JP3180891B2 - Wastewater treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus, and more particularly to a wastewater treatment apparatus for biologically high-speed treatment of ammonia nitrogen wastewater such as sewage.

[0002]

2. Description of the Related Art Ammoniacal nitrogen (N) contained in wastewater
H ₄ -N), the decrease in dissolved oxygen discharge point of water bodies, since it is one of substances causing eutrophication in closed water areas, the effective removal methods has become a challenge. As a method for biologically treating ammoniacal nitrogen in wastewater, a treatment method using a modified activated sludge circulation method is usually performed, and a nitrification reaction of ammonia to nitric acid by nitrifying bacteria and a nitrification reaction of nitric acid by denitrifying bacteria It uses a denitrification reaction to the soil. This method consists of two tanks, a denitrification tank in an anaerobic state and a nitrification tank in an aerobic state. The ammoniacal nitrogen in the wastewater is nitrified to nitric acid. Then, the nitrification solution that has been nitrified in the nitrification tank is circulated to the denitrification tank, whereby nitrogen components in the wastewater are released to the atmosphere as nitrogen gas and removed.

[0003] Of the nitrifying bacteria and denitrifying bacteria described above, nitrifying bacteria have a slow growth rate. Therefore, in order to maintain a considerable number of bacteria in activated sludge, the residence time of the sludge must be increased to increase the growth time. Must be secured. For this reason, in the modified activated sludge circulation method, immobilization of nitrifying bacteria is being studied in order to increase the nitrification efficiency, and a process in which the immobilized nitrifying bacteria is put into a nitrification tank has been put to practical use. The activated sludge circulation modified method is mainly applied to wastewater such as sewage, and the concentration of ammonia nitrogen in sewage is about 20 to 80 mg / l.

[0004]

However, a wastewater treatment apparatus for biologically treating wastewater such as sewage requires a large site area for the purpose of securing the residence time and the like. There is a problem that it is difficult to install in an urban area where it is difficult to secure a site area. Further, when the size of the wastewater treatment device is reduced in accordance with the small site space, the treatment capacity is reduced correspondingly.

[0005] From such a background, there has been a demand for a wastewater treatment apparatus that can be installed in a small site space without reducing the treatment capacity of ammoniacal nitrogen wastewater. The present invention
In view of such circumstances, a biological wastewater treatment apparatus capable of performing high-speed treatment of ammoniacal wastewater, thereby realizing a significant downsizing of the apparatus without reducing the treatment capacity. The purpose is to provide.

[0006]

In order to achieve the above object, the present invention provides a wastewater treatment apparatus for biologically treating an ammoniacal nitrogenous wastewater with a nitrifying bacterium which is carried on a carrier. A pretreatment concentrator for increasing the concentration of ammonia nitrogen, and an ammoniacal nitrogen concentrated water concentrated by the pretreatment concentrator, and cultured in a high-concentration ammonia solution of the type of nitrifying bacteria. AH bacteria exhibiting high activity at an ammonia nitrogen concentration of 400 mg / l or more, and nitrifying bacteria detected by culturing in a low-concentration ammonia solution; and a reaction tank for contacting, in an aerobic atmosphere, an immobilized carrier in which AL bacteria exhibiting high activity at an ammonia nitrogen concentration near 1 in a mixed phase are grown.

[0007]

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wastewater treatment apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. The present invention relates to the following types of nitrifying bacteria: AH bacteria and AL
The AH bacteria and AL bacteria necessary for understanding the present invention will be described first before explaining the wastewater treatment apparatus of the present invention, based on the knowledge that bacteria survive.

In other words, the present inventors previously put a carrier supporting nitrifying bacteria into three tanks and flow ammonia nitrogen wastewater in series into three tanks in order to speed up the nitrification treatment. When the step treatment was performed, a high digestion rate of 123 mg-N / hl-carrier was obtained. Therefore, in order to investigate the cause, nitrifying bacteria contained in the carrier were separated and the characteristics of the bacteria were examined. As a result, nitrifying bacteria can be roughly classified into nitrifying bacteria that exhibit high activity under conditions of high-concentration ammonia nitrogen atmosphere and nitrifying bacteria that exhibit high activity under conditions of low-concentration ammonia nitrogen atmosphere. Found to survive.

