WO2013168680A1

WO2013168680A1 - Wastewater treatment system and treatment method therefor

Info

Publication number: WO2013168680A1
Application number: PCT/JP2013/062780
Authority: WO
Inventors: 眞小島
Original assignee: 大成企業株式会社
Priority date: 2012-05-07
Filing date: 2013-05-02
Publication date: 2013-11-14
Also published as: JP5189688B1; CN104321285A; CN104321285B; JP2013233482A

Abstract

This wastewater treatment system comprises: an anaerobic region to which wastewater that has not passed through a sedimentation tank, i.e., wastewater in which solids having a small size and a low specific gravity are contained as such without being separated therefrom as raw sludge, is supplied first; and an oxygen-free region and an aerobic region which have been consecutively formed by causing the regions to communicate with each other through the openings of a partition as channels. In the system and method, the percentage of return sludge is kept at 30-60%, the concentration of active sludge (mixed liquor suspended solid (MLSS)) is kept at 2,600-5,000 mg/L, excluding 5,000 mg/L, and the concentration of bacteria belonging to the genus Bacillus is kept at 10⁸-10¹⁰ cells/mL.

Description

Wastewater treatment system and treatment method

The present invention relates to an advanced wastewater treatment system for biologically denitrifying and dephosphorizing wastewater such as sewage, domestic wastewater, human waste, and industrial wastewater, and a treatment method thereof, and more particularly to a wastewater treatment facility of a standard activated sludge method. The present invention relates to a wastewater treatment system developed as an advanced treatment using activated sludge in which bacteria predominate at a high concentration and a treatment method thereof.

Conventionally, as a method for biological treatment of wastewater such as sewage, domestic wastewater, human waste, industrial wastewater, etc., the floating biological method that mainly treats aerobic microorganisms in suspension and treats sewage, and organisms composed of various microorganisms. There is a biofilm method that grows membranes to treat sewage. In addition, typical activated sludge method, oxidation ditch (OD) method, membrane separation activated sludge method, etc. are known as representative of the former floating organism method, and each has different system configuration and treatment method. Is used.

The wastewater treatment system to which the standard activated sludge method is applied is basically composed of a first settling tank 101, a reaction tank 102, and a final settling tank 103 as shown in FIG. Then, according to the standard activated sludge method, the raw sludge 141 is separated in the first sedimentation basin 101 from the wastewater supplied through the flow path 111, and then the wastewater supplied through the flow path 112 is added to the reaction tank 102. The oxygen is dissolved by aeration and aeration at the same time and mixed with stirring. The activated sludge mainly composed of aerobic microorganisms is suspended and retained therein, and then activated in the final sedimentation basin 103 supplied through the channel 113. Sludge is allowed to settle, and the supernatant water is discharged through the channel 114 as discharge water. The reaction tank 102 may be called an aeration tank, a reaction tank, an aeration tank, a biological treatment tank, etc., and the aeration time is 6 to 8 hours. A part of the activated sludge settled in the final sedimentation basin 103 is returned to the reaction tank 102 again through the flow path 115 as return sludge 142, and the rest passes through the flow path 117 as surplus sludge 143 and the mechanical concentration equipment 105. Concentrate with. The raw sludge 141 first separated in the settling basin 101 is concentrated in the gravity concentration facility 104 through the flow path 116 and then mixed with the excess sludge 143 concentrated in the mechanical concentration facility 105 in the mixing tank 106 and dehydrated. It is applied to the facility 107.

On the other hand, an anaerobic / anoxic / aerobic method (A20 method) is known as an advanced treatment aimed at removing nitrogen and phosphorus. This is a method in which the reaction tank is placed in the order of an anaerobic tank, an anaerobic tank, and an aerobic tank, and waste water and return sludge are allowed to flow into the anaerobic tank and at the same time the nitrification solution in the aerobic tank is circulated to the anoxic tank. It is.

In addition, Bacillus bacteria corrode and deteriorate the electrical and mechanical equipment of wastewater treatment facilities, causing deterioration of the working environment and at the same time inhibiting the metabolism of adenosine triphosphate (ATP), which is said to be the energy currency of living organisms. Ability to specifically remove hydrogen sulfide that weakens the activity of microorganisms and makes sewage treatment unstable, the ability to solubilize biochemical persistent organic substances (BOD) with strong enzyme activity, protein, starch, etc. It is a highly functional microorganism with excellent ability to promote solid-liquid separation in the final sedimentation basin because of its excellent decomposition ability and nitrogen removal ability, and because the cell wall is covered with an adhesive substance. . In addition, normal activated sludge has a reduced ability of water with a decrease in water temperature, which may reduce nitrogen removal ability in the reaction tank and solid-liquid separation in the final sedimentation basin, whereas Bacillus bacteria are highly effective. Activated sludge that is dominated by concentration has a stable treatment capacity even at low temperatures. And since the Bacillus genus bacteria are aerobic and facultative anaerobic microbial cells, they can grow with fermentation energy not only in an aerobic tank but also in an anaerobic tank, and assimilate ammonia nitrogen etc. The concentration of ammonia nitrogen discharged from the discharged water flowing out through the channel 114 is significantly reduced.

By combining these standard activated sludge method, anaerobic / anoxic / aerobic method and Bacillus bacteria, it is not necessary to prepare anaerobic tank, anaerobic tank, aerobic tank, etc. separately. There is a wastewater treatment method that can be carried out without major modification to treatment facilities, has excellent wastewater treatment capabilities such as denitrification and dephosphorization, and can reduce operating costs. It has been proposed (see, for example, Patent Document 1).

In this patent document 1, the anaerobic region and the aerobic region are continuously formed, and the concentration (MLSS) of activated sludge provided in the reaction tank is controlled at 2000 to 2500 mg / liter, It is disclosed that the concentration of Bacillus bacteria in the activated sludge is increased to 10 ⁸ to ¹⁰ cells / milliliter and wastewater treatment is performed in a state where the concentration is maintained at this high concentration.

In addition, in organic biological wastewater treatment methods using anaerobic, anoxic, and aerobic methods, organic wastewater treatment methods that can significantly suppress the generation of excess sludge have been proposed (for example, patent documents). 2).

