JP2000051881A - Method and apparatus for treating drainage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat a BOD waste liquid of high concentration efficiently by supplying oxygen in an oxygen supply capacity of at least a specified value in a method for treating drainage containing organic compounds aerobically by using microorganisms. SOLUTION: In an apparatus, oxygen is supplied in an oxygen supply capacity of at least 0.5 kg/m3.hr-O2 to drainage containing organic compounds for aerobic treatment. In this way, microorganisms which decompose a specified substance efficiently are prioritized to increase treatment efficiency. In this process, a treatment tank 1 is equipped with an oxygen supply means capable of prescribed oxygen supply, oxygen-containing gas supplied from an oxygen-containing gas supply line 6 is diffused from a diffuser 3, and oxygen dissolution efficiency is improved by an agitator 2 to obtain a prescribed oxygen supply capacity. By the efficient oxygen supply, the drainage of waste liquid of high BOD (biological oxygen demand) chiefly containing weight-reduction treatment waste liquid of polyester fabrics by sodium hydroxide and others can be treated by a compact apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater containing organic matter by utilizing aerobic microorganisms and a wastewater apparatus.

[0002]

2. Description of the Related Art In an activated sludge method, which is a typical method of wastewater treatment, an organic substance in wastewater is converted into microbial cells by aerobic microbial treatment in an activated sludge tank. First, a solid-liquid separation process is performed to obtain a liquid from which organic substances have been removed.

[0003] The activated sludge method is an existing wastewater treatment method, and although the detailed treatment mechanism has not yet been clarified, it has been maintained by various empirical rules based on many years of experience.
The management method is almost established, and therefore most of the wastewater treatment uses the activated sludge method.

In the activated sludge treatment, solid-liquid separation is usually carried out in a subsequent settling tank, and the supernatant liquid is discharged as treated water. Therefore, sludge forms flocs in the settling tank and the treatment conditions of the activated sludge tank can be settled by gravity. Had to be managed. Therefore, even when it is desired to increase the sludge concentration to increase the treatment capacity, there is a limit due to the sedimentation and separability.
The limit is about 15,000 mg / liter LSS (hereinafter referred to as L). In addition, for raw water having a high concentration, when the raw water is converted into sludge, the raw water already exceeds the MLSS of the management standard, so that it is necessary to dilute and treat the raw water.

[0005] In order to overcome such a situation, there has been a method of improving the treatment conditions of an activated sludge tank, which has been tied to sedimentation separation conditions in recent years, by using membrane separation. According to these, there is no need to consider sedimentation in order to perform the solid-liquid separation operation by membrane separation, and the MLSS 20,000 is not required.
It is clear that operation can be performed at about mg / L, but the treatment method itself is not out of the range of the activated sludge method. I have not reached.

On the other hand, if the sedimentation / separation property is neglected, a method of retaining a large number of microorganisms per unit volume, that is, a high MLS
By operating at S, it becomes possible to treat high-concentration BOD wastewater. However, in order to use this method, it is necessary to supply oxygen corresponding to its decomposing ability, and ordinary activated sludge has not much ability to decompose microorganisms.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an aerobic wastewater treatment, particularly a wastewater treatment method and a wastewater treatment apparatus for efficiently treating a high-concentration BOD waste liquid.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that a wastewater containing an organic compound utilizing microorganisms having an oxygen supply capacity of 0.5 kg / m ³ · h-O ₂ or more. It has been found that this can basically be achieved by the aerobic treatment method described above.

[0009] That is, as a method for solving the problem, "a method for aerobically treating wastewater containing an organic compound by using microorganisms to reduce oxygen to 0.5 kg / m ³ · h-O ₂
A wastewater treatment method characterized by being supplied as described above. And a wastewater treatment apparatus having at least a microorganism treatment tank having at least an inlet for treated water and an outlet for treated water and a means for supplying oxygen to the microorganism treatment tank. The oxygen supply capacity of the supply means is 0.5
A wastewater treatment device characterized by a weight of kg / m ³ · h-O ₂ or more. Can basically solve the problem.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be specifically described below. In the present invention, the oxygen supply to the wastewater containing organic matter (hereinafter referred to as organic wastewater) is 0.5 kg / m.
Perform aerobic treatment by performing ³ hO ₂ or more. There are various types of organic wastewater, such as ordinary wastewater and wastewater containing a large amount of a specific substance such as a factory.The treatment is not particularly limited.However, when the wastewater contains a large amount of a specific substance, the specific substance is increased. Microorganisms that degrade with efficiency are dominant, and processing efficiency is often increased. In addition, the BOD concentration is not particularly limited, but is preferably 3,000 ppm or more, more preferably 5,000 ppm or more, and the superiority with other treatment methods is more recognized.