In order to identify these two types of nitrifying bacteria, the present inventors defined the nitrifying bacteria detected by culturing in a high-concentration ammonium sulfate solution having a concentration of 5000 mg / l for 8 weeks as AH bacteria. The nitrifying bacteria detected by culturing for 8 weeks in a low-concentration ammonium sulfate solution having a concentration of 100 mg / l were designated as AL bacteria. In order to investigate the characteristics of the AH bacteria and AL bacteria specified in this way, the nitrification rate of the carrier and the concentration of the bacteria surviving in the carrier when the culture was performed while changing the ammonia nitrogen concentration were measured in detail. The relationship shown in FIG. 2 was obtained.

FIG. 1 shows AH versus ammonia nitrogen concentration.
FIG. 2 shows the number of bacteria and the nitrification rate, and FIG. 2 shows the number of bacteria and the nitrification rate of the AL bacteria with respect to the concentration of ammonia nitrogen. The digestion rate is an important factor for determining the required volume of the aeration tank and for determining the nitrogen removal rate. The higher the digestion rate, the more compact the device. As can be seen from FIG. 1, the AH bacteria have an ammonia nitrogen concentration of 2
If it is less than 00 mg / l, the number of bacteria is small and the nitrification rate is low. However, at 400 mg / l or more, the number of bacteria increases to 2 digits or more,
The nitrification rate per carrier was more than 300 mg-N / hl·l-carrier, which was at least three times higher than that at low concentration.

On the other hand, as can be seen from FIG.
The number of bacteria is large when the ammonia nitrogen concentration is 200 mg / l or less, and the nitrification rate has a peak near 100 mg / l. In the region of 100 mg / l or less, the diffusion rate of ammonia is rate-limiting, and the apparent nitrification rate decreases.
Further, the nitrification rate decreases in the region of 100 mg / l or more, which is presumed to be caused by the poisoning of bacterial cells by ammonia.

Further, when the ammonia nitrogen concentration is 150 to 4
When cultivated in the range of 00 mg / l, multiphase propagation of AH bacteria and AL bacteria was observed, and the nitrification rate was 300 to 4
The value was as high as 50 mg-N / hl-carrier, and a synergistic effect due to the mixture of two types of bacteria was observed. In addition, since the ammonia nitrogen loading condition per carrier is important for the culture and maintenance conditions of the cells, the ammonia nitrogen loading condition is changed under the condition that the ammonia nitrogen concentration is kept constant, and the AH bacteria are changed. The characteristics of AL bacteria were examined. FIG. 3 shows that the ammonia nitrogen load per carrier is 100-600 mg-N while the ammonia nitrogen concentration is maintained at 200 mg / l.
/ Hl-carrier number when changed between carriers. FIG.
Reduces the ammoniacal nitrogen load per carrier to 100 to 60 while maintaining the ammoniacal nitrogen concentration at 500 mg / l.
The number of bacteria when the concentration was changed between 0 mg-N / hl-carrier is shown.

As can be seen from FIG. 3, when culturing at an ammonia nitrogen concentration of 200 mg / l, AH bacteria and AL
It became a mixed biota of fungi. When the ammonia nitrogen load per carrier was less than 300 mg-N / hl-carrier, the number of cells was as low as 10 ⁷ , but as the ammonia nitrogen load per carrier was increased, the number of cells became remarkable. An increase was observed. By the way, when the ammonia nitrogen load per carrier is set to 400 mg-N / h · l-carrier or more, the number of bacterial cells is at least 10 ⁸ or more and 500 mg-N / h ·
When the above l- carrier was able to be maintained at ¹⁰⁹ or more.

On the other hand, as can be seen from FIG. 4, when the cells were cultured at an ammonia nitrogen concentration of 500 mg / l, a single biota of only AH bacteria was obtained. Then, similarly to the case of FIG. 5, the ammonia nitrogen load per carrier is 300 mg-N
Below / hl-carrier, the number of cells was as low as 10 ⁷ , but as the load was increased, a remarkable increase in the number of cells was observed.

