Sewage treatment method using microorganisms

Abstract

The present invention relates to a sewage treatment method using microorganisms and, specifically, to a sewage treatment method using microorganisms, in which a first biological reaction step (S2), a second biological reaction step (S4), a precipitation step (S5), and a discharge step (S6) are sequentially performed, wherein the first biological reaction step (S2) is operated under anaerobic conditions, the second biological reaction step (S4) is operated under anoxic conditions, and the first biological reaction step (S2) and the second biological reaction step (S4) are performed in a sequencing batch reactor (SBR).

Description

Sewage treatment method using microorganisms

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0130678 dated September 26, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0002] The present invention relates to a wastewater treatment method using microorganisms, and more specifically, to a wastewater treatment method using microorganisms capable of purifying wastewater and membrane concentrate together using a continuous batch reactor (SBR).

[0003]

[0004] Generally, wastewater treatment methods can be broadly classified into the continuous flow method, which utilizes a sedimentation tank, and the continuous batch reactor (SBR) method, which allocates sedimentation time within the reactor without installing a separate sedimentation tank.

[0005] The continuous flow method involves installing separate reaction tanks—namely, anaerobic, anoxic, aerobic, and sedimentation tanks—to create the conditions required for anaerobic, anoxic, aerobic, and sedimentation wastewater treatment. It is primarily used in medium and large-scale treatment plants with a capacity of 10,000 m³ / day or more, and many examples of its installation can be found.

[0006] However, since the continuous flow method is designed to match the flow rate and water quality of the influent to be treated, it has the disadvantage of having reduced ability to cope when the flow rate increases or water quality fluctuates.

[0007] In contrast, the continuous batch reactor (SBR) consists of a single reactor that does not require a sedimentation tank, and is a method in which treatment is carried out by applying anaerobic, anoxic, aerobic, and sedimentation conditions within the single reactor, divided into an influent stage, a reaction stage, a sedimentation stage, and an effluent stage.

[0008] Continuous Batch Reactors (SBRs) are mainly used in small and medium-sized treatment plants with a capacity of less than 10,000 m³ / day, and are known to be capable of temporarily treating up to 2.5 times the normal flow rate due to their strong ability to cope with increased flow rates or fluctuations in water quality.

[0009] The Water Environment Federation (WEF) evaluated that continuous batch reactors (SBRs) are highly suitable for small-scale environments with significant fluctuations in flow rate and water quality, as they can be easily applied in small cities with limited land area, have excellent applicability depending on the characteristics of the wastewater, and are capable of removing nitrogen and phosphorus (Design of Municipal Wastewater Treatment Plant, WEF, 1998).

[0010] Recently, A / O, A 2 Advanced treatment process development is evolving from a spatial arrangement method, such as the / O and BardenpHo processes, in which 2 to 4 reactors are separated into anaerobic, anoxic, and aerobic states and sedimentation tanks are arranged, to a temporal reactor operation method in which the direction of influent injection and the operation method of the reactors are changed over time.

[0011] In particular, intermittent aeration treatment techniques that are effective for nitrogen treatment have been developed and are being used. The main focus of these methods is to effectively utilize organic matter in the anoxic or anaerobic stage, which is the stage of denitrification and phosphorus release.

[0012] However, in wastewater treatment using microorganisms, including continuous batch reactors (SBRs), aeration is required to supply oxygen, resulting in high maintenance costs such as electricity expenses.

[0013] Meanwhile, water consumption is steadily increasing due to the improvement of living standards, increased economic activity, and industrial development, whereas available water resources remain limited. In particular, as clean water resources that were previously available for use are decreasing due to water pollution—a major environmental issue caused by climate change—the water shortage is becoming increasingly severe.

[0014] Consequently, interest in the reuse of treated wastewater is increasing, and the number of treatment plants reusing treated wastewater by applying membrane technologies such as microfiltration, ultrafiltration, nanofiltration, or reverse osmosis is growing.

[0015] However, the concentrated water generated during the reuse process contains high concentrations of nitrogen, including nitrates, so the treatment of this concentrated water is emerging as a new problem.

[0016]

[0017] (Prior Art Literature)

[0018] (Patent Document 0001) Korean Registered Patent No. 2665116 (May 13, 2024)

[0019] (Patent Document 0002) Korean Registered Patent No. 2214449 (February 9, 2021)

[0020] (Patent Document 0003) Korean Registered Patent No. 1822054 (January 25, 2018)

[0021] (Patent Document 0004) Korean Registered Patent No. 2101020 (April 14, 2020)

[0022]

[0023] In order to solve the above-mentioned problems, the present invention aims to provide a wastewater treatment method using microorganisms that can reduce maintenance costs during wastewater treatment.

