JP2014200747A - Water treatment apparatus and water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus and a water treatment method capable of achieving a high nitrogen removal ratio while keeping treatment costs low.SOLUTION: The water treatment apparatus provided by an embodiment includes: an anaerobic treatment tank for decomposing some of an organic matter in treatment target water including the organic matter and ammoniac nitrogen; an aerobic treatment tank for decomposing the remainder of the organic matter within the anaerobically treated water including the remainder of the organic matter and treated within the anaerobic treatment tank and for converting the ammoniac nitrogen into nitrate nitrogen; a sulfur denitrifying tank for causing contact of hydrogen sulfide generated from the anaerobic treatment tank, the aerobically treated water generated as a result of the treatment within the aerobic treatment tank, and sulfur denitrifying bacteria to thereby partially denitrify the nitrate nitrogen by using the hydrogen sulfide as a reductant; and a heterotrophic denitrifying tank for causing contact of the sulfur-denitrified water generated as a result of the treatment within the sulfur denitrifying tank, the anaerobically treated water generated as a result of the treatment within the anaerobic treatment tank, and heterotrophic denitrifying bacteria to thereby denitrify the remainder of the nitrate nitrogen by using the remainder of the organic matter within the anaerobically treated water as a reductant.

Description

  Embodiments of the present invention relate to a water treatment apparatus and a water treatment method capable of removing nitrogen from, for example, sewage or factory waste water.

  Biological treatment is often used in the treatment of wastewater containing organic matter such as sewage and industrial wastewater. Biological treatment methods can be classified into anaerobic treatment methods using anaerobic microorganisms and aerobic treatment methods using aerobic microorganisms. The anaerobic treatment method has the advantage that the supply of oxygen is not required, so the power cost is low, the generation amount of sludge is small, and the biogas mainly composed of flammable gas, methane gas, can be recovered. Compared with aerobic treatment, the removal performance of organic substances is poor, and as it is, it is difficult to discharge it into a river or the like. In addition, when the water to be treated contains sulfur components such as sulfuric acid, hydrogen sulfide is generated by the action of sulfate-reducing bacteria, one of the anaerobic microorganisms, and the hydrogen sulfide is mixed into biogas. In order to effectively use the gas, it is necessary to perform some kind of desulfurization treatment.

  On the other hand, the aerobic treatment method has the merit that it can obtain the treated water quality that can be discharged into the river, but since it is treated with aerobic microorganisms, it is necessary to supply oxygen, and the power for that is necessary. Compared to anaerobic microorganisms, it has a demerit that it produces more sludge.

  For this reason, a water treatment process that performs anaerobic treatment on the upstream side and aerobic treatment on the downstream side is a method that has an excellent balance of treated water quality, power costs, and sludge generation amount, and is intended to remove organic substances. Has been put to practical use.

  In addition, the combination of a simple anaerobic treatment tank and an aerobic treatment tank cannot remove nitrogen, which is required to be removed as a measure for eutrophication. A method using a circulatory nitrification denitrification method has also been adopted.

  In the method using the circulation type nitrification denitrification method, the water to be treated is guided in the order of the denitrification tank and the aerobic tank after the organic matter is removed by the anaerobic treatment tank. Nitrogen components in the water to be treated are oxidized to nitrate or nitrite nitrogen in the aerobic tank, guided to the denitrification tank by the nitrification liquid circulation pump, and reduced to nitrogen gas by the action of the denitrifying bacteria. To be discharged. In the circulatory nitrification denitrification method, the denitrification reaction proceeds using organic substances as a reducing agent by the action of heterotrophic denitrifying bacteria. The reaction formula of heterotrophic denitrification using acetic acid as an organic substance is shown in Formula (1).

5CH ₃ COO ⁻ + 8NO ₃ ⁻ + 8H ⁺
→ 5CO ₂ + 5HCO ₃ ⁻ + 4N ₂ + 4H ₂ O Formula (1)
From formula (1), organic substances are required to reduce nitrate nitrogen, and it is necessary to adjust the BOD / N ratio to be 2.8 or more for complete denitrification. Depending on the quality of the water to be treated and the BOD removal performance of the anaerobic treatment tank, the BOD / N ratio cannot be satisfied. Therefore, by bypassing the anaerobic treatment tank with a part of the treated water, Adjust the BOD / N ratio.

