KR100510406B1 - The apparatus and the method of wastewater purification by anoxic-aerobic fluidizied bed - Google Patents

Abstract

The present invention is difficult to maintain a constant concentration of microorganisms in the reactor because the conventional wastewater treatment apparatus using activated sludge method is difficult to maintain a constant concentration of microorganisms in the reaction tank, the hydraulic retention time for wastewater treatment, due to the low concentration of microorganisms It is weak to load fluctuations and there is a problem that sludge of sludge occurs at high load, which significantly reduces the processing capacity.

Even in the wastewater treatment system using a fluidized bed, there is a problem of adding an alkali agent to the nitrification process and adding a carbon compound such as methanol to the denitrification process in order to activate the microorganism activity.

Deoxygenation of the raw wastewater introduced into the lower part by using anaerobic bacteria attached to the media flowing inside, and the anoxic tank discharged through the upper part, and the primary treatment water discharged from the anoxic tank for a predetermined time to precipitate the sludge A primary circulating means introduced through the lower portion by using a settling tank, a primary circulation means for drawing part of the primary treated water from the lower portion of the settling tank and re-feeding it to the lower portion of the anoxic tank, and aerobic bacteria attached to the media flowing inside The aerobic tank which removes the organic matter contained in the treated water and discharges through the upper part, the aeration tank which supplies oxygen while temporarily storing the secondary treated water exiting the aerobic tank and discharges the final treated water, and the upper part of the settling tank A flow pump for supplying the first treated water flowing through the lower portion of the aerobic tank, and from the lower portion of the aeration tank; Secondary circulation means for withdrawing part of the treated water to be re-introduced into the lower portion of the aerobic tank, a conveying pump for re-introducing a portion of the secondary treated water exiting the aerobic tank to the lower portion of the anaerobic tank, and the anaerobic and aerobic tanks It is installed in the upper part of the tank and is composed of biomembrane separation means for detaching microorganisms from the media to keep the size of bioparticles constant.

As the anaerobic and anaerobic bacteria flow, the waste water denitrification, organic matter removal and high microbial concentration in the reactor can be maintained, thereby improving the efficiency of wastewater treatment. will be.

Description

The apparatus and method for wastewater treatment using anoxic-aerobic fluidized bed {The apparatus and the method of wastewater purification by anoxic-aerobic fluidizied bed}

The present invention relates to a wastewater treatment apparatus for purifying wastewater, and in particular, an anaerobic-aerobic flow that can improve the efficiency of wastewater treatment by activating denitrification and organic matter removal reactions while flowing anaerobic and aerobic bacteria in respective reactors. A wastewater treatment apparatus and method using a phase.

Wastewater flowing into the river contains nutrients such as nitrogen (N ₂ ) and phosphorus (P) along with carbonaceous organic substances represented by biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Among these, nitrogen promotes eutrophication, so that not only the toxicity of ammonia nitrogen (NH ₃ -N) to aquatic organisms, but also ammonia nitrogen is nitrite nitrogen (NO ₂ ^-- N) and nitrogen nitrate (NO ₃ ^-- N). As a large amount of oxygen is consumed by nitrification which is oxidized, it is not only the cause of the death of fish and fish, but also the creator of the dead river. Nitric acid is not only a causative agent of eutrophication, but also binds to hemoglobin in the blood vessels to form methemoglobin, causing infants to develop methemoglobinemia, which is an oxygen deficiency. Nitrogen is known to form nitrosamine, a carcinogen. Today, biological methods for denitrifying and removing nitrogen and nitrite nitrogen in the form of nitrogen are used.

On the other hand, activated sludge is generally widely recognized as a biological treatment method and is applied to many wastewater treatment facilities. However, as the water quality environment has worsened recently, more advanced treatment methods are required, and existing activated sludge methods are difficult to cope with this, and thus there are cases where users cannot satisfy the water quality required by users. In particular, the deterioration of water supplies due to eutrophication of closed waters has reached a serious level. Therefore, in addition to the existing activated sludge method, biological denitrification and dephosphorization processes are introduced to remove nitrogen and phosphorus as the causes of eutrophication, and research on this is being actively conducted.

