Microorganism carrier

Abstract

To provide a carrier which has good microorganism fixation, capable of growing rapidly and stably, and capable of reducing weight.SOLUTION: A carrier for carrying microorganisms is composed of calcium silicate hydrate-containing materials, and capable of producing nitrogen gas from one or more of ammonia-form nitrogen and nitrite-form nitrogen.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a carrier for supporting microorganisms. [Background technology]

[0002] Harmful substances and pollutants are contained in wastewater from industries such as industry, agriculture, livestock farming, and fisheries, as well as in wastewater from sewage treatment plants and human waste treatment plants. Examples of such substances include nitrogen, and techniques for removing nitrogen from wastewater, such as wastewater, using the metabolism of microorganisms have been studied. In recent years, attention has been focused on a technique for removing ammonia nitrogen and nitrite nitrogen from wastewater as nitrogen gas using anammox bacteria, which are anaerobic and autotrophic bacteria.

[0003] However, anammox bacteria grow slowly even in favorable environments, and because their microbial aggregates (e.g., flocs, granules, sludge, etc.) are light, they are washed away by the water flow of the treated water, resulting in problems such as a slow start-up of biological treatment and a long time required for stabilization. To solve these problems, technologies have been considered that support anammox bacteria on a carrier to produce a microbial support with good settling properties and prevent it from washing away. Examples of carriers that have been proposed include carbon particles (Patent Document 1), basalt fibers (Patent Document 2), and ring-shaped bodies formed by bending a fiber thread and closing both ends (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-104009 [Patent Document 2] Patent Publication No. 2021-45123 [Patent Document 3] International Publication No. 2019 / 202756 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the carriers used in conventional techniques not only have low microbial adhesion, but also make it difficult to rapidly and stably grow microorganisms. In addition, the weight of the carriers places a heavy load on reactors and other equipment, making them economically disadvantageous. The object of the present invention is to provide a carrier that has good adhesion properties for microorganisms and allows them to grow rapidly and stably, a microbial-attached body that supports microorganisms on the carrier, and a water purification method using the same. [Means for solving the problem]

[0006] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that calcium silicate hydrate-containing materials have good adhesion and fixation properties for specific microorganisms, enable rapid and stable proliferation, and are lightweight. They have also found that by supporting specific microorganisms on a calcium silicate hydrate-containing material to form a microbial-attached material, it is possible to prevent the microorganisms from being washed away by water currents, enable economical water purification, and furthermore, remove not only nitrogen but also phosphorus from wastewater at the same time.

[0007] That is, the present invention provides the following [1] to [9]. [1] A carrier for supporting microorganisms, which is made of a calcium silicate hydrate-containing material and has the function of generating nitrogen gas using one or more of ammonia nitrogen and nitrite nitrogen as raw materials. [2] The calcium silicate hydrate-containing material has a density of 0.8 to 2.5 g / cm 3 The carrier for supporting microorganisms according to [1] above, [3] The microorganism-supporting carrier according to [1] or [2] above, wherein the calcium silicate hydrate-containing material has a porosity of 10 to 80%. [4] The carrier for supporting microorganisms according to any one of [1] to [3] above, wherein the calcium silicate hydrate-containing material has a pH of 7 to 11 when a suspension containing 5 times the mass of distilled water relative to the material is prepared. [5] The carrier for supporting a microorganism according to any one of [1] to [4] above, wherein the microorganism is an anammox bacterium. [6] A microbial-attached body comprising a carrier for supporting microorganisms according to any one of [1] to [4] above, and carrying microorganisms capable of producing nitrogen gas using one or more of ammonia nitrogen and nitrite nitrogen as raw materials. [7] The microbial adherent described in [6], wherein the microorganism is an anammox bacterium. [8] A water purification method, in which the microbial adherent material according to [6] or [7] is used to purify water containing one or more selected from ammonia nitrogen and nitrite nitrogen. [9] The water purification method according to [8], comprising a step of adjusting the pH during purification to 6 to 10. [Effects of the Invention]

