JPS63252595A - Aerobic biological treatment method - Google Patents

Abstract

PURPOSE:To efficiently treat the scum floating on the surface of water to be treated while aerobic biological treatment is performed by efficiently supplying oxygen to the water to be treated. CONSTITUTION:A gas-liquid mixing apparatus consists of a jet stream generator 1 and a flow distributor 2. The jet stream generator 1 has the liquid inlet 3 communicating with the interior of the jet stream generator through an internal nozzle 5. The flow distributor 3 is composed of a pipe opened at both ends thereof and the inner diameter thereof continuously reduces from an inlet 7 to a discharge port 8. The scum floating to the surface of the water to be treated of a biological treatment tank is collected in the gas-liquid mixing apparatus and supplied along with the water to be treated. Substances such as microbes, org. pollutants or the like are ground into fine flocks and subjected to aerobic biological treatment by extending the stagnation time thereof in the water to be treated. By this method, treatment efficiency can be enhanced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an aerobic biological treatment method for treating organic wastewater, treating various liquid media in biotechnology, etc. The present invention relates to a method for treating scum floating on the surface of water to be treated while efficiently supplying oxygen and performing aerobic biological treatment.

(Prior art) When treating water such as wastewater containing organic pollutants (organic wastewater) with aerobic organisms, it is necessary to supply oxygen as uniformly and at a high concentration to the water body as possible. Needs to be dissolved. If the supply of oxygen is insufficient or uneven, aerobic biological treatment cannot be carried out smoothly, and problems such as the proliferation of unintended anaerobic organisms occur.

Conventionally, a method of supplying gas such as oxygen to water to be treated (
Various methods are known as aeration methods, including the use of aeration pipes, mechanical aeration, bubble injection, and underwater ejector methods, but they have low efficiency in dissolving oxygen, etc., and do not provide uniform aeration. There were problems such as not being able to do so.

On the other hand, when biologically treating organic wastewater, at the start-up of biological treatment or when the load fluctuates rapidly, a film-like substance with high viscosity and large air bubbles, generally called the biosurfactant phenomenon, is formed. Air-containing scum may form. In particular, it often occurs in food processing plant wastewater, pharmaceutical processing plant wastewater, dyeing factory wastewater, etc. that contain high concentrations of organic pollutants. This air-containing scum floats on the surface of the water to be treated, but since it has not yet undergone sufficient biological treatment, if left untreated, it will rot, emit a foul odor, and the quality of the water in the biological treatment tank will deteriorate dramatically. Furthermore, since it is difficult to supply oxygen into the scum, anaerobic bacteria also proliferate within the scum, resulting in a mixture of aerobic and anaerobic bacteria that becomes extremely sticky and difficult to treat.

[Problem that the invention seeks to solve]

Conventionally, when such scum was generated, it was collected from the surface of the water to be treated in a biological treatment tank and treated separately by burning or the like, but this treatment was not easy.

An object of the present invention is to provide an aerobic biological treatment method that can efficiently treat such scum in a biological treatment process even if it is generated.

[Means for solving problems]

That is, the aerobic biological treatment method of the present invention includes a jet generator that jets a mixed state of gas and liquid from a nozzle, and a tubular jet generator that jets a bubble-containing flow jetted from the nozzle and mixes it with surrounding water and discharges it from a discharge port. A gas-liquid mixing device comprising a rectifier, the jet generator having a liquid inlet, a gas inlet, an external nozzle, and an internal nozzle, the liquid inlet communicating with the inside of the jet generator via the internal nozzle. The rectifier has a tube shape in which the inner diameter decreases at least halfway from the inlet to the discharge port, and the external nozzle and the rectifier are substantially coaxial, and the tip of the external nozzle is located near the inlet of the rectifier. A gas-liquid mixing device arranged such that The scum floating on the surface of the treated water is collected, and the scum is supplied to a jet generator along with the water to be treated, mixed with gas containing oxygen, and atomized as a bubble-containing stream that is circulated into the aquarium. This is a method of aerobic biological treatment of treated water.

Note that aerobic biological treatment as used in the present invention refers to treatment that uses aerobic bacteria for the purpose of decomposing organic substances in water to be treated.

(Preferred mode for carrying out the invention) First, a gas-liquid mixing device used in the present invention will be explained with reference to the drawings. Figures 1 and 2 are schematic sectional views showing an example of a gas-liquid mixing device. Figure 1 shows a rectifier made of a single pipe, and Figure 2 shows a rectifier made of a double pipe. It shows.

