WO2005058764A1

WO2005058764A1 - Anaerobic digestion apparatus for organic waste liquid

Info

Publication number: WO2005058764A1
Application number: PCT/JP2004/013507
Authority: WO
Inventors: Kazuya Komatsu; Hidenari Yasui
Original assignee: Kurita Water Industries Ltd.
Priority date: 2003-12-16
Filing date: 2004-09-16
Publication date: 2005-06-30
Also published as: TW200521088A; JP2005199258A; JP4507712B2

Abstract

An anaerobic digestion apparatus for an organic waste liquid, wherein a digested sludge from the organic liquid is concentrated and the concentrated sludge is returned to an anaerobic digestion tank and, at the same time, the digested sludge is solubilized and the solubilized sludge is returned to the anaerobic digestion tank, and wherein the concentrated sludge is mixed with the solubilized sludge at the suction side of a transfer pump (4) for transferring the concentrated sludge and is adjusted with respect to its concentration and then returned to the anaerobic digestion tank (1). The above apparatus allows the combination of the smooth return of the concentrated sludge and the enhancement of the concentration ratio for the digested sludge resulting in an efficient concentration of the sludge, and also allows satisfactory dispersion of the returned concentrated sludge in the anaerobic digestion tank resulting in efficient digestion and thus the enhancement of the reduction ratio of the amount of the sludge.

Description

Specification

Anaerobic digester for organic waste liquid

Field of the invention

The present invention relates to an apparatus for anaerobic digestion of an organic waste liquid.

Background art

[0002] A method of digesting organic sludge such as organic sludge, human waste, wastewater from food factories, etc., in the presence of anaerobic microorganisms to reduce the weight of the slurry has been used for a long time. Although the conventional anaerobic digestion method requires a long residence time of 10 days or more, its digestibility (removal rate of organic components) is only 35-50%, and the sludge reduction rate is low. Low.

[0003] Japanese Patent Application Laid-Open No. 9-206785 discloses that an organic waste liquid is subjected to an anaerobic digestion treatment in an anaerobic digestion tank, and then the digested sludge is separated into solid and liquid, and the separated liquid is discharged as treated water. It describes a method for anaerobic digestion of organic waste liquid in which (condensed sludge) is returned to the anaerobic digestion tank, and part of the digested sludge is reformed by ozone treatment and returned to the anaerobic digestion tank. You. In this method, the digested sludge is separated into solid and liquid, and the separated sludge is returned to the anaerobic digestion tank 1 to secure the residence time of the anaerobic microorganisms. By returning to the anaerobic digestion tank after being modified to readily biodegradable, it can be decomposed again as a substrate for anaerobic microorganisms and the digestibility (sludge reduction rate) can be increased.

[0004] In this method, in order to increase the amount of digested sludge (digested sludge containing anaerobic microorganisms) to be reformed by ozone treatment while maintaining the residence time of anaerobic microorganisms for a long time, the sludge in the anaerobic digestion tank is required. It is necessary to increase the concentration to 4.8% compared to 112% in conventional transient anaerobic digestion.

[0005] In this method, a centrifugal concentrator is usually used for solid-liquid separation of digested sludge.

In order to efficiently perform centrifugal concentration of digested sludge, it is preferable to operate the digested sludge at a higher concentration ratio, for example, 2 times or more. When the concentration ratio is low, the processing amount of the centrifugal concentrator required to obtain a certain amount of the separated liquid significantly increases, so that a larger concentrator is required or the operation time of the concentrator needs to be extended. Or require more flocculant. [0006] Adjustment of concentration by a concentrator to a desired concentration ratio requires a high level of operation technology, and if there is a change in conditions, concentration cannot be performed stably to a desired concentration. Concentration by the concentrator is preferably performed at a high concentration ratio that matches the performance of the concentrator.

[0007] Since digested sludge is relatively easily concentrated, high concentration sludge with a TS concentration of 10% or more can be obtained by concentration.

[0008] When the concentration of the concentrated sludge is increased by increasing the concentration ratio, the viscosity of the sludge increases exponentially with respect to the sludge concentration, so that the viscosity of the concentrated sludge significantly increases tl. As a result, it becomes difficult to return the concentrated sludge to the anaerobic digestion tank, a pump with a large power (discharge pressure) is required as a pump for transferring the concentrated sludge, or the returned concentrated sludge is anaerobic. The ability to disperse sufficiently in the digestion tank makes the digestion efficiency lower.

[0009] In the method using digestive sludge solubilization in combination, it is necessary to increase the sludge concentration in the anaerobic digestion tank to 418%, which is higher than in the normal anaerobic digestion method, as described above. is there. When the sludge concentration in the anaerobic digestion tank is increased to 418%, if the concentration ratio is increased to, for example, 2 times or more, the concentration of the concentrated sludge becomes very high, 8-16% or more. The viscosity of the sludge becomes extremely high, and it becomes more difficult to return the concentrated sludge to the anaerobic digestion tank and to disperse the returned concentrated sludge in the anaerobic digestion tank.