Therefore, from FIG. 3 and FIG.
Regardless of the mixed biota of bacteria or the single biota of AH bacteria alone, increasing the ammonia nitrogen load per carrier increases the bacterial cell density and consequently increases the nitrification rate per carrier. I knew I could do it. This means that, in the case of the entrapping immobilized carrier, by increasing the ammonia nitrogen load per carrier, it is possible to sufficiently supply the ammonia nitrogen, which is a nutrient source of the cells, to the inside of the carrier, so that the number of bacteria increases. It is thought that this leads to an increase in the nitrification rate per carrier.

From the above study results, the following can be said about the characteristics of AH bacteria and AL bacteria. Nitrifying bacteria can be roughly classified into AH bacteria that exhibit high activity under conditions of high-concentration ammonia nitrogen atmosphere and AL bacteria that exhibit high activity under conditions of low-concentration ammonia nitrogen atmosphere. AH bacteria are preferentially propagated in a region where the concentration of ammonia nitrogen is 400 mg / l or more, a remarkable growth of the number of bacteria is observed, and the nitrification rate is significantly increased. However, as shown in FIG. 5, in the region where the concentration of ammonia nitrogen is low, the nitrification ability is almost eliminated.

AL bacteria have an ammonia nitrogen concentration of 200
Proliferates preferentially in the region of not more than mg / l, remarkable growth of the number of bacteria is observed, and the nitrification rate shows a parabola with a peak near 100 mg / l. In the region where the concentration of ammonia nitrogen is 150 to 400 mg / l, AH bacteria and AL bacteria grow in a mixed phase, and the nitrification rate has a synergistic effect due to the mixture of two kinds of bacteria.

Mixed biota of AH bacteria and AL bacteria or AH
Regardless of the single biota of bacteria alone, increasing the ammonium nitrogen load per carrier increases the cell density and consequently increases the nitrification rate per carrier. Then, to summarize the findings from the above, by contacting an ammonia-containing liquid having an ammonia nitrogen concentration of 400 mg / l or more with an immobilized carrier on which nitrifying bacteria AH bacteria preferentially propagated, in an aerobic atmosphere. , High-concentration ammoniacal wastewater can be treated at high concentration,
In addition, high-speed processing is possible. In this case, the ammonia nitrogen load per carrier of the immobilized carrier on which the AH bacteria preferentially propagated is set to 500 mg-N / hl-carrier or more, preferably 600 mg-N / hl-carrier or more. As a result, the nitrification speed is further increased, and further high-speed processing can be performed.

When the concentration of ammonia nitrogen in the liquid is 10
By contacting the immobilized carrier in which the ammonia-containing solution of 0 to 400 mg / l or more and the immobilized carrier in which the nitrifying bacteria AH bacteria and AL bacteria are mixed and immobilized preferentially are brought into contact in an aerobic atmosphere, the medium concentration is increased. High-speed treatment of ammoniacal wastewater from low to low concentrations. Also in this case, the ammonia nitrogen load per carrier of the immobilized carrier on which the AH bacteria and the AL bacteria were mixed and immobilized was 500 mg-N / h ·
By setting the amount to be not less than 1-carrier, preferably not less than 600 mg-N / h.l-carrier, the nitrification rate is further increased and further high-speed treatment can be performed.

Therefore, the characteristics of AH bacteria suitable for high-concentration ammonia nitrogen wastewater and the characteristics of AH bacteria and AL bacteria in which AH bacteria and AL bacteria suitable for medium-concentration ammonia nitrogen wastewater are propagated in a mixed phase are well-developed. By using the wastewater, ammonia nitrogen wastewater such as sewage can be treated efficiently and at high speed, so that the wastewater treatment apparatus can be downsized.