In this Patent Document 2, sludge in a biological treatment tank consisting of an anaerobic tank, an anaerobic tank, and an aerobic tank is made into a sludge in which Bacillus bacteria are dominant species, and an anaerobic tank of a biological treatment tank, It is disclosed that the sludge concentration in the anaerobic tank and the aerobic tank is maintained at about 4000 to 20000 mg / liter.

JP 2009-131773 A JP 2007-105630 A

In general, solids contained in wastewater are precipitated in the descending order of slit-shaped or mesh-shaped screens having a mesh width of about 50 mm to 1 mm, sand settling tanks for separating sand and stone, and the remaining solids. It is removed in the first sedimentation basin that separates as raw sludge. Depending on the type and amount of solids contained in the wastewater, the sand settling tank may be omitted.

As shown in FIG. 4, the standard activated sludge method includes an initial sedimentation basin 101 and a final sedimentation basin 103, and raw sludge 141 separated in the initial sedimentation basin 101 and excess sludge 143 separated in the final sedimentation basin 103. Therefore, the operation and maintenance management is complicated. In addition, raw sludge 141 that is being solid-liquid separated in the first sedimentation tank 101, raw sludge 141 that is sent to the dehydration facility 107 after passing through the flow path 116, waste water that is flowing through the flow path 112, the reaction tank 102, and the flow path 113, Malodors such as hydrogen sulfide generated from the return sludge 142 flowing through the flow path 115, the activated sludge being solid-liquid separated in the final sedimentation basin 103, and the surplus sludge 143 that is sent to the dehydration equipment 107 after passing through the flow path 117 The corrosive gas possessed causes a deterioration of the working environment and the environment of the adjacent land, leading to the deterioration of the electrical machinery equipment. However, countermeasures against these gases are usually symptomatic in the gas phase by a biological deodorization tower or the like. It becomes expensive because it becomes a thing.

In the wastewater treatment method disclosed in Patent Document 1, an activated sludge containing a Bacillus genus bacterium that is predominated at a high concentration and retained is combined with a standard activated sludge method and an anaerobic / anoxic / aerobic method. The waste sludge was used to decompose odors from excess sludge. That is, among the six corrosive gas generation sources listed above, waste water is flowing through the flow path 112, the reaction tank 102, and the flow path 113 in FIG. Odor removal was performed on the four generation sources of activated sludge being solid-liquid separated in the sedimentation basin 103 and surplus sludge 143 that was sent to the dehydration facility 107 after passing through the flow path 117. In addition, not only a part of the activated sludge settled in the final sedimentation basin is returned to the reaction tank, but the remaining part is also returned to the initial sedimentation basin, so that the Bacillus bacteria contained in the return sludge are returned. Due to the effect, the generation of bad odor from raw sludge 141 during solid-liquid separation in the first sedimentation basin 101 of FIG. 4 and the remaining two sources of raw sludge 141 sent to the dehydration facility 107 after passing through the flow path 116 is suppressed. I was able to expect that. However, if bad odor generation from raw sludge cannot be sufficiently suppressed due to a decrease in the concentration of bacteria belonging to the genus Bacillus, symptomatic treatment in the gas phase as in the past for the remaining two sources There was a problem that it was necessary to implement anti-odor measures. Moreover, there existed a problem that it was necessary to process two systems of sludge, raw sludge 141 and surplus sludge 143.

In the wastewater treatment method disclosed in Patent Document 2, the amount of excess sludge generated was reduced by the combination as described above and the effect of Bacillus bacteria. However, among the foreign substances such as sand and solids removed by the pretreatment equipment such as the sedimentation tank and screen, there is a problem that it is necessary to take measures against bad odors especially for the foreign substances removed by the sedimentation tank. . In addition, there is a problem that it is necessary to treat two systems of sludge, raw sludge and surplus sludge generated from impurities removed in the sedimentation tank.

The purpose of the present invention is to solve the above-mentioned problems of the prior art, and to develop advanced treatment using activated sludge in which the concentration of Bacillus bacteria predominates in the wastewater treatment facility of the standard activated sludge method, The sludge to be concentrated and dewatered by abolishing the pond is made into only one surplus sludge, and wastewater containing raw sludge is generated from raw sludge by decomposing activated sludge containing Bacillus bacteria in the reaction tank. This eliminates the need to implement symptomatic odor countermeasures in the gas phase and reliably prolong the life of electrical machinery and equipment. At the same time, the work environment can be improved steadily, because the sludge of raw sludge is not first separated in the settling basin, but is reduced by being decomposed through the reaction tank while contained in the wastewater, Dirty system The amount generated can be reduced from 85 to 90% compared to the previous product, and 10 to 15% can be reduced. As a result of eliminating the need for the gravity concentration facility 104, mixing tank 106, and related piping, the equipment layout for sludge treatment is extremely high. To provide a wastewater treatment system and its treatment method that can reduce the running cost including the initial cost, maintenance cost, power consumption and disposal cost of dehydrated cake, etc. It is in.

In order to achieve the above-mentioned object, the present inventor has conducted earnest research. As a result, first, as shown in FIG. 5, a part of the activated sludge settled in the final settling basin 103 is used as the return sludge 142, and the flow paths 115, 115a. The remaining sludge is not only returned to the reaction tank 102 through the

flow path

115 and 115b but also returned to the first settling tank 101 to eliminate excess sludge, and the sludge to be concentrated and dehydrated is separated in the first settling tank 101. It is conceived that there is only one mixed sludge 144 that passes through the flow path 116, and passes through the remaining two sources, namely, raw sludge 141 that is firstly solid-liquid separated in the settling basin 101, and the flow path 116. After that, it was found that the corrosive gas having bad odor such as hydrogen sulfide generated from the raw sludge 141 sent to the dewatering equipment 107 can be removed. This mixed sludge 144 is a conventional wastewater treatment shown in FIG. Although the raw sludge 141 and the excess sludge 143 in the stem are simply mixed, the excess sludge 143 is reduced by being decomposed through the reaction tank 102 while being contained in the waste water. On the other hand, the raw sludge 141 was first separated in the settling basin 101 before flowing into the reaction tank 102, and as a result, the sludge at the time of concentration and dewatering was compared with the amount of sludge at the time of separating raw sludge (before flowing into the reaction tank 102). Since the amount was not reduced, it was found that the sludge generation amount of the entire system could not be reduced even if the sludge to be concentrated and dehydrated as shown in FIG.

