JP7282920B2 - Wastewater treatment system and wastewater treatment method - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to a wastewater treatment system and a wastewater treatment method for purifying wastewater such as sewage.

The activated sludge method is generally used for treatment of municipal sewage and the like. In the activated sludge method, air is supplied to the water to be treated, and organic matter in the water to be treated is decomposed by the action of aerobic microorganisms.

Bacillus bacteria are present in the activated sludge. Bacillus bacteria (hereinafter simply referred to as "bacillus") have the characteristic of forming spores. Bacillus is a typical useful bacterium in activated sludge, and the enzymes and antibiotics produced by Bacillus have a bacteriolytic action, so treatment facilities dominated by Bacillus generate less excess sludge. In addition, Bacillus has a role to stop the action of sulfate-reducing bacteria, and the amount of odor generated is small.

By the way, in a sewage treatment facility for treating urban sewage and the like, solid-liquid separation is performed in sludge treatment processes such as concentration, dehydration, and drying after treatment in the water treatment process. The solid matter obtained by solid-liquid separation is reused as fertilizer or cement, while the separated liquid generated by solid-liquid separation is mixed with influent sewage and treated again in the water treatment process.

However, the concentration of organic matter, nitrogen and phosphorus contained in the separated liquid may be higher than the concentration of organic matter, nitrogen and phosphorus contained in the influent sewage. Mixing separated liquids containing high concentrations of organic matter, nitrogen, and phosphorus raises concerns about increased aeration power and deterioration of treated water quality in the water treatment process.

In recent years, there has also been a sewage treatment facility joint development project (MICS project), in which night soil and septic tank sludge are mixed and treated at sewage treatment facilities, and a mixed biomass project, in which general business waste such as garbage is mixed and treated in the digestion process of sludge treatment. Business is also being promoted. In view of such circumstances, the concentrations of organic matter, nitrogen, and phosphorus contained in the separated liquid generated in the sludge treatment process tend to increase.

Therefore, a technique for efficiently removing organic matter, nitrogen, and phosphorus from a separated liquid is desired.

Japanese Patent Application Laid-Open No. 2008-253948 Japanese Patent Application Laid-Open No. 2007-301511 Japanese Patent Application Laid-Open No. 2004-097093 Japanese Patent Application Laid-Open No. 2008-126169 Japanese Patent Application Laid-Open No. 2018-079402

The problem to be solved by the present invention is to provide a wastewater treatment system and a wastewater treatment method that can efficiently remove organic matter, nitrogen, and phosphorus contained in a separated liquid generated by solid-liquid separation in a sludge treatment process. It is to be.

A wastewater treatment system of an embodiment includes a rotating fiber unit that purifies a separated liquid generated by solid-liquid separation in a sludge treatment process for treating wastewater . The rotating fiber unit purifies the separated liquid while rotating such that a portion of the fibrous body having a three-dimensional network structure to which the activated sludge in which the Bacillus genus bacteria are dominant adheres is immersed in the separated liquid. The sludge treatment process consists of an aerobic tank for wastewater aeration in which wastewater from which sludge has been removed is aerated, and a post-aeration tank for precipitating the sludge contained in the wastewater after aeration in the aerobic tank for wastewater aeration. The separated liquid is the liquid generated by solid-liquid separation from the sludge precipitated in the sedimentation tank after aeration.

FIG. 1 is a conceptual diagram showing a configuration example of a wastewater treatment system to which the wastewater treatment method of the first embodiment is applied. FIG. 2 is a conceptual diagram showing a configuration example of a rotating fiber unit. FIG. 3 is a conceptual diagram showing a configuration example of the rotating fiber unit viewed from the front side (left side in FIG. 2). FIG. 4 is a conceptual diagram showing a configuration example of a wastewater treatment system to which the wastewater treatment method of the second embodiment is applied. FIG. 5 is a conceptual diagram showing a configuration example of a wastewater treatment system to which the wastewater treatment method of the third embodiment is applied. FIG. 6 is a conceptual diagram showing a configuration example of a waste water treatment system to which the waste water treatment method of the fourth embodiment is applied.