This gas-liquid mixing device is composed of a jet generator 1 and a rectifier 2. The jet generator 1 includes a liquid inlet 3, a gas inlet 4,
It has an internal nozzle 5 and an external nozzle 6, with the liquid inlet 3 communicating with the interior of the jet generator via the internal nozzle 5.

Each nozzle 5.6 may be in the shape of a thin straight tube, but it is preferable that the diameter of the nozzle continuously changes so that the tip of the nozzle becomes narrower. Further, in the figure, the internal nozzle 5 and the external nozzle 6 are arranged in a straight line with the same orientation, but it is not necessary to arrange them in this way. may be placed.

The rectifier 2 is made of a tube with both ends open, and the inner diameter is the largest at the inlet lower part, and the inner diameter decreases continuously from the man lower part to at least halfway towards the discharge port 8. That is, the inner diameter may decrease continuously from the entrance lower part to the discharge port 8, or the inner diameter may continuously decrease halfway. In this case, if the inner diameter decreases continuously up to the middle, the tip may be straight, or conversely, the inner diameter may tend to increase again at the tip. The length of the part where the inner diameter continuously decreases from the inlet lower is preferably 1/4 or more of the total length of the tubular rectifier, and is 1/2 to 1/2.
More preferably, it is about 3.

In this gas-liquid mixing device, when the inner diameter of the external nozzle 3 of the jet generator 1 is A, and the inner diameter of the part with the smallest inner diameter of the rectifier 2 is B, A/B is in the range of 0.1 to 0.5. The total length of the rectifier 2 is preferably in the range of 20A to 100A with respect to the inner diameter A of the external nozzle.

When the value of A/B is less than 0.1, the flow rate of the bubble-containing flow discharged from the discharge 118 becomes slow, the suction force of the surrounding water is weakened, the bubble dispersion effect disappears, and the diameter of the bubbles increases. Cheap. Moreover, when it exceeds 0.5, the vortex inside the rectifier 2 increases, the same bubble collision occurs, and the bubbles tend to become large.

When the total length is less than 20A, the role of the rectifier 2 is to mix and disperse air bubbles with surrounding water to prevent bubbles from forming, and to eliminate local peaks of dissolved oxygen to increase oxygen dissolution efficiency. You won't be able to perform to your full potential. Also, L is 10O
If the length exceeds A and becomes longer than necessary, the scum is likely to contain bubbles again or the crushed scum will re-agglomerate, and the flow rate of the bubble-containing stream discharged from the discharge port 8 will become low.

Furthermore, it is extremely important that the rectifier 2 has a tube shape in which the inner diameter continuously decreases at least halfway from the inlet lower to the discharge port 8. Even if the mixing ratio of /gas is increased to 172 to 1/3, bubbles do not occur and the bubbles can be maintained in a fine state. Normally, the tapered part (inner diameter gradually decreasing part) is 172 to 1/4 of the total length, preferably l/
It is preferable that the inner diameter of the lower inlet of the rectifier 2 is about 1.4 to 4.0 times the inner diameter B of the discharge port 8.

The positional relationship between the jet generator 1 and the rectifier 2 is as follows:
and the rectifier 2 are located substantially coaxially, and the tip of the external nozzle is located near the lower part of the rectifier. The tip of the external nozzle does not need to be inserted deep into the rectifier; it is only necessary that the air bubble-containing flow injected from the external nozzle is received by the rectifier without omission. In extreme cases, the tip of the external nozzle may be located slightly outside the rectifier inlet lower, but normally
It is appropriate to arrange it so that it is located slightly inside the rectifier from the core.

FIG. 2 is a schematic cross-sectional view showing another example of the gas-liquid mixing device, in which the tubular rectifier 2 has a double-tubular shape with an inner tube 9 built therein. In this case, the rectifier body (outer tube)
2 has the above-mentioned shape, and the inner tube 9 also has the outer tube 2.
It consists of a tube with a similar shape open at both ends. The outer tube 2 and the inner tube 9 are arranged substantially coaxially, and the lower entrance of the outer tube and the inlet IO of the inner tube are located substantially aligned as shown. Also, the inner diameter of the part with the smallest inner diameter of the inner tube is C
When C/B is 0.5 to 0.75, the total length of the inner tube 9 is shorter than the total length of the rectifier body, and A is 10 to 5.
Preferably, it is 0 times. When such a rectifier having a double tube structure is used, compared to the rectifier shown in FIG. 1, there is an advantage that the ejection distance of the bubble-containing flow can be extended further.