In the case of treating high BOD wastewater, the MLSS in the activated sludge tank (a) becomes extremely high in the ordinary activated sludge method, and sedimentation and separation in the settling tank cannot be performed. Further, the activated sludge method does not consider treating such a load at all, and there is no oxygen supply device corresponding to the BOD load, and there is a problem that (b) oxygen supply is insufficient and the treatment cannot be performed.

On the other hand, in the present invention, the oxygen supply amount in the ordinary activated sludge treatment is at most 0.2 kg / m ³ · h-O _2.
In contrast, oxygen supply of 0.5 kg / m ³ · h-O ₂ or more is performed. For this reason, it is difficult to simply compare with a general activated sludge method, but the problem (b) is solved by providing a device capable of supplying a required amount of oxygen to the BOD. Regarding the problem (a), the present invention does not make the sedimentation / separation of the treated water an essential condition for the design of the apparatus.

In the activated sludge treatment, microorganisms are used to convert the BOD component of the water to be treated into microorganisms, and the microorganisms are subjected to solid-liquid separation to obtain a clear treatment liquid. A sedimentation tank by gravity settling is often used. In activated sludge treatment, sedimentation that affects the quality of treated water is a major point in treatment.

On the other hand, the present invention aims at reducing the load of the high BOD wastewater with high efficiency, so that the sedimentation and separation of the treated water does not matter. The treated water of the present invention is often treated together with other low-BOD wastewater in an activated sludge tank provided at a later stage.However, a method of membrane separation or centrifugal separation can be used, and when sedimentation can be performed, Separation can also be carried out by means such as a settling tank, and there is no particular limitation.

Taking factory wastewater as an example, organic wastewater, which is usually raw water, rarely emits a large amount of high-BOD wastewater in a large number, and a small amount of high-concentration wastewater contains a large amount of low-concentration wastewater. In many cases, the concentration is high.
In such a case, if the treatment by the activated sludge method is performed, the BOD concentration of the entire wastewater is relatively high, so that it is difficult to stably treat the wastewater as it is. Met. When this method is used, the activated sludge tank becomes very large in order to secure the required residence time of the activated sludge tank, and it is difficult to apply the activated sludge tank unless there is a space.

When the present invention is applied to the case of a factory where a small amount of high-concentration wastewater and a large amount of low-concentration wastewater are discharged, a small amount of high-concentration wastewater can be efficiently treated in a space-saving manner by using the present apparatus.
A small amount of treated water having a reduced BOD load is diluted with a large amount of low-concentration wastewater, followed by treatment with activated sludge and sedimentation and separation in a sedimentation tank. Since the present apparatus treats a small amount of high-concentration wastewater that accounts for most of the entire load, the load on the downstream activated sludge tank can be reduced, and a small activated sludge tank can be obtained.

In the activated sludge method, as the treatment capacity is expressed in the form of sludge load, how much BOD per MLSS
Is a management criterion that can be processed. For this reason, a method is employed in which the sludge is returned from the settling tank and the MLSS of the activated sludge tank is maintained at a constant value. However, the amount of oxygen required is represented by the sum of the amount used for decomposing organic substances and the amount used for maintaining and metabolizing microorganisms. In the activated sludge method, the amount used for the maintenance and metabolism of microorganisms cannot be ignored with respect to the amount used for organic matter decomposition. Therefore, because of the increased sludge concentration for organic matter decomposition, the amount of oxygen used for the maintenance and metabolism of microorganisms also increases, and oxygen must be supplied in excess of the amount of oxygen required for decomposition. Was also uneconomical.

On the other hand, in the present invention, the cells generated by the decomposition of organic substances may be returned.
Process with a pass. Therefore, most of the oxygen supply is used for organic matter decomposition, so that the oxygen use efficiency in the organic matter treatment is high and the cost is advantageous.

