JPH04371298A - Treatment of organic sewage and equipment - Google Patents

Abstract

PURPOSE:To stably enable nitrifying and denitrifying treatment by furthermore promoting nitrifying capacity in comparison with a conventional method in which an immobilizing technique is utilized. CONSTITUTION:A hollow structure 14 having a tube formed of an organic high polymer or an inorganic substance high in oxygen permeability is immersed into the inside of a nitrification tank 5. For example, air 6 is supplied to the inside of the hollow structure and supplied to the external surface thereof. The liquid to be treated is nitrified by organism slime formed on the surface of the hollow structure and then denitrified in a denitrification tank 7. The amount of immobilized nitrifying bacteria is more stabilized and also nitrifying capacity is promoted.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for nitrification and denitrification treatment of various organic wastewaters containing ammonia nitrogen, such as sewage, human waste, and industrial wastewater, which makes it possible to significantly reduce the size of treatment facilities. It is something.

0002

BACKGROUND OF THE INVENTION Nitrification and denitrification is a method of removing nitrogen from wastewater by utilizing the redox action of nitrifying bacteria and denitrifying bacteria, and is a technology that is widely used in Japan.

However, in the nitrification and denitrification method, the growth rate of nitrifying bacteria is extremely low, so in order to retain nitrifying bacteria in the biological reaction tank, the sludge retention time (SRT) must be increased.
It needed to be larger than in the case of standard activated sludge.

As a result, the hydraulic retention time (HRT) of the biological reaction tank inevitably becomes long. For example, when nitrification and denitrification treatment of sewage is performed, a biological reaction tank with an HRT of 14 to 16 hours is required. It was. Since the HRT of the standard activated sludge method biological reaction tank is usually designed to be 6 to 8 hours, it has been impossible to perform nitrification and denitrification treatment using the standard activated sludge method biological reaction tank. .

Therefore, in recent years, by immobilizing nitrifying bacteria on a carrier, the substantial SRT of nitrifying bacteria can be increased and the flow of nitrifying bacteria out of the system can be prevented. Methods are being developed to enable nitrification in

[0006] However, even with these methods that utilize immobilization techniques, the nitrification performance is insufficient during periods when the water temperature is low or when the raw water flow rate fluctuates greatly, and ammonia nitrogen may remain in the treated water. there were.

[0007]

[Problems to be Solved by the Invention] The present invention provides a method that enables stable nitrification and denitrification treatment by further promoting nitrification ability than conventional methods that utilize immobilization techniques. .

As a result of various studies conducted by the present inventors, it became clear that the problems of the conventional method could be overcome by stabilizing the amount of nitrifying bacteria immobilized and improving the oxygen supply method. reached.

[0009]

[Means for Solving the Problems] The present invention provides a method for treating organic wastewater by nitrification and denitrification, in which organic polymers or inorganic materials with high oxygen permeability are contained inside a nitrification tank or a single nitrification and denitrification tank. A method for treating organic sewage, characterized by immersing a hollow structure having a tube formed from a tube and supplying an oxygen-containing gas inside the hollow structure, and at least a nitrification tank, a denitrification tank or a single In an organic wastewater treatment device consisting of a nitrification and denitrification tank, a hollow structure having a tube made of an organic polymer or an inorganic material with high oxygen permeability is immersed in the nitrification tank or the nitrification and denitrification tank, and This organic wastewater treatment device is characterized in that the inside of the hollow structure is in communication with an oxygen-containing gas supply device.

[0010] According to the present invention, a hollow structure having a special structure is provided in a nitrification tank or a nitrification-denitrification tank to improve the nitrification function and reduce HRT. That is, this hollow structure is characterized by being equipped with a tube made of an organic polymer or an inorganic material with high oxygen permeability, and the oxygen-containing gas supplied from the oxygen-containing gas supply device is fed into the tube into a nitrification tank or a nitrification tank. Oxygen is supplied through the tube membrane to the outside of the tube surface immersed in the treated liquid supplied to the denitrification tank, and the oxygen concentration in the environment on the outer surface of the tube can be maintained at a high level at all times, thereby eliminating nitrifying bacteria. It is capable of being supported on the outer surface of the tube and maintaining its propagation highly and uniformly,
Thereby, nitrification efficiency can be improved.

[0011] The method of deploying and holding the tube in the hollow structure used in the present invention is arbitrary, but examples include a method of fixing both ends of the tube with a support member having a hollow interior. . In addition, oxygen-containing gas is usually supplied to the hollow structure and tube from a gas inlet provided on the support member, and excess gas that has supplied oxygen, etc. to the nitrification tank is discharged from the gas outlet also provided on the support member. This structure is common.

