JPH0634994B2 - Upflow biological treatment method and apparatus thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to upward flow biological treatment provided with a stirring mechanism for wastewater containing organic substances such as sewage, night soil sewage, industrial wastewater, and water, and nitrates. The present invention relates to a method and an apparatus for aerobically or anaerobically purifying by using immobilized microorganisms in the apparatus.

[Conventional technology]

Conventionally, as immobilized microorganisms, (i) sand, ceramic, activated carbon, or adherent type that adheres and proliferates microorganisms on the surface of plastic, (ii) agar, polyacrylamide gel, inside a polymer gel such as a photocrosslinkable resin Three types are used: a comprehensive type that encloses microorganisms, (iii) any carrier, and a self-immobilized type that granulates the microorganisms by the force of the microorganisms themselves without using any chemicals.

Further, three types of upward-flow-type biological treatment devices are used, which are a fluidized bed type, a fixed bed type, and a sludge bed type.

Most of these up-flow type biological treatment devices are (i) prevention of formation of madballs due to adhesion, coalescence, etc. of particulate immobilized microorganisms or self-immobilized substances in the tank, (ii) granular immobilized microorganisms Alternatively, an agitator is often provided in the tank for the purpose of smoothing the flow of the self-immobilized product and preventing the formation of dead zones in the tank.

In addition, in the conventional stirring method for the upward flow type biological treatment apparatus, since the stirring is performed with uniform stirring strength from the lower part to the upper part of the apparatus, the granular settling material or the self-fixing material having a large sedimentation speed is placed in the lower part. Those with a small settling rate tended to collect at the top. As a result, a concentration distribution of the granular immobilization product or the self-immobilization product is generated in the height direction of the apparatus, and the processing performance is deteriorated.

For example, in an upflow-type fluidized-bed biological treatment device that uses adherent-type immobilized microorganisms, microbial adherent carriers with large particle size are present at high density in the lower part of the device, and carrier with small particle size in the upper part of the device. Tend to exist sparsely. The adherent-type immobilized microorganism is a method in which treatment is performed with a biofilm formed by the growth of microorganisms on the surface of the carrier. Also occurs. Therefore, since the brushing effect is large in the lower part where the carrier density is high, the biofilm is difficult to develop.

In a conventional upward-flowing fluidized-bed biological treatment device that agitates the device at a uniform strength in the height direction, carriers with thin large-sized biofilm particles are gathered in the lower part and biological substances are in the upper part. It fell into a state in which a small-diameter carrier having a thick film was present. As a result, it was confirmed that the treatment performance especially in the lower part was lowered due to the lack of the amount of biofilm, and the treatment performance of the entire apparatus was lowered.

Moreover, in the upward flow sludge bed type biological treatment apparatus using self-immobilized products, the self-immobilized products with high density tended to gather in the lower part and the self-immobilized products with low density tended to gather in the upper part. Under such a situation, in the case of the conventional method in which the stirring is performed uniformly in the height direction of the apparatus, the sludge bed at the lower part lacks in fluidity, while the upper part disturbs the sludge bed by excessive stirring. As a result, the quality of the treated water deteriorated due to the sludge rolling up in the upper part.

[Problems to be Solved by the Invention]

The present invention provides a conventional upward flow biological treatment that has been caused by adopting a uniform stirring method, even though the distribution state of the granular immobilization product or self-immobilization product in the device height direction as described above is different. It is an object of the present invention to solve the problems of the apparatus and to develop a biological treatment apparatus capable of exhibiting superior treatment performance as compared with the conventional method.

[Means for Solving the Problems]

As a result of various studies, the present inventors have found that in the upward flow biological treatment, the problem of the conventional method can be solved by changing the stirring force in the reaction tank between the upper part and the lower part stepwise, The present invention has been completed.

That is, the present invention, in an upward flow type biological treatment method for performing biological treatment by immobilized microorganisms under aerobic or anaerobic conditions by applying stirring force by a stirring mechanism while upwardly circulating waste water. In the stirring mechanism, stirring blades are provided in multiple stages on a vertical rotation shaft, and the stirring strength of the stirring mechanism is gradually or stepwise reduced from the inflow portion of the wastewater toward the outflow portion, the area of the stirring blade, The present invention relates to an upflow biological treatment method characterized by adjusting at least one of mounting pitches.

