KR101938024B1 - Sludge-concentrating method and apparatus - Google Patents

Abstract

A method and apparatus capable of simply concentrating sludge to a high concentration. A screen residue separation step of separating the sludge into a screen residue and a sieve sludge, a chemical liquid mixing / mixing step of mixing the chemical liquid into the sludge sludge, and a solid-liquid separation of the sludge produced in the chemical liquid mixing / Wherein the sludge is separated from the sludge. A screen residue separation section for separating the sludge into a screen residue and a sieve sludge, a chemical solution / flocculation section for mixing the chemical solution with the sludge sludge, and a flocculation sludge produced from the chemical solution / flocculation section by solid-liquid separation And a sludge concentrator for concentrating the sludge.

Description

Technical Field [0001] The present invention relates to a sludge-concentrating method and apparatus,

The present invention relates to a sludge thickening method and apparatus, and more particularly, to a preferable method and apparatus as a pretreatment for anaerobic digestion treatment.

The anaerobic digestion treatment of the sludge is less sludge generation than the aerobic treatment, the hospital microorganisms and parasites are quickly killed and stabilized, the supply of oxygen is unnecessary, the power consumption is small, and biogas containing methane gas as a main component is also obtained It is a technology that has been applied for a long time as an energy saving treatment method. On the other hand, the anaerobic digestion facility requires a large capacity, and the treatment of digestion sludge is also a technology with a heavy burden on the cost of pharmaceuticals.

Therefore, as a sludge disposal method in the present situation, there are still many cases in which sludge is dehydrated and buried without anaerobic digestion, and dehydration and incineration are disposed. For example, a conventional sludge anaerobic treatment is shown by the block flow chart shown in Fig. This flow will be described.

The sludge 11 is sent to the storage device 12 and then the sludge 11 is sent to the solid-liquid separator 13 to be solid-liquid separated into the concentrated sludge 14 and the separation liquid 15, 14 is sent to the anaerobic digestion apparatus 16 and the anaerobically digested sludge is sent to the digested sludge flocculation apparatus 17 to separate the separated liquid 18 and the digested sludge flocculation 19 is prepared And the digested sludge agglomerates 19 are sent to the dewatering device 20 to separate the separated liquid 21 and prepare the dewatered cake 22. [ The separation liquid 15, the separation liquid 18 and the separation liquid 21 are sent to the wastewater treatment facility 23 and the like. In the digester sludge flocculating apparatus 17, a flocculant is often added.

[0005] On the other hand, Patent Document 1 discloses an anaerobic digestion process in which (a) a pretreatment step for solid-liquid separation of manure mixed with sludge, (b) an anaerobic digestion process for direct anaerobic digestion without dehydrating solids separated in the process, and (c) (D) a dehydration process for dehydrating and separating the effluent from the anaerobic digestion process with the solids and segregated water, (e) separating water from the pretreatment process, and the dehydration process from the dehydration process. By treating the biological wastewater treatment facility with biologically oxidizing and denitrifying separation water, it is possible to treat the organic wastewater treatment facilities such as sludge, sludge such as sludge, sludge, manure, and plant and animal residues in an energy-saving manner , Manure, unsanitary sieve in purified water tank sludge, sanitary compost, solid fuel conversion, manure, sludge, sludge treatment method proposed have.

Patent Document 2 discloses a method in which a first sludge generated from a first sedimentation tank in a wastewater treatment facility and an excess sludge generated from a final sedimentation tank are mixed and stored and then a flocculant is added to the sludge to perform a primary flocculation treatment Then, the sludge having been subjected to the primary coagulation treatment is subjected to a concentration treatment so as to have a sludge concentration of 6 to 8%, a coagulant is then added to the sludge after the concentration treatment to perform a secondary coagulation treatment, The sludge subjected to coagulation treatment is subjected to a dehydration treatment to concentrate the two kinds of sludge of the second sludge and the excess sludge generated by the wastewater treatment into one system and in the subsequent dehydration step By concentrating and maintaining the optimum sludge concentration, it is possible to maximize the total efficiency in the concentration and dehydration processes of these wastewater sludge Is proposing a sludge treatment method and system.

