JP2001179271A - Waste water treatment method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for waste water treatment using a low-cost fluidized bed carrier activated sludge excellent in the adhesiveness and activity of the activated sludge and good in the settling property and dispersibility. SOLUTION: This waste water treatment method uses shredded carbon fiber as a carrier for the waste water treatment using the fluidized bed carrier activated sludge, where the activated sludge is supported on a fine carrier. This device for carrying out the method comprises an activated sludge tank 13, a stirring means 14 for the activated sludge installed in the activated sludge tank 13, a waste water supply pit 11 communicating with the activated sludge tank 13 at the bottom part, and an overflow pit 12 for the treated water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating wastewater with a fluidized bed carrier activated sludge in which activated sludge is carried on a fine carrier.

[0002]

2. Description of the Related Art Conventionally, a method using activated sludge has been widely used as a biological wastewater treatment method. In addition, in order to increase the sedimentation of floc or to increase the concentration of activated sludge and improve the treatment performance. A treatment method using a fluidized bed carrier activated sludge in which activated sludge is supported on a carrier has also been proposed. For example, Japanese Patent Publication No. Hei 6-88031 proposes a method of incorporating granular solids composed of granulated blast furnace slag into activated sludge.

JP-A-5-85085 discloses a batch activated sludge method in which a fluidized bed carrier such as sponge or plastic is placed in an activated sludge reaction tank. JP-A-7-313990 discloses an anaerobic method for activated sludge. Granular carrier A that circulates between the tank and the aerobic tank
And a method for treating sewage using a carrier B which remains in an aerobic tank, wherein particles of gel, sand, activated carbon and the like having a size of 1 to 6 mm are shown as the carrier.

Further, Japanese Patent Application Laid-Open No. 9-75075 discloses that
Method using a clinoptilite of ~ 0.8 mm diameter as a carrier, JP-A-10-165985, various fine carriers,
There has been proposed a wastewater treatment method using a fluidized bed of an artificial granulated activated sludge immobilized carrier in which activated sludge is adhered to silica sand, treated with a paste, and hardened.

[0005] However, these conventional carriers have problems such as insufficient adhesion and activation of activated sludge, insufficient sedimentation, and complicated production of the carrier. There is a need for a method that is good, has good sedimentation, and is inexpensive.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in response to the above-mentioned problems, and has a good adhesion and activity of activated sludge, a good sedimentation property and a low cost. A processing method and apparatus are provided.

[0007]

The method of the present invention is characterized in that a crushed carbon fiber is used as a carrier in a wastewater treatment method using a fluidized bed carrier activated sludge in which activated sludge is carried on a fine carrier. Highly biocompatible, very fine crushed carbon fiber particles provide good adhesion of activated sludge, high activity of activated sludge, and good sedimentation and dispersibility. Fluid bed carrier activated sludge having good properties can be realized. Furthermore, since the carrier can be produced from the end material or the waste material of the carbon fiber molded plate, there is an advantage that the cost is low.

[0008] The diameter of the crushed carbon fiber is 5 microns or more.
Micron or less, and the ratio (L / D) of the length L to the diameter D is
If it is 500 or less, the performance can be further improved, and if the crushed carbon fiber is obtained by crushing or grinding a carbon fiber molded plate obtained by laminating pitch-based carbon fibers, it is easy to manufacture and scraps , Waste materials can be used. Mixing crushed carbon fibers with a volume of 0.1% or more and 3% or less of the final settled volume of the activated sludge can optimize the dispersibility and sedimentation, and intermittently mix the fluidized bed carrier activated sludge anaerobically. In the case of aerial aeration, a large number of facultatively anaerobic denitrifying bacteria are activated and held to perform denitrification, so that denitrification to a low concentration is possible. When the fluidized bed carrier activated sludge is stirred by aeration, aerobic decomposition and stirring of the fluidized bed can be carried out simultaneously.