[0024] Furthermore, the present invention aims to provide a sewage treatment method using microorganisms capable of treating membrane concentrate generated during the reuse of sewage water together with the sewage.

[0025]

[0026] A wastewater treatment method using microorganisms according to the present invention for achieving the above objective is characterized in that a first biological reaction step (S2), a second biological reaction step (S4), a sedimentation step (S5), and a discharge step (S6) are carried out sequentially, wherein the first biological reaction step (S2) is operated under anaerobic conditions and the second biological reaction step (S4) is operated under anoxic conditions, and the first biological reaction step (S2) and the second biological reaction step (S4) are carried out in a Sequencing Batch Reactor (SBR).

[0027] In addition, the wastewater treatment method using microorganisms according to the present invention is characterized by further including a step of supplying raw water at least once prior to the second biological reaction step (S4).

[0028] In addition, the wastewater treatment method using microorganisms according to the present invention is characterized by including a first raw water supply step (S1) for supplying a first raw water prior to the first biological reaction step (S2), and further including a second raw water supply step (S3) for supplying a second raw water between the first biological reaction step (S2) and the second biological reaction step (S4).

[0029] In addition, in the wastewater treatment method using microorganisms according to the present invention, the Sequencing Batch Reactor (SBR) is characterized by having partial denitrification microorganisms, anaerobic ammonium oxidation microorganisms, and microorganisms that simultaneously remove nitrogen and phosphorus coexist.

[0030] In addition, in the wastewater treatment method using microorganisms according to the present invention, the partial denitrification microorganism is one or more selected from the group consisting of Pseudomonas, Bacillus, Thauera, Hypomicrobium, Agrobacterium, Acinetobacter, Propionobacterium, Rhizobium, Thiobacillus, Alcaligenes, Pseudomonas fluorescens, Pseudomonas Aeruginosa, Pseudomonas denitrificans, Acidovorax, Dokdonella, Flavobacterium, Rubrivivax, Terrimonas ferruginea, Terrimonas lutea, Rhodobacter, Lysobacter, Staphylococcus, Paracoccus denitrificans, Denitratisoma, etc., the anaerobic ammonium oxidizing microorganism is Planctomycetes, Candidatus B., or Anammoxidans, and the nitrogen and phosphorus simultaneous removal microorganism is Ca. Accumulibacter, Ca. It is characterized by having at least one species selected from the group consisting of Dechloromonas, Zoogloea, Pseudomonas, Thauera, Paracoccus, and Flavobacterium.

[0031] In addition, in the wastewater treatment method using microorganisms according to the present invention, the first raw water is wastewater, and the second raw water is membrane concentrate.

[0032] In addition, in the wastewater treatment method using microorganisms according to the present invention, the second raw water is characterized as being concentrated water from a nanofiltration membrane or a reverse osmosis membrane.

[0033] In addition, in the wastewater treatment method using microorganisms according to the present invention, the second raw water is characterized as being concentrated water generated during the process of filtering wastewater treatment effluent through a nanofiltration membrane or a reverse osmosis membrane.

[0034] In addition, in the wastewater treatment method using microorganisms according to the present invention, the first raw water is supplied prior to the first biological reaction step (S2) and between the first biological reaction step (S2) and the second biological reaction step (S4).

[0035] In addition, in the wastewater treatment method using microorganisms according to the present invention, the first biological reaction step (S2) is characterized by containing 20 mg / L or more of organic matter.

[0036] In addition, in the wastewater treatment method using microorganisms according to the present invention, the second biological reaction step (S4) is characterized by maintaining the organic matter / nitrate ratio in the range of 1.7 to 2.0.

[0037]

[0038] According to the wastewater treatment method using microorganisms according to the present invention, since the process proceeds through an anaerobic condition stage and an anoxic condition stage, aeration for oxygen supply can be omitted, thereby significantly reducing treatment and maintenance costs.

[0039] In addition, according to the wastewater treatment method using microorganisms according to the present invention, the membrane concentrate can be used as a nitrate source, thereby reducing the cost of treating the membrane concentrate.

[0040]

[0041] FIG. 1 is a schematic diagram illustrating the mechanism of removing organic matter and nutrients by microorganisms according to the present invention.

[0042] Figure 2 is a schematic diagram of the device used in the present invention.

[0043] Figure 3 shows the results of ammonia concentration, nitrate concentration, nitrite concentration, and phosphorus concentration for raw water and effluent for each section.

