KR20040070407A - A waste water disposal plant - Google Patents

Abstract

PURPOSE: Provided is a system for removing organic as well as nutrition such as nitrogen and phosphorus from wastewater, which is characterized in that denitrification reaction in a first intermittent aeration basin is performed by using organic contained in supernatant returned from a sedimentation basin to reduce nitrate and nitride concentration. CONSTITUTION: The system comprises an anaerobic basin (1) where phosphorus is released from microbes; a sedimentation basin (2) where sediment and supernatant are separated; a first intermittent aeration basin (3) where nitrification and denitrification are alternately carried out; a second nitrification basin (2) and a third nitrification basin (8) for the complete nitrification reaction of wastewater; a denitrification basin (9) where nitrate and nitride from the third nitrification basin are denitrified by using activated sludge supplied from the sedimentation basin; an intermittent aeration basin (10) where organic nitrogen from the denitrification basin is decomposed, ammonia nitrogen from the denitrification basin is nitrified, and residual nitrate and nitride are denitrified; a reaeration basin (11) where nitrogen stripping and nitrification of residual ammonia nitrogen are performed at the same time; and a final clarifier (12) where activated sludge is returned to the anaerobic basin after sedimentation and supernatant is discharged to the outside.

Description

Wastewater Treatment Method {A WASTE WATER DISPOSAL PLANT}

The present invention relates to a wastewater treatment method for purifying high concentration organic wastewater which can effectively remove organic matter, nitrogen and phosphorus contained in high concentration organic wastewater such as municipal sewage, livestock wastewater and industrial wastewater, and more specifically, It is a modified system of DEPHANOX process developed in the process, which greatly improves the shortcomings of DEPHANOX process. Re-aeration tank, sedimentation tank in order, the sludge is returned from the sedimentation tank to the anaerobic contact tank, sludge separated from the separation tank flows into the denitrification reactor, supernatant separated from the separation tank flows into the first intermittent aeration tank. To operate continuously.

In general, the nutrients contained in the waste water are inorganic elements, but they flow into rivers, coastal seas, lakes (lakes and reservoirs), etc. to promote algae growth and cause eutrophication.

In addition, when the nutrients contained in the wastewater enter the coastal seas, they cause red tide. If the nutrients are severely decayed at the bottom of the water and odors are generated, they promote water pollution. The substance to be removed before entering the appeal.

In Korea, most sewage and livestock wastewater treatment methods rely on activated sludge. Most suspended solids and organics can be removed by treatment with activated sludge, but only 20-40% of nutrients such as nitrogen and phosphorus are treated.

Processes for treating nutrients such as nitrogen and phosphorus include physical and chemical treatments and biological treatments.

First of all, the physical treatment methods include ammonia degassing, ion exchange using selective adsorption, precipitation of phosphorus using slaked lime and flocculant, and struvite formation of precipitation of nitrogen and phosphorus simultaneously. It is used. However, this method, although the treatment is made selectively, there are disadvantages such as temperature-sensitive and expensive. In addition, the chemical cost and the environment required for operation is difficult to operate because it is specific, and the runoff is unstable in the world as well.

On the other hand, in the biological treatment method, in the case of nitrogen, ammonia nitrogen and organic nitrogen in the dissolved state are nitrified by nitrifying bacteria (ie, Nitrosomonas & Nitrobacter ) under aerobic conditions, and ammonia is converted into nitrate form. Denitrification bacteria (ie, Pseudomonas, Paracoccus denitrifiers) are used as electron acceptors instead of oxygen under anoxic conditions, which are converted to nitrogen gas and released into the atmosphere (denitrification). For phosphorus, wastewater is alternately maintained under anaerobic and aerobic conditions, releasing phosphorus from phosphorus-removing microorganisms (ie, Acinetobacter ) under anaerobic conditions, and in subsequent aerobic conditions, causing the microorganism to overdose phosphorus, Phosphorus in the wastewater is removed by a gentle removal.