Patent Document 3 proposes a slit type concentrator for increasing the conveying ability of the solid-liquid separator and increasing the pressure squeezing effect.

Japanese Patent Application Laid-Open No. 10-216785 Japanese Laid-Open Patent Publication No. 2009-90240 Japanese Patent Application Laid-Open No. 2003-211293

In conventional sludge thickening processes, screen residues of 3 to 4 mm or more in particle diameter are separately removed from the front end before concentration, but the screen residue of a particle size smaller than that is supplied to the concentration process as it is and is concentrated with the sludge .

Examples of the concentration method include a gravity concentration method in which sludge is sedimented by gravity, a belt concentration method using a belt-like screen that allows moisture to pass through without passing solid matter in the sludge, a centrifugal concentration method using solid- And a mechanical concentration method. In the gravity concentration method, the sludge is usually concentrated without injecting a chemical solution. However, the concentration ratio is about 2 to 3 times, and in order to increase the concentration ratio, it is necessary to secure a sufficient residence time, and thus an extremely large-capacity thickener is formed. Alternatively, it is necessary to add a chemical solution, and it is not realistic to obtain a high concentration sludge. Further, in the conventional mechanical concentration method, a large amount of chemical liquid is required to increase the solid matter recovery rate, and in the belt concentration method, a large amount of high-pressure cleaning water for cleaning the belt is required. Further, in the centrifugal concentration method, since the vessel containing the sludge is rotated at a high speed, there is a problem that a large power is required.

It is also desired to improve the concentration of sludge which is anaerobically digested, which further shortens the HRT of the conventional anaerobic digestion treatment as described above and further contributes to downsizing of the digestion tank.

Further, in the prior art, there is a problem that the dewatering property of the sludge after the anaerobic digestion treatment deteriorates, and an effective means for coping with this problem has been desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus capable of simply concentrating sludge to a high concentration.

The present invention is as follows.

1) The screen residue separation step of separating the sludge into a screen residue and a sludge separation sludge, a chemical solution / flocculation step in which the chemical solution is mixed in the sludge sludge, and a flocculation sludge produced in the chemical solution / flocculation step are concentrated And a concentrating and separating step of separating solid-liquid into solid and liquid.

2) a screen residue separating section for separating the sludge into screen residue and sieving sludge, a chemical solution / flocculation section for mixing the chemical solution with the flask sludge, and a flocculation sludge generated from the chemical solution / And a concentrated separation section for performing solid-liquid separation.

The present invention relates to a method for removing screen residues and hair, which are small in diameter and have a small diameter and a long fibrous shape, which have not been removed in the past when they are separated into screen residue and sludge in the screen residue separation step It is the largest feature. Since the sludge obtained together with the screen residue is sufficiently removed as compared with the conventional one, it becomes possible to obtain concentrated sludge of high concentration with low power without causing mechanical troubles such as entanglement with the rotating part in the concentration step, It is possible to improve the dewaterability by mixing the screen residue with the anaerobic digestion sludge at the downstream stage.

According to the present invention, it is possible to concentrate the sludge by a device with a narrow space and a low power, and the separated screen residue can be used or stored in another process as a dehydrating assistant and used for desired sludge treatment at a desired time.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an explanatory diagram including an example of a concentration apparatus for practicing one aspect of the method of the present invention.
2 is an explanatory diagram showing a configuration of a conventional processing apparatus.
Fig. 3 is an explanatory diagram showing an embodiment in which an anaerobic digestion tank is provided at the rear end of the sludge separation unit, the digested sludge is mixed with concentrated sludge, and is returned to the anaerobic digestion tank.

In the present invention, onion means sludge discharged from a process of treating an organic material such as sewage, manure, and pouring. Examples of such sludge include second-hand sludge, excess sludge, and the like.

In the present invention, screen residues are those separated from the sludge and include crude floats separated by a nominal size of 74 mu m in accordance with the sewage test method, and preferably have a particle size of 0.5 mm or more Means a porous plate having a particle diameter of 2.0 mm or more, or a pore diameter of 0.5 mm or more, or a pore diameter of 2.0 mm or more, or a shroud separated from a screen having a wire mesh of 60 to 100 mesh.