[0010] Digested sludge in the anaerobic digestion tank contains reducing inorganic substances such as sulfuric acid, divalent iron and manganese. When reforming digested sludge by ozone treatment, ozone to be used for reforming hardly decomposable organic components is consumed for oxidizing these reducing inorganic substances.

[0011] Organic components in digested sludge are decomposed and reduced by the circulating treatment of reforming and digestion, whereas inorganic components in sludge are not reduced. Therefore, they accumulate in the anaerobic digestion tank and reduce the sludge concentration. To raise. When the sludge concentration increases, the viscosity of the sludge increases, which causes problems such as stirring the anaerobic digestion tank, reforming the digested sludge, and solid-liquid separation. Therefore, the sludge in the anaerobic digestion tank is pulled out and discharged to maintain the sludge concentration in the anaerobic digestion tank within a certain range. At that time, organic components that can be originally decomposed, not only inorganic components that are not decomposed, are discharged out of the system, and the digestibility (sludge reduction rate) does not improve.

Summary of the Invention

[0012] The present invention provides an apparatus for anaerobic digestion of organic waste liquid capable of increasing the sludge loss rate. The purpose is to provide a device.

[0013] The anaerobic digestion treatment apparatus for organic waste liquid of the present invention includes an anaerobic digester for anaerobic digestion of organic waste liquid, and a solubilizer for dissolving the digested sludge extracted from the anaerobic digester. E means, return means for returning the solubilized sludge from the solubilization means to the anaerobic digestion tank, and solid-liquid separation means for concentrating the digested sludge discharged from the anaerobic digestion tank (hereinafter referred to as "concentrator"). And a pipe having a transfer pump for returning the concentrated sludge from the solid-liquid separation means to the anaerobic digestion tank, and V on the transfer pump or on the suction side of the transfer pump. A liquid supply means for adding a liquid to the concentrated sludge.

[0014] "Solubilization of sludge" refers to denaturation and destruction of sludge substances and sludge cells that are hardly assimilated by microorganisms to form a form that can be easily assimilated by microorganisms.

The apparatus for anaerobic digestion of organic waste liquid of the present invention performs anaerobic digestion treatment by performing solubilization of digested sludge and return of solubilized sludge, concentration of digested sludge and return of concentrated sludge. I do. The concentrated sludge with extremely high viscosity is adjusted in concentration with solubilized sludge and returned to the anaerobic digestion tank. The returned sludge is sufficiently dispersed in the anaerobic digestion tank, digested efficiently, and the sludge is significantly reduced.

In the present invention, the digested sludge is concentrated, and the concentrated sludge is returned to the anaerobic digestion tank, so that the SRT (solid residence time) of the anaerobic digestion tank is maintained without changing the HRT (hydraulic residence time). , The digestion efficiency and the weight loss rate can be obtained. By solubilizing the digested sludge to make it easily biodegradable and returning the solubilized sludge to the anaerobic digestion tank, the sludge loss rate can be further increased.

[0017] The sludge concentration in the anaerobic digestion tank in which the digested sludge is soluble is set high. The concentrated sludge obtained by concentrating this relatively high concentration of digested sludge is a paste-like and very viscous liquid, and the pump discharge pressure becomes extremely large when pumped. The highly viscous concentrated sludge disperses in the anaerobic digestion tank 1, which reduces digestion efficiency

. As described above, it is difficult to perform appropriate concentration to such an extent that it can be transferred by a pump, and the efficiency of the concentrator also deteriorates.

[0018] In the present invention, the digested sludge is concentrated without considering the transferability by the pump, and the obtained highly viscous concentrated sludge is mixed with a liquid to dilute the concentrated sludge to a concentration that can be easily transferred by the pump. Adjust the density.

In the present invention, the concentration of the concentrated sludge is adjusted on the transfer pump or on the suction side of the transfer pump, and the concentrated sludge can be easily transferred by the transfer pump.

[0020] In the present invention, the concentrated sludge is adjusted to a concentration suitable for pump transfer by the transfer pump or the suction side of the transfer pump, and is efficiently returned to the anaerobic digestion tank. It is possible to disperse the sludge uniformly and perform efficient anaerobic digestion treatment.

[0021] To reduce the organic matter load by concentrating the digested sludge, extracting the separated liquid containing ammonia out of the system, diluting the concentrated sludge with other waste liquid containing a small amount of ammonia, and returning the diluted sludge to the anaerobic digestion tank. An anaerobic digestion treatment can be performed.