[0008] The carrier for supporting microorganisms of the present invention exhibits good adhesion and fixation properties for microorganisms, allows for rapid and stable proliferation, and is lightweight. The microbial-attached material of the present invention not only prevents the outflow of microorganisms due to water flow, but also places a small load on equipment such as reaction tanks, making it economically advantageous for use in water purification. Furthermore, it can simultaneously remove not only nitrogen but also phosphorus contained in wastewater. Therefore, the water purification method of the present invention is useful for purifying wastewater such as wastewater from industry, agriculture, livestock farming, fisheries, etc., and polluted water from sewage treatment plants and sewage treatment plants. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of a water purification device applicable to the present invention. [Figure 2] FIG. 10 is a schematic diagram showing another example of a water purifier applicable to the present invention. [Figure 3] FIG. 10 is a schematic diagram showing another example of a water purifier applicable to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. [Microorganism-supporting carrier] The carrier for supporting microorganisms of the present invention is made of a calcium silicate hydrate-containing material, which allows for good adhesion and fixation of microorganisms, rapid and stable proliferation, and light weight.

[0011] (Calcium silicate hydrate-containing material) As used herein, the term "calcium silicate hydrate" is a type of silicate, and is a general term for compositions in which calcium oxide, silicon dioxide, and water are combined in various composition ratios.

[0012] Calcium silicate hydrates can be classified into, for example, tobermorite, xonotlite, CSH gel, foshagite, gyrolite, hillebrandite, and wollastonite depending on their crystal structures. In the present invention, one or more calcium silicate hydrate-containing materials may be contained.

[0013] Tobermorite is a crystalline calcium silicate hydrate, e.g., Ca5·(SiO 18 H2)·4H2O (plate-like form), Ca5·(SiO 18 H2) (plate-like morphology), Ca5·(SiO 18 It has a chemical composition such as H2·8H2O (fibrous form). Xonotlite is a crystalline calcium silicate hydrate, e.g., Ca6·(SiO 17 )·(OH)2 (fibrous form) etc. CSH gel has the chemical composition αCaO·βSiO2·γH2O (where α / β = 0.7 to 2.3, γ / β = 1.2 to 2.7). For example, calcium silicate hydrate with the chemical composition 3CaO·2SiO2·3H2O can be mentioned. Foshagite has a chemical composition such as Ca4(SiO3)3(OH)2. Gyrolite is (NaCa2)Ca 14 (Si 23 Al)O 60It has a chemical composition such as (OH)8·14H2O. Hillebrandite has the chemical composition Ca2SiO3(OH)2. Wollastonite has a chemical composition of CaO·SiO2 (fibrous or columnar). Among these, tobermorite is preferred from the viewpoints of availability and economy.

[0014] The calcium silicate hydrate-containing material used in the present invention may be a natural mineral, cement hydrate, or hardened cement separated from waste concrete. However, from the viewpoint of ease of availability, lightweight aerated concrete (ALC) containing tobermorite as its main component may be used. Here, in this specification, "lightweight aerated concrete" refers to a material consisting of tobermorite and unreacted silica. The proportion of tobermorite in lightweight aerated concrete is typically about 50 to 80% by volume, with the entire solid phase excluding the voids inside the lightweight aerated concrete being taken as 100% by volume. Furthermore, from the viewpoint of promoting the use of waste materials, scraps and waste materials of lightweight aerated concrete generated during the manufacturing process of lightweight aerated concrete or at construction sites may be used. Furthermore, scraps and waste materials of moisture-retaining materials containing xonotlite may also be used.

[0015] Lightweight aerated concrete can be obtained, for example, by autoclaving raw materials (for example, a hardened body made from a mixture of these) containing silica powder, cement, quicklime powder, a foaming agent (for example, aluminum powder), water, etc.

[0016] The calcium silicate hydrate-containing material is preferably porous. By making the material porous, microorganisms can penetrate into the interior of the material, which not only prevents the outflow of microorganisms due to water flow but also allows a larger number of microorganisms to adhere. Furthermore, when anammox bacteria are used as the microorganisms, the frequency of contact between oxygen and anammox bacteria is reduced, allowing the anammox bacteria to grow quickly and stably even in a relatively aerobic environment. In addition, the density is reduced, allowing for weight reduction. An example of a porous calcium silicate hydrate-containing material is the lightweight aerated concrete described above. The porous calcium silicate hydrate-containing material preferably has the following properties:

[0017] The calcium silicate hydrate-containing material preferably has a porosity of 10 to 80%, more preferably 15 to 80%, and even more preferably 20 to 75%. Such a porosity allows microorganisms to penetrate deep into the material, preventing the outflow of microorganisms due to water flow and allowing a greater number of microorganisms to adhere. Furthermore, when anammox bacteria are used as the microorganisms, the frequency of contact between oxygen and the anammox bacteria is reduced, allowing the anammox bacteria to grow rapidly and stably even in a relatively aerobic environment. In addition, the density is reduced, allowing for further weight reduction. Herein, "porosity" refers to the ratio of the total volume of voids to the total volume of the carrier. Porosity can be measured by mercury intrusion porosimetry. The porosity is calculated according to the following (Equation 1):