Here, the particle diameter is the value classified by the sieve, and the pore diameter means the diameter of the hole.

First, a screen residue separation process for separating sludge into screen residue and sludge will be described.

A process for separating and recovering the screen residue contained in the sludge in the screen residue separation process, and a device used in the process will be described.

The sludge from which screen residues are separated is a slurry and typically has a SS of at least 5 g / l (liters).

The separation of the screen residue can be carried out basically by filtering the sludge using a sieve means having a particle size smaller than the particle size to be separated according to the particle size of the screen residue or as desired. For example, in general, when the ratio of the second sludge having a large amount of screen residue is high, the above-mentioned screen is used as a coarse screen, and when the ratio of surplus sludge having a small screen residue content is high, But is not limited thereto.

Examples of the sieve means include the above-mentioned perforated plate or a screen using a wire mesh.

The shape of the screen residue separating section for separating the screen residue and the screen residue into the screen residue is not particularly limited. For example, a screening device for separated screen residue, a vibrating mechanism for preventing clogging of the screening means .

Next, the chemical solution mixing and coagulation process will be described.

In the present application, the chemical liquid means at least a medicament containing a flocculant, and may contain other medicines other than the flocculant, for example, a pH adjuster and the like. Further, the chemical liquid is not limited to a liquid. The chemical liquid can be used as a coagulant alone, a mixed use of a coagulant and another medicament, or a combined use with a time lag.

In this chemical solution mixing and coagulation step, coagulated sludge is prepared by injecting and mixing at least a flocculant into the sludge sludge. The chemical liquid mixing and coagulating portion for mixing the coagulant to the sludge is usually a coagulating bath having the coagulant injecting means. However, if the coagulating sludge can be prepared, it may be a simple tube or a tubular body provided with the coagulant injecting means. In addition, the chemical solution mixing / condensation section may be provided with a flocculation tank storage tank for storing a solution of a flocculating agent quantitatively dissolved therein, and injecting the flocculating agent solution from the tank into a flocification tank for sludge sludge. This method is preferable because the coagulant can be efficiently injected without waste.

The amount of the flocculant added in the chemical solution mixing and flocculating step is preferably 0.2 to 1.0%, more preferably 0.3 to 0.6% based on the SS (suspended solid) mass in the sludge.

Examples of the flocculant include, but are not limited to, inorganic flocculants (e.g., ferric polysulfate or PAC, sulfate bands, etc.) and organic polymer flocculants (hereinafter also referred to as polymer flocculants) But it is preferable to include at least a polymer flocculant. Examples of the polymer flocculant include a cationic system, an anionic system and a positive system, and examples thereof include an amidine flocculant, an acrylamide flocculant, and an acrylic acid flocculant.

Next, the concentration and separation step of solid-liquid separation of the coagulated sludge prepared in the chemical solution mixing and coagulation process with the concentrated sludge and the separation liquid will be described.

According to the present invention, as described above, concentrated sludge having a high concentration can be prepared by subjecting the coagulated sludge to solid-liquid separation by the concentration and separation step.

Here, the concentrated separation unit for separating the coagulated sludge into concentrated sludge and separation liquid by solid-liquid separation is not particularly limited, and may be a simple tank to which the gravity concentration method is applied, a centrifugal separator to which the centrifugal concentration method is applied, A separator using a screen, and the like. Among them, a slit-type concentrator is preferable. For example, a plurality of original plates described in Patent Document 3, in which a processed product is received as a slit plate and a circumferential surface is protruded on a slit plate on which a plurality of slits are formed, The liquid is eccentrically rotated by the rotating shaft in the water discharge direction so that the processed product is sent to the discharge side on the slit plate. In this process, the liquid component falls from the gap with the disk in the slit and is filtered, Further, in addition to this means, there is a machine structure in which a belt conveyor is formed on the slit plate, which rotates in the direction of discharge of the processed material close to the upper surface of the slit plate, and compresses the collected material on the slit plate to dewater. When a slit type concentrator is applied, high concentration, for example, a high concentration of 4 to 12 mass% can be stably and reliably performed at a low running cost.