Brief Description of Drawings

FIG. 1 is a system diagram showing an embodiment of an apparatus for anaerobic digestion of organic waste liquid of the present invention.

FIG. 2 is a system diagram showing another embodiment of the organic waste liquid anaerobic digestion treatment apparatus of the present invention.

FIG. 3 is a graph showing the time-dependent changes in sludge concentration and digestibility in an anaerobic digestion tank in Example 1.

FIG. 4 is a graph showing time-dependent changes in sludge concentration and digestibility in an anaerobic digestion tank in Comparative Example 1.

FIG. 5 is a graph showing the change over time in the sludge concentration and digestibility in the anaerobic digestion tank in Example 2.

FIG. 6 is a graph showing the relationship between the TVSZTS ratio of feed sludge and the TVSZTS ratio of discharged sludge (concentrated sludge and supernatant sludge (concentrated separated liquid)) determined in Experimental Example 2.

Preferred description, detailed description of the form

According to one embodiment of the apparatus for anaerobic digestion of organic waste liquid of the present invention, solubilized sludge is used as a diluting liquid for adjusting the concentration of concentrated sludge. As a result, more efficient processing is performed. That is, since the viscosity of the sludge is reduced by the solubilizing treatment, the solubilized sludge is effective for diluting the concentrated sludge. In this case, the dilution liquid itself is also a target for processing. As such, digestion efficiency is improved. When water is added as the diluting liquid, it is necessary to concentrate again to increase digestion efficiency. However, if the soluble sludge is used, the concentration becomes unnecessary. After the solubilized sludge and the concentrated sludge are mixed in advance and returned to the anaerobic digestion tank, the solubilized sludge and the concentrated sludge are more uniformly mixed and dispersed to promote digestion.

[0024] According to another embodiment of the apparatus for anaerobic digestion of organic waste liquid of the present invention, the solubilizing means is an oxidizing means. By this oxidation treatment, digested sludge can be efficiently solubilized.

[0025] According to another embodiment of the apparatus for anaerobic digestion of organic waste liquid of the present invention, digested sludge introduced into the oxidation treatment means is previously aerated by aeration means. Thereby, the reducing inorganic substance contained in the digested sludge is oxidized, and for example, in the ozone treatment means as the oxidation treatment means in the subsequent stage, the ozone force is prevented from being consumed by the oxidation of the reducing inorganic substance, and And the efficiency of the fusible treatment can be increased.

[0026] According to still another embodiment of the apparatus for anaerobic digestion of organic waste liquid of the present invention, an ozone treatment means is adopted as the soluble means. Since the viscosity of the ozone-treated soluble dashi sludge is small, it can be returned to the anaerobic digestion tank in a uniform state while ensuring fluidity. Since it is returned to the anaerobic digestion tank in a uniform state, the digestion efficiency in the anaerobic digestion tank increases. When a drug such as potassium permanganate is added for solubilization, manganese diacid and the like remain in the system, and a chemical injection facility is required. Is converted to oxygen and does not remain in the system, and no chemical injection equipment is required.

[0027] According to still another embodiment of the organic waste liquid anaerobic digestion treatment apparatus of the present invention, the concentrated sludge obtained by centrifugally concentrating the digested sludge without adding a flocculant is discharged out of the system. . As a result, the inorganic component having a higher specific gravity than the organic component can be preferentially discharged out of the system, and the accumulation of the inorganic component in the system can be prevented to increase the digestion efficiency. In addition, sludge containing a large amount of inorganic components is excellent in dewatering properties, so that a low water content can be obtained and a dewatered cake can be obtained.

Hereinafter, an embodiment of an apparatus for anaerobic digestion of organic waste liquid of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show a system showing an embodiment of an apparatus for anaerobic digestion of organic waste liquid of the present invention. FIG. In FIGS. 1 and 2, members having the same functions are denoted by the same reference numerals.

[0030] [Anaerobic digestion treatment apparatus for organic waste liquid in FIG. 1]

In FIG. 1, organic sludge (organic waste liquid) is introduced into an anaerobic digestion tank 1 and subjected to an anaerobic digestion treatment. A part of the digested sludge in the anaerobic digester 1 is withdrawn and concentrated by the concentrator 2. Another part of the anaerobic digestion tank 1 is withdrawn and solubilized by an ozone treatment device 5 as a solubilizing means. At least a part of the solubilized sludge is sent to the mixing tank 3, and the rest is returned to the anaerobic digestion tank 1. The concentrated sludge concentrated by the concentrator 2 is fed to the mixing tank 3 and mixed with the soluble slime from the ozone treatment device 5 to adjust the concentration, and the sludge diluted to a concentration suitable for pump transfer is transferred. Returned to anaerobic digestion tank 1 by pump 4.