[0012] The size of the tube, the distribution of the tubes in the hollow structure, etc. can be selected in various ways, but to give an example of a preferable range, the inner diameter of the tube is 0.2 to 0.2.
The length of the tube is 30-300 cm, preferably 50 mm, preferably 0.5-10 mm.
~200cm, but the tube thickness is 0.05~
2 mm, respectively, and the distribution of tubes in the hollow structure is such that the distance between the outer surfaces of the tubes is 10 to 200 mm.
mm, preferably 20 to 50 mm.

[0013] The oxygen-containing gas may be only oxygen gas, a mixed gas of oxygen gas and air, or oxygen gas and any other gas such as carbon dioxide. In addition, the oxygen concentration and/or the oxygen supply amount, that is, the oxygen-containing gas supply pressure,
By selecting various tube materials, hole sizes, etc.
The amount of dissolved oxygen (DO) in the nitrification tank can be adjusted. The gas pressure can be adjusted by controlling a blower.

[0014] The pore size of the tube is 0.05 to 50 μm for both organic polymers and inorganic materials in porous tubes.
, preferably 0.1 to 5 μm, and when air is used as the oxygen-containing gas, the air supply pressure in the organic polymer tube is 0.2 to 4 kgf/cm2 in gauge pressure,
It is preferably 0.8 to 1.5 kgf/cm2, and for inorganic tubes, it is 0.1 to 1 kgf/cm2, preferably 0.2 to 0.3 kgf/cm2.

[0015] As the organic polymer tube, it is preferable to use one having permselectivity particularly for oxygen gas, which is economical and allows the maximum use of ordinary air. rubber)
, polybutadiene, etc. are suitable. As a result, it is possible to increase the dissolved oxygen concentration (DO) that diffuses around the hollow structure (ie, the nitrification tank mixture) and increase the amount of oxygen supplied.

[0016] The porous tube has a porous structure with high oxygen permeability; for example, in the case of an inorganic tube, porous ceramics, specifically alumina-based, carbon-based, etc., are suitable. . For example, polypropylene or the like is suitable as an organic polymer. Porous materials have a large specific surface area and a large contact area with the nitrification tank mixture, so that the amount of oxygen supplied can be increased as a result.

[0017] Furthermore, the present invention allows the supply amount/or supply pressure of air to be supplied to the hollow structure to be adjusted according to the DO of the nitrification tank mixed liquid.
It is possible to control oxygen by detecting it and prevent insufficient or excessive supply of oxygen. As a control index, D
In addition to O, it is also possible to use an oxidation-reduction potential (ORP) or the like.

[0018] As described above, the present invention is for attaching and immobilizing biological slime containing nitrifying bacteria on the outer surface of a tube. That is, in addition to functioning as an oxygen supply device, the hollow structure also functions as an immobilization carrier for nitrifying bacteria. Furthermore, since DO can be supplied from inside the biological slime, it is possible to keep the entire biological slime aerobic. Since nitrifying bacteria are obligately aerobic, by keeping the entire biological slime aerobic, it is possible to increase the amount of nitrifying bacteria present and improve nitrification performance.

[0019] In addition, in the present invention, especially when a porous organic polymer or inorganic tube is used, when removing excess biological slime, the air supply pressure is set higher than the water pressure around the hollow structure. Excess biological slime can be removed by releasing gas as bubbles on the surface of the hollow structure. On the other hand, organic polymer tubes have the advantage that the biological slime on their outer surface can maintain a nearly steady state, so they do not require cleaning, or the frequency of cleaning is lower than that of inorganic tubes.

The hollow structure of the present invention is preferably unitized into a size that is convenient for handling, and a plurality of hollow structures can be combined and arranged in a nitrification tank. In this case, oxygen gas can be supplied to the hollow structure from one oxygen gas-containing supply device by communicating the gas outlet and gas inlet provided on the tube support member. Note that the nitrification tank may be provided with an aeration device at the bottom or the like, if desired, for supplying oxygen gas not to the interior of the hollow structure but to the liquid to be treated within the nitrification tank.