Each embodiment of the present invention will be described below with reference to the drawings. Note that these embodiments are merely examples, and do not limit the present invention.

(First embodiment)
A waste water treatment system to which the waste water treatment method of the first embodiment is applied will be described.

FIG. 1 is a conceptual diagram showing a configuration example of a wastewater treatment system to which the wastewater treatment method of the first embodiment is applied.

The wastewater treatment system 10 of the first embodiment includes a sludge treatment process for city sewage, a sludge treatment process for mixing night soil and septic tank sludge in a sewage treatment facility, and a sludge digestion process for general business waste such as garbage. The present invention relates to a wastewater treatment system that purifies a separated liquid generated from a mixed sludge treatment process, etc., using bacteria belonging to the genus Bacillus and a rotating fiber unit.

Specifically, the wastewater treatment system 10 of the first embodiment is a system for performing a sewage treatment flow of treating raw water a, which is wastewater such as sewage, and discharging treated water α. , a pretreatment facility 12 , a first sedimentation tank 14 , an aerobic tank 16 and a second sedimentation tank 18 .

The pretreatment facility 12 consists of a screen and a settling basin, receives the raw water a, and removes large contaminants, sand, etc. contained in the raw water a. The to-be-treated water b obtained by removing large contaminants, sand, etc. from the raw water a is discharged from the pretreatment equipment 12 .

The first sedimentation tank 14 is provided after the pretreatment facility 12, and the water to be treated b discharged from the pretreatment facility 12 is introduced. The water to be treated b flows slowly through the first sedimentation tank 14 , and sludge c contained in the water to be treated b settles to the bottom of the first sedimentation tank 14 during that time. The water to be treated d, which is the supernatant liquid of the water to be treated b from which the sludge c has been removed in this way, is discharged from the first sedimentation tank 14 .

The aerobic tank 16 is provided after the first sedimentation tank 14, and the water to be treated d discharged from the first sedimentation tank 14 is introduced. In the aerobic tank 16, the water d to be treated and the activated sludge present in the aerobic tank 16 are mixed. As a result, the activated sludge proliferates while breathing in the air supplied by the aeration, and decomposes the organic matter contained in the water to be treated d. From the aerobic tank 16, the water to be treated e from which the organic matter has been removed in this manner is discharged.

The second sedimentation tank 18 is provided after the aerobic tank 16, and the water to be treated e discharged from the aerobic tank 16 is introduced. The water e to be treated flows slowly through the second sedimentation tank 18, and during this time it proliferates in the aerobic tank 16, and the floc-like activated sludge f contained in the water e to be treated flows into the second sedimentation tank 18. settle to the bottom. The supernatant liquid of the water to be treated e from which the activated sludge f has been removed in this manner is discharged from the second sedimentation tank 18 as the treated water α that has undergone sewage treatment.

The wastewater treatment system 10 of the first embodiment further includes, for example, a gravity thickening tank 20, a mechanical It has a thickener 22 , a sludge digestion tank 24 and a sludge dewaterer 26 .

The sludge c settled on the bottom of the first sedimentation tank 14 is withdrawn from the bottom of the first sedimentation tank 14 and sent to the gravity thickening tank 20 where it is concentrated by natural sedimentation. The thickened sludge g (hereinafter referred to as “thickened sludge g”) is sent to the sludge digestion tank 24 . On the other hand, the supernatant liquid is collected from the gravity concentration tank 20 by this concentration. This water is referred to as separation liquid h1.

The activated sludge f settled on the bottom of the second sedimentation tank 18 is withdrawn from the bottom of the second sedimentation tank 18, part of it is sent to the mechanical thickener 22, and most of the rest is returned to the aerobic tank 16. be done. The mechanical thickener 22 thickens the activated sludge f by centrifugal thickening, for example. As a result, the thickened sludge i, which is the thickened activated sludge f, is sent to the sludge digestion tank 24 . On the other hand, by this concentration, water is recovered from the activated sludge f in the mechanical thickener 22 . This water is referred to as separation liquid h2.