The apparatus of the present invention has an activated sludge tank, means for stirring the activated sludge provided in the activated sludge tank, a drain supply reservoir communicating with the activated sludge tank at the bottom, and an overflow reservoir for treated water. And
The apparatus for carrying out the method of the present invention can carry out the method of the present invention efficiently, and enables efficient and advanced treatment of wastewater. A filter provided with a filtering means for filtering the treated water can surely perform solid-liquid separation, so that the water quality can be further improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic side sectional view of one embodiment of an apparatus for performing the method of the present invention.

In FIG. 1, reference numeral 10 denotes a fluidized bed carrier activated sludge treatment tank having a square flat cross section, and a waste water supply reservoir 11 and an overflow wall 10b defined by a partition wall 10a communicating at the bottom. An overflow reservoir 12 is defined for the treated water. An activated sludge tank 13 for a fluidized bed carrier is formed between the supply reservoir 11 and the overflow reservoir 12.

A stirring device 14 having a stirring blade 14a for stirring is mounted at the center of the activated sludge tank 13.
In addition, 14b is a rotating shaft, 14c is a thrust bearing, 14d is a drive motor, which is attached to a bracket outside the tank (not shown), the activated sludge in the fluidized bed carrier in the activated sludge tank 13 as shown by arrow A in the figure. Stir and let flow. Numeral 15 denotes two aeration pipes laid on the bottom of the activated sludge tank 13, which are connected to a blower (not shown) provided outside the tank, and start and aeration of the inside of the tank by driving and stopping the blower. Perform a stop.

The activated sludge tank 13 is filled with crushed carbon fibers. This crushed carbon fiber is manufactured by Donac Co., Ltd., and is made of milled carbon fiber (graphitic) obtained by crushing crimped short fiber Donacarbo (registered trademark) of general-purpose pitch-based carbon fiber to 3 mm or less. It is 13 microns in diameter.

As the crushed carbon fiber, the milled carbon fiber thus produced can be used. However, the bulky web made of Donacarb (registered trademark) manufactured by Donac Co., Ltd. and the donacarb (registered trademark) )-Sharpening powder produced by grinding a carbon fiber molded plate obtained by compression molding light wool (referred to as DLW) or crushed powder obtained by crushing the same can be used as crushed carbon fiber. The carbon fiber molded plate is used as a heat insulating material. Since the heat insulating material is used in a required shape and size according to its use, the material and the waste material of the carbon fiber molded plate are generated. Materials and waste materials can be used effectively.

The powdery crushed milled carbon fiber is mixed with a 2% volume ratio with respect to the final settling volume of the activated sludge (the final settling volume in which the activated sludge is settled and the settling volume does not change). Fluidized bed carrier activated sludge. In addition,
As the crushed carbon fiber, the average length is 1 mm or less, and the ratio of the length L to the diameter D, L / D is preferably 500 or less, from the observation of the adhesion and dispersibility of the activated sludge. From, since the length of the crushed carbon fiber is distributed in a certain range,
For use, it is sufficient to sift through particularly large ones. From the viewpoint of activated sludge, that is, the adhesion of microorganisms, the diameter of the carbon fiber is preferably 5 μm or more and 20 μm or less.

Now, the waste water treatment in such an apparatus will be described. Prior to the treatment of the wastewater, the fluidized bed carrier activated sludge is acclimated. In this method, while supplying wastewater to be treated in the same manner as in the usual acclimation of activated sludge, fluidized bed carrier activated sludge in which seed sludge and crushed carbon fiber are mixed is stirred to achieve growth and mixing of activated sludge. Activated sludge adheres using the carbon fiber crushing carrier as a core, and has sedimentation and dispersibility.
When an activated sludge layer 13a (portion indicated by hatching right in the figure) is formed below the activated sludge tank 13, wastewater is continuously supplied to the supply reservoir 11.

The supplied wastewater flows into the activated sludge tank 13 from the lower communication portion of the partition wall 10a, and is stirred and fluidized together with the fluidized bed carrier activated sludge which is stirred by the stirrer 14 and flows as indicated by arrow A in the figure. The nitrate contained in the wastewater is reduced and decomposed by the acclimated facultative anaerobic denitrifying bacteria, and the nitrogen content in the wastewater is removed. The wastewater from which nitrogen is mainly removed and treated is treated as overflow water
The water reaches the overflow reservoir 12 beyond 10b, is drawn out of the tank, and is returned as treated water, or the processing of the next step is performed if necessary. Since the activity of facultative anaerobic denitrifying bacteria decreases when the anaerobic state is continuously maintained, if necessary, air is intermittently supplied from the aeration tube 15 to perform aeration and replenish the hydrogen donor. .

