KR101233545B1 - Method of biologically treating organic waste water - Google Patents

Abstract

The present invention provides a biological treatment method for organic wastewater, which can stably obtain a sludge reduction effect due to the predatory action of microorganisms, and can obtain treated water of good quality. Organic wastewater is introduced into the aeration tank and biotreated at high load to produce dispersible bacteria. The biological treatment liquid flowing out of the aeration tank containing the dispersible bacteria is introduced into the microorganism holding tank. By controlling the DO concentration of the aeration tank or by operating the soluble BOD sludge load of the microorganism holding tank at 0.025kg-BOD / kg-VSS / day or more and 0.05kg-BOD / kg-VSS / day or less, Microorganisms are reproduced to reduce the amount of surplus sludge generated by the predatory action of microorganisms, and produce sludge flocs excellent in sedimentation properties.

Description

Biological treatment method of organic wastewater {METHOD OF BIOLOGICALLY TREATING ORGANIC WASTE WATER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for biological treatment of organic wastewater treating organic wastewater with activated sludge and the like, and more particularly, to a method for biological treatment of organic wastewater for biologically reducing surplus sludge generated by biotreatment of organic wastewater. will be.

Among the biological treatment methods for biological treatment of organic wastewater containing organic substances, the active sludge method has the advantage of being able to obtain a good quality treated water and easy management, and is widely used as a treatment method for various organic wastewater such as sewage and industrial wastewater. It is used. However, the volume load of BOD (organic matter expressed in biochemical oxygen consumption) for the biological treatment tank which performs active sludge treatment is low as 0.5-0.8 kg / m <^3> / day. Accordingly, in order to cope with high loads, there is a problem that the aeration tank must be large and a large installation area is required.

On the other hand, the fluidized bed method is known as a biological treatment method capable of high load operation. The fluidized bed method increases the sludge concentration maintained in the aeration tank by adding a carrier to the aeration tank to perform biotreatment, so that a high load operation of a BOD volume load of 3 kg / m ³ / day or more is possible.

By the way, when the wastewater is biotreated, most of the BOD magnetized to the bacteria is used as the respiratory substrate of the bacteria and decomposed into carbon dioxide and water, but some are used for the growth of the bacteria. For example, in the activated sludge method, about 20 to 40% of the BOD injected into bacteria is used for cell synthesis. Thus, about 20 to 40% of the activated sludge treated BOD is converted into bacteria, and bacteria that have propagated BOD as a substrate have a problem of being discharged as excess sludge. In particular, the fluidized bed method produces more excess sludge than the conventional activated sludge method, specifically, about 30-40% of the surplus sludge of biodegraded BOD is generated.

Therefore, in the second stage of the first stage biological treatment tank (hereinafter may be referred to as "aeration tank" in particular), the second stage biological treatment tank (hereinafter, specifically referred to as "microbial maintenance tank") holding fixed protozoa There is known an organic wastewater biological treatment method for installing (for example, Patent Document 1). In the method disclosed in Patent Literature 1, by placing a high BOD load on the first stage biological treatment tank, proliferation of protozoa is prevented to prevent the aggregation of bacteria, and biological treatment flowing out of the first stage biological treatment tank including dispersible bacteria. The liquid is introduced into a second stage biological treatment tank. In the second stage biological treatment tank, the protozoa that preys dispersible bacteria is retained, so that the disperse bacteria are fed to the protozoa, so that surplus sludge is reduced, and at the same time, flocking of the biological population proceeds. As a result, in the second monobial treatment tank, microbial aggregates (sludge flocs) having good sedimentation properties are formed, and clear and clean treatment water can be obtained by solid-liquid separation of the effluent from the second monobial treatment tank.

Thus, by combining the first monobial treatment tank operated at high load and the second monobial treatment tank holding fixed protozoa, high load operation and reduction of surplus sludge can be achieved, and clear and clean treatment water can be obtained. . Accordingly, various kinds of improvement methods have been proposed for the biological treatment method using the first single biological treatment tank and the second single biological treatment tank. For example, Patent Literature 2 discloses a biological treatment device in which a food refining tank is provided between a first stage biological treatment tank and a second stage biological treatment tank. In the apparatus disclosed in Patent Document 2, ultrasonication or the like is carried out in a feed micronization tank to disperse the flocked bacteria to promote bacterial predation by protozoa maintained in a second stage biological treatment tank at a later stage.

Moreover, the method of reducing excess sludge by combining the fluidized bed method and the activated sludge method is proposed (patent document 3). In the method disclosed in Patent Literature 3, the biological treatment is performed by the fluidized bed method in the front-side aeration tank, and then the BOD sludge load is 0.1-0.6 kg-BOD / kg-VSS / day in the rear-side biological treatment tank. Perform the process. By adding a carrier to the biological treatment tank on the front side, this method enables high load treatment, while lowering the BOD sludge load in the rear biological treatment tank to promote self-extinguishing of activated sludge and to reduce the amount of excess sludge generated. .

Patent Document 1: Japanese Patent Laid-Open No. 55-20649

Patent Document 2: Japanese Patent Laid-Open No. 57-74082

Patent Document 3: Japanese Patent No. 3410699

Problem to be solved by invention

In the method described in Patent Literature 3, although sludge is reduced using self-extinguishing of activated sludge, lowering the load of soluble BOD sludge to promote self-extinguishing of activated sludge lowers sedimentation of sludge and deteriorates treated water quality. There is a problem.

On the other hand, in the method disclosed by patent document 1 and patent document 2, sludge is reduced using the phagocytosis of the bacteria by the microorganism of the filtration predation type which inhales and preys on a bacterium. In this method, it is possible to prevent deterioration of sedimentation of sludge because it is possible to accelerate sludge reduction and microbial flocculation due to the predation action of microorganisms in the second monobial treatment tank that saponifies sludge. Can be.

However, in the method disclosed by patent document 1 and patent document 2, it is difficult to adjust the processing conditions in a 1st single biological treatment tank and a 2nd single biological treatment tank. In particular, when the treatment conditions in the first biological treatment tank are not controlled to an appropriate range, not only the sludge reduction effect can be obtained but also the deterioration of the treated water quality may be caused. For example, the biomass maintained in the second stage biological treatment tank depends on the removal rate of soluble BOD in the first stage biological treatment tank, and depending on the treatment conditions in the first stage biological treatment tank, Sometimes microorganisms cannot be maintained. Alternatively, when bacteria are larger than the diameter of microorganisms, predation by microorganisms does not proceed, and the effect of sludge reduction may be lowered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a biological treatment method for organic wastewater which can obtain treated water of good quality, and furthermore, stably obtains a sludge reduction effect due to the predation action of microorganisms. There is a purpose.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM The present inventors can proliferate dispersible bacteria in an aeration tank by controlling the aeration tank dissolved oxygen (DO) density | concentration of a high load processing process, and the food required in order to hold | maintain a predetermined amount of microorganisms in a microorganism holding tank stably is stable. Provide what can be supplied. In addition, the present inventors control the solubility BOD sludge load of the microorganism holding tank to be within a certain range, and provide that the microorganism holding tank easily maintains a predetermined amount of microorganisms.

