JP4925208B2 - Aerobic granule formation method, water treatment method and water treatment apparatus - Google Patents

Description

  The present invention relates to an aerobic granule formation method, a water treatment method, and a water treatment apparatus.

For the purpose of treating organic components contained in raw water such as sewage and factory wastewater, an activated sludge method using assimilation and catabolism of microorganisms is widely used. By contacting sludge, mainly microbial floc, and raw water to be treated in the presence of dissolved oxygen, the organic matter is oxidized to carbon dioxide, and the sludge and treated water are set in the sedimentation tank installed after the reaction tank. The aerobic activated sludge method for separating treated water to obtain treated water is widely used regardless of whether it is sewage or industrial wastewater because the facility is simple and wastewater with a wide concentration can be treated. However, since this activated sludge method uses floc-like bacteria and separates the treated water and flocs by gravity, the occurrence of poor sedimentation (bulking) due to filamentous fungi, actinomycetes, etc. is a problem. Moreover, since the microorganism concentration in a reaction tank cannot be taken high, the load is comparatively low as about 1.0 kgBOD / m < ³ > / day, and the point which requires a large area is also a subject.

  In recent years, in order to solve such problems, a method has been developed that allows a large amount of microorganisms to be retained in the reaction tank by introducing a filler into the reaction tank and attaching the microorganism to the filler. ing. This method can increase the load per reaction tank higher than the activated sludge method, eliminates the need for a sedimentation tank, generates many protozoa and metazoans, and can retain various organisms. It has the advantage that the amount generated is small. However, many of the packing materials added to the reaction tank are expensive, and the processing cost tends to be high, such as the need to periodically replenish the packing materials.

  On the other hand, in anaerobic treatment that does not require dissolved oxygen, the treatment rate per unit microorganism is slow, so the microorganism concentration in the reaction vessel can be reduced by self-granulating the microorganism itself to form a so-called granule with a high specific gravity. A method of dramatically increasing is used. In the method using granulated microorganisms, since a high concentration of microorganisms can be retained, the processing speed per reaction tank is faster than the method using packing, no packing is required, and the specific gravity of granules And the sedimentation rate is high, and thus has an advantage of easy solid-liquid separation. In addition to anaerobic methane fermentation, microbial groups forming such granules have been confirmed to form in a nitrifying bacteria group (see Patent Document 1) and a semi-batch reactor (SBR) in an aerobic treatment.

JP 2003-266095 A

  In a semi-batch type treatment device, (1) inflow of raw water, (2) oxygen supply and contact between raw water and microorganisms, (3) sedimentation of microorganisms, and (4) discharge of treated water in one reaction tank. Although the process is performed through the four steps, both the inflow and the discharge are performed in a short time, so that the process flow rate varies greatly, and a large flow rate adjustment tank is required in the implementation. Therefore, although it can be a simple and advantageous apparatus in a small-scale apparatus, it is often difficult to apply in a medium to large-scale apparatus. In order to solve these problems, it is preferable to adopt a continuous inflow / discharge type device configuration that has been used in many devices, but an aerobic granule that can treat organic substances and allow continuous water flow. No method has been identified for forming the shell.

  The present invention is a method for forming an aerobic granule capable of stably forming granules under aerobic conditions with a continuous water flow system.

  In addition, the present invention is a water treatment method and a water treatment apparatus capable of performing biological treatment of raw water containing an organic substance to be treated at a low cost and in a small space.

The present invention is an organic matter and iron ions are continuously introduced into together with air from the lower portion of the raw water and the reaction vessel containing 0.1 mg-Fe / L or more in contact with the microorganisms in the reactor, forming the microorganism A method for forming an aerobic granule that forms granulated granules and separates the microorganisms, treated water, and air by a gas-solid separation device provided at the top of the reaction tank , wherein the raw water C An aerobic granule forming method in which the / N ratio is adjusted to 7 or less and introduced into the reaction vessel, and the granule is formed in the reaction vessel in the presence of nitrifying bacteria under aerobic conditions. is there.

