JPH04363194A - Method for purifying organic material-containing waste water - Google Patents

Abstract

PURPOSE:To provide the method for purifying org. material-contg. waste water which is capable of removing the phenol in the org. material-contg. waste water with high efficiency, effectively controlling the quantity of the dissolved oxygen necessary for maintaining the activity of the bacteria for decomposing the org. materials, decreasing the amt. of the excess sludge generated at the time of a purification treatment and lessening the generation of smell. CONSTITUTION:This method for purifying the org. material-contg. waste water consists in supplying the org. material-contg. waste water and air for aeration of 10 to 150(Nm<3> -air/h/m<3> -waste water/h) of the volume of the waste water (m<3> -waste water/h) into a fluidized bed type bioreactor which is packed with biocatalysts formed by including and immobilizing the bacteria for decomposing the org. materials into a polyvinyl alcohol gel at such a ratio as to attain a packing rate of a 5 to 60mol% range, is installed with a diffusion plate having 0.5 to 5mmphi pore diameter and 0.3 to 20% opening rate and has 3 to 9 column height/column diameter, thereby bringing the air for aeration, the org. material- contg. waste water and the biocatalysts into contact with each other.

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 wastewater containing organic substances, particularly phenol-containing wastewater discharged from petroleum refining plants, etc., using a fluidized bed bioreactor filled with a biocatalyst.

0002

BACKGROUND OF THE INVENTION The problems of the conventional activated sludge process are listed below. ■The phenol concentration of phenol-containing wastewater discharged from oil refinery plants, etc. is 40 to 500 ppm, and when treated by the activated sludge method, the concentration of phenol is 90 ppm.
With a removal rate of ~98%, further removal is difficult. ■ Continuous treatment is difficult because of the switching process between the aeration process and the sedimentation separation process of sludge generated by biological reactions. ■A large amount of surplus sludge is generated, which puts a burden on the subsequent treatment process and costs too much if the surplus sludge is treated as industrial waste. ■Processing failures of unknown causes are 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 its normal state. ■Generally, the biological reaction produced by the activated sludge method is relatively slow, and therefore the reaction tank needs to be large, which inevitably increases the installation area. ■ Conventional wastewater treatment using the activated sludge method produces a significant amount of odor, making it difficult to counteract the odor.

Next, these problems will be explained in more detail. First of all, the phenol removal rate is 90-98%, and we cannot expect a higher removal rate because activated sludge (bacteria) is a kind of collection of bacteria (mixed bacteria), and even under certain environments, it can remove 100% of the target material. Only bacterial cells that decompose do not form a bacterial phase, so even if the aeration air, nutrients, contact time (reaction time), etc. are adjusted, the removal rate will not exceed the above-mentioned level. In the activated sludge method, after sufficiently aerating in the aeration process and allowing biological reactions to occur, water flow is temporarily stopped, and the sludge generated by the biological reactions is sedimented and separated.
The supernatant water is then sent to the subsequent treatment process, and the sedimented and separated sludge is treated as industrial waste. In this activated sludge method, surplus sludge generated often enters the subsequent treatment process without being sufficiently sedimented and separated, making it impossible to operate the wastewater treatment equipment. Therefore, continuous processing is difficult and processing capacity is limited. Possible countermeasures to this problem include constructing two identical devices or using a two-stage processing method.
It is clear that this is extremely disadvantageous economically.

[0004] Next, activated sludge (bacteria) often suffers from unsatisfactory treatment for unknown reasons. This is because when the state (properties) of wastewater changes rapidly, that is, when the operating conditions of an oil refinery plant etc. are poor, ammonia nitrogen, sulfur ions (S2-), etc. The activity of activated sludge (bacteria) is significantly inhibited by the substance, and in some cases, almost no phenol is removed.

[0005] When the activity of activated sludge (bacteria) is significantly inhibited and its activity is reduced, it takes time to recover, and as mentioned above, it takes 1 to 6 months, and one cannot help but hope for natural recovery. do not have. Therefore, treatment using the activated sludge method is inevitably limited.

Furthermore, the activity of activated sludge (bacteria) is low, and in order to maintain a constant removal rate including the acclimatization and culture period, the reaction tank must necessarily be large, and the installation area must therefore also be large. . In addition, activated sludge (bacteria) is a typical source of odor when treating wastewater, and especially when an abnormally large amount of sludge is generated for some reason, the odor is particularly noticeable. In the activated sludge method, the treatment is generally carried out in a treatment tank above ground or in a semi-underground treatment tank, which inevitably results in insufficient countermeasures against bad odors.