Therefore, as a result of further earnest research, the inventor has continuously formed anoxic regions and aerobic regions as in Patent Document 1, and at the same time, in order to enhance the ability of Bacillus bacteria, The MLSS concentration of the activated sludge provided in the tank 2 is further increased from 2000 to 2500 mg / liter described in Patent Document 1, and is lower than about 4000 to 20000 mg / liter described in Patent Document 2, and is 2600 mg / liter or more and 5000 mg / liter. Maintain and manage at an MLSS concentration of less than liter, more preferably maintain at an MLSS concentration of 3000 mg / liter or more and less than 4000 mg / liter, and at the same time, set the ratio of the total residence time of the anaerobic region and anaerobic region to the residence time of the aerobic region Maintain within 1.0 to 2.0, more preferably within 1.1 to 1.9. By managing it was found that it is possible to eliminate the primary sedimentation. Furthermore, as described above, in the configuration of FIG. 5, the amount of raw sludge is reduced because the amount of sludge at the time of concentration and dehydration is not reduced with respect to the amount of sludge at the time of separation of raw sludge (before flowing into the reaction tank 102). On the other hand, by eliminating the raw sludge by abolishing the first sedimentation basin and making the sludge to be concentrated and dehydrated into only one system of surplus sludge separated in the final sedimentation basin, the sludge for raw sludge can be reduced. Since it is not separated in the first settling basin 101 but is reduced by being decomposed through the reaction tank 102 while contained in the wastewater, the amount of surplus sludge in the raw sludge can be reduced, and the sludge of the entire system can be reduced. The present inventors have found that it is possible to provide a wastewater treatment system capable of reducing the generation amount and achieve the above object and a treatment method thereof, and have achieved the present invention. That is, the main differences between the present invention and the wastewater treatment method disclosed in Patent Document 1 are the presence / absence of the first sedimentation tank 101, the value of the MLSS concentration of activated sludge provided in the reaction tank 2, and the residence time of the aerobic region. This is the presence or absence of a description regarding the ratio of the total residence time of the anaerobic region and the anaerobic region, and the main difference between the present invention and the wastewater treatment method disclosed in Patent Document 2 is not in the present invention in addition to these three points. A point in which a reaction tank in which an oxygen region and an aerobic region are continuously formed is used, and in the present invention, a mineral powder addition means is used in order to maintain the concentration of Bacillus bacteria within a predetermined concentration range. It is.

That is, in order to achieve the above object, a first aspect of the present invention, anaerobic region has anoxic region and the aerobic region,該嫌gas area, in the order of anoxic region and the aerobic region, 10 ⁸ -10 ¹⁰ / ml of active sludge having a second concentration of 2600 mg / liter or more and less than 5000 mg / liter containing a first concentration of bacteria belonging to the genus Bacillus, the raw sludge contained in the wastewater is decomposed and the wastewater A reaction tank for removing nitrogen and phosphorus from the reaction tank, a sedimentation basin for precipitating and separating activated sludge contained in the treated wastewater discharged from the reaction tank, and activated sludge in the reaction tank. In order to maintain 2 concentration, sludge returning means for returning a predetermined ratio from the activated sludge separated in the sedimentation basin to the reaction tank as a return sludge, and surplus residual activated sludge separated in the sedimentation basin Sludge Based on the concentration of waste water supplied into the reaction tank, in order to maintain the concentration of Bacillus bacteria in the activated sludge returned from the sedimentation basin at the first concentration, There is provided a wastewater treatment system comprising mineral powder addition means for adding mineral powder mainly composed of silicic acid to wastewater supplied to the reaction tank.

Moreover, in order to achieve the said objective, the 2nd aspect of this invention is the order of this anaerobic region, anaerobic region, and an aerobic region by the reaction tank which has an anaerobic region, an anaerobic region, and an aerobic region, Decomposing raw sludge contained in wastewater using activated sludge having a second concentration of 2600 mg / liter or more and less than 5000 mg / liter, containing 10 ⁸ to 10 ¹⁰ cells / milliliter of a first concentration of Bacillus bacteria, The waste water is treated to remove nitrogen and phosphorus, and the activated sludge contained in the treated waste water discharged from the reaction tank is precipitated and separated by a sedimentation basin, and the activated sludge in the reaction tank is separated from the waste water. In order to maintain 2 concentrations, the sludge return means returns a predetermined ratio from the activated sludge separated in the settling basin as return sludge to the reaction tank, and the concentrated dehydration means returns the sludge in the settling basin. In order to concentrate and dehydrate the separated activated sludge as surplus sludge, and to maintain the Bacillus bacteria in the activated sludge returned from the sedimentation basin at the first concentration, the reaction is performed by means of mineral powder addition means. The present invention provides a wastewater treatment method in which mineral powder mainly composed of silicic acid is added to wastewater supplied to the reaction tank based on the concentration of wastewater supplied into the tank.

Here, in the first and second embodiments, the sludge returning means returns the activated sludge in the reaction tank to 3000 mg / liter or more and 4000 mg / liter by returning the returned sludge to the reaction tank. More preferably, it is maintained at a lower concentration.
The sludge return means preferably adjusts the ratio of the return sludge to the activated sludge separated in the sedimentation basin within a range of 30 to 60%.
The residence times of the waste water in the anaerobic region, the anaerobic region, and the aerobic region are 1.5 to 2.0 hours, 3.5 to 4.5 hours, and 3.5 to 4.5 hours, respectively. Preferably there is.
Furthermore, it is preferable to provide a control means for maintaining the oxidation-reduction potential in the anaerobic region at −150 to −350 mV, and the amount of dissolved oxygen in the wastewater in the aerobic region at 2.0 to 3.5 mg / liter.
The reaction tank has a partition wall that partitions the anaerobic region and the aerobic region, and the partition wall removes wastewater near the water surface of the aerobic region by aeration performed in the aerobic region. It is preferable to have an opening for backflow into the region.
The reaction tank includes a first reaction tank having the anaerobic region, the second reaction tank having the anaerobic region and the aerobic region, and waste water discharged from the anaerobic region of the first reaction tank. Is preferably provided to the oxygen-free region of the second reaction tank.

