KR200425128Y1 - Biological phosphorus and nitrogen removal apparatus using the granulated methan-oxidizing bacteria - Google Patents

Abstract

The present invention relates to a method and apparatus for biologically removing nitrogen and phosphorus, using methane oxide bacteria grown using methane as a carbon source such as methane gas contained in anaerobic digestion gas of sewage treatment plant or methane gas generated from landfill site. A method and apparatus for biologically removing nitrogen and phosphorus simultaneously. In the present invention, the methanolated bacteria were granulated to dominantly increase the removal efficiency of nitrogen and phosphorus. In addition, methane gas and oxygen in the granulation bioreactor were dissolved in the return water, circulated, and when the gas was exhausted and decompressed, the intermittent gas injection method was used to reduce the methane content in the exhaust gas. . In addition, organic carbon, such as methanol generated in the granulation bioreactor, was further utilized as a carbon source for an anoxic activated sludge process, thereby further improving nitrogen removal.

Methanolated Bacteria, Granulation, Nitrogen, Phosphorus

Description

Biological phosphorus and nitrogen removal apparatus using the granulated methan-oxidizing bacteria}

1 shows a treatment apparatus of the present invention for biologically treating phosphorus and nitrogen using granulated methanated bacteria.

Figure 2 shows a granulation bioreactor section in which hollow fiber synthetic membrane biocarriers are installed.

* Explanation of symbols for the main parts of the drawings

101: oxygen storage tank 102: methane storage tank

103, 104: supply valve 105: mixing tank

201: bioreactor gas holder 202: granulation bioreactor

203: influent pump 204: influent

205: Return water 206: Return water pump

207: conveying water injection nozzle 208: granulation tank agitator

209: granular treatment water 210: mixed gas valve

301: anoxic tank agitator 302: anoxic tank

303: final processed water

401: hollow fiber synthetic membrane biocarrier

402: hollow fiber biological carrier treated water

The present invention relates to a method for biologically removing nitrogen and phosphorus and a device therefor, and more particularly, to methane such as methane gas contained in anaerobic digestion gas of sewage treatment plant or methane gas generated from landfill site as carbon source. The present invention relates to a method for granulating methanated bacteria and removing nitrogen and phosphorus simultaneously, and a device therefor.

In general, biological and nitrogen removal apparatus by suspended microorganisms are anaerobic tank which is a process of releasing phosphorus in the cell; An oxygen-free tank for reducing nitrate or nitrite nitrogen by nitrogen gas; An aeration tank that serves to remove organic matter, oxidize nitrogen, and excessively intake of phosphorus released from the anaerobic tank; And a sedimentation tank for sedimenting the floating microorganisms to separate the treated water and the microorganisms. In order to remove phosphorus by such a device, the anaerobic sludge should be introduced into the aeration tank after undergoing an anaerobic tank, and the aeration tank sludge should be returned to the anaerobic tank to repeat the anaerobic and aeration processes. In addition, in order to remove nitrogen, it was troublesome to repeat the anoxic process and the aeration process again for the sludge.

In addition, in order to facilitate the release and denitrification of phosphorus in the anaerobic and anaerobic tanks for removing phosphorus and nitrate nitrogen, the influent of BOD (biological oxygen demand) or COD (chemical oxygen demand) Etc., the concentration of organic matter should be high. If the concentration of organic matter in the influent is low or insufficient, additional denitrification reactors should be installed after the aeration process, and methanol or acetic acid should be injected as an organic carbon source supplement. The furnace must be completely decomposed by the post-aeration process. Therefore, there is a need for a new carbon source to replace methanol or acetic acid because there is a problem that additional facility costs such as after-denitrification tank and post-aeration tank, and expensive methanol or acetic acid chemical cost are additionally required when the influent carbon source is insufficient.

On the other hand, methane gas is generated from an organic waste landfill or an anaerobic sludge digester in a sewage treatment plant, and is treated as a gas causing global warming and is usually burned in the atmosphere. Therefore, methane gas is a very inexpensive alternative carbon source for nitrogen removal.

In order to use methane as a carbon source, the aeration tank, which is an aerobic reaction tank, is incubated with air and methanated bacteria are inhabited, and the methanated bacteria proceed through the following steps.

1) In the first step, methane injected by metanotrophs bacteria is converted into organic materials such as methanol using dissolved oxygen in water,

2) In the second step, the generated methanol is used as a carbon source to reduce nitrate nitrogen in water to nitrogen gas by methylotrophs bacteria.