[0044] Figure 4 shows the results of ammonia removal rate, nitrate removal rate, nitrite removal rate, and phosphorus removal rate for raw water and effluent for each section.

[0045] Figure 5 shows the COD concentration and removal rate results for raw water and effluent for each section.

[0046]

[0047] Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0048]

[0049] The wastewater treatment method using microorganisms according to the present invention comprises a series of steps consisting of a first raw water supply step (S1), a first biological reaction step (S2), a second raw water supply step (S3), a second biological reaction step (S4), a sedimentation step (S5), and a discharge step (S6), which are performed repeatedly.

[0050] In detail, in the first raw water supply step (S1), sewage containing organic matter and ammonia is supplied, and in the second raw water supply step (S3), nitrate concentrated water rich in nitrate is preferably, for example, membrane concentrated water, more preferably is concentrated water from a nanofiltration membrane or reverse osmosis membrane, and most preferably is concentrated water from a reverse osmosis membrane.

[0051] Here, membrane concentrate may be the concentrate generated during the process of reusing sewage effluent from which most pollutants, such as organic matter, have been removed through a biological treatment process. In other words, it is the concentrate that cannot pass through nanofiltration membranes or reverse osmosis membranes, which are used to filter sewage effluent once again for reuse.

[0052] At this time, it is preferable that the membrane concentrate contains 40 mg / L or more of nitrate (NO3), and more preferable that it contains 60 mg / L or more.

[0053] Meanwhile, the first biological reaction stage (S2) is operated under anaerobic conditions, and the second biological reaction stage (S4) is operated under anoxic conditions.

[0054] Anaerobic conditions refer to a state where there is no bound oxygen with dissolved oxygen of less than 0.1 mg / L, and anoxic conditions refer to a state where there is no bound oxygen such as NOx, even though the dissolved oxygen is less than 0.1 mg / L.

[0055] The aforementioned steps, namely the first raw water supply step (S1), the first biological reaction step (S2), the second raw water supply step (S3), the second biological reaction step (S4), the sedimentation step (S5), and the discharge step (S6), can be performed in a Sequencing Batch Reactor (SBR).

[0056] In addition, in the first biological reaction stage (S2) operated under anaerobic conditions and the second biological reaction stage (S4) operated under anoxic conditions, it is desirable for partial denitrification organisms (PDO) and anaerobic ammonium oxidation organisms (Amammox) to grow together so as to remove organic matter and nitrogen, and it is more desirable for denitrifying phosphorus accumulating organisms (DPAO) to grow together so as to remove phosphorus components.

[0057] Partial denitrification organisms (PDOs) utilize organic matter as an electron donor to reduce nitrate (NO3) to nitrite (NO2) under anaerobic conditions.

[0058] (Reaction Equation 1)

[0059] Here, partial denitrification organisms (PDOs) may be one or more selected from the group consisting of Pseudomonas, Bacillus, Thauera, Hypomicrobium, Agrobacterium, Acinetobacter, Propionobacterium, Rhizobium, Thiobacillus, Alcaligenes, Pseudomonas fluorescens, Pseudomonas Aeruginosa, Pseudomonas denitrificans, Acidovorax, Dokdonella, Flavobacterium, Rubrivivax, Terrimonas ferruginea, Terrimonas lutea, Rhodobacter, Lysobacter, Staphylococcus, Paracoccus denitrificans, Denitratisoma, etc.

[0060] Anaerobic ammonium oxidation organisms (Amammoxes) act as electron donors for NH4 under anaerobic conditions without an organic carbon source. + , as an electron acceptor NO2 - Converted into an inert gas using and inorganic carbon (HCO3 - Synthesizes carbon within the cell by reducing ).

[0061] (Reaction Equation 2)

[0062] One or more of these anaerobic ammonium oxidation organisms (Amammox) may be selected from the group consisting of Candidatus Brocadia anammoxidans, Candidatus Kuenenia stuttgartiensis, Candidatus Scalindua wagneri, Candidatus Anammoxoglobus propionicus, and Planctomycete KSU-1.

[0063] In addition, denitrifying phosphorus accumulating organisms (DPAOs) use organic matter in place of oxygen under anaerobic conditions and release phosphorus, and under anoxic conditions, they use nitrate (NO3) as an electron acceptor and utilize the released phosphorus.

[0064] One or more of these denitrifying phosphorus accumulating organisms (DPAOs) may be selected from the group consisting of Ca. Accumulibacter, Ca. Dechloromonas, Zoogloea, Pseudomonas, Thauera, Paracoccus, and Flavobacterium.

[0065] Meanwhile, in the discharge step (S6), the treated water can be discharged to a value of approximately 35 to 50% of the effective volume of the reactor.