The sludge digestion tank 24 reduces the volume of the thickened sludge g from the gravity thickening tank 20 and the thickened sludge i from the mechanical thickener 22 by methane fermentation. Methane gas can be reused as an energy source. The thickened sludge g and i are thus reduced in volume and stabilized through methane fermentation to become digested sludge j.

The sludge dehydrator 26 dehydrates the digested sludge j discharged from the sludge digestion tank 24 . As a result, a solid k in which the digested sludge j is concentrated is obtained. The solid k contains phosphorus and can be used as fertilizer, for example. On the other hand, water is recovered by dehydration. This water is referred to as separation liquid h3.

All of the separated liquids h1, h2 and h3 (hereafter, the separated liquids h1, h2 and h3 are collectively referred to as "separated liquid h") contain relatively high concentrations of organic substances, nitrogen and phosphorus.

If such a separated liquid h is returned to the upstream side of the sewage treatment flow like the pretreatment equipment 12 or the first sedimentation tank 14, a large amount of aeration power will be required in the aerobic tank 16, and the system This may lead to an increase in the overall load and, as a result, degrade the water quality of the treated water α. For this reason, the wastewater treatment system 10 is provided with a rotating fiber unit 40 and a small aerobic tank 50 in order to efficiently remove the organic matter, nitrogen, and phosphorus components contained in the separated liquid h. For this reason, the rotating fiber unit 40 is connected to a separation liquid introduction line D commonly used for feeding the separation liquids h1, h2 and h3.

FIG. 2 is a conceptual diagram showing a configuration example of a rotating fiber unit.

The rotating fiber unit 40 is a device for purifying the separated liquid h with activated sludge in which Bacillus bacteria are dominant and the rotating fiber unit. The rotating fiber unit 40 is provided with a separation liquid h from a separation liquid introduction line D provided on the left side of the drawing, and the separation liquid h is purified water m to be purified. , as shown on the right side of the drawing, the liquid is discharged from the side opposite to the introduction side.

FIG. 2 shows a configuration example of the rotating fiber unit 40 viewed from above, and the rotating fiber unit 40 is arranged in parallel at a constant interval L in a water treatment tank 41 into which the separation liquid h is introduced. A plurality of rotating contact bodies 42 are provided.

FIG. 3 is a conceptual diagram showing a configuration example of the rotating fiber unit viewed from the front side (left side in FIG. 2). However, the separation liquid introduction line D is not shown in FIG.

Each rotary contact member 42 has a through hole at the center of the circle, and each rotary contact member 42 is fixed to a shaft 43 inserted into the through hole. As a result, the rotary contact members 42 are arranged parallel to each other with a constant interval L along the long axis direction of the shaft 43 (horizontal direction in FIG. 2).

The surface of each rotary contactor 42 has a three-dimensional mesh structure to which microorganisms are likely to adhere.

A separation liquid h is introduced into the water treatment tank 41 . However, as shown in FIG. 3, each rotating contact member 42 is not entirely immersed in the separation liquid h, but only a lower portion thereof is immersed in the separation liquid h. The upper side of the part is installed in the water treatment tank 41 so as to be in the gas phase.

As a result, each rotating contact member 42 is in contact with the air on its upper side and immersed in the separation liquid h on its lower side.

The upper side of the water treatment tank 41 is configured with a cover 45 that prevents the invasion of ultraviolet rays, rainwater, and the like.

The shaft 43 is rotated by the driving force from the motor 48, and thereby each rotating contact member 42 also rotates around the shaft 43 as indicated by the arrow R shown in FIG.

In this way, each rotating contact member 42 rotates as indicated by an arrow R in FIG. 3 along with the rotation of the shaft 43, so that the Bacillus bacteria adhering to each rotating contact member 42, particularly the contact member, become dominant. In the gas phase, the activated sludge takes in oxygen from the air, and in the liquid phase, which is while it is immersed in the separated liquid h, oxidatively decomposes the organic matter in the separated liquid h, and nitrates the nitrogen component. Or denitrify. As a result, the water to be purified m from which the organic substances and nitrogen components have been removed from the separated liquid h is discharged from the water treatment tank 41 .

