JP2003285093A - Biological denitrification method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological denitrification system enabling almost perfect denitrification and preventing the lowering of a recovery ratio of water by washing the filter medium packed part of a biological membrane filtering and cleaning apparatus. <P>SOLUTION: In a biological denitrification method for water using an activated sludge treatment apparatus having a denitrification tank and a nitrification tank and the biological membrane filtering type septic tank provided on the downstream side thereof, the biological membrane filtering type septic tank is set to an ascending flow type and a hydrogen donor is injected in water on the downstream side of an NO<SB>x</SB>-N detection means but on the upstream side of the filter medium packed part in an amount controlled on the basis of the signal from the NO<SB>x</SB>-N detection means arranged on the upstream side of the filter medium packed part arranged at the intermediate part of the septic tank. An oxygen-containing gas is injected in the central part of the filter medium packed part in an amount controlled on the basis of the signal from the dissolved oxygen detection means arranged on the downstream side of the filter medium packed part and washing wastewater discharged by the washing operation of the filter medium packed part of the biological membrane filtering type septic tank is returned to the activated sludge treatment apparatus. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biological nitrogen removal system for water, and more particularly to a controlled oxygen donor for injecting a controlled hydrogen donor downstream of an activated sludge treatment device. The present invention relates to a biological nitrogen removal system for water having a biofilm filtration septic tank for injecting water.

[0002]

2. Description of the Related Art The sewerage penetration rate reached 57% at the end of 1998, and the emphasis on sewerage development has shifted to small and medium-sized municipalities. In addition, as awareness of water environment conservation increases, promotion of advanced treatment for the purpose of eutrophication in closed water areas and recycling and reuse of sewage treatment water is also an important issue. The current main substances to be removed in the advanced treatment method are nitrogen and phosphorus that cannot be removed by the standard activated sludge method,
As a method for removing these, a circulating nitrification denitrification method (nitrogen removal), an anaerobic aerobic method (phosphorus removal), etc. have already been put into practical use.

Recently, a carrier-introduced activated sludge method capable of simultaneously removing nitrogen and phosphorus at the same retention time as that of the standard activated sludge method has been developed, and its spread is expected. On the other hand, the biofilm filtration method is capable of removing soluble organic substances and nitrification at high speed due to the action of microorganisms adhering to the filter medium at high speed in addition to the physical filtration action. Has been promoted (water and wastewater, vol.25, N
o. 5 (1983), Shimura et al., "Nitrogen Removal Process Using Biofilm Filtration Method", 31st Sewer Research Presentation Lecture (1
994) etc.). In the small-scale sewage treatment, in addition to the features described above, a settling tank is not required and sludge management is not required, and maintenance is easy. Practical use is progressing as the next processing method. Further, its application is being advanced as an advanced treatment for secondary sewage treatment water. However, since these methods, which have been put into practical use, do not support nitrogen removal, a nitrogen removal process that makes the most of the characteristics of the biofilm filtration method has been desired.

As a nitrogen removal process for small-scale sewage, the present inventors have developed a nitrogen removal device by a biofilm filtration method using a floating filter medium having a specific gravity lighter than that of water (Sakuma et al. Removal of Nitrogen by the Biofilm Filtration Method ", 4th Hokkaido University Hygiene Engineering Symposium Proceedings (1996)
Such). When a floating filter medium is used as the filter medium for the biofilm filtration method, it is possible to make the lower part of the ventilation pipe an anaerobic part and the upper part an aerobic part by passing water in an upward flow and installing a ventilation pipe in the packed bed. It is possible to remove nitrogen in one tower (Rogalla
et. al. "Upscaling a compac
t nitrogen removal processes
s "Wat. Sci. Tech. (1992). Moreover, it is possible to use a floating filter medium for the anaerobic filter bed, and by using the lower part of the filter bed as a settling section, a denitrification tank that doubles as a settling tank can be obtained. Nitrogen removal can be performed by combining with the existing aerobic filter (Tanaka et al. "Research on small-scale sewage treatment process" EBARA Inferco Jikkan No. 104 (199)
1)). Against this background, the present inventors have aimed to remove SS and phosphorus as a pretreatment process and organic pollutants and nitrogen as an efficient treatment method of the return water of sludge intensive treatment. We have been developing a treatment system consisting of the following biological treatment processes (Ebara Bulletin No. 187).
(2000-4), (Company) Japan Sewer Association 38th Sewer Research Presentation Lecture p538-540 (2001), etc.).

