WO2014030583A1

WO2014030583A1 - System and method for treating wastewater containing suspended organic substance

Info

Publication number: WO2014030583A1
Application number: PCT/JP2013/071906
Authority: WO
Inventors: 智子松▲崎▼
Original assignee: 株式会社クボタ
Priority date: 2012-08-24
Filing date: 2013-08-14
Publication date: 2014-02-27
Also published as: IN2014DN10992A; JP5968723B2; JP2014042857A; CN104271516A; PH12014502879A1

Abstract

A system for efficiently treating a wastewater which contains suspended organic substances in a high concentration, the system being equipped with: a suspended-organic-substance separator (10) which separates the suspended organic substances from the water to be treated; an anaerobic sludge digester (20) which anaerobically digests the suspended organic substances separated by the suspended-organic-substance separator (10); a device (30) for conversion into nitrous acid , the device (30) oxidizing the ammonia contained in the digested liquid from the anaerobic sludge digester (20) into nitrous acid under aerobic conditions; an autotrophic denitrification device (40) whereby the ammonia contained in the treated liquid from the device (30) for conversion into nitrous acid is oxidized into nitrogen gas under anaerobic conditions with an autotrophic denitrifying microorganism; and a first transfer route (R1) through which the separated liquid from which the suspended organic substances have been removed in the suspended-organic-substance separator (10) is supplied to the device (30) for conversion into nitrous acid.

Description

Suspended organic matter-containing wastewater treatment system and treatment method

The present invention relates to a treatment system and a treatment method for suspending organic substance-containing wastewater, and particularly to a treatment system and a treatment method suitable for wastewater containing a high concentration of suspending organic matter.

Conventionally, when treating wastewater containing a high concentration of suspended organic matter, the suspended organic matter is first separated and removed from the wastewater, and then the separated solution is treated in a biological treatment process such as nitrification denitrification. The method has been adopted. Suspended organic substances separated and removed from wastewater are dehydrated as they are, or disposed after anaerobic digestion for the purpose of weight reduction and methane gas recovery. And the dehydrated filtrate and digestive juice which generate | occur | produce in the case of these processes are returned to a biological treatment process, and are processed with a separated liquid.

The nitrification denitrification method is a nitrification process in which ammonia nitrogen in wastewater is oxidized to nitrite nitrogen by ammonia oxidizing bacteria, and nitrite nitrogen is oxidized to nitrate nitrogen by nitrite oxidizing bacteria, This is a method of decomposing ammonium nitrogen in waste water into nitrogen molecules through a denitrification step of decomposing nitrate nitrogen into nitrogen molecules by heterotrophic denitrifying bacteria.

However, in such a conventional biological nitrification denitrification method, a large amount of oxygen is required in the nitrification process, and the power cost required for a blower fan or the like for aeration rises. As a source of organic carbon in the denitrification process It is necessary to add a large amount of methanol, etc., and the cost of chemicals for that purpose increases, and the amount of sludge generated due to the use of heterotrophic denitrifying microorganisms increases the cost of surplus sludge treatment. There was a problem that the cost increased.

Therefore, in Patent Document 1, solid-liquid separation means for solid-liquid separation of a target treatment liquid containing SS organic substances and ammonia nitrogen, and anaerobic digestion treatment of the separated sludge separated by the solid-liquid separation means. A denitrification treatment by mixing a digestion tank, a nitritation tank for nitrifying the treatment liquid of the anaerobic digestion tank, and a nitrating liquid of the nitritation tank and a separation liquid of the solid-liquid separation means A biological nitrogen removal system with a nitrogen bath has been proposed.

The biological nitrogen removal system anaerobically digests the separated sludge obtained by solid-liquid separation of the target treatment liquid containing SS organic matter and ammonia nitrogen, and then treats the treatment liquid obtained by anaerobic digestion. This is a system that denitrifies a nitrifying solution that has been subjected to nitritation treatment and a separation solution obtained by solid-liquid separation of the target treatment solution by anaerobic ammonia oxidation treatment.

Japanese Patent Laid-Open No. 2003-245687

Anaerobic ammonia oxidation treatment is expressed by the following formula using ammonia nitrogen by an autotrophic denitrifying microorganism (autotrophic denitrifying bacteria) as an electron donor and nitrite nitrogen as an electron acceptor under anaerobic conditions. As described above, 1 equivalent of ammonia nitrogen and 1.32 equivalent of nitrite nitrogen are converted into nitrogen molecules by denitrification reaction. At this time, 0.26 equivalent of nitric acid is produced.
_{^{_{^{NH 4 + + 1.32NO 2 - +}}}} 0.066HCO 3 - + 0.13H + →
_{_{^{1.02N 2 + 0.26NO 3 - + 0.066CH}}} 2 O 0.5 N 0.15 + 2.03H 2 O

When waste water containing high-concentration suspended organic matter is treated with the biological nitrogen removal system described in Patent Document 1, a large amount of separated sludge separated in the settling tank is subjected to anaerobic digestion treatment, resulting in a high concentration. Ammonia is generated. The generated ammonia is nitritized in a nitrification tank, and anaerobic ammonia oxidation treatment is performed in a denitrification tank together with a separation liquid in a precipitation tank, followed by denitrification.

However, in the biological nitrogen removal system, when the nitrite concentration (free nitrous acid concentration) in the nitrification tank becomes high, the activity of ammonia oxidizing bacteria is inhibited and the efficiency of the nitrification reaction decreases. And, as a result of a large amount of ammonia nitrogen that has not been nitritized in the nitrification tank flowing into the denitrification tank, the ammonia nitrogen is excessive with respect to the nitrite nitrogen in the denitrification tank, and ammonia that cannot be treated leaks. There was a problem.

In view of the above-mentioned problems, the object of the present invention is to enable more efficient treatment than the prior art. Furthermore, even wastewater containing a high concentration of suspending organic matter can be more efficiently suspended. It is in the point which provides the processing system and processing method of organic matter containing wastewater.