In the conventional method for improving nitrogen removal rate using characteristics of methanated bacteria growing in the aerobic environment as described above, that is, activated sludge method using suspended microorganisms, directly inflowing wastewater, air and methane gas into an aeration tank, and attaching microorganisms. In the bio-media using the inlet waste water, air, methane gas is injected directly at the same time from the bottom of the reactor. Therefore, in the conventional nitrogen and phosphorus removal method using methanation bacteria, methanation bacteria dominate and methanation bacteria dominate, while organic matter removal bacteria such as BOD and COD, and nitrification bacteria oxidizing ammonia nitrogen are mixed. It was difficult.

In addition, since the organic oxidizing bacteria grow faster than the methane oxidizing bacteria, methanol produced by the methane oxidizing bacteria was consumed by the organic oxidizing bacteria first, and thus the nitrogen removal efficiency by the methylotropes was very low. In addition, methane-oxidized bacteria produced during the injection of methane gas release sticky gelatinous substances, such as polysaccharides (EPS), 10 times more than ordinary floating or adherent bacteria, and thus, gravel, ceramics, etc. When the same biocarrier was used, the pores between carriers were frequently closed. In addition, methane gas is a global warming gas, and if it is 5% or more in the atmosphere, there is a possibility of explosion. Therefore, when the conventional method is used as it is, there is a problem that the concentration of the methane gas is high and the explosion gas is high even after the bioreaction.

Therefore, in order to effectively use methane gas as a carbon source for nitrogen removal, 1) the methanolated bacteria should be dominated by species, 2) when applied to biological carriers, and no closure should occur. The concentration of methane must be very low.

The technical problem to be achieved by the present invention is to provide a method and apparatus for more effectively removing the nitrate nitrogen or phosphorus present in the contaminated water.

As a result of intensive research to remove phosphorus and nitrogen in contaminated water, the inventor has granulated methanated bacteria by utilizing the fact that methane-oxidized bacteria contain a large amount of polysaccharides as sticky substances. The method and apparatus for dominating only methanated bacteria were developed, and the present invention was completed by confirming that phosphorus and nitrogen in contaminated water can be more effectively removed.

In order to achieve the above technical problem, the present invention, a first step of injecting a methane gas and oxygen mixed in the bioreactor gas holder; Injecting water and granulated water into the bioreactor gas holder is injected, and the methane gas and oxygen are dissolved in the inflow water and the return water, and then the inflow water and the dissolved water of the methane gas and oxygen are granulated. A second step of transporting the bioreactor; A third step of reducing the nitrate nitrogen in the inflow and return water with nitrogen gas by using the granulated methanation bacteria in the granulation bioreactor; And a fourth step of transporting the treated water from which nitric acid is removed to an anoxic tank and then discharging the same.

In addition, the present invention, a mixing tank for mixing methane gas and oxygen; A granulation bioreactor equipped with a return water pump and an agitator for colliding the methanated bacterial particles with each other to induce granulation; The granulation bioreactor, which is connected to the mixing tank and the granulation bioreactor, and the return water from the inflow water and the granulation bioreactor, is injected, and the mixed gas of methane gas and oxygen mixed in the mixing tank is cultured. A bioreactor gas holder for efficiently feeding a furnace; And an anoxic tank connected to the granulation bioreactor, wherein the treated water in the granulation bioreactor is further transported to further treat nitrate nitrogen with organic matter such as methanol remaining. To provide.

Hereinafter, the present invention will be described in detail.

The biological phosphorus and nitrogen removal method using the methanated bacteria according to the present invention includes a first step of first mixing the methane gas and oxygen and then injecting the bioreactor gas holder.

In the above, the mixing ratio of methane gas and oxygen is 1: 0.5 (volume ratio) when compressed air is used for proper cultivation of methane-oxidized bacteria, and 1: 0.5 (volume ratio) when pure oxygen (gas oxygen, oxygen 60% or more) is used. Is preferably, but is not limited thereto.

Thereafter, a second step of injecting inflow water into the bioreactor gas holder to dissolve the methane gas and oxygen in the inflow water and then transporting the inflow water in which the methane gas and oxygen are dissolved to a granulation bioreactor.

In the inflow water, rather than directly using high-contaminant wastewater containing a mixture of organic and nitrogen substances, first of all, the decomposition of organic matter and oxidation of nitrogen compounds in the aeration tank of activated sludge, which is a commonly used biological treatment facility, is performed. By the way, it is preferable to use the treated water which removes organic substance and has high nitrate nitrogen content.