[0018] (Formula 1) Porosity (%)=100×[1-(A / B)]

[0019] The symbols in the formula are as follows: A: Density of the support measured by mercury intrusion porosimetry without mercury being intruded into the pores B: Density of the support when mercury is forced into the pores, measured by mercury intrusion porosimetry

[0020] The calcium silicate hydrate-containing material preferably has a density of 0.8 to 2.5 g / cm 3 and more preferably 0.9 to 2.4 g / cm 3 and more preferably 1.0 to 2.3 g / cm 3 If the density is within the above range, the outflow of the microbial carrier due to the water flow can be prevented, making it possible to increase the amount of water treated per unit time, and since the carrier is lightweight, the load on the reaction tank is small, making it possible to purify water economically. Here, in this specification, "density" refers to the density of the carrier when mercury is injected into the pores by mercury porosimetry.

[0021] The carrier preferably has a pH of 7 to 11, more preferably 7.5 to 11, and even more preferably 8 to 11, as measured by the following method. If the pH is within this range, microorganisms can be supported on the carrier surface without inhibiting their growth.

[0022] (pH measurement) Distilled water is added in an amount 5 times by mass relative to the carrier, and the mixture is shaken for 30 minutes. A glass electrode is immersed in the resulting suspension, and the pH is measured after 30 seconds.

[0023] The suspension may be shaken at any speed that allows the carrier to be sufficiently mixed with the distilled water, for example, 100 rpm. The measurement temperature is usually room temperature, for example, 23°C.

[0024] The calcium silicate hydrate-containing material used in the present invention is preferably a granular material from the viewpoints of supporting microorganisms, rapid and stable growth, and preventing the microbial support or carrier from leaking out. Here, in this specification, the term "granular material" means an aggregate of powder, an aggregate of granules, or an aggregate containing powder and granules. For example, when lightweight aerated concrete is used, the granules of calcium silicate hydrate-containing material may be obtained by crushing the lightweight aerated concrete, and the crushed material may have aggregate (including aggregate whose properties have changed due to the hydration of cement) removed.

[0025] When the calcium silicate hydrate-containing material is granular, it preferably has a longitudinal dimension of 100 mm or less, and more preferably satisfies the following requirements: By doing so, it becomes easier to support microorganisms, allowing for rapid and stable growth, and also reduces the weight, thereby reducing the load on the reaction vessel. (1) The proportion of granular material having a particle size of 0.6 mm or more but less than 5.00 mm as measured by a sieve is usually 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, from the viewpoint of the permeability of the treated water in the reaction tank and the prevention of outflow of the carrier. If the proportion is less than 50% by mass, the function of retaining microorganisms is likely to be impaired. (2) The proportion of granular material having a particle size of less than 0.6 mm as determined by sieving is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 6% by mass or less, and particularly preferably 4% by mass or less. The lower limit of the proportion is not particularly limited, but from the viewpoint of ease of availability, it is preferably 0.5% by mass, more preferably 0.8% by mass. If the particle size is too small, the microbially attached material will easily float and flow out, which is undesirable. (3) The proportion of granular material having a particle size of more than 5 mm as determined by sieving is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 10% by mass or less. If the particle size is too large, the granular material may not absorb water throughout the particle, resulting in particles with a low specific gravity that may easily flow out. Furthermore, the specific surface area may decrease, potentially reducing the amount of microorganisms that can be supported. The lower limit of the above proportion is not particularly limited and may be 0% by mass.

[0026] (microorganisms) The microorganisms applicable to the present invention have the ability to produce nitrogen gas using one or more materials selected from ammonia nitrogen and nitrite nitrogen as raw materials. Here, in this specification, "ammonia nitrogen" refers to the nitrogen atoms constituting ammonia and / or ammonium salts and chemical species containing them. Furthermore, "nitrite nitrogen" refers to the nitrogen atoms constituting nitrite and / or nitrite salts and chemical species containing them.