Next, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a diagram showing an example of the flow of the processing method of the present invention. The inflowing sewage 1 to be treated, for example, undergoes a settling/screening process 2 to remove large foreign substances such as sand, is first transferred to a settling tank 3, and undergoes a natural sedimentation process in which sedimentary components are removed as sludge 4, and ammonia-based sludge is removed. A liquid to be treated containing nitrogen and the like is obtained. In addition to this method, various known methods such as centrifugal treatment, membrane treatment, etc. may be used to obtain the liquid to be treated. The liquid is sent to a nitrification and denitrification tank consisting of a nitrification tank 5 and a denitrification tank 7, where it is subjected to nitrification and denitrification treatment. The activated sludge mixture that has been subjected to nitrification and denitrification treatment is sent to a final settling tank 9, where mainly sludge 11 is removed, and the supernatant water is subjected to chlorination treatment 12, etc., and then discharged as effluent water 13. The method for treating the activated sludge mixture that has been subjected to nitrification and denitrification is not limited to natural sedimentation, and known treatment methods such as membrane treatment can be applied. Further, a part of the sludge is mixed with the nitrification liquid and the liquid to be treated through the return sludge line 10 and recycled.

The structure of the nitrification and denitrification tank will now be explained in more detail with reference to FIGS. 2 and 3. The configuration of the nitrification tank 5 shown in FIG. 3 is a configuration in which a plurality of hollow structures 14 shown in FIG. 2 are provided, and an air diffuser 20 is further provided at the bottom of the tank.

[0023] The water sent from the initial settling tank 3 is passed through the nitrification tank 5 through the nitrification fluid circulation line to convert ammonia nitrogen into NOx.
- N
The OX-N is reduced to nitrogen, and the liquid containing ammonia nitrogen is transferred to the nitrification tank 5, where the above treatment is recycled.

Since the nitrification tank 5 must be maintained under aerobic conditions for the propagation and maintenance of nitrifying bacteria, air 6 is supplied thereto. The structure of the hollow structure 14 used in the present invention is as follows:
It has the function of not only maintaining this aerobic condition well, but also providing a good support for oxygen-permeable nitrifying bacteria. That is, the hollow structure 14 consists of a tube 16 and a support member 15 that holds the tube 16. The support member 15 is a tube 16
The inside of the tube is hollow and communicates with the tube 6, and has an air inlet 17 and an air outlet 1 for introducing air into the tube 6.
8 are deployed. Further, the tube 6 is at least permeable to oxygen and is a good adhesion carrier for nitrifying bacteria, and can enjoy a direct supply of oxygen from the surface of the tube 6, so it has the characteristic of maintaining high biological activity. The supply of oxygen takes place through a tube connected to the air inlet 17 and a blower (not shown). By controlling the amount of air at this time, a desired amount of oxygen can be supplied. This air supply device can also be used to eliminate excess microorganisms that have formed on the tube surface, and in this case it is preferable to increase the amount of air supply than usual. Further, the oxygen may be supplied only from a tube, but if desired, an aeration device 20 may be provided at the bottom of the nitrification tank to widen the control range of the oxygen amount. In addition, a flow port 19 for activated sludge mixed liquid is provided in the support member 19.
By providing this, the efficiency of the nitrification reaction can be increased.

In this example, the shapes of the hollow structure 14 and the nitrification tank are rectangular, but the present invention is not limited to these shapes, and any shape is acceptable. is also optional. For example, the support member may also be constructed from an oxygen permeable material.

Although FIG. 1 describes an example consisting of a nitrification tank and a denitrification tank, the present invention can also be applied to a case where nitrification and denitrification are performed in a single tank (nitrification and denitrification tank).

[0027]

[Effect] In the nitrification and denitrification method, it is difficult to maintain sufficient nitrification performance during periods of low water temperature or during periods of large flow rate fluctuations with the conventional method that only involves immobilizing nitrifying bacteria in the nitrification tank. there were. However, the present invention, which involves immersing a hollow structure made of a special material into the nitrification tank, increases the ability to supply oxygen to the nitrification tank, and also increases the amount of nitrifying bacteria fixed by keeping the entire biological slime aerobic. let me,
By increasing nitrification performance, it is possible to overcome the problems of conventional methods caused by lower water temperatures and flow rate fluctuations.

[0028]

EXAMPLES The present invention will be explained in detail based on examples. (a) Example with polydimethylsiloxane hollow structure -
Operating conditions - Apply the processing flow in Figure 1.

・Water temperature: 11~16°C ・Amount of treated sewage: 240m3/day (hourly flow rate fluctuation...80-120% of average flow rate) ・Nitrification liquid circulation amount: 480m3/day ・Amount of returned sludge: 120m3/day ・Air Supply amount (air is used as oxygen-containing gas): Hollow structure...0.7Nm3/min (tube supply pressure 0.8
~1.5kgf/cm2), nitrification tank mixed liquid DO
was maintained at 2-3 mg/L (liter).