  In the circulatory nitrification denitrification method, the bypass amount of the anaerobic treatment tank increases depending on the quality of the water to be treated, so that the merit of the anaerobic treatment cannot be fully exhibited, causing an increase in operating cost.

  As one of the methods for solving the above problems, nitrogen removal methods using sulfur denitrification using sulfur as a reducing agent for nitrate nitrogen have been proposed (Patent Documents 1 to 5). The reaction formula of sulfur denitrification using sulfide as a reducing agent is shown in Formula (2).

5HS ⁻ + 8NO ₃ ⁻ + 3H ⁺ → 5SO ₄ ²⁻ + 4N ₂ + 4H ₂ O (2)
Sulfur denitrification is a reaction in which sulfide, elemental sulfur, thiosulfuric acid, etc. are oxidized to sulfuric acid and at the same time nitric acid is reduced to nitrogen. In Patent Documents 1 and 3-5, hydrogen sulfide in biogas, patent In Document 2, a sulfur treating agent mainly composed of a sulfur component is used.

JP 2000-189995 A JP 2008-49251 A JP 2010-42327 A JP2011-189286A JP 2012-66186 A

Ikemoto, Yamashita, Kaneko: Environmental Engineering Research Papers, Vol. 44 (2007)

  The inventors conducted a continuous test for the denitrification process in which heterotrophic denitrification and sulfur denitrification coexist, using the apparatus of FIG. 1 under the two conditions of FIG. In condition 1, the aerobic treated water was adjusted with potassium nitrate so that the concentration of nitrate nitrogen in the influent water was 6.25 mg / L. Moreover, the anaerobic treated water was adjusted with sodium sulfide so that the S / N ratio of the influent water was 0.4. In condition 2, in addition to condition 1, anaerobic treated water was prepared with acetic acid so that the BOD / N ratio of the influent water was 2.

That is, in the condition 1, the S / N ratio was set such that nitrate nitrogen in the influent water could be removed up to 40% by sulfur denitrification. In condition 2, the BOD / N ratio that allows removal of about 75% of nitrate nitrogen in the influent water by heterotrophic denitrification was made 100% in total.

  In both cases, continuous operation for about 5 months is performed with a treatment amount of 4 hours for anaerobic treated water and aerobic treated water, the nitrate nitrogen removal rate, the amount of microorganisms in the denitrification tank at the end of operation and the removal The amount of sulfur deposited and deposited as single sulfur in the nitrogen tank was investigated.

As a result, as shown in FIG. 3, although the nitrate nitrogen removal rate roughly corresponding to the S / N ratio was obtained under the condition 1, the total of the S / N ratio and the BOD / N ratio (maximum 115%) was obtained under the condition 2. The nitrate nitrogen removal rate was lower than Since the amount of sulfur accumulated in the denitrification tank at the end of the operation is greater in condition 2 than in condition 1, the supplied sulfide is accumulated in the form of elemental sulfur without being oxidized to sulfuric acid. It was suggested that the utilization rate of the product as a nitrate nitrogen reducing agent was lower than that in Condition 1, and the contribution to the nitrate nitrogen removal rate by sulfur denitrification was low.

  Furthermore, in the denitrification tank of condition 2, there was a concern that elemental sulfur adhered to the surface of the carrier, which would be a cause of blocking the carrier packed bed. Moreover, there was a concern that the elemental sulfur peeled off from the carrier was precipitated and deposited in the denitrification tank as a solid substance, which would cause the denitrification tank to be blocked. In order to prevent clogging, when this solid substance containing simple sulfur as a main component is taken out, it becomes solid waste, and there is a concern that the processing cost increases due to the disposal cost.

  This invention is devised with respect to the said subject, and it aims at suppressing the accumulation | storage of single-piece | unit sulfur in a denitrification processing tank, and preventing the obstruction | occlusion of a sulfur denitrification processing tank, and the increase of waste solid substance. .

  According to Non-Patent Document 1 described above, when the S / N ratio is 1.0 or more in sulfur denitrification, sulfur particles are accumulated in the denitrification tank, and when the S / N ratio is 0.5 or less, the accumulated sulfur. It has been shown that the grains are used for denitrification.

