JP2000140893A - Treatment of sludge and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce load on a water treatment system for removing phosphorous by subjecting a sludge mixture or its concentrate to oxidation treatment with a chlorine-oxidizing agent and removing phosphorous from the liquid separated from the sludge mixture. SOLUTION: This treatment process comprises: subjecting a sludge-containing liquid mixture 1 to oxidation treatment in the sludge treatment equipment 2 using a chlorine-based oxidizing agent; thereafter, introducing the treatment sludge-containing liquid mixture into a gravity concentration vessel 3a to obtain a separated liquid 61 and a sludge concentrate 72; introducing the sludge concentrate 72 into a dehydrator 4 to obtain another separated liquid 62 and a dehydrated cake 8; introducing the dehydrated cake 8 into an incineration furnace 5 to obtain an exhaust gas 9 and incineration ash 10; and sewage/wastewater treatment equipment or exclusive treatment equipment for such separated liquid where the separated liquids 61 and 62 are returned and treated, is the one using a biological treatment process having a phosphorus removal treatment mechanism, a physiochemical treatment process represented by a flocculant addition treatment process or a combination of these processes, whose purposes are phosphorus removal treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to the field of sewage wastewater treatment, and more particularly to a method and an apparatus for treating sludge generated as a result of advanced treatment centering on phosphorus removal of sewage wastewater and treatment of sewage wastewater. is there.

[0002]

2. Description of the Related Art In the treatment of sewage wastewater, an activated sludge method is often used, in which organic matter and SS (suspendable solid matter), which are often measured as BOD, are mainly treated. .

On the other hand, since nitrogen and phosphorus cause eutrophication of enclosed water, in recent years, nitrogen and phosphorus in sewage have also been removed and the environment of enclosed water discharged from treated water has been reduced. There is a growing movement to preserve the environment. Among such techniques used in so-called advanced treatment, examples of using a modified method of the activated sludge method include an anaerobic aerobic activated sludge method capable of simultaneously removing BOD and SS and phosphorus, and BOD and There is an anaerobic anoxic aerobic activated sludge method capable of simultaneously removing SS, phosphorus and nitrogen.

FIG. 3 shows an example of a wastewater treatment apparatus using the anaerobic-aerobic activated sludge method. The wastewater treatment apparatus based on the anaerobic and aerobic activated sludge method mainly includes an initial sedimentation basin 12, an anaerobic tank 13 in which activated sludge releases phosphate ions in cells into wastewater by a biological phosphorus release reaction, Activated sludge is composed of an aerobic tank 14 for taking in phosphate ions in wastewater into cells by a typical phosphorus uptake reaction and a final sedimentation pond 16. The phosphorus intake of the activated sludge in the aerobic step is larger than the phosphorus release in the anaerobic step, and the difference between the phosphorus intake and the phosphorus release corresponds to the phosphorus removal from the wastewater.

[0005] After removing relatively large and heavy solids contained in the wastewater 11 in the first settling basin 12, a biological phosphorus release reaction in an anaerobic process and a biological phosphorus uptake reaction in an aerobic process are performed. Then, the phosphorus in the wastewater is changed into a constituent component of the sludge, and is finally discharged from the wastewater treatment apparatus as surplus sludge. In addition, BOD in wastewater is removed in both the anaerobic process and the aerobic process, and SS is mainly used in the first settling basin 12.
And sewage is removed in a final sedimentation basin 16 which is introduced after undergoing biological treatment in the anaerobic tank 13 and the aerobic tank 14.

FIG. 4 shows an example of a wastewater treatment apparatus using the anaerobic oxygen-free aerobic activated sludge method. The wastewater treatment apparatus using the anaerobic anoxic aerobic activated sludge method mainly includes an initial sedimentation basin 12, an anaerobic tank 13 in which activated sludge releases intracellular phosphate ions into wastewater by a biological phosphorus release reaction, An anoxic tank 19 in which activated sludge causes a biological phosphorus uptake reaction and a denitrification reaction in which phosphate ions in wastewater are taken into cells, and an organism in which activated sludge takes up phosphate ions in wastewater into cells. Tank 1 that induces the biological phosphorus uptake reaction and nitrification reaction
4 and a final settling basin 16. The phosphorus uptake of activated sludge in the anoxic and aerobic processes is greater than the phosphorus release in the anaerobic process, and the difference between this phosphorus intake and the phosphorus release corresponds to the amount of phosphorus removed from wastewater . The anaerobic anoxic aerobic activated sludge process shown in FIG. 4 is a process of removing phosphorus and nitrogen together with BOD and SS in wastewater by performing a biological dephosphorization reaction and a denitrification reaction. Is what you do.

Although not shown in FIGS. 3 and 4,
For example, there is a method in which a coagulant such as an aluminum salt or an iron salt is added to an inflow portion or an outflow portion of a reaction tank, and a biological dephosphorization treatment and a physicochemical dephosphorization treatment are used in combination.