Hydrogen sulfide and the like generated during the treatment of wastewater and sludge are corrosive gases having a bad odor. In the wastewater treatment system and the treatment method of the present invention, the wastewater treatment facility of the standard activated sludge method is developed as advanced treatment using activated sludge predominated at high concentrations of Bacillus bacteria, and the first sedimentation basin is abolished. The sludge to be concentrated and dewatered is made into one system with only surplus sludge, and waste water containing sludge from raw sludge is decomposed in the reaction tank by activated sludge containing Bacillus bacteria, hydrogen sulfide generated from raw sludge, etc. This eliminates the need to implement symptomatic odor countermeasures in the gas phase, which can reliably extend the life of electrical machinery and equipment, The environment can be improved reliably.

Moreover, in the wastewater treatment system and the treatment method of the present invention, the sludge for raw sludge is not separated in the initial sedimentation basin, but is reduced by being decomposed through the reaction tank while being contained in the wastewater. The amount of sludge generated in the entire system can be reduced by 85 to 90% compared with the conventional system, and 10 to 15% can be reduced.

Furthermore, in the wastewater treatment system and the treatment method of the present invention, since the gravity concentration equipment 104, the mixing tank 106 and their related piping are not required, the equipment arrangement for sludge treatment becomes very simple and compact. It is possible to reduce the running cost including the overall initial cost, maintenance cost, power consumption and disposal cost of dehydrated cake.

FIG. 1A is a configuration diagram schematically showing a first embodiment of a wastewater treatment system according to the present invention, and FIG. 1B is a cross-sectional view taken along line AA showing an example of the wastewater treatment system shown in FIG. 1A. FIG. 1C is a cross-sectional view taken along the line AA showing another example of the wastewater treatment system shown in FIG. 1A. It is a block diagram which shows typically 2nd Embodiment of the wastewater treatment system which concerns on this invention. It is a flowchart which shows one Example of the procedure of the wastewater treatment method which concerns on this invention. It is a block diagram which shows typically the structure of the wastewater treatment system of the conventional standard activated sludge method. FIG. 5 is a configuration diagram in which the configuration of the wastewater treatment system shown in FIG. 4 is partially modified.

The wastewater treatment system and the treatment method according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1A is a configuration diagram schematically showing a first embodiment of a wastewater treatment system according to the present invention. The present invention develops as an advanced treatment using activated sludge predominated at high concentration by Bacillus bacteria in the wastewater treatment facility of the standard activated sludge method, and makes the sludge to be concentrated and dehydrated into one system. This is a wastewater treatment system that reduces the amount of sludge generated, and includes a reaction tank 2, a sedimentation basin 3, a sludge return means, a concentration means 5, a dehydration means 7, and a mineral powder addition means 8.

The reaction tank 2 has an anaerobic region 2b, an oxygen-free region 2c, and an aerobic region 2d, the interior of which is partitioned by the first and

second partition walls

2e and 2f. The reaction tank 2 contains Bacillus bacteria at a concentration of 10 ⁸ to 10 ¹⁰ cells / milliliter in the order of the anaerobic region 2b, the anaerobic region 2c, and the aerobic region 2d, and a concentration of 2600 mg / liter or more and less than 5000 mg / liter. The activated sludge is used to decompose raw sludge contained in the wastewater and to remove nitrogen and phosphorus from the wastewater.

The 1st partition wall 2e partitions between the anaerobic area | region 2b and the anaerobic area | region 2c, and has an opening part connected as a flow path of the waste water which flows from the anaerobic area | region 2b to the anaerobic area | region 2c.
The second partition wall 2f partitions the anoxic region 2c and the aerobic region 2d, and waste water near the water surface of the aerobic region 2d is converted into the anoxic region 2c by aeration performed in the aerobic region 2d. An opening for backflow is provided, and the oxygen-free region 2c and the aerobic region 2d are continuously formed by the opening.
That is, as shown in FIG. 1B, the second partition wall 2f is disposed in an intermediate portion that partitions between the anoxic region 2c and the aerobic region 2d, and a part of the height of the intermediate portion from the upper end of the intermediate portion. It has an opening 2i that extends in the height direction and communicates as a flow path in all width directions. The height of the water surface 2h in the aerobic region 2d rises due to aeration, and the amount of rise varies depending on the degree of aeration.
Further, as shown in FIG. 1C, the second partition wall 2f extends in the width direction from one end in the width direction of the intermediate portion to a part of the width of the intermediate portion, and has an opening 2j extending in all height directions. You may have. The second partition wall 2f having the opening 2j as shown in FIG. 1C is provided on the left side when the opening between the anaerobic region 2b and the oxygen-free region 2c is viewed from above, for example, in order to prevent stagnation of waste water. This is applied when the flow path is meandered on the right side when viewed from above the opening between the oxygen region 2c and the aerobic region 2d.

As described above, generally, solids contained in wastewater are removed by a screen and a sand settling tank based on the size and specific gravity, and the remaining solids having a relatively small size and lower specific gravity than sand ( Hereinafter, waste water containing small size and small specific gravity solids) is first supplied to the settling basin and separated as raw sludge. In the present invention, since the first sedimentation basin has been abolished, waste water that has not passed through the first sedimentation basin, that is, a solid substance having a small size and a low specific gravity contained in the waste water, is introduced into the inlet 2a provided in the anaerobic region 2b. Waste water is supplied as it is without being separated as raw sludge.