FIG. 6 shows a first embodiment of the wastewater treatment apparatus 10 of the present invention constructed based on the above findings. FIG.
As shown in the figure, the raw water of the ammoniacal nitrogen wastewater is first separated through a raw water inflow pipe 12 by a pressure pump (not shown) after solid matter in the raw water is separated in advance by a solid-liquid separator (not shown). The water is sent to the ammonia concentrator 14. The first ammonia concentrator 14 is composed of a reverse osmosis membrane (RO membrane) device, and performs membrane separation into concentrated water in which the ammonia nitrogen in raw water is concentrated to a predetermined concentration and permeated water containing almost no ammonia nitrogen. I do. The permeated water is discharged from the permeated water pipe 16 as it is, and the concentrated water is sent to the nitrification device 20 via the concentrated water supply pipe 18. Further, a bypass pipe 22 is provided from the raw water inflow pipe 12 to the nitrification apparatus 20 without passing through the first concentrator 14, and an open / close valve 24 is provided in the bypass pipe 22. This allows
When the concentration of ammonia nitrogen in the wastewater raw water is not required to be sufficiently high, the raw water is directly sent to the nitrification device 20 by the bypass pipe 22.

The nitrification apparatus 20 includes a nitrification tank 26 and a nitrification tank 2
6, a nitrifying bacteria immobilizing carrier 28 to be charged into the
An aeration pipe 30 for supplying air to form an aerobic state in the tube 6, and a screen 32 for preventing the carrier 28 from flowing out of the nitrification tank 26. As the carrier 28 to be charged into the nitrification tank 26, an immobilized carrier 28 in which AH bacteria are preferentially propagated, or an immobilized carrier 28 in which AH bacteria and AL bacteria are propagated in a mixed phase are used. Is performed. The nitrification liquid subjected to the nitrification treatment is sent to a denitrification device 36 via a nitrification liquid pipe 34. The pH at which the nitrifying bacteria works effectively is preferably about 7 to 8, and alkali can be added to the nitrification apparatus 20 in preparation for a pH decrease due to nitric acid generated by the nitrification treatment.

The denitrification device 36 is composed of a denitrification tank 38, a submerged stirrer 40, and a nutrient supply pipe 42. Denitrification tank 38
Activated sludge containing denitrifying bacteria floats in the inside, and a nutrient source of denitrifying bacteria, for example, alcohol is supplied through a nutrient supply pipe 42, and nitrification water is denitrified. The denitrification liquid subjected to the denitrification treatment is supplied to a solid-liquid separation tank 46 through a denitrification liquid pipe 44.
Is sent to the second concentrating device 50 through the supernatant water pipe 48.

The second concentrating device 50 includes a microfiltration membrane (MF)
Multistage reverse osmosis membrane (RO)
The denitrification liquid, which is constituted by a membrane) device and is pressure-fed to the second concentrator 50 by a pressure pump (not shown), is a concentrated water in which ammonia nitrogen remaining in the denitrification liquid is concentrated. And permeated water not containing ammonia nitrogen. The permeated water is discharged from the treated water pipe 52 as treated water. On the other hand, the concentrated water passes through a return pipe 54 to the nitrification apparatus 20 and a circulation pipe 56 branched from the middle of the return pipe 54, reaches the supernatant water pipe 48, and is circulated again to the second concentrator 50, and has a predetermined concentration ratio. And a part of the circulating concentrated water is returned to the nitrification device 20 via the return pipe 54. The amount of the concentrated water circulated and the amount returned to the nitrification device 20 are adjusted by a flow control valve 58 provided in the circulation pipe 56.

A circulating fluid pipe 60 is connected in the middle of the return pipe 54 so that the liquid in the denitrification apparatus 36 can be circulated to the nitrification apparatus 20 if necessary.
At 0, a circulation pump 62 is provided. Next, the operation of the wastewater treatment apparatus 10 of the present invention configured as described above will be described by using low-concentration ammoniacal nitrogen wastewater such as sewage (about 80 mg / l).
An example of processing will be described.

The low-concentration ammonia-nitrogen wastewater is first sent to a first concentrator 14 and membrane-separated into concentrated water in which ammonia-nitrogen is concentrated to a predetermined concentration and permeate containing almost no ammonia-nitrogen. . The permeated water is discharged as it is, and only the concentrated water is sent to the nitrification device 20. As a result, the concentrated water whose volume has been reduced according to the concentration ratio is sent from the first concentration device 14 to the nitrification device 20.