The present invention also provides an upward flow type biological treatment apparatus in which a layer of immobilized microorganisms is formed in a biological reaction tank in which waste water flows upward, and stirring blades are arranged in multiple stages on a vertical rotating shaft in the tank. In the above, the stirring blade has a smaller area or a wider mounting pitch as it goes from the lower part to the upper part in the tank.

The degree of decrease in stirring strength in the present invention varies depending on the type of immobilized microorganisms used, particle size, specific gravity, size of device, etc., but desirably the stirring strength of the upper part is 10-80% of the lower part. Is desired.

In order to change the stirring strength, it is possible to reduce the area of the stirring blade toward the upper part of the apparatus or to widen the mounting pitch.

Further, the present invention exerts its effect when applied to an upflow type biological treatment apparatus, particularly a fluidized bed type and a sludge bed type.

An upflow fluidized bed biological treatment apparatus is a granular immobilized microorganism in which microorganisms are adhered to or entrapped in a granular carrier, and the granular immobilized microorganism is excited by water or / and gas to flow upward. Is a device for biological treatment while maintaining the fluid state. Upflow type sludge bed type biological treatment equipment maintains sludge beds or sludge blankets with granular biomass (self-immobilized products) formed by microorganisms themselves by upward flow excited by water and / or gas. It is a device that performs processing while doing so.

Although the present invention relates to a stirring method for an upflow-type biological treatment apparatus, it is not limited to the biological treatment apparatus and is an effective method for all upflow-type reaction apparatuses.

[Work]

According to the present invention, it is possible to maintain a high stirring strength in the lower part of the apparatus, in which the particulate immobilized product or the self-immobilized product tends to be present at a high density. As a result, it is possible to prevent the amount of microorganisms from being insufficient due to biofilm separation in the lower part in the upflow type fluidized bed method, and the formation of a dead zone due to insufficient stirring in the lower part in the upflow type sludge bed method. Further, since the stirring in the upper part of the device can be made gentle, it is possible to prevent the sludge from rolling up in the upper part in the upward flow type sludge bed method. Due to these actions, superior processing performance is exhibited as compared with the conventional method.

〔Example〕

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 FIG. 1 is a schematic diagram of an anaerobic upflow type fluidized bed type biological treatment apparatus using adherent type immobilized microorganisms, which is intended for biological denitrification. Water obtained by adding methanol to wastewater containing nitrate passes through the raw water inflow pipe 1 and the biological treatment device 2
Water flows upward from the bottom of the. The inside of the biological treatment apparatus 2 is filled with sand having an effective diameter of 2 mm and a uniform coefficient of 1.3 as an adsorbent carrier 3 for denitrifying bacteria. The carrier 3 is maintained in a fluidized state by an upward flow of water and an upward flow excited by nitrogen gas generated as a result of denitrification, and is agitated by a stirrer 4. The treated water flows out from the upper part of the device 2 through the treated water outflow pipe 7. Reference numeral 6 denotes a carrier withdrawal tube for removing the carrier 3 enlarged by the attachment of the denitrifying bacteria.

In order to confirm the effect of the present invention, the stirring blade 5 of the stirrer 4
Two types were used, one of the present invention shown as a schematic diagram in FIG. 2 and the conventional type shown as a schematic diagram in FIG. The size of the equipment and stirring blades are summarized below.

Upflow fluidized bed type biological treatment equipment φ1000mm × height 3200mm Stirring blade size ・ Fig. 2 4 flat blades (width 200mm from the bottom, 2
(00 mm, 100 mm, 50 mm) ・ Fig. 3 4 flat blades (blade widths are all 80 mm) ・ Both blade length 800 mm, mounting pitch 800 mm, agitator rotation speed, both 1.5 rpm Table-1 and Fig. 2 FIG. 3 shows the denitrification performance and the amount of attached denitrifying bacteria when the stirring blade of FIG. 3 was used. The denitrification performance was shown by the denitrification rate per unit volume.