[0027] The microorganism is not particularly limited as long as it uses at least one of ammonia nitrogen and nitrite nitrogen as a raw material and produces at least one of nitrogen gas and nitrite nitrogen, and may be aerobic or anaerobic. Examples of such microorganisms include ammonia-oxidizing bacteria selected from the genera Nitrosomonas, Nitrosococcus, Nitrosospira, Nitrosolubus, Brevibacillus, and Xanthomonas; and anammox bacteria. One or more types of microorganisms can be used, and ammonia-oxidizing bacteria and anammox bacteria can be used in combination. Alternatively, for example, denitrifying bacteria can be used to reduce nitrate nitrogen produced by anammox bacteria in the presence of BOD (organic matter), converting it to nitrogen gas via nitrite nitrogen. Herein, "nitrate nitrogen" refers to the nitrogen atom constituting nitric acid and / or nitrates, as well as chemical species containing the same.

[0028] Among these, anammox bacteria are preferred because they have good affinity with the carrier of the present invention and can directly convert ammonia nitrogen and nitrite nitrogen into nitrogen gas. Herein, the term "anammox bacteria" as used herein is not particularly limited, but refers to, for example, anaerobic autotrophic bacteria that cause an anammox reaction in the stoichiometric ratio of the following (Equation 2).

[0029] (Formula 2) NH4 + + 1.32 NO2 - + 0.066 HCO3 - + 0.13 H + → 1.02 N2+ 0.26 NO3 - + 0.066 CH2O0.5 N 0.15 + 2.03 H2O

[0030] In this way, anammox bacteria can directly convert harmful ammonia nitrogen and nitrite nitrogen in water into harmless nitrogen gas, and have the denitrification ability to release up to 89% of the nitrogen from the water out of the system.

[0031] The microorganisms are not limited to isolated bacteria, but may be aggregates, mixtures, or supports of anammox bacteria grown in an existing anammox reactor, or may be mixed-cultured microbial communities or microbial communities derived from environmental samples. Here, "mixed culture" as used herein refers to the simultaneous cultivation of two or more microbial species in a single system. Furthermore, "environmental samples" refer to samples collected from environments such as soil, groundwater, rivers, and lakes. For example, in the case of soil, samples may include samples of soil samples.

[0032] [Microbial adhesion body] The microbial adhering material of the present invention is a carrier for supporting microorganisms described above, which supports microorganisms capable of producing nitrogen gas using one or more materials selected from ammonia nitrogen and nitrite nitrogen as raw materials. The microbial-attached material of the present invention has good adhesion of microorganisms to the carrier of the present invention, making it possible to prevent the microorganisms from being washed away by water currents and efficiently treat the water to be purified. Therefore, it is not necessary for all microorganisms to be attached to the surface or inside of the carrier; for example, it is acceptable for the microorganisms to accumulate together in a linear or branched chain, with at least the microorganisms at one end of the chain or some of the microorganisms located other than the ends being attached to the carrier.

[0033] The method for supporting microorganisms is not particularly limited, and various known support methods can be appropriately adopted. For example, a method of immersing the microorganism-supporting carrier of the present invention in a liquid containing microorganisms can be mentioned. Then, the carrier can be left to stand until the microorganisms attached to the surface or inside of the carrier grow. Then, by recovering the carrier, a microorganism-supported body can be obtained. When the microorganism-supporting carriers, the microorganisms, and the water to be purified are initially allowed to coexist simultaneously in a reaction tank, the ratio of (C) the microorganism-supporting carriers to (D) the microorganisms, expressed as a volume ratio [(C):(D)] of the two when the total is taken as 100, is preferably 90:10 to 10:90, more preferably 80:20 to 20:80, and even more preferably 70:30 to 30:70. By setting the ratio in this manner, the microorganisms can be sufficiently supported on the carriers, and water purification can be efficiently initiated. The specific configuration of the microorganism is as explained above. As the microorganism, anammox bacteria are preferred because they have good affinity with the carrier of the present invention and can directly convert ammonium nitrogen and nitrite nitrogen into nitrogen gas.

[0034] [Water purification method] The water purification method of the present invention uses the microbially attached material described above to purify water containing one or more forms selected from ammonia nitrogen and nitrite nitrogen. This not only decomposes ammonia nitrogen and nitrite nitrogen into nitrogen gas while preventing the outflow of microorganisms with the water flow, but also purifies the water by simultaneously adsorbing and / or insolubilizing phosphorus with the calcium contained in the carrier, if the water to be purified contains phosphorus. Here, "phosphorus" in this specification refers to an inorganic phosphorus compound. Examples of inorganic phosphorus compounds include, but are not limited to, phosphorous acid, orthophosphoric acid, and pyrophosphoric acid.