In general, if the wastewater treatment process is classified according to the growth patterns of microorganisms, it can be divided into floating growth and adherent growth. Floating growth is a method of treating wastewater while the microorganisms involved in wastewater purification naturally propagate inside the reactor, which is mainly used for activated sludge method, and more than 90% of Korean wastewater treatment plants use activated sludge method. In contrast, adherent growth is a method in which wastewater is treated using biofilms formed by microorganisms involved in wastewater purification on fixed or fluidized media. In the United States, biofilm processes account for more than 30% of wastewater treatment plants. Very high.

Activated sludge method is difficult to maintain constant concentration of microorganisms in the reaction tank unless sludge is returned due to the loss of microorganisms, hydraulic retention time for wastewater treatment is relatively long, and it is weak to load fluctuation due to low concentration of microorganisms and Swelling has a disadvantage that the processing capacity is significantly reduced. In addition, the required site and facility capacity must be large, and there is a lot of difficulty in treating a large amount of wastewater which is increased day by day because it is sensitive to temperature changes.

In order to solve these drawbacks, it is necessary to maintain a high concentration of microorganisms in a relatively small space in the reaction tank, which requires the treatment of the wastewater, the immersion filtering method, the rotating disk method and the fluidized bed method. In particular, in the case of fluidized bed, the specific surface area provided for adhesion growth and microbial retention per unit volume are much higher than other processes, and many studies are being conducted at home and abroad.

The research on the fluidized bed is mainly progressing domestically and internationally on the basis of less than 1mm of silica sand or lightweight aggregate as part of the high efficiency of the processing equipment. The characteristic of the fluidized bed is a treatment method to purify by biofilm formed on the media instead of the floc by activated sludge method.As the microorganisms responsible for purification grow and adhere to the media in the fluidized bed, solid-liquid separation by sludge tank and sludge conveyance are performed. It is unnecessary and has the characteristics that useful microorganisms, such as ammonia oxidizing bacteria and nitrite oxidizing bacteria, which have a slow specific growth rate are easily attached. In addition, unlike activated sludge method, there is no swelling phenomenon, so the operation management is easy and the amount of excess sludge is generated, which is applicable to low concentration organic wastewater. However, if the adherent biofilm becomes too thick, the processing capacity is lowered. Therefore, it is necessary to understand the variation of biofilm volume, to study the growth and peeling mechanism, and to establish a method of automatically removing and managing the biofilm.

Wastewater containing nitrogen and phosphorus and advanced treatment are required. Especially, in the treatment of nitrogen components, biological treatment is economical and efficient. To remove nitrogen biologically, it is possible by inducing a nitrification process under aerobic conditions and by applying a denitrification process under anoxic conditions.

In general, however, in the biological removal of waste water, there is a problem in that an alkali agent is added to the nitrification process and a carbon compound such as methanol is added to the denitrification process.

The present invention has been made to solve the above problems of the prior art, by performing a denitrification reaction using anaerobic bacteria first and then performing a nitrification process to aerobic bacteria, high concentration of microorganisms without adding an additional additive It is an object of the present invention to provide an apparatus and method for treating wastewater using an anoxic-aerobic fluidized bed which can improve the efficiency of wastewater treatment using.

The present invention for achieving the above object is an anaerobic tank for denitrifying the raw wastewater flowing into the lower part by using the anaerobic bacteria attached to the media flowing inside, and discharged through the upper portion, and the first treatment exited from the anoxic tank A sedimentation tank for storing water for a predetermined time to settle the sludge, a primary circulation means for drawing part of the primary treated water from the lower part of the sedimentation tank and re-injecting it into the lower part of the anoxic tank, and aerobic fluid attached to the media flowing inside The aerobic tank discharges through the upper part after oxidizing the primary treated water introduced through the lower part using bacteria, and temporarily stores the secondary treated water exiting the aerobic tank while supplying oxygen and discharging the final treated water. Aeration tank, and the flow pump for supplying the first treatment water flowing through the upper portion of the settling tank to the lower portion of the aerobic tank, A second circulation means for drawing part of the secondary treated water from the lower part of the aeration tank and re-putting it into the lower part of the aerobic tank, and a return pump for re-putting a part of the secondary treated water exiting the aerobic tank to the lower part of the anoxic tank; And, it is installed on the anoxic tank and the aerobic tank is characterized in that consisting of biofilm separation means for separating the biofilm of the bioparticles to maintain a predetermined size.