The concentrated sludge separated in the concentration and separation step may be supplied to a desired treatment step and subjected to an arbitrary treatment.

It is preferable that the concentrated sludge supply unit capable of collecting the concentrated sludge and supplying the concentrated sludge in a fixed amount to the treatment apparatus is provided with a pump in which the quantification means and the transfer means are integrated. For example, . However, by arranging at least the sludge thickening section of the sludge thickening device according to the present invention on the upper part of the anaerobic digestion tank, the concentrated sludge discharged from the thickening section can be dropped directly into the digester or through the screw conveyor. In this case, since the injection pump and the like are not required, the low power can be achieved.

In the case where the treatment process in the subsequent stage is a digestion process, as shown in Fig. 3, the withdrawal pipe of the digestion sludge is branched and a pipe for conveying the digestion sludge to the anaerobic digestion tank is formed, and the concentrated sludge and digestion sludge are mixed It is possible to lower the concentration and viscosity of the input sludge to the anaerobic digestion tank and to reduce the pump power for the addition.

A part or all of the separated liquid obtained by subjecting the coagulated sludge to solid-liquid separation in this concentration and separation step can be mixed in an arbitrary treatment step. In this case, the separated liquid may or may not be mixed with the screen residue.

Next, an example in which the sludge concentration technique of the present invention is applied as a pretreatment for anaerobic digestion treatment is described below.

In this embodiment, the screen residue obtained in the screen residue separation step is used to improve the dewaterability of the sludge after the anaerobic digestion treatment. In the sludge recovered from the screen residue, a chemical solution is added, mixed and prepared, and then concentrated to a high concentration (for example, 4 to 12 mass%). The separated liquid separated in the concentration step is mixed with the screen residue separated at the front end, and the whole or a part thereof is mixed with the anaerobic digestion sludge after the anaerobic digestion treatment and supplied to the dehydration processing step.

The concentrated sludge separated in the concentrating and separating process is introduced into the anaerobic digestion process. Conventionally, the sludge was concentrated by gravity concentration or various mechanical concentration. However, the concentration of the sludge supplied to the anaerobic digestion process was about 3 to 4% and at most about 5%. Since the screen residue in the sludge is not separated in the concentration step, it is introduced into the anaerobic digestion process together with sludge, and most of it is decomposed by the anaerobic digestion treatment.

As described above, the sludge (sieve sludge) from which the screen residue has been recovered is mixed with the anaerobic digestion sludge after the anaerobic digestion treatment in a total amount or a part of the screen residue separated and recovered in the chemical solution / flocculation process . In this case, when the anaerobic digestion sludge is additionally treated with the flocculant, the addition of the screen residue to the digested sludge can be carried out by adjusting the particle size of the screen residue and the pore diameter of the means for separating the aggregated sludge produced by the flocculant And the like, it can be appropriately selected before or after the addition of the coagulant or simultaneously with the addition of the coagulant, and can be used in combination. If the addition of the screen residue is after the addition of the flocculant, it is preferred that at least the resulting flocculant sludge is added to the flocculent sludge during or before the treatment in the dewatering process.

The recovered screen residue may be stored by carrying out drying treatment or the like as desired.

The concentrated sludge separated in the concentration and separation step is supplied to the anaerobic digestion process as described above. When the sludge condensing section can be installed on the upper part of the anaerobic digestion tank, the discharged concentrated sludge is directly introduced into the digester with gravity. Otherwise, the concentrated sludge is recovered and supplied to the anaerobic digestion process. It is preferable to carry out the anaerobic digestion treatment for more efficient operation management.

Examples of the concentrated sludge supply unit capable of collecting the concentrated sludge and supplying the same in a fixed amount to the anaerobic digestion apparatus include the above-described pump in which the quantification means and the transfer means are integrated.

Further, a part or all of the separated liquid obtained by solid-liquid separation of the coagulated sludge in this concentration and separation step can be mixed with the anaerobic digestion sludge obtained in the anaerobic digestion process. In this case, the separated liquid may or may not be mixed with the screen residue.