In the nitrification device 20, the concentrated water concentrated in the first concentration device 14 and the immobilized carrier 2 on which the nitrifying bacteria are immobilized.
8 in an aerobic atmosphere to perform nitrification treatment. The immobilizing carrier 28 for nitrifying bacteria used in this nitrification treatment may be A if the concentration of ammonia nitrogen in the concentrated water is 400 mg / l or more.
Using the immobilized carrier 28 on which H bacteria preferentially propagated,
If it is about 00 mg / l, it is preferable to use the immobilized carrier 28 in which AH bacteria and AL bacteria are mixed-phase propagated. As described above, the ammonia nitrogen wastewater is subjected to nitrification treatment by increasing the concentration of ammonia nitrogen to a concentration suitable for the immobilization carrier 28 of the AH bacteria or the immobilization carrier 28 in which the AH bacteria and the AL bacteria are mixed in phase. The number of bacteria in the inside increases remarkably, and a high nitrification rate can be obtained. In this case, the higher the ammonia nitrogen load per carrier, the higher the nitrification rate can be obtained, so that the ammonia nitrogen load per carrier can be increased as long as the ammonia nitrogen concentration of the treated water does not increase significantly. desirable. Specifically, the ammonia nitrogen load is 500 mg-N / hl-carrier or more, preferably 60 mg-N / hl.
Nitrification tank 26 so that the amount becomes 0 mg-N / hl-carrier or more.
It is preferable to set the amount of the carrier to be charged into the container, the residence time, and the like.

Next, the nitrification liquid that has been nitrified by the nitrification device 20 is sent to a denitrification device 36, subjected to denitrification by activated sludge containing denitrifying bacteria, and released to the atmosphere as nitrogen gas. The denitrification liquid subjected to the denitrification treatment in the denitrification device 36 is subjected to solid-liquid separation in a solid-liquid separation tank 46, and the supernatant of the denitrification solution is sent to the second concentrator 50 and remains in the denitrification solution. The ammonia nitrogen is removed. On the other hand, a part of the activated sludge settled at the bottom of the solid-liquid separation tank 46 is returned to the nitrification device 20, and the other activated sludge is pulled out of the system as surplus sludge.

Next, the denitrification liquid sent to the second concentrator 50 is circulated and concentrated so as to have a predetermined concentration ratio, so that the concentrated water in which ammonia nitrogen is concentrated and the ammonia nitrogen are almost completely removed. The membrane is separated into permeate that does not contain. The concentrated water is returned to the nitrification device 20 and the nitrification treatment is performed again. On the other hand, the permeated water is discharged as treated water. Thereby, since the ammonia nitrogen remaining in the denitrification liquid is almost completely removed, the ammonia nitrogen concentration in the treated water can be reduced as much as possible.

As described above, by utilizing the characteristics of the immobilization carrier 28 on which nitrifying AH bacteria are propagated preferentially, or the immobilization carrier 28 on which AH bacteria and AL bacteria are propagated in a mixed phase, low concentrations of ammonia nitrogen Since the wastewater can be concentrated and subjected to the nitrification treatment, the amount of the wastewater treated by the nitrification device 20 can be significantly reduced. Furthermore, since high-speed treatment can be performed at a higher nitrification rate than the conventional activated sludge method, the wastewater treatment apparatus 10 can be significantly reduced in size.

Next, a second embodiment of the wastewater treatment apparatus 10 of the present invention will be described. In the second embodiment, the first concentrator 14 and the second concentrator 50 are changed from the membrane separation method in the first embodiment to a distillation separation method. In the second embodiment, only the nitrification system is shown. As shown in FIG. 7, the ammoniacal nitrogen wastewater is sent to a first ammonia concentrator 14 via a raw water inflow pipe 12 after solids in the raw water are separated in advance by a solid-liquid separator (not shown). The first ammonia concentrator 14 includes a distillation device 70, a condenser 72, and an absorption tank 74 in which an absorbing liquid (for example, a weak acid such as acetic acid) is stored. In the middle position in the distillation apparatus 70, a packed bed 7 filled with rahiring is provided.
6 is formed, the ammoniacal nitrogen wastewater is showered from a showering pipe 78 provided above the packed bed 76, and heated air is supplied from a heated air pipe 80 provided below the packed bed 76. Supplied to As a result, the ammonia nitrogen wastewater is distilled and separated into a distillate in which ammonia nitrogen is concentrated and a distillation residue containing almost no ammonia nitrogen. The distillate is condensed in the condenser 72 and then absorbed by the absorption liquid, and the distillation residue is discharged as it is.