  In condition 1, as shown in non-patent literature, accumulation of sulfur in the denitrification tank was not observed. On the other hand, in condition 2, although the S / N ratio was 0.5 or less, accumulation of sulfur in the denitrification tank was observed. Therefore, heterotrophic denitrification and sulfur denitrification proceeded with preference (or faster), and the remaining 25% (about 1.2) from which 75% nitrate nitrogen was removed by heterotrophic denitrification. 56 mg / L) of nitrate nitrogen was subjected to sulfur denitrification. In that case, the S / N ratio was 1.6, and since it exceeded 1.0, it was assumed that sulfur accumulated in the denitrification tank. It was.

  Accordingly, the nitrogen removal method and apparatus shown in FIG. 4 have been devised.

  The water treatment apparatus of the embodiment was treated in the anaerobic treatment tank that decomposes a part of the organic matter in the water to be treated containing organic matter and ammonia nitrogen, and the anaerobic treatment tank that contains the remainder of the organic matter. The aerobic treatment tank decomposes the remainder of the organic matter and converts the ammoniacal nitrogen into nitrate nitrogen, hydrogen sulfide generated from the anaerobic treatment tank, and the aerobic treatment tank. The aerobic treated water and a sulfur denitrifying bacterium are brought into contact with each other, and the sulfur denitrification treatment tank for denitrifying a part of the nitrate nitrogen using the hydrogen sulfide as a reducing agent, and the treatment in the sulfur denitrification treatment tank The sulfur denitrification treated water, the anaerobic treated water treated in the anaerobic treatment tank and the heterotrophic denitrifying bacteria are brought into contact, and the remaining organic matter in the anaerobic treated water is used as a reducing agent, and the nitrate state Heterotrophic denitrification to denitrify the remainder of nitrogen Comprising a vessel, a.

Schematic diagram of a nitrogen removal test apparatus using sulfur denitrification and heterotrophic denitrification. The table | surface which showed the test conditions of the nitrogen removal test apparatus shown in FIG. The table | surface which showed the test result of the nitrogen removal test apparatus shown in FIG. The schematic diagram which showed typically the whole structure of the water treatment apparatus of embodiment. The table | surface which showed an example of the operating conditions of the sulfur denitrification reactor and heterotrophic denitrification reactor of the water treatment apparatus shown in FIG.

  Hereinafter, the water treatment apparatus according to the embodiment will be described with reference to FIGS. 4 and 5.

  The water treatment apparatus 11 includes an anaerobic reactor 12 (anaerobic treatment tank), an aerobic reactor 13 (aerobic treatment tank), a sulfur denitrification reactor 14 (sulfur denitrification treatment tank), and a heterotrophic denitrification reactor 15 (heterotrophic nutrition). (Denitrification tank).

  The water treatment device 11 includes a first pipe 21 connecting the anaerobic reactor 12 and the heterotrophic denitrification reactor 15, a second pipe 22 connecting the heterotrophic denitrification reactor 15 and the aerobic reactor 13, and an aerobic reactor. 13 and the sulfur denitrification reactor 14, the third pipe 23 connected to the sulfur denitrification reactor 14 and the heterotrophic denitrification reactor 15, and the anaerobic reactor 12 connected to the anaerobic reactor 12. A sewage pipe 25 (fifth pipe) that supplies treated water (sewage), and a discharge pipe 26 (sixth pipe) that is connected to the aerobic reactor 13 and discharges treated (purified) treated water from the aerobic reactor 13. And.

  The water treatment apparatus 11 is provided in the middle of the first pump 31 that sends the anaerobic treated water that is provided in the middle of the first pipe 21 and is processed in the anaerobic reactor 12 to the heterotrophic denitrification reactor 15, and the third pipe 23. The second pump 32 that sends the aerobic treated water treated in the aerobic reactor 13 to the sulfur denitrification reactor 14, and the sulfur denitrification treated water treated in the sulfur denitrification reactor 14 provided in the middle of the fourth pipe 24. A third pump 33 that sends to the heterotrophic denitrification reactor 15 and a sewage pump 34 (fourth pump) that is provided in the middle of the sewage pipe 25 and sends treated water to the anaerobic reactor 12 are provided. The first pump 31 is an example of a water supply unit.

  Further, as will be described later, the water treatment device 11 collects a biogas containing hydrogen sulfide from the anaerobic reactor and supplies the biogas to the sulfur denitrification reactor 14, and branches from the middle of the aeration tube 35. The first gas pipe 41 for collecting the biogas, the second gas pipe 42 for collecting the biogas desulfurized from the sulfur denitrification reactor 14, and the third gas for collecting the nitrogen gas from the heterotrophic denitrification reactor 15 A gas pipe 43. In the middle of the air diffusion pipe 35, for example, a blower for sending biogas to the sulfur denitrification reactor 14 is interposed.