In order to achieve the above-mentioned object, the first characteristic configuration of the treatment system for waste water containing suspended organic matter according to the present invention contains the suspended organic matter as described in claim 1 of the claims. Suspended organic matter separator for separating suspended organic matter from water to be treated, sludge anaerobic digester for anaerobically digesting suspended organic matter separated by the suspended organic matter separator, and sludge anaerobic A nitrifier that oxidizes ammonia contained in the digestive juice of the digester into nitrous acid under aerobic conditions, and ammonia contained in the treatment liquid of the nitrifier by an autotrophic denitrifying microorganism under anaerobic conditions A suspension system containing suspending organic matter-containing wastewater having an autotrophic denitrification device that oxidizes to nitrogen gas, wherein the suspending organic matter is removed by the suspending organic matter separation device or the separation solution Biological treatment The processing solution in that it includes a first transport path for supplying the nitrite apparatus.

Suspended organic matter separated from the water to be treated by the suspended organic matter separator is anaerobically digested by the sludge anaerobic digester. A digestion solution containing ammonia by anaerobic digestion is introduced into a nitritation device and oxidized to nitrous acid under aerobic conditions, and a treatment solution containing ammonia and nitrite is introduced into an autotrophic denitrification device. In the autotrophic denitrification device, the anaerobic ammonia oxidation treatment uses ammonia nitrogen contained in the treatment liquid as an electron donor and nitrite nitrogen as an electron acceptor under anaerobic conditions. Nitrogenized. When ammonia is oxidized to nitrite in the nitrifier, if the nitrous acid concentration (free nitrous acid concentration) is higher than the specified concentration, the activity of ammonia-oxidizing bacteria is inhibited and the efficiency of the nitrification reaction decreases. However, the efficiency of the denitrification process is lowered by the autotrophic denitrification apparatus at the latter stage.

However, even in such a situation, the separation liquid from which the suspended organic matter is removed by the suspended organic matter separation apparatus or the treatment liquid obtained by biologically treating the separated liquid is transferred to the nitrous acid via the first transfer path. The nitrite concentration (free nitrous acid concentration) in the nitrification solution in the nitrification device is adjusted to a concentration suitable for ammonia nitritation treatment so that the nitrification reaction is promoted. become. In addition, according to such a structure, it is not necessary to prepare the separate dilution water supply equipment using a tap water etc., and it can accelerate | stimulate a nitritation reaction, without performing special temperature control and pH control. it can. Energy costs such as tap water and electricity, and chemical costs can be saved.

As described in claim 2, the second characteristic configuration includes, in addition to the first characteristic configuration described above, a separation liquid of the suspension organic substance separation device or a treatment liquid obtained by biologically treating the separation liquid. It is in the point provided with the 2nd transfer route which supplies to an autotrophic denitrification apparatus.

In the autotrophic denitrification apparatus, ammonia contained in the treatment liquid of the nitritation apparatus is oxidized to nitrogen gas by the autotrophic denitrification microorganisms under anaerobic conditions. However, when the nitrous acid concentration (free nitrous acid concentration) of the treatment liquid introduced into the autotrophic denitrification apparatus is increased, the treatment efficiency of the anaerobic ammonia oxidation treatment is lowered.

However, even in such a situation, the separation liquid from which the suspending organic matter is removed by the suspending organic matter separation device or the treatment liquid obtained by biologically treating the separation liquid is passed through the second transfer path. Since the nitrous acid concentration (free nitrous acid concentration) of the treatment liquid in the autotrophic denitrification device is a concentration suitable for anaerobic ammonia oxidation treatment, the autotrophic denitrification device The inner treatment liquid is diluted, and efficient anaerobic ammonia oxidation treatment is promoted. Similarly, according to such a configuration, it is not necessary to prepare a separate dilution water supply facility using tap water or the like.

In addition to the first or second characteristic configuration described above, the third characteristic configuration is characterized in that the denitrification liquid treated by the autotrophic denitrification device is the autotrophic denitrification as described in claim 3. It is in the point provided with the 3rd transfer route which returns to a nitrogen device.

Even if it is not possible to dilute the nitrous acid concentration (free nitrous acid concentration) of the treatment liquid in the autotrophic denitrification apparatus to an appropriate value by adding the above-mentioned separation liquid or the treatment liquid obtained by biologically treating the separation liquid, Since the denitrification liquid that has been processed by the autotrophic denitrification device and the concentration of nitrous acid has been reduced is returned to the autotrophic denitrification device via the third transfer route, the processing in the autotrophic denitrification device Further dilution is possible so that the nitrous acid concentration (free nitrous acid concentration) of the liquid becomes an appropriate value. Similarly, according to such a configuration, it is not necessary to prepare a separate dilution water supply facility using tap water or the like.

In the fourth feature configuration, as described in claim 4, in addition to the first or second feature configuration described above, nitric acid contained in the denitrification solution of the autotrophic denitrification apparatus is subjected to anaerobic conditions. And a heterotrophic denitrification device that reduces the nitrogen to the nitrogen gas by the heterotrophic denitrification microorganism, and a denitrification solution treated by the heterotrophic denitrification device is returned to the autotrophic denitrification device. It is in the point equipped with.

The nitric acid is contained in the denitrification liquid that has been subjected to anaerobic ammonia oxidation treatment in the autotrophic denitrification apparatus. By introducing such a denitrification liquid into the heterotrophic denitrification apparatus, the nitric acid contained in the denitrification liquid is reduced to nitrogen gas by the heterotrophic denitrification microorganisms under anaerobic conditions. Since the denitrification liquid processed in the heterotrophic denitrification apparatus is returned to the autotrophic denitrification apparatus via the fourth transfer route, the concentration of nitrous acid in the treatment liquid in the autotrophic denitrification apparatus ( It can be further diluted so that the concentration of free nitrous acid becomes an appropriate value.

The first characteristic configuration of the method for treating suspending organic substance-containing wastewater according to the present invention is the suspending property for separating the suspending organic substance from the water to be treated containing the suspending organic substance as described in claim 5. Organic matter separation treatment, sludge anaerobic digestion treatment for anaerobically digesting suspended organic matter separated by the suspension organic matter separation treatment, and ammonia contained in the digested liquid by the sludge anaerobic digestion treatment under aerobic conditions A nitrite treatment that oxidizes to nitrous acid, and an autotrophic denitrification treatment that oxidizes ammonia contained in the treatment solution by the nitrite treatment to nitrogen gas by an autotrophic denitrifying microorganism under anaerobic conditions. A suspending organic matter-containing wastewater treatment method to be performed, wherein the separation liquid from which the suspended organic substances have been removed by the suspension organic substance separation treatment or the treatment liquid in which the separation liquid has been biologically treated is used as the nitritation treatment. And said autotrophic Was transferred to a denitrification process, it lies in regulating the free nitrous acid concentration at each step.

