JP2535267B2 - Purification method of wastewater containing organic substances - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying an organic matter-containing wastewater, particularly a phenol-containing wastewater discharged from a petroleum refining plant, in a fluidized bed bioreactor filled with a biocatalyst.

[0002]

2. Description of the Related Art The problems of treatment by the conventional activated sludge method are listed below. The phenol concentration of the phenol-containing wastewater discharged from petroleum refining plants, etc. is 40 to 500 ppm, which is 90 when treated by the activated sludge method.
With a removal rate of ~ 98%, further removal is difficult. Continuous treatment is difficult due to the switching process between the aeration process and the sedimentation and separation process of sludge generated by biological reaction. Excessive sludge is generated so much that it imposes a burden on the subsequent treatment process and the cost is too high when the excess sludge is treated as industrial waste. A process disorder of unknown cause is likely to occur, and it may take a long time of 1 to 6 months or more to restore the activity of activated sludge (bacteria) to a normal state. In general, the biological reaction by the activated sludge method is relatively slow, which necessitates a large reaction tank, which inevitably requires a large installation area. In the conventional wastewater treatment by the activated sludge method, odor is remarkably generated, and it is difficult to control the odor.

Next, these problems will be described in more detail. First, the phenol removal rate is 90 to 98%, and the removal rate cannot be expected to be higher than this because activated sludge (bacteria) is a group of mixed bacteria (mixed bacteria), and even in a specific environment, 100% target Since only the degrading bacterial cells do not form a bacterial phase, even if the aeration air, nutrients, contact time (reaction time), etc. are adjusted, the above removal rate will not be exceeded. In the activated sludge method, the aeration process is sufficiently aerated, the biological reaction is performed, and then the water flow is temporarily stopped, and the sludge generated by the biological reaction is settled and separated,
After that, the supernatant water is allowed to flow to the subsequent treatment step, and the sludge that has been settled and separated is treated as industrial waste. In this activated sludge method, excess sludge often generated may not be sufficiently settled and separated, and may enter the subsequent treatment step, so that the operation of the wastewater treatment equipment becomes impossible. Therefore, continuous processing is difficult and the processing capacity is limited. As a countermeasure for this, it is possible to construct two identical devices or treat them in a two-stage system.
Clearly, it is extremely economically disadvantageous.

[0004] Next, activated sludge (bacteria) often has a treatment failure state of unknown cause. This is because when the state (property) of the wastewater changes rapidly, that is, when the operating conditions of the oil refining plant and the like are poor, ammonia nitrogen, sulfur ions ( ^S2- ), etc. in the wastewater increase sharply, and therefore Due to these substances, the activity of activated sludge (bacteria) is significantly impaired, and phenol is hardly removed in some cases.

When the activity of activated sludge (bacteria) is remarkably inhibited and the activity is lowered, it takes a long time to recover, and as described above, it takes 1 to 6 months to expect a natural recovery. Absent. Therefore, treatment by the activated sludge method must be limited.

Furthermore, the activity of activated sludge (bacteria) is low, and in order to maintain a constant removal rate including the acclimation / culturing period, the reaction tank must be large and therefore the installation area must be large. . Further, it is a typical source of generating a bad odor in the treatment of wastewater with activated sludge (bacteria), and particularly when a large amount of sludge is generated for some reason, the bad odor is remarkably generated. The activated sludge method is generally installed on the ground in a treatment tank or treated in a semi-underground treatment tank.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides highly efficient removal of phenol in wastewater containing organic substances, and effective control of the amount of dissolved oxygen required for maintaining the activity of cells degrading organic substances. Another object of the present invention is to provide a method for purifying organic matter-containing wastewater capable of reducing the amount of excess sludge generated during purification treatment and reducing the generation of odor.

[0008]

[Means for Solving the Problems] As a result of intensive studies on the method for purifying the organic matter-containing wastewater, the present inventors have found that
It was found that phenol in the organic matter-containing wastewater can be removed with high efficiency by performing purification treatment in a fluidized bed bioreactor filled with a specific biocatalyst, and the present invention could be achieved based on this finding.