[0005]

However, the limit of the total nitrogen concentration of the treatment liquid treated by the conventional biological purification apparatus such as the combination of the precoagulation and the biofilm filtration is about 10 mg / liter, which is less than this value. It was extremely difficult to remove nitrogen. Also, HRT is usually 10-12 hours
There is a strong demand for shortening (Hydric Retention Time, retention time). Furthermore, there has been a strong demand for improving the transparency of the treatment liquid without providing a final settling tank.

In view of the above circumstances, the present invention provides a system capable of almost completely removing nitrogen, and biological nitrogen removal in which the recovery rate does not decrease due to cleaning of the filter medium filling part of the biofilm filtration and purification device. The purpose is to provide a system.

[0007]

The present invention has solved the above-mentioned problems by the means described below. (1) In a biological nitrogen removal method of water using an activated sludge treatment device having a denitrification tank and a nitrification tank and a biofilm filtration septic tank provided on the downstream side, the biofilm filtration septic tank is an upflow type the organism membrane filtration type septic tank of the intermediate portion arranged oxidized nitrogen than filter material filling portion disposed upstream of water (NO _x -N) is controlled by a signal from the sensing means the amount of the hydrogen donor Injecting water downstream of the detection means and upstream of water from the filter medium filling section, while controlling the amount of oxygen by a signal from a dissolved oxygen (DO) detection means installed downstream of the filter medium filling section. Biological water characterized by injecting a contained gas into substantially the center of the filter medium filling section and returning the cleaning wastewater discharged by the cleaning operation of the filter medium filling section of the biofilm septic tank to the activated sludge treatment device. Nitrogen removal method. (2) The biological nitrogen removing method according to (1), wherein the cleaning wastewater is returned to the denitrification tank inflow part of the activated sludge treatment device. (3) The injection amount of the hydrogen donor is set so that the COD / N ratio is 2.
The method for removing biological nitrogen according to (1) or (2) above, wherein the method is controlled so as to be 4 or more. (4) The biological nitrogen removal according to any one of (1) to (3), wherein the injection amount of the oxygen-containing gas is controlled so that DO is 5 mg / liter or more. Method.

(5) In an apparatus for biological nitrogen removal of water using an activated sludge treatment device having a denitrification tank and a nitrification tank and a biofilm filtration type septic tank provided on the downstream side, the biofilm filtration type septic tank is directed upward. and the flow type, is arranged filter media filled portion in an intermediate portion of the organism membrane filtration type septic tank, the filter media upstream oxidation nitrogen (NO _x -N) detecting means of the filling unit is installed, and downstream from said detecting means Injecting means for injecting an amount of hydrogen donor controlled by a signal from the detecting means is installed upstream of the filter medium filling section, while dissolved oxygen (DO) detection is provided downstream of the filter medium filling section. A means is installed, and an injection means for injecting an oxygen-containing gas in an amount controlled by a signal from the dissolved oxygen (DO) detection means is installed at substantially the center of the filter medium filling section, and further, the injection means of the biofilm filtration septic tank is installed. By cleaning the filter material filling section The washing waste water issued, biological nitrogen removal system of water, characterized in that a pipe for returning the activated sludge treatment apparatus.

That is, the main points of the present invention are:
In a biological nitrogen removal system having an activated sludge treatment device and a biofilm filtration type septic tank provided on the downstream side thereof, the biofilm filtration type septic tank is an upflow type, and a filter medium is provided in an intermediate part of the biofilm filtration type septic tank. disposing the filling unit, the upstream of the filter media filled portion of the water provided oxide nitrogen (NO _x -N) detecting means, the hydrogen donor of the amount controlled by a signal from oxidation nitrogen detection means, wherein The amount controlled by the signal from the dissolved oxygen detection means is provided downstream of the detection means and upstream of the water in the filter medium filling portion, while the dissolved oxygen (DO) detection means is provided downstream of the filter medium filling portion. By injecting the oxygen-containing gas into the substantially central portion of the filter medium filling portion, it is possible to completely remove nitrogen, and the gas is discharged by a cleaning operation of the filter medium filling portion of the biofilm filtration septic tank. Wash wastewater, activated sludge treatment By returning to the apparatus, by collecting the washing waste water as treated water, a biological nitrogen removal system water recovery rate does not decrease.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.
In FIGS. 1 and 2 for explaining the embodiments and examples, constituent elements having the same function are designated by the same reference numerals, and repeated description thereof will be omitted.