In addition, the wastewater treatment method using the anoxic-aerobic fluidized bed of the present invention is the first step of denitrifying the raw wastewater supplied to the anaerobic tank in which anaerobic bacteria are propagated and discharging only the supernatant water to the primary treated water, and the primary treatment. Precipitate the organic matter contained in the water and then supply the upper layer water to the aerobic tank, and part of the lower layer water is returned to the anoxic tank and re-introduced together with the original waste water, and the first step using the aerobic bacteria grown in the aerobic tank. Removing the organic matter contained in the treated water and discharging the upper water to the secondary treated water, and supplying oxygen to the secondary treated water to oxidize it, and then discharging the upper water to the final treated water and the lower water to the It is characterized by consisting of a fourth step of returning to the aerobic tank to be re-injected with the first treated water.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The wastewater treatment apparatus using the anoxic-aerobic fluidized bed of the present invention uses an anaerobic bacterium attached to the media flowing inside, as shown in FIG. (20), and the settling tank 30 for storing the primary treated water from the oxygen-free tank 20 for a predetermined time to settle the sludge, and withdraw some of the primary treated water from the lower portion of the settling tank 30 After removing the organic matter contained in the first treated water introduced through the lower by using the first circulation means 35 and the aerobic bacteria attached to the media flowing in the lower portion of the anoxic tank 20, the upper portion is removed. The aeration tank 40 discharged through the aeration tank 50 to temporarily discharge the final treatment water after supplying oxygen while temporarily storing the secondary treatment water exited from the aerobic tank 40, and the settling tank of the A flow pump 53 for supplying the first treated water flowing through the upper portion to the lower portion of the aerobic tank 40 and a portion of the second treated water from the lower portion of the aeration tank 50 to draw out the aerobic tank 40 A second circulation means 55 to be re-injected to the lower portion of the lower portion, a conveying pump 58 to re-introduce a portion of the secondary treated water exiting the aerobic tank 40 to the lower portion of the oxygen-free tank 20, and It is installed on the anoxic tank 20 and the aerobic tank 40 and is composed of a biofilm separation means 60 to maintain the size of the bioparticles (bioparticles) by maintaining the size of the microorganisms from the media.

As shown in FIG. 2, the biofilm separator 60 is installed on the anoxic tank 20 and the aerobic tank 40 to suction the bioparticle 65 and use a centrifugal force. The desorption pump 62 which separates the bio particles 65 into microorganisms and sand grains 66, and the bio particles 65 introduced through the suction unit 61 are supplied to the desorption pump 62. The feed pipe 63 and the sand grain 66 separated from the microorganisms in the desorption pump 62 are composed of a return pipe 64 which is returned to the anoxic tank 20 and the aerobic tank 40.

The anoxic tank 20 and the aerobic tank 40 are formed at the lower end of the conical shape so that the bio particles 65 in the tank are not damaged by the collision, and the first circulation means 35 and the second circulation means 55 ) Is provided with flow rate detectors 36 and 56 to detect the amount of treated water being re-injected. In addition, a fixed quantity injection pump 11 is installed at the inlet of the anoxic tank 20 so that the amount of the raw wastewater supplied to the anoxic tank 20 is always constant.

Reference numerals 21 and 41 are pressure gauges for sensing the pressure of the oxygen-free tank 20 and the aerobic tank 40, and 22 and 42 are formed on the side surface so as to obtain a sample liquid from the oxygen-free tank 20 and the aerobic tank 40. One sampling port.

The wastewater treatment apparatus using the anoxic-aerobic fluidized bed of the present invention configured as described above is subjected to denitrification first and then nitrified to remove nitrate nitrogen.

