JPS6274500A - Method and apparatus for treating activated sludge in order to lower water content of dehydrated cake - Google Patents

Abstract

PURPOSE:To lower the water content of a dehydrated cake, by charging newspaper in the sewage of an aeration tank to dissolve the same in order to enhance the activity of sludge. CONSTITUTION:A newspaper decomposition tank 17 is suspended in the sewage of an aeration tank 3 and a stirrer 19 is provided in the decomposition tank 7. Newspaper is dissolved in sewage under stirring and flows in the sewage of the aeration tank 3 through the numerous small holes 18 provided or the peripheral wall part 17a and the bottom plate part 17b of the decomposition tank 17 by drilling. The fibers 22 of the newspaper crosslink and adsorb the particle group 21 of activated sludge to enhance the bonding degree of the particle group. Thereafter, the sewage is successively sent to a conc. sludge tank and a flocculation tank and a flocculating liquid is injected in the sewage. By this method, the activity of sludge itself becomes high and the water content of the cake dehydrated by a dehydrator is lowered.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention belongs to the field of activated sludge treatment methods and devices that purify sewage using bacteria and microorganisms present in sewage, and more specifically, Belongs to the field of activated sludge treatment methods and devices that are characterized by reducing the moisture content of the dehydrated cake that is generated when sludge that is generated by dissolving newspaper in the wastewater of a tank is dehydrated. .

(Prior art) When dewatering sludge using a screw press, centrifuge, etc., it is possible to reduce the transportation cost of the dehydrated cake and to minimize the energy required for final disposal such as landfilling, drying, and incineration. Various methods have been attempted to lower the water content of.

A common method for reducing the water content of this dehydrated cake is to pre-flocculate the sludge using a polymer flocculant and then dehydrate it. The limit is said to be %.

In addition, in a previous application (Japanese Patent Application No. 136666/1982), the present applicant has proposed adding newspaper slurry liquid or powdered newspaper to concentrated sludge in a coagulation tank connected to a thickened sludge tank constituting an activated sludge treatment device. We have filed a patent application that is characterized by reducing the water content of a dehydrated cake produced when sludge is dehydrated by injecting or mixing it with a molecular flocculant to coagulate and dehydrate sludge.

Injecting or mixing newspaper slurry liquid or powdered newspaper into thickened sludge causes the particles that make up the sludge to be cross-linked and adsorbed by the fibers that make up the newspaper, thereby increasing the bonding strength of the sludge particles and increasing the strength of the sludge itself. Increase the intensity (
This is to reduce the moisture content of the dehydrated cake.

In this way, if newspaper is directly thrown into the thickened sludge immediately before dehydration, it will take time for the newspaper to completely dissolve, so it is necessary to dissolve the newspaper in water to form a slurry or to make it into powder to facilitate dissolution. Must be. The former method has the problem of requiring a separate large-capacity newspaper slurry tank, and the latter method has the problem of requiring a grinder to grind a large amount of newspaper into powder. This was discovered as a result of research and experiments conducted after the patent application was filed.

(Problems to be Solved by the Invention) In view of the above-mentioned problems, the present invention has been developed by introducing newspaper into the sewage of the aeration tank that constitutes the activated sludge treatment equipment, and by stirring and mixing the sewage due to the aeration. The newspaper is completely dissolved and mixed uniformly into the sewage, and when floc-like sludge is generated in the aeration tank, the particles of this sludge are cross-linked and adsorbed by the fibers that make up Shinkaigami. This was done with the aim of increasing the strength and lowering the water content of the dehydrated cake produced when sludge is dehydrated.

(Means for Solving the Problems) The present invention involves pumping sewage in a storage tank into an aeration tank for a fixed amount, and generating floc-like sludge by pumping air into the sewage in the aeration tank and agitating it. Afterwards, the sludge is sent to a settling tank, and a part of the sludge settled in the settling tank is returned to the aeration tank, and other surplus sludge is sent to a thickened sludge tank, and the sludge in this thickened sludge tank is dehydrated by a dewatering machine. In addition, in the activated sludge treatment method in which sewage is treated by discharging the supernatant water in the settling tank, the strength of the sludge generated by dissolving newspaper by throwing it into the sewage in the aeration tank. An activated sludge treatment method characterized by increasing the water content of the dehydrated cake produced when dehydrating sludge, and a storage tank for storing sewage, and a storage tank for storing sewage, an aeration tank for pumping and agitating air into the sewage to produce floc-like sludge; a settling tank for settling the sludge in the sewage sent from the aeration tank; An activation system consisting of a sludge return device for returning part of the sludge to the aeration tank, a thickened sludge tank for sending surplus sludge in the settling tank, and a dehydrator for dewatering the sludge in the thickened sludge tank. In the sludge treatment equipment, a newspaper dissolving tank with numerous small holes drilled in the peripheral wall and bottom plate is suspended in the aeration tank, and an agitator is installed in the newspaper dissolving tank to dissolve the newspaper. The newspaper put into the wastewater of the dissolving tank is stirred by a stirrer and dissolved in the wastewater, and the dissolved newspaper flows out from numerous small holes drilled in the peripheral wall and bottom plate of the newspaper dissolving tank. This is an activated sludge treatment device characterized by dispersing sludge in wastewater of an aeration tank.