In addition, there is widely used a method of sterilizing a treated wastewater by contacting it with chlorine gas, sodium hypochlorite, calcium hypochlorite or chlorine dioxide before discharging the treated wastewater into a river or sea area. Used.

Conventional methods for treating sludge generated during the treatment of sewage wastewater include concentration, dehydration, anaerobic digestion, aerobic digestion, and incineration.

FIG. 5 shows an example of a conventional method for treating wastewater and a method for treating sludge by the activated sludge method. Sludge generated from a water treatment system based on the activated sludge method in which the wastewater 11 is sequentially passed through the first sedimentation basin 12, the aeration tank 21 and the final sedimentation basin 16 to obtain the treated water 17 is mainly solidified in the final sedimentation basin 16. Sludge from the final sedimentation basin obtained by liquid separation 2
Of the two, so-called excess sludge excluding returned sludge 18;
Firstly, the sludge is drawn from the sedimentation basin. These sludges are introduced into the concentration tank 3 to obtain the concentrated sludge 7 and the separated liquid 61. The separated liquid 61 is usually first returned to the position before the sedimentation basin 12, and the concentrated sludge 7 is treated by the dehydrator 4 which is the next sludge treatment step, to obtain the dewatered cake 8 and the separated liquid 62. The separated liquid 62 is usually returned to a position before the settling basin 12. The dewatered cake 8 is introduced into the incinerator 5, where the exhaust gas 9 and the incinerated ash 1
0 is obtained. The incineration ash 10 is usually disposed of in landfill. In some cases, the dehydrated cake 8 is directly disposed to landfill.

FIG. 6 shows another example of a conventional sludge treatment method, showing an example of a sludge treatment plant for centrally treating sludge sent from three sewage treatment plants. 3
Once the sludge drawn from the sedimentation basin obtained at several sewage treatment plants is concentrated at each sewage treatment plant, it is diluted as necessary to make the sludge concentration suitable for pipeline transport. It is transported to the sludge centralized treatment plant via the road 31. In the sludge centralized treatment plant, the transported sludge is received in each adjusting tank 32, mixed in the mixing tank 33, and then processed by the concentrator 3 to be separated into the separated liquid 61 and the concentrated sludge 7. The separation liquid 61 is transferred to the separation liquid storage tank 34.
The concentrated sludge 7 is introduced into the concentrated sludge storage tank 35, and the concentrated sludge 7
Is then processed by the dehydrator 4 to separate the separated liquid 62 and the dehydrated cake 8
And get The dehydrated cake 8 is sent to the incinerator 5 for incineration. After the obtained exhaust gas 9 is treated by the exhaust gas treatment equipment 37, it is released to the atmosphere via a chimney 38, and the obtained incineration ash 10 is carried out and landfilled. Separated liquids 61 and 62 obtained when the treatment is performed by the concentrator 3 and the dehydrator 4 are processed in a separated liquid treatment facility 39, and the separated liquid treated sludge 40 is returned to the mixing tank 33. 41 is sent to a nearby sewage treatment plant (= return water) to perform water treatment. In this separation liquid treatment facility 39, the separation liquid 61
And 62, a coagulation sedimentation method for the purpose of solid-liquid separation is mainly used, and a polymer coagulant, polyaluminum chloride, ferric chloride and the like are used as coagulation chemicals.
Of these flocculants, aluminum and iron salts are
Although it also has a phosphorus removal treatment effect, the purpose of this coagulation precipitation treatment is basically solid-liquid separation treatment, so the amount of coagulant added is small, and the phosphorus removal treatment performance is not good. Is normal. In a series of sludge treatment steps, odor gas 42 originating from the decay of sludge is generated. Therefore, after treatment is performed by a deodorizing facility such as a biological deodorization tower 43 or an activated carbon adsorption tower 44, the air is discharged to the atmosphere Dissipate. Such concentrated treatment of sludge aims at economicalization of sludge treatment by consolidating sludge treatment equipment and its operation management personnel, and has recently been implemented for sewage treatment in large cities.

[0012]

Generally, a method for removing phosphorus in sewage wastewater includes a biological treatment method represented by the above-described anaerobic aerobic method or anaerobic anoxic aerobic method and a flocculant. There is a physicochemical treatment method represented by the addition treatment. The former is
Utilizing biological reactions such as a phosphorus release reaction and a phosphorus uptake reaction by microorganisms to remove phosphorus in sewage by incorporating phosphorus into microorganisms, the latter is:
The method removes phosphorus in sewage by adding a coagulant such as an iron salt or an aluminum salt to form a poorly soluble phosphate. As a biological phosphorus removal method, an anaerobic aerobic method or an anaerobic anoxic aerobic method, which combines an anaerobic treatment step and an aerobic treatment step, is a typical method. Even in a conventional biological treatment method including only a treatment step, there is a mechanism in which phosphorus is also removed along with BOD removal. This means that in the aerobic treatment step, pollutants in the wastewater are removed at a BOD: N: P ratio of approximately 100: 5: 1, and some of the removed pollutants are used for the synthesis of microorganisms (sludge). Used, phosphorus is also used as a component of its microbial organisms, so that phosphorus is removed from wastewater by a mechanism.