[0035] The water to be purified is not particularly limited as long as it contains at least one selected from ammonia nitrogen and nitrite nitrogen, and examples thereof include wastewater, such as wastewater discharged from industry, agriculture, livestock farming, and fisheries, wastewater from sewage treatment plants and human waste treatment plants, and digested liquid from methane fermentation processes.

[0036] The method for purifying water is not particularly limited as long as the water to be purified, the microorganisms, and the microorganism-supporting carrier of the present invention are simultaneously present in a reaction tank. For example, the following methods can be mentioned, but are not limited to these. (1) Microorganisms and the carrier for supporting microorganisms of the present invention are simultaneously introduced into a reactor filled with water to be purified, or one is introduced first and then the other. (2) The microbial adhering material of the present invention is placed in a reaction tank filled with water to be purified. (3) Microorganisms and water to be purified are introduced into a reaction tank containing the carrier for supporting microorganisms of the present invention, or one is introduced first and then the other is introduced. (4) The water to be purified is introduced into or passed through a reaction tank holding the microbially attached material of the present invention. (5) After the water to be purified, the microorganisms, and the carriers for supporting microorganisms of the present invention all coexist in the reaction tank, more carriers for supporting microorganisms are added. The specific configurations of the microorganisms and the carrier for supporting the microorganisms are as explained above.

[0037] Thus, the water purification method may be either a batch method or a flow method. In the case of a flow method, it may be either an upflow method or a downflow method. When the microorganism-supporting carrier and the microbial adhering bodies of the present invention are retained in a reaction vessel, the retaining form may be any of a fixed bed, a fluidized bed, an expanded bed and a moving bed, and is not particularly limited.

[0038] The reaction vessel may be a single-vessel type or a two-vessel type, and is not particularly limited. For example, when anammox bacteria are used as the microorganisms and a single-tank system is used, a reaction tank as shown in Figure 1 can be used. In this reaction tank, a portion of the ammonia nitrogen contained in the water to be purified is partially nitritated and oxidized to nitrite nitrogen by aeration and the action of ammonia-oxidizing bacteria [see, for example, formula (3-1)], and this nitrite nitrogen, together with ammonia nitrogen, is converted to nitrogen gas by anammox bacteria (anammox reaction), and nitrogen gas is discharged [see, for example, formula (3-2)]. That is, in the single-tank system, partial nitritation and the anammox reaction occur in the same tank, and nitrogen gas is produced from ammonia nitrogen and nitrite nitrogen.

[0039] (Formula 3-1) NH4 + + 3 / 2O2 → NO2- + 2H + + H2O (Formula 3-2) NH4 + + NO2 - → N2+ NO3 - + H2O

[0040] Furthermore, when a two-tank system is used, for example, a reaction tank as shown in Figure 2 can be used. The reaction tank has a first tank in which ammonia nitrogen contained in the water to be purified is oxidized to nitrite nitrogen by partial nitritation through aeration and the action of ammonia-oxidizing bacteria, and a second tank in which this nitrite nitrogen, together with ammonia nitrogen, is converted to nitrogen gas by anammox bacteria and the nitrogen gas is discharged. That is, in the two-tank system, the nitritation and anammox reactions occur in separate tanks, and nitrogen gas is produced from ammonia nitrogen and nitrite nitrogen.

[0041] In the present invention, the treated water obtained by purification may be used as influent for a known denitrification process, and nitrate nitrogen in the treated water may be converted to nitrogen gas by, for example, a method using denitrifying bacteria.

[0042] The pH during purification is preferably adjusted to the optimum pH for the microorganisms in order to promote the purification reaction. The pH can be set appropriately depending on the type of microorganism, but in the case of anammox bacteria, it is preferably 6 to 10, more preferably 7 to 9. The pH is a value measured at 10 to 40°C. A pH adjuster can be used to adjust the pH. Acids or alkalis can be used as pH adjusters, and acids and alkalis can be used in combination to achieve a desired pH. Examples of acids include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, as well as organic acids. Examples of alkalis include sodium hydroxide, calcium hydroxide, and potassium hydroxide. The amount of pH adjuster used can be appropriately selected depending on the type of pH adjuster.