As described above, the digested sludge of the concentrated sludge treated in the anaerobic digestion process can be further treated with the screen residue as desired by the flocculant, but if it is intact, the alkalinity of M is high and the treatment with the flocculant is difficult It is preferable to dilute it, and a separate liquid can be used for the dilution. In this case, the screen residue added may or may not be mixed with the separation liquid.

Since the separation liquid contains phosphorus, calcium, siloxane, and the like, it may be returned to the step of recovering them and recovered.

Next, an example of the present invention will be further described with reference to the drawings.

1 is a block flow diagram showing an embodiment of the present invention. The sludge thickening apparatus of the present invention comprises at least a screen residue separating section 1, a chemical liquid mixing and condensing section including a coagulating bath 2 and a chemical liquid reservoir 3, and a sludge thickening section 4 do. First, the sludge is sent to the screen residue separation unit 1 and separated into screen residue and sludge sludge. Next, the chemical sludge is sent to the coagulation admixture tank 2 through a pipe, and the chemical solution of the chemical liquid storage tank 3 is added to the coagulation admixture tank 2 during the piping or agglomeration and preparation. The coagulated sludge is introduced into the sludge thickening section (4) and separated into a concentrated sludge of high concentration and a separation liquid. The concentrated sludge is supplied to the pump via the feeder provided in the concentrated sludge transfer pump 5, and is transferred quantitatively to the downstream anaerobic digestion process. The screen residue separated in the screen residue separation section and the separated liquid separated in the sludge thickening section are mixed in the screen residue / separation liquid tank (6), mixed with digested sludge after the anaerobic digestion treatment, Process.

Fig. 3 is a block flow chart showing an embodiment in which the anaerobic digestion tank 7 is formed at the rear end of the enrichment / separation section 4. Fig. The concentrated sludge separated in the concentrating and separating section 4 is anaerobically digested in the anaerobic digestion tank 7 to become anaerobic digestion sludge and is withdrawn through the digested sludge withdrawal pipe 10a. In the digester sludge extraction pipe 10a, the digester sludge transfer pipe 10b is branched, and at least part of the anaerobic digestion sludge is returned to the anaerobic digestion tank 7. A mixing tank 9 for mixing the concentrated sludge and the anaerobic digestion sludge is formed in the digester sludge transporting pipe 10b and the mixed sludge is supplied to the anaerobic digestion tank 7. In the embodiment shown in the drawings, there are provided a charging pump 8 for supplying a mixture of concentrated sludge or concentrated sludge and anaerobic digestion sludge to the anaerobic digestion tank 7, and a sludge drawing unit 7 for drawing the anaerobic digestion sludge from the anaerobic digestion tank 7. Although the pump 10 is used, if the sludge can be supplied or withdrawn by its own weight, the pump is unnecessary.

Example

Hereinafter, embodiments of the present invention will be described. Sewage sludge from sewage treatment plant A was subjected to the sludge concentration test of the present invention in accordance with the embodiment of Fig. The sewage sludge used in the test was a gravity-concentrated sludge obtained by mixing a second sludge and an excess sludge at a ratio of about 1: 1.

Further, the present invention is not limited at all by this embodiment.

Table 1 shows the specifications of the sludge thickener used in the test. In the test, 0.5% (relative to SS ratio) of a sieve onionecation polymer flocculant (average molecular weight: 3 million) was added.

Table 2 shows the properties of the separated liquid obtained in the sludge and concentrating step before and after the concentration treatment. One sludge is sludge.

The analytical method was performed as follows.

· TS (Total solids, total evaporation residue); 105 ° C Evaporation residue weight (JIS K 0102)

VTS (Volatile total solids); Heat loss at 600 ℃ (JIS K 0102)

· Suspended solids (SS); The weight of sediment (JIS K 0102) at a rotation speed of 3,000 rpm by centrifugal separation for 10 minutes,

· Volatile suspended solids (VSS); Reduced ignition loss of suspended particles at 600 ℃ (JIS K 0102)

M alkalinity; The titrant was titrated to pH 4.8 with a 0.1 mol / l hydrochloric acid solution at 3,000 rpm for 3 minutes by centrifugal separator (sewage test method)

Coarse floats; Analysis of coarse floors by nominal size 74 μm sieve (sewage test method)

From the above results, it is apparent that the present invention can efficiently concentrate sludge to a high concentration.