The oxygen supply apparatus used in the present invention is a method of efficiently supplying oxygen by agitating with a stirring blade while aerating to make air bubbles fine, or supplying oxygen by jetting water and air from a nozzle vigorously. There are an injector method and a method of efficiently supplying oxygen by combining a submersible pump-like device and an air ejection mechanism. There is no particular limitation as long as the oxygen supply capacity is satisfied.

As the gas containing oxygen to be used, air having an oxygen concentration of about 21% may be used, or a gas having an increased oxygen concentration may be supplied to improve the oxygen supply capacity.
Further, a gas having an oxygen concentration of 90% or more may be used, and there is no particular limitation as long as the oxygen supply capacity is satisfied.

As the cells used in the present invention, it is preferable to use, as a dominant species, a bacterium or a bacterium group having a maximum oxygen utilization rate of 0.5 kg / m ³ · hO ₂ or more. The present device is effective when bacterial cells utilize the oxygen supplied by its high oxygen supply capacity to decompose organic substances. For this reason, it is desirable to grasp the maximum oxygen utilization rate of the cells in advance, screen for bacteria having a large maximum oxygen utilization rate, and use them as the dominant species. Except for the dominant species, there is no particular need to consider the oxygen utilization rate.However, there are bacteria that have a useful effect on the dominant species even if the oxygen utilization rate is low, so understand the coexistence relationship when performing the treatment. Preferably.

Basically, the apparatus of the present invention only needs to satisfy the oxygen supply capacity. However, in order to maintain the conditions for efficiently decomposing the treated cells, a temperature controller and a pH controller must be added. Is preferred. In addition, it is preferable that the apparatus be capable of constantly monitoring dissolved oxygen and confirming that there is no shortage of oxygen supply. In addition, it is more preferable that the apparatus be capable of detecting the concentration of dissolved oxygen in the treatment tank and adjusting the oxygen supply capacity in response to the load fluctuation due to the concentration and flow rate of the raw water. At this time, the main method of adjustment is to adjust the flow rate of the oxygen-containing gas or to adjust the capacity when using a supply efficiency improving means such as stirring, but the method is not particularly limited.

The present invention is effective when treating wastewater mainly composed of waste liquid for weight reduction treatment of polyester fabric with caustic soda. The waste liquid is often a high BOD waste liquid,
Conventionally, it has been treated by acid precipitation or a general activated sludge method.
However, the treatment by the activated sludge method has a large load on the wastewater treatment facility due to the high BOD wastewater, and requires a very large activated sludge tank, which poses problems in space and cost. In the present invention, it is possible to treat wastewater mainly composed of a waste liquid of weight loss treatment with caustic soda of a polyester fabric in a compact device by highly efficient oxygen supply,
Although it is advantageous in terms of space and cost, the liquid to be treated is not limited to this.

The apparatus configuration of the present invention will be described with reference to the embodiment of FIG. 1. A raw water supply line 4 and a treated water line 5 are connected to the treatment tank 1, and a predetermined oxygen supply is supplied to the treatment tank 1. It is provided with an oxygen supply means which can be used. In the example of FIG. 1, oxygen is supplied by aeration and agitation. The oxygen-containing gas supplied from the oxygen-containing gas supply line 6 is diffused from the diffuser 3, and the oxygen dissolving efficiency is improved by the stirrer 2 to increase the oxygen dissolving efficiency. Oxygen supply capacity.

FIG. 2 shows an example in which an injector is used as an oxygen supply device and a device for separating cells of treated water is provided. In this example, temperature control is further performed by the temperature measurement control device 14 and the heat exchanger 8, pH control is performed by the pH measurement control device 13 and the pH adjusting agent charging device 10, and circulating water and oxygen are supplied to the injector 9 by the DO measurement control device 15. DO control for changing the supply amount of the contained gas can be performed, and in addition, the inorganic salt (nutrient salt) input device 11 can input a required inorganic salt. In addition, the treated water containing the cells from the treatment tank 1 is removed by the cell separator 12 and discharged from the treated water line 5.

FIG. 3 shows an example in which the present invention is applied to a drainage system in which a small amount of high-BOD wastewater and a large amount of low-BOD wastewater are discharged. The high-BOD wastewater is supplied from a high-concentration raw water supply line 17 to an apparatus 16 of the present invention. The treated water is discharged to the activated sludge tank 19. The activated sludge tank 19 receives the low BOD wastewater from the low-concentration raw water supply line 18 and processes the activated sludge together with the treated water of the apparatus 16 of the present invention. The treated water is introduced into the sedimentation tank 20, separated into solid and liquid, and discharged from the treated water line 5. 2
Reference numeral 1 denotes a line for extracting excess sludge from the sedimentation tank 20;
A sludge return line for returning a part of the sludge in the settling tank 20 to the activated sludge tank 19.