The second characteristic configuration includes a suspending organic matter separation treatment for separating the suspending organic matter from the water to be treated containing the suspending organic matter, and the suspending organic matter separation treatment as described in claim 6. Sludge anaerobic digestion treatment for anaerobically digesting suspended organic matter separated by the above, and nitritation treatment for oxidizing ammonia contained in the digested liquid by the sludge anaerobic digestion treatment to nitrous acid under aerobic conditions; A method of treating wastewater containing suspended organic matter, comprising: autotrophic denitrification treatment in which ammonia contained in the treatment solution by the nitritation treatment is oxidized to nitrogen gas by an autotrophic denitrification microorganism under anaerobic conditions. Then, the separation liquid from which the suspended organic substances have been removed by the suspension organic substance separation treatment or the treatment liquid obtained by biologically treating the separation liquid is transferred to the nitritation treatment, and the treatment liquid or the separation liquid and the Both treatment liquids Transferred to serial autotrophic denitrification treatment lies in that mediate the release nitrite concentration at each step.

In the third feature configuration, as described in claim 7, in addition to the first or second feature configuration described above, the nitritation step adjusts the free nitrous acid concentration to less than 0.2 ppm. However, the step of the autotrophic denitrification treatment is to adjust the free nitrous acid concentration to less than 0.08 ppm.

In the nitritation process, the ammonia is efficiently nitrified by adjusting the free nitrous acid concentration to less than 0.2 ppm. In the autotrophic denitrification process, the anaerobic ammonia oxidation process can be efficiently performed by adjusting the free nitrous acid concentration to less than 0.08 ppm. That is, nitrogen can be removed efficiently even with wastewater containing a high concentration of suspended organic matter.

As described above, according to the present invention, more efficient treatment than the prior art is possible, and even wastewater containing a high concentration of suspended organic matter contains more efficient suspended organic matter. A wastewater treatment system and treatment method can be provided.

FIG. 1 (a) is an explanatory view of the first embodiment of the treatment system according to the present invention, and FIG. 1 (b) is such that the ammonia nitrogen concentration and nitrite nitrogen concentration of the anaerobic digestion liquid are 1: 1.32. It is explanatory drawing of the free nitrous acid density | concentration when it nitrites. FIG. 2 is an explanatory diagram of a second embodiment of the processing system according to the present invention. FIG. 3 is an explanatory diagram of a third aspect of the processing system according to the present invention. FIG. 4 is an explanatory diagram of a fourth aspect of the processing system according to the present invention. FIG. 5 is an explanatory diagram of a fifth aspect of the processing system according to the present invention. FIG. 6 is an explanatory diagram of a sixth aspect of the processing system according to the present invention. FIG. 7 is an explanatory diagram of a numerical simulation of the processing system according to the present invention. FIG. 8 is an explanatory diagram of a numerical simulation of the processing system according to the present invention.

Hereinafter, embodiments of a treatment system and a treatment method for suspending organic substance-containing wastewater according to the present invention will be described.

FIG. 1 (a) shows a treatment system for waste water containing suspended organic substances according to the first embodiment. The said processing system is a system which purifies the to-be-processed water containing suspended organic substance, suspended organic substance separation apparatus 10, sludge anaerobic digester 20, nitritation apparatus 30, and autotrophic desorption. A nitrogen device 40 and a first transfer path R1 are provided.

In the suspension organic matter separation device 10, the suspension organic matter contained in the water to be treated is separated, and in the sludge anaerobic digestion device 20, the suspension organic matter separated in the suspension organic matter separation device 10 is anaerobic digestion. Is done.

In the nitrification apparatus 30, ammonia contained in the digestion liquid of the sludge anaerobic digestion apparatus 20 is oxidized to nitrous acid under aerobic conditions. In the autotrophic denitrification apparatus 40, the treatment liquid of the nitritation apparatus 30 is used. The contained ammonia and nitrous acid are converted to nitrogen gas by autotrophic denitrifying microorganisms under anaerobic conditions. Then, the separated liquid from which the suspended organic matter has been removed by the suspended organic matter separation device 10 is supplied to the nitritation device 30 via the first transfer path R1.

The suspending organic matter separation device 10 can be configured by any of a precipitation device, a coagulation precipitation device, a flotation separation device, a screen device, a membrane separation device, a cyclone device, and a mechanical separation device such as a screw press or a decanter. Further, these devices can be combined.

The suspended organic matter separated from the water to be treated by the suspended organic matter separation device 10 is anaerobically digested by the sludge anaerobic digester 20 to become a digestive liquid containing ammonia nitrogen.

The digested liquid containing ammonia nitrogen charged into the nitritation apparatus 30 is subjected to nitritation treatment by nitrite bacteria under aerobic conditions, and a part of the ammonia nitrogen is oxidized to nitrite nitrogen. .

The treatment liquid of the nitritation apparatus 30 charged into the autotrophic denitrification apparatus 40, that is, the treatment liquid containing ammonia nitrogen and nitrite nitrogen, is converted to ammonia nitrogen by the autotrophic denitrification microorganisms under anaerobic conditions. It is denitrified by an anaerobic ammonia oxidation treatment using an electron donor and nitrite nitrogen as an electron acceptor. That is, the autotrophic denitrification device 40 is an anaerobic ammonia oxidation device.

The autotrophic denitrifying microorganisms are held in the autotrophic denitrification apparatus 40 in the form of airborne bacteria and fixed by immobilizing the biofilm adhered to the filler or the autotrophic denitrifying microorganisms on the immobilizing material. It can also be held in the autotrophic denitrification apparatus 40 as a nitrifying carrier.

When a biofilm in which autotrophic denitrifying microorganisms are adhered to the filler is adopted, the biofilm filling amount into autotrophic denitrification apparatus 40 is preferably 20 to 80% by volume in the case of a fixed bed type. As the filler, a material such as a nonwoven fabric, a plastic material, a sponge material, or porous ceramics can be used, and various shapes such as a plate shape, a granular shape, and a cylindrical shape can be adopted.