The present invention has been completed based on the above-described contents, and the biological treatment tank is divided into plural stages, the DO concentration of the biological treatment tank (aeration tank) on the front side is controlled, or the biological treatment tank (microbial maintenance tank) on the rear end side. By controlling the solubility BOD sludge load of), microorganisms are stably propagated in the microorganism holding tank to reduce excess sludge. More specifically, the present invention provides the following.

(1) a high load treatment step of introducing organic wastewater containing organic matter into an aeration tank and biotreating under aerobic conditions, and a low load treatment step of introducing and treating a biological treatment liquid flowing out of the high load treatment step into a microbial holding tank for biotreatment. And one or both of the dissolved oxygen concentration of the aeration tank of the high load treatment step, and the soluble BOD sludge load to the microbial holding tank of the low load treatment step to control the organic matter in the high load treatment step. A biotreatment method for organic wastewater, in which dispersible bacteria are produced by a substrate, and the dispersible bacteria are fed by the microorganisms reproduced in the microorganism holding tank in the low load treatment step.

(2) In (1), in the low load treatment step, the soluble BOD sludge load on the microorganism holding tank is 0.025 kg-BOD / kg-VSS / day or more and 0.05 kg-BOD / kg-VSS / day or less. The organic wastewater biological treatment method described.

(3) The organic wastewater biological treatment method according to (1) or (2), wherein in the high load treatment step, the dissolved oxygen concentration of the aeration tank is biotreated at 0.5 mg / L or less.

(4) In the high load treatment step, the amount of CODcr to be decomposed in the high load treatment step is obtained by measuring the inflow amount of the organic wastewater to the aeration tank and the concentration of the organic matter contained in the organic wastewater, and the amount of CODcr to be decomposed. The organic wastewater biological treatment method in any one of (1)-(3) which controls the oxygen supply amount based on the above.

(5) In the high load treatment step, the organic wastewater according to any one of (1) to (4), which creates an oxygen depletion period in which the dissolved oxygen concentration of the crude liquid in the aeration tank becomes 0 mg / L by controlling the oxygen supply amount. Biological treatment method.

(6) In the high load treatment step, the oxygen supply amount is controlled such that the ratio of the oxygen depletion period to the aerobic period in which the dissolved oxygen concentration of the crude liquid in the aeration tank exceeds 0 mg / L is 0.25 or more and 1 or less (5) The biological treatment method of the organic wastewater of description.

(7) The biological treatment method for organic wastewater according to any one of (1) to (6), wherein the oxygen supply amount is controlled so that the difference between the oxygen consumption rate and the oxygen supply rate is 10% or less in the high load treatment step.

(8) The biological treatment method for organic wastewater according to any one of (1) to (7), wherein the microorganism is reproduced at a concentration of 5% or more of sludge MLVSS in the microorganism holding tank.

(9) The biological treatment method for organic wastewater according to any one of (1) to (8), wherein the organic wastewater bypassed by the aeration tank is introduced directly into the microbial holding tank.

In the present invention, the effluent (biological treatment liquid) treated in the aeration tank and flowing out in the high load treatment step includes bacteria which have grown organic substances contained in the organic wastewater as substrates. In the present invention, the biological treatment liquid is introduced into the microorganism holding tank, and the amount of sludge generation is reduced by bacterial predation and microdigestion of the microorganisms. For this reason, the microorganism holding tank is operated under conditions suitable to hold a predetermined amount of microorganisms and to aggregate bacteria.

In order to hold a predetermined amount of microorganisms in the microbial holding tank, either the DO concentration of the aeration tank, which is a front-side biological treatment tank operated at high load, and the soluble BOD load of the microbial holding tank, which is a rear-end biological treatment tank operated at low load, or Control both.

In the case of controlling the DO concentration of the aeration tank, the DO concentration is controlled so that the dispersible bacteria dominate. The DO concentration of the tank liquid in the aeration tank can be controlled by adjusting the amount of oxygen supplied to the aeration tank. As a control method of the oxygen supply amount for predominantly dispersible bacteria in the aeration tank, a DO system is provided in the aeration tank, and the DO system value is 0.5 mg / L or less, preferably 0.1 mg / L or less, more preferably 0.05 The method of adjusting oxygen supply amount so that it may become mg / L or less is mentioned.

In addition, since the oxygen supplied to the aeration tank is mainly used for consumption of organic matters and consumed, the oxygen supply amount supplied to the aeration tank can be set by measuring the inflow amount and the organic matter concentration of the organic wastewater flowing into the aeration tank. That is, by calculating the inflow amount of organic wastewater and the concentration of organic matter, the organic matter supplied to the aeration tank is obtained, and the amount of CODcr (organic matter expressed in chemical oxygen consumption) introduced into the aeration tank can be grasped. In the aeration tank, 70-90% of the soluble CODcr is mainly converted to dispersible bacteria. Therefore, the CODcr fraction of the cells when 70-90% of the soluble CODcr contained in the raw water (organic wastewater) flowing into the aeration tank is converted into cells. By supplying oxygen to the aeration tank in the amount necessary to oxidatively decompose CODcr, the dispersing bacteria that maintain DO concentration in the aeration tank below 0.5 mg / L can be predominant. In other words, if the yield of the cells and the degradability of the soluble CODcr of the target wastewater are obtained in advance, the optimum amount of oxygen supplied to the aeration tank can be known even if the organic matter concentration of the organic wastewater in the raw water changes. In addition, although the organic substance concentration contained in organic wastewater can be calculated | required by CODcr, what is calculated | required by BOD or total organic substance amount (TOC) is not excluded.

Alternatively, a period (oxygen deficiency period) in which the DO concentration in the crude liquid of the aeration tank is substantially zero may be provided by temporarily stopping the oxygen supply. By establishing an oxygen deprivation period, it is possible to control the reproduction of bacteria that are more than 5 μm in length and difficult to feed on microorganisms. The oxygen deprivation period can be set by means such as intermittently supplying oxygen to the aeration tank (intermittent aeration) or temporarily reducing the oxygen supply amount. In particular, when the organic matter concentration of the organic wastewater is large (for example, when the variation range is 50 to 150% or more), it is difficult to maintain the DO at a constant value. It is desirable to control the growth of bacteria that do not feed well.