  Moreover, in the formation method of the aerobic granule, it is preferable to adjust the nitrate nitrogen generated by nitrification in the reaction tank to be in the range of 5 mg / L to 2000 mg / L.

  Moreover, in the formation method of the aerobic granule, it is preferable that the organic matter in the raw water is fermented under anaerobic conditions to convert at least a part thereof into an organic acid, and then introduced into the reaction vessel.

Further, the present invention is organic matter and iron ions and adjusting the C / N ratio of the raw water containing 0.1 mg-Fe / L or more so that the 7 or less, the C / N ratio of 7 below was adjusted raw water is continuously introduced into together with air into contact with the microorganisms in the reaction vessel from the bottom of the reaction vessel, under aerobic conditions, in the presence of nitrifying bacteria, granules obtained by granulating the microorganism A biological treatment process for biologically treating the organic matter, and a separation process for separating the biologically treated water , air, and the microorganisms by a gas-solid separation device provided at an upper part of the reaction tank. It is a water treatment method including.

Furthermore, the present invention is organic matter and iron ions and means for adjusting the C / N ratio of the raw water containing 0.1 mg-Fe / L or more so that the 7 or less, the C / N ratio of 7 below The adjusted raw water is brought into contact with microorganisms, a reaction tank for biological treatment of the organic matter, a raw water introduction means for continuously introducing the raw water from the lower part of the reaction tank, and oxygen supplied to the reaction tank An oxygen supply means, and a biologically treated treated water , a separation means for separating the oxygen and the microorganisms , provided in an upper part of the reaction tank, and in the reaction tank, aerobic conditions, It is a water treatment device that forms granules in which the microorganisms are granulated in the presence of nitrifying bacteria.

  According to the present invention, a method for forming an aerobic granule that enables granulation in the presence of nitrifying bacteria to stably form granules under aerobic conditions in a continuous water flow system. Can be provided.

  In addition, according to the present invention, by granulating microorganisms in the presence of nitrifying bacteria, it becomes possible to stably form granules under aerobic conditions in a continuous water flow system, and organic matter to be treated It is possible to provide a water treatment method and a water treatment apparatus capable of performing biological treatment of raw water containing water at a low cost and at a low cost.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  As a result of intensive studies, the present inventors have made it possible to granulate cells even when a continuous contact system is used under aerobic conditions by allowing nitrifying bacteria having a slow growth rate to coexist with bacterial groups. I found out. By using this method, microorganisms can be self-granulated to form aerobic granules with good sedimentation, and it is possible to maintain a high concentration of microorganisms without installing a filler in the reaction tank. This enables high-speed processing at a low cost.

  In this specification, “granule” refers to a self-granulated body of microorganisms and is not particularly limited. For example, the granule refers to a particle having a particle diameter of 125 μm or more. Further, sludge containing microorganisms was added to a 1 L graduated cylinder, and the ratio of SVI5 which is the sludge volume index (SVI) [mL / g] 5 minutes after the addition and SVI30 which is SVI 30 minutes after the addition (SVI5 / A material having an SVI30) of 1.2 or less is sometimes called a granule.

  Further, in the present specification, “continuously introduced” and “continuous water flow” are methods for the “batch method”, and are a method in which raw water is continuously charged into the reaction tank for operation. The supply of oxygen to the reaction vessel may be continuous or intermittent.

  Examples of raw water to be treated include food factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, and other industrial wastewater, domestic wastewater, sewage, river water, etc., and raw water containing biodegradable organic matter Can be easily applied. Moreover, when processing a biologically indegradable organic substance, a physicochemical process is performed beforehand and it can process by converting into a biodegradable substance.

  Hereinafter, taking the case where food factory wastewater is treated as an example, the aerobic granule forming method, the water treatment method, and the application of the water treatment apparatus according to the present embodiment will be described in detail.

