JP2006035221A - Method and apparatus for high-speed biological treatment of organic sewage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for high-speed biological treatment of organic sewage using fine solid particles such as sand. <P>SOLUTION: In the method and the apparatus for high-speed biological treatment of organic sewage, the organic sewage is biologically treated while fluidizing the fine solid particles to each of which a biomembrane is stuck in a biological treatment tank, then the biologically treated water containing the fine solid particles is discharged from the biological treatment tank. At least polymer coagulant is added to the biologically treated water to form coagulated flocs including the fine solid particles, then the flocs are coagulated and settled to obtain the clear treated water and the fine solid particles are recovered from the settled sludge and are returned to the biological treatment tank. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-speed biological treatment method and apparatus for various organic sewage (sewage, industrial wastewater, etc.).

Conventionally, the activated sludge method has been applied as a representative biological treatment of organic sewage.
However, the activated sludge method has a problem that the biological treatment rate is low and the sedimentation rate of activated sludge is small, so that a biological treatment tank and a sedimentation tank are required to have large volumes and installation areas. Moreover, in the operation, activated sludge fine particles flowed out from the sedimentation tank into the treated water depending on the conditions, and the problem of deteriorating the treated water SS and BOD easily occurred.

  A method for biological treatment at high load by adding sand to a biological treatment tank with a sand sedimentation separation part at the top and circulating it through an air lift to attach a biofilm to the surface of the sand. Fluid medium biological treatment methods) were also known. However, this technology is very easy to cause trouble that sand flows out from the biological treatment tank to the treated water, and fine biological particles in the biological treated water are hard to settle, and the treated water SS is more than the treated water SS of the activated sludge method. Due to the problem of getting worse, there were few examples of practical use, and it was now abandoned technology.

In addition, for example, the literature (1) Ultra-high speed coagulation sedimentation treatment using fine sand; 37th Sewerage Research Presentation Summary, p243-245 (2000), (2) JP-A-Gazette; In addition, when coagulating sedimentation treatment of river water, lake water, etc. containing suspended solids, solid particles with a large specific gravity such as sand and magnetite and flocculant are added to the raw water, and the fine solid particles are used as weights. A coagulation sedimentation method is disclosed in which flocs that have been incorporated and have greatly increased sedimentation properties are coagulated and precipitated at a high speed.
However, this technique is merely a technique for accelerating the physicochemical unit operation of coagulating sedimentation of suspended water, and has nothing to do with biological treatment.
In this method, technology is shown in which mineral particles are collected from agglomerated sedimentation sludge incorporating mineral particles such as sand with a cyclone and returned to the raw water subject to agglomeration and reused as floc weights. These mineral particles were used only as the weight of the flocculent floc in the flocculent sedimentation process, and remained in a way that was completely unrelated to biological treatment.

In the biological treatment of organic sewage, the present invention uses a fine solid particle having a specific gravity of 2 or more and a particle size of several hundreds μm or less such as sand, garnet, magnetite, and iron powder in a novel manner. The present invention provides a novel high-speed biological treatment method and apparatus that speeds up both precipitation processes.
According to the present invention, the above-mentioned problems of the conventional fluid medium biological treatment method can be solved.

  That is, the present invention establishes a high-speed biological treatment technology based on a novel technical idea of giving a composite function of “a role as a biofilm-adhering carrier and a role as a mass substance of aggregated floc” to fine solid particles such as sand. did.

The present invention was able to solve the above problems by using the following means.
(1) After biologically treating organic sewage while flowing fine solid particles having a biofilm attached thereto in a biological treatment tank, the biologically treated water containing fine solid particles is discharged from the biological treatment tank. At least a polymer flocculant is added to form a floc floc incorporating fine solid particles, and then coagulated and precipitated to obtain clarified treated water, and the precipitated sludge is separated, and the fine solid particles are recovered from the precipitated sludge. A method for treating organic wastewater, which is returned to the biological treatment tank.
(2) An organic sewage supply pipe, an air blowing pipe, a fine solid particle supply pipe and a biological treatment water discharge pipe are attached, and an air lift unit for flowing fine solid particles having a biofilm attached thereto and the fine solid A biological treatment tank partitioned into a sedimentation separation unit for sedimenting particles, a coagulation tank using a polymer flocculant containing biologically treated water containing fine solid particles, an agglomeration sedimentation apparatus for agglomerated flocs incorporating fine solid particles, and an aggregation precipitation apparatus A high-speed biological treatment apparatus for organic sewage characterized by having a separation device for separating and collecting sludge and fine solid particles from the precipitated sludge from the soil, and a return pipe for sending the collected fine solid particles to a biological treatment tank.