Aeration device...0.7Nm3/min・Biological reaction tank capacity: Denitrification tank...60m3 (HRT...6 hours) Nitrification tank...20m3 (HRT...2 hours)・Hollow structure of nitrification tank: See Figure 2 Unit shown (1m x 1m x 2m)
Number of filling units used: 4 units/20 m3 Nitrification tank Use of polydimethylsiloxane tubes: 50 tubes with inner diameter 10 mm x length 2 m, tube wall thickness 0.5 mm connected to 1 unit - Processing results - Water quality of composite sample (raw) Sewage/treated water)・BO
D...210/8 mg/L
・SS…180/5
mg/L・Kendall nitrogen...40/3
mg/L・Nitrous acid + nitric acid … 1/6
mg/L as N In this way, even in the low water temperature period, the biological reaction tank HRT:
It was possible to reduce the total nitrogen in the treated water to 10 mg/L or less in 8 hours. The thickness of the biological slime on the tube surface was constant, ranging from 100 to 300 μm. In addition, the entire biological slime was brown in color, and no anaerobic black parts were observed.

(b) Example of porous ceramic hollow structure - Operating conditions - The processing flow is the same as that in FIG.

・Water temperature: 14~18°C ・Amount of sewage treated: 240m3/day (hourly flow rate fluctuation...40-160% of average flow rate) ・Nitrification liquid circulation amount: 480m3/day ・Amount of returned sludge: 120m3/day ・Air Supply amount: Hollow structure...0.7Nm3/min (tube supply pressure 0
．． (controlled at 2 to 0.3 kgf/cm2), and the nitrification tank mixed solution DO was maintained at 2 to 3 mg/L.

Aeration device...0.7Nm3/min・Biological reaction tank capacity: Denitrification tank...60m3 (HRT...6 hours) Nitrification tank...20m3 (HRT...2 hours)・Nitrification tank hollow structure: 1 unit ( The external appearance of the building (1m x 1m x 2m) is the same as that in Figure 2.

[0034] Number of filling units...4 units/20m3
Nitrification tank porous ceramic tube...Alumina type, pore size 0
．． Connect 50 tubes of 1 to 5 μm, inner diameter 10 mm x length 2 m, wall thickness 0.5 mm to one unit - Treatment results - Water quality at peak flow rate (raw sewage/treated water)/BOD
...210/9 mg/L・SS
...180/9 mg/L
・Kendall nitrogen...35/4 mg/L
・Nitrous acid + nitric acid … 1/5 mg
/L as N In this way, even when the flow rate fluctuations are large during the low water temperature period, the total nitrogen of the treated water can be reduced to 10 in 8 hours of biological reaction tank HRT.
It was possible to reduce the amount to below mg/L. Note that the thickness of the biological slime on the surface of the ceramic tube was not constant like that of polydimethylsiloxane, but tended to increase in thickness as the operation progressed. Therefore, once every two weeks, the pressure of the air introduced into the tube was increased to 0.8 kgf/c.
Excess slime was removed by increasing the temperature to m2 and bubbling the feed gas.

[0035]

[Effects of the Invention] As explained above, according to the present invention,
HRT: It is possible to perform sufficient nitrification and denitrification treatment in a biological reaction tank for 8 hours. Moreover, microbial treatment of BOD can also be ensured at the same time.

The present invention will be widely adopted in future nitrification and denitrification treatment methods for organic wastewater.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the flow of an embodiment of the processing method of the present invention.

FIG. 2 is a diagram for explaining an example of the structure of a hollow structure used in the present invention.

FIG. 3 is a diagram for explaining an example of a nitrification tank used in the present invention.

[Explanation of symbols]

1 Inflow sewage 2　Sand settling/screen treatment 3 First settling tank 4. Sludge 5 Nitrification tank 6 Air 7 Denitrification tank 8 Nitrification liquid circulation line 9 Final settling tank 10 Return sludge line 11 Sludge 12 Chlorine disinfection 13　Discharge water 14 Hollow structure 15 Support member 16 Tube 17 Air inlet 18 Air outlet 19 Activated sludge mixture flow port 20　Air diffuser

Claims (2)

[Claims] Claim 1: A method for treating organic wastewater by nitrification and denitrification, in which a hollow tube having a tube made of an organic polymer or an inorganic material with high oxygen permeability is provided inside a nitrification tank or a single nitrification and denitrification tank. A method for treating organic wastewater, comprising immersing a structure and supplying oxygen-containing gas into the hollow structure. Claim 2: In an organic wastewater treatment device consisting of at least a nitrification tank, a denitrification tank, or a single nitrification and denitrification tank, the nitrification tank or the nitrification and denitrification tank is made of organic polymer or inorganic material with high oxygen permeability. 1. An organic sewage treatment device, characterized in that a hollow structure having a hollow tube is immersed therein, and the inside of the hollow structure is in communication with an oxygen-containing gas supply device.