The degree of ingestion of the phosphorus of the microorganism in the aerobic condition depends on the amount and type of organic matter introduced into the anaerobic condition, especially in the case of maintaining the pure anaerobic state and in the case of a large amount of organic acid salts such as acetate in pure anaerobic condition The amount of phosphorus released is enhanced, and the intake of phosphorus is enhanced in subsequent aerobic conditions, thereby increasing the throughput.

Therefore, the biological nitrogen and phosphorus removal process is appropriately arranged anaerobic-aerobic-anaerobic-aerobic reactors in accordance with the characteristics of each reactor to induce organic oxidation and nitrification reaction and microorganism intake of phosphorus in the aerobic reactor, and in anaerobic and anoxic reactor Nitrate nitrogen is converted to nitrogen gas to induce denitrification and phosphorus release into the atmosphere.

In general, in the process of treating nutrients as described above, in order to improve the sedimentation of the sludge and to suppress the release of phosphorus, a scavenging reaction tank is disposed before the sedimentation tank. Examples of such a method include the Bardenpho process disclosed in US Pat. No. 3,964,988 to Barnard et al., A single system A / O process, A ² / O process, and the like.

These processes operate in steady-state so that the wastewater passes through the anaerobic and aerobic reactors by separating and arranging the reactors depending on the presence of oxygen. However, these processes have the drawback of excessive power consumption because the internal circulation must be maintained at about four times the wastewater inflow in order to improve the efficiency of the wastewater treatment. Another example of the method is the DEPHANOX process. In this process, anaerobic contacting tanks and separation tanks are used for the microorganisms to adsorb organic matter and induce the release of phosphorus in the anaerobic contacting tank, the organic matter and microorganisms adsorbed in the separation tank are separated into the subsequent denitrification tank and the nitrogen is not adsorbed. Compounds are nitrified in separate reactors and sent to subsequent denitrification tanks for denitrification by microorganisms that adsorb organic matter. That is, the DEPHANOX process is a process in which denitrification and nitrification are carried out in separate sludges and reactors, and the phosphorus is excessively ingested by microorganisms in a subsequent aerobic reactor.

However, since DEPHANOX process has no internal circulation and denitrification is performed only in a single denitrification tank during subsequent treatment after nitrification, high nitrogen removal efficiency cannot be expected.

The present invention provides an effective treatment method for treating organic matter and nutrients, such as livestock wastewater including urban sewage and industrial wastewater (toxic and low C / N ratio wastewater) of the present invention. In particular, the present invention as a complement to the disadvantages of the existing DEPHANOX process can be said to be a process focused on improving the nitrogen treatment. In the existing DEPHANOX process, the nitrification tank serves as a complete mixing reactor, so the nitrification of ammonia nitrogen is more unstable in the tubular flow reactor. Therefore, we tried to develop a process that complements this.

As a specific means for this,

First, the single nitrification reactor of the existing DEPHANOX process is divided into three stages with the same volume, and the first of them is operated as intermittent aeration and the second and third reactors are operated as continuous aeration. In this way, the denitrification of nitrate nitrate occurs in the oxygen state of several to several tens ppm depending on the characteristics of the waste water by using the organic material flowing from the separation tank in the first oxygen aeration tank in the absence of oxygen. In addition, when the single nitrification reactor is separated into three stages, the advantages of the tubular flow reactor (PFR) can be utilized, and thus nitrification can be performed more stably. Secondly, an intermittent aeration process can be provided at the rear of the denitrification tank to significantly reduce the nitrate concentration in the effluent.

1 is a schematic view showing a wastewater treatment apparatus according to the present invention.

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

1: anaerobic contact tank

2: Separation tank

3: first intermittent aeration tank

4: fixed fence, medium

5: submersible pump

6: second nitrification reactor

7: floating fence, medium

8: third nitrification reactor

9: denitrification reactor

10: intermittent aeration tank

11: Reaeration

12: sedimentation tank

The present invention is a biological treatment method devised for more complete nitrogen treatment to compensate for the shortcomings of the existing DEPHANOX process,

The present invention provides an anaerobic contact tank (1), separation tank (2), first intermittent aeration tank (3), second nitriding reaction tank (6), third nitriding reaction tank (8), denitrification reaction tank (9), intermittent aeration tank (10). ), Re-aeration tank 11, and the settling tank (12).