The distillate absorbed by the absorbing solution is supplied to the distillate piping 6
The water is sent to the nitrification apparatus 20 through the humidifier 4 and the AH bacteria immobilization carrier 28 or the AH bacteria + AL as in the first embodiment.
Nitrification treatment is performed by contacting the bacteria-immobilized carrier 28 in an aerobic atmosphere. Above the nitrification device 20, a storage tank 82 for an alkaline liquid (for example, a weak alkali such as sodium hydrogen carbonate) for adjusting the pH in the nitrification tank 26 to about 7 to 8 is provided. A predetermined amount of the alkaline liquid is added by the added amount adjusting valve 68.

The nitrification liquid nitrified by the nitrification device 20 is
Water is supplied to the second concentrator 50 through the nitrification liquid pipe 34, and an alkali is added by an alkali addition line 84 during the water supply to raise the pH to around 10. The second concentrating device 50 is composed of a distillation device 86, and the structure of the distillation device 86 is the same as that of the distillation device described in the first embodiment. The nitrification liquid is distilled by the second concentrating device 50, and is separated into a distillate in which the ammonia nitrogen remaining in the nitrification liquid is concentrated and a distillation residue containing no ammonia nitrogen. The distillate is absorbed through the ammonia separation pipe 88 into the second absorption tank 90 in which the absorption liquid is stored, and is intermittently returned to the nitrification device 20 by the on-off valve 94 provided in the absorption tank pipe 92. On the other hand, the distillation residue is discharged as treated water.

The same effect as in the first embodiment can be obtained in the case of the wastewater treatment apparatus 10 according to the second embodiment configured as described above. Furthermore, since the distillation devices 70 and 86 are used as the first and second concentrators 14 and 50, there is no decrease in the processing capacity due to clogging or the like as in membrane separation. As described above, carbonate such as sodium bicarbonate is generally used for pH adjustment in the nitrification tank 26. However, if the second concentrator 50 is a membrane separation method, clogging by carbonate is prevented. Although the solid-liquid separation tank is indispensable, the distillation separation method does not require it and the apparatus can be simplified.

In the above embodiment, a measuring device for monitoring the concentration of ammonia nitrogen in the raw wastewater is provided.
When the concentration ratio in the first concentration device is determined based on the measurement result, more efficient nitrification treatment can be performed. Further, the first or second concentrator does not need to use the same system, and the membrane separation system and the distillation system can be freely combined.

[0037]

The following is a description of an embodiment which was tested using the above wastewater treatment apparatus. (Embodiment 1) Embodiment 1 is a wastewater treatment apparatus 1 described with reference to FIG.
In this case, the capacity of the nitrification tank 26 was set to 5 liters. As the immobilization carrier 28, a binding type PVA carrier obtained by adhering and nitrifying bacteria to a 3 mmφ carrier surface was used, and the filling rate was 20%.

The operation conditions were No. 1 to No. 3 and the ammonia nitrogen load per carrier was 60%.
Nitrification tank 26 so that the amount becomes 0 mg-N / hl-carrier or more.
At different residence times. The ammonia nitrogen concentration, the ammonia removal rate (removal rate with respect to the ammonia nitrogen concentration flowing into the nitrification tank 26) of the treated water, and the nitrification rate were measured when the operation was stabilized after continuous operation for 60 days.

The No. 1 operating condition is that the ammonia nitrogen wastewater having an ammonia nitrogen concentration of 80 mg / l is concentrated three times by the first concentration device 14 and supplied to the nitrification device 20 while the second concentration device At 50, the operation was performed so that the concentration was doubled, and the residence time in the nitrification tank 26 was set to 1 hour. The No. 2 operating condition is that the ammonia nitrogen wastewater having an ammonia nitrogen concentration of 400 mg / l is concentrated 1.5 times with the first concentration device 14 and supplied to the nitrification device 20 and the second concentration device 50 The operation was performed so that the concentration was tripled, and the residence time in the nitrification tank 26 was set to 5 hours.