According to the present invention, the following excellent effects are produced.
(A) As a function of fine solid particles such as sand, two functions of a biofilm adhesion carrier in a process of biological treatment by flowing in a state where a biofilm is adhered and a floc weight material in a coagulation sedimentation process were given. Therefore, the microorganism concentration in the biological treatment tank can be increased, the biological reaction rate can be increased, and the floc sedimentation rate of the biological treatment water can be increased. As a result, the required volume and installation area of the biological treatment tank and the sedimentation tank can be greatly reduced, sewage treatment facilities can be installed even in a small site, and construction costs are also reduced. In particular, the areas of the sedimentation separation unit and the coagulation sedimentation apparatus may be small, and may be as small as incomparable with a normal activated sludge sedimentation basin.

(B) Since fine solid particles such as sand are intentionally discharged from the biological treatment tank and used as a floc weight in the coagulation sedimentation process, the medium outflow trouble, which has been a problem of the conventional fluidized medium biological treatment method, It will be fundamentally resolved. Conversely, the fine solids that flowed out can be used for speeding up the precipitation separation.
(C) By coagulating and precipitating the sand-containing biologically treated water, the problem of the conventional medium fluidized biological treatment method that “the treated water SS becomes larger than that of the activated sludge method” can be completely solved.

In order to avoid the complexity of the description below, a case where sand having a fine particle size is used as an example will be described as a representative of fine solid particles.
FIG. 1 is a process diagram showing an embodiment of the high-speed biological treatment method of the present invention.
Organic wastewater (raw water) 1 such as sewage is allowed to flow into the bottom of the biological treatment tank 2 so as to flow upward in the biological treatment tank 2 and air is aerated to perform biological treatment. Fine sand 3 is introduced into the biological treatment tank 2 and flows in the tank by the water flow caused by the upward flow of the raw water 1 and the aeration of the air 4. Reference numeral 5 denotes a hollow cylindrical air lift pipe. When the air 4 is supplied into the pipe, the raw water 1 flows as an upward flow in the pipe and then descends outside the air lift pipe 5 so that the tank 2 A circulation flow of raw water 1 is formed inside. If the operation is continued for a while in this state, the biofilm naturally grows and adheres to the surface of the fine sand 3. If the particle size of the fine sand 3 is excessively large, it is difficult for the biofilm to adhere to it, and if it is excessively small, it is difficult to increase the sedimentation rate in the subsequent coagulation sedimentation step. .

A suitable range for the amount of sand particles 3 added to the biological treatment tank 2 is about 5 to 6% of the volume of the biological treatment tank 2. If it is more than this, the fluidization energy of the sand particles 3 will increase, and if it is too small, the amount of microbial film in the biological treatment tank 2 will decrease, and the biological treatment speed will decrease.
In addition, as a process of carrying out biological treatment while flowing fine solid particles such as fine sand 3 to which a biofilm is attached in the present invention, aerobic biological treatment (BOD removal, nitrification), anaerobic biological denitrification treatment, Any anaerobic treatment can be applied.

  As shown in FIG. 1, the sedimentation separation unit 6 is provided in the outflow part of the biological treatment tank 2, the separation speed of the sedimentation separation unit 6 is set appropriately, and the particle size is small in the input sand 3 from the sedimentation separation unit 6. The three members of the biofilm adhesion sand, suspended microbial particles and SS contained in the raw water are intentionally included in the biologically treated water to be discharged. As for the density | concentration of the sand 3 which flows out into biologically treated water, 2000-4000 mg / liter is suitable. If the amount is too small, the floc sedimentation rate of the aggregated precipitation cannot be increased. Reference numeral 10 denotes a coagulation tank.

  Next, when at least the polymer flocculant 8 (in the case of removing phosphorus and COD, it is preferable to use the inorganic flocculant 9 and the polymer flocculant 8 in combination) is added to the biological treatment water containing fine sand 3 and stirred for several minutes. A floc having a very large sedimentation property incorporating the fine sand 3 is formed. When this is allowed to flow into the coagulating sedimentation device 11, it can be separated by sedimentation at a very high speed of 1 m / min or more, and clear treated water 12 containing no fine sand 3 flows out.

