JPH02233199A - Fixed bed deep tank wastewater treatment method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fixed-bed deep-layer wastewater treatment method for biologically treating wastewater such as sewage in a treatment tank in a shallow layer.

[Industrial application field]

Conventionally, a wastewater treatment tank formed at a depth of 40 to 150 m underground is divided into an ascending section and a descending section for wastewater, and a contact oxidation tank for biologically treating wastewater is provided in the ascending section. A layered wastewater treatment device has been proposed in Japanese Patent Application Laid-Open No. 61-212388.

In this deep wastewater treatment device, wastewater is supplied to the descending section,
It is sent to the contact oxidation tank together with the aeration air supplied in the descending section and/or the ascending section.

In a contact oxidation tank, a biofilm of aerobic microorganisms is formed on the surface of the mouthpiece, and the growth of microorganisms is promoted by the oxygen contained in the air. Then, organic matter and degradable substances in suspended solids (hereinafter referred to as "SS") of the wastewater passing between the mouthpieces are sorbed by the biofilm and removed from the wastewater. The organic substances adsorbed on the biofilm are taken into the bodies of microorganisms and decomposed into inorganic substances such as carbon dioxide, ammonia, and water.

Therefore, according to the wastewater treatment apparatus, organic matter and SS in wastewater can be efficiently removed, and the generation of sludge can be reduced.

By the way, since the microorganisms are aerobic, a sufficient supply of oxygen is essential to maintain and activate their activities.

[Problem to be solved by the invention]

However, the previously proposed deep wastewater treatment methods and devices described above have a problem in that the decomposition ability of microorganisms cannot be fully demonstrated because atmospheric air is supplied.

Further, in the deep wastewater treatment apparatus described in the embodiment of the above-mentioned publication, the contact oxidation tank is provided at the upper part of the rising part. Therefore, the air supplied in the lower part of the descending part and/or the rising part expands as it rises. That is, even minute bubbles at the bottom of the wastewater treatment layer become quite large in the upper layer. Therefore, the air passing through the contact oxidation tank is very large, and as the air bubbles expand, their scraping effect on the biofilm tends to increase, resulting in the problem that the biofilm attached to the mouth material is peeled off. Was.

Therefore, an object of the present invention is to provide a method for treating soot layer wastewater that can maintain and activate microorganisms in a biological treatment tank provided in a wastewater treatment tank.

[Means to solve the problem]

The present invention has been made to achieve the above object,
The configuration will be described with reference to the accompanying drawings showing one embodiment.

In the first fixed bed deep wastewater treatment method, as shown in FIG.
, which biologically treats this wastewater (4) by supplying oxygen (6) to the wastewater (4) before the wastewater (4) is sent to the fixed bed assembly layer (2). It is.

As shown in FIG. 2-3, the second fixed-bed deep-layer wastewater treatment method collects air contained in the wastewater (25) in the deep-layer treatment tank (l1) into a recovery unit ( 2 0
, 2 1.2 2).

[Effect]

In the first fixed bed deep wastewater treatment method, oxygen (6) is supplied before the wastewater (4) reaches the fixed bed assembly layer (2),
Since it comes into contact with the microorganisms in a state with sufficient dissolved oxygen, the supply of oxygen to the microorganisms increases, and the decomposition ability of the microorganisms is fully developed.

In the second fixed bed deep wastewater treatment method, excess air bubbles contained in the wastewater (25) are collected in the collection section (2 0, 2 1.22). Therefore, the biofilm of the fixed bed assembly layer (17) is not peeled off by the expanded large bubbles.

〔Example〕

Hereinafter, an apparatus using the fixed bed deep wastewater treatment method according to the present invention will be described with reference to the accompanying drawings.

《First Example》 In Fig. 1, the treatment layer 1 is formed in a vertical hole with a depth of 40 to 150 m formed by a mechanical excavation method such as a reverse circulation method or an earth drilling method. This is a tube loaded with tubes. The fixed floor assembly layer 2 is
A fixed bed assembly (mouth material) 3 is filled over almost the entire length of the treatment tank 1. The fixed bed assembly 3 may be made of any material as long as it is not harmful to the growth of aerobic microorganisms, such as plastic balls, crushed stone, ceramics, wood cloth, etc. Further, the fixed bed assembly 3 needs to have voids between them in a filled state through which waste water can sufficiently pass. Note that the size of the fixed bed assembly 3 may be different for each stage depending on the depth.