The oxygen deprivation period is preferably set to be 0.25 to 1 times the period of the aerobic period in which the aeration tank is in aerobic conditions (the period during which the DO concentration exceeds 0 mg / L). It is preferable to set it as 1-60 minutes, and it is preferable to set it as 2 minutes or less especially for an oxygen deficiency period. The oxygen deficiency period and the aerobic period are preferably set alternately at intervals of several minutes, for example, at intervals of about 2 to 10 minutes. However, the time interval of 30 minutes or 1 hour is not excluded.

In order to more precisely control the DO concentration, it is preferable to control the oxygen supply amount so that the difference between the oxygen consumption rate and the oxygen supply rate in the aeration tank is 10% or less, preferably 5% or less. The oxygen consumption rate can be calculated by temporarily supplying oxygen temporarily so that the concentration of the DO liquid in the aeration tank becomes 2 mg / L or more, and then temporarily stopping or reducing the oxygen supply amount. That is, the rate of oxygen consumption can be calculated by determining the rate of decrease of the DO concentration at the time of excess oxygen supply and at the time of suppressing oxygen supply. Since the oxygen consumption rate changes depending on the characteristics of organic wastewater, changes in treatment conditions, and the like, it is preferable to calculate the oxygen consumption rate at least once per hour, specifically at an interval of 20 to 40 minutes.

On the other hand, the reason for controlling the soluble BOD sludge load of the microorganism holding tank is as follows. When a large amount of organic matter is supplied to the microorganism holding tank, bacteria that grow as organic substrates multiply in a form that avoids predation by microorganisms, so that a sufficient sludge reduction effect is not obtained. It may also cause a bulking phenomenon. In addition, the microorganisms which dismantle the floc increase, and the quality of the treated water may deteriorate. On the other hand, if the amount of organic matter supplied to the microorganism holding tank is insufficient, the microorganism is not maintained in the microorganism holding tank in a predetermined amount, and the sludge reduction effect is not only lowered, but the sludge is made fine by the self-digestion of bacteria. As a result of deterioration, there is a fear that deterioration of the treated water quality.

In order to prevent this problem, the present invention controls the load of soluble BOD sludge for the microorganism holding tank holding microorganisms, in particular, 0.05kg-BOD / kg-VSS / day or less, in particular, 0.025kg ~ 0.05kg- Control in the range of BOD / kg-VSS / day. In the present invention, while controlling the load of the soluble BOD sludge of the microorganism holding tank, the DO concentration of the aeration tank can be controlled as described above.

In addition, as a biological treatment method of the microbial holding tank, an active sludge method for returning the separated sludge by installing a solid-liquid separation device such as a sedimentation basin at the rear end of the microbial holding tank, and a membrane-separated active sludge for installing a separation membrane in the microbial holding tank. Law and the like. In addition, a carrier suitable for holding microorganisms and bacteria may be added to the microorganism holding tank. Various kinds of fluid fillers can be used as the carrier, and the material and the shape thereof are not particularly limited. The filling rate of the carrier is preferably about 10 to 50% by volume volume per tank.

Further, since microorganisms have a slower growth rate than bacteria, it is preferable that the microorganism holding tank has an SRT (average residence time of sludge) of 10 days or more. However, if the SRT is made too long, the microorganisms are excessively retained in the microorganism holding tank, and the secretions of the microorganisms are also accumulated. Therefore, the SRT should be 40 days or less, particularly 10 days or more and 30 days or less. In addition, SRT can be obtained by Equation 1.

(Equation 1)

 SRT (day) = amount of sludge in the tank ÷ amount of sludge removed

 Here, the amount of sludge in a tank is an existing quantity of microorganisms (sludge) in a biological treatment tank, and can be calculated | required by Formula (2). In addition, the amount of sludge taken out is the quantity of microorganisms (sludge) discharged | emitted from the biological treatment tank, and can be calculated | required by Formula (3).

(Equation 2)

Sludge Volume in Tank = Insoluble Solids (SS) Concentration (mg / L) × Crude Volume (L)

(Formula 3)

Sludge removed = Insoluble solids (SS) concentration (mg / L) × Sludge removed (L / day)

In addition, in order to reproduce a predetermined amount of microorganisms in the microorganism holding tank, dispersing bacteria of at least 0.1% by weight, particularly about 5 to 20% by weight, of the amount of COD of the solids contained in the biological treatment liquid are added to the microorganism holding tank. It is desirable to carry in. In addition, a substance that is a nutrient for microorganisms may be added to the microorganism holding tank. As the nutrient, a substance containing lipids is particularly preferable. Examples of the lipid include phospholipids, free fatty acids, and sterols. Especially, phospholipids such as lysophospholipid and lecithin may be used. The containing material can be used suitably. Specifically, rice bran, beer forge, oil forge, beet forge, shell powder, eggshell, vegetable extract, fish meat extract, various amino acids, various vitamins, etc. can be used as a nutrient. The amount of addition is preferably 0.01 mg / L / day or more, particularly 0.1-10 mg / L / day, per crude volume.

In microbial maintenance baths, microorganisms are preferably grown at a concentration of at least 5% of MLVSS. In addition, in this specification, "microorganism" shall refer to the aquatic protozoan and the welfare animal which preys on a bacterium, and a protozoan includes a strawworm and a bellworm, and a worm and a nematode as a welfare animal. As the microorganisms, it is particularly desirable to predominate microorganisms exhibiting the feeding behavior of the filtered predation type, and specifically, to control the soluble BOD sludge load on the microorganism holding tank as described above. . In addition, MLVSS (Mixed Liquer Volatile Suspended Solid) means sludge (organic) concentration which burns at 600 degreeC.

Effects of the Invention

According to the present invention, by controlling the DO concentration of the aeration tank, it is possible to stabilize the amount of the microorganisms maintained in the microorganism holding tank by predominantly dispersing the dispersible bacteria which are easily predated by microorganisms such as filtration predators. have. In the present invention, the amount of microorganisms in the microorganism holding tank which contributes to sludge reduction is reduced by lowering the soluble BOD sludge load on the microorganism holding tank which maintains microorganisms such as protozoa and the like while performing biotreatment at high load in the aeration tank. It can stabilize. For this reason, according to this invention, the generation amount of surplus sludge can be reduced stably and the treated water with low SS concentration can be obtained.

1 is a schematic diagram of a biological treatment apparatus according to a first embodiment for carrying out the present invention.

2 is a schematic diagram of a biological treatment apparatus according to a second embodiment for carrying out the present invention.

3 is a schematic diagram of a biological treatment apparatus according to a third embodiment of the present invention.

4 is a schematic diagram of a biological treatment apparatus according to a fourth embodiment for practicing the present invention.

5 is a schematic view of a biological treatment apparatus according to a fifth embodiment of the present invention.