That is, the present invention contains a polyvinyl alcohol and a polysaccharide or a protein having a saponification degree of 95 mol% or more and a viscosity average degree of polymerization of 1500 or more, without adhering bacterial cells decomposing organic substances to fine particles. However, it contains a polyvinyl alcohol and a polysaccharide or protein having a saponification degree of 95 mol% or more and a viscosity average degree of polymerization of 1500 or more, which has a uniform fine network structure having a mesh width of 2 to 3 μm, and has a uniform mesh width of 2 to 3 μm. An average diameter of 3 to 100 is entrapped and fixed in a polyvinyl alcohol gel having a fine mesh structure.
A 15 mm dice-like or granular biocatalyst was filled so that the filling rate was in the range of 5 to 60 vol%, and a dispersion plate having a pore diameter of 0.5 to 5 mmφ and an opening rate of 0.3 to 20% was installed. Wastewater containing organic substances and amount of wastewater (m ³ −wastewater / h) in a fluidized bed type bioreactor with a tower height / tower diameter of 3 to 9
To 10 to 150 (Nm ³ −air / h / m ³ −wastewater / h) for continuous supply of aeration air, organic matter- containing wastewater and biocatalyst Provided is a method for purifying wastewater containing organic substances.

The organic matter-containing wastewater of the present invention means various industrial wastes
Wastewater containing organic substances in water, domestic wastewater, etc.
COD and BOD concentration is 10 mg / l or more, preferably 1
Waste water containing 0 to 500 mg / l and other oils
It Particularly in the present invention, phenols are 40 to 500 ppm
It is possible to effectively purify the contained wastewater, specifically, the wastewater containing phenols from the fluid catalytic cracking of the oil refinery plant or the fluid catalytic cracking product storage tank.

The biocatalyst of the present invention is a catalyst in which cells that decompose organic substances are entrapped and immobilized in polyvinyl alcohol gel. For example, the biocatalyst described in JP-A-1-281195 is preferably used. The type of microorganism (microorganism) that decomposes organic substances is not particularly limited as long as it is a microorganism that can decompose phenols such as phenol and cresol. For example, bacteria, yeast and the like can be used. Preferably, bacteria or the like having a particle size of about 1 to 3 μm can be effectively used.

[0012] polyvinyl (referred to as PVA gel) alcohol gel as the described in Japanese Patent Laid-Open No. 1-281195 (1) degree of saponification 95 mol% or more, the viscosity average polymerization degree of 1
A PVA gel containing 500 to 25 wt% of PVA of 5 or more and (2) 0.01 to 5 wt% of polysaccharide or protein, and having a uniform fine network structure with a mesh width of 2 to 3 μm.
Used. The shape of the biocatalyst flat Hitoshi径about 1~30m
m, preferably dice-shaped or granular 3~15mm
Things are used.

The filling rate of the biocatalyst of the present invention is 5 to 60 vol% with respect to the volume of the bioreactor, preferably 15
It is filled so as to be in the range of ˜50 vol%. When the filling rate is less than 5 vol%, the biocatalyst causes a nonuniform flow in the bioreactor, which reduces the efficiency of the microbial reaction. When the filling rate exceeds 60 vol%, the flow of the biocatalyst is significantly restricted, the biocatalyst does not flow locally, or the aeration air is united to cause an unstable flow state.

The bioreactor of the present invention is a fluidized bed type bioreactor in which a dispersion plate is installed at the bottom of the reactor. The tower height / tower diameter of the bioreactor is in the range of 3 to 9, preferably 5 to 7. When the tower height / tower diameter is less than 3, only the biocatalyst in the central portion of the bioreactor flows, and the biocatalyst near the wall surface of the bioreactor hardly flows, so slime is generated. If the tower height / tower diameter exceeds 9, the biocatalyst and the air for aeration are distributed from the bottom to the top of the bioreactor, and a uniform flow state cannot be obtained. The dispersion plate is provided with a plurality of holes having a hole diameter of 0.5 to 5 mmφ, preferably 1.5 to 3.5 mmφ, and the open area ratio is 0.3 to 20%, preferably 3 to 15%. If the pore diameter is less than 0.5 mmφ, the fine floating substances contained in the wastewater cause clogging and coalescence of air bubbles occurs on the surface of the dispersion plate. 8-10 when the hole diameter exceeds 5mmφ
Air bubbles of mmφ are generated, and the amount of dissolved oxygen is significantly reduced.
If the porosity is less than 0.3%, the amount of dissolved oxygen is significantly reduced because the air for aeration is significantly limited, and the pores of the dispersion plate are reduced, so that the flow of the biocatalyst is locally reduced. Get worse. When the open area ratio exceeds 20%, the distance between the holes becomes extremely narrow, the coalescence of air bubbles for aeration is remarkable, and the strength cannot be maintained during the production of the dispersion plate.