The wastewater 4 is supplied to an oxygen supply tank 5.
Oxygen 6, which is supplied from the bottom of the tank, is dissolved in the wastewater. Note that if the inside of the oxygen supply tank 5 is kept in a pressurized state, the dissolved rate of oxygen 6 will further increase.

Wastewater 4 containing dissolved oxygen 6 and bubbly oxygen 6
is temporarily stored in the storage tank 7. It is desirable that the storage tank 7 is also pressurized in the same way as the oxygen supply tank 5 to prevent oxygen from leaching out of the wastewater.

The wastewater 4 in the storage tank 7 is supplied to the bottom of the treatment tank 1 by a pump 8.

The wastewater 4 supplied to the treatment tank 1 ascends the fixed bed assembly layer 2. On the other hand, a biofilm consisting mainly of aerobic microorganisms is formed on the surface of the fixed bed assembly 3 that comes into contact with the wastewater 4. This biofilm ingests oxygen 6 dissolved in the wastewater 4, propagates, and increases its thickness.

As the wastewater 4 passes between the fixed bed assemblies 3, it comes into contact with the biofilm. The organic substances contained in the wastewater 4 and the decomposable substances contained in the SS are sorbed and absorbed by the microorganisms and decomposed into inorganic substances.

Here, the wastewater 5 is supplied with oxygen 6 in advance and is sufficiently dissolved, and since sufficient oxygen is supplied to the microorganisms, the decomposition ability of the microorganisms is extremely high, and the wastewater 4 is highly purified. . Moreover, it can sufficiently cope with load fluctuations.

Therefore, the transparency of the treated water 9 that passes through the fixed bed assembly layer 2 and is discharged from the upper part of the treatment tank 1 increases.

Specifically, a deep aeration device (Japanese Patent Application Laid-Open No. 1983-1999) is a deep aeration system in which a treatment tank is provided with an ascending section and a descending section, and wastewater is treated while being aerated.
The type proposed in Publication No. 245898, etc. )
Then, the average suspended solids concentration in the treatment tank (rMLSSJ
That's what it means. ) is about 4,503 mg/Q, while
In the processing device of this embodiment, it is approximately 7,000 MLSS.
Omg/(+), microorganisms are held in a highly concentrated state in the treatment tank, and the wastewater treatment capacity is much higher than that of conventional ones.

In this embodiment, the fixed bed assembly layer 2 is provided over almost the entire length of the processing tank I, but it may be divided into multiple stages or may be limited to only a portion.

<<Second Embodiment>> In FIG. 2, a processing tank 1l is formed in the same manner as in the first embodiment, and has an inner pipe l2 equipped with a collection pipe 20 on the outer periphery, and a It is divided into a descending part 13 located at
The descending portion 13 and the ascending portion l4 are connected through a space located below the inner tube l2.

The inside of the inner tube 12 is partitioned into multiple stages by redistribution filters 15. This redistribution filter 15 has holes 15a (see FIG. 4) uniformly formed throughout.

A gas-liquid separation plate 16 is provided below the redistribution filter 15 and faces diagonally downward. The outer peripheral portion of the gas-liquid separation plate l6 except for its lower end side is welded to the inner surface of the inner tube 12 to block air circulation, and a passage l is formed between the lower end and the inner tube l2.
7 is formed.

Gas-liquid separation plate I6 and redistribution filter 1 located below it
A fixed bed assembly layer I8 is provided between the fixed bed assembly layer I8 and the fixed bed assembly layer I8, which is filled with the fixed bed assembly l9 shown in the first embodiment. Further, as shown in FIG. 4, a float valve 22 is provided in the space 2l formed between the gas-liquid separation plate l6 and the fixed bed assembly layer l8.

The float valve 22 is attached to the inner surface of the inner pipe 12,
As the float 23 rises, the space 2l and the recovery pipe 20 provided on the outer peripheral surface of the inner pipe 2 are brought into communication. Note that the lower end of the recovery pipe 20 is closed, and the upper end is open to the atmosphere. However, in the case where oxygen is dissolved in the waste water 25 as in the first embodiment, the collection pipe 2
The upper end of 0 is connected to a collection container to collect oxygen.

In the fixed bed wastewater treatment apparatus having the above configuration, air or oxygen is supplied to the bottom of the treatment tank 11 by the compressor 24, and this air and oxygen rise through the rising portion I4 in the inner pipe 12.

The waste water 25 is supplied to the upper part of the descending part l3, passes through the bottom of the treatment tank 11, and rises together with the air in the rising part l4 due to the air lift effect of the flow formed by the air supplied from the compressor 24.