FIG. 1 is a diagram illustrating an outline of one embodiment of the biological nitrogen removal system of the present invention. The activated sludge treatment device 2 shown in FIG. 1 is a device that performs a circulating nitrification denitrification method that is practically used in sewage treatment, and is composed of a denitrification tank 3, a nitrification tank 4, and a sedimentation tank 7. Using organic matter denitrification tank 3 the inflow waste water 1 as a hydrogen donor, nitrate nitrogen in the nitrification circulating fluid: the (NO _x -N NO ₂ -N and NO ₃ -N), then reduced to nitrogen gas nitrogen Remove. In the nitrification tank 4, decomposition and removal of residual organic substances and nitrification reaction using ammonia nitrogen (NH ₄ —N) as NO _x —N are performed. The activated sludge slurry 5 in the nitrification tank 4 is sent to the settling tank 7. In settling basin 7,
Solid-liquid separation is performed into activated sludge and overflow water 8 in the sedimentation basin. The limit of the total nitrogen concentration of the settling basin overflow water 8 is about 10 mg / liter.

In the biofilm filtration tank 11 of FIG. 1, it is possible to simultaneously utilize the physical separation effect by filtration and the bioreaction by the group of microorganisms adhering and growing on the surface of the filter medium.
Therefore, the final settling tank is not required in the latter stage of the biofilm filtration tank 11 and the microorganism group can be maintained at a high concentration, so that the reactor becomes a space-saving type. By providing this biofilm filtration tank 11, a total nitrogen concentration of 5 mg / liter or less can be stably obtained.

The lower layer (upstream side) of the biofilm filtration tank 11 is made anaerobic, and a hydrogen donor 15 is injected therein to remove oxidized nitrogen. Therefore, the overflow water 8
The concentration of oxidized nitrogen was measured, and a controlled amount of hydrogen donor 15 was injected so that nitrogen could be removed according to the concentration. The oxidized nitrogen concentration detecting means 13 is
N of the settling basin overflow water 8 collected from the upstream of the filter medium filling section 12
Any device that measures the amount of O ₂ —N and NO ₃ —N may be used, and the signal from this sensing means relates to the total amount of these nitrogens. The injection amount of the hydrogen donor 15 is COD.
/ N ratio (mg / COD / mgN) is 2.4 or more, especially 3
It is preferable to control so as to be 8 to 8 and especially 4 to 5. Here, COD is the amount of the hydrogen donor 15, N represents the amount of NO _x -N.

This control is usually performed by setting an arbitrary set value within these ranges so that the COD / N ratio is in the vicinity of this set value. This hydrogen donor 15 is used as a biofilm filtration tank 1
Inject from 1 upstream. The injection position is preferably downstream of the sampling position of the oxidized nitrogen detecting means 13. Hydrogen donor 15 according to the measured value of oxidized nitrogen
In order to prevent unnecessary addition of the hydrogen donor 15 and reduce the cost, a stable denitrification treatment is possible because the addition amount of is controlled. The hydrogen donor 15 may be any organic substance having a relatively low molecular weight and soluble in water, and examples thereof include methanol, ethanol, isopropanol, acetic acid, and the like, and methanol is preferable from the viewpoint of cost.