When adopting an immobilization carrier in which autotrophic denitrifying microorganisms are immobilized on an immobilizing material, two methods of adhesion immobilization and entrapping immobilization are used for immobilizing autotrophic denitrifying microorganisms on the immobilizing material. Can be adopted.

In the case of adopting adhesion fixation, in addition to a carrier such as a sphere or cylinder, a string material, a gel material, or a nonwoven material can be adopted, and a material with many irregularities that easily attach microorganisms is used as a carrier. It is preferable to adopt.

When employing entrapping immobilization, it is common to employ a method in which microorganisms to be immobilized and monomers or prepolymers as carriers are mixed and then polymerized to entrapped and immobilize microorganisms.

As the monomer material, acrylamide, methylenebisacrylamide, triacryl formal and the like can be preferably used, and as the prepolymer material, polyethylene glycol diacrylate and polyethylene glycol methacrylate can be preferably used. If an immobilizing material with many irregularities is employed in the same manner as the above-described adhesion fixing, the contact efficiency with the water to be treated is good and the denitrification ability is improved.

As described above, the anaerobic ammonia oxidation process performed in the autotrophic denitrification apparatus 40 is a process of converting 1 equivalent of ammonia nitrogen and 1.32 equivalents of nitrite nitrogen into nitrogen molecules by a denitrification reaction. It is. Therefore, in order to efficiently perform the anaerobic ammonia oxidation treatment, ideally, the nitritation treatment is preferably performed in the nitritation apparatus 30 so that the molar ratio of ammonia to nitrous acid is 1: 1.32. .

That is, since the digested liquid obtained by digesting the high-concentration suspended organic substance contains high-concentration ammonia nitrogen, the nitrite concentration (free nitrous acid concentration) in the nitritation apparatus 30 tends to increase. is there.

In nitrification, it is said that all nitrifying bacteria are inhibited when the free nitrite concentration (FNA) is 0.2 ppm or more. According to the calculation formula of Anthonisen et al., The free nitrous acid concentration (FNA) is expressed by the following formula. That is, the free nitrous acid concentration (FNA) is determined by the nitrous acid concentration, temperature, and pH.

FIG. 1 (b) shows the calculation of the free nitrous acid concentration based on the above equation when the nitrous acid concentration of the anaerobic digestion solution is 1: 1.32. The value is shown.

When the concentration of ammonia nitrogen in the anaerobic digestive liquid is 1000 ppm, nitritation is performed so that the concentration of nitrite nitrogen is 570 ppm. At this time, if the pH is 7.4 and the water temperature is 30 ° C., the concentration of free nitrous acid becomes 0.151 ppm, and nitritation is not hindered. However, when the pH is lowered to 7.2, the concentration of free nitrous acid becomes 0.239 ppm, resulting in a concentration that hinders nitritation.

Conventionally, an alkali agent has been added to increase the pH. However, according to the treatment system of the first aspect, the separation liquid is supplied to the nitritation apparatus 30 via the first transfer path R1. By diluting so that the nitrite nitrogen concentration is about 470 ppm, the free nitrite concentration can be brought to a level that does not hinder nitritation.

When the water temperature reaches 15 ° C, the free nitrous acid concentration becomes 0.224 ppm, but maintaining a good state for nitritation by diluting the nitrite nitrogen concentration to about 500 ppm without increasing the water temperature. Can do.

When the concentration of ammonia nitrogen in the anaerobic digestion solution reaches 2000 ppm, the free nitrous acid concentration becomes 0.302 ppm at a pH of 7.4 and a water temperature of 30 ° C. At this time, if the pH is adjusted to 7.6 or the water temperature is adjusted to 48 ° C., the concentration of free nitrous acid can be controlled to be less than 0.2 ppm. For this purpose, a large amount of alkaline agent and enormous energy for heating are required. . However, according to the treatment system of the first aspect, by diluting the nitrite nitrogen concentration to about 740 ppm, the free nitrite concentration can be brought to a level that does not hinder nitritation.

In this way, the separation liquid is supplied to the nitritation apparatus 30 via the first transfer path R1 to dilute the digestion liquid in the nitritation apparatus 30 so that the digestion liquid in the nitritation apparatus 30 is diluted. The nitrous acid concentration (free nitrous acid concentration) can be adjusted to a concentration suitable for ammonia nitritation.

In FIG. 1A, an example in which the diluent supplied to the nitritation device 30 via the first transfer path R <b> 1 is a separation solution from which the suspended organic matter has been removed by the suspended organic matter separation device 10. As described above, when a biological treatment apparatus for biologically treating the separation liquid using aerobic microorganisms is provided, nitrous acid is used as a dilution liquid instead of the separation liquid. It may be supplied to the conversion apparatus 30. This aspect will be described in detail later.

The nitrifying apparatus 30 can efficiently nitrify ammonia without being inhibited by the ammonia oxidizing bacteria, and the nitrifying apparatus 30 can sufficiently nitrify ammonia.

The treatment liquid of the nitrite treatment device 30 is efficiently anaerobic ammonia oxidation treatment and denitrification treatment by the autotrophic denitrification device 40. Since the separation liquid or a treatment liquid obtained by biological treatment of the separation liquid is used to adjust the nitrous acid concentration (free nitrous acid concentration) of the digestion liquid, a separate dilution water supply device such as tap water is prepared. There is no need to do. Electricity costs and chemical costs for temperature control and pH control for efficient nitritation reaction can be saved.

With the above-described configuration, the suspension organic matter separation treatment for separating the suspension organic matter from the water to be treated containing the suspension organic matter and the suspension organic matter separated by the suspension organic matter separation treatment are anaerobically digested. Sludge anaerobic digestion treatment, nitritation treatment that oxidizes ammonia contained in digestion fluid by sludge anaerobic digestion treatment to nitrous acid under aerobic conditions, and ammonia contained in treatment solution by nitritation treatment under anaerobic conditions Under the condition, autotrophic denitrification treatment that oxidizes to nitrogen gas by autotrophic denitrification microorganisms was performed, and the separated organic solution from which suspended organic matter was removed by the suspension organic matter separation treatment or the separated solution was biologically treated The treatment liquid is transferred to nitritation treatment, and a method for treating suspended organic matter-containing wastewater that adjusts the free nitrous acid concentration in the nitritation treatment step is executed.