[0043] An example of a water purifier that can be used in the present invention is shown in FIG. The water purification apparatus shown in Figure 3 is a single-tank water purification apparatus intended for water purification using the anammox reaction, and is an upflow expansion bed water purification apparatus. This water purification apparatus includes a storage tank for storing the water to be purified, an inlet pump for inflowing the water from the storage tank into a reaction tank, a reaction tank for purifying the water using the anammox reaction, and a recirculation pump for circulating the water in the reaction tank. A gas meter for detecting the amount of nitrogen gas discharged from the reaction tank is installed at the other end above the water inlet of the reaction tank. A pH meter for measuring the pH of the circulating water is installed in the piping for circulating the water in the reaction tank. A mechanism is provided for adding a required amount of acid (e.g., dilute sulfuric acid) based on the measured pH value to maintain the pH of the circulating water at a controlled value. Furthermore, a thermometer and a water temperature control mechanism are installed in the storage tank and / or reaction tank to maintain the water to be purified at the optimal temperature for the anammox reaction.

[0044] Next, an embodiment of a water purification method by anammox reaction according to the present invention using the water purification apparatus having the above configuration will be described. First, the water to be purified is introduced from the storage tank into the reaction tank by an inflow pump, and after the reaction tank is filled with water, the water is circulated within the reaction tank by a recirculation pump. Next, when using a carrier for supporting microorganisms of the present invention, the carrier for supporting microorganisms and anammox bacteria are added to the reaction tank. The order in which the carrier for supporting microorganisms of the present invention and anammox bacteria are added is not particularly limited, and both may be added simultaneously or in small amounts alternately. When a carrier for supporting microorganisms is installed in the reaction tank, anammox bacteria are added. Furthermore, instead of the carrier for supporting microorganisms in the reaction tank, the microbial adherent material of the present invention may be placed in the reaction tank or may be introduced into the reaction tank. The microbial adherent material of the present invention may be used in combination with the carrier for supporting microorganisms in the present invention and anammox bacteria.

[0045] The water in the reaction tank is circulated by a recirculation pump, and the water to be purified is subjected to the anammox reaction, which is usually carried out under anaerobic conditions and does not necessarily require aeration. As the anammox reaction progresses, the pH of the water tends to rise. Therefore, the pH of the circulating water is measured using a pH meter installed in the piping. If there is a discrepancy between the measured pH value and the pH control value, a necessary amount of acid such as dilute sulfuric acid is added to maintain the pH of the circulating water at the control value. The pH control value of the circulating water is the optimal pH described above for anammox bacteria.

[0046] Furthermore, by using the calcium silicate hydrate-containing material of the present invention as a carrier, it is possible to alleviate the sudden change in the growth environment of anammox bacteria that is caused by a sudden change in the pH of water, thereby reducing the adverse effects.

[0047] The water purification method of the present invention has been described in detail above based on the embodiments. However, the present invention is not limited to the above embodiments. Various modifications of the present invention are possible without departing from the spirit of the present invention. For example, in the above embodiments, a pH meter for measuring the pH of the circulating water is installed in the piping for circulating water in the reaction tank, but a device for measuring the phosphorus concentration of the circulating water may also be installed.

[0048] As explained above, the microorganism-supporting carrier of the present invention exhibits good adhesion and fixation of microorganisms, enabling rapid and stable proliferation, and is also lightweight. Furthermore, since the microbial-attached material of the present invention is well-supported on the carrier, it prevents the microorganisms from being washed away by the water current, allowing the treated water to pass through at a higher rate than if a carrier were not used. Furthermore, since the load on the reaction tank is small, the water purification effect of the denitrification reaction using microorganisms can be advantageously exerted over a long period of time. Therefore, the water purification method of the present invention is useful for purifying wastewater, such as wastewater from industry, agriculture, livestock farming, fisheries, etc., and wastewater from sewage treatment plants and sewage treatment plants. [Example]

[0049] The following examples will explain the present invention in more detail, but the present invention is not limited to the examples below.

[0050] The carriers used in this example are as follows: Calcium silicate hydrate-containing material: Lightweight aerated concrete was crushed and sieved to a particle size of 1-4 mm, with a density of 1.4 g / cm 3 , porosity 57%, pH 10.2 Hydroxyapatite (powder, commercially available): Granulated and sieved to particle sizes of 1-4 mm, density 3.1 g / cm 3 , porosity 19%, pH 7.4 Silica sand: Mix half of No. 2 and half of No. 3 silica sand, sieve to classify particle size to 1-4 mm, density 2.6 g / cm 3 , porosity 0.4%, pH7.2

[0051] The density and porosity were measured by mercury intrusion porosimetry using an AutoPore IV 9520 (Micromeritics, Shimadzu Corporation). The density A of the support was measured when the force of forcing mercury into the pores was 0.49 pounds per square inch and when no mercury was forcing into the pores. In addition, the density B of the carrier was measured in a state where mercury was forced into the pores under a force of 59,800 pounds per square inch.