By forcibly injecting the oxygen-containing gas 17 from approximately the middle of the biofilm filtration tank 11, the upper layer (downstream) is made aerobic and the lower layer (upstream) is treated with nitrogen to supply the remaining amount of hydrogen. The body 15 is removed. At this stage, it is possible to secure the oxygen concentration of the treatment liquid at the same time. Since there is this stage (downstream side), this biofilm filtration tank 11 is forced to flow upward. Further, since there is this stage (downstream side), it is possible to use a sufficient amount or an excessive amount of the hydrogen donor 15 in the preceding stage (upstream side), and complete removal of nitrogen. Is possible. In order to remove the hydrogen donor 15 in the upper layer of the biofilm filtration tank 11, in order to secure the oxygen concentration of the liquid to be treated at a predetermined concentration as necessary, the liquid to be treated which has passed through the filter medium filling section 12 is dissolved. The amount of oxygen is measured and the amount of oxygen-containing gas 17 injected is controlled. The dissolved oxygen detection means may be any device that detects the dissolved oxygen amount of the liquid to be treated, which is sampled from the downstream side of the filter medium filling section 12 of the biofilm filtration tank 11. The injection amount of the oxygen-containing gas is DO (dissolved oxygen concentration) of 5 mg / liter or more, especially 5
It is preferable to control the concentration to be 8 mg / liter, and more preferably 5 to 7 mg / liter.

This control is usually performed by setting an arbitrary set value within these ranges so that DO is in the vicinity of this set value. The oxygen-containing gas 17 is injected into substantially the center of the filter medium filling section 12 of the biofilm filtration tank. The central part means the center of the most upstream part and the most downstream part of the filter medium filling part 12, and substantially the center means that there is an effective amount of the filter media upstream and downstream thereof. The dissolved oxygen concentration of the biological membrane filtration tank treated water 20 is continuously measured, and the biological membrane filtration tank 1 is measured according to the measured value.
By controlling the aeration amount of 1, excessive aeration can be reduced and the amount of electricity used can be saved.

In the case of the biofilm filtration tank 11, when the operation is continued, the SS component is trapped in the filter medium filling section 12 and the head loss is increased, so that the washing operation is required. Filter medium filling section 12
The cleaning operation is performed by the cleaning air diffuser 22 below the filter medium filling unit 12.
From the top, cleaning water from the upper part of the filter medium filling section 12
And the cleaning process by discharging the cleaning drainage 24 from the lower part of the filter medium filling section 12 are combined. As the cleaning water 23 supplied from the upper part of the filter medium filling section 12, it is preferable to use the treated water 20 of the biofilm filtration tank 11.
Most of the microorganisms involved in denitrification are facultative anaerobic,
There is no problem even if the lower layer (lower part) of the filter medium filling section 12 that is not aerated during normal operation is cleaned by aeration. The washing operation is performed when the head loss exceeds the set value or when the treatment duration after washing exceeds the set value. Figure
In the case of the treatment system of 1, the frequency of cleaning the biofilm filtration tank 7 is several times a week.

The washing wastewater 24 of the biofilm filtration tank 11 is returned to the activated sludge treatment device 2 and treated together with the inflowing wastewater 1. The pollutant component of the cleaning drainage 24 is the filter medium filling section 12
Since the SS is mainly composed of the microorganisms captured in, it does not adversely affect the nitrification and denitrification process, and solid-liquid separation is performed in the sedimentation tank 7, so that the return position of the washing wastewater 24 is set at the inflow part of the sedimentation tank or The denitrification tank 3 and the nitrification tank 4 can be used. However, when there is a possibility that the nitrification denitrification treatment performance may decrease due to the reduction of the residence time of the denitrification tank 3 or the nitrification tank 4 and the solid-liquid separation performance may decrease due to an increase in the water area load of the settling tank 7, The return position of the cleaning drainage 24 is not the inflow part of the sedimentation basin 7, the denitrification tank 3 or the nitrification tank 4 but the adjustment tank for the inflowing wastewater 1,
It should be treated together with the inflow wastewater 1.

Alternatively, a cleaning drainage storage tank is installed to temporarily store the cleaning drainage 24, and the solid-liquid separation performance is reduced due to an increase in the water area load of the sedimentation basin 7, and the residence time of the denitrification tank 3 and the nitrification tank 4 is reduced. Alternatively, the cleaning wastewater 24 may be returned to the inflow portion of the settling tank 7, the denitrification tank 3, and the nitrification tank 4 at a flow rate that does not cause deterioration of the nitrification denitrification treatment performance. Biofilm filtration tank 1
1 is installed in plural series, the cleaning time of each biofilm filtration tank 11 is shifted, and the amount of cleaning wastewater 24 per one tank is reduced, so that the return position of the cleaning wastewater 24 is set at the inflow part of the sedimentation tank 7 or the like. When the denitrification tank 3 and the nitrification tank 4 are used, the solid-liquid separation performance deteriorates due to an increase in the water area load of the settling tank 7, and the denitrification tank 3 and the nitrification tank 4
It is less likely that the nitrification and denitrification treatment performance will be deteriorated due to the decrease in the residence time. Further, in this case, it is possible to reduce the capacity of the cleaning drainage storage tank for temporarily storing the cleaning drainage 24.