[0066]

[0067] FIG. 1 is a schematic diagram illustrating the mechanism of removing organic matter and nutrients by microorganisms according to the present invention. With reference to FIG. 1, the reactions of denitrifying phosphorus accumulating organisms (DPAO), partial denitrification organisms (PDO), and anaerobic ammonium oxidation organisms (Amammox) under anaerobic or anoxic conditions will be described.

[0068] First, in the anaerobic stage, denitrifying phosphorus-accumulating organisms (DPAOs) utilize the supplied organic matter and release phosphorus. In other words, only organic matter is consumed in the anaerobic stage.

[0069] In the anaerobic conditions stage, partial denitrification organisms (PDOs) reduce nitrate (NO3) to nitrite (NO2) by utilizing organic matter. Then, anaerobic ammonium oxidation organisms (Amammoxes) synthesize intracellular carbon by using ammonia (NH4) as an electron acceptor and electron donor for the nitrite (NO2) produced by partial denitrification organisms (PDOs).

[0070] In addition, denitrifying phosphorus accumulating organisms (DPAOs) utilize nitrate (NO3) as an electron acceptor and use released phosphorus as well as phosphorus contained in the incoming raw water.

[0071] Therefore, to effectively remove ammonia, phosphorus, and organic matter, it is desirable to perform an anoxic condition stage after the anaerobic condition stage. In addition, while the supply of organic matter is required in the anaerobic condition stage, the supply of nitrate along with organic matter is required in the anoxic condition stage.

[0072] For example, when proceeding with the anaerobic condition stage, if there is a lack of organic matter, phosphorus release by denitrifying phosphorus accumulating organisms (DPAO) is not smooth, making it difficult to expect a high phosphorus removal rate; therefore, it is desirable to include at least 20 mg / L of organic matter (based on CODcr). Of course, if there is an excess of organic matter, it causes excessive phosphorus release during the anaerobic condition stage, and since using the phosphorus released during the anoxic stage requires a large amount of nitrate (NO3), there is a risk of nitrate shortage. Therefore, for effective phosphorus removal, it is desirable to control the organic matter (based on CODcr) to the range of 20-50 mg / L during the anaerobic condition stage.

[0073] When proceeding with the anaerobic condition stage, if there is no nitrate or insufficient nitrite, nitrite (NO2) is not produced sufficiently, and the removal rate of ammonia (NH4) by anaerobic ammonium oxidation organisms (Amammox) is reduced.

[0074] Also, when proceeding with the anaerobic condition stage, if there is no or insufficient organic matter, nitrite (NO2) is not produced sufficiently, and the removal rate of ammonia (NH4) by anaerobic ammonium oxidation organisms (Amammox) is reduced.

[0075] In other words, during the anaerobic condition stage, since partial denitrification organisms (PDOs) require organic matter and nitrates, and denitrifying phosphorus accumulating organisms (DPAOs) require nitrates, it is desirable to include organic matter and nitrates within an appropriate range. For example, during the anaerobic condition stage, a COD / NO3 ratio of 1.7 to 2.0 is desirable, and a range of 1.8 to 1.9 is more desirable.

[0076]

[0077] The present invention will be explained in more detail below through examples. These examples are intended solely to explain the present invention more specifically and do not limit the present invention.

[0078]

[0079] Examples

[0080] A schematic diagram of the device used in the present invention is shown in FIG. 2. As illustrated in FIG. 2, the device of the present invention comprises a reaction tank equipped with a stirrer, a first raw water supply tank for temporarily storing wastewater which is the first raw water, a second raw water supply tank for temporarily storing membrane concentrate which is the second raw water, and a plurality of pumps.

[0081] As shown in Table 1, the effective volume of the reactor is 10 L, and the seeding sludge consists of partial denitrification microorganisms (PDO), nitrogen and phosphorus simultaneous removal microorganisms (DPAO), and anaerobic ammonium oxidation microorganisms (Amammox), which were seeded at 900 mg / L, 900 mg / L, and 750 mg / L, respectively.

[0082] The device was operated as a continuous batch reaction, and after the reaction was finished, treated water equivalent to 40% of the volume of the reaction tank was discharged, and the process of supplying raw water again in the same amount as the discharged treated water was repeated.

[0083] Reactor Volume 10L Seeding Sludge - Partially Denitrifying Organisms (PDO) - Denitrifying Microorganisms (DPAO) - Anaerobic Ammonium Oxidizing Microorganisms (Anammox) 900mg / L 900mg / L 750mg / L Exchange Rate 40% of Reactor Volume Temperature 30±2℃ HRT 6.25~13.75hr DO <0.1

[0084] The first raw water, sewage, is sewage flowing into the P sewage treatment plant, and the second raw water, membrane concentrate, is concentrate generated during the process of producing recycled water by filtering the effluent of the P sewage treatment plant through a reverse osmosis (RO) membrane, and their representative water quality is as shown in Table 2.