Each region of the anaerobic region 2b, the anaerobic region 2c, and the aerobic region 2d is the reaction tank 2 in which the wastewater supplied from the inlet 2a provided in the anaerobic region 2b via the flow path 11 is downstream from the upstream side. Arranged in order of flow to the side. Each region is provided with activated sludge in which the Bacillus bacteria that decompose the wastewater supplied from the inlet 2a predominate at a high concentration, and wastewater containing solid matter of small size and small specific gravity is included in each region. During the stay, the raw sludge (solid matter) is decomposed, denitrified, dephosphorized, and the like.
That is, in the anaerobic region 2b, facultative anaerobic bacteria including Bacillus bacteria reduce the organic substances such as carbohydrates and proteins in the mixed solution to ammonia and the like by enzymes, and use them as biological constituents. Releases phosphorus stored in the body. In the anoxic region 2c, denitrifying bacteria reduce nitrate nitrogen and nitrite nitrogen to nitrogen gas using BOD in the mixed solution as a hydrogen donor.
In the aerobic region 2d, ammonia nitrogen contained in the wastewater is oxidized to nitrite nitrogen and nitrate nitrogen by nitrifying bacteria, and phosphorus is removed from the wastewater by the phosphorus accumulating bacteria re-ingesting phosphorus into the body. .
For this reason, in the anaerobic region 2b / anoxic region 2c, a positive aeration is not performed, and a small amount of stirring is performed using the stirrer 9 for the purpose of preventing starch from forming in the reaction tank 2. The degree of this stirring is such that it does not interfere with the effects of denitrification, dephosphorization, etc. in the wastewater by the action of microorganisms such as Bacillus bacteria in the activated sludge in the anaerobic region 2b and the anaerobic region 2c. On the other hand, aeration is performed via the air diffuser 10 in the aerobic region 2d.
Moreover, in each area | region of the anaerobic area | region 2b, the anaerobic area | region 2c, and the aerobic area | region 2d, Bacillus genus bacteria decompose | disassemble the sulfur compound (hydrogen sulfide, methyl mercaptan, methyl sulfide, methyl disulfide) contained in raw sludge. , Remove bad smell. And the waste water after flowing through the aerobic region 2d is discharged from the outlet 2g provided in the aerobic region 2d in a state including the activated sludge after flowing through the aerobic region 2d.

Since Bacillus bacteria have a very high treatment capacity in the facultative anaerobic part, the residence time of the wastewater in the anaerobic region 2b and the anaerobic region 2c may be longer than the residence time of the wastewater in the aerobic region 2d. preferable. In the present embodiment, the residence times of the wastewater in the anaerobic region 2b, the anaerobic region 2c, and the aerobic region 2d are 1.5 to 2.0 hours, 3.5 to 4.5 hours, and 3.5 to 4 respectively. Adjusted within 5 hours. If each residence time is shorter than this range, the wastewater will not be decomposed sufficiently and the amount of excess sludge will increase, while if it is longer than this range, the wastewater treatment capacity of the entire system will increase due to the longer treatment time. descend. The ratio of the total residence time of the anaerobic region and the anaerobic region to the residence time of the aerobic region is preferably maintained within a range of 1.0 to 2.0. The ratio is more preferably maintained within a range of 1.1 to 1.9. If this ratio is lower than this range, the wastewater will not be decomposed sufficiently and the amount of excess sludge will increase. To do. In particular, when it is outside the above range, the ability to remove nitrogen contained in the wastewater is significantly reduced.
The activated sludge in the reaction tank 2 contains Bacillus bacteria that decompose the wastewater supplied from the inlet 2a at a concentration of 10 ⁸ to 10 ¹⁰ / ml by adjusting the amount of mineral powder to be described later. It is preferable to maintain and manage the state, that is, the state in which Bacillus bacteria are dominant at a high concentration. When the concentration of Bacillus bacteria is lower than this range, the wastewater is not sufficiently decomposed and the amount of excess sludge increases, whereas when it is higher than this range, the amount of mineral powder added is excessively increased. The running cost of the entire system increases more than necessary.

Depending on the nitrogen concentration, phosphorus concentration, etc. in the wastewater to be treated, the anaerobic region 2b confirmed by the ORP meter 32 by adjusting the state of aeration through the air diffuser 10 by control means not shown. It is preferable that the redox potential is −150 to −350 mV, and that the dissolved oxygen amount in the wastewater in the aerobic region 2d confirmed by the DO meter 33 is 2.0 to 3.5 mg / liter. . When the oxidation-reduction potential is lower than this range (below −350 mV), the activity of nitrifying bacteria decreases due to the generation of hydrogen sulfide and the like, and the water quality deteriorates, while when it is high (above −150 mV), Since the anaerobic degree is low, the dephosphorization reaction becomes insufficient and the water quality deteriorates. If the amount of dissolved oxygen is lower than this range, the wastewater will not be decomposed sufficiently and the amount of excess sludge will increase.If the amount of dissolved oxygen is higher than this range, the running cost of the entire system will increase due to an excessive increase in the amount of aeration. Rise more than necessary.

Subsequently, the sedimentation basin 3 is provided on the downstream side of the reaction tank 2, and precipitates and separates activated sludge contained in the treated wastewater discharged from the outlet 2g of the reaction tank 2.

Here, in the wastewater treatment system of this embodiment, the suspended matter (SS) meter 31 for confirming the load on the reaction tank 2 in the flow path 11 to the inlet 2a of the reaction tank 2, and the anaerobic region 2b An oxidation-reduction potential (ORP) meter 32 for confirming the oxidation-reduction potential, a dissolved oxygen (DO) meter 33, an MLSS meter 34, a reaction tank 2 for confirming the amount of dissolved oxygen in the wastewater An automatic phosphorus measuring device 35 is provided in the flow path 13 between the settling basins 3, and a total nitrogen (TN) / total phosphorus (for monitoring nitrogen and phosphorus discharge concentrations are provided in the discharge flow path 14 from the settling basin 3 ( (TP) An automatic measuring device 36 and a chemical oxygen demand (COD) meter 37 for monitoring the chemical oxygen demand discharge concentration are installed, and each is monitored and controlled.

The sludge return means includes a return passage 15 connected between the downstream side of the sedimentation basin 3 and the vicinity of the inlet 2a on the upstream side of the reaction tank 2, a pump (not shown) for conveying the sludge, and the like. Yes. In order to maintain the MLSS concentration of the activated sludge in the reaction tank 2 measured by the MLSS meter 34 within a predetermined range, which will be described later, the sludge returning means uses a pump or the like from the activated sludge separated in the sedimentation basin 3 to a predetermined level. The ratio is returned as the return sludge 42 from the downstream side of the sedimentation basin 3 to the upstream side of the reaction tank 2 via the return flow path 15.