Methane gas, a carbon source, is supplied in the granulation bioreactor transported with inflow water in which methane gas and oxygen are dissolved. In particular, in the present invention, since the methane gas provided as the carbon source is consumed to the maximum by the methane-oxidizing bacteria, there is an advantage that the residual concentration of methane is very low in the exhaust gas finally discharged.

The method according to the present invention includes a third step of reducing the nitrate nitrogen in the influent to nitrogen gas using methanation bacteria granulated in the granulation bioreactor.

Methane-oxidizing bacteria produce methanol by metanotroph when injecting methane under aerobic conditions with air supply, and methylrotroph is produced by using the produced methanol as a carbon source. It has the ability to remove acidic nitrogen by reducing it to nitrogen gas.

In the present invention, as a method for maximizing and dominantly removing the nitrogen of the methanated bacteria as described above, the methanated bacteria contained a large amount of polysaccharides, which are adhesive substances, and used a high concentration of microorganisms without a carrier. This is characterized by the fact that it is possible to produce concentrated granulated methanated bacteria.

The granulation of methane-oxidized bacteria is based on the vortex caused by the hydraulic power of the return water pump that transfers the return water from the granulation bioreactor to the bioreactor gas holder, and assists the stirring force of the agitator in the granulation bioreactor. By conventional means, it is by repetitive contact between methanated bacterial particles. In the above, the stirring force of the stirrer is preferably a stirring speed in the range of 10-20 rpm, which causes a problem that the granulated sludge subsides when the stirring speed is less than 10 rpm, and when the stirring speed exceeds 20 rpm, This is because a problem of excessive expansion of the sludge layer occurs.

As described above, after the nitrate nitrogen is reduced to nitrogen gas by the methanation bacterrea in the granulation bioreactor, the inflow water in the granulation bioreactor is returned to the bioreactor gas holder. Methane gas and oxygen are dissolved again in the returned water returned to the bioreactor gas holder, and methane gas and oxygen are consumed.

In addition, after the third step, the nitrate nitrogen in the influent and the return water may be further reduced by nitrogen gas using methanation bacteria attached to the surface of the hollow fiber synthetic membrane carrier. There is an advantage that the treatment can be carried out continuously without closing the microbial carrier.

The hollow fiber synthetic membrane that can additionally be used to remove the nitrogen and phosphorus is preferably a synthetic high molecular material such as polyethylene (polyethylene) or poly propylene (poly propylene). In addition, the hollow fiber synthetic membrane is hollow, and a conventional microfiltration membrane having a diameter of 0.5 to 1 mm is preferable. When the diameter of the hollow fiber synthetic membrane is in the above range, there is an advantage that the diameter is thin and the microbial adhesion specific surface area becomes very large. In addition, it is preferable that the hollow body is in the form of a strand of a strand. In such a case, when the influent flows into the upstream, even when the thread of each membrane is separated by the flow rate and buoyancy, the methane oxide bacteria adhere to the surface. There is no problem of clogging.

After the nitrate nitrogen is discharged to nitrogen through the above steps, the treated water from which the nitrate nitrogen has been removed is transported to an anaerobic tank, retreated, and discharged.

Hereinafter, a method for removing biological nitrogen and phosphorus and an apparatus therefor according to the present invention will be described in detail with reference to the drawings showing an embodiment according to the present invention.

 The mixed tank 105 may be compressed air and compressed methane gas 102 by the compressed pure oxygen 101 or the compressor at a mixing ratio of 0.5: 1 or 1: 1 (volume ratio) by opening the supply valves 103 and 104. After mixing in, it is injected into the bioreactor gas holder 201.

The upper part of the bioreactor gas holder is sealed to prevent external air from penetrating, and when the mixed gas is injected, the water level in the bioreactor gas holder 201 is lowered by the injection pressure, and the level of the granulation bioreactor 202 is increased. do. When the inflow water 204 rich in nitrate nitrogen and the return water 205 returned from the granulation bioreactor are pumped into the bioreactor gas holder 201 with the pumps 203 and 206, the methane of the bioreactor gas holder 201 is injected. Gas and oxygen are dissolved in the influent 204 and the return water 205 and transported to the granulation bioreactor 202. The return water 205 transported from the granulation bioreactor 202 to the bioreactor gas holder 201 is sprayed with a spray nozzle 207 to evenly dissolve methane gas and oxygen.