  An example of a water treatment apparatus according to an embodiment of the present invention is schematically shown in FIG. 1 includes a raw water storage tank 10, a reaction tank 12, a solid-liquid separation tank 14, which is a separation means, a treated water tank 16, a raw water introduction pump 18 which is a raw water introduction means, and an air pump which is an oxygen supply means. 20.

  In the water treatment apparatus 1 of FIG. 1, the outlet of the raw water storage tank 10 is connected to the inlet of the reaction tank 12 via a raw water introduction pump 18 by a raw water introduction pipe, and the outlet of the reaction tank 12 is a solid-liquid separation tank by a reaction liquid pipe. 14 and the outlet of the solid-liquid separation tank 14 is connected to the inlet of the treated water tank 16 by treated water piping. An air pump 20 is connected to the lower part of the reaction tank 12 through an oxygen introduction pipe. Moreover, the lower part of the solid-liquid separation tank 14 may be connected to the downstream side of the raw water introduction pump 18 of the raw water introduction pipe via the return pump 22 by a return pipe. In the example of FIG. 1, the reaction tank 12 and the solid-liquid separation tank 14 as a separation unit are configured as separate tanks, but the reaction tank and the solid-liquid separation tank may be configured as one tank.

  The aerobic granule formation method, the water treatment method, and the operation of the water treatment apparatus 1 according to the present embodiment will be described. The raw water containing the organic matter discharged from the food factory or the like is sent to the raw water storage tank 10 to stabilize the raw water quality. At this time, when the solid water is contained in the raw water, it is preferably removed by a screen or the like. Moreover, in order to make the raw water uniform in the raw water storage tank 10, it is preferable to install a stirring device (mechanical stirring, air stirring, etc.).

  The raw water is continuously fed from the raw water storage tank 10 to the reaction tank 12 by the raw water introduction pump 18, contacted with microorganisms, and granulated granules of microorganisms in the presence of nitrifying bacteria under aerobic conditions. The organic matter in the raw water that is formed is biologically treated (biological treatment step). Since organic substances are decomposed aerobically in the reaction tank 12, an oxygen source is supplied by the air pump 20. As the oxygen source, oxygen and air can be used. At this time, the supply amount of the oxygen source is determined by the amount of organic matter in the raw water, the load of the organic matter, etc., but it should be supplied so that the dissolved oxygen concentration in the reaction tank 12 is generally in the range of 0.5 to 8 mg / L. Is preferred.

  The biologically treated reaction liquid is sent to the solid-liquid separation tank 14, and the treated water and microorganisms are separated by natural sedimentation or the like (separation step). The treated water is sent to the treated water tank 16. The sludge containing microorganisms may be taken out from the solid-liquid separation tank 14 and discarded, or may be returned to the upstream side of the reaction tank 12 by the return pump 22.

  In this embodiment, nitrifying bacteria are allowed to coexist in the microorganism group in the reaction tank 12 in order to granulate microorganisms and promote granulation. Here, in the present specification, “in the presence of nitrifying bacteria” means that ammonia nitrogen generated by nitrification in the reaction tank 12 and nitrate nitrogen derived from organic nitrogen is 5 mg / L or more. Therefore, it is preferable to adjust the amount of ammonia nitrogen generated by nitrification in the reaction tank 12 and nitrate nitrogen derived from organic nitrogen to 5 mg / L or more, and to adjust to an amount of 10 mg / L or more. More preferred. If the nitrate nitrogen is less than 5 mg / L, the amount of nitrogen to be nitrified is low in the raw water, so that the number of nitrifying bacteria that coexist in the microorganism decreases, and granule cannot be formed stably. There is a case. In the granule formation, there is almost no inhibition if the nitrogen concentration is up to about 2000 mg / L in the reaction tank 12, but adding an excessive amount of nitrogen not only costs the nitrogen agent, but also costs the pH adjuster and the treated water. This increases costs such as the cost of processing the remaining nitrate ions. Therefore, it is more preferable to adjust the amount of nitrogen added so that the concentration of nitrate nitrogen at the outlet of the reaction tank 12 is 100 mg / L or less.