The wastewater passing through the fixed bed assembly layer 18 comes into contact with the biofilm generated on the surface of the fixed bed assembly 19, and organic matter and SS are removed.

On the other hand, the air rising through the fixed bed assembly layer l8 expands as the water pressure decreases due to the rise, and when it passes through each fixed bed assembly layer I8, most of it is captured in the space 2l below the gas-liquid separation plate 16. Ru. When the stored air in the space 21 exceeds a predetermined amount and the liquid level there falls below a predetermined level, the valve 22 is opened by the seven funnels 23 that move up and down along the liquid level, and the air in the space 21 is released into the recovery pipe 20. is discharged.

At this time, the waste water 25 above the space 2l descends simultaneously with the exhaust, creating a backflow. As a result, the flow of the rising wastewater 25 is temporarily disturbed, so that the wastewater 25 and the fixed bed assembly I9
In other words, the contact between the wastewater 25 and the biofilm increases, and the treatment effect of the wastewater 25 increases.

The waste water 25 and air that have passed through the fixed bed bulk layer 18 and the passage l7 above it are uniformly distributed over the cross section of the rising part l4 by the redistribution filter 15, and are further distributed to the upper fixed bed assembly layer l8.
sent to.

In this way, the wastewater 25 that has passed through the multiple fixed bed assembly layers 18 comes into contact with biofilms in each layer, and organic matter and SS components are removed.

In addition, as mentioned above, the float valve 2 provided for each layer
2, etc., excess air is collected and distributed evenly by each redistribution filter 15, so that expanded large air bubbles do not pass through the fixed bed assembly layer 18 as is. Therefore, the biofilm on each fixed bed assembly layer 18 is not destroyed or peeled off, so that the wastewater 25 can be stably treated, and the transparency of the treated water 26 is increased.

Furthermore, since air is removed in the treatment tank 11 in this manner, there is no need to further deaerate the treated water 26 in a deaeration tank (not shown). Alternatively, the deaeration tank can be downsized.

In this embodiment, the float valve 22 is used to exhaust air from the space 2L, but a pressure valve may be used, and in short, any means that can exhaust air intermittently may be used.

Further, the structure for recovering air is not limited to the above embodiment.

<<Arrangement example of fixed bed assembly layer, etc.>> The arrangement of the fixed bed assembly layer and the air supply ports may be as shown in FIGS. 4 to 6. In addition, in these figures, 3l
is a processing tank, 32 is an inner pipe, 33 is a descending part, 34 is a rising part,
35 is a fixed bed assembly layer, 36 is a compressor, and 37 is an air diffuser port.

In the ripening apparatus shown in FIG. 4, a fixed bed assembly layer 35 is provided only on the rising section 34, and an air diffuser port 37 is arranged at the bottom of the fixed bed assembly layer 35. In the processing apparatus shown in FIG. 5, a fixed bed assembly layer 35 is provided over the entire ascending section 34 and the lower part of the descending section 33, and is dispersed at a position above the fixed bed assembly layer 35 provided in the descending section 33. Air mouth 3
7 is placed. In the processing apparatus shown in FIG. 6, the fixed bed assembly 35 is filled in the rising part 34 and the bottom of the processing tank 3l.
The air diffuser 37 is arranged in the middle of the descending section 33.

《Experiment example》 Below, we made a model of the fixed bed wastewater treatment equipment shown in Figure 1.
We will explain the experiments confirmed regarding the wastewater treatment status.

I. The Riactor, which corresponds to the experimental equipment processing tank, has an inner diameter of 20 cm and a height of 1 m.
Use a transparent acrylic laminate.

The fixed bed assembly is made of terraret (PVC) with a diameter of 6 cm.
An elliptical frame (manufactured by Nippon Steel Kakoki Co., Ltd.) was used, and the reactor was filled with this.

The aeration (oxygen supply) method involves supplying liquid oxygen and nitrogen after adjusting them to a predetermined ratio using a mass 7-row meter.

The reactor was equipped with a constant pressure valve to intermittently draw out treated water to maintain a constant pressure inside the reactor.

A heater was installed at the inlet of wastewater into the reactor to maintain a constant water temperature within the reactor.

i. Experimental method Runl (Experiment to understand processing setting conditions Part 1) By changing the oxygen concentration in the aeration, the dissolved oxygen (hereinafter referred to as "Do") in the reactor was changed and the treatment results were compared. Considering the possibility that the treatment situation may change depending on the reproducibility check and load conditions, the inflow substrate water volume was set at 190 m
The experiment was conducted under two conditions: Q/min and 150 m (2/min).The experiment was conducted at normal pressure, and the experimental conditions are shown in Table 1.