(Example) An activated sludge treatment apparatus according to the present invention is shown in FIGS. 1 and 2.

The generated wastewater first flows into the screen device 1, where coarse solids in the wastewater are removed, and the wastewater from which the coarse solids have been removed naturally flows into the storage tank 2. The wastewater in the storage tank 2 is sent by a pump P into the aeration tank 3 at a constant rate.

The capacity of this aeration tank 3 is quite large, and the blower 4 continuously sends air into the sewage in the aeration tank 3. As a result, the sewage in the aeration tank 3 is mixed by the action of the air (agitation and mixing). When air is sent into the sewage in the aeration tank 3 and an appropriate amount of oxygen is supplied to the activated sludge microorganisms in the sewage, floc-like suspended matter is generated.This suspended matter is a collection of aerobic microorganisms. It is called activated sludge,
Has sedimentation properties.

Surplus sewage in the aeration tank 3 in which activated sludge has been generated naturally flows into the settling tank 5. In the settling tank 5, the activated sludge that has sedimentation properties naturally settles to the bottom and becomes purified supernatant water. is separated from the top.

This purified supernatant water naturally flows out and enters the disinfection tank 6, where it is disinfected and then discharged to the outside.

On the other hand, the concentration of activated sludge in the aeration tank 3 must be kept constant, and since the activated sludge produced in the aeration tank 3 alone has a low concentration, the activated sludge that has settled at the bottom of the settling tank 5 A part of the sludge is returned to the aeration tank 3 by the sludge return device 7 to help purify the inflowing sewage.
Surplus sewage that is not returned is periodically sent to the thickened sludge tank 8.

The thickened sludge in the thickened sludge tank 8 is sent by the pump P to the first and second flocculation tanks 9 and 10.

Coagulation liquid tanks 11, 12.13 in which various different polymer flocculants are diluted with water are connected to the first and second coagulation tanks 9.10. The flocculating liquid in the flocculating liquid tanks 11, 12, and 13 is injected into the thickened sludge fed into the thickened sludge 10 to flocculate the thickened sludge, and then the concentrated sludge is fed into a dehydrator (screw press in the embodiment) 14 to be dehydrated. The dehydrated cake dehydrated by the dehydrator 14 is carried out by a conveyor 15 for carrying out, and the filtrate produced during dehydration is stored in a filtrate settling tank 16.

Further, in the present invention, a bottomed cylindrical newspaper dissolving tank 17 with numerous small holes 18 bored in the peripheral wall part 17a and the bottom plate part 17b is suspended in the wastewater of the aeration tank 3, and this A stirrer 19 is disposed within the newspaper dissolving tank 17. In addition, in FIGS. 1 and 2, M indicates a motor for operating the stirrer.

Then, when the newspaper is directly thrown into the waste water of the newspaper dissolving tank 17, the thrown newspaper is stirred and dissolved in the waste water by the action of the stirrer 19, and the dissolved newspaper is disposed on the peripheral wall of the newspaper dissolving tank 17. 17a and bottom plate part 17b
The waste water flows into the aeration tank 3 through numerous small holes 18 bored in the aeration tank 3. In the aeration tank 3, the sewage is mixed and stirred by the aeration of air sent into the sewage, and the dissolved newspaper that has flowed into the sewage in the aeration tank 3 through the small hole 18 of the newspaper dissolution tank 17 is It is uniformly dispersed in the wastewater by the mixing and pushing action of the wastewater.

The newspaper dissolved in the wastewater is dispersed in the form of fibers, as shown in Figure 3 (a) and (b).
The 21 groups of particles constituting the generated activated sludge exist in an unstable state, and the fibers 22 constituting the newspaper cross-link and adsorb the 21 groups of activated sludge particles that exist in an unstable state, This cross-linked and adsorbed activated sludge particle 21
It is imagined that the group is surrounded by fibers 22 that make up the Shinkai paper. As a result, the bonding strength of the 21 groups of particles constituting the activated sludge is increased (it is understood that the strength of the activated sludge itself is increased).

Moreover, in the present invention, newspaper is thrown into wastewater when activated sludge is generated, and the activated sludge particles 21 are cross-linked and adsorbed by the fibers 22 constituting the newspaper. Since the time required for the final dewatering treatment is long, the contact time between the activated sludge particle groups 21 and the fibers 22 constituting the newspaper is long (this is also a factor that increases the strength of the activated sludge itself). Furthermore, since the capacity of the aeration tank 3 is extremely large, even if a large amount of newspaper is thrown in, it will be easily dissolved.