[0007]

[Problems to be Solved by the Invention] The present invention aims to remove phenol from wastewater containing organic matter with high efficiency, and to effectively control the amount of dissolved oxygen necessary to maintain the activity of microbial cells that decompose organic matter. An object of the present invention is to provide a method for purifying organic matter-containing wastewater that can reduce the amount of surplus sludge generated during purification treatment and reduce the generation of odor.

[0008]

[Means for Solving the Problems] As a result of intensive research into methods for purifying wastewater containing organic matter, the present inventors found that
It was discovered that phenol in organic matter-containing wastewater can be removed with high efficiency by purification using a fluidized bed bioreactor filled with a specific biocatalyst, and based on this knowledge, the present invention was achieved.

That is, in the present invention, a biocatalyst in which bacterial cells that decompose organic substances are entrapping immobilized in a polyvinyl alcohol gel is filled so that the filling rate is in the range of 5 to 60 vol %, and the pore size is in the range of 0.5 to 60 vol %. 5mmφ and open area ratio 0.3~
Organic matter-containing wastewater and the amount of wastewater (m3
- wastewater/h) to 10-150 (Nm3-air/h)
A method for purifying organic matter-containing wastewater is provided by supplying aeration air of /m3-wastewater/h) and bringing the aeration air, organic matter-containing wastewater, and a biocatalyst into contact with each other.

[0010] The organic matter-containing wastewater of the present invention refers to wastewater containing organic matter in various industrial wastewater, domestic wastewater, etc., and for example, COD and BOD concentrations are 10 mg/l or more, preferably 1
It is wastewater containing 00 to 500 mg/l and other oil components. In particular, the present invention can effectively purify wastewater containing 40 to 500 ppm of phenols in addition to the above-mentioned organic substances, specifically, phenol-containing wastewater from fluid catalytic cracking or fluid catalytic cracking product storage tanks of petroleum refinery plants. .

The biocatalyst of the present invention is a catalyst in which bacterial cells that decompose organic substances are entrappingly immobilized on a polyvinyl alcohol gel. For example, the biocatalyst described in JP-A-1-281195 is preferably used. The type of bacterial cells (microorganisms) that decompose organic substances is not particularly limited as long as they can decompose phenols such as phenol and cresol. For example, bacteria, yeast, etc. can be used. Preferably, bacteria having an average diameter of about 1 to 3 μm can be effectively used.

[0012] The polyvinyl alcohol gel (referred to as PVA gel) is not particularly limited. For example, (1) PVA5-2 having a saponification degree of 95 mol% or more and a viscosity average polymerization degree of 1500 or more as described in JP-A-1-281195
5 wt% and (2) polysaccharide or protein 0.01
PVA gel containing ~5 wt% and having a uniform fine network structure with a mesh width of 2 to 3 μm is preferred. The biocatalyst may have any shape. For example, the average diameter is about 1~
A dice or granule shape of 30 mm, preferably 3 to 15 mm is preferred.

[0013] The filling rate of the biocatalyst of the present invention is 5 to 60 vol%, preferably 15 vol% to the volume of the bioreactor.
Fill it to a range of ~50 vol%. When the filling rate is less than 5 vol%, the biocatalyst causes uneven flow within the bioreactor, reducing the efficiency of the microbial reaction. When the filling rate exceeds 60 vol %, the flow of the biocatalyst is significantly restricted, and the biocatalyst may not flow locally, or the aeration air may coalesce, resulting in 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 column height/column diameter of the bioreactor is in the range of 3-9, preferably 5-7. If the column height/column diameter is less than 3, only the biocatalyst in the center of the bioreactor will flow, and the biocatalyst near the bioreactor wall will hardly flow, resulting in slime generation. If the column height/column diameter exceeds 9, the biocatalyst and aeration air will be distributed from the bottom of the bioreactor to the top of the column, making it impossible to obtain a uniform fluidization state. The dispersion plate is provided with a plurality of holes having a diameter of 0.5 to 5 mm, preferably 1.5 to 3.5 mm, and has a porosity of 0.3 to 20%, preferably 3 to 15%. If the pore diameter is less than 0.5 mmφ, clogging occurs due to fine suspended substances contained in the wastewater, and air bubbles coalesce on the surface of the dispersion plate. 8 to 10 if the hole diameter exceeds 5 mmφ
Air bubbles of mmφ are generated, and the amount of dissolved oxygen is significantly reduced. If the porosity is less than 0.3%, the aeration air will be severely restricted, which will not only significantly reduce the amount of dissolved oxygen, but also cause the flow of the biocatalyst to be localized due to fewer pores in the dispersion plate. It gets worse. When the porosity exceeds 20%, the distance between the holes becomes extremely narrow, the coalescence of aeration air bubbles becomes remarkable, and it becomes impossible to maintain the strength when manufacturing the distribution plate.