The methane gas and oxygen delivered to the granulation bioreactor 202 are converted to methanol and carbon dioxide by metanotropes bacteria using dissolved oxygen, and the methylotropes are nitrates contained in influent 204 using methanol. Nitrogen is removed by nitrogen gas. Accordingly, the upper part of the granulation bioreactor 202 discharges nitrogen and carbon dioxide decomposed by methanation bacteria, and the methane gas and oxygen in the bioreactor gas holder 201 are transported and consumed by the return water 205. As the partial pressure of oxygen and methane gas is gradually lowered, the level of the bioreactor gas holder 201 is gradually increased.

When the water level of the bioreactor gas holder reaches the highest point, the valve 210 of the gas mixing tank 105 is opened again to provide methane gas and oxygen to the lowest level point. By intermittently injecting the gas and using it until the exhaustion of the methane gas and oxygen can be prevented, methane is prevented from being lost in the exhaust gas of the granulation bioreactor 202.

Granulation of methanated bacteria in the granulation bioreactor 202 is based on the vortex caused by the hydraulic power of the return water pump 206 which transfers the return water from the granulation bioreactor to the bioreactor gas holder 201. Using the stirring force of the mechanical stirrer 208 as an auxiliary means, granular methanated bacteria are produced by repetitive contact between methanated bacterial microbial particles having a very high concentration of gelatinous substances such as polysaccharides.

When the method of granulating methane-oxidized bacteria further includes a method of using the hollow fiber synthetic membrane 401 as a microbial attachment carrier, methane and oxygen mixed gas injection 210, influent injection 204, and return All procedures, such as water injection (205), are the same as the granulation method of methanated bacteria. However, the hollow fiber synthetic membrane 401 is used as a carrier to which the methanated bacterium, which contains a lot of gelatinous materials such as polysaccharides, can be attached without a closing phenomenon. Since the hollow fiber synthetic membrane is usually made of 0.5 to 1mm in diameter and hollow and very light, the hollow fiber synthetic membrane stands straight in the direction of water flow when the conveying water 205 is conveyed in an upflow manner, so that there is no overlap between the membranes. In addition, the supplied methane gas and dissolved oxygen are evenly supplied in the water flow direction so that the methanated bacteria are evenly attached to the hollow fiber synthetic membrane surface.

The treated water (209, 402) passing through the granulated methanation bacteria contains undigested methanol, etc., which is discharged after treatment in an anoxic tank (302) equipped with a stirrer (301) to be reused as a carbon source. 303).

Hereinafter, the present invention will be described in detail by examples.

However, the following examples are merely to illustrate the subject innovation, the contents of the subject innovation is not limited to the following examples.

<Example 1>

Using the apparatus of the present invention equipped with a granulation bioreactor in which methanated bacteria are granulated (see FIG. 1), when methane is injected into each reactor as a carbon source, the removal efficiency of nitrate nitrogen and phosphorus and the global warming gas The exhaust gas content of methane was measured.

Influent water is aerated in the sewage treatment plant, organic matter is removed, ammonia nitrogen is oxidized, and in addition to treated water with high nitrate nitrogen concentration, KNO ₃ as nitrate nitrogen and KH ₂ PO ₄ as soluble phosphorus Was used by injection.

  The inflow flow rate is 100 L / d per day, the hydraulic retention time of the granulation bioreactor 202 is 3 hours, and the oxygen-free tank for using methanol remaining in the granulation bioreactor as a carbon source by the airborne microorganisms (302). ) The residence time was 2 hours. The supply method of methane gas (99%) and oxygen (99%) injected into each reactor was using compressed gas, and the mixture of each gas was mixed at a volume ratio of 1: 1 so that the content ratio (%) of mixed gas was 50:50 was maintained.

By using the pressure of the mixing tank 105, the mixed gas is filled to the lowest point of the bioreactor gas holder 201, and the methane gas and oxygen are consumed by being transferred to the granular bioreactor 202 by the return water 205. When the water level of the bioreactor gas holder 201 reached the highest point, the mixed gas was injected again, and the mixed gas was intermittently injected. In the experiment, each reactor was installed in parallel and the same influent was used.

The results for this example are shown in Table 1 below, and the results in Table 1 are the average values of the experimental results for about one month.