  In the anaerobic reactor 12 (anaerobic treatment tank), hydrolyzing bacteria, acid-producing bacteria, and methanogenic bacteria decompose organic substances in sewage (treated water) to methane gas, and the organic substances in sewage (treated water) Remove most (anaerobic treatment). Thus, the anaerobic reactor 12 can recover a gas called biogas whose main component is methane gas, which is a combustible gas.

When the water to be treated (sewage) contains a sulfur content, sulfate-reducing bacteria that are a kind of anaerobic bacteria produce hydrogen sulfide in the anaerobic reactor 12. For this reason, in the anaerobic treated water, hydrogen sulfide is dissolved in the form of hydrogen sulfide ions (HS ⁻ ), sulfide ions (S ²⁻ ), and hydrogen sulfide (H ₂ S) (these are pH values in the liquid). However, in the following, this is referred to as hydrogen sulfide). And the hydrogen sulfide produced | generated in this way mixes in above-described biogas.

In the aerobic reactor 13 (aerobic treatment tank), for example, a blower is provided near the bottom. The blower can supply air into the aerobic reactor 13. In the aerobic reactor 13, the aerobic microorganisms decompose the remaining organic matter into carbon dioxide. In the aerobic reactor 13, the nitrifying bacteria oxidize ammonia (ammonia nitrogen) contained in the raw water to nitrogen in a nitrous acid (NO ₂ ⁻ ) state and a nitric acid (NO ₃ ⁻ ) state (aerobic treatment).

  The sulfur denitrification reactor 14 (sulfur denitrification treatment tank) has a first carrier 44 holding sulfur denitrifying bacteria at a high concentration inside (in the liquid). The first carrier 44 has a surface on which microorganisms are easily rooted. The first carrier 44 may be, for example, a string-like one used by being hung, or may be one that has a specific gravity lighter than water and floats in the liquid. Note that the first carrier 44 is desirably filled in the upper layer portion of the liquid of the sulfur denitrification reactor 14 without any gap in order to effectively contact biogas and aerobic treated water. On the other hand, it is desirable that there is enough space to allow the flow of the biogas described later.

  The air diffusion pipe 35 has a nozzle portion 45 at a position below the first carrier 44 (near the bottom of the sulfur denitrification reactor 14), and biogas and sulfide are introduced into the sulfur denitrification reactor 14 via the nozzle portion 45. Hydrogen can be supplied. Therefore, the nozzle portion 45 is provided below the liquid surface of the aerobic treated water stored in the sulfur denitrification reactor 14. Biogas and hydrogen sulfide are blown into the sulfur denitrification reactor from below the first carrier 44 by driving the blower in the air diffusion pipe 35. The ratio (S / N ratio) between the amount of sulfur and the amount of nitrate nitrogen in the liquid (inflow water) in the sulfur denitrification reactor 14 is the flow rate of biogas containing hydrogen sulfide supplied to the sulfur denitrification reactor 14. It is controlled by adjusting.

There are various reports on sulfur denitrification treatment with sulfur denitrifying bacteria (typically Thiobacillus denitrificans). For example, as shown in the following formulas (1) to (3), hydrogen sulfide ion (HS ⁻ ), elemental sulfur (S ₀ ), nitrate and nitrite are used to oxidize sulfur to sulfuric acid and nitrogen to nitrogen gas. There is something to reduce. In addition, thiosulfate ions (S ₂ O ₃ ²⁻ ) can be used as sulfur, and N ₂ O (nitrous oxide) can be used as a nitrogen source.
_{^{5HS - + 8NO 3 - + 3H}} + → 5SO 4 2- + 4N 2 + 4H 2 O ... (1)
S ₀ + 2NO ₂ ⁻ → N ₂ + SO ₄ ²⁻ (2)
5S ₀ + 6NO ₃ ⁻ + 2H ₂ O → 5SO ₄ ²⁻ + 3N ₂ + 4H ⁺ (3)
Here, the reaction with nitrate is exemplified, but there is also a sulfur denitrifying bacterium that performs denitrification using nitrite.