[0031] The organic waste liquid to be treated is a waste liquid containing an organic substance which is reduced by the anaerobic digestion treatment, and may be a slurry containing a solid or a liquid containing no solid. . It may contain organic substances, inorganic substances, cellulose, paper, cotton, wool, cloth, and solids in human waste that are hardly biodegradable. Organic waste liquids include sewage, primary sewage sludge, human waste, septic tank sludge, wastewater and residues from food factories, beer waste yeast, other industrial waste liquids, and excess sludge generated when processing these waste liquids. Is mentioned.

[0032] In the anaerobic digestion tank 1, an organic waste liquid is subjected to methane fermentation in the presence of sludge containing anaerobic microorganisms for treatment. Sludge containing anaerobic microorganisms includes acid-producing bacteria and methanogens. In the anaerobic digestion process, organic substances are converted to methane gas by anaerobic microorganisms in the steps of liquefaction → low molecular weight → organic acid generation → methane generation and processed.

[0033] The conditions of anaerobic digestion can be any temperature conditions under which medium-temperature methanogens having an optimum temperature around 35 ° C and high-temperature methanogens having an optimum temperature near 55 ° C grow. is there. Since medium-temperature methanogens grow slowly, it is necessary to lengthen the SRT, that is, to enlarge the anaerobic digestion tank.However, since the treatment can be performed at a relatively low temperature, the equipment for heating and keeping the heat simple. can do. On the other hand, in the case of high-temperature methanogens, heating and warming facilities are required, but because of rapid growth, an anaerobic digestion tank with a short and good SRT can be reduced to / J.

When the mesophilic methanogen is mainly used, the SRT of the sludge in the anaerobic digestion tank needs to be 10 days or more, preferably about 15 to 50 days. On the other hand, mainly high temperature methanogens In this case, it is possible to set the SRT shorter than the above range (2 days or more).

[0035] The organic matter load is 0.2 to 2-3. Okg-TVS / m ³ -day, preferably 0.4 to 0.8 kg—TVS / m 3 · day, and the TS concentration in the anaerobic digestion tank is 1 to 10 The anaerobic digestion treatment can be performed under the conditions of%, preferably 3-6%, and the temperature is 30-38 ° C or 45-60 ° C.

[0036] As the concentrator 2 for condensing digested sludge, a centrifugal concentrator, a flotation concentrator, a screw press concentrator, and a filter that can separate and condense digested sludge by solid-liquid separation can be used. A solid-liquid separation device such as a cloth-type concentrator, a sedimentation tank, a membrane separation device, and a filtration device can also be used, but is not limited thereto.

In concentrating the digested sludge, a coagulant, preferably a polymer coagulant, is added to the digested sludge to coagulate the SS content in the digested sludge, thereby increasing the concentration ratio and increasing the clarity of the separated liquid. Can be obtained. As the flocculant, a known flocculant generally used for concentration and dehydration of digested sludge can be used, but a cationic polymer flocculant is preferable because the amount of addition is small. The polymer flocculant is preferably dissolved in tap water, industrial water, secondary sewage water, etc. at a concentration of about 0.2-0.4% by weight and added at a rate of SS per digested sludge. 0.05-1.5% by weight is preferred. When a coagulant is added to digested sludge, the coagulant can be injected into the digestion sludge transfer line or added to the concentrator, or it can be coagulated by installing a separate coagulation tank.

[0038] The degree of concentration of the digested sludge in the concentrator 2 depends on the performance of the concentrator used. Normally, the digested sludge having a TS (solid matter) concentration of about 3 to 6% is converted into a paste form of about 8 to 20%. Or it is preferred to concentrate to a highly viscous liquid.

[0039] If necessary, the concentrated sludge from the concentrator 2 may be partially discharged to the system as drawn sludge (excess sludge), and may be subjected to dehydration, incineration, landfill, composting, and other disposal. . If the sludge to be discharged has high viscosity, diluting it with a diluting liquid and discharging it will require less power for the discharge pump. As the diluting liquid, treated water (separated liquid of the concentrator 2), biologically treated water of other organic waste liquid, or the like can be used.

[0040] It is preferable that the sludge is extracted such that the sludge (TS) concentration in the anaerobic digestion tank 1 is maintained at 3 to 10%.

[0041] The extracted sludge may be directly discharged from the anaerobic digestion tank 1. [0042] The concentrated separated liquid of the concentrator 2 can be discharged as it is as treated water to a sewer or the like, but may be discharged after aerobic biological treatment or other post-treatment.

[0043] Since the concentrated separated solution contains ammonia, phosphorus, and the like at a high concentration, crystals of magnesium phosphate (MAP) and the like may precipitate in the transfer pipe, and may block the pipe. . In this case, by introducing tap water, industrial water, sewage secondary treatment water, or the like into the concentrated separated liquid, the concentration thereof can be reduced and precipitation can be prevented.