The supply amount of the aeration air contacting the organic compound-containing waste water in the present invention is waste water amount (m 3 ^- Wastewater / h)
With respect to 10 to 150 (Nm ³ −air / h / m ³ −waste water / h), preferably 30 to 130 (Nm ³ −air / h /
m ³ −waste water / h). When the supply amount of the aeration air is less than 10 (Nm ³ −air / h / m ³ −waste water / h), the activity of the biocatalyst is remarkably lowered and the removal rate of phenols is lowered. Aeration air supply is 150 (Nm
^{If 3- (} air / h / m ³ −waste water / h) is exceeded, aeration air becomes excessive, which is economically disadvantageous. The retention time (HRT) of the organic matter-containing wastewater is preferably 0.5 to 5 hours (hr). The LHSV (1 / hour) is preferably 0.1 to 2. The contact temperature of the organic matter-containing wastewater, the air for aeration and the biocatalyst is not particularly limited, but is preferably 20 to 40.
It is in the range of ° C.

In the present invention, under the above conditions, the flow state of the biocatalyst is extremely good, there is almost no coalescence of bubbles, and the distribution of bubbles is uniform. The process flow of the bioreactor of the present invention is shown in FIG. Based on this process flow, the method for treating organic matter-containing wastewater will be described. 1. Wastewater Stripper Treated water (wastewater) is stored in a wastewater tank. 2. Waste water from the waste water tank and air for aeration are supplied from the lower part of the bioreactor previously filled with the biocatalyst through the dispersion plate. (Wastewater is pre-filled in the bioreactor, and a predetermined amount of biocatalyst is filled therein to keep it in an aeration state). By supplying wastewater and air to the bioreactor, the biocatalyst forms a fluidized state, and the organic substances in the wastewater are decomposed into CO ₂ and H ₂ O by the bacteria in the biocatalyst. 4. The wastewater treated by the cells in the biocatalyst in the bioreactor flows into the pit, passes through the sand filter, enters the treated water tank, and is then discharged. 5. Aeration air in the bioreactor is exhausted from the top of the bioreactor.

[0017]

EXAMPLES The biocatalyst used in the following examples is methanobac
50 wt% of terium cells is saponified to 99.85 mol.
%, Viscosity average polymerization degree 1750 polyvinyl alcohol
Contains 14.5 wt% and agar powder 0.5 wt%,
Polyvinyl with a uniform fine network structure with a width of 2-3 μm
A support with an average diameter of 8 mm, entrapped and immobilized in alcohol gel.
It is a dolphin-shaped biocatalyst. Also, the bioreactor has holes
Flow with a dispersion plate with a diameter of 3 mm and a porosity of 10%
It is a moving bed type bioreactor. "Example 1" Volume 0.5 l (Tower height = 25 cm, Tower diameter = 6
cm) bioreactor was used to perform processing experiments. The properties and treatment conditions of the phenol-containing wastewater (artificial water) in this case are shown in the table below.

[0018]

[Table 1]

FIG. 1 shows the treatment results of phenol-containing wastewater. According to this, it was revealed that the phenol in the wastewater was almost completely removed. In this experiment, artificial water was used as the phenol-containing wastewater, and it is clear that the above treatment conditions are effective in the continuous treatment experiment for about 90 days. The results shown in FIG. 1 show that the biocatalyst packing rate is 30.
In the case of vol%, the filling rate of biocatalyst is 2 each
Similar results were shown in the case of 0,50 vol%. In order to maintain the flow of the biocatalyst in an optimum state, the biocatalyst packing rate is preferably 20 to 30 vol%. Therefore, considering both the phenol removal rate and the flow characteristics, the biocatalyst packing rate should be 3%.
About 0% is considered to be the best.