<Example 2>

After the experiment was carried out in the same manner as in Example 1 using a device of the present invention that additionally includes a bioreactor (see FIG. 2) equipped with a polypropylene hollow fiber synthetic membrane having an outer diameter of about 1 mm, It is shown in Table 1 below.

Comparative Example

The efficiency of nitrogen and phosphorus removal and the exhaust gas content of methane, a global warming gas, were measured using a conventional activated sludge process.

In the conventional activated sludge aeration tank operated by injecting air, methane gas was injected at 300 mL / min as a carbon source for oxygen and nitrogen removal, and a mechanical stirrer was used for complete mixing of the activated sludge and gas. The hydraulic residence time of the aeration tank was 6 hours, and the water quality of the influent was the same as that of the example.

division Item COD (mg / L) BOD (mg / L) NO ₃ ^-- N (mg / L) S-P (mg / L) Methane (%)  Comparative example Influent 8 5 40 10 50 Final treated water 5 3 32 8 - Treatment efficiency (%) - - 20 25 - Exhaust air - - - - 35    Example 1 Influent 8 5 40 10 50 Granular Bioreactor Treatment Water 35 22 12 2 - Final treated water 5 2 3 One - Treatment efficiency (%) - - 93 90 - Exhaust air - - - - Not detected    Example 2 Influent 8 5 40 10 50 Granulated bioreactor treated water including membrane carrier 25 18 10 1.8 - Final treated water 3 2 2 1.0 - Treatment efficiency (%) - - 95 90 - Exhaust air - - - - Not detected

As shown in Table 1, in the comparative example using a conventional activated sludge method, the removal efficiency of nitrate nitrogen and phosphorus was very low at 20% and 25%, respectively, and the amount of unreacted methane gas in the exhaust gas was about 35%. As a high percentage, there was a risk of fire. This is because when the methane gas is injected into the activated sludge process, it is difficult to dominate the methane-oxidized bacteria due to competition between aerobic activated sludge bacteria and methane-oxidized bacteria.

On the other hand, in Examples 1 and 2 according to the present invention, the removal efficiency of nitrate nitrogen and phosphorus was more than 90%, which was very high compared to the comparative example. In addition, there was no unreacted methane gas in the exhaust gas. This predominates only methanated bacteria in the form of granular or adherent microorganisms, and the injection of methane dissolves methane gas and oxygen in the return water until the methane of the bioreactor gas holder is exhausted. This is probably because of the intermittent injection operation. In addition, the methanol produced in the granulation bioreactor and the hollow fiber synthetic membrane reactor was further utilized as a carbon source in the anoxic activated sludge process to further improve nitrogen removal. In addition, the present invention is considered to be very excellent due to the adsorption by polysaccharide as compared with the case where methane is introduced into the activated sludge process in phosphorus removal efficiency.

Above As described above, the present invention was able to increase the removal efficiency of nitrogen and phosphorus by granulating methanated bacteria and dominant species, and the delivery of methane and oxygen compressed gas to the bioreactor was dissolved in the return water, circulated and exhausted. After depressurization, the methane content in the off-gas could be drastically reduced by using the intermittent gas injection method again. In addition, methanol produced in the granulation bioreactor was further utilized as a carbon source for an anoxic activated sludge process to further improve nitrogen removal.

Claims (4)

A mixing tank for mixing methane gas and oxygen; A granulation bioreactor equipped with a return water pump and an agitator for colliding the methanated bacterial particles with each other to induce granulation; The granulation bioreactor, which is connected to the mixing tank and the granulation bioreactor, and the return water from the inflow water and the granulation bioreactor, is injected, and the mixed gas of methane gas and oxygen mixed in the mixing tank is cultured. A bioreactor gas holder for efficiently feeding a furnace; And The anoxic tank is connected to the granulation bioreactor and the treated water in the granulation bioreactor is transported to further treat the nitrate nitrogen using organic substances such as methanol. Device for the removal of phosphorus and nitrogen consisting of. The method of claim 1, The bioreactor gas holder is equipped with a nozzle such that methane gas and oxygen are uniformly introduced into the dissolved water to be returned from the granulation bioreactor. Device. The method of claim 1, The hollow fiber synthetic membrane biocarrier is characterized in that it further comprises a granulation bioreactor installed Device. The method of claim 1, The inflow water flowing into the bioreactor gas holder, the organic matter is decomposed through the aeration process, the ammonia nitrogen is oxidized, characterized in that the treated water having a high nitrate nitrogen content Device.

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