These gas-liquid mixing devices can uniformly supply a large amount of fine air bubbles to the water to be treated without creating bubbles, making it possible to achieve extremely high oxygen dissolution efficiency. The volume ratio of I/2 to 173
It has the feature that the dispersibility of air bubbles into water does not decrease even if it is increased to a certain degree.

The method of the present invention uses the gas-liquid mixing device described in section E to efficiently supply oxygen to the water to be treated and carry out aerobic biological treatment, and at the same time, it is possible to carry out aerobic biological treatment by efficiently supplying oxygen to the water to be treated. The scum is collected and fed to the gas-liquid mixing device along with the water to be treated.

In other words, the scum is forcibly mixed with the water to be treated and a gas containing oxygen, and at the same time, high shear force is used to microorganize the scum, which is a mixture of microorganisms, organic pollutants, and coarse air bubbles, and the organic pollutants in the water to be treated. Aerobic biological treatment is carried out by crushing the flocs into flocs, placing them in a bubble-containing stream, dispersing them over as wide a range as possible in the treatment tank, and extending the residence time in the water to be treated.

When carrying out the method of the present invention, a gas containing oxygen, such as air or oxygen-enriched air, is supplied to the jet generator 1 to form a bubble-containing flow. The mixing ratio of water)/gas is 172 to 1 by volume.
It is preferable to set the temperature within the range of about 73 because a large amount of fine air bubbles can be diffused into the processing tank.

Further, in the method of the present invention, a mixed liquid of water to be treated and scum floating on the surface of the water to be treated is used as the liquid to be supplied to the gas-liquid mixing device. The water to be treated may be used by circulating the water in the treatment tank, or the undiluted solution supplied to the treatment tank may be used. Of course, the water to be treated may be diluted with clean water and then supplied. However, when the water to be treated in the aquarium is circulated and supplied to the gas-liquid mixing device, the flocs formed by agglomeration of aerobic organisms in the aquarium are atomized in the gas-liquid mixing device and returned to the aquarium. This is preferable because biological treatment can be carried out more efficiently.

The scum floating on the surface of the water to be treated in the biological treatment tank has considerable buoyancy due to coarse air bubbles, so even if you try to collect this scum and supply it to the gas-liquid mixing device along with the water to be treated, it will not get caught in the pump. It may not be included. In such a case, the coarse bubbles may be crushed or pushed into the water to be treated by applying pressure that overcomes buoyancy, and then sent to the gas-liquid mixing device using a pump or the like.

Methods of applying mechanical shearing force to destroy coarse scum bubbles and forcing them into the water to be treated include: ■ Water jet method (using a spray gun, etc.) ■ Air jet method (using an air jet nozzle) ■ Hammering method Methods such as (using a blade or plate) ■ Stirring method (using a stirrer) ■ Kneading method (using a screw type kneader) ■ Crushing method (using an impeller rotating above the water surface) can be used.

Also, after destroying the coarse bubbles of scum in this way,
If the scum is mixed with the water to be treated using a so-called static mixer, which has a baffle plate or a guide plate for changing the flow direction in the pipe, before being supplied to the gas-liquid mixing device, the air bubbles in the scum can be further broken down. can.

According to the method of the present invention, scum is supplied together with the water to be treated to a gas-liquid mixing device, mixed with oxygen-containing gas, and the scum crushed into fine flocs is placed on a bubble-containing flow to spread as widely as possible in the treatment tank. By dispersing, the following biological treatment proceeds.

(1) By feeding the microorganisms in the scum that are suitable for biological treatment to the gas-liquid mixing device, they are differentiated as much as possible and the number of microorganisms increases, reducing the opportunity and contact area for contact with pollutants and dissolved oxygen. This increases the efficiency of biological treatment.

(2) In addition to the components contained in raw organic wastewater, pollutant components include components treated in biological treatment tanks, and some of them remain as scum and float on the surface of the water to be treated. Some of them tend to be anaerobic, and all of them are differentiated and their number increases, which increases the opportunity for contact with microorganisms and dissolved oxygen and increases the contact area, resulting in higher biological treatment efficiency.