[0085] Raw Water No. 1 (Sewage Raw Water) Raw Water No. 2 (RO Concentrated Water) NH4-N (mg / L) 32.2~37.8 (Average 34.3)-NO2 - -N(mg / L)--NO3 - -N(mg / L)0.2~0.5(average 0.3)52.5~57.3(average 54.2)PO4 3- -P(mg / L)5.8~6.3(Average 6.0)0.07~0.15(Average 0.10) -Alkalinity(CaCO3)(mg / L)320~380(Average 350)46.7~56.7(Average 55.2) -pH7.2~7.6(Average 7.4)8.1~8.4(Average 8.3) -TCODcr(mg / L)143~161(Average 152)51.3~56.7(Average 53.9)

[0086] The experiment was conducted by dividing the experiment into a total of five sections, including sections A through E, with different operating conditions, and the detailed operating conditions for each section are shown in Tables 3 through 7. First, as summarized in Table 3, in section A, a series of steps (1 cycle) consisting of a raw water inflow stage, an anaerobic condition stage, a sedimentation stage, and a discharge stage are repeated.

[0087] At this time, partial denitrification microorganisms seeded at a concentration of 900 mg / L were the dominant species in the reactor, and the first and second raw waters were supplied in a volume ratio of 1.2:1.0 within one cycle, and the organic matter / nitrate (CODcr / NO3) ratio in the anaerobic condition stage was 2.72~2.86.

[0088] Mixing Ratio (1st Raw Water:2nd Raw Water) 1.2:1.0 Microorganisms in Reactor Partially Denitrifying Microorganisms Operating Conditions: Inflow (5 min) - Anaerobic (35 min) - Sedimentation (90 min) - Discharge (20 min) Total HRT 6.25 hr Anaerobic Section C / NO3 2.72~2.86

[0089] The operating conditions for Section B are as shown in Table 4. In Section B, a series of steps consisting of a raw water inflow stage, an anaerobic condition stage, a sedimentation stage, and a discharge stage are repeated. At this time, the reactor contains a mixture of partially denitrifying microorganisms seeded at a concentration of 900 mg / L and anaerobic ammonium oxidizing microorganisms seeded at a concentration of 750 mg / L. Within one cycle, the first raw water and the second raw water were supplied in a volume ratio of 1.2:1.0, and the organic matter / nitrate (CODcr / NO3) ratio in the anaerobic condition stage is 2.74–2.90.

[0090] Mixing Ratio (1st Raw Water:2nd Raw Water) 1.2:1.0 Microorganisms in Reactor: Partially Denitrifying Microorganisms + Anammox Microorganisms Operating Conditions: Inflow (5 min) - Anaerobic (105 min) - Sedimentation (90 min) - Discharge (20 min) Total HRT 9.17 hr Anaerobic Section C / NO3 2.74~2.90

[0091] The operating conditions for Section C are as shown in Table 5. In Section C, a series of stages consisting of the first influent stage, the anaerobic stage, the second influent stage, the anoxic condition stage, the sedimentation stage, and the discharge stage are repeated. At this time, the reactor contains a mixture of partially denitrifying microorganisms seeded at a concentration of 900 mg / L and anaerobic ammonium oxidizing microorganisms seeded at a concentration of 750 mg / L. Within one cycle, the first raw water and the second raw water were supplied in a volume ratio of 1.2:1.0, with the first raw water supplied in the first influent stage and the second raw water supplied in the second influent stage. Meanwhile, the organic matter / nitrate (CODcr / NO3) ratio in the anoxic condition stage is 2.73–2.79.

[0092] Mixing Ratio (1st Raw Water:2nd Raw Water) 1.2:1.0 1st Raw Water Supply 1st Influent Stage 2nd Raw Water Supply 2nd Influent Stage Microorganisms in Reactor Partially Denitrifying Microorganisms + Anammox Microorganisms Operating Conditions 1st Influent (5 min) - Anaerobic (105 min) - 2nd Influent (5 min) - Anoxic (105 min) - Sedimentation (90 min) - Discharge (20 min) Total HRT 13.75 hr Anoxic Section C / NO 30

[0093] The operating conditions for Section D are as shown in Table 6. In Section D, a series of stages consisting of the first influent stage, the anaerobic stage, the second influent stage, the anoxic condition stage, the sedimentation stage, and the discharge stage are repeated. At this time, the reactor contains a mixture of partially denitrifying microorganisms seeded at a concentration of 900 mg / L, anaerobic ammonium oxidizing microorganisms seeded at a concentration of 750 mg / L, and nitrogen-phosphorus simultaneous removal microorganisms seeded at a concentration of 900 mg / L. Within one cycle, the first raw water and the second raw water were supplied in a volume ratio of 1.2:1.0, with the first raw water supplied in the first influent stage and the second raw water supplied in the second influent stage. Meanwhile, the organic matter / nitrate (CODcr / NO3) ratio in the anoxic condition stage is 0.