Unlike the physicochemical treatment method, the biological treatment method does not require the purchase and addition of a flocculant.
Since there is no problem that the added coagulant component eventually becomes a sludge component and the amount of generated sludge increases, there is a tendency to particularly emphasize and adopt a phosphorus removal method in the treatment of large-scale sewage wastewater.

However, as used as part of biological phosphorus removal means, sludge containing many microorganisms can transfer phosphorus to external water when exposed to anaerobic conditions in the presence of organic matter. Because it has the property of releasing, even if phosphorus in sewage wastewater is incorporated into sludge using some biological phosphorus removal mechanism, in the process of treating sludge generated as a result of such water treatment When the sludge mixture is exposed to anaerobic conditions, the metabolism of microorganisms under anaerobic conditions releases phosphorus to the external water, that is, to the liquid side of the sludge mixture.

There are many cases in which sludge is exposed to such anaerobic conditions in the course of conventional sludge treatment. In the sludge concentration treatment equipment, the gravity concentration tank has no high-speed operation part and has relatively low operation power cost, and is therefore used in many sewage treatment plants. The residence time in this gravity concentration tank is about 10 to 15 hours, depending on the sludge concentration of the introduced sludge mixture, and the inside of the gravity concentration tank is under anaerobic conditions. Also, when transporting sludge from a sewage treatment plant to a sludge centralized treatment plant, a sludge mixed solution having a relatively high sludge concentration of about 1 to 2% of solid matter is usually transported. Depending on the distance, the residence time in the transport line is 15 to 24 hours, during which the sludge is exposed to anaerobic conditions. In addition, regardless of whether the sludge generated in the process of sewage treatment is treated at the sewage treatment plant or the sewage treatment plant, a process of storing the concentrated sludge before dewatering the concentrated sludge (storage) (A tank, a regulating tank, a mixing tank, etc.), and may have a residence time of 12 to 24 hours in the concentrated sludge storage process, during which the sludge is exposed to anaerobic conditions.

As the sludge goes through these steps, phosphorus is released into the water. That is, even if phosphorus removal treatment is performed using some biological mechanism in the wastewater treatment system, the phosphorus concentration in the separated solution generated in the sludge treatment process may increase depending on the treatment method used in the sludge treatment system. However, when the separated solution having a high phosphorus concentration is returned to the water treatment system, there is a problem that the effect of the biological phosphorus removal treatment in the water treatment system is eventually impaired. Further, even when the separated liquid is subjected to the phosphorus removal treatment using the separation liquid treatment equipment, the phosphorus load on the treatment equipment becomes large, and for example, when the coagulation precipitation treatment is performed, the amount of the coagulant used increases. There was a problem.

On the other hand, even if the sludge is exposed to anaerobic conditions, if phosphorus is sufficiently contained in the sludge at the stage of the dewatering cake, the sludge treatment / disposal process after the dewatering cake can be performed by the following steps. Whether incinerated or landfilled or directly landfilled, these processes rarely generate phosphorus-containing wastewater such as a separated liquid, so a water treatment system or a dedicated liquid processing device in which the separated liquid generated in the sludge treatment step is returned. In the case of performing the biological dephosphorization treatment or physicochemical dephosphorization treatment in the above, the treatment effect is not impaired, and when the coagulant addition treatment is performed, the use amount of the coagulant and the amount of sludge generated increase Not even.

According to the present invention, even if the sludge is exposed to anaerobic conditions in the sludge treatment process, the sludge hardly releases phosphorus into the surrounding water, and the separated liquid generated in the sludge treatment process is returned and transferred to the water treatment system. It is an object of the present invention to provide a method and an apparatus for treating sewage wastewater and sludge, which do not easily burden phosphorus removal treatment in a water treatment system.

[0019]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a chlorine-based oxidizing agent is added to a sludge mixture or a concentrated sludge extracted from a sedimentation pond of a biological wastewater treatment facility. And sludge concentration from the mixed sludge mixture, removing phosphorus from the separated liquid separated during dewatering, and a method for treating biological wastewater. In a sludge treatment apparatus comprising a concentration equipment for a sludge mixture liquid extracted from a sedimentation tank and a dewatering device for the concentrated sludge, a chlorine-based oxidizing agent is added between the upstream side of the concentration equipment and the dehydrator to perform oxidation treatment. This object has been attained by a sludge treatment apparatus characterized in that an oxidation treatment tank is provided and the separated liquid of the concentrating device and the dehydrator is sent to a device capable of removing phosphorus. Than it is.

