JPH0210719B2 - - Google Patents

Description

Detailed Description of the Invention The present invention involves suspending a carrier for attaching microorganisms in a tank, and circulating and flowing the carrier in the tank while performing gas agitation using an air lift tube installed in the tank. This invention relates to a fluidized bed biological treatment device for wastewater.

Recently, various biofilm-based sewage treatment systems have been put into practical use, employing tube catalytic oxidation, rotating disk method, granular solid fluidized bed method, etc., to eliminate the bulking phenomenon caused by the activated sludge method and the complexity of maintenance. has been done. Among these, microorganisms are attached to the surface of granular carriers suspended in a tank, and the carriers are circulated and flowed in the tank while performing gas agitation via an air lift pipe installed in the tank, and brought into contact with wastewater. The fluidized bed method, which removes sludge substances from wastewater, has a much larger surface area of the carrier for microorganisms to attach to than other biofilm methods, so it is possible to retain a large amount of microorganisms in the tank. It is attracting attention because it has many advantages, such as the fact that the carrier circulates in the tank and does not cause problems such as clogging or partial anaerobic formation.

In this type of fluidized bed method, sand, anthracite, activated carbon, zeolite, plastic balls, etc. are used as carriers for microbial attachment, and particles with specific gravity and particles suitable for smooth circulation and flow in the tank are used. A granular solid with a certain diameter is used, but sand is usually used due to its price and availability.

In a fluidized bed apparatus using such a fluidized bed method, as shown in the first illustrated example, a carrier 2 for attaching microorganisms is placed in a tank 1.
The air lift pipe 3 installed in the tank 1 has an air introduction pipe 4 connected to its lower part, and due to the air lift action of the air blown into the air lift pipe 3, water is removed from the raw water introduction pipe 5. The carrier 2 is circulating in and out of the air lift pipe 3 together with the introduced raw water.

The inside of the tank 1 is partially or entirely partitioned by a partition wall 6 whose upper end is above the water surface and whose lower end is below the water surface and is separated from the tank bottom.
A separation section 7 is formed, and while a part of the suspension in the tank 1 rises through this separation section 7, it separates the carrier 2 and is taken out as effluent water 9 from an upper outflow section 8. It's getting old.

In this conventional fluidized bed apparatus, the effluent water 9 is sent to a coagulation-sedimentation device, a sand filtration device, etc. for post-treatment, and is subjected to treatments such as removing SS, BOD, and COD from the effluent water 9, and finally It becomes treated water. However, as the treatment continues, microorganisms adhere to the carrier 2 in the fluidized bed apparatus and the carrier 2 becomes enlarged, so the sedimentation rate of the carrier 2 gradually decreases, and eventually the separation section 7 cannot completely separate the carrier 2. It disappears and becomes entrained in the runoff water 9. As a result, troubles such as clogging and abrasion occur in the coagulation-sedimentation device and sand filter device in the subsequent stage.

Conventionally, in order to avoid such troubles, the separation section 7 has been designed to have as much room as possible and be made as large as possible. In many cases, it is difficult to determine whether or not the carrier 2 should be separated, and as a result, the force separation section 7 is often designed to be excessively large, resulting in an unstable and uneconomical structure. It was done.

It has also been considered to collect the microorganism-attached carriers 2 that flowed out with the runoff water 9 by once leading the runoff water 9 to a sedimentation tank and sufficiently precipitating it there, but in this case, Floating bacterial cells contained in the effluent water 9 also precipitate together with the carrier 2. When this precipitate is returned to the fluidized bed apparatus, the suspended microbial cells in the precipitate are also returned at the same time, so that the concentration of suspended microbial cells in the fluidized bed increases. For this reason, the adhesion and proliferation of microorganisms to the carrier 2 is hindered, resulting in new troubles such as deterioration of the original function and promotion of outflow of the carrier 2.

The present invention was developed after thorough investigation and research into these conventional troubles that occur during the actual design and operation of fluidized bed equipment. The purpose of the present invention is to provide a rational and economical fluidized bed biological treatment device that can perform the following tasks.

The present invention involves suspending carriers for attaching microorganisms in a tank, circulating the carriers through airlift pipes installed in the tank, and separating the carriers in a separation section based on the difference in specific gravity to produce separated water. a fluidized bed type aeration tank for discharging water, a settling tank for guiding the separated water flowing out from the fluidized bed type aeration tank to precipitate and separate the water, and a settling tank for guiding the precipitate precipitated in the settling tank to remove the carriers in the precipitate. and a return mechanism that returns the carrier separated by the liquid cyclone to the fluidized bed type aeration tank. It is also characterized in that a microbial film stripping device is attached between the cyclone and the microbial film that guides the precipitate in the sedimentation tank and strips the microbial film attached to the carrier in the precipitate.

Further, an embodiment of the present invention will be described with reference to the drawings. In the second illustrated example, 1 indicates a fluidized bed aeration tank, which is almost the same as the conventional device shown in FIG. 1, and the same reference numerals are used. They show the same parts. Outflow water 9 from this tank 1 is connected to be guided to a settling tank 10, and the precipitate 11 settled in the settling tank 10 is led to a hydrocyclone 12 by a pump P etc. The separated carriers 2 are arranged so as to be returned to the fluidized bed type aeration tank 1 via a return pipe 13.

In the figure, 14 indicates overflow water from the settling tank 10.