[0094] Mixing Ratio (1st Raw Water:2nd Raw Water) 1.2:1.0 1st Raw Water Supply 1st Influent Stage 2nd Raw Water Supply 2nd Influent Stage Microorganisms in Reactor Partially Denitrifying Microorganisms + Anammox Microorganisms + Microorganisms for Simultaneous Nitrogen and Phosphorus Removal Operating Conditions 1st Influent (5 min) - Anaerobic (105 min) - 2nd Influent (5 min) - Anoxic (105 min) - Sedimentation (90 min) - Discharge (20 min) Total HRT 13.75 hr Anoxic Section C / NO 30

[0095] The operating conditions of section E are as shown in Table 7. In section D, a series of stages consisting of a first influent stage, an anaerobic stage, a second influent stage, an anoxic condition stage, a sedimentation stage, and a discharge stage are repeated. At this time, the reactor contains a mixture of partially denitrifying microorganisms seeded at a concentration of 900 mg / L, anaerobic ammonium oxidizing microorganisms seeded at a concentration of 750 mg / L, and nitrogen and phosphorus simultaneous removal microorganisms seeded at a concentration of 900 mg / L.

[0096] In one cycle, the first raw water and the second raw water were supplied in a volume ratio of 1.2:1.0, with the first raw water being supplied in a divided manner: 0.7 in the first inflow stage and the remaining 0.5 in the second inflow stage.

[0097] The second raw water was supplied only at the second inflow stage, and the organic matter / nitrate (CODcr / NO3) ratio at the anaerobic condition stage is 1.25 to 1.30.

[0098] Mixing Ratio (1st Raw Water: 2nd Raw Water) 1.2:1.0 Split supply of 1st raw water 1st Influent Stage 0.7 : 2nd Influent Stage 0.5 Supply of 2nd raw water 2nd Influent Stage Microbial Part in Reactor: Denitrifying microorganisms + Anammox microorganisms + Nitrogen and phosphorus simultaneous removal microorganisms Operating Conditions: 1st Influent (5 min) - Anaerobic (105 min) - 2nd Influent (5 min) - Anoxic (105 min) - Sedimentation (90 min) - Discharge (20 min) Total HRT 13.75 hr Anoxic Section C / NO3 1.25~1.30

[0099] Figure 3 shows the results of ammonia concentration, nitrate concentration, nitrite concentration, and phosphorus concentration for raw water and effluent for each section, Figure 4 shows the results of ammonia removal rate, nitrate removal rate, nitrite removal rate, and phosphorus removal rate for raw water and effluent for each section, and Figure 5 shows the results of COD concentration and removal rate for raw water and effluent for each section. Referring to Figures 3 to 5, in Section A, nitrite, which was not contained in the influent raw water—that is, the mixture consisting of sewage, the first raw water, and RO concentrate, the second raw water—increased to a range of 22.1–23.1 mg / L. However, the removal rates of ammonia and phosphorus were negligible, and it was found that about 80% of organic matter was removed.

[0100] This is because Section A is operated under anaerobic conditions and partial denitrification microorganisms are the dominant species, so the organic matter contained in the raw water was used as an electron donor to reduce nitrate (NO3) to nitrite (NO2).

[0101] In section B, nitrite, which was not present in the influent raw water—that is, the mixture consisting of the first raw water, sewage, and the second raw water, RO concentrate—was detected in the range of 0.5–2.2 mg / L, and it was found that ammonia was removed by 55–96% and organic matter by about 78%. However, the removal rate of phosphorus was 1–2.5%, meaning it was hardly removed.

[0102] Section B operates under anaerobic conditions, where partial denitrification microorganisms and Anammox microorganisms coexist. Consequently, organic matter contained in the raw water is utilized by partial denitrification microorganisms as an electron donor to reduce nitrate (NO3) to nitrite (NO2), while Anammox microorganisms convert ammonia (NH4) as an electron donor and the generated nitrite (NO2) into nitrogen, an inert gas, by utilizing the generated nitrite as an electron acceptor.