After the activated sludge whose strength has been increased in this way enters the thickened sludge tank 7, it is transferred to the first and second coagulation tanks 9, 10.
When the sludge is sent to the flocculation tank 11, 12.
The flocculating liquid in 13 is injected. The polymer of the polymer flocculant constituting the flocculating liquid exists bent in the shape of a thread in the thickened sludge, and when the flocculating liquid is injected into the activated sludge, as shown in Figure 4, this Since the polymer 23 of the polymer flocculant works with the fibers 22 constituting Shinkai Paper to cross-link and adsorb the 21 groups of particles of the concentrated sludge, the bonding strength of the 21 groups of particles of the agricultural shrinkage sludge further increases and the concentration increases. It is understood that the strength of the sludge itself is further increased.

It is understood that the fibers that make up Shinkaishi dissolved in sewage function as a flocculant, which increases the bonding strength of the particles that make up the sludge, increasing the strength of the sludge itself. As a result, the water content of the dehydrated cake dehydrated by the dehydrator decreases, and a clean filtrate (separated water) with a low content of sludge solids is obtained.

Specific examples and comparative examples of the present invention are listed below.

Example 1 1. OOppm of sewage at 40 On? The amount of sewage in the aeration tank 3 is always kept at 1. Aeration tank 3 where some of the sludge was continuously returned from the settling tank 6 to the aeration tank 3 so that the concentration of the sewage was maintained at 5.00 Oppm at all times. The total weight of the sludge inside is 1.000 x 5,000 g/n? =5000 kg SS, and 1500 kg of newspaper corresponding to 30% of the weight of the sludge in this aeration tank 3 was initially charged into the newspaper dissolving tank 17.

The weight of sludge solids in wastewater treated per day is 400
rd/day Xi, 000g/rrr=400kg-DS
1 day, and an attempt was made to pull out excess sludge from the settling tank 5 to the sludge thickening tank 8, which corresponds to 120 kg DS/day of pure sludge solids, which is 30% of the weight of the sludge solids treated in this day. . 3 for the weight of pure sludge solids
Newspaper is used at a rate of 0%, so in reality (1
Excess sludge corresponding to the weight of sludge solids (20+36)=156 kg-DS/day was drawn out from the settling tank 5 to the sludge thickening tank 8. After that, 36 kg/day of newspaper was transferred to newspaper dissolving tank 17.
continued to invest in.

The concentrated sludge drawn into the concentrated sludge tank 8 was dehydrated using a screw press, and the water content of the resulting dehydrated cake was measured and found to be 68%.

Example 2 Sewage was treated under the same conditions as in Example 1 except that the ratio of newspaper to the total weight of sludge in the aeration tank 3 was changed to 15%.

Newspaper is added at a rate of 15% of the weight of pure sludge solids, so in reality (120←18) = 1
Excess sludge equivalent to the weight of 38 kg-037 days of sludge solids was drawn out from the settling tank 5 to the sludge thickening tank 8. 18 thereafter
kg/day of newspaper was continuously fed into the newspaper dissolving tank 17.

4 The concentrated sludge drawn into the reduced sludge tank 8 was dehydrated using a screw press, and the moisture content of the resulting dehydrated cake was measured and found to be 75%.

Comparative Example The wastewater was treated under the same conditions as in Example 1 without putting any newspaper into the wastewater of the aeration tank 3. 1
Excess sludge equivalent to the weight of 20 kg-037 days of sludge solids was drawn out from the settling tank 5 to the sludge thickening tank 8.

When the moisture content of the dehydrated cake obtained by dewatering the concentrated sludge using a screw press was measured, it was 85%Q.Here, the reduction in the weight of the dehydrated cake due to the decrease in the moisture content will be calculated.

The weight of pure sludge solids treated per day is in each case 120 kg - 037 days.

In Example 1, surplus sludge equivalent to 156 kg-037 days of sludge solid weight was treated, and the weight of the dehydrated cake obtained by dewatering this surplus sludge was 155 kgX 100/(100-68)= 487.
It is 5 kg.

In Example 2, surplus sludge equivalent to 138 kg-037 days of sludge solid weight was treated, and the weight of the dehydrated cake obtained by dewatering this surplus sludge was 138 kgX 100/(100-75)= 552
kg.

In the comparative example, surplus sludge equivalent to 120kg-037 days of sludge solid weight was treated, and the weight of the dehydrated cake obtained by dewatering this surplus sludge was 120kgX100/(100-85)=800
kg.