Fig. 6 is a diagram showing a control pattern of the oxygen supply amount in the third embodiment.

7 is a diagram showing the result of Reference Example 7. FIG.

Carrying out the invention  Preferred form for

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are given to the same members, and description thereof is omitted or simplified. 1 is a schematic diagram of a biological treatment apparatus (hereinafter simply referred to as a "treatment apparatus") 11 of organic wastewater used for practicing the present invention. The treatment apparatus 11 includes an aeration tank 21, a microbial holding tank 31, and a sedimentation basin 41 for solid-liquid separation means. The sludge treatment tank 51 which bioprocesses the separated sludge floc is further provided.

The aeration tank 21 and the microbial holding tank 31 are connected in series to each other by the first connecting pipe 35, and the microbial holding tank 31 and the settling basin 41 are connected to each other in series by the second connecting pipe 45. In addition, the settling basin 41 and the microbial holding tank 31 are connected to the sludge conveying path 65, and a part of the sludge separated from the settling basin 41 is conveyed to the microbial holding tank 31 as the returning sludge. It is. From the sludge conveying path 65, the sludge discharge path 56 and the treated sludge furnace 57 are branched, and a part of sludge separated from the settling basin 41 is treated by the sludge treatment tank 51. ) Is further reduced, and the surplus is discharged out of the system from the sludge discharge path (56).

In such a treatment apparatus 11, first, organic wastewater such as sewage and industrial wastewater is introduced into the aeration tank 21 from the raw water passage 25 as the water to be treated. In the aeration tank 21, the organic wastewater is mixed with the activated sludge maintained in the tank, and a high load treatment step of biodegrading organic matter contained in the organic wastewater is performed. In the aeration tank 21, the biological treatment is performed while controlling the oxygen supply amount from the gas supply means (in this embodiment, the diffuser) 22 so that the DO concentration of the inner liquid is within a predetermined range, and thus dispersibility is achieved. Dominate bacteria. The control of the oxygen supply amount is as described above, but it is preferable that the concentration of DO in the crude liquid measured by the DO system 23 is 0.5 mg / L or less.

The aeration tank 21 controls the oxygen supply amount, and makes the ratio of the isolate | separable bacteria with respect to a microbial cell 50% or more, especially 80-100%. In order to predominantly disperse bacteria in the aeration tank 21 that are susceptible to predation by the filtered predatory microorganisms, the DO concentration of the aeration tank 21 is adjusted, and the HRT (hydraulic residence time) of the aeration tank 21 is adjusted. It is desirable to set it short. Specifically, the optimum value is HRT capable of removing about 70 to 90% of the soluble organics contained in the organic wastewater introduced into the aeration tank 21, and the HRT is within 0.75 to 1.5 times the optimum value. It is desirable to control. Since the optimum value of HRT depends on the type of organic wastewater, etc., it is good to obtain the optimal value of HRT in advance by a desk test. In general, the HRT of the aeration tank 21 is preferably set to 24 hours or less, and particularly preferably 2 to 8 hours.

As a method of maintaining the HRT within a predetermined range, when the amount of organic wastewater flowing into the aeration tank 21 decreases, the treated water is returned to the aeration tank so that the amount of water entering the aeration tank 21 is constant, or the aeration tank 21 The method of changing the water level of the aeration tank 21 according to the fluctuation | variation of the wastewater inflow into (), etc. are mentioned. In addition, HRT represents the time until the to-be-processed water flows into and flows out into a biological treatment tank (aeration tank 21), and volume L of the biological treatment tank (aeration tank 21) is treated water (organic wastewater). It can be found by dividing by the flow rate (L / hour).

In addition, in the aeration tank 21, biological treatment (high load treatment) as a high organic load is performed compared with the biological treatment (low load treatment) in the microorganism holding tank 31, specifically, 1 kg of soluble BOD volume load. It is good to operate at a high load of -BOD / m ³ / day or more, preferably 3 kg-BOD / m ³ / day or more and 20kg-BOD / m ³ / day or less. When the BOD volume load is increased, the dispersible bacteria tend to dominate by preventing the flocking of bacteria and the predominance of filamentous bacteria, so that the volume of the aeration tank 21 can be reduced.

As the biological treatment system in the aeration tank 21, any method such as floating type or fluidized bed type can be adopted. The aeration tank 21 may be divided into two or more stages and may be multistage, or may introduce sludge conveyed from the microbial holding tank 31 behind the aeration tank 21. In addition, a carrier may be added to the aeration tank 21.

Various kinds of fluid fillers can be used as the carrier, and the material is not particularly limited. Specific examples of the carrier material include inorganic materials such as ash, sand, activated carbon and ceramics, and organic materials such as synthetic resins and cellulose (including a dielectric of cellulose). Synthetic resins include polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, and the like, and foams obtained by appropriately mixing a foaming agent with such foams can be suitably used because of their porosity with a network structure. It is also possible to use a carrier made of a gelled substance.

The shape of the carrier is also not limited, and particle shapes, tubular shapes, honeycomb shapes, yarn shapes, waveforms, and the like can be exemplified, and the shape of the carrier particles in the form of particles can include spheres, pellets, spheres, and the like. There is this. The size of the carrier may be about 0.1 to 10mm. In order to promote the production of dispersible bacteria, the filling rate of the carrier is preferably smaller than usual. Specifically, the filling rate of the carrier is preferably 10% or less, in particular 5% or less, by volume per aeration tank 21.

In the aeration tank 21, 70% or more, preferably 80% or more, more preferably 90% or more of the soluble BOD contained in the organic wastewater is decomposed, and the pH is preferably 6 or more and 8 or less. However, when treating organic wastewater containing a lot of oil (eg 100 mg / L or more), the pH may be higher than 8.

In the aeration tank 21, a high load treatment step of biodegrading most of the soluble BOD contained in the organic wastewater introduced as treated water (for example, 70% or more) is performed. Since the aeration tank 21 is operated by adjusting the DO concentration by controlling the oxygen supply amount, dispersible bacteria predominantly, and a suspension (biotreatment liquid) containing non-aggregated bacteria flows out of the aeration tank 21. The biological treatment liquid is introduced into the microorganism holding tank 31 through the first connecting pipe 35.

In the microbial holding tank 31, a low load treatment step of supplying an oxygen-containing gas from the gas supply means 32 and biotreating under aerobic conditions is performed. The pH of the crude liquid in the microorganism holding tank 31 is preferably about 4-8. The microbial holding tank 31 reduces sludge generation by microbial predation and microbial self-digestion, and promotes flocculation of dispersible bacteria. For this reason, the microorganism holding tank 31 may be operated under conditions suitable for holding a predetermined amount of microorganisms and for aggregating bacteria.