FIG. 2 shows the processing system of the second aspect. In addition to the processing system of the first aspect described above, the processing system includes a second transfer path R2 that supplies the separation liquid to the autotrophic denitrification apparatus 40.

As described above, in the autotrophic denitrification apparatus 40, ammonia nitrogen is used as an electron donor by the autotrophic denitrification microorganisms under anaerobic conditions with respect to the treatment liquid of the nitritation apparatus 30, and nitrite nitrogen is converted. Denitrification is performed by anaerobic ammonia oxidation treatment as an electron acceptor. At this time, if the concentration of nitrous acid (free nitrous acid concentration) in the autotrophic denitrification apparatus 40 is high, the efficiency of the anaerobic ammonia oxidation treatment is lowered.

By supplying the separation liquid to the autotrophic denitrification apparatus 40 through the second transfer path R2, the processing liquid in the autotrophic denitrification apparatus 40 is diluted, and the nitrous acid concentration (free nitrous acid concentration) of the processing liquid is It is adjusted to a concentration suitable for anaerobic ammonia oxidation treatment. Accordingly, the autotrophic denitrification apparatus 40 can efficiently perform anaerobic ammonia oxidation treatment. Since it is the structure which adjusts nitrous acid concentration (free nitrous acid concentration) using a separated liquid, it is not necessary to prepare separate dilution water supply facilities, such as tap water.

In other words, suspended organic matter separation treatment that separates suspended organic matter from water to be treated containing suspended organic matter, and sludge anaerobic that digests suspended organic matter separated by suspended organic matter separation treatment Nitrite treatment that oxidizes ammonia contained in digestion solution by digestion treatment and sludge anaerobic digestion to nitrous acid under aerobic conditions, and anaerobic condition of ammonia and nitrite contained in treatment solution by nitrite treatment Under the autotrophic denitrification microorganism, the autotrophic denitrification process that converts it to nitrogen gas was performed, and the suspended organic matter was removed by the suspension organic matter separation treatment or the separated solution was biologically treated. A treatment method for wastewater containing suspended organic substances is performed, wherein the treatment liquid is transferred to nitritation treatment and autotrophic denitrification treatment, and the concentration of free nitrous acid in each treatment step is adjusted. .

In the nitrification process, the free nitrous acid concentration is preferably adjusted to less than 0.2 ppm, and the autotrophic denitrification process is preferably adjusted to a free nitrous acid concentration of less than 0.08 ppm. Less than is more preferable. In the nitritation process, ammonia is efficiently nitrified by adjusting the free nitrous acid concentration to less than 0.2 ppm. In the autotrophic denitrification process, the anaerobic ammonia oxidation process can be efficiently performed by adjusting the free nitrous acid concentration to less than 0.08 ppm. That is, nitrogen can be removed efficiently even with wastewater containing a high concentration of suspended organic matter.

FIG. 3 shows the processing system of the third aspect. In addition to the processing system of the second aspect described above, the processing system includes a third transfer path R3 that returns the denitrification liquid processed by the autotrophic denitrification device 40 to the autotrophic denitrification device 40. It is characterized by that. Note that the second transfer path R2 is not necessarily provided.

The dilution of the processing liquid in the autotrophic denitrification apparatus 40 may not be sufficient only by supplying the separation liquid via the first transfer path R1 and the second transfer path R2. Even in such a case, the denitrification liquid treated by the autotrophic denitrification apparatus 40 is returned to the autotrophic denitrification apparatus 40 through the third transfer route R3, so that the inside of the autotrophic denitrification apparatus 40 The treatment liquid can be further diluted. Therefore, the nitrite concentration (free nitrous acid concentration) of the treatment liquid in the autotrophic denitrification device 40 can be reliably adjusted without supplying dilution water to the autotrophic denitrification device 40 from outside the system. Can be done.

In addition, untreated nitrous acid and ammonia remain in addition to nitric acid in the denitrification liquid treated by the autotrophic denitrification apparatus 40. A sensor for measuring nitrite ions and ammonia ions is provided in the autotrophic denitrification device 40, and the denitrification liquid discharged from the autotrophic denitrification device 40 to the outside of the system according to the remaining nitrous acid and ammonia. It is preferable to adjust the return amount so as to satisfy the discharge standard.

In other words, suspended organic matter separation treatment that separates suspended organic matter from water to be treated containing suspended organic matter, and sludge anaerobic that digests suspended organic matter separated by suspended organic matter separation treatment Nitrite treatment that oxidizes ammonia contained in digestion solution by digestion treatment and sludge anaerobic digestion to nitrous acid under aerobic conditions, and anaerobic condition of ammonia and nitrite contained in treatment solution by nitrite treatment Under the autotrophic denitrification microorganisms, autotrophic denitrification treatment that converts to nitrogen gas is performed, and the separated liquid from which suspended organic substances have been removed by the suspension organic matter separation treatment is transferred to nitritation treatment, The treatment liquid or both of the separation liquid and the treatment liquid are transferred to an autotrophic denitrification treatment, and a method for treating suspending organic substance-containing wastewater that adjusts the concentration of free nitrous acid in each treatment step is executed. The

FIG. 4 shows a processing system according to the fourth aspect. In addition to the treatment system of the second aspect described above, the treatment system reduces nitric acid contained in the denitrification liquid of the autotrophic denitrification apparatus 40 to nitrogen gas by heterotrophic denitrification microorganisms under anaerobic conditions. A heterotrophic denitrification apparatus 50 is provided, and a fourth transfer path R4 for returning the denitrification liquid processed by the heterotrophic denitrification apparatus 50 to the autotrophic denitrification apparatus 40 is provided. In addition, you may provide 5th transfer path | route R5 which supplies the separation liquid of the suspension organic substance separation apparatus 10 to the heterotrophic denitrification apparatus 50. FIG. Further, the second transfer path R2 is not necessarily provided.

In the heterotrophic denitrification apparatus 50, a denitrification reaction by a heterotrophic denitrification microorganism using nitrate nitrogen generated by anaerobic ammonia oxidation treatment as an electron acceptor and organic matter dissolved in the separation liquid as an electron donor. The amount of nitric acid and organic matter discharged from the autotrophic denitrification apparatus 40 to the outside of the system can be reduced by advancing the process.