  The heterotrophic denitrification reactor 15 (heterotrophic denitrification treatment tank) has the second carrier 46 inside (in the liquid). The structure of the second carrier 46 is substantially the same as the first carrier 44 of the sulfur denitrification reactor 14. The second carrier 46 maintains a high concentration of heterotrophic denitrifying bacteria (which requires organic substances during denitrification; hereinafter referred to as denitrifying bacteria).

Denitrifying bacteria (typically, microorganisms such as Preudomonas denitrificans) can use various organic substances. As an example, the reaction when acetic acid is used as the organic substance is illustrated in the following formula (4).
5CH ₃ COO ⁻ + 8NO ₃ ⁻ + 8H ⁺ → 5CO ₂ + 5HCO ₃ ⁻ + 4N ₂ + 4H ₂ O (4)
Due to the action of denitrifying bacteria, a denitrification reaction proceeds using organic substances as a reducing agent (heterotrophic denitrification treatment). In the heterotrophic denitrification reactor 15, the BOD (biochemical oxygen demand) / N ratio is adjusted to, for example, 2 for almost complete denitrification. Adjustment of the BOD / N ratio in the heterotrophic denitrification reactor 15 is adjusted by manipulating the amount of anaerobic treated water supplied from the anaerobic reactor 12.

  Then, with reference to FIG. 4, FIG. 5, the water treatment process (water treatment method) using the water treatment apparatus 11 of this embodiment is demonstrated.

  The sulfur denitrification reactor 14 and the heterotrophic denitrification reactor 15 were set under the conditions shown in FIG. For example, in the sulfur denitrification reactor 14, the S / N ratio of the inflow water (aerobic treated water) is adjusted to 0.5 or less. In the present embodiment, the S / N ratio is adjusted to 0.4 as an example, but the S / N ratio may be any value as long as it is, for example, 0.1 or more and 0.5 or less.

  The time for which the treated water stays in the sulfur denitrification reactor 14 and the heterotrophic denitrification reactor 15 is 4 hours, respectively. The conditions shown in FIG. 5 are merely examples, and vary depending on the conditions of the water to be treated (sewage), other treatment conditions, and the like.

  First, sewage (treated water) is supplied from the sewage pipe 25 to the anaerobic reactor 12 by driving the sewage pump 34. In the anaerobic reactor 12, hydrolyzing bacteria, acid-producing bacteria, and methanogens decompose some of the organic matter in the sewage into methane gas, thereby producing biogas. Similarly, sulfate-reducing bacteria produce hydrogen sulfide in an anaerobic reactor.

  The biogas containing hydrogen sulfide generated by these anaerobic treatments is supplied to the sulfur denitrification reactor 14 through the air diffuser 35 and the blower. The anaerobic treated water treated in the anaerobic reactor 12 is sent to the heterotrophic denitrification reactor 15 through the first pipe 21 by driving the first pump 31. In addition, in the anaerobic treated water treated by the anaerobic treatment, ammonia (ammonia nitrogen) contained in the water to be treated (sewage) is dissolved as it is.

The anaerobic treated water sent to the heterotrophic denitrification reactor 15 is temporarily stored in the heterotrophic denitrification reactor 15. However, in the state where nitrous acid (NO ₂ ⁻ ) and nitric acid (NO ₃ ⁻ ) are not supplied into the heterotrophic denitrification reactor 15, no particular reaction is performed. The supernatant of the anaerobic treated water stored in the heterotrophic denitrification reactor 15 is supplied to the aerobic reactor 13 via the second pipe 22.

In the aerobic reactor 13, the organic matter remaining in the anaerobic treated water is decomposed into carbon dioxide by the action of the aerobic microorganism. The aerobic reactor 13 oxidizes ammonia (ammonia nitrogen) contained in the anaerobic treated water to nitrogen in a nitrous acid (NO ₂ ⁻ ) state and a nitric acid (NO ₃ ⁻ ) state by the action of nitrifying bacteria. The aerobic treated water treated in the aerobic reactor 13 is sent to the sulfur denitrification reactor 14 through the third pipe 23 by driving the second pump 32.

A biogas containing hydrogen sulfide is supplied into the sulfur denitrification reactor 14 through the air diffusion pipe 35 and the nozzle portion 45. In the sulfur denitrification reactor 14, sulfur denitrification bacteria perform a sulfur denitrification reaction. Sulfur denitrifying bacteria reduce nitrogen to nitrogen gas using hydrogen sulfide ions (HS ⁻ ), elemental sulfur (S ₀ ), nitrates, and nitrites. At the same time, sulfur denitrifying bacteria oxidize sulfur to sulfuric acid.