Next, the sludge subjected to the anaerobic digestion treatment of the concentrated sludge was subjected to a dehydration test, and a change in dehydration property depending on the presence or absence of the screen residue separated by the pretreatment was examined.

The anaerobic digestion treatment conditions are shown in Table 3. Table 4 shows properties of the sludge before and after the anaerobic digestion treatment.

The sludge obtained by mixing the total amount of the screen residue separated by the pretreatment of the anaerobic digestion with the total amount of the concentrated and separated liquid at a ratio of 1: 1 to the anaerobic digestion sludge was provided for the dehydration test. As a comparative example, a sludge obtained by mixing anaerobic digestion sludge and a concentrated separation solution at a ratio of 1: 1 was subjected to a dehydration test. Cationic polymer flocculant (average molecular weight: 3 million) was used for sludge dewatering. The dehydrator used was a belt press type dehydrator, and the dehydration condition was 4.9 kN / m in shear tension and 1.0 m / min in shear rate. As a result, the polymer flocculant injection rate and water content of dehydrated sludge were as shown in Table 5.

From the above results, it can be seen that dehydrated sludge having a low water content at a low drug solution injection rate can be obtained according to the present invention.

1: screen residue separation unit
2: coagulation tank
3: Chemical solution reservoir
4: sludge thickener
5: Concentrated sludge transfer pump
6: Screen residue / separation liquid tank
7: Anaerobic digester
8: Injection pump
9: Mixing tank
10: Sludge Pump
10a: Digitized sludge plumbing
10b: piping for returning sewage sludge
11: Sewing
12: Storage device
13: Solid-liquid separator
14: concentrated sludge
16: Anaerobic digester
17: Digestion sludge aggregate preparation device
18: Separated liquid
19: Digestion sludge agglomerates
20: Dewatering device
21: Separated liquid
23: Wastewater treatment plant

Claims (14)

A screen residue separation step of separating the sludge into a screen residue and a sieve sludge, a chemical liquid mixing / mixing step of mixing the chemical liquid into the sludge sludge, and a solid-liquid separation of the sludge produced in the chemical solution / A condensation separation step,
A concentrated sludge supply step of recovering the concentrated sludge and supplying a fixed amount to the anaerobic digestion step,
Mixing the digested anaerobic digestion sludge with the concentrated sludge in the anaerobic digestion process and returning the anaerobic digestion process to the anaerobic digestion process;
And a mixing step of mixing the whole or a part of the separated screen residue and the separated liquid individually or in a mixture to the anaerobic digestion sludge after the anaerobic digestion process,
The mixing step is a step of dewatering the sludge or a method of concentrating the sludge prior to the dewatering step. delete delete delete delete The method according to claim 1,
The screen residue separation step separates screen residues having a particle diameter of 0.5 mm or more. A screen residue separation section for separating the sludge into a screen residue and a sieve sludge, a chemical solution / flocculation section for mixing the chemical solution with the sludge sludge, and a flocculation sludge produced from the chemical solution / flocculation section by solid-liquid separation ,
And a concentrated sludge supply unit capable of recovering the concentrated sludge and supplying the concentrated sludge in a predetermined amount to the anaerobic digestion apparatus,
The concentrated sludge supply unit includes a metering pump,
The concentrated sludge supply unit is formed at a higher position than the anaerobic digestion apparatus,
And a mixing section for mixing the anaerobic digestion sludge from the anaerobic digestion sludge from the anaerobic digestion apparatus and the anaerobic digestion sludge from the digested sludge transfer pipe branched from the pipeline, The anaerobic digestion sludge mixed with the concentrated sludge in the mixing section is returned to the anaerobic digestion apparatus again,
And a mechanism for mixing the whole or a part of the separated screen residue and the separated liquid individually or in a mixture to the anaerobic digestion sludge after the anaerobic digestion process,
The mechanism is a sludge thickening device that is in contact with a dewatering process or a process before the sludge dewatering process. delete delete delete delete delete delete 8. The method of claim 7,
Wherein the screen residue separating section comprises a screen having a perforated plate of 0.5 mm or more in pore size.

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