Here, in the method of the present invention, the activated sludge is captured so that the crushed carbon fiber carrier becomes the core of the suspended activated sludge, and the activated sludge layer is a fluidized bed carrier having high sedimentation and high dispersibility. Since 13a is formed, the sludge content is high, the treatment performance is high, and the activity is high. It is not clear why such a good fluidized bed carrier activated sludge is formed,
The material advantage of easy attachment of sludge due to the high biocompatibility of carbon fiber, the shape of fine carbon fiber, bacteria,
The advantage of fineness that promotes the attachment of microorganisms such as protozoa, or the structural advantage that elongated carbon fibers are entangled to promote the attachment of microorganisms and enhance the sedimentation property, and further, different sizes or different L It is also presumed that the presence of a carrier having a / D ratio promotes adhesion of various microorganisms.

In terms of sedimentation, crushed carbon fibers having an apparent specific gravity higher than that of activated sludge are the core of the activated sludge containing no carbon fibers. Good sedimentation. Also,
Speaking of dispersibility, when activated sludge is anaerobically stirred, the activated sludge floc becomes sticky and sticks in the wastewater, but the fluidized bed carrier activated sludge of the present invention is always in a fluffy state, and when it is stirred. It shows good fluidity.

With respect to the dispersibility or apparent density of the activated sludge, in the above embodiment, powder of crushed carbon fiber having a volume of 2% of the final settled volume of the activated sludge was mixed. The final settled volume of the fluidized bed carrier activated sludge increased by twice the volume of the added carrier. This means that the apparent volume of the floc of the activated sludge was increased while the sedimentation property was improved, and it is also presumed that the activated sludge was prevented from sticking. Further, regarding the denitrification performance in the above embodiment, as a result of treating the activated sludge tank 13 with a volume of 6000 cc, an activated sludge concentration MLSS of 3000 mg / l, a wastewater supply amount of 50 cc / min, and a wastewater nitrate concentration of 20 mg / l, The nitrate concentration was 10 mg / l, indicating that the treatment speed was high at a low concentration.

As shown in the above embodiment, the apparatus of the present invention is provided with a supply reservoir 11 communicating with an activated sludge tank 13 as an activated sludge treatment tank 10, so that the fluidized bed carrier activated sludge is provided as shown in the figure. Is sealed in the activated sludge tank 13, and the concentration control of the fluidized bed is easy. In addition, the overflow wall 10b is provided above the lower activated sludge layer 13a, and the treated water overflows from the supernatant 13b at the upper part of the activated sludge tank 13. And a simple structure.

The fluidized state of the activated sludge of the fluidized bed carrier is as follows:
It depends on the shape of the tank, the concentration of the activated sludge, the mixing amount of the crushed carbon fibers as the carrier, or the stirring speed. When the stirring speed is high, the activated sludge receives a shearing force, so that the carrier is easily separated, and when the stirring speed is low, more carriers can be mixed. In addition, the condition of the activated sludge layer described above is determined depending on the stirring speed and the depth of the tank.
When the activated sludge layer is sealed with supernatant water as shown in FIG. 1, it is necessary to optimally set the amount of the carrier mixed, the stirring speed (or the amount of aeration), etc., according to the treatment conditions.

In the apparatus shown in the figure, the separation of the treated water from the activated sludge is based on the so-called sedimentation separation. However, depending on the nature of the drainage, the suspending substance may float. In such a case, solid-liquid separation can be performed by providing an appropriate filter or filtration means such as a microfiltration membrane or a nonwoven fabric membrane. In addition, as a matter of course, a separate sedimentation tank may be provided to perform solid-liquid separation, and the settled sludge may be returned to the activated sludge tank.