Example 2 Volume 0.5 l (Tower height = 25 c
m, tower diameter = 6 cm), a treatment experiment was performed using a bioreactor. An experiment was conducted using wastewater prepared by adding phenol to the phenol-containing wastewater discharged from a petroleum refining plant as raw water to adjust the phenol concentration to about 300 ppm. The state of waste water and the treatment conditions are shown in the table below.

[0021]

[Table 2]

FIG. 2 shows the result of treating the phenol-containing wastewater. According to this, it was revealed that the phenol in the wastewater was almost completely removed. The result of the continuous treatment experiment for about 300 days showed almost no decrease in the activity of the biocatalyst and almost no generation of excess sludge. Phenol, CO
The removal rates of D, BOD, etc. are as follows.

[0023]

[Table 3]

[Example 3] Volume 10 l (tower height = 60 c
m, tower diameter = 15 cm), a wastewater treatment experiment was conducted using a bioreactor. In Examples 1 and 2, a 0.5 l experimental apparatus was used as a basic experiment, but this time, the treatment conditions were examined using a petroleum refining process waste water as a waste water in a 10 l bioreactor having a capacity of 20 times.

[0025]

[Table 4]

FIG. 3 shows the treatment results of phenol-containing wastewater. Examining the processing conditions of Examples 1 and 2, HRT: 30
Minute to 2 hours, LHSV (1 / hour): 0.5 to 2.0,
Treatment temperature (° C): 20-40, biocatalyst filling rate (vol)
%): It is the result of conducting the experiment at 20-35. In a continuous treatment experiment for about 1 year, the activity of the biocatalyst was not reduced, the PVA gel as the carrier was not disintegrated at all, and almost 100% of the phenol could be removed. In addition, it was revealed that the surplus sludge was hardly generated and this treatment method was very effective. From the results of this experiment, the optimum processing conditions are
It is as shown in the table below.

[0027]

[Table 5]

Example 4 Volume 10 l (Tower height = 60 c
m, tower diameter = 15 cm), a wastewater treatment experiment was conducted using a bioreactor. Examining the results of Example 3, phenol was added to petroleum refining process wastewater as raw water to adjust the phenol concentration to about 300 ppm, and Example 3 was used.
A continuous treatment experiment was carried out based on the treatment conditions. The properties of phenol-containing wastewater are shown in the table below.

[0029]

[Table 6]

From the results shown in FIG. 4, the phenol content is 300 ppm.
Even in the case of wastewater containing high-concentration phenol, it was revealed that the phenol can be removed almost completely by treating it under the operating conditions shown in the table below. As in the case of Example 3, even after continuous treatment for about 100 days, the activity of the biocatalyst was reduced and PVA as the carrier was used.
No disintegration of the gel was observed and it was revealed that this treatment method was very effective.

[0031]

[Table 7]

[Embodiment 5] Capacity 200 l (Tower height = 300)
cm, tower diameter = 30 cm) using a bioreactor
A wastewater treatment experiment was conducted. Considering the results of Example 4,
Phenol was added to the petroleum refining process wastewater as raw water to adjust the phenol concentration to about 300 ppm, and a continuous treatment experiment was conducted with reference to the treatment conditions of Example 4. The properties of phenol-containing wastewater are shown in the table below.

[0033]

[Table 8]

This experiment is a treatment of phenol-containing wastewater using a bench plant scale apparatus, and the results of a continuous treatment experiment for about 7 months are shown in FIG. Also in this experiment, the activity of the biocatalyst was not decreased, the PVA gel as the carrier was not collapsed, and it was revealed that the present treatment method is excellent. The optimum processing conditions in this case are as shown in the table below.

[0035]

[Table 9]

Example 6 Phenol concentration is 500 pp
m phenol-containing wastewater, LHSV = 0.6 (HRT
= 1 hour 40 minutes, other processing conditions are the same as in Example 5)
As a result of the treatment for about 3 months, the phenol could be removed almost completely. From this result, it was clarified that this treatment method can sufficiently cope with the case where the phenol content is 500 ppm.

Comparative Example 1 In order to prove the effectiveness of this bioreactor system, a comparison was made with the conventional activated sludge process. As the phenol-containing wastewater, wastewater prepared by adding phenol to wastewater of a petroleum refining plant to prepare a phenol concentration of about 300 ppm was used.

