means,
2. The controller according to claim 1, wherein the controller controls at least one of the nutrient solution adding unit and the nitrate solution adding unit based on outputs of the first and second absorptiometers. Denitrification device described. The operation method of the denitrification apparatus according to claim 1 or 2, wherein the raw water treated with methanol is injected from the lower part of the treatment tower filled with granular denitrification bacteria,
Detecting methanol concentration and nitrous oxide concentration in the treated water discharged from the upper part of the treatment tower;
When the methanol concentration is higher than the allowable upper limit Nu and the nitrous oxide concentration is higher than the threshold Tu, the denitrifying bacteria activation treatment step is performed to reduce the amount of methanol supplied and improve the activity of the denitrifying bacteria. A method for operating a denitrification apparatus. The operation method of the denitrification apparatus according to claim 1 or 2, wherein the raw water treated with methanol is injected from the lower part of the treatment tower filled with granular denitrification bacteria,
Detecting methanol concentration and nitrous oxide concentration in the treated water discharged from the upper part of the treatment tower;
An operation method of a denitrification apparatus, wherein the addition of methanol to the treated raw water is suppressed when the methanol concentration is higher than an allowable upper limit Nu and the nitrous oxide concentration is lower than a threshold Tu. The operation method of the denitrification apparatus according to claim 1 or 2, wherein the raw water treated with methanol is injected from the lower part of the treatment tower filled with granular denitrification bacteria,
Detecting methanol concentration and nitrous oxide concentration in the treated water discharged from the upper part of the treatment tower;
The lower than methanol concentration allowable lower limit Nd, wherein when nitrous higher than nitric oxide concentration threshold Tu, the supply amount and increase the methanol, the denitrifying bacteria of the active denitrifying bacteria activation of improving the process A method for operating a denitrification apparatus, characterized in that: The operation method of the denitrification apparatus according to claim 1 or 2, wherein the raw water treated with methanol is injected from the lower part of the treatment tower filled with granular denitrification bacteria,
Detecting methanol concentration and nitrous oxide concentration in the treated water discharged from the upper part of the treatment tower;
A method for operating a denitrification apparatus, wherein when the methanol concentration is lower than an allowable lower limit value Nd and the nitrous oxide concentration is lower than a threshold value Tu, the amount of methanol added to the treated raw water is increased.