In particular, in the present invention, by supplying the biological treatment solution containing the dispersible bacteria predominant in the aeration tank 21, microorganisms in the microorganism holding tank 31 can be reproduced at a concentration of 5% or more of MLVSS.

The microbial holding tank 31 has a soluble BOD sludge load on the microbial holding tank 31 of 0.05 kg-BOD / kg-VSS / day or less, in particular 0.025 to 0.05 kg-BOD / kg-VSS / day. It is preferable to drive with. This is to prevent the growth of microorganisms in the form of a thread or the like that are difficult to be predated on the microorganisms in the microorganism holding tank 31, and to predominantly reproduce the microorganisms of the filtration predation type. In addition, in order to retain the microorganisms with a slower growth rate than the bacteria in the microorganism holding tank 31, the SRT is preferably set to 24 hours or more, particularly 10 days or more. However, if the SRT is too long, the microorganisms are retained excessively in the microorganism holding tank 31, and the secretions of the microorganisms are also accumulated. Therefore, the SRT is preferably 40 days or less, particularly 10 days or more and 30 days or less. Do.

In addition, in order to secure the food of the microorganisms reproduced in the microorganism holding tank 31, 0.1 wt% or more of the amount of CODcr (organic substance represented by chemical oxygen consumption) of the solids contained in the biological treatment liquid, in particular 5 to 20 It is preferable to allow about 20% by weight of the soluble CODcr to be introduced into the microorganism holding tank 31. The microorganism holding tank 31 may also be added with a substance serving as a nutrient for microorganisms. Particularly preferred as a nutrient is a substance containing a lipid, and lipids include phospholipids, free fatty acids, sterols, and the like. Particularly, substances containing phospholipids such as lysophospholipids and lecithin may be used. It can use suitably. Specifically, rice bran, beer forge, oil forge, sugar beet forage, waste shell powder, egg shell, vegetable extract, fish meat extract, various amino acids, various vitamins, and the like can be used as a nutrient. The amount of addition is preferably 0.01 mg / L / day or more, particularly 0.1-10 mg / L / day, per crude volume.

In addition, as a biological treatment method of the microbial holding tank 31, an activity of conveying sludge separated by installing a solid-liquid separation means such as a settling basin 41 at the rear end of the microbial holding tank 31 as in the present embodiment. In addition to the sludge method, a membrane-separated activated sludge method and the like which provide a separation membrane in the microorganism holding tank 31 can be used. In addition, a carrier suitable for holding microorganisms in the microorganism holding tank 31 may be added to the microorganism holding tank 31. The carrier is not particularly limited, and the carrier described above can be used, and the filling rate is preferably about 10 to 40% by volume per tank.

In the microbial holding tank 31, the dispersible bacteria contained in the biological treatment liquid flowing out of the aeration tank 21 is reduced by predation or self-extinguishing by microorganisms. As a result, the microorganism holding tank 31 consumes the bacteria which become a surplus sludge, reduces sludge, and produces the flocculated floc which the bacteria aggregated and flocculated.

The liquid containing the sludge floc flows out of the microbial holding tank 31, is introduced into the sedimentation basin 41 from the second connecting pipe 45, and is separated from the treated water. The treated water is taken out from the treated water passage 55 connected to the outlet side of the sedimentation basin 41, and a part of the separated sludge is conveyed from the sludge conveying path 65 to the microbial holding tank 31. In the treatment apparatus 11 according to the present embodiment, a portion of the sludge separated from the sedimentation basin 41 is sent from the treatment sludge furnace 57 to the sludge treatment tank 51 to reduce the sludge biologically. In addition, a portion of the sludge separated from the settling basin 41 may be conveyed to the aeration tank 21.

The sludge treatment tank 51 may have the same configuration as that of the microorganism holding tank 31. Specifically, the sludge treatment tank 51 supplies oxygen-containing gas such as air from a gas supply means 51 such as an acid engine, grows micro organisms, and further reduces the amount of sludge generated by using the predation action of the micro organisms. do. A carrier may be added to the sludge treatment tank 51 similarly to the microorganism holding tank 31, and a nutrient may be added to promote the growth of the microorganisms.

Except for the part returned to the microbial holding tank 31 and the part sent to the sludge treatment tank 51 of the sludge floc which could not be processed by the sludge treatment tank 51 and / or the sludge taken out from the sedimentation basin 41. The remaining sludge floc can be discharged out of the system from the sludge discharge passage 56.

This invention controls the oxygen supply amount to the aeration tank 21, and promotes the propagation of the dispersible bacteria in the aeration tank 21, The said Example can be modified suitably. For example, as shown in FIG. 2, the inflow amount of organic wastewater flowing into the aeration tank 21 and the organic matter concentration of the organic wastewater by using the processing apparatus 12 having the flowmeter 26 installed in the raw water reactor 25 are shown. Based on the amount of oxygen required by the aeration tank 21, the amount of oxygen supplied can be controlled.

In addition, a carrier can be added to either or both of the aeration tank 21 and the microorganism holding tank 31. Preferable types and filling rates of the carrier added to each tank are as described above. 3, the schematic diagram of the processing apparatus 13 which added the support | carrier 58 to the aeration tank 21 is shown. In addition, a nutrient or the like can be added to promote the growth of the microorganisms in the microorganism holding tank 31. In addition, the sludge treatment tank 51 may chemically reduce sludge by blowing ozone or the like, or physically reduce sludge by mechanical destruction or the like.

Next, with reference to FIG. 4 and FIG. 5, the method to stabilize micro biomass by controlling the soluble BOD sludge load of the microorganism holding tank 31 is demonstrated. The processing apparatus 14 of FIG. 4 is equipped with the aeration tank 21, the microorganism holding tank 31, and the sedimentation basin 41 to solid-liquid separation means. In the treatment apparatus 14, instead of controlling the DO concentration of the aeration tank 21, the microbial holding of the microbial holding tank 31 is controlled by controlling the soluble BOD sludge load on the microbial holding tank 31. By stabilizing the amount, the control of the DO concentration in the aeration tank 21 does not need to be carried out in particular, so that the DO system is not provided in the aeration tank 21. However, in order to promote the production of dispersible bacteria in the aeration tank 21 as described above, the dissolved oxygen concentration of the aeration tank 21 is not too high, and the DO of the aeration tank 21 also in the treatment apparatus 14 is It is preferable to set it as 0.5 mg / L or less.