Run2 (: Processing setting condition understanding experiment part 2) Runl
From the results of 2013, it became clear that it was necessary to conduct the experiment at a high Do level, as the load was relatively low and there was not much difference in the treatment results.
80 mQ/min) and using the pressurized oxygen method. The experimental conditions are shown in Table-2.

[Margins below] Table I Experimental Conditions for Run 2 Experimental Conditions for Run 2 When the main pressure is applied, the apparent value is as follows. Experimental Results (1) Runl Results ■Environmental Conditions The water temperature in each experiment was within a range of about 23±2°C. Moreover, the pH inside the reactor was approximately 6.5, and there was almost no difference observed due to the difference in oxygen concentration during aeration. The results of DO in each experiment are shown in FIGS. 7(a) and (b). From the figure, it can be seen that the oxygen concentration during aeration and Do in the actor are almost proportional. In addition, in pure oxygen aeration, D
O rose to about 26 mg/L, and D◯ did not show any difference with this level of water amount difference.

■SS and organic matter Figure 8 shows the change in SS in Runl's treated water.

In either case, there was a tendency for the outflow SS to suddenly decrease after slightly exceeding D○ at the time of air aeration when atmospheric air was supplied.

In other words, it was shown that if even a small amount of oxygen is added to the atmosphere and supplied to the treated water, the SS removal efficiency can be significantly increased.

There was no significant difference in SS when Do was 7 ml/L or higher.

Figure 9 shows the measurement results of soluble BOD in the treated water.

When the inflow water amount is Experiment 2, the soluble B○D is 5 mg/
It can be seen that the process is completely completed below L. In addition, in the case of Experiment 1, the higher the Do, the higher the solubility of B in the treated water.
OD is low.

■Effective volumetric load! - 4 kg/m' ・d (water volume 1
At about 50 ml/min), the processing was completed under all setting conditions, so there was no difference between the setting conditions.

Effective volumetric load 1. 7 kg/m”・d (water volume 1
Even in the case of 90 ml/min), the differences in processing conditions due to differences in setting conditions are not very clear.

(2) Results of Run 2 ■Environmental conditions The water temperature during each experiment was kept almost constant at 26±2°C in Experiment 1, and kept almost constant at about 24±1°C in Experiment 2. p
}{ was within the range of 6.0 to 6.5 in each experiment, and almost no pH decrease was observed due to pressurization. Do for each experiment
Figure 10(a) shows the changes in . Shown in (b). Generally Do
is proportional to the oxygen partial pressure during aeration. Large amount of water (7
80 ml/min), Do rose only to just under 60 mg/L even at 2 atm.

■Organic matter and SS Figure 11 shows SS in treated water. The amount of water is low (2
50 ml/min), the SS of the treated water showed a tendency to suddenly decrease just beyond Do during air aeration, as in the case of Runl. Also, D○ is about 45mg
9 or higher, the amount of SS contained in the treated water showed a tendency to increase rapidly. Large amount of water (780 ml/min
) Sometimes it was observed that if the DS was in the range of about 20-60 mg/L, the SS would drop to the range of 20-23 mg/L.

DO and soluble TOC (TOC: organic carbon) in treated water
shows the relationship between In Experiment 1, as in the case of Runl, when the Do was raised slightly above the Do for air aeration, the TOC suddenly dropped, and when the Do was further increased, the TOC tended to gradually rise. In addition, in the case of Experiment 2, as DO increases, T
oC tends to decrease.

Figure 13 shows the change in soluble BOD in the treated water. Experiment 1 shows almost the same tendency as the change in TOC.

■ Figure 14 shows the measurement results for various nitrogen related nitrogen states. It can be seen that in either case, most of the treated water is discharged in the ammonia form. Regarding Experiment 1, it can be seen that nitrification progresses as D○ increases, and as D○ increases further, nitrification is suppressed. In the case of Experiment 2, soluble organic nitrogen gradually decreased up to 1-5 atm, and the concentration of ammonia nitrogen increased accordingly.

■ Biota and biomass At the end of Experiment 2 of Run 2 (90%02 aeration 2 atm
(setting), organisms inside the reactor were collected and examined under a microscope.