Here, it is ideal that the molar ratio of ammonia and nitrous acid is adjusted to 1: 1.32 in the nitritation apparatus 30, but anaerobic ammonia oxidation is performed in the heterotrophic denitrification apparatus 50 in the subsequent stage. Since the nitrite remaining in the reaction can be denitrified by the heterotrophic denitrifying microorganism, the nitritation apparatus 30 may be adjusted so that the nitrous acid is larger than the molar ratio of 1.32 with ammonia. In some cases, nitrification may proceed to nitric acid. However, in order to increase the efficiency of denitrification and reduce the amount of oxygen required for nitrification, it is desirable that ammonia: nitrous acid is adjusted to about 1: 1.32 to 1.5 in the nitritation apparatus 30.

By returning the denitrification liquid denitrified by the heterotrophic denitrification apparatus 50 through the fourth transfer route R4 to the autotrophic denitrification apparatus 40, the treatment liquid in the autotrophic denitrification apparatus 40 is further diluted. can do. Therefore, the nitrite concentration (free nitrous acid concentration) of the treatment liquid in the autotrophic denitrification apparatus 40 can be adjusted reliably.

The heterotrophic denitrification apparatus 50 is charged with heterotrophic denitrification microorganisms and is maintained in an anaerobic atmosphere. The retention form of the heterotrophic denitrification microorganisms in the heterotrophic denitrification apparatus 50 is the same retention form as the autotrophic denitrification microorganisms in the autotrophic denitrification apparatus 40 described in the processing system of the first aspect. Can be adopted. When the organic substance contained in the denitrification liquid processed by the autotrophic denitrification apparatus 40 is insufficient, the heterotrophic denitrification apparatus 50 is separated into the suspended organic substance separation apparatus 10 via the fifth transfer path R5. By supplying, the lack of organic matter can be compensated.

In the processing systems of the first to fourth aspects described above, the separation liquid from which the suspended organic matter has been removed by the suspended organic matter separation device 10 is supplied to the nitritation device 30 via the first transfer path R1. Alternatively, the configuration for supplying the anaerobic ammonia oxidation apparatus 40 via the second transfer path R2 has been described, but the diluent supplied via the transfer paths R1, R2 is not limited to the separation liquid, and the separation liquid A treatment solution in which the organic matter concentration is reduced by biological treatment may be used as a diluent.

FIG. 5 shows the processing system of the fifth aspect. In addition to the treatment system of the second aspect described above, the treatment system includes a biological treatment device 60 that biologically treats the separated liquid of the suspending organic matter separation device 10, and nitrites the biologically treated treatment solution. It is configured to supply to the device 30. It should be noted that the same configuration can be adopted in the processing system of any of the first, third, and fourth modes.

If the BOD component contained in the separation liquid of the suspending organic matter separation device 10 is large, heterotrophic bacteria predominate in the nitritation device 30 and the autotrophic denitrification device 40, resulting in nitritation and anaerobic conditions. There is a risk that the efficiency of the active ammonia oxidation treatment will decrease. This problem can be solved by appropriately removing BOD contained in the separation liquid by the biological treatment apparatus 60. In addition, the biological treatment apparatus 60 can illustrate an aeration tank.

FIG. 6 shows the processing system of the sixth aspect. In the treatment system, liquid organic waste is supplied to the sludge anaerobic digester 20 of the treatment system according to the first aspect described above from a route different from the suspended organic matter supplied from the suspended organic matter separation device 10. It is configured to flow in. The liquid organic waste is preferably food waste, sludge generated by wastewater treatment, livestock manure, and the like. The processing system of the second to fifth aspects can have the same configuration.

According to the processing system and the processing method for suspending organic substance-containing wastewater according to the present invention as shown in the first to fifth aspects described above, the liquid organic waste is introduced into the sludge anaerobic digester from outside the system, and ammonia Even if the amount generated is increased, the nitrous acid concentration (free nitrous acid concentration) in the nitrifying device can be adjusted by the separated liquid from which the suspending organic matter has been removed by the suspending organic matter separating device. Efficient nitrogen removal becomes possible by the ammonia oxidation treatment.

Hereinafter, the results of numerical simulation performed on the processing system according to the present invention will be described.

FIG. 7 shows the result of a numerical simulation performed on the processing system of the second mode described in FIG. 200 m ³ / d treated water flows into the treatment system. The suspending organic matter separation device 10 separates 10 m ³ / d suspending organic matter contained in the water to be treated. The concentration of ammonia nitrogen and nitrite nitrogen in the 190 m ³ / d separation liquid of the suspending organic matter separation apparatus 10 is 0 ppm for convenience.

The suspended organic matter separated by the suspended organic matter separation device 10 is anaerobically digested by the sludge anaerobic digester 20. The digestive fluid contains 5000 ppm of ammonia nitrogen.

The nitritation apparatus 30 is kept aerobic at a temperature of 30 ° C. and pH 7.4, and ammonia contained in the anaerobic digestion liquid of the sludge anaerobic digestion apparatus 20 has a molar ratio of ammonia to nitrous acid of about 1: 1. Nitrite to 3. Therefore, when nitrifying 5000 ppm of ammonia nitrogen as it is, it becomes 2160 ppm of ammonia nitrogen and 2840 ppm of nitrite nitrogen. At this time, the free ammonia concentration is 53.8 ppm and the free nitrous acid concentration is 0.75 ppm.

The concentration of free ammonia is determined by the formula of Anthonisen et al., Which is obtained by measuring the ammonium ion concentration of water to be treated by a diaphragm type ion electrode method or the like and calculating from the relationship between temperature and pH as shown in the following formula 2. The method can be adopted.

This free nitrous acid concentration of 0.75 ppm exceeds the free nitrous acid concentration of 0.2 ppm, which is said to inhibit all nitrifying bacteria, as described above, and hinders the nitritation of ammonia. It becomes concentration.

Therefore, the 45 m ³ / d of the separated liquid separated 190 m ³ / d in suspension organic material separating device 10 via the first transfer path R1, and supplies the nitrous acid apparatus 30. That is, the digestive liquid 10 m ³ / d of the sludge anaerobic digester 20 is diluted 5.5 times with a 45 m ³ / d separation liquid. Then, the digestive liquid of the sludge anaerobic digester 20 having 5000 ppm of ammonia nitrogen is diluted to 900 ppm.