  In order for nitrifying bacteria to coexist in the microorganism group in the reaction tank 12, it is preferable to adjust the C / N ratio (total organic carbon (TOC) / total nitrogen (TN)) of the raw water to 7 or less. If the C / N ratio of the raw water exceeds 7, the amount of nitrogen that is the target of nitrification in the raw water will be small, so the number of nitrifying bacteria that coexist in the microorganism will be small and stable granules cannot be formed. There is a case.

  In a normal organic matter treatment, a nitrogen source is added to the raw water so that the ratio of BOD to nitrogen concentration is about 100: 5 (that is, C / N ratio is about 7.5). This is calculated from the ratio of carbon to nitrogen in the microorganism, and the BOD component is processed by adding a necessary amount of nitrogen source. In this embodiment, this nitrogen source is added so as to be excessive. The excessively added nitrogen source is used for the treatment of the BOD component in the reaction tank 12, and then the surplus is oxidized to nitrate ions or nitrite ions by the nitrifying bacteria group.

  Here, as the nitrogen source, salts such as ammonium chloride and ammonium sulfate that dissociate into ammonium ions in water, organic nitrogen such as urea, protein, amino acids, and amines, and fertilizers containing these can be used. From the aspect, it is preferable to use ammonium chloride, ammonium sulfate, ammonia, corn steep liquor or the like. In particular, ammonia can be ammonia recovered from wastewater by ammonia stripping or the like. These components can be added in the raw water storage tank 10, the reaction tank 12, or a method of directly feeding into the organic acid fermentation tank for organic acid fermentation described later, or in the previous stage of flowing into each tank.

Since the nitrification reaction occurs in the reaction tank 12 in addition to the oxidation reaction of BOD, the alkalinity of 7.17 kg CaCO _{3 is} normally consumed per 1 kg of nitrogen. A pH measuring means such as a pH meter and a pH adjusting means such as an alkali agent adding device may be provided to inject the alkali agent or the like. By adding the alkali agent at this time, the reaction tank 12 is preferably in the range of pH 6 to 8, more preferably in the range of pH 6.5 to 7.5.

  The method in the present embodiment can be used for various organic substances, but the oil and fat may adhere to sludge and granules and adversely affect them. It is preferable to remove to about 20 mg / L or less as an n-hexane extract by an existing method such as an apparatus or an adsorption apparatus.

In addition, proteins, saccharides and the like sometimes promote the growth of filamentous fungi, inhibit granulation, or cause fiber formation on the granule surface to cause poor sedimentation. In the case of a low molecular organic acid, the formation of granules is very good. For example, as shown in FIG. 2, an organic acid fermentation tank 24 is provided before the raw water is allowed to flow into the reaction tank 12, and the raw water is previously subjected to anaerobic conditions. The method of fermenting organic matter to organic acid is very effective. The conditions reported for organic acid fermentation can be those normally reported. For example, the organic load is about 5 to 50 kg COD / m ³ / day (more preferably about 5 to 20 kg COD / m ³ / day), pH 4.5 to 7 By adjusting the pH to about 0.0 (optimal pH varies depending on the reaction temperature), ORP (redox potential) -200 to -400, and temperature 20 to 40 ° C., the inflowing organic substances are acetic acid, lactic acid, propionic acid, butyric acid. It changes to low molecular organic acids such as.

  In addition, when nutrient salts (nitrogen, phosphorus) and trace metal elements are insufficient in the raw water, these additional facilities are added to the raw water storage tank 10, the reaction tank 12, or the organic acid fermentation tank 24, or those tanks. You may provide in the front | former stage side which flows in. Food factory wastewater rarely lacks trace elements and phosphorus, so it often supplies a nitrogen source.