Surplus sludge by standard activated sludge method is 2.5%
Excess sludge generated from water treatment equipment using biological phosphorus removal reaction typified by the anaerobic and aerobic activated sludge method and the anaerobic and anoxic aerobic activated sludge method contains about 4% phosphorus. However, phosphorus is eluted when sludge including these excess sludges is placed under anaerobic conditions for a long time. The relationship between the sludge standing time and the phosphorus elution amount under the anaerobic condition depends on the sludge concentration conditions and the sludge age, but according to the experimental findings of the present inventors, phosphorus elution is detected. This occurs after about 10 to 20 minutes have passed since the anaerobic condition was reached, and thereafter the amount of phosphorus eluted gradually increases. Such phosphorus elution from the sludge is due to a biological reaction, and the release of phosphorus from the sludge can be prevented by stopping the biological action. In the method of the present invention, an oxidation treatment with a chlorine-based oxidizing agent is used to stop the biological action related to the elution of phosphorus. In FIG. 1, the gravity concentration method is used in the concentration step, and the residence time in the gravity concentration process is about 10 to 15 hours as described above. Before the sludge is introduced into the gravity concentration treatment, an oxidation treatment with a chlorine-based oxidizing agent is performed.

The oxidation treatment with the chlorine-based oxidizing agent in the method of the present invention aims at stopping the biological reaction by the sterilization treatment. To perform microbiologically complete sterilization in a wet state, for example, pressurization and heat treatment at 120 ° C. for 15 to 20 minutes is performed. However, such complete sterilization is not necessarily performed in the method of the present invention. Not necessary. Some microorganisms, such as spores or oocysts, take forms in their life cycle that are resistant to the oxidizing action of chlorine-based oxidants. However, it is generally said that bacteria play the most important role in the treatment of sewage wastewater by activated sludge, but most of them are Gram-negative, which do not produce spores. It is a fungus. Therefore, considering that the time required for the step of treating the sludge after performing the oxidation treatment with the chlorine-based oxidizing agent is at most 24-36 hours, the oxidation treatment with the chlorine-based oxidizing agent is performed once. The effect of surviving spores becoming vegetative and releasing phosphorus after the vegetative bacteria have been killed appears to be relatively small. Therefore, taking into account the cost of equipment necessary for performing complete sterilization or operating costs such as heating costs, rather than complete sterilization,
It is considered more practical to sterilize the vegetative body.

[0022] Thus, the separated liquid obtained in the process of the concentration and dehydration of the sludge has a very low phosphorus concentration, so that even when the separated liquid is treated in a dedicated treatment facility, the sludge is produced. Even when the wastewater is returned to the wastewater treatment facility for treatment, the phosphorus load is extremely low, and good phosphorus removal treatment results are obtained.

Also, when a biological treatment method and a physicochemical treatment method with the addition of a flocculant are used together for removing phosphorus in a sewage wastewater treatment facility, or phosphorus is removed by a flocculation and sedimentation treatment in a treatment facility dedicated to a separated solution. In the case where the method of the present invention is not used, for example, when the treatment is used, phosphorus is eluted from the sludge in the step of sludge treatment, and the sludge is eventually removed by the coagulant. Since the biological sludge discharged out of the sludge treatment system through the sludge treatment process has a high phosphorus content, the phosphorus load on the water treatment system is relatively low, and the amount of coagulant used is low. The amount of sludge generated by the coagulant is reduced, while reducing the amount of sludge.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION What is oxidized in the present invention is a sludge mixed liquid drawn out from a sedimentation basin or its concentrated product. The concentration of these sludges is 4,0 in the sludge mixture.
About 00 to 10,000 mg / l, usually 6,000 to 8,
2,000 mg / l, and 10,000
About 0 to 30,000 mg / l, usually 15,000 to 2
It is about 000 mg / l.

The chlorine-based oxidizing agent is chlorine gas, hypochlorite,
It is a dioxide type or the like. Of these, chlorine gas, sodium hypochlorite, calcium hypochlorite and chlorine dioxide are preferred.

When chlorine gas is used as a chlorine agent, the chlorine gas dissolves in water and reacts and dissociates as follows. Cl ₂ + H ₂ O = HOCl + HCl HOCl = H ⁺ + OCl ⁻ where HOCl and OCl ⁻ are effective for sterilization.

When sodium hypochlorite is used as a chlorine agent, sodium hypochlorite has the following dissociation equilibrium in water. ^{NaOCl = Na + + OCl - HOCl} = H + + OCl - in this case, HOCl and OCl ^- is effective for sterilization.