[0044] In the ozone treatment apparatus 5, the digested sludge from the anaerobic digestion tank 1 is made soluble by bringing it into contact with ozone. As a method of contacting with ozone in the ozone treatment apparatus 5, a method of introducing digested sludge into the ozone treatment tank and blowing ozone, a method of mechanical stirring, a method of using a packed bed, and the like can be adopted. As ozone, in addition to ozone-containing gas such as ozone water and ozonized air, ozone-containing water can be used. The amount of ozone used is usually 0.01-0.08 g per VSS of digested sludge that is ozonized. — O Zg— VSS, preferably 0.0

Three

2-0. 05g-O Zg- VSS.

Three

[0045] By performing the ozone treatment, the cells in the digested sludge are killed, and the digested sludge is reformed to be easily biodegradable together with other organic substances. At that time, the viscosity of the sludge is significantly reduced. Part or all of the soluble solubilized sludge solubilized by the ozone treatment device 5 is sent to the mixing tank 3, and the rest (when a part of the solubilized sludge is sent to the mixing tank 3) is anaerobic. Returned to sexual digester 1.

In the mixing tank 3, the concentration of the concentrated sludge from the concentrator 2 is adjusted by adding the solubilized sludge from the ozone treatment device 5. The diluting liquid used for adjusting the concentration of the concentrated sludge includes, in addition to the solubilized sludge, digested sludge, organic sludge of raw sludge (organic waste liquid), treated water (separation liquid of the concentrator 2), and industrial water. Water, secondary effluent from sewage, wastewater from other systems, biologically treated water, etc. can also be used, but preferably soluble slime is used. The concentration of TS in concentrated sludge is usually 8-20%, which is extremely high viscosity. However, the concentration of TS in fusible slime is usually 3-6%, and the viscosity is further reduced by fusible treatment. Therefore, the concentration sludge can be efficiently diluted by such a soluble dani sludge.

To adjust the concentration of the concentrated sludge, it is only necessary to inject the diluting liquid into the suction side of the transfer pump or the transfer pump immediately before the transfer pipe for the concentrated sludge without necessarily providing a mixing tank. However, if the viscosity of the concentrated sludge is high, It is preferable to provide 3 and mix mechanically. As the mixing means, a stirrer, gas blowing, a static mixer, or the like can be used.

[0048] Since the residence time of the mixing tank 3 for adjusting the concentration of the concentrated sludge may be about 1 minute to 6 hours, the volume of the mixing tank 3 may be small. Also, the power required for mixing in the mixing tank 3 is extremely small as compared with the case where the concentrated sludge is directly introduced into the anaerobic digestion tank and mixed with the digested sludge and the raw sludge.

[0049] The concentration of the concentrated sludge is adjusted, for example, to such an extent that it can be smoothly transferred by a single-stage monopump. Generally, the TS concentration is adjusted so that the discharge pressure of the transfer pump 4 becomes 0.4 MPa or less. It is preferable to concentrate to 6-12%, for example, about 8%.

[0050] In the apparatus of Fig. 1, the concentrated sludge concentrated by the concentrator 2 is dropped into the mixing tank 3, and the concentration of the concentrated sludge is adjusted by the solubilized sludge. The sludge whose concentration has been adjusted in this manner can be efficiently returned to the anaerobic digestion tank 1 by the transfer pump 4, and can be efficiently dispersed in the anaerobic digestion tank 1 for efficient anaerobic digestion. Sexually digested.

[0051] The transfer pump 4 for transferring the sludge after the concentration adjustment is not particularly limited, and a mono pump, a hose pump, or the like can be used.

[0052] By extracting a part of the digested sludge in the anaerobic digester 1 and concentrating it with the concentrator 2, adjusting the concentration of the concentrated sludge and returning it to the anaerobic digester 1, the SRT can be changed without changing the HRT. It can be lengthened, which can reduce the sludge loss rate.

[0053] The amount of digested sludge withdrawn from the anaerobic digestion tank 1 for concentration is not particularly limited, but about 1Z30-1Z10 of the sludge retained in the anaerobic digestion tank 1 is extracted, and the concentration and concentration are adjusted. By post-circulation, the SRT can be extended at least about three times or more than in the case where such sludge circulation is not performed, and even if the organic waste liquid is hardly biodegradable, the sludge can be reduced. The dagger can be promoted.