The operation condition of No. 3 is a case of ammonia nitrogen wastewater having a sufficiently high ammonia nitrogen concentration of 1000 mg / l. The wastewater is directly nitrified by the bypass pipe 22 without using the first concentrator 14. To the device 20
Was used in double concentration, and the residence time in the nitrification tank 26 was set to 6 hours. As a comparative example, ammonia nitrogen wastewater having an ammonia nitrogen concentration of 80 mg / l was directly supplied to the nitrification device 20 without being concentrated, and only the second concentration device was used in double concentration.

FIG. 8 shows the above operating conditions and test results.
As a result, the measurement result of the ammonia nitrogen concentration of each treated water (permeated water of the second concentrator 50) in No. 1 to No. 3 was 4 mg / l (removal rate: 98.3%) in No. 1. ), No.2
8 to 9 mg / l (removal rate: 98.7%) and No. 3 to 10 mg / l (removal rate: 99.0%), which was sufficiently reduced. On the other hand, the ammonia nitrogen concentration of the treated water of the comparative example was 10 mg / l (87.5%), and the removal rate was lower than that of No. 1 to No. 3.

The measurement results of the nitrification rates in No. 1 to No. 3 were all 400 mg-N / h.l-carrier or more, and in particular, No. 3 was extremely 460 mg-N / h.l-carrier. It showed a high value. In contrast, the nitrification rate of the comparative example was 1
20 mg-N / hl · carrier, which was about 1/4 of No. 1 to No. 3. When the nitrifying bacteria contained in the carrier 28 after the test was completed, No. 1 and No. 2
The presence of AH bacteria and AL bacteria was confirmed in the carrier 28 of No.
It was confirmed that AH bacteria preferentially propagated in the carrier 28 of No. 3. Further, the carrier 28 of the comparative example was mostly composed of AL bacteria, and it is considered that the difference in bacterial species was reflected on the nitrification rate. (Embodiment 2) Embodiment 2 is a wastewater treatment apparatus 1 described with reference to FIG.
This is the case where 0 is used. The capacity of the nitrification tank 26, the used carrier 28, and the filling rate of the carrier 28 are the same as in the first embodiment. In the second embodiment, the urine wastewater synthesized as the ammoniacal nitrogenous wastewater was diluted to reduce the ammoniacal nitrogen concentration to 80 mg.
/ L was used. Further, the measurement of the ammonia nitrogen concentration and the nitrification rate of the treated water were measured when the operation was stabilized after continuous operation for 60 days.

The operating conditions of the present embodiment are as follows. Ammonia nitrogen wastewater having an ammonia nitrogen concentration of 80 mg / l is concentrated 5 times in the first concentrator 14 and supplied to the nitrification apparatus 20, and the second concentrator is used. At 50, the operation was performed so that the concentration was doubled, and the residence time in the nitrification tank 26 was set to 4 hours. As a comparative example, ammonia nitrogen wastewater having an ammonia nitrogen concentration of 80 mg / l was directly supplied to the nitrification device 20 without being concentrated, and only the second concentration device 50 was used for double concentration. The residence time in the nitrification tank 26 was set to 20 hours.

FIG. 9 shows the above operating conditions and test results.
As a result, in the case of this embodiment, the ammonia nitrogen concentration of the distillation residue discharged from the first concentrator 14 is 5 mg /
1 or less. The ammonia nitrogen concentration of the treated water (distillate residue) discharged from the second concentrator 50 is 1
It was stable at 0 mg / l or less. The nitrification rate is 29
It became 0 mg-N / hl·l-carrier, and in the case of the second example, the nitrification rate was returned to a high level. Thus, high-speed processing could be performed as in the first example.