  By using hydrogen sulfide by sulfur denitrification treatment, biogas desulfurization treatment (treatment for removing hydrogen sulfide from biogas) is performed. The desulfurized biogas and the nitrogen generated by the sulfur denitrification reaction are recovered through the second gas pipe 42.

  By such sulfur denitrification treatment, a part (about 40%) of nitrate nitrogen contained in the aerobic treated water is removed. The sulfur denitrification treated water treated in the sulfur denitrification reactor 14 is sent to the heterotrophic denitrification reactor 15 via the fourth pipe 24 by driving the third pump 33.

  In addition to the sulfur denitrification treated water, the anaerobic treated water from the anaerobic reactor 12 is sent to the heterotrophic denitrification reactor 15 as described above. This anaerobic treated water contains the remainder of organic matter that was not decomposed by the anaerobic treatment. With this anaerobic treated water, an amount of organic matter necessary for the heterotrophic denitrification treatment is supplied to the heterotrophic denitrification reactor 15.

  In the heterotrophic denitrification reactor 15, the denitrifying bacteria performs a denitrification reaction using the organic substance (the remainder of the organic substance) as a reducing agent. By the denitrification reaction in the heterotrophic denitrification reactor 15, the remainder of nitrate nitrogen in the sulfur denitrification treated water (about 60% of the total nitrate nitrogen contained in the aerobic treated water) can be removed.

  By this heterotrophic denitrification treatment, almost 100% of nitrate nitrogen in the aerobic treated water is removed together with the sulfur denitrification described above. Nitrogen gas generated by the heterotrophic denitrification process is recovered via the third gas pipe 43. Here, the “remainder” of nitrate nitrogen means the total amount of nitrate nitrogen that was not treated by the sulfur denitrification treatment, but the “residue” was not treated by the sulfur denitrification treatment. It may be a part of nitrate nitrogen. In the latter case, the removal rate of nitrate nitrogen in the treated water does not reach 100% even when the sulfur denitrification treatment and the heterotrophic denitrification treatment are combined.

  The supernatant of the heterotrophic denitrification water is sent to the aerobic reactor 13 via the second pipe 22. The first pump 31 (water supply unit) sends the anaerobic treated water to the heterotrophic denitrification reactor 15 at a constant flow rate, and the same flow rate as that of the anaerobic treated water by the driving force of the first pump 31. Heterotrophic denitrification treated water is supplied to the aerobic reactor 13. The heterotrophic denitrification treated water sent into the aerobic reactor 13 is mixed with the aerobic treated water. The heterotrophic denitrification treated water mixed in this way is drained from the aerobic reactor 13 to the drain pipe at the same flow rate as the anaerobic treated water by the driving force of the first pump 31.

  The water treatment apparatus 11 of the embodiment is treated in the anaerobic treatment tank that decomposes a part of the organic matter in the water to be treated containing organic matter and ammonia nitrogen, and the anaerobic treatment tank that contains the remainder of the organic matter. The aerobic treatment tank that decomposes the remainder of the organic matter in the anaerobic treatment water and converts the ammoniacal nitrogen to nitrate nitrogen, hydrogen sulfide generated from the anaerobic treatment tank, and treatment in the aerobic treatment tank A sulfur aerobic treatment water and a sulfur denitrification bacterium, and a sulfur denitrification treatment tank for denitrifying a part of the nitrate nitrogen using the hydrogen sulfide as a reducing agent, and the sulfur denitrification treatment tank The treated sulfur denitrification treated water, the anaerobic treated water treated in the anaerobic treatment tank and the heterotrophic denitrifying bacteria are brought into contact with each other, and the remaining nitric acid in the anaerobic treated water is used as a reducing agent, and the nitric acid Heterotrophic denitrification that denitrifies the rest of the state nitrogen Comprising a treatment tank, a.

  Moreover, the water treatment method of the embodiment was treated by anaerobic treatment for decomposing a part of the organic matter in the water to be treated containing organic matter and ammonia nitrogen, and the anaerobic treatment containing the remainder of the organic matter. In the anaerobic treated water, the aerobic treatment which decomposes the remainder of the organic matter and converts the ammoniacal nitrogen to nitrate nitrogen, hydrogen sulfide generated in the anaerobic treatment, and aerobic treated in the aerobic treatment Sulfur denitrification treatment in which treated water and sulfur denitrifying bacteria are contacted to denitrify a part of the nitrate nitrogen using the hydrogen sulfide as a reducing agent, and sulfur denitrification treated in the sulfur denitrification treatment The treated water, the anaerobic treated water treated in the anaerobic treatment and the heterotrophic denitrifying bacteria are brought into contact with each other, and the remainder of the nitrate nitrogen is denitrified using the remainder of the organic matter in the anaerobic treated water as a reducing agent. A heterotrophic denitrification process, comprising .