In the present invention, the amount of aeration air that is brought into contact with the wastewater containing organic matter is the amount of wastewater (m3-wastewater/h).
10 to 150 (Nm3-air/h/m3-wastewater/h), preferably 30 to 130 (Nm3-air/h/
m3-wastewater/h). If the supply amount of aeration air is less than 10 (Nm3-air/h/m3-wastewater/h), the activity of the biocatalyst will decrease significantly and the removal rate of phenols will decrease. The supply amount of air for aeration is 150 (Nm)
3-air/h/m3-wastewater/h), the aeration air becomes excessive and becomes economically disadvantageous. The residence time (HRT) of the organic matter-containing wastewater is preferably 0.5 to 5 hours (hr). LHSV (1/hour) is preferably 0.1 to 2. The contact temperature of organic matter-containing wastewater, aeration air, and biocatalyst is not particularly limited, but is preferably 20 to 40°C.
is within the range of

In the present invention, under the above conditions, the fluidity 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. A method for treating wastewater containing organic matter will be described based on this process flow. 1. Wastewater stripper The treated water (wastewater) is stored in the wastewater tank ■. 2. Wastewater from the wastewater tank (■) and air for aeration are supplied from the bottom of the bioreactor (■), which has been filled with a biocatalyst, through the distribution plate (■). (Pre-fill the bioreactor ■ with wastewater, fill it with a predetermined amount of biocatalyst, and keep it in an aerated state)3. By supplying wastewater and air to the bioreactor (1), the biocatalyst forms a fluid state, and the organic matter in the wastewater is decomposed into CO2 and H2O by the bacteria in the biocatalyst. 4. Wastewater treated by the bacteria 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. The aeration air inside the bioreactor ■ is exhausted from the top of the bioreactor ■.

[0017]

【Example】

"Example 1" Capacity 0.5L (column height = 25cm, column diameter = 6
Treatment experiments were carried out using a bioreactor with a bioreactor (cm). 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 results of treatment of phenol-containing wastewater. This revealed that phenol in wastewater was almost completely removed. Note that this experiment used artificial water as the phenol-containing wastewater, and it is clear that the above treatment conditions are effective in a continuous treatment experiment of about 90 days. The results shown in Figure 1 show that the biocatalyst loading rate is 30.
In the case of vol%, the biocatalyst loading rate is 2.
Similar results were shown in the case of 0.50 vol%. In order to maintain the flow of the biocatalyst in an optimal state, the biocatalyst loading rate is preferably 20 to 30 vol%. Therefore, considering both the phenol removal rate and the flow characteristics, the biocatalyst loading rate is 3.
Approximately 0% is considered best.

"Example 2" Capacity 0.5l (tower height = 25c
Treatment experiments were conducted using a bioreactor with a diameter of 6 cm. The experiment was conducted using raw water that was prepared by adding phenol to phenol-containing wastewater discharged from a petroleum refinery plant to have a phenol concentration of about 300 ppm. The wastewater properties and treatment conditions are shown in the table below.

[0021]

[Table 2]

FIG. 2 shows the results of treatment of phenol-containing wastewater. This revealed that phenol in wastewater was almost completely removed. These are the results of a continuous treatment experiment for about 300 days, and there was almost no decrease in the activity of the biocatalyst, and there was almost no generation of excess sludge. Phenol, COD
, BOD, etc. removal rate is as follows.

[0023]

[Table 3]

[Example 3] Capacity 10 liters (tower height = 60 cm)
A wastewater treatment experiment was conducted using a bioreactor with a diameter of 15 cm. In Examples 1 and 2, a 0.5 liter experimental apparatus was used as a basic experiment, but this time, a 10 liter bioreactor with 20 times the capacity was used, and treatment conditions were investigated using petroleum refining process wastewater as wastewater.

[0025]

[Table 4]

FIG. 3 shows the results of treatment of phenol-containing wastewater. Examining the processing conditions of Examples 1 and 2, HRT: 30
minutes to 2 hours, LHSV (1/hour): 0.5 to 2.0,
Treatment temperature (°C): 20-40, biocatalyst loading rate (vol
%): 20 to 35. In a continuous treatment experiment lasting about one year, no decrease in the activity of the biocatalyst or collapse of the PVA gel carrier was observed, and almost 100% of phenol was removed. Additionally, almost no surplus sludge was generated, making it clear that this treatment method is extremely effective. From the results of this experiment, the optimal processing conditions are:
As shown in the table below.