[0052] The composition of the artificial wastewater used in this example is shown in Table 1. The total nitrogen content is made up of ammonium sulfate and sodium nitrite, and the total phosphorus content is made up of potassium dihydrogen phosphate.

[0053] [Table 1]

[0054] Example 1 and Comparative Examples 1 and 2 Using the upflow expanded bed reactor (purification system) shown in Figure 3, water was purified according to the following procedure. First, 3 L of carrier and 3 L of anammox bacteria aggregate were added to a 6 L reactor. After addition, artificial wastewater was passed through the reactor, and a water purification test was conducted over a period of 115 days. During this test, the nitrogen loading rate was changed when the nitrogen removal rate stabilized over a period of 2 to 7 days, and the phosphorus loading rate was changed when the phosphorus removal rate stabilized, to test the load the purification system could withstand. As the anammox reaction progressed, the pH of the artificial wastewater that passed through the reactor rose. Therefore, dilute sulfuric acid was added as needed to adjust the pH of the artificial wastewater flowing into the reactor to within the range of 6 to 10. On the 98th day after the start of the experiment, carriers not containing anammox bacteria were added to the reactor in an amount of 10% by volume of the initial loading amount.

[0055] The evaluation involved measuring the daily changes in microbial count and pH when calcium silicate hydrate-containing materials were used as carriers, and the daily changes in nitrogen removal rate and phosphorus removal rate due to the anammox reaction when each carrier was used, over a period of 115 days. The analytical methods for microbial count, nitrogen removal rate, and phosphorus removal rate were as follows.

[0056] (1) Microbial amount The amount of microorganisms was defined by "VSS." Here, "VSS" refers to the amount of organic matter in "SS." Also, "SS" refers to the amount of suspended solids, which is the total amount of organic matter and inorganic matter that does not dissolve in water. In this example, VSS / SS is used as an index of the amount of microorganisms. SS (g / L) was measured according to the method described in Appendix 7 of Notification No. 59 of the Ministry of the Environment and JIS K 0102, Section 14.1. VSS (g / L) was measured according to the method described in Appendix 12 of the 1997 Sewage Test Methods. The larger the VSS / SS ratio, the higher the microbial concentration per SS. If this value is 0.1 or higher, it can be determined that the start-up of the reactor is progressing.

[0057] (2) Nitrogen removal rate The nitrogen removal rate (TNRE) was calculated using the following formulas (4) to (6).

[0058] (Formula 4) NLR(gN / L d -1)= TN(mg-N / L) / 1000× 24(h / d) / HRT(h) (Formula 5) NRR(gN / L d -1 ) = Amount of nitrogen removed (mg-N / L) / 1000 × 24 (h / d) / HRT (h) (Equation 6) TNRE (%) = NRR / NLR × 100

[0059] The symbols in the formula are as follows: TN: Total nitrogen in the artificial wastewater NLR: Nitrogen Loading Rate HRT: Hydraulic residence time NRR: Nitrogen Removal Rate

[0060] The NRR was obtained by quantifying ammonium ions, nitrite ions, and nitrate ions by ion chromatography and calculating the amount of nitrogen removed.

[0061] (3) Phosphorus removal rate The phosphorus removal rate (TPRE) was calculated using the following formulas (7) to (9).

[0062] (Equation 7) PLR(gP / L d -1 )= TP(mg-P / L) / 1000× 24(h / d) / HRT(h) (Formula 8) PRR(gP / L d -1 ) = Amount of phosphorus removed (mg-P / L) / 1000 × 24 (h / d) / HRT (h) (Formula 9) TPRE(%) = PRR / PLR ×100

[0063] The symbols in the formula are as follows: TP: Total phosphorus in artificial wastewater PLR: Phosphorus Loading Rate HRT: Hydraulic residence time PRR: Phosphorus Removal Rate

[0064] PRR was obtained by quantifying phosphate ions by ion chromatography and calculating the amount of phosphorus removed.