On the other hand, in the case of the comparative example, the ammonia nitrogen concentration of the treated water (distillate residue) was reduced to 10 mg / l or less by making the residence time in the nitrification tank 26 five times that of this embodiment. However, the nitrification rate was 14 mg-N / hl·l-, which was significantly lower than that of the present example, and the result was far from high-speed processing. The decrease in the nitrification rate is considered to be due to a decrease in the cell density corresponding to the concentration of ammonia nitrogen in the nitrification tank 26.

[0046]

As described above, according to the wastewater treatment apparatus of the present invention, the characteristics of the immobilized carrier on which nitrifying AH bacteria are propagated preferentially, or the immobilized carrier on which AH bacteria and AL bacteria are multiphase propagated, Utilization of this method enables low-concentration ammoniacal nitrogen wastewater to be concentrated for nitrification treatment, so that the amount of wastewater treated in the reaction tank can be significantly reduced. Further, since high-speed treatment can be performed at a higher nitrification rate than the conventional activated sludge method, the wastewater treatment apparatus can be significantly reduced in size.

Therefore, it is extremely useful as a biological wastewater treatment apparatus installed in an urban area where it is difficult to secure a large site area.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the nitrification rate and the number of AH bacteria relative to the concentration of ammonia nitrogen.

FIG. 2 is a graph showing the relationship between the nitrification rate and the number of AL bacteria with respect to ammonia nitrogen concentration.

FIG. 3 is a diagram showing the relationship between the ammonia nitrogen load per carrier and the number of bacteria when the ammonia nitrogen concentration is kept constant at 200 mg / l.

FIG. 4 is a graph showing the relationship between the ammonia nitrogen load per carrier and the number of bacteria when the ammonia nitrogen concentration is kept constant at 500 mg / l.

FIG. 5 is an explanatory diagram showing an appropriate range of AH bacteria with respect to ammonia nitrogen concentration.

FIG. 6 is a configuration diagram illustrating a first embodiment of the wastewater treatment apparatus of the present invention.

FIG. 7 is a configuration diagram illustrating a wastewater treatment apparatus according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing operating conditions and results of an example implemented using the wastewater treatment apparatus according to the first embodiment of the present invention.

FIG. 9 is an explanatory diagram showing operating conditions and results of an example implemented using the wastewater treatment apparatus according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wastewater treatment apparatus 14 ... 1st concentrating apparatus 20 ... Nitrification apparatus 28 ... Carrier which fixed nitrifying bacteria 30 ... Aeration piping 36 ... Denitrification apparatus 46 ... Solid-liquid separation tank 50 ... 2nd concentrating apparatus

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masataka Kasai 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Plant Construction Co., Ltd. (56) References JP-A-5-64799 (JP, A) JP-A-5-177197 (JP, A) JP-A-63-36898 (JP, A) JP-A-5-169091 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3 / 00 C02F 3/34

Claims (3)

(57) [Claims] 1. A wastewater treatment apparatus for biological treatment with nitrifying bacteria carrying ammonia nitrogen wastewater on a carrier, comprising: a pretreatment concentration apparatus for concentrating the ammonia nitrogen wastewater to increase the concentration of ammonia nitrogen; Ammoniacal nitrogen-enriched water concentrated by the pretreatment concentrator, and nitrifying bacteria detected by culturing in a high-concentration ammonia solution of the nitrifying bacteria type, 40
AH bacteria exhibiting high activity at an ammonia nitrogen concentration of 0 mg / l or more, and nitrifying bacteria detected by culturing in a low-concentration ammonia solution, and have high activity at an ammonia nitrogen concentration of around 100 mg / l A wastewater treatment apparatus, comprising: a reaction tank in which an immobilized carrier in which an AL bacterium exhibiting the above-mentioned conditions is propagated in a mixed phase state is brought into contact with an aerobic atmosphere. 2. A concentrating device for post-treatment is provided for concentrating and separating ammoniacal nitrogen in the effluent discharged from the reaction tank and returning the concentrated water separated and concentrated to the reaction tank. The wastewater treatment apparatus according to claim 1 , wherein the ammonia nitrogen is removed. 3. A concentrator for the pretreatment and post-treatment, membrane separation apparatus with distillation unit, characterized in that it is selected from claims 1 or 2 of the waste water treatment apparatus.