It should be noted that the method of the present invention can be carried out not only by the apparatus of this embodiment but also by an apparatus of any other structure and type. Also, the apparatus of the present invention is not limited to the rectangular tank shape of the embodiment, The shape such as a circle (in this case, the supply reservoir, the activated sludge tank and the overflow reservoir are concentrically arranged without being annular) can be appropriately changed, and the stirrer can also be appropriately changed as necessary. It cannot be overemphasized that the form of the form can be used.

As described above, as the crushed carbon fiber used in the present invention, a crushed powder or a ground powder of a carbon fiber molded plate such as Donacarb (registered trademark) milled fiber or Donacarb (registered trademark) felt is preferably used. However, the crushed carbon fiber of the present invention is not limited thereto, and is a crushed powder of carbon fiber, the diameter of which is 5 to 20 microns, the ratio of the length L to the diameter D, L / D is 500 or less, Preferably 200 or less 10 or more, not limited to pitch-based crimp short fibers,
Crushed powder of PAN type long fiber can also be used.

In the above description, the method and apparatus of the present invention are applied to anaerobic stirring (stirring without supplementing air or oxygen), that is, denitrification. It is clear from the properties of activated sludge that the effect is exhibited even when applied to a chemical treatment and a biological oxidative decomposition treatment.

[0027]

According to the method of the present invention, crushed carbon fibers are used as a carrier in a wastewater treatment method using a fluidized bed carrier activated sludge in which activated sludge is carried on a fine carrier. Fluid bed carrier activated sludge with high adhesion of activated sludge, high activity of activated sludge, good sedimentation and dispersibility, high processing performance and good solid-liquid separation due to fine carbon fiber crushed particles. Can be realized. Furthermore, since the carrier can be produced from the end material or the waste material of the carbon fiber molded plate, there is an advantage that the cost is low.

The apparatus of the present invention has an activated sludge tank, means for stirring the activated sludge provided in the activated sludge tank, a drain supply reservoir communicating with the activated sludge tank at the bottom, and an overflow reservoir for treated water. And
Since the method of the present invention can be carried out efficiently, efficient drainage,
Advanced processing becomes possible.

[Brief description of the drawings]

FIG. 1 is a simplified side sectional view of an embodiment of the device of the present invention.

[Explanation of symbols]

 10 Fluidized bed carrier activated sludge treatment tank 11 Supply reservoir 12 Overflow reservoir 13 Activated sludge tank (fluidized bed activated sludge tank) 14 Stirrer 15 Aeration tube

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D003 AA12 AA13 AB02 AB15 BA01 CA07 CA08 DA08 DA15 DA19 EA20 EA22 FA02 FA10 4D027 AA01 AA12 AA16 AB01 AB12 AB16 4D028 AA02 AB00 BB02 BC12 BC18 BC24 BC26 BD08 BB10 BB38 BB BB63

Claims (8)

[Claims] 1. A wastewater treatment method using a fluidized bed carrier activated sludge in which activated sludge is carried on a fine carrier, wherein crushed carbon fibers are used as the carrier. 2. The crushed carbon fiber has a diameter of not less than 5 microns and not more than 20 microns, and has a ratio of length L to diameter D (L / D).
The wastewater treatment method according to claim 1, wherein D) is 500 or less. 3. The wastewater treatment method according to claim 1, wherein the crushed carbon fibers are carbon fibers obtained by crushing or grinding a carbon fiber molded plate formed by laminating pitch-based carbon fibers. 4. The wastewater treatment method according to claim 1, wherein crushed carbon fibers having a volume of 0.1% or more and 3% or less of the final settling volume of the activated sludge are mixed. 5. The wastewater treatment method according to claim 1, wherein the fluidized bed carrier activated sludge is intermittently aerated while being anaerobically stirred. 6. The wastewater treatment method according to claim 1, wherein the fluidized bed carrier activated sludge is stirred by aeration. 7. An activated sludge tank, means for stirring activated sludge provided in the activated sludge tank, a drainage supply reservoir communicating with the activated sludge tank at a bottom portion, and an overflow reservoir for treated water. Terms 1, 2,
A wastewater treatment apparatus, wherein the wastewater treatment method described in 3, 4, 5, or 6 is performed. 8. The wastewater treatment apparatus according to claim 7, further comprising a filtering means for filtering the treated water.