[0027]

(Example 1) Using a device of the present invention having a tank capacity of 1 L, a decomposition treatment experiment was performed using a mixed aqueous solution containing 8 g / L of disodium terephthalate and 3 g / L of ethylene glycol as a main BOD source. went. 167 mL / h of raw water
(Retention 6h), air was supplied by aeration and stirring to supply 1.7 kg / m ³ · h-O ₂ as an oxygen supply amount, and inorganic salts were adjusted so that BOD: N: P became 100: 5: 1. Was added. However, the amount of oxygen supplied at this time was equivalent to the actual amount used, because the oxygen concentration and flow rate of the exhaust gas were measured and the aeration and agitation were adjusted. The same applies to the following Examples and Comparative Examples. The treatment conditions were adjusted so that the temperature was 45 ° C. and the pH was 8.5. The used bacterial group was obtained from soil and used for one month in advance with raw water having the same composition.

The measured BOD of the treated water containing the generated bacterial cells is 4,000 p.m.
pm. In addition, as a result of centrifugation,
D was 300 ppm.

(Example 2) Using the apparatus of the present invention having a tank capacity of 1 L, a decomposition treatment experiment was carried out using a mixed aqueous solution containing 8 g / L of terephthalic acid disodium salt and 3 g / L of ethylene glycol as a main BOD source as raw water. Was. 167 mL of raw water
h (residence 6h), air is supplied by aeration and stirring to supply 1.7 kg / m ³ · h-O ₂ as an oxygen supply amount, and the inorganic salts are adjusted so that BOD: N: P becomes 100: 5: 1. Was added. The treatment conditions were adjusted so that the temperature was 45 ° C. and the pH was 8.5. The used bacterial groups were obtained from soil, and four kinds of bacterial strains useful for raw water decomposition were isolated from those that had been acclimated for one month in raw water having the same composition and used.

The measured BOD of the treated water containing the generated bacterial cells is 4,000 p.
pm. In addition, as a result of centrifugation,
D was 300 ppm, the same result as in the case where the treatment was performed with the four isolated bacteria and in the case where the treatment was not performed, and it was presumed that almost all of the decomposition was performed by the isolated four species.

(Example 3) Using this apparatus having a tank capacity of 1 L, a decomposition treatment experiment was carried out using a mixed aqueous solution containing 8 g / L of terephthalic acid disodium salt and 3 g / L of ethylene glycol as a main BOD source. 167 mL / h of raw water
(Retention 6 h), air was supplied by aeration and stirring to supply 1.7 kg / m ³ · h-O ₂ as an oxygen supply amount, and inorganic salts were adjusted so that BOD: N: P became 100: 5: 1. Was added. The processing conditions of the processing tank were adjusted so that the temperature was 45 ° C. and the pH was 8.5. The used bacterial group was obtained from soil and used for one month in advance with raw water having the same composition. The effluent containing the bacterial cells from this apparatus and the water were mixed and diluted at a ratio of 1: 9, treated in a 25-L activated sludge tank, and subjected to solid-liquid separation in a 6-L sedimentation tank. Return from the settling tank to the activated sludge tank is 420ml / h, 50m
1 / h was extracted as surplus sludge.

The measured BOD of the effluent containing the bacterial cells of the present apparatus was 4.0, while the measured BOD of the raw water was 16,000 ppm.
It was 00 ppm. MLSS of activated sludge tank is 2,000
0 mg / L, and the measured BOD of the effluent was 30 ppm.

(Comparative Example 1) Using an activated sludge tank having a capacity of 25 L and a settling tank having a capacity of 6 L, a mixed aqueous solution containing 8 g / L of disodium terephthalate and 3 g / L of ethylene glycol as a main BOD source was decomposed as raw water. Processing experiments were performed. Raw water was supplied at 167 mL / h and aerated at 5 L / min. When the oxygen supply amount at this time was measured, it was 0.1 kg
/ M ³ · h-O ₂ . The measured BOD of raw water is 1
It was 6,000 ppm.