[0027]

[Table 5]

"Example 4" Capacity 10 liters (tower height = 60 cm
A wastewater treatment experiment was conducted using a bioreactor with a diameter of 15 cm. After 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 a continuous treatment experiment was conducted based on the treatment conditions of Example 3. The properties of phenol-containing wastewater are shown in the table below.

[0029]

[Table 6]

From the results shown in Figure 4, the phenol content was 300 ppm.
Even in the case of wastewater containing a high concentration of phenol, it was revealed that phenol could be almost completely removed by treating it under the operating conditions shown in the table below. As in Example 3, the activity of the biocatalyst decreased even after continuous treatment for about 100 days, and the PVA support
No gel collapse was observed, indicating that this treatment method is extremely effective.

[0031]

[Table 7]

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

[0033]

[Table 8]

[0034] This experiment involved the treatment of phenol-containing wastewater using equipment on a bench plant scale. Figure 5 shows the results of a continuous treatment experiment lasting about 7 months. In this experiment, there was no decrease in the activity of the biocatalyst, no collapse of the PVA gel as a carrier, and it became clear that this treatment method was superior. The optimum processing conditions in this case are shown in the table below.

[0035]

[Table 9]

"Example 6" Phenol concentration is 500 pp
m of phenol-containing wastewater at LHSV=0.6 (HRT
= 1 hour 40 minutes, other processing conditions are the same as in Example 5)
As a result of treatment for about 3 months, phenol was almost completely removed. These results revealed that even a phenol content of 500 ppm can be adequately treated with this treatment method.

Comparative Example 1 In order to prove the effectiveness of this bioreactor system, it was compared with the conventional activated sludge method. The phenol-containing wastewater was prepared by adding phenol to wastewater from a petroleum refinery plant to have a phenol concentration of about 300 ppm.

[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. The results of this experiment show that the bioreactor method has a higher amount of treated water, phenol load, phenol removal rate, and lower phenol removal rate than the activated sludge method.
It has been found that this method is extremely superior in terms of bacterial acclimatization period, generation of excess sludge, etc.

[0040]

[Table 11]

[0041]

[Effect of the invention] 1. The amount of dissolved oxygen required to maintain the activity of bacterial cells (microorganisms) can be effectively controlled. 2. The amount of surplus sludge generated during wastewater treatment can be controlled to 1/5 to 1/10 compared to the conventional activated sludge method. 3. The phenol-degrading bacteria in the biocatalyst are encircled and protected by PVA gel, which is extremely strong, acid- and alkali-resistant, and resistant to chemical and biological reactions. Even if a processing malfunction of unknown cause occurs, the activity can be prevented from decreasing without being directly affected, and the activity can be maintained without replenishing new biocatalyst even if continuous processing operation is performed for a long period of time. 4. Almost 100% of phenols from phenol-containing wastewater discharged from oil refinery plants, etc. can be removed, and the phenol-degrading bacteria in the biocatalyst have extremely strong self-extinguishing power, so excess sludge is extremely rare. Therefore, there is no need to process excess sludge, and there is no need for a sedimentation separation device for suspended matter as in the activated sludge method.Furthermore, there is little odor generation, and odor countermeasures can be easily taken, so it is extremely compact and requires a small installation area. Therefore, it is extremely advantageous economically. 5. While the conventional activated sludge method is a batch method, the method of the present invention can treat wastewater continuously. 6. The activity of the phenol-degrading bacteria in the biocatalyst is extremely high, and when compared under the same conditions, the activity is 5 to 10 times that of the activated sludge method. Therefore, the scale of the treatment equipment can be made compact, and therefore the installation area is 1/3 to 1/2 compared to the activated sludge method.
It can be reduced to

[Brief explanation of the drawing]

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

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

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

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

FIG. 5 shows the results of treatment of phenol-containing wastewater using bench plant scale equipment. ○: Wastewater ●: Treated water

FIG. 6 shows a biprocess probe of the present invention.

[Explanation of symbols]

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

Claims (1)

[Claims] Claim 1: A biocatalyst in which bacterial cells that decompose organic substances are entrappingly immobilized in a polyvinyl alcohol gel is filled so that the filling rate is in the range of 5 to 60 vol%, and the pore size is 0.
．． Organic matter-containing wastewater and the amount of wastewater (m2 - wastewater/h) are placed in a fluidized bed bioreactor with a column height/column diameter of 3 to 9 in which a dispersion plate with a diameter of 5 to 5 mm and a porosity of 0.3 to 20% is installed. 10 to 150 (Nm3-air/h/m3-wastewater/
h) A method for purifying organic matter-containing wastewater, which comprises supplying aeration air and bringing the aeration air, organic matter-containing wastewater, and a biocatalyst into contact with each other.