In this way, in the rotating fiber unit 40, the Bacillus bacterium, which has excellent organic matter and nitrogen removal capabilities, dominates the activated sludge, thereby removing 50 to 60% of the organic matter in the separated liquid h and reducing nitrogen to 70%. % or more, it can be discharged as water to be purified m.

Dominance is defined as a state in which 10 ⁷ CFU/mL or more of Bacillus bacteria are present in activated sludge.

An air diffusion pipe 46 is provided below the rotary contactor 42 in the water treatment tank 41 . Further, outside the water treatment tank 41, an air blower 47 for sending air to the diffuser pipe 46 is provided.

A large number of small holes (not shown) are provided on the surface of the diffuser pipe 46, and the air supplied from the blower 47 becomes bubbles n when passing through the holes. Since the bubbles n rise in the separated liquid h, the separated liquid h is agitated in the water treatment tank 41 .

The stirring of the separated liquid h in the water treatment tank 41 is not limited to the use of the air bubbles n from the air diffuser 46, but may be performed using an underwater stirrer or any other method.

In addition, when the air bubbles n collide with the rotating contactor 42 located above the air diffuser 46, the activated sludge adhering to the rotating contactor 42 (dominated by bacteria belonging to the genus Bacillus) is removed from the rotating contactor 42. Since the bubbles n are separated, the bubbles n can also be used for adjusting the amount of activated sludge adhering to the rotary contactor 42 .

In this manner, the blower 47 constantly feeds air into the air diffuser pipe 46 in order to adjust the amount of activated sludge adhering to the rotary contactor 42 and to agitate the separated liquid h. However, since the air bubbles n generated from the diffuser pipe 46 are coarse, the inside of the water treatment tank 41 becomes a facultative anaerobic state.

The rotating fiber unit 40 having such a configuration can also be called an RBC (Rotating Biological Contactor).

A small aerobic tank 50 is provided behind the rotating fiber unit 40 . The water to be purified m discharged from the rotating fiber unit 40 is introduced into the small aerobic tank 50 . In the small aerobic tank 50, the water to be purified m is aerated.

As a result, in the small aerobic tank 50, as in the case of the aerobic tank 16, the activated sludge existing in the small aerobic tank 50 proliferates while breathing with the air supplied by aeration, and the water to be purified Organic matter contained in m is decomposed.

Further, by connecting the rotating fiber unit 40, which is in an anaerobic state by adjusting the amount of air from the diffuser pipe 46, and the small aerobic tank 50, in which aerobic treatment is performed, the water to be purified m is anaerobic-aerobic Since the treatment is performed, the phosphorus removal efficiency from the water to be purified m is also enhanced.

Further, in the small aerobic tank 50, nitrification liquid q is generated by aeration. In an anaerobic environment such as the rotating fiber unit 40, the nitrified liquid q changes into nitrogen gas and can be released into the air. Therefore, it is preferable to return the nitrified liquid q generated in the small aerobic tank 50 to the rotating fiber unit 40 . For this purpose, a nitrifying liquid return line E for returning the nitrifying liquid q from the small aerobic tank 50 to the rotating fiber unit 40 is provided. Furthermore, the small aerobic tank 50 may be provided with a return pump (not shown) for this return. Considering the fluctuation of the nitrogen load in the separated liquid h, etc., it is desirable to use an inverter or the like with a variable return water amount for this return pump.

Thus, from the small aerobic tank 50, the water to be treated p from which the organic matter, phosphorus, and nitrifying liquid q have been removed is discharged.

The water to be treated p discharged from the small aerobic tank 50 is, for example, not upstream of the sewage treatment flow such as the pretreatment facility 12 or the first sedimentation tank 14, but to the aerobic tank 16 via the return line B. sent back. This is also for making the sludge in the rotating fiber unit 40, the small aerobic tank 50, the aerobic tank 16, and the second sedimentation tank 18 in a state in which Bacillus bacteria are dominant.

Similarly, in order to maintain the state in which Bacillus bacteria are dominant in the sludge in the rotary fiber unit 40, the small aerobic tank 50, the aerobic tank 16, and the second sedimentation tank 18, Of the activated sludge f, a part of the activated sludge f that has not been sent to the mechanical thickener 22 is provided with an introduction line A for introducing into the rotary fiber unit 40, and is sent to the rotary fiber unit 40 via the introduction line A. Activated sludge f may be introduced.