[0038]

[Table 10]

When the bioreactor method and the activated sludge method were compared under the above treatment conditions, the results shown in the following table were obtained.
From the results of this experiment, compared with the activated sludge method, the amount of treated water, phenol load, phenol removal rate,
It was revealed that it is extremely excellent in terms of acclimation of bacterial cells and generation of excess sludge.

[0040]

[Table 11]

[0041]

Effect of the Invention It is possible to effectively control the amount of dissolved oxygen required for maintaining the activity of bacterial cells (microorganisms). 2. The amount of excess sludge generated during wastewater treatment can be controlled to 1/5 to 1/10 of that of the conventional activated sludge method. 3. Phenol-decomposing bacteria in the biocatalyst are in a state of being protected by being comprehensively immobilized on a carrier called PVA gel, which is extremely strong in acid resistance, alkali resistance, and resistant to chemical reactions and biological reactions. Even if a treatment disorder of unknown cause occurs, the activity is not directly affected and a decrease in activity can be prevented, and the activity can be maintained without supplementing with a new biocatalyst even if a long-term continuous treatment operation is performed. 4. Almost 100% of phenols in phenol-containing wastewater discharged from petroleum refining plants can be removed. Phenol-degrading bacteria in biocatalysts have extremely strong self-digestion power, and therefore, excessive sludge generation is extremely low. Therefore, it does not require excess sludge treatment and does not require a sedimentation and separation device for suspended matter, such as the activated sludge method. Furthermore, it does not generate odors and can easily control odors. Therefore, it is economically extremely advantageous. 5. The activated sludge method which is a conventional method is a batch method, whereas the method of the present invention can continuously treat wastewater. 6. The activity of the phenol-decomposing bacteria in the biocatalyst is extremely high, and the activity is 5 to 10 times that of the activated sludge method when compared under the same conditions. Therefore, the scale of the treatment equipment can be made compact, and therefore the installation area is 1/3 to 1 / compared with the activated sludge method.
It can be reduced to 2.

[Brief description of drawings]

1 shows the treatment results of phenol-containing wastewater obtained according to Example 1. FIG. ○: Waste water ●: Treated water

2 shows the treatment results of phenol-containing wastewater obtained according to Example 2. FIG. ○: Waste water ●: Treated water

FIG. 3 shows the treatment results of phenol-containing wastewater obtained according to Example 3. ○: Waste water ●: Treated water

FIG. 4 shows the results obtained according to Example 4.

FIG. 5 shows the results of treating phenol-containing wastewater using a bench plant scale device. ○: Waste water ●: Treated water

FIG. 6 shows a bioprocess flow of the present invention.

[Explanation of symbols]

 1 Waste water tank 2 Bioreactor 3 Dispersion plate 4 Pit 5 Sand filter 6 Treated water tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroo Takeda 2-228-1031 Kosugicho, Nakahara-ku, Kawasaki-shi, Kanagawa (56) References JP-A-63-158194 (JP, A) JP-A-1-281195 ( JP, A) JP 60-197295 (JP, A)

Claims (1)

(57) [Claims] 1. Micro- organisms that decompose microorganisms that decompose organic substances
95 mol of a saponification degree of 95 mol% or more, a polyvinyl alcohol having a viscosity average degree of polymerization of 1500 or more and a polysaccharide or a protein, and a uniform fine network structure having a mesh width of 2 to 3 μm without adhering. %that's all,
Containing polyvinyl alcohol and a polysaccharide or protein with a viscosity average degree of polymerization of 1500 or more, and a mesh width of 2-3
Packing rate of dice-like or granular biocatalyst having an average diameter of 3 to 15 mm, which is entrapped and fixed in polyvinyl alcohol gel having a uniform fine network structure of μm, is 5 to 60 vol%.
Tower height / hole size of 0.5 to 5 mmφ and a porosity of 0.3 to 20%.
In a fluidized bed type bioreactor with a tower diameter of 3 to 9, 10 to 15 with respect to organic matter- containing wastewater and wastewater amount (m ³ −wastewater / h)
0 (Nm ³ −air / h / m ³ −wastewater / h) for supplying aeration air continuously, and contacting aeration air, organic matter- containing wastewater and biocatalyst, organic matter-containing wastewater Purification method.