In the processing apparatus 14, the soluble BOD sludge load of the microorganism holding tank 31 is controlled within a predetermined range, and specifically, the soluble BOD sludge load is made into 0.05 kg-BOD / kg-VSS / day or less. Alternatively, the microorganism holding tank 31 is preferably operated at aerobic conditions by supplying an oxygen-containing gas from the gas supply means 32 at a pH of 5 to 8. In the processing apparatus 14, in order to propagate the microorganisms with a slow growth rate, the microorganism holding tank 31 has a SRT of 12 hours or more and 40 days or less, preferably 30 days or less, more preferably 10 to 30 days. It's good to drive around. In the microbial holding tank 31, it is preferable to circulate a part of the solid content (sludge) separated from the liquid component in the sedimentation basin 41 at the rear end as a return sludge. Alternatively, by providing a separation membrane in the microbial holding tank 31, a membrane separation method for holding sludge in the tank may be used. The microorganism holding tank 31 may be a fluidized bed by filling the carrier. In this case, the carrier to be filled in the microorganism holding tank 31 is not particularly limited, and the carrier described above can be used.

In the aeration tank 21, a biological treatment liquid mainly containing dispersible bacteria flows out and flows into the microbial maintenance tank 31. The microorganisms are held in the microorganism holding tank 31, and the dispersible bacteria contained in the biological treatment liquid flowing out of the aeration tank 21 is reduced by predation or self-extinguishing by the microorganisms. The microorganism holding tank 31 also grows bacteria by using the remaining organic matter contained in the biological treatment liquid as a substrate, but since the soluble BOD sludge load on the microorganism holding tank 31 is low, the growth of bacteria is microorganisms. It stays to the extent that it is consumed by the food which is needed to maintain the microbial number maintained in the holding tank 31.

As a result, the microorganism holding tank 31 holds a predetermined amount of microorganisms, and consumes the sludge as a surplus sludge, reduces sludge, and generates flocculation flocculated by the aggregation of bacteria. The sludge floc has an SVI (ml of sedimentation volume per 1 g of sludge) of about 150 or less, and is easily separated from the liquid in the sedimentation basin 41.

The liquid containing the sludge floc flows out of the microbial holding tank 31, is introduced into the sedimentation basin 41 from the second connecting pipe 45, and is separated from the treated water. The treated water is taken out from the treated water passage 55 connected to the outlet side of the sedimentation basin 41, and at least a part of the separated sludge is conveyed from the sludge conveying path 65 to the microbial holding tank 31. Some of the sludge separated from the sedimentation basin 41 may be discharged out of the system as surplus sludge from the sludge discharge path 56 branched from the sludge conveying path 65. In addition, a part of the conveying sludge may be conveyed to the aeration tank 21, and a sludge treatment tank (not shown) which introduces a surplus sludge to reduce the sludge in a biological, chemical, or physical method is included in the treatment apparatus 14. In addition, it is possible to further reduce the amount of excess sludge generated.

The present invention introduces a biological treatment liquid containing separable bacteria generated by biological treatment at high load into the microbial holding tank 31 to maintain the soluble BOD sludge load in a predetermined range. It is intended to flocculate and reduce the sludge through predation by the above-described method, and the embodiment can be modified as appropriate. For example, a carrier can be added to either or both of the aeration tank 21 and the microbial holding tank 31. Preferable types and filling rates of the carrier added to each tank are as described above. In addition, a nutrient or the like may be added to promote the growth of the microorganisms in the microorganism holding tank 31.

In addition, as shown in FIG. 5, the raw water passage 25 may be branched to directly introduce a portion of the raw water into the microorganism holding tank 31. In this way, the separation rate of the soluble BOD contained in the raw water introduced into the aeration tank 21 is taken into consideration by configuring a device for supplying a part of the raw water to the microbial holding tank 31 without passing through the aeration tank 21. The amount of raw water to bypass the microbial holding tank 31 can be adjusted. For this reason, in the processing apparatus 15 shown in FIG. 5, it becomes easy to adjust the operating conditions of the microorganism holding tank 31 so that it is suitable for holding | maintenance and flocculation of microorganisms.

Example 1

Hereinafter, the present invention will be described in more detail based on Examples. As Example 1, an artificial wastewater (CODcr concentration of 1,200 ml / L, soluble BOD concentration of 600 mg / L, and soluble CODcr concentration of 1,100 mg / L) was tested with treated water using the treatment apparatus 11 shown in FIG. did. The aeration tank 21 was operated with a capacity of 3.6 L without pH 7.0, HRT 4 hours, and return sludge. In the aeration tank 21, since 80% of the soluble CODcr contained in the water to be treated and the total CODcr concentration decrease by 30%, the oxygen supply amount is controlled based on the total amount of CODcr decomposed in the aeration tank 21, so that the DO of the tank liquid is reduced. The concentration was 0.01 mg / L.

The microbial holding tank 31 was operated at a capacity of 15 L with a sludge load of 0.044 kg-BOD / kg-VSS / day with a MLVSS concentration of 3,900 mg / L, a pH 7, soluble BOD, and HRT 17 hours. About the microbial holding tank 31, oxygen was supplied so that DO of 2-3 g / L of tank liquid might become. The microbial holding tank 31 conveyed a part of sludge floc separated from the sedimentation basin 41 via the sludge carrying path 65. In Example 1, the sludge discharge path 56 is used as a surplus sludge except for returning the sludge floc separated from the sedimentation basin 41 to the microorganism holding tank 31 without using the sludge treatment tank 51. Exhausted out of the system.

As a result of the treatment under the above conditions, in the aeration tank 21, the proportion of the bacteria in the dispersed state of about 1 to 5 um in length with respect to the cells SS is about 80%, which can proliferate disperse bacteria predominantly. there was. In addition, the microbial holding tank 31 reproduces predominantly at the concentration of 100,000-130,000 / ml (10-13% of MLVSS), and the sludge conversion rate of BOD contained in the water to be treated is 0.15 kg-. The SS concentration of the treated water taken out from the MLSS / kg-BOD and the sedimentation basin 41 was changed to about 20 mg / L or less.

[Example 2]

The experiment was carried out under the same conditions as in Example 1 except that the oxygen supply to the aeration tank 21 was intermittently performed. That is, in Example 1, the oxygen supply to the aeration tank 21 is continuously performed, whereas in Example 2, the oxygen supply to the aeration tank 21 is intermittently performed, so that DO of the tank liquid in the aeration tank 21 is decreased. The aerobic period of 2 mg / L was 1 minute, the oxygen deficiency period of 0 mg / L for DO was 1 minute, and the period (fulfillment period) between 0 and 2 mg / L for DO was 2 minutes.

As a result, in the aeration tank 21, the proportion of the bacteria in the dispersed state of about 1 to 5 um in length with respect to the cells SS was about 70%, and the dispersible bacteria could proliferate predominantly. In addition, the microbial holding tank 31 is predominantly reproduced at a concentration of about 100,000 pieces / ml species, the sludge conversion rate of BOD contained in the water to be treated is 0.20kg-MLSS / kg-BOD, the sedimentation basin (41). The SS concentration of the treated water taken out from) changed to about 20 mg / L or less.