Therefore, in Example 1, (800-
487,5) = 312.5 kg of excess water was separated, and in Example 2, compared to the comparative example, (800-5
52) = 248 kg of excess water was separated, and the weight of the Shinkai paper thrown into the wastewater (36 kg/in Example 1)
It turns out that the weight of the dehydrated cake is considerably reduced as a result of the extra separation of water of a much greater weight than 18 kg/day in Example 2).

(Effects) (1) Newspaper is put into the sewage of the aeration tank that constitutes the activated sludge treatment equipment, and the stirring and mixing action of the sewage caused by this aeration completely dissolves the newspaper and uniformly disperses it in the sewage. When floc-like activated sludge is generated in the tank, the fibers that make up the newspaper cross-link and adsorb the particle groups that make up the activated sludge, increasing the bonding strength of the particle groups and increasing the strength of the sludge itself. As a result, the water content of the dehydrated cake produced by dewatering the sludge can be reduced. Furthermore, since the new paper is placed in a large capacity aeration tank, it is possible to put in a large amount of newspaper.

(2) A newspaper dissolving tank is suspended in the aeration tank, a stirrer is installed in the newspaper dissolving tank, and the newspaper thrown into the waste water of the newspaper dissolving tank is can be easily and completely dissolved.Also,
The newspaper dissolved in the newspaper dissolving tank flows into the wastewater of the aeration tank through numerous small holes drilled in the surrounding wall and bottom plate, so that the dissolved newspaper is uniformly dispersed in the wastewater of the aeration tank. can be done.

(3) Since newspaper is used, which is readily available and inexpensive as it exists in large quantities as used paper in the vicinity, it is possible to reduce the moisture content of the dehydrated cake at a low cost.

(4) Since the sludge particles are strongly (cross-linked and adsorbed) by the fibers that make up the newspaper, the content of sludge solids contained in the filtrate (separated water) is reduced, making post-treatment of the filtrate easier. .

[Brief Description of the Drawings] Fig. 1 is a diagram showing an activated sludge treatment apparatus according to the present invention;
Figure 2 is an enlarged sectional view of the aeration tank 3, and Figures 3 (a) and 3 (b) are imaginary diagrams showing before and after the sludge particle groups 21 are cross-linked and adsorbed by the fibers 22 constituting the dissolved newspaper. FIG. 4 is an imaginary diagram showing a state in which a group of sludge particles 21 cross-linked and adsorbed by fibers 22 constituting newspaper are further cross-linked and adsorbed by a polymer 23 which is a polymer flocculant. (Explanation of symbols of main parts) 1 Niclean device 2: Storage tank 3: Aeration tank 4 Niblore 5: Sedimentation tank 6: Disinfection tank 7: Sludge return device 8: Thickened sludge tank 9: First coagulation tank 10 2 Second coagulation tank 11.12.13: Coagulation liquid tank 14: Dehydrator 17: Newspaper dissolving tank 18: Small holes 19: Stirrer 21: Particles constituting sludge 22: Fibers constituting newspaper 23: High Polymer patent applicant for molecular flocculant Sunbeck Co., Ltd. Figure 2 M Figure 4 Figure 3 (A)

Claims (2)

[Claims] (1) The sewage in the storage tank is sent to the aeration tank for a fixed amount, and air is pumped into the sewage in the aeration tank while stirring to generate floc-like sludge, which is then sent to the settling tank, where it settles. A part of the sludge is returned to the aeration tank, and other surplus sludge is sent to the thickened sludge tank, and the sludge in the thickened sludge tank is dehydrated by a dehydrator, and the supernatant water in the settling tank is discharged. In the activated sludge treatment method that treats sewage by dissolving sewage in the aeration tank, newspapers are added to the sewage in the aeration tank to increase the strength of the generated sludge, thereby increasing the strength of the sludge when dewatering the sludge. 1. An activated sludge treatment method for reducing the water content of a dehydrated cake, characterized by reducing the water content of the dehydrated cake produced. (2) A storage tank for storing sewage, an aeration tank for pumping air into the sewage sent from this storage tank and agitating it to generate floc-like sludge, and a settling tank for settling sludge in sewage; a sludge return device for returning part of the sludge in the settling tank to the aeration tank; and a thickened sludge tank for sending excess sludge in the settling tank. In an activated sludge treatment device consisting of a dehydrator for dewatering sludge in a thickened sludge tank, a newspaper dissolving tank with numerous small holes drilled in the peripheral wall and bottom plate is placed in the aeration tank. At the same time, a stirrer is installed in this newspaper dissolving tank, and the newspaper put into the waste water of the newspaper dissolving tank is stirred and dissolved in the waste water, and the surrounding wall of the newspaper dissolving tank and An activated sludge treatment device for reducing the moisture content of a dehydrated cake, characterized in that dissolved newspaper flows out from numerous small holes drilled in the bottom plate and is dispersed in the wastewater of an aeration tank.