When the raw waste water stored in the feed tank 10 is supplied to the lower portion of the anaerobic tank 20 through the quantitative injection pump 11, the denitrification reaction proceeds in the anaerobic tank 10. That is, the anaerobic bacteria attached to the median of the anoxic tank 20, nitrate and nitrite nitrogen (NO ₂ ^- -N) and ^{nitrate-nitrite} ions constituting the _{(NO 3 -N) (NO 2} -) and nitrate ions By breathing (NO ₃ ⁻ ) as a hydrogen acceptor, it is converted into nitrogen gas (N ₂ ) and released into the atmosphere. In other words, in the oxygen-free tank 20, the reduction reaction of nitrite ion and nitrate ion by the anaerobic bacteria is made, and the organic material is required as an energy source for the reduction reaction, and the organic material is also removed at the same time.

Primary wastewater formed by denitrification by the anaerobic bacteria is moved to the settling tank 30 through an outlet formed at the top of the anaerobic tank 20. In the settling tank 30, the sludge contained in the primary treatment water is settled, and the sludge is precipitated and the remaining supernatant is supplied to the lower portion of the aerobic tank 40 according to the operation of the flow pump (). At this time, the precipitated sludge is re-introduced to the lower portion of the anoxic tank 20 by the first circulation means 35 connected to the lower portion of the sedimentation tank 30 together with the lower layer water, and the circulation ratio of the primary treated water is about 30%. It is enough. As a result, since the oxygen-free tank 20 does not require oxygen in the process of denitrification, the primary treated water is circulated only to the extent that only the media can flow well.

The primary treatment water supplied to the aerobic tank 40 is organic matter is removed by the aerobic bacteria attached to the media of the aerobic tank (40). That is, aerobic bacteria oxidize ammonia nitrogen (NH ₃ -N) formed as a result of denitrification, and as a result, nitrite nitrogen (NO ₂ ⁻ ) and nitrite nitrogen (NO ₃ ⁻ ) containing nitrite ion ( NO ₂ ^-- N) and nitrate nitrogen (NO ₃ ^-- N) are formed. At the same time, assimilation occurs for the propagation of aerobic bacteria, the amount of organic matter required for assimilation is reduced.

Wastewater after the secondary treatment by aerobic bacteria is completed is the secondary treatment water is moved to the aeration tank 50, a part of the secondary treatment water by the conveying pump (58) while moving to the aeration tank (50) 20 Return to) and re-input. That is, the nitrate nitrogen and the nitrite nitrogen contained in the secondary treated water are moved to the anoxic tank 20 so that the denitrification reaction proceeds. At this time, the circulation ratio of the secondary treated water is suitable about 40%, because the oxygen demand is increased with the increase of the circulation ratio because the aerobic microorganisms remove most of the organic matter.

The aeration tank 50 is supplied with sufficient oxygen while allowing the sludge contained in the secondary treated water to settle. At this time, the aeration tank 50 is provided with an air pump 53 to increase the supply of oxygen, sludge precipitated at the bottom of the aeration tank 50 by the second circulation means 55 together with the lower layer of aerobic tank 40 ) And the supernatant after sludge settling is discharged and discharged.

Here, as the media, sand grains are used, and anaerobic bacteria or aerobic bacteria are attached to the media to form a biofilm, and the media on which the biofilm is formed are called bioparticles. The size of the bio particles 65 is gradually increased as the reactor 20, 40 is operated, which is due to the growth and proliferation of microorganisms. Therefore, as the size of the bioparticle 65 increases, the height of the fluidized bed becomes high. At this time, the bioparticle 65 is lost unless the height is maintained below a certain height. If the bioparticles 65 are lost, the treatment efficiency of the wastewater is reduced and the operation of the fluidized bed is difficult.

In order to avoid such obstacles, the biofilm separation means 60 installed at the top of the reaction tanks 20 and 40 is operated. The biofilm separation means 60 sucks the bioparticles 65 forming the fluidized bed using the suction part 61, and the sucked bioparticles 65 desorb the pump 62 through the supply pipe 63. Is moved to. The desorption pump 62 separates the microorganisms attached to the media from the median sand grains 66 using centrifugal force, and only the sand grains 66 are refilled into the fluidized bed through the return pipe 64. At this time, the sludge formed by detaching from the bioparticle furnace 65 is discharged together with the treated water through the outlet formed in the upper portion of the reaction vessel 20, 40.