[Example 3]

By calculating the oxygen consumption rate in the aeration tank 21, the experiment was carried out under the same conditions as in Example 1 except that the oxygen supply amount required for the biotreatment in the aeration tank 21 was obtained to control the oxygen supply amount. Specifically, once per hour, the oxygen supply amount to the aeration tank 21 is increased to temporarily increase the DO concentration of the tank liquid in the aeration tank 21 (2 minutes), and then temporarily decrease the oxygen supply amount. (Or stopped), the rate of oxygen consumption was determined from the rate of decrease of the DO concentration in the crude liquid. 6, the control pattern of the oxygen supply amount in Example 3 is shown. In the present Example, based on the oxygen consumption rate calculated | required in this way, oxygen supply rate was controlled so that DO density | concentration of the aeration tank 21 might be 0.01 mg / L.

As a result, in the aeration tank 21, the proportion of the bacteria in the dispersed state of about 1 to 5 um in length with respect to the cells SS was about 90%, and the dispersible bacteria could proliferate predominantly. In addition, the microbial holding tank 31 is predominantly reproduced at a concentration of about 100,000 to 130,000 pieces / ml, and the sludge conversion rate of BOD contained in the water to be treated is 0.15kg-MLSS / kg-BOD, and the sedimentation basin. The SS concentration of the treated water taken out in (41) was changed to about 20 mg / L or less.

[Referential Example 1]

In Reference Example 1, the DO concentration control in the aeration tank 21 was examined. Specifically, the experiment was carried out under the same conditions as in Example 1 except that the DO concentration of the crude liquid in the aeration tank 21 was set to the same value as the microorganism holding tank 31, that is, 2 to 3 mg / L. In the aeration tank 21, the thread type bacteria of about 10-50 micrometers in length became the dominant state which propagated more than the bacteria of the dispersed state of about 1-5 micrometers in diameter, and predation by microorganisms became difficult. As a result, the microbial concentration of the microbial holding tank 31 is lowered to a concentration of 10,000 to 20,000 / ml (1 to 2% of MLVSS), and the sludge conversion rate of BOD contained in the water to be treated is 0.30kg- The SS concentration of MLSS / kg-BOD and the treated water taken out from the settling basin 41 was about 30 mg / L.

Example 4

The aeration tank 21 is filled with a sponge carrier 58 having a 5 mm angle at a volumetric volume ratio of 5% with respect to the aeration tank 21, using the treatment apparatus 13 of FIG. 3 in which the aeration tank 21 is a fluidized bed. The experiment was conducted. In Example 4, the same conditions as in Example 1 were applied except that the carrier 58 was filled in the aeration tank 21, and the oxygen supply amount was controlled to control the DO concentration in the aeration tank 21 to be 0.01 mg / L. . As a result, in the aeration tank 21, the proportion of bacteria in the dispersed state of about 1 to 5 um in length with respect to the cells SS was about 80%, and the dispersible bacteria could proliferate predominantly. In addition, the microbial holding tank 31 is predominantly reproduced at a concentration of about 100,000 to 130,000 / ml species, and the sludge conversion rate of BOD contained in the water to be treated is 0.15kg-MLSS / kg-BOD, and the sedimentation basin. The SS concentration of the treated water taken out in (41) was changed to about 20 mg / L or less.

In Example 4, the flow rate of the organic wastewater flowing into the aeration tank 21 is halved one month after the start of the experiment, and the half of the BOD volume load to the aeration tank 21 is halved. Through the sedimentation basin 41, the treated water separated from the sludge floc was returned to the aeration tank 21. The conveyed amount of treated water was made into the same quantity as the decrease of organic wastewater. Thus, after continuing the process which reduced the to-be-processed water flow rate for 12 hours, it returned to the to-be-processed water flow rate, and continued the process which stops conveyance of the treated water for 12 hours. In the meantime, the HRT of the aeration tank 21 could be kept substantially constant by conveying the treated water at the time of decreasing the amount of water to be treated. In the meantime, in the aeration tank 21, the predominant state of the dispersible bacteria is maintained, the sludge conversion rate can also be maintained at the above-mentioned value, and the concentration of species worms in the microorganism holding tank 31 is 100,000 to 130,000 / ml The value could be maintained.

[Reference Example 2]

In Reference Example 2, the experiment was conducted under the same conditions as in Example 4 except that the treated water was conveyed when the flow rate of the water to be treated in Example 4 was decreased. In the reference example 1, the test which repeated the process which reduces the to-be-processed water flow volume for 12 hours and returns the flow rate for the next 12 hours was continued for three days, and the dispersion state which predominantly existed in the aeration tank 21 was carried out. It turned into a bacterium, and a thread-shaped bacterium of about 20 to 1,000 um in length predominated. In the microbial oil holding tank 31, the number of species of insects decreased to about 12,000 / ml, and the sludge conversion rate rose to 0.40 kg-MLSS / kg-BOD. The SS concentration of the treated water taken out from the settling basin 41 was about 40 mg / L.

The results of Examples 1 to 4 and Reference Examples 1 and 2 are shown in Table 1 below.

Table 1

Oni conversion rate
(kg-MLSS / kg-BOD) Aeration tank
DO (mg / L) In the aeration tank
Dominant bacteria length (㎛) Treated Water SS
Concentration (mg / L) Number of species bugs of microorganisms (N / ml) Example 1 0.15 0.01 1-5 ≤20 100000-130000 Example 2 0.20 0.20 1-5 ≤20 100000 Example 3 0.15 0.01 1-5 ≤20 100000-130000 Example 4 0.15 0.01 1-5 ≤20 100000-130000 Reference Example 1 0.30 2.00 10-50 30 10000-20000 Reference Example 2 0.40 0.01 20-1000 40 12000

As described above, according to the present invention, in the aeration tank 21, the dispersible bacteria are predominant, and in the microbial maintenance tank 31 provided at the rear end of the aeration tank 21, the predatory operation of the microorganisms is used. The amount of generation could be reduced.

[Referential Example 3]

Next, Reference Example 3 for controlling the soluble BOD sludge load for the microorganism holding cell 31 will be described. In Reference Example 3, an artificial wastewater (CODcr concentration of 1,000 mg / L, soluble BOD concentration of 640 mg / L) was used as the water to be treated using the treatment apparatus 15 shown in FIG. The aeration tank 21 was operated without return sludge with a capacity of 3.6L, pH 7, HRT 4 hours, and DO concentration of 1.0 mg / L. The microorganism holding tank 31 was operated at a capacity of 15 L, pH 7, MLVSS 3,700 mg / L, and HRT 17 hours. The decomposition rate of the soluble BOD in the aeration tank 21 is about 95%, and a part of the raw water is introduced directly into the microbial holding tank 31 from the bypass passage 26, so that the microbial holding tank 31 The solubility BOD sludge load with respect to the amount of sludge in a tank was 0.03 kg-BOD / kg-VSS / day. In Reference Example 3, the soluble BOD volume load of the whole biological treatment tank including the aeration tank 21 and the microbial holding tank 31 was 0.75 kg / m ³ / day, and HRT 21 hours.