  In addition, seed sludge is usually charged into the reaction tank 12 at the initial start-up. At this time, as a settling accelerator, iron oxide, fly ash, diatomaceous earth, zeolite, blast furnace slag, etc. It is preferable to add a molecular flocculant because granule formation is promoted. Although it depends on the apparatus, the seed sludge concentration is preferably about 1000 to 10000 mg / L, the insoluble powder such as iron oxide is preferably about 200 to 100,000 mg / L, and the polymer flocculant is preferably about 1 to 1000 mg / L. It is also possible to divide and throw in.

In addition, when the organic substance load in the reaction tank 12 is low, granule formation is inhibited, while high load impairs the growth of filamentous fungi and the growth of nitrifying bacteria, making it difficult to maintain the shape of the granules. Therefore, the volumetric load is 1.0-30 kg BOD / m ³ / day (more preferably 2.0-20 kg BOD / m ³ / day), and the MLSS load is 0.1-3.0 kg BOD / kg MLSS / day ( More preferably 0.3 to 1.0 kg BOD / kg MLSS / day).

  It is preferable to add 0.1 to 10 mg-Fe / L, more preferably 1 to 5 mg-Fe / L, of iron ions as a granule formation accelerator in the reaction tank 12 with respect to the inflow raw water amount. This iron ion adjusts the pH value of the solution to form fine particles or colloids, assists in the aggregation of microorganisms, and promotes the formation of granules. Ordinary wastewater contains iron ions as trace metals, but when using wastewater that does not contain these or its concentration is not enough as raw water, It is preferable to add the compound. Moreover, Ca etc. which are contained in raw water may work as a granule formation accelerator.

  According to the formation method of aerobic granules according to the present embodiment, it becomes possible to stably form granules even under aerobic conditions in a continuous water flow method that has been considered difficult to form, Biological treatment can be performed in a space-saving and low-cost manner.

  Further, the water treatment method and the water treatment apparatus according to the present embodiment are a method and apparatus for biochemically treating pollutants in raw water with aerobic microorganisms, wherein the microorganisms self-granulate and settle. High-speed processing can be realized by forming good granules and holding microorganisms at a high density in the reaction vessel.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

(Examples 1 to 3, Comparative Example 1)
<Influence of raw water C / N ratio>
As an aerobic reaction tank, simulated drainage mainly composed of sodium acetate was continuously passed through a cylindrical column having an inner diameter of 64 mm and a height of 840 mm (effective volume: about 2.7 L). The dissolved oxygen concentration in the reaction vessel was adjusted to 2 to 3 mg / L. A gas-solid separator (GSS: Gas-Solid Separator) was installed at the top of the column to separate microorganisms, treated water, and air. At this time, activated sludge collected from the sewage treatment plant as seed sludge was added so as to have an initial concentration of 5000 mg MLSS / L. In addition, FeSO ₄ was added to the raw water as a granule formation accelerator so as to be 2 mg / L as Fe.

  In order to confirm the influence of the C / N ratio, the experiment was performed in four ways by changing the nitrogen addition amount. Table 1 shows the raw water composition used in this experiment.

  At a C / N ratio of 7.5 (Comparative Example 1) adjusted by normal biological treatment, filamentous fungi grew and became a floc with very poor sedimentation, and granulation was not confirmed. In Examples 1 to 3 in which the / N ratio was adjusted to 7 or less, good granules were formed. Further, in Examples 1 to 3 in which good granules were confirmed, the nitrate nitrogen concentration was confirmed to be 5 mg / L or more, and it was confirmed that nitrifying bacteria were growing in the microorganism group. Comparative Example 1 , The nitrate nitrogen concentration was 0 to 3 mg / L, and it was confirmed that nitrifying bacteria did not coexist in the microorganism group. The nitrate nitrogen concentration was measured by the method shown in JIS K0102 (1998).