  According to these structures, almost 100% of nitrogen can be removed from the treated water by sulfur denitrification treatment and heterotrophic denitrification treatment. This can effectively prevent eutrophication in the river. Moreover, since it can reduce the amount of denitrification which bears by heterotrophic denitrification processing by using together with sulfur denitrification processing, the amount of organic substances required by heterotrophic denitrification processing can be reduced. As a result, it is possible to prevent the organic matter from being deficient in the anaerobic treated water purified by the anaerobic treatment, so that sufficient denitrification does not occur in the heterotrophic denitrification treatment. In addition, hydrogen sulfide generated in anaerobic treatment can be effectively used in heterotrophic denitrification treatment, so the amount of elemental sulfur added to heterotrophic denitrification treatment can be reduced, and the number of additions of elemental sulfur can be reduced. Alternatively, the addition of elemental sulfur can be made unnecessary. Thereby, the water treatment cost can be reduced.

  The water treatment apparatus includes a biogas generated in the anaerobic treatment tank and an aeration pipe 35 for supplying the hydrogen sulfide into the sulfur denitrification treatment tank, and the biogas desulfurized in the sulfur denitrification treatment tank. A gas pipe for collecting the gas.

  According to this configuration, hydrogen sulfide in the biogas can be removed by sulfur denitrification treatment. This makes it possible to obtain a biogas that does not require a separate treatment process (desulfurization treatment) and to effectively use hydrogen sulfide in the sulfur denitrification treatment.

  In this embodiment, the nozzle part 45 of the diffuser pipe 35 is provided below the liquid level of the aerobic treated water stored in the sulfur denitrification treatment tank. According to this configuration, hydrogen sulfide can be efficiently dissolved in the aerobic treated water in the sulfur denitrification treatment tank.

  The water treatment device 11 extends from the aerobic treatment tank and discharges the aerobic treatment water treated in the aerobic treatment tank, and from the anaerobic treatment tank to the heterotrophic denitrification treatment tank. Sending the anaerobic treated water at a predetermined flow rate and treating the heterotrophic treated water treated in the heterotrophic denitrification treatment tank from the heterotrophic denitrification treatment tank at the same flow rate as the predetermined flow rate A water supply section that is sent to the tank and discharged from the aerobic treatment tank through the discharge pipe 26.

  According to this structure, the heterotrophic treated water of the same amount as the anaerobic treated water sent from the anaerobic treated tank can be discharged to the outside. Thereby, the water treatment apparatus 11 which can be continuously operated stably at low cost can be realized.

  In the sulfur denitrification treatment tank, a ratio (S / N ratio) of a total sulfur amount including sulfur in the hydrogen sulfide and the nitrate nitrogen amount is 0.5 or less. In the present embodiment, a two-stage denitrification process is performed, which is a first-stage sulfur denitrification process and a second-stage heterotrophic denitrification process. And in the required treatment process, anaerobic treated water is purified to some extent (organic matter is removed), so that the amount of organic matter that serves as a reducing agent is not sufficiently supplied to the subsequent heterotrophic denitrification ( There is a precondition). When hydrogen sulfide (which becomes a reducing agent in sulfur denitrification) is supplied so that the S / N ratio is greater than 0.5, single sulfur is accumulated in the sulfur denitrification treatment tank, and sulfur accumulation is caused by the accumulation. There will be a situation in which blockage occurs in the nitriding tank.

  According to the above configuration, the sulfur denitrification treatment is performed prior to the heterotrophic denitrification treatment so that the S / N ratio is 0.5 or less, thereby realizing almost complete denitrification. Can do.