As another countermeasure for maintaining the state in which bacteria of the genus Bacillus are dominant, an activator injection device 62 for injecting an activator r containing minerals necessary for the growth of bacteria of the genus Bacillus is attached to the rotating fiber unit 40. It may be provided in the front stage. This is realized, for example, by injecting the activator r from the activator injector 62 into the separation liquid introduction line D. As shown in FIG. Alternatively, the activator r from the activator injector 62 may be injected into the small aerobic tank 50 .

Incidentally, the nitrogen concentration in the separated liquid h may be higher than the organic substance concentration. In this case, in order to increase the nitrogen removal efficiency in the rotating fiber unit 40, a solvent such as methanol or molasses, which has the effect of increasing the C/N (carbon/nitrogen) ratio in the separated liquid h, is added to the upstream stage of the rotating fiber unit 40. A modifier injector 60 is provided for injecting a carbon-containing modifier s. The amount of modifier s injected by the modifier injector 60 can be determined in consideration of the BOD/N (soluble contaminants/nitrogen) ratio.

As described above, according to the waste water treatment system 10 of the first embodiment, the organic matter, nitrogen, and phosphorus contained in the separated liquid h generated in the solid-liquid separation in the sludge treatment process are mainly removed by the rotating fiber unit 40 and a small aerobic tank 50 can be used to efficiently remove it.

In particular, the application of the rotating fiber unit 40 has made it possible to hold sludge at a higher concentration than in the prior art, so that it is possible to improve the removal efficiency of organic matter, nitrogen, and phosphorus.

Since the load on each facility of the waste water treatment system 10 of the first embodiment is reduced by improving the removal efficiency of organic matter, nitrogen, and phosphorus in this way, it is possible to prevent deterioration of the water quality of the treated water α.

Furthermore, by reducing the load on the facility, it is possible to reduce the aeration power in the aerobic tank 16, so that energy can be saved. Alternatively, the aerobic tank 16 can be downsized, and in this case, the installation space for the aerobic tank 16 can be reduced.

(Second embodiment)
A waste water treatment system to which the waste water treatment method of the second embodiment is applied will be described.

FIG. 4 is a conceptual diagram showing a configuration example of a wastewater treatment system to which the wastewater treatment method of the second embodiment is applied.

In the explanation of the wastewater treatment system 10a of the second embodiment, the same parts as those of the wastewater treatment system 10 of the first embodiment are denoted by the same reference numerals to avoid redundant explanation.

The wastewater treatment system 10a has a configuration in which the activator injection device 62 and the introduction line A are removed from the wastewater treatment system 10. As shown in FIG.

In the present embodiment, it is assumed that the raw water a is originally dominated by bacteria belonging to the genus Bacillus. It is known that Bacillus bacteria become dominant by injecting mineral components such as silica and magnesium as Bacillus bacteria activators. Therefore, when the raw water a is rich in these components, the Bacillus genus bacteria become dominant even without the injection of the activator r. Even if the introduction line A for introducing the activated sludge f into the rotary fiber unit 40 is not provided, the organic matter contained in the separated liquid h generated by the solid-liquid separation in the sludge treatment process can be removed as described in the first embodiment. , nitrogen, and phosphorus can be efficiently removed primarily by the rotating fiber unit 40 and the small aerobic tank 50 .

In addition, in order to confirm that Bacillus bacteria are actually dominant, the water to be treated e in the aerobic tank 16 is sampled, and the concentration of Bacillus bacteria is 10 ⁷ CFU / mL or more. It is necessary to analyze whether there is

As described above, according to the wastewater treatment system 10a of the second embodiment, the same effects as those of the first embodiment can be obtained from the wastewater treatment system 10 of the first embodiment with the activator injection device 62 and Even with a configuration in which the introduction line A is deleted, the effect can be achieved.

That is, it is possible to simplify the equipment without lowering the performance, thereby reducing the initial cost. In addition, since the Bacillus bacterium to be added at the time of starting up the system is unnecessary, it can contribute to the reduction of the initial cost. Furthermore, since it is no longer necessary to prepare the activator r, the running cost required for arranging the activator r can also be eliminated.