[0065] The change in the amount of microorganisms over a period of 115 days when calcium silicate hydrate-containing material was used as a carrier was measured, and the analysis results for each period are shown in Table 2.

[0066] [Table 2]

[0067] Table 2 shows that the VSS / SS ratio was 0.1 or higher 50 to 81 days after the start of the experiment, indicating that the start-up of the reactor was progressing. Furthermore, the maximum VSS value was obtained on the 66th day, which indicates that calcium silicate enabled the rapid support and proliferation of anammox bacteria, enabling the reactor to be started up quickly. On the other hand, when hydroxyapatite or silica sand was used as the carrier, it took more than 180 days to start up, so it was confirmed that using a calcium silicate hydrate-containing material as the carrier allows the reaction tank to be started up quickly and stably. The decrease in SS was presumed to be due to the dissolution of calcium silicate hydrate.

[0068] The daily change in nitrogen removal rate due to the anammox reaction when using each carrier was measured over a period of 115 days, and the analysis results for each period are shown in Table 3.

[0069] [Table 3]

[0070] As can be seen from Table 3, when calcium silicate hydrate-containing material was used as a carrier, it showed a removal capacity close to the theoretical amount of nitrogen gas (89%) over all periods. This shows that calcium silicate hydrate-containing material is easy to support anammox bacteria, has excellent adhesion properties, and is useful for water purification. Furthermore, the amount of nitrogen gas generated tended to decrease from 90 to 97 days, but the amount of nitrogen gas generated increased when calcium silicate hydrate-containing material was re-added on the 98th day. This confirmed that calcium silicate hydrate-containing material not only does not inhibit the nitrogen removal activity of anammox bacteria, but also has the ability to promote the reaction and / or prevent the outflow of anammox bacteria.

[0071] The daily change in the phosphorus removal rate by the anammox reaction using each carrier was measured over a period of 115 days, and the analysis results for each period are shown in Table 4.

[0072] [Table 4]

[0073] Table 4 shows that when calcium silicate hydrate-containing materials are used as carriers, phosphorus can be removed with an efficiency of about 70% or more for a period of three months or more. Furthermore, by adding calcium silicate hydrate-containing material again on the 98th day, the phosphorus removal efficiency improved to nearly 80%, suggesting that the calcium eluted from the calcium silicate hydrate-containing material supplemented the phosphate ions, causing them to settle and be removed. Therefore, when the phosphorus concentration of the water to be purified does not meet the environmental standard, the phosphorus concentration of the treated water can be easily reduced by adding the carrier of the present invention.

[0074] The change in pH over time of artificial wastewater that passed through a reaction tank during an anammox reaction over 115 days when calcium silicate hydrate-containing material was used as a carrier was measured, and the analysis results for each period are shown in Table 5.

[0075] [Table 5]

[0076] Table 5 shows that in this purification system, the pH during purification was adjusted to the optimal pH for anammox bacteria and maintained approximately constant for 115 days, allowing the anammox reaction to proceed continuously and achieving high removal capacity over a long period of time.

Claims

1. A carrier for supporting a microorganism having a function of generating nitrogen gas using one or more selected from ammonia nitrogen and nitrite nitrogen as raw materials, the carrier being made of a calcium silicate hydrate-containing material, The microorganism is anammox bacteria. Support carrier.

2. The calcium silicate hydrate-containing material has a density of 0.8 to 2.5 g / cm 3 The carrier for supporting microorganisms according to claim 1, wherein

3. 3. The microorganism-supporting carrier according to claim 1, wherein the calcium silicate hydrate-containing material has a porosity of 10 to 80%.

4. The carrier for supporting microorganisms according to any one of claims 1 to 3, wherein the calcium silicate hydrate-containing material has a pH of 7 to 11 when a suspension containing 5 times the mass of distilled water relative to the material is prepared.

5. A microbial-supported body comprising a microorganism supported on a carrier for supporting microorganisms according to any one of claims 1 to 4, the microorganisms having the function of generating nitrogen gas using one or more materials selected from ammonia nitrogen and nitrite nitrogen as raw materials, The microorganism is anammox bacteria. Microbial adherens.

6. A method for purifying water, comprising using the microbial adherent material according to claim 5 to purify water containing at least one selected from the group consisting of ammonia nitrogen and nitrite nitrogen.

7. The water purification method according to claim 6, further comprising a step of adjusting the pH during purification to 6 to 10.

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