By adjusting the ratio of the return sludge 42 to the activated sludge after separation in the sedimentation basin 3 within the range of 30 to 60%, the activated sludge in the reaction tank 2 is 2600 mg / liter or more and less than 5000 mg / liter MLSS. It is preferably maintained at a concentration. Further, the activated sludge in the reaction tank 2 is more preferably maintained and managed at a MLSS concentration of 3000 mg / liter or more and less than 4000 mg / liter. When the MLSS concentration of activated sludge is lower than this range, the wastewater is not sufficiently decomposed and the amount of surplus sludge increases. On the other hand, when the MLSS concentration is higher than this range, the amount of returned sludge increases excessively. Running costs will rise more than necessary. Moreover, the capacity | capacitance of the sedimentation basin 3 may be insufficient and water quality may deteriorate.

Subsequently, the concentration means 5 and the dewatering means 7 are provided on the downstream side of the settling basin 3, and the residue obtained by returning the returned sludge 42 from the activated sludge after separation in the settling basin 3 is concentrated and dehydrated as excess sludge 43. is there. The surplus sludge 43 supplied to the concentrating means 5 through the flow path 17 is easy to sludge because Bacillus bacteria dominate at a high concentration and hardly perish.

Finally, the mineral powder addition means 8 is provided in the vicinity of the inlet 2a on the upstream side of the reaction tank 2, and waste water supplied into the reaction tank 2 obtained by converting the BOD concentration by measuring with the SS meter 31. Based on the BOD concentration, when the waste water is supplied into the reaction tank 2, the concentration of the Bacillus bacteria in the activated sludge returned from the sedimentation tank 3 and supplied into the reaction tank 2 is within the predetermined range. In order to maintain the above, mineral powder mainly composed of silicic acid is added to the wastewater supplied to the reaction tank 2.
The wastewater treatment system according to the present invention is basically configured as described above.

Next, the wastewater treatment method according to the present invention will be described.
FIG. 3 is a flowchart showing an embodiment of the procedure of the wastewater treatment method according to the present invention. The present invention develops as an advanced treatment using activated sludge predominated at high concentration by Bacillus bacteria in the wastewater treatment facility of the standard activated sludge method, and makes the sludge to be concentrated and dehydrated into one system. This is a wastewater treatment method for reducing the amount of sludge generated, and comprises steps S10 to S28.

First, in step S10, waste water that does not pass through the first sedimentation basin that separates solid sludge having a small size and small specific gravity contained in the waste water as raw sludge, that is, small size and small specific gravity contained in the waste water. Waste water containing solid matter as raw sludge as it is without being separated is supplied from the inlet 2a into the reaction tank 2 through the flow path 11.
In the reaction tank 2, the anaerobic region 2b, the anaerobic region 2c, and the aerobic region 2d are arranged in the order in which the waste water supplied into the reaction vessel 2 flows from the upstream side to the downstream side. 2 is provided with activated sludge in which the Bacillus bacteria that decompose the wastewater supplied in 2 are dominant at a high concentration. In the case of this embodiment, the activated sludge provided in the reaction tank 2 is maintained and managed at a MLSS concentration of 2600 mg / liter or more and less than 5000 mg / liter, and Bacillus bacteria contained in the activated sludge are 10 ⁸ to 10 ¹⁰ cells / ml. Maintained at a concentration of

Next, in step S12, while the wastewater supplied into the anaerobic region 2b in step S10 flows through the anaerobic region 2b including the activated sludge provided in the anaerobic region 2b over 1.5 to 2.0 hours, Bacillus bacteria contained in the activated sludge flowing through the anaerobic region 2b decompose the wastewater flowing through the anaerobic region 2b. Specifically, the Bacillus bacterium in the activated sludge in the reaction tank 2 exhibits an excellent ability to remove sulfur compounds (hydrogen sulfide, methyl mercaptan, methyl sulfide, methyl disulfide) in the waste water. The malodor is simultaneously removed by the waste water treatment. In addition, NH4-N (ammonia nitrogen) is removed to below the lower limit of quantification.
In addition, the Bacillus bacteria in the activated sludge in the reaction tank 2 have a nitrogen removing ability, and in the anaerobic region 2b that is in an oxygen-deficient state due to the absence of aeration, the growth time is faster than other general bacteria. Ammonia nitrogen is used as a biological component. Furthermore, phosphorus accumulated in the body is released in the anaerobic region 2b by the action of phosphorus accumulating bacteria in the activated sludge in the reaction tank 2.

Next, in step S14, in the anaerobic region 2c, the wastewater after flowing in the anaerobic region 2b in step S12 includes the activated sludge after flowing in the anaerobic region 2b, and through the opening of the partition wall 2e, the anoxic region 2c. The Bacillus bacteria contained in the activated sludge flowing through the anaerobic region 2c, while flowing through the anoxic region 2c over 3.5 to 4.5 hours, wastewater flowing through the anoxic region 2c. Decompose. Specifically, Bacillus bacteria remove bad odor by decomposing sulfur compounds in the anoxic region 2c as well. Similarly, Bacillus bacteria also use ammoniacal nitrogen as a biological component even in the anoxic region 2c that is in an oxygen-deficient state due to the absence of aeration.

Next, in step S16, in the aerobic region 2d, the wastewater after flowing in the anoxic region 2c in step S14 includes activated sludge after flowing in the anoxic region 2c and is aerobic through the opening of the partition wall 2f. While being supplied to the region 2d and flowing through the aerobic region 2d over 3.5 to 4.5 hours, Bacillus bacteria contained in the activated sludge flowing through the aerobic region 2d are flowing through the aerobic region 2d. Decompose wastewater. Specifically, the Bacillus bacterium removes malodors by decomposing sulfur compounds in the aerobic region 2d as well. In addition, in the aerobic region 2d where aeration is performed, the action of nitrifying bacteria in activated sludge (oxidizing ammonia to nitrate) is added to the action of Bacillus bacteria described above, and nitrification is promoted and contained in wastewater. Ammonia nitrogen is oxidized to nitrite nitrogen and nitrate nitrogen by nitrifying bacteria. Furthermore, phosphorus is removed from the wastewater by re-ingesting more phosphorus into the body than the phosphorus accumulating bacteria released in the anaerobic region 2b in the aerobic region 2d.