  Furthermore, according to the said structure, a desired water treatment process is realizable, without the denitrification reaction by sulfur denitrifying bacteria being inhibited by addition of excess sulfur. Moreover, according to the said structure, addition of excess sulfur can be prevented, and single sulfur can precipitate and deposit in a sulfur denitrification processing tank, and it can prevent that the inside of a sulfur denitrification processing tank is obstruct | occluded. Accumulation of elemental sulfur in the sulfur denitrification treatment tank is prevented, so the cost required to remove elemental sulfur from the sulfur denitrification treatment tank for cleaning or to discard the extracted elemental sulfur is eliminated. Can be reduced.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... Water treatment apparatus, 12 ... Anaerobic reactor, 13 ... Aerobic reactor, 14 ... Sulfur denitrification reactor, 15 ... Heterotrophic denitrification reactor, 31 ... First pump, 35 ... Aeration pipe, 42 ... Second gas pipe, 45 ... Nozzle

Claims (8)

An anaerobic treatment tank for decomposing part of the organic matter in the water to be treated containing organic matter and ammoniacal nitrogen;
An aerobic treatment tank that decomposes the remainder of the organic substance and converts the ammonia nitrogen to nitrate nitrogen in the anaerobic treatment water treated in the anaerobic treatment tank containing the remainder of the organic substance;
Hydrogen sulfide generated from the anaerobic treatment tank, aerobic treated water treated in the aerobic treatment tank, and sulfur-denitrifying bacteria are brought into contact with each other, and one of the nitrate nitrogens using the hydrogen sulfide as a reducing agent. A sulfur denitrification treatment tank for denitrifying the part,
Contacting the sulfur denitrification treated water treated in the sulfur denitrification treatment tank, the anaerobic treated water treated in the anaerobic treatment tank and the heterotrophic denitrifying bacteria, the remainder of the organic matter in the anaerobic treated water A heterotrophic denitrification treatment tank that denitrifies the remainder of the nitrate nitrogen using a reducing agent,
A water treatment apparatus comprising: An air diffuser for supplying the biogas generated in the anaerobic treatment tank and the hydrogen sulfide into the sulfur denitrification treatment tank;
A gas pipe for collecting the biogas desulfurized in the sulfur denitrification tank;
A water treatment device according to claim 1.   The water treatment apparatus according to claim 2, wherein a nozzle portion of the air diffusion pipe is provided below a liquid surface of the aerobic treated water stored in the sulfur denitrification treatment tank. A discharge pipe extending from the aerobic treatment tank and discharged from the aerobic treatment water treated in the aerobic treatment tank;
While sending the anaerobic treated water at a predetermined flow rate from the anaerobic treatment tank to the heterotrophic denitrification treatment tank, the heterotrophic denitrification treated water treated in the heterotrophic denitrification treatment tank is the predetermined flow rate. A water supply section that is sent from the heterotrophic denitrification treatment tank to the aerobic treatment tank at the same flow rate, and is discharged from the aerobic treatment tank through the discharge pipe,
A water treatment device according to claim 3.   The water treatment apparatus according to claim 4, wherein a ratio (S / N ratio) of a total sulfur amount including sulfur in the hydrogen sulfide and the nitrate nitrogen amount is 0.5 or less in the sulfur denitrification treatment tank. Anaerobic treatment for decomposing part of the organic matter in the water to be treated containing organic matter and ammoniacal nitrogen;
Aerobic treatment of decomposing the remaining organic matter and converting the ammoniacal nitrogen to nitrate nitrogen in the anaerobic treated water treated by the anaerobic treatment containing the remaining organic matter;
Hydrogen sulfide generated by the anaerobic treatment, aerobic treated water treated by the aerobic treatment, and sulfur denitrifying bacteria are contacted, and a part of the nitrate nitrogen is reduced using the hydrogen sulfide as a reducing agent. Sulfur denitrification treatment to denitrify,
The sulfur denitrification treated water treated in the sulfur denitrification treatment, the anaerobic treated water treated in the anaerobic treatment and the heterotrophic denitrifying bacteria are brought into contact with each other, and the remainder of the organic matter in the anaerobic treated water is reduced. Heterotrophic denitrification treatment for denitrifying the remainder of the nitrate nitrogen as an agent,
A water treatment method comprising:   The water according to claim 6, further comprising a process of supplying the biogas generated in the anaerobic process and the hydrogen sulfide to the sulfur denitrification process and recovering the biogas desulfurized by the sulfur denitrification process. Processing method.   The water treatment method according to claim 7, wherein, in the sulfur denitrification treatment, a ratio (S / N ratio) of a total sulfur amount including sulfur in the hydrogen sulfide and the nitrate nitrogen amount is 0.5 or less.

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