Thus, when treating raw water a in which Bacillus bacteria are originally dominant, it is possible to treat at a lower cost than otherwise.

(Third embodiment)
A waste water treatment system to which the waste water treatment method of the third embodiment is applied will be described.

FIG. 5 is a conceptual diagram showing a configuration example of a wastewater treatment system to which the wastewater treatment method of the third embodiment is applied.

In the explanation of the wastewater treatment system 10b of the third embodiment, the same parts as those of the wastewater treatment system 10 of the first embodiment are denoted by the same reference numerals to avoid redundant explanation.

In the wastewater treatment system 10b, the small aerobic tank 50 and the nitrified solution return line E for returning the nitrified solution q produced in the small aerobic tank 50 to the rotating fiber unit 40 are removed from the wastewater treatment system 10. Instead, a nitrified liquid return line F for returning the nitrified liquid t produced in the aerobic tank 16 to the rotating fiber unit 40 is provided.

In order to omit the small aerobic tank 50 in this way, the contamination load of the water to be purified m discharged from the rotating fiber unit 40 must be low, and the water quality of the treated water α must satisfy the allowable value. It is assumed that there is no problem in terms of processing capacity, such as

For example, when adding the wastewater treatment system 10b to the existing sewage treatment plant, the small aerobic tank 50 is installed after considering the existing treatment capacity and the pollution load of the water to be purified m discharged from the rotating fiber unit 40. It is possible to determine whether or not to omit.

On the other hand, in the case of a new sewage treatment plant, the aerobic tank 16 can be designed by considering the contamination load of the water to be purified m introduced into the aerobic tank 16 from the rotating fiber unit 40 via the return line B. , the small aerobic tank 50 can be omitted.

By omitting the small aerobic tank 50 as in the wastewater treatment system 10b of the third embodiment, it is possible to reduce construction costs and installation space.

(Fourth embodiment)
A waste water treatment system to which the waste water treatment method of the fourth embodiment is applied will be described.

FIG. 6 is a conceptual diagram showing a configuration example of a waste water treatment system to which the waste water treatment method of the fourth embodiment is applied.

In the description of the wastewater treatment system 10c of the fourth embodiment, the same reference numerals are used to denote the same parts as those of the wastewater treatment system 10b of the third embodiment, and repeated explanations are avoided.

The wastewater treatment system 10c has a configuration in which the activator injection device 62 and the introduction line A are removed from the wastewater treatment system 10b.

Furthermore, also in this embodiment, as in the second embodiment, it is assumed that the raw water a is originally dominated by bacteria of the genus Bacillus.

The waste water treatment system 10c is a modification of the waste water treatment system 10b that treats raw water a in which Bacillus bacteria are originally dominant. That is, when the wastewater treatment system 10b treats the raw water a in which Bacillus bacteria are originally dominant, the activator injection device 62 and the introduction line A can be deleted as described in the second embodiment. can be done. Therefore, the waste water treatment system 10c has a configuration in which the activator injection device 62 and the introduction line A are removed from the waste water treatment system 10b.

As described in the third embodiment, the application of the waste water treatment system 10c of the fourth embodiment requires that the pollution load of the water to be purified m discharged from the rotating fiber unit 40 is low, and the water quality of the treated water α is high. It is assumed that Bacillus bacteria are originally dominant in the raw water a, in addition to having no problem in terms of treatment capacity, such as satisfying the allowable value. If such a premise is satisfied, the wastewater treatment system 10c can be applied. As described in the second embodiment, the wastewater treatment system 10c reduces the initial cost due to the elimination of the activator injection device 62 and the introduction line A, reduces the initial cost due to the elimination of Bacillus bacteria, and reduces the initial cost due to the elimination of the activator injection device 62 and the introduction line A. As described in the third embodiment, the omission of the small aerobic tank 50 reduces the construction cost and installation space.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

Claims (13)