[0028] When using calcium hypochlorite as the chlorinating agent, in water have similar dissociation equilibrium in the case of sodium hypochlorite, HOCl and OCl ^- acts effectively for sterilization.

When chlorine dioxide is used as the chlorine agent, chlorine dioxide, ie, ClO ₂ itself has a sterilizing effect. The formula for producing this chlorine dioxide is as follows. Cl ₂ + 2NaClO ₂ = 2ClO ₂ + 2NaCl

Usually, when producing chlorine dioxide, a large excess of chlorine gas (Cl ₂ ) is blown against sodium suboxide (NaClO ₂ ) to produce chlorine dioxide (ClO ₂ ).
Is relatively unstable and is manufactured on site.

Chlorine gas is inexpensive but toxic and requires careful handling and handling.

Usually, sodium hypochlorite is handled as a liquid of about 0.5 to 3%. However, when a commercially available product is purchased and used, it is manufactured in-situ using the electrolysis principle of saline solution. May be used. In the former case, although there is no need to install sodium hypochlorite production equipment on the sewage wastewater treatment side, it is necessary to transport and receive toxic sodium hypochlorite solution. It is not necessary to transport and receive the sodium hypochlorite solution, but it is necessary to install and operate a sodium hypochlorite production facility. In selecting one of the two, factors such as economy related to the scale of use of sodium hypochlorite are also taken into consideration.

Calcium hypochlorite is usually handled as a solid tablet, and is easy to handle. However, it is more expensive than chlorine gas and sodium hypochlorite. It is preferably used in wastewater treatment facilities.

When chlorine dioxide is used, it is less likely to form a chlorine compound as a harmful by-product than other chlorine-based oxidizing agents. . However, when chlorine dioxide is used, it is necessary to keep the amount of harmful sodium chlorite in such a manner that no harmful sodium chlorite remains in the processing solution.

Regarding the chlorine-based oxidizing agent to be used, when selecting whether to use chlorine gas, sodium hypochlorite, calcium hypochlorite, or chlorine dioxide, existing sewage wastewater is used. It is also possible to use the chemicals used for the sterilization of the processing system as they are, and to comprehensively consider the processing scale, the cost required for the purchase or on-site production of these chemicals, and the safety in the management of the chemicals, etc. You can select the one that is appropriate for each case.

The amount of the chlorine-based oxidizing agent added is 5 to 400 in terms of sodium hypochlorite in the case of a sludge mixture.
mg / l, preferably about 20 to 50 mg / l, in the case of a concentrated product, about 10 to 1,000 mg / l,
Preferably, about 30 to 100 mg / l is appropriate. The pH of the sludge mixture or the concentrated product to which these chlorine-based oxidizing agents are added is usually about 6.8 to 7.5. The oxidation treatment time is such that most of the sludge is killed, and varies depending on the concentration of the oxidizing agent, the water temperature, and the like, but is usually about 10 minutes to 1 hour, particularly about 15 to 30 minutes. The equipment required for this oxidation treatment is an oxidation treatment tank capable of providing the above treatment time, and equipment for introducing the chlorine-based oxidant into the oxidation treatment tank, that is, a chlorine-based oxidant storage tank, an injection pump, and the like. , An injection line, etc., and a stirrer for promoting a sufficient contact reaction between the sludge mixture or the concentrated product thereof and the chlorine-based oxidizing agent in the oxidation tank. It is also possible to separately install an oxidation treatment tank in the course of transporting the sludge mixture or its concentrated product, and the above reaction time can be secured in a pipe or open channel for transporting the sludge mixed solution or its concentrated product. In such a case, it is also possible to use a part of the transportation pipeline or the open channel as an oxidation tank. In order to prevent the added chlorine-based oxides from flowing back through the transport route of the sludge mixture or its concentrate and damaging organisms that perform wastewater treatment, the location of the chlorine-based oxidizing agent in the transport pipeline should be Provide a check valve on the upstream side, or cascade the upstream side of the chlorine-based oxidizing agent addition position in the transport open channel, or cascade the transportation route for introducing sludge into the chlorine-based oxidizing agent-added oxidation tank. It is preferable to adopt the following configuration. In addition, in order to promote contact mixing of sludge and chlorine-based oxidizing agent, a configuration shall be adopted in which a stirrer is installed in the oxidation tank, aeration and stirring is performed by introducing air, and a circulating pump is installed to perform circulating mixing. Can be. Also, when a part of the sludge transport pipeline is used for the reaction section corresponding to the oxidation tank,
A pipe mixer can be installed downstream of the chlorine-based oxidizing agent addition position to promote stirring and mixing. When an oxidation tank is separately installed, it is preferable to adopt a cover structure in order to prevent the odor of the sludge from leaking to the outside. It is preferable that a part of the sludge transport pipeline can be used as an oxidation tank in that leakage of odor can be prevented, and that the device of the present invention can be installed in a narrow place. The chemical storage tank can be installed at a position away from the oxidation tank as needed, and can be moved by gravity or an injection pump.