The ammonia nitrogen (NH ₃ -N) formed as a result of the denitrification reaction in the oxygen-free tank 20 is transferred to the aerobic tank 40 and oxidized, and the nitrite nitrogen (NO ₂ ^-- formed by nitrification in the aerobic tank 40). N) and nitrate nitrogen (NO ₃ ^- -N) is conveyed to the anoxic tank (20) by the transfer pump 58 is changed into ammonium nitrogen (NH ₃ -N). At this time, the ratio of the waste water flowing into the anoxic tank 20 and the return water returned from the aerobic tank 40 is about 2 to 3.5 is appropriate, the effect of waste water treatment when the ratio of the raw waste water and the return water is 3. Is the best.

Chemical reactions used in the present invention are represented by Chemical Formulas 1 to 4 below.

[Formula 1]

^{_{22NH 4 + + 37O 2 + 4CO}} 2 + HCO 3 -

_{→ C 5 H 7 O 2 N} + 21 NO 3 - + 20H 2 + 42H +

Formula 1 shows the total metabolism including both nitrification and assimilation in aerobic tank 40, and includes Formula 2 indicating nitrification and Formula 3 indicating cell assimilation.

[Formula 2]

^{_{NH 4 + + 2O 2 → NO}} 3 - + 2H + + H 2 O

Formula 2 indicates that ammonium ions (NH ₄ ⁺ ) contained in ammonia nitrogen (NH ₃ -N) are oxidized to be converted into nitrite ions (NO ₃ ⁻ ) and water as nitrification, and aerobic bacteria nitrite and nitrate Due to catabolism for energy acquisition.

[Formula 3]

^{_{4CO 2 + HCO 3 - + NH}} 4 + + H 2 O → C 5 H 7 O 2 N + 5O 2

Formula 3 indicates the synthesis of cellular material through the supply of carbon as an assimilation process, and is due to an assimilation for cell synthesis of aerobic bacteria.

[Formula 4]

^{_{2NO 2 - + 3H 2 → N}} 2 + 2OH - + 2H 2 O

^{_{2NO 3 - + 5H 2 → N}} 2 + 2OH - + 4H 2 O

Formula 4 shows the denitrification reaction occurring in the anaerobic tank 20 as a chemical formula, and shows a catabolism by anaerobic bacteria that proliferate in the anaerobic tank 20.

That is, the raw waste water is introduced into the anoxic tank 20 together with the return water and denitrified by anaerobic bacteria, and as a result of the denitrification, nitrite ions (NO ₂ ⁻ ) or nitrate ions (NO ₃ ) contained in the waste water and the return water. ^- ) Is reduced to nitrogen (N ₂ ). The denitrified primary treated water is introduced into the aerobic tank 40 and nitrified by aerobic bacteria, and as a result of nitrification, ammonia nitrogen (NH ₃ -N) contained in the secondary treated water is returned to the anoxic tank 20 side. It is re-injected with the original waste water into the anaerobic tank 20. Of course, most of the secondary treated water discharged from the aerobic tank 40 is temporarily stored in the aeration tank 50, mixed with oxygen and then exits into the effluent.

As such, the wastewater treatment apparatus and method using the anaerobic-aerobic fluidized bed of the present invention can denitrify wastewater and remove organics while flowing anaerobic bacteria and anaerobic bacteria, and maintain high microbial concentration in the reaction tank. There is an advantage to improve the efficiency.

1 is a block diagram showing an apparatus for treating wastewater using an anoxic-aerobic fluidized bed according to the present invention.

Figure 2 is a detailed view of the biofilm separation device that is the main component of the present invention.