(Examples 4 to 6)
<Influence of organic substances to be treated>
In order to confirm the influence of the inflowing organic matter using the same apparatus as in Example 1, the test was performed by changing the processing target organic matter. Among the target organic substances, TMAH (tetramethylammonium hydroxide) contains nitrogen in the molecule, so the nitrogen source was not added, but the other organic substances had a C / N ratio of 5 in the raw water. It adjusted so that it might become, and it passed continuously. The dissolved oxygen concentration in the reaction vessel was adjusted to 2 to 3 mg / L. Table 3 shows the raw water composition used in this experiment.

  Table 4 shows SVI after 50 days as an indicator of the presence or absence of granulation and sedimentation when each organic carbon source is used. In the raw water mainly composed of peptone-meat extract (Example 4), many granular lumps were observed in the initial stage. However, filamentous fungi propagated as the water flow continued, and finally the diameter was about 1 cm in diameter. It became a fluffy ball-like granule with poor sedimentation. In addition, the raw water mainly composed of sodium acetate (Example 5) and TMAH (Example 6) was in a favorable granule shape from the beginning, and a stable granule was formed. In Examples 5 and 6 in which good granules were confirmed, nitrate nitrogen concentrations were confirmed to be 10 to 20 mg / L and 60 to 70 mg / L, respectively, and nitrifying bacteria were growing in the microorganism group. confirmed. On the other hand, in Example 4, the nitrate nitrogen concentration was 85 to 95 mg / L.

(Example 7)
<Combination with organic acid fermentation>
In the raw water (Table 3) mainly composed of meat extract-peptone in which a slightly unstable granule was formed in Example 4, an anaerobic organic acid fermenter having a volume of 1.35 L was installed in front of the aerobic reactor. The formation of granules was observed. The operating conditions of the anaerobic organic acid fermenter were pH 5.0 to 6.5, temperature 35 ° C., organic load 6.0 kg COD / m ³ / day, and ORP-300. The aerobic reaction tank was the same as in Example 1. The raw water was continuously adjusted to have a C / N ratio of 2.7, but a part of the carbon was consumed in the fermenter, and the C / N ratio at the inlet in the reactor was 2. It was about 1. The dissolved oxygen concentration in the reaction vessel was adjusted to 2 to 3 mg / L.

  Moreover, the test was implemented also about the case where air was ventilated to an organic acid fermenter as a comparison and fermentation was not performed. The results are shown in Table 5.

  By the fermentation in the organic acid fermenter, most of the meat extract and peptone were changed to organic acids such as acetic acid and butyric acid. In a system where fermentation does not occur, a large amount of filamentous fungi were generated in the same manner as in Example 4, and granules with poor sedimentation were formed. I could not. On the other hand, good granule is formed in the system subjected to organic acid fermentation, and it is advantageous for the formation of aerobic granule to change protein-based organic matter such as meat extract and peptone to low molecular organic acid. It has been shown. Further, in a system in which good granules were confirmed, the nitrate nitrogen concentration was confirmed to be 75 to 85 mg / L, and it was confirmed that nitrifying bacteria were growing in the microorganism group. On the other hand, even in a system in which granule formation is unstable, a sufficient nitrate nitrogen concentration of 85 to 95 mg / L was maintained.

(Example 8, comparative example 2)
A GSS for separating air, sludge, and treated water was installed at the top of a cylindrical column having an inner diameter of 50 mm and a height of 3000 mm, and the raw water and air shown in Table 6 were introduced from the bottom. The raw water was continuously adjusted to have a C / N ratio of 5.6. The amount of air was 1 L / min, and the dissolved oxygen concentration in the reaction vessel was adjusted to 2 to 3 mg / L. Further, as Comparative Example 2, a test was also conducted on a system in which ATU (allylthiourea) was added to the raw water so as to be 86 μmol / L to inhibit the activity of nitrifying bacteria.