Although the use of an oxidizing agent such as ozone or hydrogen peroxide in place of the chlorine-based oxidizing agent can similarly provide the effect of suppressing a biological reaction, the present invention is limited to the chlorine-based oxidizing agent. It is inexpensive and economical as compared with other oxidizing agents.

The removal of phosphorus from the separated liquid separated when the sludge is concentrated and dehydrated may be performed by a known method, and may be any of a biological method, a method using a flocculant, and the like. For the separated liquid after the treatment by the device of the present invention,
When phosphorus is removed by adding an iron salt or an aluminum salt as a coagulant, the necessary theoretical amount is 1 mol of iron or aluminum per 1 mol of phosphorus, but it is actually 1.2 to 1.5 times that. By adding to a certain extent, good treated water can be obtained stably. The addition ratio of the phosphorus removing flocculant to the phosphorus amount is the same as in the conventional method (when the apparatus of the present invention is not used). By this phosphorus removal treatment, about 95 to 99% of the phosphorus is removed from the separated liquid having a phosphorus (TP) concentration of about 10 to 80 mg / l.

FIG. 1 shows an example of a sludge treatment facility based on the method of the present invention. In FIG. 1, the sludge 1 drawn from a sedimentation basin is oxidized in a chlorine-based oxidizing agent treatment facility 2 and then introduced into a gravity concentration tank 3a to obtain a separated liquid 61 and a concentrated sludge 72. The separated liquid 61 is introduced into a water treatment system for treatment. On the other hand, the concentrated sludge 72 is introduced into the dehydrator 4 to obtain the separated liquid 62 and the dehydrated cake 8. The separated liquid 62 is introduced into a water treatment system for treatment. On the other hand, the dewatered cake 8 is introduced into the incinerator 5 to obtain the exhaust gas 9 and the incinerated ash 10. The exhaust gas 9 is subjected to desulfurization treatment, denitration treatment, and the like, and then released into the atmosphere. The incineration ash 10 is landfilled. First
In the figure, it is one of the features of the present invention that the sludge drawn from the first sedimentation basin and the final sedimentation basin is subjected to oxidation treatment with a chlorine-based oxidizing agent. Also, the separation liquid 61
For treating liquids 62 and 62, ie, separation liquids 61 and 6
2. The wastewater treatment facility or separated liquid treatment facility that is returned and treated using a biological treatment method that has a phosphorus removal mechanism, or a physicochemical process represented by a coagulant addition process Another feature of the present invention is that a treatment method is used or a combination thereof is used for the purpose of removing phosphorus.

Another example of the sludge treatment equipment based on the method of the present invention is shown in FIG. In FIG. 2, the sludge 1 drawn from the sedimentation basin is subjected to a concentration treatment by the concentration equipment 3 to obtain a separated liquid 61 and a concentrated sludge 71. Separation liquid 6
1 is introduced into a water treatment system for treatment. On the other hand, concentrated sludge 7
1 is oxidized in a chlorine-based oxidizing agent treatment facility 2,
The sludge 72 after the chlorine-based oxidizing agent treatment is introduced into the dehydrator 5 to obtain the separated liquid 62 and the dehydrated cake 8. The separated liquid 62 is introduced into a water treatment system for treatment. On the other hand, the dewatered cake 8 is introduced into the incinerator 5 to obtain the exhaust gas 9 and the incinerated ash 10. The exhaust gas 9 is subjected to desulfurization treatment, denitration treatment, and the like, and then released into the atmosphere. The incineration ash 10 is landfilled. In FIG. 2, one of the features of the present embodiment is that the concentrated sludge obtained by concentrating the sludge drawn from the first sedimentation basin and the final sedimentation basin is subjected to an oxidation treatment with a chlorine-based oxidizing agent. In addition, a facility for treating the separation liquids 61 and 62, that is, a treatment facility for sewage wastewater into which the physical fluids 61 and 62 are introduced and treated or a treatment facility dedicated to the separation fluid uses a biological treatment method having a phosphorus removal treatment mechanism. In the present invention, it is a thing using a physicochemical treatment method typified by a coagulant addition treatment, or a combination thereof and an object for phosphorus removal treatment Another feature.

In the concentration step shown in FIG. 2, unlike the gravity concentration method, a concentration method having a short residence time (treatment time) such as a centrifugal concentration method having a residence time of about 5 minutes or less is used. Since the phosphorus eluted from the sludge in the concentration process is relatively small, treating the concentrated sludge with an oxidizing agent using a chlorine-based oxidizing agent reduces the chlorine-based oxidizing agent treatment equipment and reduces the chlorine-based oxidizing agent. It is economical because the amount of addition is small.