[0054] The amount of digested sludge withdrawn from the anaerobic digestion tank 1 for fusible dung is controlled by the amount of organic solids (VSS ) Is preferably set to an amount corresponding to 1Z3 to 5 times, preferably 1Z2 to 2 times the amount of the organic solids (VSS) introduced into the anaerobic digestion tank 1. The amount of digested sludge to be dissolved per day is 1Z10 or less, preferably 1Z1, of the total amount of organic solids (VSS) in the anaerobic digestion tank 1. It is preferable to set the amount to 00-1 / 15, more preferably 1Z50-1Z30. By setting the amount of the soluble dialysis treatment per day to such an amount, the amount of microorganisms required for the anaerobic digestion treatment can be held in the anaerobic digestion tank 1, and the efficiency of the anaerobic digestion treatment can be improved. Can be kept high.

[0055] In Fig. 1, an ozone treatment device is used as a solubilizing means, but the solubilization treatment is not limited to the ozone treatment device at all, and sludge cells are denatured and destroyed and are easily assimilated by microorganisms. Anything that can be soluble in water is acceptable. Various methods known as a method for solubilizing sludge can be employed. Various methods such as ozone treatment; chemical treatment with strong oxidizing agents such as hydrogen peroxide, or acids and alkalis; physical treatment such as ultrasonic treatment and milling with a mill; and thermal treatment It can be employed alone or in combination of two or more.

[0056] The solubilization treatment may be performed on digested sludge extracted from the anaerobic digestion tank, or may be performed on a part or all of the concentrated sludge obtained by concentrating the digested sludge.

[0057] It is preferable to operate the concentrator and the mixing tank in a state where the air is shut off from the atmosphere. For example, if the concentrator is closed to condense and restrict the contact between sludge and oxygen, anaerobic bacteria Can be returned to the anaerobic digestion tank with vigor, and the viable cell count in the anaerobic digestion tank can be easily maintained and increased, and the digestion efficiency can be improved.

[0058] It is also preferable to use the digestion gas (methane gas) generated in the anaerobic digestion tank effectively to cover the heating of the digestion tank and a part or all of the power required for the solubilizing means and the concentrator.

[0059] [Anaerobic digestion treatment apparatus for organic waste liquid in FIG. 2]

In the anaerobic digestion treatment apparatus for organic waste liquid shown in FIG. 2, the mixing tank 3 is omitted, and the soluble slime from the ozone treatment apparatus 5 is injected into the suction side of the transfer pump 4 to concentrate the sewage sludge from the concentrator 2. Mix with mud. A pre-aeration tank 6 is provided upstream of the ozone treatment apparatus 5, and digested sludge is subjected to an aeration treatment in the pre-aeration tank 6 before ozone treatment. The digested sludge in the anaerobic digestion tank 1 is drawn out, concentrated by the centrifugal concentrator 7, the concentrated sludge is discharged out of the system as drawn sludge, and the separated liquid is injected into the transfer pump 4 on the suction side. Other configurations are the same as those of the apparatus for anaerobic digestion of organic waste liquid shown in FIG.

[0060] The treatment conditions of the pre-aeration tank 6 include the efficiency of air oxidation of reducing inorganic substances in digested sludge. From the viewpoint of good performance, it is preferable that aeration air is blown in at a condition of 0.2-1.0 m ³ Zm ³ 'min, and aeration treatment is performed for a residence time of about 5 minutes to 8 hours. By providing the pre-aeration tank 6 in front of the ozone treatment device 5, the reducing inorganic substances in the digested sludge are subjected to oxidation treatment in advance, and the ozone treatment in the ozone treatment device 5 allows the sludge to be dissolved by the ozone treatment. Can be increased.

[0061] When the ozone gas discharged from the ozone treatment device 5 is used as the aeration air in the preaeration tank 6, the exhaust gas can be effectively used to more efficiently oxidize the reducing inorganic substances in the digested sludge. Can be. The use of ozone ozone as the ozone is effective because the oxygen concentration of the exhaust gas is high.

[0062] By providing the pre-aeration tank 6, the amount of ozone used in the ozone treatment device 5 can be reduced. For example, the digestion sludge introduced into the ozone treatment device 5 is 0.01-0.04 kg. — O Zkg— As a VSS, sludge can be treated efficiently.

Three

[0063] Into the centrifugal concentrator 7, the required amount of digested sludge for maintaining the sludge concentration in the anaerobic digestion tank 1 in the above-mentioned preferred range is introduced without adding a flocculant, and the centrifugal concentrator is introduced. Is done. By centrifugally concentrating the digested sludge without the coagulant, the inorganic components in the digested sludge are preferentially concentrated. By extracting this concentrated sludge to the outside of the system, inorganic components can be preferentially discharged to the outside of the system, preventing accumulation of inorganic components in the system and improving digestion efficiency.

[0064] The extracted sludge is disposed of by dehydration, incineration, landfill, composting, or the like. The extracted sludge has a high content of inorganic components, is excellent in dehydration properties, and is a dewatered cake having a low moisture content, which is advantageous in handling.