The pollutant components in the cleaning wastewater 24 are purified by the activated sludge treatment device 2 and are treated together with the surplus sludge 10 in sludge treatment equipment such as a concentration step and a dehydration step. Biofilm filtration tank 1
Return the washing wastewater 24 of No. 1 to the activated sludge treatment device 2 of the previous stage,
By treating with the inflowing wastewater 1 and collecting it as the treated water 20, the water recovery rate becomes almost 100%.

In FIG. 1, 9 is a returned sludge, 6 is a nitrification liquid circulation pipe, and 22 is a filter medium filling section 1.
2 is an air diffuser for injecting an oxygen-containing gas 17 into 2. FIG. 2 is a schematic diagram of the biological nitrogen removal system used in the examples, and specifically shows the wash water circulation system and the wash drainage circulation system. In FIG. 2, 25 is a treated water tank,
26 is a wash water pump, 27 is a wash drain tank, 28 is a wash drain water pump, and other components are the same as those in FIG.

[0022]

EXAMPLES The present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

(1) Experimental conditions An experiment was conducted under the following conditions according to the process chart of FIG. As raw water, the first settling pond overflow water was used.

[0024] ・ Water condition (average value) BOD 150 mg / liter SS 80 mg / liter T-N 40 mg / liter

・ Specification of experimental equipment Denitrification tank capacity 1.5m ³ Nitrification tank capacity 3m ³ Sedimentation tank water area load 15m ³ / m ² / d Biofilm filtration tank φ0.5m × 4m Filter medium packed bed height 2m (anaerobic part 1m, Aerobic part 1m) Filter medium filling capacity 400 liters (anaerobic part 200 liters,
Aerobic part 200 liters) Cleaning drainage tank 2m ³

[0026] ・ Operating conditions for activated sludge treatment Raw water volume (Q) 6 liters / min MLSS 3000 mg / liter Return sludge amount 0.5Q Return sludge concentration 9000mg / liter Nitrification solution circulating water volume 0.5-1.5Q Nitrification tank DO 3-4 mg / liter Water temperature 20 ℃

Operating conditions of biofilm filtration tank Methanol injection amount COD / NO _x -N = 4.5 Treated water DO 6 mg / liter Water temperature 20 ° C. Wash water amount 1 m ³ / wash water flow amount 0.5 l / min

As a filter medium for a biofilm filtration tank, a specific gravity of 0.1
6. Expanded polystyrene particles having an effective diameter of 4 mm were used.
Methanol was used as the hydrogen donor for denitrification in the biofilm filtration tank. The oxidized form of nitrogen concentration in the settling basin overflow flowing water continuously measured and controlled methanol injection amount such that the COD / NO _x -N = 4.5. The DO of the treated water in the biofilm filtration tank was continuously measured, and the air amount was controlled so that the DO of the treated water was 6 mg / liter. Cleaning of the biofilm filtration tank was performed when the head loss was over 2 m. After storing the cleaning wastewater in the cleaning wastewater storage tank, 0.5 liter / mi
It was returned to the denitrification tank at a flow rate of n. Filter medium packed bed cleaning 1
The amount of washing waste water per operation is 1 m ³ .

The experiment was conducted in three periods. Experiment section 1 has a nitrification solution circulating water volume of 1.5Q, and the biofilm filtration tank is not used. Experiment section 2 uses a biofilm filtration tank and nitrification solution circulation water amount is 1.5Q. This is a period in which a membrane filtration tank is used and the amount of circulating water of nitrification solution is set to 0.5Q.

(2) Experimental results-The nitrogen removal results are shown in FIG. After inflowing at about 40 mg / liter, the T-N of the overflow water of the sedimentation basin was about 13 mg / liter in experimental sections 1 and 2, and about 20 mg / liter in experimental section 3, showing a nitrogen removal rate according to the circulation ratio. . Most of the TN of the overflow water of the sedimentation tank was NOx-N. Using a biofilm filtration tank,
In Experimental Sections 2 and 3 in which denitrification was performed by injecting methanol according to the NOx-N concentration of the overflow water of the sedimentation basin, the nitrogen concentration of the treated water was 0.5 mg / liter or less for NOx-N, T
1N / l could be achieved with -N.