900 ppm of ammonia nitrogen contained in the digested liquid after dilution is nitritized by the nitritation apparatus 30 to become 390 ppm of ammonia nitrogen and 510 ppm of nitrite nitrogen. At this time, the free ammonia concentration is 9.7 ppm, and the free nitrous acid concentration is 0.13 ppm. Thus, by supplying the separation liquid to the nitritation device 30 via the first transfer path R1, the concentration of free nitrous acid can be reduced to a level of 0.2 ppm or less that does not interfere with nitritation. it can.

In addition, if 10 m < ³ > / d of the digestion liquid of the sludge anaerobic digester 20 is diluted 4 times with the separation liquid of 30 m < ³ > / d, the ammonia nitrogen contained in the digested liquid after dilution will be 1250 ppm. When the digested liquid after this dilution is nitritized by the nitritation apparatus 30, it becomes 543 ppm of ammonia nitrogen and 707 ppm of nitrite nitrogen. At this time, the free nitrous acid concentration is 0.19 ppm. That is, it is possible to achieve a free nitrous acid concentration of less than 0.2 ppm by diluting the digestive fluid four times.

However, since the free ammonia concentration is 13.5 ppm, in order to achieve a free ammonia concentration of 0.1 to 10 ppm, which is said to be selectively inhibited by nitric acid bacteria, the digestive fluid of the sludge anaerobic digester 20 is 10 m. ³ / d was diluted 5.5 times with 45 m ³ / d separation. Thus, the digestive juice is diluted so that the concentration of free nitrous acid is less than 0.2 ppm, but it is more preferable to dilute so that the concentration of free ammonia is in the range of 0.1 to 10 ppm.

The autotrophic denitrification apparatus 40 is kept anaerobic at a temperature of 30 ° C. and pH 7.4, and denitrifies the treatment liquid of the nitritation apparatus 30 by anaerobic ammonia oxidation treatment. As described above, the concentration of free nitrous acid in the treatment liquid of the nitritation treatment apparatus 30 is 0.13 ppm. This free nitrous acid concentration of 0.13 ppm exceeds the free nitrous acid concentration, which is a condition for efficient anaerobic ammonia oxidation treatment, by 0.08 ppm. Therefore, the efficiency of the anaerobic ammonia oxidation treatment is lowered as it is.

Therefore, the remaining 135m ³ / d of which 85 m ³ / d of separating liquid separated in suspension organic material separating device 10 via the second transfer path R2, and supplies the autotrophic denitrification device 40. That is, the 55 m ³ / d digested liquid of the nitritation apparatus 30 is diluted about 2.55 times with the 85 m ³ / d separated liquid. Then, the nitrite nitrogen is diluted to 200 ppm in the treatment liquid of the nitrite treatment apparatus 30 having 510 ppm of nitrite nitrogen. At this time, the concentration of free nitrous acid is 0.053 ppm, which is less than 0.08 ppm, which is a condition for efficient anaerobic ammonia oxidation treatment. In addition, nitrous acid nitrogen becomes 300 ppm by 1.7 times dilution, At this time, free nitrous acid concentration will be 0.079 ppm and will be less than 0.08 ppm, but it will be less than 0.06 ppm which can be processed more efficiently. Diluted.

FIG. 8 shows the result of a numerical simulation performed on the processing system of the third aspect described in FIG. The processing system is the processing system of the third aspect described in FIG. 200 m ³ / d treated water flows into the treatment system. The suspending organic matter separation device 10 separates the suspending organic matter 20 m ³ / d contained in the water to be treated. The concentration of ammonia nitrogen and nitrite nitrogen in the 180 m ³ / d separation liquid of the suspending organic matter separation apparatus 10 is 0 ppm for convenience.

Accordingly, the 90m ³ / d of the separated liquid separated 180 m ³ / d in suspension organic material separating device 10 via the first transfer path R1, and supplies the nitrous acid apparatus 30. That is, the digestive liquid 20m ³ / d of the sludge anaerobic digester 20 is diluted 5.5 times with a 90 m ³ / d separation liquid. Then, the ammonia nitrogen in the digestive liquid of the sludge anaerobic digester 20 is diluted from 5000 ppm to 900 ppm.

900 ppm of ammonia nitrogen contained in the digested liquid after dilution is nitritized by the nitritation apparatus 30 to become 390 ppm of ammonia nitrogen and 510 ppm of nitrite nitrogen. At this time, the free ammonia concentration is 9.7 ppm, and the free nitrous acid concentration is 0.13 ppm. In this way, by supplying the separation liquid to the nitritation device 30 via the first transfer path R1, the free nitrous acid concentration can be reduced to less than 0.2 ppm that does not interfere with nitritation.

The autotrophic denitrification apparatus 40 is kept anaerobic at a temperature of 30 ° C. and pH 7.4, and denitrifies the treatment liquid of the nitritation apparatus 30 by anaerobic ammonia oxidation treatment. As described above, the concentration of free nitrous acid in the treatment liquid of the nitritation treatment apparatus 30 is 0.13 ppm. This free nitrous acid concentration of 0.13 ppm exceeds the free nitrous acid concentration, which is a condition for efficient anaerobic ammonia oxidation treatment, by more than 0.06 ppm, so that the efficiency of the anaerobic ammonia oxidation treatment is lowered as it is.

When the treatment liquid of the nitritation treatment apparatus 30 is diluted until nitrite nitrogen is reduced from 510 ppm to 200 ppm, the free nitrous acid concentration at this time becomes 0.053 ppm, which is a condition for efficient anaerobic ammonia oxidation treatment. Less than 0.06 ppm can be achieved. For this purpose, it is necessary to dilute the treatment liquid 110 m ³ / d of the nitritation apparatus 30 about 2.55 times. Therefore, a separation liquid of 170 m ³ / d is necessary for dilution of the treatment liquid. However, the separation liquid separated by the suspending organic matter separation device 10 is only 90 m ³ / d.