As shown in Table-1, by changing the stirring strength in the apparatus height direction as in the present invention, the amount of microorganisms in the lower part is increased as compared with the conventional method, and as a result, the total amount of microorganisms is also increased,
The denitrification rate also obtained a large value.

Example 2 FIG. 4 is a schematic diagram of an aerobic upflow-type fluidized-bed biological treatment apparatus using entrapped immobilized microorganisms, which is intended for nitrification of ammonia contained in a tap water source. Lake water contaminated with ammonia is passed through the raw water inflow pipe 1 to the pre-aeration tank 9 in a downward flow, where oxygen necessary for nitrification is dissolved. The raw water then passes through the water pipe 8 and the nitrification tank 1
Water is flowed up to 0. Inside the nitrification tank 10, the diameter is 3
Immobilized nitrifying bacteria 3 entrapped in mm alginate calcium gel are filled. 3 is maintained in a fluidized state by an upward flow of water and a stirring flow of a stirrer 4. The treated water flows out through the outflow pipe 7.

In order to confirm the effect of the present invention, as the stirrer 4, a fifth
Two types are used, one with a different attachment pitch of the stirring blade 5 as shown in the figure (invention) and one with uniform pitch as shown in the figure in FIG. 6 (conventional method). did.

The sizes of the device and the stirring blade are as follows.

・ Nitrification tank φ900mm × height 3000mm ・ Stirring blade width 30mm × length 800mm ・ Mounting pitch (from bottom) Fig. 140, 140, 340, 340, 340, 400, 400mm Fig. 6 All 300mm ・ Agitator rotation speed Both are 4 rpm Table 2 shows the nitrification rate in each case.

Thus, by changing the attachment pitch as in the present invention, a higher nitrification rate than the conventional method was obtained. The cause is
It is considered that the flow of the immobilized nitrifying bacteria in the lower part became active, and the effective tank volume increased.

The effectiveness of the present invention was similarly confirmed in other examples in which the stirring speed was changed.

〔The invention's effect〕

As described above, according to the present invention, microorganisms grow uniformly over the entire tank, and the total amount of microorganisms increases, which is accompanied by insufficient amount of microorganisms due to biofilm peeling at the bottom and insufficient stirring. The formation of dead zones is prevented and excellent processing performance can be exhibited.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an anaerobic upward flow biological treatment apparatus of the present invention, and FIGS. 2 and 3 are schematic diagrams showing the arrangement of stirring blades used in the apparatus of FIG. 2 shows the stirring blade of the present invention, and FIG. 3 shows the stirring blade of the conventional method. FIG. 4 is a schematic view of the aerobic upflow biological treatment apparatus of the present invention, and FIGS. 5 and 6 are schematic views showing the arrangement of stirring blades used in the apparatus of FIG. The figure shows the stirring blade of the present invention, and FIG. 6 shows the stirring blade of the conventional method. 1 ... Raw water inflow pipe, 2 ... Biological treatment device, 3 ... Adhesive carrier, 4 ... Stirrer, 5 ... Stirring blade, 6 ... Carrier withdrawal pipe, 7 ... Treated water outflow pipe, 8 ... Water pipe, 9 ... Front aeration tank, 10 ... Nitrification tank

Claims (2)

[Claims] 1. An upward-flow-type biological treatment method for performing biological treatment with immobilized microorganisms under aerobic or anaerobic conditions while applying a stirring force by a stirring mechanism while upwardly circulating waste water. The stirring mechanism is provided with a multi-stage stirring blade on a vertical rotating shaft, and the stirring blade area is reduced so that the stirring strength by the stirring mechanism is gradually or stepwise reduced from the inflow part of the wastewater toward the outflow part. , An upflow biological treatment method, characterized in that at least one of the mounting pitches is adjusted. 2. An upward flow type biological treatment apparatus in which a layer of immobilized microorganisms is formed in a biological reaction tank in which waste water is upwardly flowed and stirring blades are arranged in multiple stages on a vertical rotating shaft in the tank. In the upflow type biological treatment apparatus, the stirring blade has a smaller area or a wider mounting pitch from the lower part to the upper part in the tank.