[0103] Meanwhile, in section C, nitrite, which was not contained in the influent raw water, that is, the mixture consisting of the first raw water, sewage, and the second raw water, RO concentrate, was detected in the range of 1.3–2.2 mg / L, and ammonia showed a removal rate of 95–98%, organic matter 75–79%, and phosphorus 0.6–2.0%, which was similar to the results in section B.

[0104] There is no anaerobic condition stage in section B, whereas an anaerobic condition stage proceeds in section C, and there is a difference in that in section B, the first raw water, sewage, and the second raw water, RO concentrate, are supplied simultaneously, whereas in section C, the first raw water, sewage, is supplied before the anaerobic condition stage, and the second raw water is supplied between the anaerobic condition stage and the anoxic condition stage.

[0105] However, since partial denitrification microorganisms require organic matter to reduce nitrate (NO3) to nitrite (NO2), and Anammox microorganisms require nitrite (NO2) as an electron acceptor, ammonia and organic matter are not substantially consumed until the RO concentrate, which is the second raw water rich in nitrate (NO3), is supplied.

[0106] Ultimately, during the anaerobic condition stage, ammonia and organic matter are not changed, and in the anoxic condition stage after the second raw water, RO concentrate, is supplied, nitrite (NO2) is produced by partial denitrification microorganisms, and Anammox microorganisms consume ammonia (NH4) by using the produced nitrite (NO2) as an electron acceptor.

[0107] Furthermore, in section D, removal rates ranged from 70 to 97% for ammonia, 81 to 83% for organic matter, and 23 to 84% for phosphorus. Also, nitrite (NO2) was not detected in reality, but nitrate (NO3) was detected in the range of 7.2 to 10.2 gm / L.

[0108] In addition, in Section D, as the operating period increases, the phosphorus removal rate increases, while the ammonia removal rate shows a slightly decreasing trend.

[0109] In section D, the nitrogen and phosphorus simultaneous removal microorganisms prepared by pre-culturing were formed, and as these nitrogen and phosphorus simultaneous removal microorganisms gradually grew, the removal rate of phosphorus also increased.

[0110] That is, in the anaerobic condition stage, the nitrogen and phosphorus simultaneous removal microorganisms use the organic matter of the supplied wastewater and then release phosphorus, and in the anoxic condition stage, they grow by using nitrate (NO3) as an electron acceptor and utilizing the released phosphorus and the phosphorus contained in the raw water.

[0111] Of course, during the anaerobic conditions, partial denitrification microorganisms reduce nitrate (NO3) to nitrite (NO2) while utilizing some organic matter, and Anammox microorganisms utilize ammonia (NH4) as an electron acceptor and electron donor for the nitrite (NO2) produced by the partial denitrification microorganisms.

[0112] Meanwhile, the supply ratio of organic matter and nitrate (NO3) is important during the anaerobic condition stage. During the anaerobic condition stage, only partial denitrification microorganisms utilize organic matter, while nitrogen and phosphorus simultaneous removal microorganisms and partial denitrification microorganisms consume nitrate (NO3). Additionally, Anammox microorganisms consume nitrite (NO2) and ammonia, producing nitrate (NO3) as a byproduct.

[0113] Therefore, during the anaerobic conditions, if organic matter is insufficient, the reduction of nitrate (NO3) by partial denitrification microorganisms becomes inefficient, which reduces the ammonia (NH4) removal capacity of Anammox microorganisms.

[0114] Ultimately, in the case of section D, the first raw water, which is sewage containing organic matter, is supplied in its entirety before the anaerobic condition stage begins. Therefore, the nitrogen and phosphorus simultaneous removal microorganisms have sufficient organic matter to release phosphate, and can reuse the phosphate during the anoxic condition stage, thereby increasing the phosphorus removal rate. However, the organic matter in the second raw water supplied before the anoxic condition stage begins is difficult to decompose, making it difficult for partial denitrification microorganisms to utilize. Furthermore, since the organic matter supplied before the anaerobic condition stage has been consumed in excess by the nitrogen and phosphorus simultaneous removal microorganisms, there is a shortage of organic matter during the anoxic condition stage.

[0115] Next, in section E, removal rates ranged from 82–87% for ammonia, about 83% for organic matter, and 83–85% for phosphorus. Compared to section D, it was confirmed that the removal rates of organic matter and phosphorus remained at similar levels while the removal rate of ammonia improved and remained stable.

[0116] It is expected that this is because, unlike in section D, the first raw water containing organic matter was injected in divided portions in section E.