Next, in step S20, the waste water after flowing through the aerobic region 2d is discharged from the outlet 2g of the reaction tank 2 including the activated sludge after flowing through the aerobic region 2d.

As described above, the Bacillus bacteria in the activated sludge in the reaction tank 2 become poorly nourished when treatment proceeds in the reaction tank 2, and spores are formed in the cells. It flows into the settling basin 3. Since the cell wall of the spore of this Bacillus genus is covered with an adhesive substance, it has adsorptivity, facilitates floc formation, and improves aggregation. In addition, as described above, silicic acid in the mineral powder added to the waste water becomes the core of the sludge, so that the specific gravity of the activated sludge increases and the sedimentation property of the sludge increases.

Next, in step S22, the activated sludge contained in the wastewater is precipitated and separated from the wastewater discharged from the reaction tank 2 in step S20 and flowing into the settling basin 3, and discharged to the outside through the flow path 14. . As described above, waste water is treated in the reaction tank 2 and the sedimentation basin 3.

Next, in step S24, as shown by return sludge return "Y" (yes), in order to maintain the MLSS concentration of the activated sludge provided in the reaction tank 2 within the above concentration range, the sludge return means performs step S24. A part of the activated sludge separated in S22 is reacted through the return flow path 15 from the downstream side of the sedimentation basin 3 while adjusting the return ratio of the activated sludge within the range of 30 to 60%. Return to the upstream side of the tank 2.

Next, in step S26, in order to maintain the concentration of Bacillus bacteria in the activated sludge that is returned as the return sludge 42 from the sedimentation basin 3 in step S24 and supplied into the reaction tank 2 within the above-mentioned concentration range, SS While adjusting the amount of mineral powder mainly composed of silicic acid based on the BOD concentration of wastewater supplied into the reaction tank 2 in step S10 obtained by measuring the total 31 and converting the BOD concentration, the reaction This mineral powder is added to the upstream side of the tank 2. The return sludge 42 is provided in the anaerobic region 2b as activated sludge after flowing into the reaction tank 2 from the upstream side of the reaction tank 2. Thereafter, the process returns to step S12 and executed.

On the other hand, as shown by the return “N” (No) of the returned sludge in Step S24, the remaining activated sludge that has returned the returned sludge is supplied to the concentrating means 5 through the flow path 17 in Step S28, and this residual The concentrated sludge is concentrated and dehydrated as excess sludge 43 by the concentration means 5 and the dewatering means 7.
The wastewater treatment method according to the present invention basically includes the steps as described above.

In the wastewater treatment system of this embodiment, the raw sludge is eliminated by eliminating the first sedimentation basin, and the sludge to be concentrated and dewatered is only one system of surplus sludge separated in the final sedimentation basin. As a result, the sludge for raw sludge is not separated in the first sedimentation basin, but is decomposed and reduced through the reaction tank while contained in the wastewater, so that the excess sludge for raw sludge can be reduced. The amount of sludge generated in the entire system can be reduced.

In addition, by eliminating the first sedimentation basin as described above and making the sludge to be concentrated and dehydrated into only one system of surplus sludge, by decomposing the wastewater using the activated sludge in which Bacillus bacteria predominated at a high concentration, Corrosive gas having bad odor such as hydrogen sulfide generated from raw sludge can be removed. Therefore, it is not necessary to implement symptomatic odor countermeasures in the gas phase, and it is possible to reliably extend the life of electric machinery and the like, and to improve the working environment with certainty.

In addition, since sludge from raw sludge is not separated in the initial sedimentation basin, it is reduced by being decomposed through the reaction tank while contained in the wastewater. 90% can be reduced by 10 to 15%.

Furthermore, compared to conventional wastewater treatment systems, the equipment for sludge treatment is very simple and compact as a result of eliminating the need for gravity concentration equipment, mixing tanks and related piping. Therefore, the running cost including the initial cost of the entire system, the maintenance cost, the amount of power used, the disposal cost of the dehydrated cake, etc. can be greatly reduced.

Next, a wastewater treatment system according to a second embodiment of the present invention will be described.
FIG. 2 is a configuration diagram schematically showing a second embodiment of the wastewater treatment system according to the present invention, and the present invention is applied to an existing wastewater treatment system in which the standard activated sludge method is adopted. Embodiment. The reaction tank shown in FIG. 2 includes a first reaction tank 21 modified from the first sedimentation tank in the standard activated sludge method, a second reaction tank 22 modified from the reaction tank in the standard activated sludge method, And the flow path 12 between them. The first reaction tank 21 is on the upstream side where the waste water supplied from the inflow port 2a flows, and an anaerobic region 2b is provided therein. The second reaction tank 22 is provided on the downstream side of the first reaction tank 21, and an oxygen-free region 2c and an aerobic region 2d are provided in the upstream half and the downstream half, respectively. That is, the first reaction tank 21 and the second reaction tank 22 are separated as separate tanks, and the second partition wall is provided between the anoxic region 2c and the aerobic region 2d in the second reaction tank 22. It is partitioned by 2f. Other parts are the same as those of the wastewater treatment system according to the first embodiment of the present invention shown in FIG. 1A.

As described above, the residence time of the anaerobic region 2b, the anaerobic region 2c, and the aerobic region 2d is 1.5 to 2.0 hours, 3.5 to 4.5 hours, and 3.5 to 4.5 hours. However, the volume ratio of the first sedimentation basin to the reaction tank of the existing wastewater treatment system that uses the standard activated sludge method is about 1: 4 to 5, so the first sedimentation basin is anaerobic region 2b and there is no reaction tank. It can be used as the oxygen region 2c and the aerobic region 2d. Moreover, since the residence time of the anaerobic region 2c and the aerobic region 2d is substantially the same, the respective volumes are also substantially the same.