As a result of the treatment under the above conditions, the microbial oil holding tank 31 reproduces predominantly with leech roundworms at a concentration of 50,000 / ml (15% of MLVSS), and the sludge conversion rate of BOD contained in the water to be treated is 0.20. kg-MLSS / kg-BOD. In addition, the SS concentration of the treated water taken out from the settling basin 41 changed to about 10 mg / L or less.

[Reference Example 4]

Under the same conditions as in Reference Example 3, the direct introduction of raw water into the microorganism holding tank 31 was stopped and the soluble BOD sludge load on the microorganism holding tank 31 was 0.01 kg-BOD / kg-VSS / day. Experimented. As a result, the reproductive water of the microorganisms in the microorganism holding tank 31 became 1,000 pieces / mL (1% of MLVSS) or less, and sludge reduction and flocculation did not progress by the phagocytosis of microorganisms. Accordingly, in Reference Example 4, the sludge conversion rate of BOD contained in the water to be treated was BOD, so that the SS concentration of 0.30 kg-MLSS / kg-BOD and the treated water was 30 mg / L.

Reference Example 5

Experiments were carried out under the same conditions as in Reference Example 3 except that the amount of raw water inflow into the microorganism holding tank 31 was increased and the soluble BOD sludge load on the microorganism holding tank 31 was 0.1 kg-BOD / kg-VSS / day. . As a result, the microorganisms in the microorganism holding tank 31 multiply in the form of yarns, and it is difficult to be fed to microorganisms, and the reproductive water of the microorganisms is 1,000 pieces / mL or less. Therefore, sludge reduction and flocculation did not proceed due to the phagocytosis of microorganisms. In Reference Example 5, the sludge conversion rate of BOD contained in the water to be treated was 0.40 kg-MLSS / kg-BOD as BOD. In Reference Example 5, the SS concentration of the treated water was 10 mg / L, but due to the growth of filamentous bacteria, the consolidation of sludge decreased, and the SVI was 220.

Reference Example 6

The raw water inflow into the microorganism holding tank 31 was increased, and the soluble BOD sludge load on the microorganism holding tank 31 was tested under the same conditions as in Reference Example 3 except that 0.08 g-BOD / kg-VSS / day was used. . As a result, the reproductive water of the microorganisms in the microorganism holding tank 31 also became 30,000 / mL (7% of MLVSS). Accordingly, the sludge conversion rate of BOD contained in the water to be treated was 0.20 kg-MLSS / kg-BOD as BOD. However, the predominant microorganisms are floc predatory worms that feed on and feed the flocs, so the flocs are eaten and the SS concentration of the treated water is 120 mg / L.

Table 2 shows the results of Reference Examples 3 to 6.

[Table 2]

To microbial maintenance tank
Soluble BOD sludge load
(kg-BOD / kg-VSS / d) Oni conversion rate
(kg-MLSS / kg-BOD) Treated water SS concentration
(mg / L) Microbial water of microorganism maintenance tank
(Piece / mL) Reference Example 3 0.03 0.20 10 50000 leech roundworm Reference Example 4 0.01 0.30 30 1000 or less Reference Example 5 0.1 0.40 10 1000 or less Reference Example 6 0.08 0.20 120 300000 (cigarettes)

As shown in Table 2, by controlling the soluble BOD sludge load in the microorganism holding tank 31, it was possible to reduce the amount of surplus sludge using the phagocytosis of the microorganisms. In addition, in the microbial holding tank 31, it was possible to promote the flocculation of bacteria and to produce a sludge floc with good settling property, thereby obtaining treated water of good quality.

Reference Example 7

As a reference example 7, the reproductive water of the microorganisms in the microorganism holding tank 31 when the soluble BOD sludge load to the microorganism holding tank 31 was changed was investigated. The results are shown in Fig.

As shown in FIG. 7, the microorganism of the filtration predation type which inhales and disperse | distributes dispersible bacteria by making the soluble BOD sludge load to the microorganism holding tank 31 about 0.05 kg-BOD / kg-VSS / day or less. Could dominate. As a result, by setting the soluble BOD sludge load to the microbial holding tank 31 to 0.05 kg-BOD / kg-VSS / day or less, it was possible to prevent the sludge floc collapse and to obtain treated water of good quality.

The present invention can be used for biological treatment of organic wastewater such as sewage.

Claims (9)

A high load treatment step of introducing an organic wastewater containing organic matter into the aeration tank for biotreatment under aerobic conditions; And And a low load treatment step of introducing the biological treatment liquid flowing out of the high load treatment step into a microbial holding tank for biological treatment. The dissolved oxygen concentration of the aeration tank of the high load treatment process is controlled to 0.5 mg / L or less, and the soluble BOD sludge load of the microbial holding tank of the low load treatment process is 0.025 kg-BOD / kg-VSS / day. More than 0.05kg-BOD / kg-VSS / day or less, Biological treatment of organic wastewater which produces dispersible bacteria using the organic material as a substrate in the high load treatment step, and predisposes the dispersible bacteria by micro organisms grown in the microbial holding tank in the low load treatment step. Way. delete delete The method of claim 1, In the high load treatment process, the amount of CODcr to be decomposed in the high load treatment process is determined by measuring the inflow amount of the organic wastewater into the aeration tank and the concentration of the organic matter contained in the organic wastewater, and based on the amount of CODcr to be decomposed A biological treatment method for organic wastewater, characterized in that the supply amount is controlled. The method of claim 1, A biological treatment method for organic wastewater, characterized in that an oxygen depletion period for temporarily stopping the oxygen supply in the high load treatment step is provided. The method of claim 5, In the high load treatment step, the oxygen depletion period for temporarily stopping the oxygen supply amount controls the oxygen supply amount such that the aeration tank is 0.25 to 1 times the length of the aerobic period in the aerobic condition. Method of biological treatment of wastewater. The method according to any one of claims 1 and 4 to 6, In the high load treatment step, the oxygen supply amount is controlled so that the difference between the oxygen consumption rate and the oxygen supply rate is 10% or less. The method of claim 1, The microbial holding tank, wherein the microorganism is reproduced at a concentration of 5% or more of the sludge MLVSS, biological treatment method of organic wastewater. The method of claim 1, The organic wastewater treatment method for organic wastewater, characterized in that the organic wastewater bypassed by the aeration tank is introduced directly into the microbial holding tank.

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