[0117] That is, the total volume of the first raw water supplied in one cycle is divided into 0.7:0.5, and the first raw water corresponding to 0.7 is supplied during the first influent stage, which is before the anaerobic condition stage, and the first raw water corresponding to the remaining 0.5 is supplied during the second influent stage, which is before the anoxic condition stage. Then, during the anoxic condition stage, the supply of insufficient organic matter induces the reduction of nitrate (NO3) by partial denitrification microorganisms, and as a result, the ammonia (NH4) removal capacity by Anammox microorganisms is improved.

[0118] However, the removal rate of ammonia did not reach 90%, and the nitrate (NO3) concentration in the effluent was also relatively high at 4 mg / L or higher. This is because the organic matter / nitrate (CODcr / NO3) ratio in the anaerobic condition stage was in the range of 1.25 to 1.30, which was somewhat low. Therefore, in order to further increase the removal rate of ammonia and phosphorus, it is advisable to adjust the organic matter / nitrate (CODcr / NO3) ratio in the anaerobic condition stage to a range of 1.7 to 2.0, and more preferably to a range of 1.8 to 1.9.

[0119] For example, this can be achieved by increasing the supply of organic matter or decreasing the supply of nitrates.

[0120]

[0121] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited thereto and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

1. The first biological reaction step (S2), the second biological reaction step (S4), the sedimentation step (S5), and the discharge step (S6) proceed sequentially, The first biological reaction step (S2) above is operated under anaerobic conditions, and The above second biological reaction step (S4) is operated under anaerobic conditions, and A wastewater treatment method using microorganisms, characterized in that the first biological reaction step (S2) and the second biological reaction step (S4) are performed in a Sequencing Batch Reactor (SBR).

2. In Paragraph 1, A wastewater treatment method using microorganisms, characterized by further including a step of supplying raw water at least once prior to the second biological reaction step (S4).

3. In Paragraph 2, It includes a first raw water supply step (S1) for supplying first raw water prior to the first biological reaction step (S2), and A wastewater treatment method using microorganisms, characterized by further including a second raw water supply step (S3) for supplying second raw water between the first biological reaction step (S2) and the second biological reaction step (S4).

4. In Paragraph 3, A wastewater treatment method using microorganisms characterized by the coexistence of partial denitrification microorganisms, anaerobic ammonium oxidation microorganisms, and nitrogen and phosphorus simultaneous removal microorganisms in the above-mentioned Sequencing Batch Reactor (SBR).

5. In Paragraph 4, The above partially denitrifying microorganisms are one or more species selected from the group consisting of Pseudomonas, Bacillus, Thauera, Hypomicrobium, Agrobacterium, Acinetobacter, Propionobacterium, Rhizobium, Thiobacillus, Alcaligenes, Pseudomonas fluorescens, Pseudomonas Aeruginosa, Pseudomonas denitrificans, Acidovorax, Dokdonella, Flavobacterium, Rubrivivax, Terrimonas ferruginea, Terrimonas lutea, Rhodobacter, Lysobacter, Staphylococcus, Paracoccus denitrificans, Denitratisoma, etc. The above anaerobic ammonium-oxidizing microorganisms are Planctomycetes, Candidatus B., or Anammoxidans, and A wastewater treatment method using microorganisms characterized by the fact that the above-mentioned microorganisms for simultaneous removal of nitrogen and phosphorus are selected from the group consisting of Ca. Accumulibacter, Ca. Dechloromonas, Zoogloea, Pseudomonas, Thauera, Paracoccus, and Flavobacterium.

6. In Paragraph 4, A wastewater treatment method using microorganisms characterized in that the first raw water is wastewater and the second raw water is membrane concentrate.

7. In Paragraph 6, A wastewater treatment method using microorganisms characterized in that the second raw water is concentrated water from a nanofiltration membrane or a reverse osmosis membrane.

8. In Paragraph 7, A wastewater treatment method using microorganisms, characterized in that the above-mentioned second raw water is concentrated water generated during the process of filtering wastewater treatment effluent through a nanofiltration membrane or a reverse osmosis membrane.

9. In Paragraph 8, A wastewater treatment method using microorganisms, characterized in that the first raw water is supplied prior to the first biological reaction step (S2) and between the first biological reaction step (S2) and the second biological reaction step (S4).

10. In Paragraph 6, A sewage treatment method characterized in that the first biological reaction step (S2) contains 20 mg / L or more of organic matter.

11. In Paragraph 6, A sewage treatment method characterized by maintaining the organic matter / nitrate ratio in the range of 1.7 to 2.0 in the second biological reaction step (S4) above.

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