The DO control result of the biofilm filtration tank is shown in FIG. By incorporating the aeration amount control, the DO of the biofilm filtration tank treated water could be stably controlled to 6 mg / liter.・ SS results are shown in FIG. Throughout the experimental sections 1 to 3, the SS of the overflow water of the sedimentation basin was 10 mg / liter or less. In the experimental sections 2 and 3, SS of the biofilm-filtered water could be treated to 5 mg / liter or less.

-BOD Results are shown in FIG. After flowing in at about 150 mg / liter,
Through the experimental zones 1 to 3, 10 mg / liter in the overflow water of the sedimentation pond
5 or less for the biofilm-filtered water in the experimental sections 2 and 3
It fell below mg / liter. Precipitation compared to Experiment Zone 2
NO of Ikegoe running water _x-High N concentration,
Remaining amount of injected methanol in the increased experimental section 3
Are considered to have been removed.

Washing of filter medium packed bed The cleaning frequency of the filter medium packed bed was once every 3 days in experimental section 2 and once every 2 days in experimental section 3. In Experiment Group 3 in which a large amount of methanol was injected, the cleaning frequency was higher than that in Experiment Group 2.
The ratio of the amount of washing wastewater to the amount of raw water was 4% in Experimental Zone 2,
It was 6% in experimental section 3. The amount of cleaning wastewater sent is 0.5 liters / min, so the amount of cleaning wastewater per meter is 1 m.
Can deliver ³ in 33 hours. Cleaning frequency is 2-3 days (48
Once every 72 hours), the amount of washing waste water sent is 0.5
By setting the rate to 1 liter / min, the entire amount of the cleaning drainage received in the cleaning drainage tank before the next cleaning starts can be sent to the denitrification tank.

-Treatment water quality when washing wastewater is returned to the activated sludge treatment facility. From the results of Figs. 3, 5 and 6, in the case of the experimental sections 2 and 3 where the washing wastewater of the biofilm filtration tank is returned to the activated sludge treatment facility. Also, the quality of TN, SS, and BOD of the overflow water of the sedimentation basin was the same as that of the experimental section 1 (the experimental section 3 has a high TN,
Because the nitrification solution circulation ratio is different). The pollutant components of the cleaning wastewater are
It is an SS mainly composed of microorganisms trapped in the filter medium filling part, which does not adversely affect the nitrification and denitrification process, and because it is separated into solid and liquid in the sedimentation tank, it affects the quality of the overflow water of the sedimentation tank. There was no. The amount of water sent during washing drainage is less than 10% of the amount of raw water, and the solid-liquid separation performance decreases due to an increase in the water area load of the sedimentation basin, and the nitrogen removal performance of the denitrification tank and the nitrification tank decreases due to the decrease There was no effect on the decline.

The results of water recovery rate are shown in Table 1. Water recovery rate is 9 in all experimental plots
It was 8% or more. In Experimental Zones 2 and 3, the same waste water recovery rate as in Experimental Zone 1 was obtained by returning the cleaning wastewater from the biofilm filtration tank to the activated sludge treatment device in the previous stage, treating it with raw water, and collecting it as treated water.

[0036]

[Table 1]

[0037]

According to the present invention, there is provided a biological nitrogen removal system comprising an activated sludge treatment device and a biofilm filtration septic tank provided on the downstream side thereof, wherein the biofilm filtration septic tank is used as an upward flow. A filter medium filling section is arranged in the middle of the biofilm filtration septic tank, and oxidized nitrogen (NO _{x) is provided} upstream of the filter medium filling section.
-N) A detection means is provided, and a hydrogen donor in an amount controlled by a signal from the oxidized nitrogen detection means is injected upstream of the filter medium filling section, while dissolved oxygen (D) is supplied downstream of the filter medium filling section.
O) A biofilm capable of complete nitrogen removal by providing a detection means and injecting an amount of oxygen-containing gas controlled by a signal from the dissolved oxygen detection means into substantially the center of the filter medium filling part. In the filtration type septic tank, complete nitrogen removal can be achieved, and the washing wastewater discharged by the washing operation of the filter medium filling part of the biofilm septic tank is returned to the activated sludge treatment system, and the washing wastewater is treated together with the inflowing wastewater, and treated. By recovering as water, it was possible to provide a biological nitrogen removal system in which the water recovery rate does not decrease.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating the principle of a biological nitrogen removal system according to the present invention.