Therefore, the remaining 90 m ³ / d of the separation liquid separated by the suspending organic matter separation device 10 is supplied to the autotrophic denitrification device 40 via the second transfer path R2, and the autotrophic denitrification is also performed. Of the denitrification liquid in the apparatus 40, 80 m ³ / d is returned to the autotrophic denitrification apparatus 40 via the third transfer path R3.

As a result, the 110 m ³ / d treatment liquid of the nitritation apparatus 30 is supplied via the 90 m ³ / d separation liquid supplied via the first transfer path R 1 and the third transfer path R 3. Furthermore, it can be diluted about 2.55 times with a denitrification solution of 80 m ³ / d. Then, the nitrite nitrogen in the treatment liquid of the nitritation treatment apparatus 30 is diluted from 510 ppm to 200 ppm. At this time, the concentration of free nitrous acid is 0.053 ppm, and can be made less than 0.06 ppm, which is a condition for efficient anaerobic ammonia oxidation treatment.

Here, the 110 m ³ / d digested liquid of the nitritation apparatus 30 is passed through the 90 m ³ / d separation liquid supplied via the first transfer path R 1 and the third transfer path R 3. The case of diluting about 2.55 times with the supplied 90 m ³ / d denitrification liquid has been described, but the distribution of the separation liquid and denitrification liquid used for dilution of the treatment liquid of the nitritation apparatus 30 is as follows. For example, only 110 m ³ / d denitrification liquid supplied through the third transfer path R 3 without using a separation liquid is used as the 110 m ³ / d treatment liquid of the nitritation apparatus 30. You may comprise so that it may be diluted with. Further, in the treatment system including the heterotrophic denitrification device 50 in the subsequent stage of the autotrophic denitrification device 40 as in the treatment system of the fourth aspect, the denitrification liquid of the heterotrophic denitrification device 50 is sublimated. You may use for the dilution of the process liquid of the nitrification apparatus 30. FIG.

Each of the above-described embodiments is an example of the present invention, and the present invention is not limited by the description. The specific configuration of each part can be appropriately designed within the range where the effects of the present invention are exhibited. Needless to say.

10: Suspended organic matter separation device 20: Sludge anaerobic digester 30: Nitrite device 40: Autotrophic denitrification device 50: Heterotrophic denitrification device 60: Biological treatment device R1: First transfer route R2: Second transfer route R3: Third transfer route R4: Fourth transfer route R5: Fifth transfer route

Claims

Suspended organic matter separation device for separating suspended organic matter from water to be treated containing suspended organic matter, and sludge anaerobic digestion for anaerobic digestion of suspended organic matter separated by the suspended organic matter separation device Apparatus, nitritation apparatus that oxidizes ammonia contained in digestion liquid of sludge anaerobic digestion apparatus to nitrous acid under aerobic conditions, and ammonia contained in treatment liquid of nitritation apparatus under anaerobic conditions An autotrophic denitrification device that oxidizes to nitrogen gas by autotrophic denitrifying microorganisms, and a wastewater-containing wastewater treatment system comprising:
It is provided with the 1st transfer path which supplies the separation liquid from which suspended organic matter was removed with the suspension organic substance separation device, or the processing liquid which carried out the biological treatment of the separation liquid to the nitritation device. Suspended organic matter-containing wastewater treatment system.
2. The suspension according to claim 1, further comprising a second transfer path for supplying a separation liquid of the suspending organic matter separation apparatus or a treatment liquid obtained by biological treatment of the separation liquid to the autotrophic denitrification apparatus. Wastewater treatment system containing turbid organic substances.
The wastewater containing suspended organic matter according to claim 1 or 2, further comprising a third transfer path for returning the denitrification liquid treated by the autotrophic denitrification apparatus to the autotrophic denitrification apparatus. Processing system.
A heterotrophic denitrification device for reducing nitric acid contained in the denitrification solution of the autotrophic denitrification treatment device to nitrogen gas by heterotrophic denitrification microorganisms under anaerobic conditions; The suspension system for suspended organic matter-containing wastewater according to claim 1 or 2, further comprising a fourth transfer path for returning the treated denitrification liquid to the autotrophic denitrification apparatus.
Suspended organic matter separation treatment for separating suspended organic matter from water to be treated containing suspended organic matter, and sludge anaerobic digestion for anaerobically digesting suspended organic matter separated by the suspended organic matter separation treatment Nitrification treatment that oxidizes ammonia contained in the digestion liquid by the sludge anaerobic digestion treatment to nitrous acid under aerobic conditions, and ammonia contained in the treatment liquid by the nitritation treatment under anaerobic conditions A method of treating wastewater containing suspended organic matter, comprising: an autotrophic denitrification treatment that oxidizes to nitrogen gas by an autotrophic denitrifying microorganism,
The separation liquid from which the suspended organic substances have been removed by the suspension organic substance separation treatment or the treatment liquid in which the separation liquid has been biologically treated is transferred to the nitritation treatment and the autotrophic denitrification treatment, A method for treating wastewater containing suspended organic matter, characterized by adjusting the concentration of free nitrous acid in the treatment step.
Suspended organic matter separation treatment for separating suspended organic matter from water to be treated containing suspended organic matter, and sludge anaerobic digestion for anaerobically digesting suspended organic matter separated by the suspended organic matter separation treatment Nitrification treatment that oxidizes ammonia contained in the digestion liquid by the sludge anaerobic digestion treatment to nitrous acid under aerobic conditions, and ammonia contained in the treatment liquid by the nitritation treatment under anaerobic conditions A method of treating wastewater containing suspended organic matter, comprising: an autotrophic denitrification treatment that oxidizes to nitrogen gas by an autotrophic denitrifying microorganism,
The separation liquid from which suspended organic substances have been removed by the suspension organic substance separation treatment or the treatment liquid obtained by biologically treating the separation liquid is transferred to the nitritation treatment, and the treatment liquid or the separation liquid and the treatment liquid are transferred to the nitritation treatment. Both of these are transferred to the autotrophic denitrification treatment, and the concentration of free nitrous acid in each treatment step is adjusted.
The nitrite treatment step adjusts the free nitrous acid concentration to less than 0.2 ppm, and the autotrophic denitrification treatment step adjusts the free nitrous acid concentration to less than 0.08 ppm. 7. A method for treating wastewater containing suspended organic substances according to 5 or 6.