Thus, the raw water that has been pretreated as necessary is introduced into the fluidized bed type aeration tank 1 from the raw water introduction pipe 5. In the fluidized bed type aeration tank 1, carriers 2 to which microorganisms are attached are suspended, and due to the air lift action of the air blown from the air introduction pipe 4 into the air lift pipe 3 arranged in the tank, the air lift pipe 3
It circulates inside and outside, and the raw water that is introduced also circulates and flows. Then, while circulating and flowing in the tank 1, the pollutants in the raw water come into contact with the carrier 2 to which microorganisms are attached, and are biologically decomposed and removed. A part of the liquid in the tank is thus led to a separation section 7 partitioned by a partition wall 6, where most of the carrier 2 is sedimented and separated due to the difference in specific gravity, and flows out from an outflow section 8 as effluent water 9. The separation area of this separation section 7 is such that most of the carriers 2 are sedimented and separated, and SS in the raw water and floating bacteria grown in the tank 1 are carried away with the outflow water 9 and flowed out. It is determined that

The effluent water 9 from the tank 1 is then sent to a settling tank 10, where the carriers 2 and some suspended SS remaining in the effluent water 9 are separated by precipitation. The separation area of this settling tank 10 is determined so that most of the suspended SS does not settle and the carriers 2 remaining in the inflowing water are completely separated. Unlike the separation section 7, here the carrier 2 settles at the terminal sedimentation velocity of its single particles, so it is possible to achieve the purpose with a relatively small scale. The overflow water 14 that is separated in the settling tank 10 and flows out is sent to a subsequent post-processing device (not shown) such as coagulation sedimentation, sand filtration, etc., as necessary.

The precipitate 11 precipitated in the settling tank 10 is sent to the liquid cyclone 12 by a pump P, where the carrier 2 and floating SS are separated, and the carrier 2 is recovered and sent from the return pipe 13 to the fluidized bed aeration tank. 1, the suspended SS is separately taken out and sent to a post-treatment device together with the overflow water 14 of the settling tank 10, as the case may be.

By providing this liquid cyclone 12, the return of floating bacteria to the fluidized bed aeration tank 1 is eliminated, and the accumulation of floating bacteria in the fluidized bed aeration tank 1, which has tended to occur in the past, is prevented. As a result, the adhesion of microorganisms to the carrier 2 is inhibited, and the processing function deteriorates.
Troubles such as excessive outflow of the carrier 2 out of the tank can be eliminated.

Further, the present invention can achieve the above-mentioned object more effectively also by attaching a microbial film peeling device 15 in front of the liquid cyclone 12 as shown in the third illustrated example.

That is, a microbial membrane stripping device 15 is attached in front of the liquid cyclone 12, and the precipitate 11 from the settling tank 10 is guided to the stripping device 15, so that excess microorganisms in the precipitate 11 adhere to it and easily flow out. After removing the microbial membrane from the carriers 2, the carriers 2 are separated and recovered by the liquid cyclone 12 and returned to the fluidized bed aeration tank 1, thereby preventing an increase in the number of carriers 2 flowing out from the tank 1. The amount of microorganisms in the tank 1 can be kept constant, making it possible to continue stable biological treatment.

The microbial film peeling device 15 may be any device that can sufficiently peel off the microbial film on the surface of the carrier 2, such as by using a stirrer or the stirring effect of air blowing. For example, the device shown in FIG. A stirring tank filled with granular solids 16 having a larger particle size or specific gravity than the carrier 2, as disclosed in Japanese Patent Publication No. 58-40295, was effective.

As described above, according to the present invention, the drawbacks of the conventional fluidized bed apparatus, such as uneconomical design due to an excessively large separation section, troubles in the downstream equipment due to the outflow of microbial-attached carriers, and problems in the fluidized bed aeration tank. It is possible to eliminate both the inhibition of adhesion to the carrier and the deterioration of the treatment function due to the accumulation of suspended bacteria on the carrier, and it is a compact device that is an original feature of fluidized bed biological treatment equipment, and is rationally and economically efficient. It is possible to stably exhibit load processing performance.

[Brief explanation of drawings]

Figure 1 is a model diagram of a conventional fluidized bed aeration tank, Figure 2
3 to 3 are model diagrams showing embodiments of the present invention, and FIG. 4 is a model diagram showing an example of a microbial membrane peeling device in the present invention. DESCRIPTION OF SYMBOLS 1... Fluidized bed aeration tank, 2... Carrier, 3... Air lift pipe, 4... Air introduction pipe, 5... Raw water introduction pipe, 6... Partition wall, 7... Separation part, 8... Outflow part,
9... Outflow water, 10... Sedimentation tank, 11... Sediment, 12... Liquid cyclone, 13... Return pipe,
15...Microbial film peeling device.

Claims (1)

[Scope of Claims] 1. A carrier for attaching microorganisms is suspended in a tank, the carrier is circulated and flowed through an air lift tube provided in the tank, and the carrier is separated in a separation section based on the difference in specific gravity. A fluidized bed type aeration tank that allows separated water to flow out of the fluidized bed type aeration tank, a settling tank that guides the separated water flowing out from the fluidized bed type aeration tank to precipitate and separate the water, and a sedimentation tank that guides the precipitate precipitated in the settling tank and separates it into the precipitate. A biological treatment device comprising: a liquid cyclone that separates the carrier; and a return mechanism that returns the carrier separated by the liquid cyclone to the fluidized bed aeration tank. 2. Suspend carriers for microbial attachment in a tank, circulate and flow the carriers using an air lift pipe installed in the tank, separate the carriers in a separation section based on the difference in specific gravity, and let the separated water flow out. A fluidized bed type aeration tank, a settling tank for guiding the separated water flowing out from the fluidized bed type aeration tank to precipitate and separate the water, and guiding the precipitate precipitated in the settling tank to adhere to the carrier in the precipitate. A microbial film stripping device that strips a microbial film, a liquid cyclone that guides the effluent of the microbial film stripping device and separates the carriers in the effluent, and a fluidized bed aeration system that removes the carriers separated by the liquid cyclone. A biological treatment device characterized by comprising a return mechanism for returning the material to a tank.