FIG. 2 is a block diagram of a biological nitrogen removing apparatus used in an embodiment of the present invention.

FIG. 3 is a graph showing the daily change of total nitrogen.

FIG. 4 is a graph showing the daily change of treated water DO.

FIG. 5 is a graph showing the daily change of SS.

FIG. 6 is a graph showing daily changes in BOD.

[Explanation of symbols]

1 Influent Raw Water 2 Activated Sludge Treatment Device 3 Denitrification Tank 4 Nitrification Tank 5 Activated Sludge Slurry 6 Nitrification Solution Circulation 7 Settling Tank 8 Sedimentation Tank Overflow Water 9 Returned Sludge 10 Excess Sludge 11 Biofilm Filtration Tank 12 Filter Media Packing Layer (layer) 13 NO _x total 14 hydrogen donor injection pump 15 hydrogen donor (methanol) 16 hydrogen donor storage tank 17 air (oxygen-containing gas) 18 air diffuser 19 DO meter 20 treated water 21 air 22 cleaning air diffuser 23 cleaning water 24 cleaning drain 25 Treated water tank 26 Wash water pump 27 Wash drain tank 28 Wash drain pump

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Tsuno             2-8-14 Kinugawa, Otsu City, Shiga Prefecture F-term (reference) 4D040 BB05 BB23 BB42 BB57 BB82                       BB91 BB93

Claims (5)

[Claims] 1. A method for biological nitrogen removal of water using an activated sludge treatment device having a denitrification tank and a nitrification tank and a biofilm filtration septic tank provided on the downstream side thereof, wherein the biofilm filtration septic tank is upflowed. and wherein the hydrogen of the amount controlled by a signal from the organism membrane filtration type septic tank of the intermediate portion arranged filter material filling section oxide nitrogen, which is installed upstream of the water than (NO _x -N) detecting means donating A body is injected downstream of the detection means and upstream of water from the filter medium filling portion, while the amount controlled by a signal from a dissolved oxygen (DO) detection means installed downstream of the filter medium filling portion. Oxygen-containing gas is injected into substantially the center of the filter medium filling part, and the cleaning wastewater discharged by the cleaning operation of the filter medium filling part of the biofilm septic tank is returned to the activated sludge treatment device. Nitrogen removal method. 2. The biological nitrogen removing method according to claim 1, wherein the cleaning wastewater is returned to the denitrification tank inflow part of the activated sludge treatment device. 3. The injection amount of the hydrogen donor is COD / N
The biological nitrogen removal method according to claim 1 or 2, wherein the ratio is controlled to be 2.4 or more. 4. The injection amount of the oxygen-containing gas is DO of 5
The method for removing biological nitrogen according to any one of claims 1 to 3, wherein the method is controlled to be at least mg / liter. 5. An activated sludge treatment device having a denitrification tank and a nitrification tank, and a biological nitrogen removal apparatus for water using a biofilm filtration septic tank provided on the downstream side of the biofilm filtration septic tank. In the formula, a filter medium filling part is arranged in an intermediate part of the biofilm filtration septic tank, an oxidized nitrogen (NO _x -N) detecting means is installed upstream of the filter medium filling part, and is located downstream of the detecting means and Injecting means for injecting a hydrogen donor in an amount controlled by a signal from the detecting means is installed upstream of the filter medium filling section, while dissolved oxygen (DO) detecting means is provided downstream of the filter medium filling section. Is installed, and an injection means for injecting an oxygen-containing gas in an amount controlled by a signal from a dissolved oxygen (DO) detection means is installed in substantially the center of the filter medium filling section, and the filter medium of the biofilm filtration septic tank is further installed. It is discharged by cleaning the filling section. A biological nitrogen removing device for water, characterized in that a pipe is provided for returning the cleaning wastewater to the activated sludge treatment device.