3 is a flow chart illustrating a wastewater treatment method using an anoxic-aerobic fluidized bed according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: feed tank 11: metering pump

20: anoxic tank 30: sedimentation tank

35: first circulation means 36: flow rate detector

40: aerobic maturity 50: abandonment

53 air pump 55 second circulation means

56: flow rate sensor 58: conveying pump

60: biofilm separation means 61: suction unit

62: tally pump 63: supply pipe

64: return pipe 65: bio particles

66: grains of sand

Claims (9)

Deoxygenation of the raw wastewater introduced into the lower part by using anaerobic bacteria attached to the media flowing inside, and the anoxic tank discharged through the upper part, and the primary treatment water discharged from the anoxic tank for a predetermined time to precipitate the sludge A primary circulating means introduced through the lower portion by using a settling tank, a primary circulation means for drawing a part of the primary treated water from the lower portion of the settling tank and re-feeding it to the lower portion of the anoxic tank, and an aerobic bacterium attached to a medium flowing therein; The aerobic tank which removes the organic matter contained in the treated water and discharges through the upper part, the aeration tank which supplies oxygen while temporarily storing the secondary treated water exiting the aerobic tank and discharges the final treated water, and the upper part of the settling tank A flow pump for supplying the first treated water flowing through the lower portion of the aerobic tank, and from the lower portion of the aeration tank; Secondary circulation means for withdrawing part of the treated water to be re-introduced into the lower portion of the aerobic tank, a conveying pump for re-introducing a portion of the secondary treated water exiting the aerobic tank to the lower portion of the anaerobic tank, and the anaerobic and aerobic tanks Apparatus for wastewater treatment using an anoxic-aerobic fluidized bed characterized in that it is installed on the top of the tank and composed of biofilm separation means for detaching microorganisms from the media to maintain a constant size of the bioparticles. The method of claim 1, The biomembrane separation means is provided on the upper part of the anoxic tank and aerobic tank suction section for suctioning the bioparticles, a desorption pump for separating the bioparticles into microorganisms and sand grains using centrifugal force, and the bioparticles introduced through the suction unit The waste water treatment apparatus using an oxygen-exhaled aerobic fluidized bed characterized by consisting of a supply pipe supplied to the desorption pump and a return pipe in which sand grains separated from bacteria in the desorption pump are returned to the anoxic tank and the aerobic tank. The method of claim 1, The anoxic tank and the aerobic tank are wastewater treatment apparatus using an oxygen-aerobic fluidized bed, characterized in that the lower end is formed in a conical shape so that bioparticles in the tank are not damaged by collision. The method of claim 1, An apparatus for treating waste water using an anoxic-aerobic fluidized bed, characterized in that a fixed quantity injection pump is provided such that the amount of raw wastewater supplied to the anoxic tank is always constant. The method of claim 1, The first circulation means and the second circulation means is an oxygen-free aerobic fluidized bed characterized in that consisting of a circulation pump for taking out the treated water to be re-introduced into each reactor, and a flow rate sensor for detecting the amount of the re-introduced treated water. Wastewater treatment device using. The first step of denitrifying the raw wastewater supplied to an anaerobic tank in which anaerobic bacteria are propagated and discharging only the supernatant water to the primary treated water, and after precipitating the denitrified precipitate contained in the primary treated water, the supernatant is aerobic. The second step of feeding into the tank and part of the lower layer water is returned to the anoxic tank and re-injected with the original waste water, and the upper layer water removing the organic matter contained in the primary treated water using the aerobic bacteria grown in the aerobic tank. The third step of discharging to the secondary treatment water, and after supplying oxygen to the secondary treatment water to oxidize, the upper layer water is discharged to the final treated water and the lower layer is returned to the aerobic tank to be re-introduced with the primary treated water Wastewater treatment method using an anoxic-aerobic fluidized bed characterized in that the fourth step. The method of claim 6, And a conveying step of conveying the nitric oxide formed in the third step to the anoxic tank to denitrify with the raw waste water. The method according to claim 6 and 7, Waste water treatment method using an oxygen-aerobic fluid bed characterized in that the ratio of the raw waste water to the anoxic tank and the return water is 2 to 3.5. The method of claim 6, The circulation ratio of the primary treated water is 25 to 35%, and the circulation ratio of the secondary treated water is 35 to 40%.