[0042]

EXAMPLE An indoor experiment was conducted on a method for treating wastewater and sludge according to the present invention. Excess sludge (MLSS 7480 mg / L, T) obtained from sewage treatment pilot experimental facility with a treatment amount of 25 m ³ / day by the anaerobic oxygen-free aerobic activated sludge method
S7930 mg / L) was used as an experimental material, and 4 L of excess sludge was placed in a 5 L beaker.

1) Without adding sodium hypochlorite to the surplus sludge, immediately after aerating the air through a diffuser ball for 1 hour and once leaving it in an aerobic state and after leaving it for 24 hours, 2) Immediately after adding a predetermined amount of sodium hypochlorite to the sludge, aerating it with air through a diffuser ball for 1 hour to make it aerobic, and leaving it to stand for 24 hours. 3) Sprinkle the excess sludge for 1 hour. After aerating the air once through a gas ball to make it aerobic, immediately after adding a predetermined amount of sodium hypochlorite and leaving it for 24 hours, the PO ₄ -P on the liquid side of the excess sludge was used. Was examined. Regarding the preparation of the analytical sample on the liquid side of the excess sludge, 300 ml of the excess sludge solution was collected from the above beaker, and immediately subjected to centrifugation at 2,000 G for 5 minutes. The filtrate obtained by filtration was used as an analysis sample.

Table 1 shows the results together with the amount of sodium hypochlorite added.

[Table 1]

As shown in Table 1, when aeration was performed after adding sodium hypochlorite, phosphorus was not taken into sludge due to aeration due to the effect of sodium hypochlorite. It is considered that the PO ₄ -P concentration on the liquid side of the excess sludge mixed liquid before, that is, immediately after the aeration treatment was increased. When sodium hypochlorite is added after aeration, that is, when sodium hypochlorite is added in a state where sludge has sufficiently taken in phosphorus, even after 24 hours, PO ₄ − on the liquid side of the excess sludge mixed liquid is added. The P concentration was kept relatively low. Also, as can be seen from the table, it seems that the amount of sodium hypochlorite added is preferably about 40 mg / L or more.

An interesting point in the results of the table is that when the untreated excess sludge mixture was aerated and left for 24 hours,
PO ₄ -P on the liquid side of the excess sludge mixture is 45.7 mg / L
In contrast, after aeration, that is, 40 mg of sodium hypochlorite in a state where phosphorus is sufficiently contained in the sludge.
/ L was added, and PO ₄ -P on the liquid side of the excess sludge mixture after standing for 24 hours was 15.1 mg / L. Similarly, when 200 mg / L of sodium hypochlorite was added, 24 hours PO ₄ -P 15 of the liquid side of the excess sludge mixture after standing.
It was 8 mg / L. That is, 40 mg / L
In the case where sodium hypochlorite is added, the effect of suppressing the PO ₄ -P concentration on the liquid side of the excess sludge mixture liquid by about 30 mg / L even after standing for 24 hours is obtained.
Compared to the cost of adding polyaluminum chloride required to remove this 30 mg / L PO ₄ -P, 40
The cost for adding mg / L sodium hypochlorite is lower. Moreover, when sodium hypochlorite is added, no new sludge is generated as in the case of performing a phosphorus removal treatment by adding an iron salt or an aluminum salt as a coagulant. The effect of preventing the dissolution of phosphorus from sludge by the chlorine-based oxidizing agent treatment can prevent an increase in the load of phosphorus in performing the phosphorus removal treatment in the water treatment system, and is also advantageous in terms of the economics of the phosphorus removal treatment. Become.

Although the results of the experiment shown in Table 1 relate to excess sludge in the biological phosphorus removal process, aerobic conditions were also applied to excess sludge from a facility only for aerobic treatment represented by the standard activated sludge method. There is a mechanism of phosphorus ingestion and phosphorus release in anaerobic conditions. By adding sodium hypochlorite etc. to such sludge, phosphorus elution under anaerobic conditions can be suppressed. Conceivable. Regardless of whether the water treatment system is a biological phosphorus removal facility combining anaerobic treatment and aerobic treatment, or a facility only for aerobic treatment typified by the standard activated sludge process, Since sludge generated in the process and to be disposed of contains sludge, even when processing mixed sludge containing surplus sludge, phosphorus is eluted from sludge by adding sodium hypochlorite, etc. It is thought that it can be suppressed.

[0048]

According to the method of the present invention, the sludge generated in the treatment of sewage wastewater by the biological treatment method including the activated sludge method using the biological phosphorus removal reaction and the standard activated sludge method is used. And subjecting the sludge mixture extracted from the sedimentation basin of the water treatment facility that generates the sludge to the sludge mixture before the concentration treatment or the sludge mixture after the concentration treatment with an oxidizing treatment with a chlorine-based oxidizing agent, and performing the concentration step and the dewatering. The wastewater containing the separated liquid generated in the process is subjected to a phosphorus removal treatment. The chlorine-based oxidizing agent used was chlorine gas, sodium hypochlorite, calcium hypochlorite, or chlorine dioxide.