In addition to the organic waste liquid anaerobic digestion treatment apparatus shown in FIG. 2, other processing conditions and alternative means are the same as those described for the organic waste liquid anaerobic digestion treatment apparatus shown in FIG. The same is true.

Example

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[0067] The sewage primary sludge and excess sludge were anaerobically digested in a transient manner at 35 ° C. Anaerobic digestion tank capacity ί 1,100m ³ , TVS load ί 0.65kg / m ^3- HRTi 45 (input amount of sludge is 24.4m ³ ) o Input sludge concentration (TS 3.5% (compared to TVSZTS) On the other hand, the digested sludge concentration was 1.6% (73% of TVS ZTS), and the digestibility (TVS weight loss rate) was 60%. In the anaerobic digestion treatment in this anaerobic digestion tank, the sludge in the anaerobic digestion tank is solid-liquid separated and the concentrated sludge is returned to increase the sludge residence time, and the sludge in the tank is solubilized and returned. Thus, an attempt was made to increase the weight loss rate, and a centrifugal concentrator was used as a solid-liquid separation means. In addition, an ozone treatment device was used as a solubilizing means.

[0068] The sludge in the tank is sent to the ozone treatment apparatus at 1.0 m ³ Zhr, and the amount of ozone used is 0.03 kg—O / kg.

Reaction with ozone was performed to obtain 3 VSS. Further, pulling the intracisternal sludge 3. 7m ^3, which corresponds to 15% of the charged amount of sludge, the amount corresponding to 85% the rest was discharged intracisternal sludge out of the system as a partial syneresis when the centrifugal concentration. For centrifugal concentration, the sludge in the tank is fed to the centrifugal concentrator at 2.0 m ³ Zhr, and the cation-based polymer dissolved in 0.2% by weight at a centrifugal strength of 2,100 G and a differential speed of 15 min- ¹ The test was performed while adding a flocculant at 0.6% by weight per SS. At this time, the concentrated sludge concentration was 12%, and the SS recovery rate was 95% or more. When trying to return the concentrated sludge discharged from the centrifugal concentrator to the concentrated sludge receiving tank (mixing tank) to the anaerobic digestion tank with a monopump, the pressure of the monopump reached 0.8 MPa and the pump tripped, causing the sludge to slip. Could not be returned.

Therefore, the processing of the following examples and comparative examples was performed.

Example 1

The concentrated sludge was put into the mixing tank, and a part of the sludge that had been dissolved by the ozone treatment was introduced into the mixing tank and mixed with gentle stirring using a stirrer. Since the pressure was 3.6%, the pressure of the monopump dropped to 0.12MPa, it was possible to quickly return to the anaerobic digestion tank.

[0071] Fig. 3 shows the changes in the sludge concentration in the anaerobic digestion tank and the digestibility obtained from the solid content balance and the amount of digested gas generated when such operation was continued for one year. As shown in FIG. 3, after 5 months from the start of operation, the TVS concentration in the tank changed around 2.3%, and a digestibility of 80% or more was continuously obtained. As the sludge concentration in the tank increased to 4.6%, the concentrated sludge concentration after mixing with the ozone-treated sludge increased to 7.2% Power The pressure of the mono pump was 0.3MPa or less, and it was sent back without difficulty We were able to. Comparative Example 1

The conditions for centrifugal concentration were changed to reduce the pressure so that it could be pumped by a monopump. When the centrifugal strength was reduced to 1, OOOG and the coagulant addition rate was reduced to 0.2% by weight, the concentrated sludge concentration was reduced to about 7%, the pressure of the monopump was reduced to 0.3 MPa, and the anaerobic digester was reduced. Can now be sent back. However, the SS recovery rate at this time was 70%, and sludge flowed to the separation liquid side.

[0073] Fig. 4 shows the transition of the sludge concentration in the anaerobic digestion tank and the digestibility when such operation was continued for one year. As shown in Fig. 4, the SS recovery rate was low, so the sludge concentration in the tank could not be increased even if the operation was continued, and the digestibility could not be increased to 70% or more.

Example 2

Except that the digested sludge from the anaerobic digester was centrifugally concentrated at 4.0 m ³ Zhr, the secondary sewage water was introduced into the mixing tank at 1.0 m ³ / hr, and mixed gently with a stirrer. When the treatment was performed in the same manner as in Example 1, the pressure of the monopump for returning the concentrated sludge was reduced to 0.2 MPa, and the sludge could be immediately returned to the anaerobic digestion tank.

[0075] Fig. 5 shows changes in the sludge concentration in the anaerobic digestion tank and the digestibility when such operation is continued. As shown in Fig. 5, when the TS concentration in the tank exceeded 3.7% after 5 months from the start of operation, the solids load of the centrifugal concentrator became too high and it became impossible to operate. . Therefore, was increased to 6 m ³ Z date corresponding withdrawal of intracisternal sludge 25% of the input amount of sludge, intracisternal TS concentration remained 3. about 7%, it is possible to continue the operation, Digestibility increased to 78%.