The aeration tank MLSS rises, and it is impossible to settle and separate in the sedimentation tank. In addition, terephthalic acid disodium salt and ethylene glycol are detected from the effluent containing sludge, and the treatment can be performed sufficiently. Did not.

Apart from solid-liquid separation, treatment at the same concentration as that of the present apparatus could not be performed in the activated sludge tank.

(Comparative Example 2) Using an activated sludge tank having a capacity of 25 L and a sedimentation tank having a capacity of 6 L, a mixed aqueous solution containing 8 g / L of disodium terephthalate and 3 g / L of ethylene glycol as main BOD sources (actually measured BOD 16, 000 ppm)
Raw water (BOD40) diluted 40 times with water
0 ppm), and the decomposition treatment experiment was performed by changing the flow rate of the raw water. The aeration amount was 5 L / min, and the oxygen supply amount at this time was measured to be 0.1 kg / m ³ · h
It was -O _2.

When the raw water flow rate was 1,700 mL / h and the sludge return rate was 0.25, stable operation was possible. The MLSS of the activated sludge tank was 2,000 mg / L, and the BOD of the effluent was 32 ppm. At this time, the processing amount of the mixed aqueous solution containing 8 g / L of terephthalic acid disodium salt and 3 g / L of ethylene glycol before dilution as the main BOD source was 42.5 mL / h.
Met. Compared with Example 2, the throughput of the mixed solution before dilution was about 1/4 in the activated sludge tank having the same capacity.

Therefore, if the same throughput as in Example 1 is to be achieved only by the activated sludge method without using the apparatus of the present invention, the capacity of the activated sludge tank is required to be four times as large as 100 L.

[0039]

According to the present invention, aerobic wastewater treatment, in particular, high-concentration BOD wastewater can be efficiently treated by a compact apparatus with high efficiency.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of a wastewater treatment apparatus containing a microorganism-using organic compound according to the present invention.

FIG. 2 is a flowchart showing another example of the wastewater treatment apparatus containing an organic compound utilizing microorganisms of the present invention.

FIG. 3 is a flowchart showing an example in which the microorganism-using organic compound-containing wastewater treatment apparatus of the present invention is combined with activated sludge treatment.

[Explanation of symbols]

 1: treatment tank 2: stirrer 3: air diffuser 4: raw water supply line 5: treated water line 6: oxygen-containing gas supply line 7: circulation pump 8: heat exchanger 9: oxygen supply device (injector) 10: pH adjustment Agent charging device 11: Inorganic salt (nutrient salt) charging device 12: Cell separation device 13: pH measurement control device 14: Temperature measurement control device 15: DO measurement control device 16: Device of the present invention 17: High concentration raw water supply line 18 : Low concentration raw water supply line 19: Activated sludge tank 20: Settling tank 21: Excess sludge extraction line 22: Sludge return line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D003 AB01 AB19 BA02 CA07 FA02 FA05 4D028 AB00 AC03 BB06 BC24 BD00 CA09 CB02 CC07 CD01 4D029 AA09 AB03 AB06 CC03

Claims (6)

[Claims] 1. A method for aerobically treating wastewater containing an organic compound by utilizing microorganisms, wherein oxygen is added at 0.5 k
A wastewater treatment method characterized by supplying g / m ³ · h-O ₂ or more. 2. The maximum oxygen utilization rate is 0.5 kg / m ³ · h.
Waste water treatment method according to claim 1, wherein utilizing -O ₂ or more fungi or bacterial group as dominant species. 3. The wastewater treatment method according to claim 1, wherein the oxygen supply capacity is adjusted by the concentration of dissolved oxygen in the treatment tank. 4. The wastewater treatment method according to claim 1, wherein wastewater mainly composed of waste liquid of weight reduction treatment of polyester fabric with caustic soda is treated. 5. A wastewater treatment apparatus having a microorganism treatment tank having at least an inlet for treated water and an outlet for treated water, and a wastewater treatment apparatus having an oxygen supply means for the microorganism treatment tank, wherein the oxygen supply means has an oxygen supply capacity of zero. A wastewater treatment device characterized by being at least 0.5 kg / m ³ · h-O ₂ . 6. The wastewater treatment apparatus according to claim 5, further comprising means for adjusting an oxygen supply capacity by a concentration of dissolved oxygen in the treatment tank.