In a wastewater treatment system that purifies wastewater,
In order to purify the separated liquid generated by solid-liquid separation in the sludge treatment process for treating the waste water by making the Bacillus bacteria present in the activated sludge dominant, the activity that makes the Bacillus bacteria dominant Rotating to purify the separated liquid with activated sludge in which the Bacillus genus bacteria adhered to the fibrous bodies are dominant, while the fibrous bodies having a three-dimensional network structure to which the sludge is attached are partially immersed in the separated liquid. Equipped with a fiber unit,
The sludge treatment step includes a wastewater aeration aerobic tank in which the wastewater from which sludge has been removed is aerated, and sludge contained in the wastewater after aeration in the wastewater aeration aerobic tank is precipitated. and a post-aeration sedimentation tank for
The separated liquid is a liquid generated by solid-liquid separation from the sludge precipitated in the post-aeration sedimentation tank.
Wastewater treatment system. The sludge treatment step further includes a pre-aeration sedimentation tank for precipitating the sludge contained in the waste water and generating the waste water from which the sludge has been removed, which is supplied to the waste water aeration aerobic tank,
The separated liquid further includes a liquid generated by solid-liquid separation from the sludge precipitated in the pre-aeration sedimentation tank.
The wastewater treatment system according to claim 1. 3. The wastewater treatment system according to claim 1 , further comprising an aerobic tank for aeration of the separated liquid to be purified, which aerates the separated liquid purified by the rotating fiber unit. Claim 3 , further comprising a first return line for returning the nitrified liquid generated by aeration in the aeration tank for aeration of the separated liquid to be purified from the aerobic tank for aeration of the separated liquid to be purified to the rotating fiber unit. A wastewater treatment system as described. 3. A first injection device for injecting a carbon-containing modifier into the separated liquid before being purified by the rotating fiber unit in order to increase the C/N ratio of the separated liquid. A wastewater treatment system as described. Further comprising a second injection device for injecting an activator containing minerals necessary for the growth of the Bacillus bacteria into the separated liquid before or after being purified by the rotating fiber unit. 3. A wastewater treatment system according to Item 1 or 2 . 3. The wastewater treatment system according to claim 1, further comprising a first introduction line for withdrawing sludge settled in said post-aeration sedimentation basin from said post-aeration sedimentation basin and introducing the sludge into said rotary fiber unit. 3. The wastewater treatment system according to claim 1, further comprising a second return line for returning part of said wastewater after being aerated in said wastewater aeration aerobic tank to said rotating fiber unit. 3. The waste water treatment system according to claim 1, further comprising a third return line for returning said separated liquid purified by said rotating fiber unit to said aerobic tank for waste water aeration . an aerobic tank for aerating the separated liquid to be purified , which aerates the separated liquid purified by the rotating fiber unit;
3. The wastewater treatment system according to claim 1, further comprising a fourth return line for returning said separated liquid aerated in said aerobic tank for aeration of the separated liquid to be purified to said aerobic tank for wastewater aeration. . 11. A first return line for returning the nitrified liquid generated by aeration in said aeration tank for aeration of separated liquid to be purified from said aerobic tank for aerated separated liquid to be purified to said rotary fiber unit. A wastewater treatment system as described. 3. The wastewater treatment system according to claim 1 , wherein said wastewater is dominated by said bacteria belonging to the genus Bacillus. A wastewater treatment method performed by a wastewater treatment system to purify wastewater, comprising:
Precipitating the sludge contained in the wastewater in a first sedimentation tank,
aeration in an aerobic tank against the wastewater from which sludge has been removed by sedimentation in the first sedimentation tank;
Precipitating the sludge contained in the wastewater after aeration in the aerobic tank in a second sedimentation tank,
In order to purify the separated liquid generated by solid-liquid separation from the sludge precipitated in the first sedimentation tank and the sludge precipitated in the second sedimentation tank with activated sludge in which bacteria of the genus Bacillus are dominant, the bacillus In a rotating fiber unit comprising a fibrous body to which a bacterium of the genus is attached, the separation is performed by the Bacillus bacterium attached to the fibrous body while rotating the fibrous body so that a part of the fibrous body is immersed in the separation liquid. Wastewater treatment method for purifying liquid.

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