  The average values of the test results in the steady state on the 60th to 110th day from the start of water flow are shown in Table 7, and photographs showing the change in the sludge state with time are shown in FIGS. In both cases, the removal rate of TOC was as high as 95% or more, but nitrification was inhibited in the system to which ATU was added. In addition, as can be seen from FIGS. 3 and 4, in Example 8 (FIG. 3) in which ATU was not added, a clear granulated body was confirmed, whereas conditions in which nitrifying bacteria did not grow by adding ATU. In Comparative Example 2 (FIG. 4), formation of a granulated body was not confirmed. Furthermore, SVI, which is an index of sludge settling, also showed a high value in Comparative Example 2, confirming that the sludge settling in Example 8 was good. Moreover, in Example 8 in which good granules were confirmed, nitrate nitrogen was confirmed to be 20 to 30 mg / L, and it was confirmed that nitrifying bacteria were growing in the microorganism group. On the other hand, in Comparative Example 2, nitrification was inhibited by ATU, and the nitrate nitrogen concentration was a very low value of 0 to 2 mg / L. This suggests that the presence of nitrifying bacteria is a major factor in granule formation.

  In this way, by granulating microorganisms in the presence of nitrifying bacteria, it becomes possible to form granules stably under aerobic conditions with continuous water flow, and raw water containing organic matter to be treated It is clear that high-speed biological treatment can be performed at low cost with low space.

It is a schematic structure figure showing an example of the water treatment equipment concerning the embodiment of the present invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a photograph which shows transition of the sludge state in Example 8 of this invention. It is a photograph which shows transition of the sludge state in the comparative example 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Water treatment apparatus, 10 Raw water storage tank, 12 Reaction tank, 14 Solid-liquid separation tank, 16 Treated water tank, 18 Raw water introduction pump, 20 Air pump, 22 Return pump, 24 Organic acid fermentation tank.

Claims (5)

The organic matter and iron ions are continuously introduced into together with air from the lower portion of the raw water and the reaction vessel containing 0.1 mg-Fe / L or more in contact with the microorganisms in the reaction vessel was granulated said microorganism granulated And forming the aerobic granule by separating the microorganism, the treated water and the air by a gas-solid separation device provided at the top of the reaction tank , wherein the C / N ratio of the raw water is determined. A method for forming an aerobic granule, characterized in that the granule is adjusted to 7 or less and introduced into the reaction vessel, and the granule is formed in the reaction vessel in the presence of nitrifying bacteria under aerobic conditions. . A method for forming an aerobic granule according to claim 1,
A method for forming an aerobic granule, comprising adjusting the nitrate nitrogen generated by nitrification in the reaction tank to be in a range of 5 mg / L to 2000 mg / L. A method for forming an aerobic granule according to claim 1 or 2,
A method for forming an aerobic granule, wherein the organic matter in the raw water is fermented under anaerobic conditions, and at least a part thereof is converted into an organic acid, and then introduced into the reaction vessel. Organic matter and iron ions and adjusting the C / N ratio of the raw water containing 0.1 mg-Fe / L or more so that the 7 or less,
The C / N ratio 7 introduced continuously the raw water is adjusted to together with air from the lower portion of the reaction vessel below is contacted with microorganisms in the reactor, under aerobic conditions, in the presence of nitrifying bacteria, A biological treatment step of forming a granulated granule and biologically treating the organic matter;
A separation step of separating the biologically treated treated water , air and the microorganisms by a gas-solid separation device provided in an upper part of the reaction tank ;
A water treatment method comprising: And organic matter and means for adjusting the iron ions to the C / N ratio of the raw water containing 0.1 mg-Fe / L or more is 7 or less,
A reaction tank for biologically treating the organic matter by bringing the raw water whose C / N ratio is adjusted to 7 or less into contact with microorganisms;
Raw water introduction means for continuously introducing the raw water from the lower part of the reaction tank;
Oxygen supply means for supplying oxygen to the reaction vessel;
A separation means for separating the biologically treated treated water , the oxygen and the microorganisms, which is provided in an upper part of the reaction tank ;
With
In the reaction tank, a granule obtained by granulating the microorganism is formed under aerobic conditions in the presence of nitrifying bacteria.