In the process of sludge treatment, the sludge mixture is often exposed to anaerobic conditions.
By subjecting the sludge mixture to an oxidation treatment using a chlorine-based oxidizing agent, elution of phosphorus from the sludge can be prevented. By using such a sludge treatment method,
Since the separated liquid generated during the sludge concentration treatment and the dehydration treatment has a relatively low phosphorus concentration, even when the wastewater containing the separated liquid is returned to the original water treatment system to perform the phosphorus removal treatment, Even when transferring to a dedicated treatment facility for phosphorus removal treatment, it is possible to prevent an increase in the phosphorus load on these water treatment facilities, and to obtain good phosphorus removal treatment results in the water treatment facility. When the phosphorus removal method by adding a flocculant is employed in these water treatment facilities, the amount of the flocculant to be added can be reduced, and the generation of new sludge due to the addition of the flocculant can be suppressed. It is economical. Whether the oxidation treatment with the chlorine-based oxidizing agent is performed before the sludge concentration step or after the sludge concentration step is selected depending on a difference in characteristics such as residence time in equipment used in the concentration step. be able to. These chlorine-based oxidants are relatively inexpensive, and the cost of adding such a chlorine-based oxidant is relatively low.

Whether the chlorine-based oxidizing agent used is chlorine gas, sodium hypochlorite, calcium hypochlorite, or chlorine dioxide is a sterilization treatment of an existing water treatment system. It is possible to use the chemicals used in the process as they are, and it is suitable for individual projects in consideration of the scale of processing, the cost required for purchasing these chemicals or on-site production, and the safety of drug management. Can be selected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an apparatus for treating sewage and sludge according to one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a wastewater and sludge treatment apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an example of a conventional biological phosphorus removal treatment apparatus.

FIG. 4 is a diagram showing the configuration of another example of a conventional biological phosphorus removal treatment apparatus.

FIG. 5 is a diagram showing a configuration of an example of a conventional wastewater treatment apparatus and a sludge treatment apparatus by an activated sludge method.

FIG. 6 is a diagram showing the configuration of another example of a conventional apparatus for treating sludge generated with the treatment of sewage wastewater.

[Explanation of symbols]

 1. Sludge drawn from sedimentation basin 2. 2. Chlorine oxidizer treatment equipment Concentration equipment 3a. Gravity concentration tank 4. Dehydrator 5. 8. Incinerator Exhaust gas 10. Incinerated ash 6,61,62. Separation liquid 7, 71, 72. 7. Condensed sludge Dehydrated cake 11. Wastewater 12. First settling basin 13. Anaerobic tank 14. Aerobic tank 15. Diffuser 16. Final sedimentation tank 17. Treated water 18. Returned sludge 19. Anoxic tank (denitrification tank) 20. Nitrifying circulating fluid 21. Aeration tank 22. Sludge drawn from final sedimentation basin 23. First settling tank withdrawal sludge 31. Sludge transport pipeline 32. Adjustment tank 33. Mixing tank 34. Separation liquid storage tank 35. Thickened sludge storage tank 36. Separation liquid storage tank 37. Exhaust gas treatment equipment 38. Chimney 39. Separation liquid treatment equipment 40. Separation liquid treated sludge 41. Separation liquid treated water 42. Odor gas 43. Biological deodorization tower 44. Activated carbon adsorption tower 45. Exhaust tower

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Miyata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Kokan Kogyo Co., Ltd. (72) Inventor Kei Kei Bamba 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor: Satoru Udagawa, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan Co., Ltd. (72) Toyo Sawada, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Co., Ltd. (72) Inventor Shinichi Endo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4D059 AA03 BC02 BE00 BE31 BE37 BE49 CA14 CA22 CA24 DA45 DA46

Claims (3)

[Claims] 1. A sludge mixture or a concentrated product thereof extracted from a sedimentation pond of a biological wastewater treatment facility is oxidized by adding a chlorine-based oxidizing agent, and the sludge is concentrated from the sludge mixture and dewatered. For removing phosphorus from a separated liquid separated at the time of sludge treatment 2. The method for treating sludge according to claim 1, wherein the chlorine-based oxidizing agent is chlorine gas, sodium hypochlorite, calcium hypochlorite, or chlorine dioxide. 3. A sludge treatment apparatus comprising: a sludge mixture concentrating facility drawn out of a sedimentation pond of a biological wastewater treatment facility; and a sludge dewatering machine. Sludge characterized by providing an oxidizing tank for oxidizing by adding a chlorine-based oxidizing agent during the process, and configured to send the separated liquid of the concentrating device and the dehydrator to a device capable of removing phosphorus. Processing equipment