As the type of the organic polymer flocculant 8 (polymer), cationic and amphoteric are preferable when the inorganic flocculant 9 is not used together, and anionic, nonionic and amphoteric polymers are used when the inorganic flocculant 9 is used together. Is suitable. A polymer injection rate of about 0.5 to 3 mg / liter is sufficient.
The appropriate addition rate of the inorganic flocculant 9 varies depending on the quality of the raw water 1 (particularly phosphorus concentration and COD concentration). However, when sewage is treated according to the present invention, the PAC is 100 to 200 mg / liter, and the ferric chloride is used. It is about 50 to 100 mg / liter.

Then, the coagulation sedimentation sludge 13 in which the sand 3 coexists is extracted from the bottom of the coagulation sedimentation apparatus 11 by the pump 14, supplied to the liquid cyclone 15, classified and recovered, and recycled to the biological treatment tank 2.
Even if the liquid cyclone 15 is passed, the biofilm is not completely separated from the fine sand 3. Therefore, returning to the biological treatment tank 2 immediately contributes to removing BOD in the organic wastewater.
When magnetic particles such as magnetite and iron powder are applied as fine solid particles, they can be collected by a magnetic separation device instead of the cyclone 15.

The sludge 16 from which the sand 3 has been removed by the hydrocyclone 15 is supplied to a sludge treatment process such as sludge dewatering treatment.
As another method, biological sludge solubilization treatment such as ozone treatment, ultrasonic treatment, heat treatment, mill crushing treatment, etc. is performed on the sludge 16 from which sand has been removed by the hydrocyclone 15 or the like. After improving the decomposability, when the biological sludge is supplied to the biological treatment tank 2, the biological sludge is biodegraded, so that the amount of surplus biological sludge generated can be greatly reduced.

  When inorganic flocculant 9 is added to agglomerate and remove phosphorus or hardly biodegradable COD in the sand-containing biologically treated water, ozone treatment is most preferable as a solubilizing means. This is because COD components adsorbed and removed by aluminum hydroxide and iron hydroxide floc by addition of the inorganic flocculant 9 are oxidized and improved in biodegradability by ozone treatment. This is because it is removed by biodegradation.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not restrict | limited at all by this Example.

Example 1
Sewage treatment will be described as an example.
Sewage (average water quality: water temperature 22 ° C., pH 7.2, SS 150 mg / liter, BOD 120 mg / liter) was treated according to the flow chart of FIG.
As fine sand particles to be added to the biological treatment tank, sand having a particle size of 20 to 300 μm was used.
The treatment conditions for the biological treatment tank and the coagulation sedimentation step were set as shown in Table 1 below.

Ten days after the start of operation, the sand was taken out from the biological treatment tank and observed under a microscope. As a result, it was observed that the biofilm was attached to the surface of the sand. .
The operation lasted for 3 months. The following Table 2 shows the relationship between the elapsed days after the start of operation and the quality of treated water.

Comparative Example 1
In the case where the polymer flocculant is not added in Example 1, the fine SS flowing out from the biological treatment tank does not settle in the coagulation sedimentation tank, and a large amount flows out into the treated water, and the treated water SS is 85 to 120 mg / liter. The water quality was poor.

It is process drawing of one Example of the high-speed biological treatment method of the organic wastewater of this invention.

Explanation of symbols

1 Organic wastewater (raw water)
2 biological treatment tank 3 fine sand 4 air 5 air lift pipe 6 sedimentation separation part 7 biological treatment water 8 polymer flocculant 9 inorganic flocculant 10 coagulation tank 11 coagulation sedimentation device 12 treated water 13 coagulation sedimentation sludge 14 pump 15 liquid cyclone 16 sludge

Claims (2)

  After biologically treating the organic wastewater while flowing the fine solid particles with the biofilm attached thereto in the biological treatment tank, the biologically treated water containing the fine solid particles is discharged from the biological treatment tank, and at least high After adding a molecular flocculant to form fine flocs incorporating fine solid particles, flocculent sedimentation is performed to obtain clarified treated water, separating the precipitated sludge, collecting the fine solid particles from the precipitated sludge, A method for treating organic sewage, which is returned to a treatment tank.   Organic sewage supply pipe, air blowing pipe, fine solid particle supply pipe and biological treatment water discharge pipe are attached, and the inside of the tank moves the fine solid particles with the biofilm attached, and the fine solid particles settle A biological treatment tank partitioned into a sedimentation separation unit, a coagulation tank using a polymer coagulant containing biologically treated water containing fine solid particles, an agglomeration sedimentation apparatus for agglomeration flocs incorporating fine solid particles, and precipitation from the aggregation precipitation apparatus A high-speed biological treatment apparatus for organic sewage comprising a separation device for separating and collecting sludge and fine solid particles from sludge, and a return pipe for sending the collected fine solid particles to a biological treatment tank.

Images