Bacteria include the genus Zooglaea and Sphaerotilus, and protozoa and shite include Chilodone.
lla) genus, Paramecium
), the genus Porticella, and as metazoans, the genus Dero and Macrobiotus have appeared.

In particular, the genus Chilodonella appeared frequently. Considering the fact that the genus Cyrodonra is highly sensitive to environments with low dissolved oxygen concentration (does not appear if Do is low) and the biota that have appeared as a whole, under these conditions, ``the load is somewhat high, but it is not possible to treat it.'' can be said to be in good condition.

At this time, the amount of organisms retained in the column is 10 as ss.
300mg/L VS S9800m
g/L, and VSS/SS is 95%.

1v. Summary - It is accurate to use Do as a processing setting condition (taking into account the difference in load).

■If D○ is raised to a certain level, the processing will be good, but if it is raised too much, the processing will not proceed well (white clouding will occur).

(2) It seems appropriate that D○ is about 25 to 50 mg/L as a treatment setting condition. Although it differs slightly depending on the load, it seems appropriate to process latm with 90% 02@ki.

■It is possible to process up to a volumetric load of approximately 7.2 kgBOD/m"・d.

〔Effect of the invention〕

As is clear from the above explanation, in the fixed bed deep wastewater treatment method in which wastewater is passed through the fixed bed assembly layer of a deep treatment tank and this wastewater is biologically treated, the wastewater is sent to the fixed bed assembly layer. According to the first aspect of the invention, the wastewater is sufficiently and evenly dissolved in oxygen and comes into contact with the microorganisms. Therefore, the supply of oxygen to the microorganisms is increased, the ability of the microorganisms to decompose organic matter, that is, the ability to treat wastewater is fully demonstrated, and highly purified water is discharged.

Further, according to the second invention, in the fixed bed deep wastewater treatment method, air contained in the wastewater in the deep treatment tank is recovered by a recovery section provided in the deep treatment tank, in which excess air bubbles contained in the wastewater are recovered. collected at the department.

Therefore, the biofilm on the fixed bed assembly layer is not destroyed or peeled off by the expanded large bubbles, and the biofilm is stably retained on the fixed bed assembly, maintaining constant processing capacity over a long period of time. can do.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the schematic configuration of a fixed-bed deep wastewater treatment device, and FIG. 2 is a cross-sectional view showing the schematic configuration of another fixed-bed wastewater treatment device. Figure 3 is an enlarged sectional view of part ■ in Figure 2;
Figure 6 is a sectional view showing an example of the arrangement of fixed bed assembly layers, etc.; Figure 7 (
Figures 9 a) and 9 are diagrams showing Runi's experimental results, and Figure 7 (a). (b) is a diagram of the relationship between oxygen amount and Do;
Figure 8 is a relationship diagram between Do and SS, Figure 9 is Do and BOD
Relationship diagrams from Figures 10 (a) and (b) to 14
Figures (a) and (b) are diagrams showing the experimental results of Run 2, and Figure 10 (a). (b) is the relationship diagram between oxygen amount and Do, the first
Figure 1 is a relationship diagram between Do and SS, and Figure 12 is a diagram of the relationship between Do and S-T.
The relationship diagram with OC, Figure 13 is the relationship diagram between D○ and BOD,
FIGS. 14(a) and 14(b) are diagrams showing the relationship between the amount of oxygen and the nitrogen content of treated water. 1.11... Processing tank, 2.18... Fixed bed assembly layer,
3, l9...Fixed bed assembly, 4.25...Wastewater, 5.
...Oxygen supply tank, 6...Oxygen, l2...Inner pipe, l3
... Descending part, l4... Rising part, l5... Redistribution filter, 16... Gas-liquid separation plate, 20... Recovery pipe, 2
l... Space, 22... Float valve, 23... Float, 3l... Processing tank, 32... Inner pipe, 33... Descending part, 34... Ascending part, 35... Fixed floor assembly layer.

Claims (2)

[Claims] (1) In a fixed bed deep wastewater treatment method in which wastewater is passed through a fixed bed assembly layer of a deep treatment tank and this wastewater is biologically treated, the wastewater is A fixed bed deep wastewater treatment method characterized by supplying oxygen. (2) In a fixed bed deep wastewater treatment method in which wastewater is passed through a fixed bed assembly layer of a deep treatment tank and the wastewater is biologically treated, air contained in the wastewater of the deep treatment tank is passed through the deep treatment tank. A fixed bed deep wastewater treatment method characterized by collection in a collection section provided.