In addition, in the aerobic biological treatment method of the present invention, in order to make the inside of the aquarium a suitable environment for biological treatment, conventionally known methods such as pH adjustment, temperature adjustment, removal of toxic substances, removal of excess oil and fat, and addition of nutrients are carried out. It is recommended to perform various operations as appropriate.

The method of the present invention can be applied to natural or artificial organic wastewater such as industrial wastewater from the food, chemical, steel, and oil industries, industrial wastewater discharged from buildings, schools, hospitals, etc., and so-called sewage discharged from cities and rural areas. Not only can it be used to treat organic wastewater containing compounds, but it can also be applied to aerobic biological treatment in the treatment of various liquid media in biotechnology.

〔Effect of the invention〕

According to the method of the present invention, there is no need to separately treat the scum floating on the surface of the water to be treated by burning or the like. In addition, air can be diffused into the biological treatment tank extremely efficiently, and the flocs of aerobic organisms in the water to be treated are also differentiated, so the generation of scum is reduced, and opportunities for scum treatment are also substantially reduced.

〔Example〕

Hereinafter, the method for treating organic wastewater of the present invention will be explained in more detail according to Examples.

Example 1 Wastewater from washing bottles of milk, fruit juice, and coffee milk was treated using the wastewater treatment equipment outlined in FIG. The BOD of this organic wastewater is 800-1400 ppm, S
S fluctuated wildly in the range of 66-190 ppn+.

The biological treatment tank 12 has an effective water depth of 62001111 and a length of 1
The tank is 2.5m long and 2.2m wide, with a first tank at the bottom.
A gas-liquid mixing device 16 having the structure shown in the figure was installed. In this gas-liquid mixing device 13, the inner diameter of the nozzle of the jet generator is 50 m.
m, total length of rectifier 2000mm, straight pipe length 1000mm
mm, the inner diameter of the inlet was 240 mm, and the inner diameter of the outlet was 100 mm. The water to be treated in the water tank 12 is taken in as a liquid from the water intake port 24 to the gas-liquid mixing device 13, and the water is supplied by the pump 17 at a discharge water rate of 0.7 g/min and a pressure of 2.1 kg/c, and the gas is The air is supplied by the gas supply line 22 at 1.4 Nrr? The bubble-containing stream was continuously discharged by feeding at a rate of 1/min. There was almost no escape of air bubbles due to bubble inclusion, and good dispersion of fine air bubbles into the aquarium was observed.

When biological treatment was continued by flowing a bubble-containing stream in this biological treatment tank 12, a considerable amount of coarse scum floated to the surface of the water to be treated after 6 hours. Therefore, the scum schema 14 is activated to collect the scum on the surface of the water to be treated into the scum tray 15, and the scum is mixed with the water to be treated at a ratio of 1:1 (weight ratio) through the scum pressure pump 12, and then air-filled. When the biological treatment was continued by supplying it to the liquid mixing device 12,
After 1.5 hours, the scum on the surface of the water to be treated completely disappeared, and after another 6 hours, the R of the organic wastewater in the biological treatment tank 12 disappeared.
The OD decreased to 19 ppm, and extremely high quality treated water was obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing an example of a gas-liquid mixing device used in the method of the present invention, and FIG. 3 is a schematic cross-sectional view of a biological treatment tank for carrying out the method of the present invention. be.

Claims (1)

[Scope of Claims] 1) It has a jet generator that jets out a mixture of gas and liquid from a nozzle, and a tubular rectifier that mixes the bubble-containing flow jetted from the nozzle with surrounding water and discharges it from a discharge port. A gas-liquid mixing device comprising: a jet generator having a liquid inlet, a gas inlet, an external nozzle, and an internal nozzle, the liquid inlet communicating with the inside of the jet generator via the internal nozzle; The rectifier has a tube shape in which the inner diameter decreases at least halfway from the inlet to the discharge port, and the outer nozzle and the rectifier are arranged substantially coaxially and the tip of the outer nozzle is located near the inlet of the rectifier. A gas-liquid mixing device made of Collect the scum that has floated to the surface, feed this scum to a jet generator together with the water to be treated, mix it with gas containing oxygen, atomize it as a bubble-containing stream, and circulate it into the aquarium to improve the water to be treated in the aquarium. How to treat temperamental organisms. 2) The inner diameter of the external nozzle is A, and the inner diameter of the rectifier outlet is B.
The method according to claim 1, which uses a gas-liquid mixing device in which A/B is 0.1 to 0.5 and the total length L of the rectifier is 20A to 100A.