The operation of the wastewater treatment system of the second embodiment is that wastewater treated in the first reaction tank 21 is discharged from the first reaction tank 21 and supplied to the second reaction tank 22 through the flow path 12. Except for this point, it is the same as the wastewater treatment system of the first embodiment.
In the wastewater treatment system of the second embodiment, the present invention is applied to an existing wastewater treatment system in which the standard activated sludge method is adopted. In addition to the effects of the wastewater treatment system of the first embodiment, In addition, there is a merit that the cost can be reduced by making effective use of existing facilities.

The wastewater treatment system and the treatment method according to the present invention have been described in detail with reference to the embodiments and examples. However, the present invention is not limited to the above-described embodiments and examples, and does not depart from the gist of the present invention. Of course, various improvements and changes may be made.

The wastewater treatment system and the treatment method of the present invention eliminate the need to implement symptomatic odor countermeasures in the gas phase, and can reliably prolong the life of electrical machinery and equipment, while ensuring the working environment. In addition, the amount of sludge generated in the entire system can be reduced by 85 to 90% compared to the conventional system, and 10 to 15% can be reduced. In addition, the initial cost, maintenance cost, and power consumption of the entire system can be reduced. The running cost including the amount and the disposal cost of the dehydrated cake can be reduced, which is industrially useful.

2, 21, 22 Reaction tank 2a Inlet 2b Anaerobic region 2c Anaerobic region 2d

Aerobic region

2e, 2f Partition wall 2g Outlet

2h Water surface

2i, 2j Opening 3 Sedimentation basin 5 Concentrating means 7 Dehydrating means 8 Mineral powder addition Means 9 Stirrer 10

Air diffuser

11, 12, 13, 14, 17 Flow path 15 Return flow path 31 SS meter 32 ORP meter 33 DO meter 34 MLSS meter 35 Phosphorus automatic measuring device 36 TN / TP automatic measuring device 37 COD meter 42 Return sludge 43 Surplus sludge 101 Initial sedimentation tank 102 Reaction tank 103 Final sedimentation tank 104 Gravity concentration equipment 105 Mechanical concentration equipment 106 Mixing tank 107

Dehydration equipment

111, 112, 113, 114, 115, 115a, 115b, 116, 117 Channel 141 Raw sludge 142 Return sludge 143 Excess sludge 144 Mixed sludge

Claims

An anaerobic region, an anaerobic region, and an aerobic region, and containing, in the order of the anaerobic region, the anaerobic region, and the aerobic region, a Bacillus bacterium having a first concentration of 10 8 to 10 10 cells / ml. Using a second concentration activated sludge of liters or more and less than 5000 mg / liter, decomposing raw sludge contained in wastewater, and performing a treatment for removing nitrogen and phosphorus from the wastewater;
A sedimentation basin for precipitating and separating activated sludge contained in the treated wastewater discharged from the reaction tank;
In order to maintain the activated sludge in the reaction tank at the second concentration, sludge return means for returning a predetermined ratio from the activated sludge separated in the sedimentation basin to the reaction tank as return sludge;
A concentration dewatering means for concentrating and dewatering the residue of the activated sludge separated in the sedimentation basin as surplus sludge;
In order to maintain the Bacillus bacteria in the activated sludge returned from the sedimentation basin at the first concentration, a mineral powder mainly composed of silicic acid is used based on the concentration of wastewater supplied into the reaction tank. And a mineral powder adding means for adding to the wastewater supplied to the reaction tank.
2. The sludge return means maintains the activated sludge in the reaction tank at a concentration of 3000 mg / liter or more and less than 4000 mg / liter by returning the return sludge to the reaction tank. Wastewater treatment system.
The wastewater treatment system according to claim 1 or 2, wherein the sludge return means adjusts the ratio of return sludge to the activated sludge separated in the sedimentation basin within a range of 30 to 60%.
The residence time of waste water in the anaerobic region, the anaerobic region, and the aerobic region is 1.5 to 2.0 hours, 3.5 to 4.5 hours, and 3.5 to 4.5 hours, respectively. Item 4. A wastewater treatment system according to any one of Items 1 to 3.
5. The control device according to claim 1, further comprising control means for maintaining an oxidation-reduction potential in the anaerobic region at −150 to −350 mV, and an amount of dissolved oxygen in wastewater in the aerobic region at 2.0 to 3.5 mg / liter. The wastewater treatment system according to any one of the above.
The reaction tank has a partition wall that partitions the anoxic region and the aerobic region,
The wastewater treatment according to any one of claims 1 to 5, wherein the partition wall has an opening for causing the wastewater near the water surface of the aerobic region to flow back to the anoxic region by aeration performed in the aerobic region. system.
The reaction tank includes a first reaction tank having the anaerobic region, the second reaction tank having the anaerobic region and the aerobic region, and waste water discharged from the anaerobic region of the first reaction tank. The wastewater treatment system according to any one of claims 1 to 6, further comprising: a flow path for supplying the gas to an oxygen-free region of the second reaction tank.
A reaction tank having an anaerobic region, an anaerobic region, and an aerobic region, containing 10 8 to 10 10 cells / ml of a first concentration of Bacillus bacteria in the order of the anaerobic region, the anaerobic region, and the aerobic region; Using the activated sludge having a second concentration of 2600 mg / liter or more and less than 5000 mg / liter, the raw sludge contained in the wastewater is decomposed and nitrogen and phosphorus are removed from the wastewater.
By the sedimentation basin, the activated sludge contained in the treated wastewater discharged from the reaction tank is precipitated and separated,
In order to maintain the activated sludge in the reaction tank at the second concentration, the sludge returning means returns a predetermined ratio from the activated sludge separated in the sedimentation basin to the reaction tank as a return sludge,
Concentrated and dehydrated means to concentrate and dehydrate the remainder of the activated sludge separated in the sedimentation basin as excess sludge,
In order to maintain the Bacillus bacteria in the activated sludge returned from the sedimentation basin at the first concentration, silicic acid is added based on the concentration of waste water supplied into the reaction tank by the mineral powder addition means. A wastewater treatment method comprising adding a mineral powder as a main component to wastewater supplied to the reaction tank.