Hereinafter, tests showing the solubilizing effect by ozone treatment and the preferential discharge effect of inorganic components by centrifugal concentration without addition of a flocculant will be described.

[0077] Test 1

Ozone reaction rate of digested sludge after ozone treatment of 0.03 kg—O Zkg—VSS

Three

The properties of the sludge before and after the treatment were examined, and the results are shown in Table 1.

[0078] [Table 1] Properties of digested sludge before and after ozone treatment

[0079] As is clear from Table 1, the TS, VS, and total COD concentrations were almost the same before and after ozone treatment.

Cr

However, the concentration of SS and VSS decreased slightly less than 10% compared to before ozone treatment,

Cr

BOD concentration increased. From this result, it is understood that a part of the VSS component in the sludge was converted to a soluble component by the ozone treatment and was easily biodegraded.

[0080] Test 2

To a digested sludge (TS5%), a polymethacrylic acid ester-based polymer dissolved in sewage secondary treatment water at a concentration of 0.2% by weight as a polymer flocculant was added at 0.5% by weight per SS, and decanter centrifugation When supplied to the concentrator at 4 m ³ / hr and centrifugally concentrated at a centrifugal strength of 2100 G, the concentration (TS) and amount of the obtained concentrated sludge and concentrated separated liquid were as shown in Table 2.

When this digested sludge was centrifugally concentrated under the same conditions without adding a flocculant, the concentrations (TS) and amounts of the obtained concentrated sludge and the concentrated separated solution were as shown in Table 2.

[Table 2] Comparison of concentrated sludge and concentrated separated liquid with and without addition of flocculant

Next, several types of digested sludge having different concentrations are centrifuged and concentrated in the same manner as described above without adding a coagulant, and the TVSZTS ratio of the sludge supplied to the centrifugal concentrator and the discharged sludge (concentrated sludge and supernatant sludge ( The relationship between the concentrated separation solution)) and the TVSZTS ratio was examined, and the results are shown in FIG. [0084] As is clear from Fig. 6, the TVSZTS ratio of the concentrated sludge is 0.02-0. 04 lower than the TVSZTS ratio of the supplied sludge, whereas the TVSZTS ratio of the supernatant sludge is about 0.03 higher. Was. This result indicates that inorganic components were preferentially concentrated on the concentrated sludge side.

[0085] Each of the concentrated sludge and the supplied sludge was dewatered with a belt press dehydrator under the same conditions (filtration speed, filter cloth pressure, coagulant addition rate). The dewatered cake of the concentrated sludge is about 5% lower than the dewatered cake of the supplied sludge, and when compared with the same amount of solid matter, the dewatered cake of the concentrated sludge has a smaller dewatered cake amount than the dewatered cake of the supplied sludge. Decreased by 15-20%. From this result, it is clear that concentrated sludge with a high content of inorganic components obtained by centrifugal concentration without adding a flocculant has excellent dewatering properties.

Claims

The scope of the claims

[1] an anaerobic digester for anaerobic digestion of organic wastewater,

Anaerobic digestion tank power soluble means for solubilizing the extracted digested sludge; and return means for returning the soluble eh sludge of the soluble ionic means power to the anaerobic digestion tank. A pipe having a solid-liquid separation means for condensing digested sludge discharged from the anaerobic digestion tank, and a transfer pump for returning the concentrated sludge from the solid-liquid separation means to the anaerobic digestion tank;

A liquid supply means for adding liquid to the concentrated sludge at the transfer pump or on the suction side of the transfer pump;

An anaerobic digestion treatment apparatus for organic waste liquid, comprising:

[2] The anaerobic digestion treatment apparatus for organic waste liquid according to claim 1, wherein the liquid added to the concentrated sludge is the solubilized sludge.

[3] The apparatus for anaerobic digestion of organic waste liquid according to claim 1, wherein the solubilizing means is an oxidizing means.

[4] The apparatus for anaerobic digestion of organic waste liquid according to claim 3, further comprising an aeration means for aerating the digested sludge extracted from the anaerobic digestion tank in a stage preceding the oxidation treatment means.

[5] The apparatus for anaerobic digestion of organic waste liquid according to claim 3, wherein the oxidation treatment means is an ozone treatment means.

[6] The centrifugal concentration means for concentrating digested sludge discharged also from the anaerobic digester tank without adding a coagulant, and at least one of the concentrated sludge of the centrifugal concentration means according to claim 1. An anaerobic digestion treatment apparatus for organic waste liquid, characterized by having a sludge discharge means for discharging a part out of the system.