The anaerobic contact tank 1 is used to induce the release of phosphorus when activated sludge is adsorbed to the organic matter introduced into the waste water and used to denitrify it in the denitrification reactor 9.

Another important role of the anaerobic contact tank (1) is to adsorb the toxic substances in the inflow of toxic substances and to perform the nitrification process without the toxic effect of the nitrification bacteria in the subsequent nitrification reactors (3,6,8). .

Separation tank (2) serves to separate the sludge and the supernatant adsorbed organic matter from the anaerobic contact tank, the supernatant containing a large amount of ammonia is transferred to the first intermittent aeration tank (3), the sludge adsorbed organic matter is denitrification reactor It is transferred to (9) and used to increase the denitrification efficiency.

In the first intermittent aeration tank 1 having a fixed fence and a medium, nitrification of ammonia nitrogen and denitrification of nitrate nitrogen occur from the separation tank at the time of exhalation. In addition, denitrification occurs using the organic matter introduced from the separation tank 2 in an oxygen-free state, and may vary depending on the wastewater properties. The aerobic / oxygen-free cycle is carried out at 1 hour / 1 hour intervals, and during exhalation, sufficient oxygen is supplied to the nitric acid from the acid pipe, and in the anoxic state, the oxygen supply is stopped and the water pump 5 operates to circulate the fluid. Play a role. The walls and media in the first intermittent aeration tank 1 utilize a fixed wall, media 4 rather than a floating wall, media to allow this function to be performed smoothly.

In the second nitrification reactor 6 and the third nitriding reactor 8, a flotation tank and a medium 7 contribute to nitrification of residual ammonia nitrogen continuously introduced from the first intermittent aeration tank 3 and separating the tank. It serves to remove most of the ammonia nitrogen flowing in from (2).

In the existing DEPHANOX process, the ammonia nitrogen flowing from the separation tank (2) proceeds in a single nitriding reaction tank, while in the present invention, the nitrification reaction tank is separated into three and induces a tubular flow to more stably remove the ammonia nitrogen.

The denitrification tank 9 is subjected to denitrification of the nitrate nitrogen flowing from the third nitriding reactor 8, and the electron donor is provided from the organic material adsorbed to the activated sludge introduced from the separation tank 2. In addition, organic nitrogen and ammonia nitrogen which are not decomposed from the separation tank 2 are introduced into the denitration reaction tank 9.

In the intermittent aeration tank 10, denitrification of residual nitrate nitrogen flowing from the denitrification reaction tank 9 during anoxia occurs, and nitrification of ammonia nitrogen and organic nitrogen introduced into the denitrification reaction tank 9 from the separation tank 2 during aerobic flow is performed. This will significantly reduce the nitrate concentration in the effluent than the existing DEPHANOX process.

The reaeration tank 11 serves to release nitrogen gas, which is a denitrification by-product flowing from the intermittent aeration tank 10, into the atmosphere, thereby improving sludge settling in the subsequent settling tank 12. In addition, it contributes to the nitrification of residual ammonia nitrogen, which helps to improve the ammonia nitrogen removal rate in the whole process.

The settling tank 12 is used to separate the sludge and the supernatant flowing from the reaeration tank 11. The separated sludge is returned to the anaerobic contact tank 1 and the supernatant is discharged.

As described above, according to the wastewater purification process, it is possible to maximize the treatment of nitrogen and phosphorus, which are the main causes of eutrophication.

The biological treatment process of the present invention compensates for the shortcomings of the existing DEPHANOX process by transforming a single nitrification reactor of the DEPHANOX process into a tubular flow and operating the first reactor following the separation tank 2 as intermittent aeration. It has the advantage of reducing nitrate concentration.

In the case of toxic and waste water, the anaerobic contact tank (1) is brought into contact with microorganisms to adsorb toxic substances in the waste water to microorganisms, and the concentrated microorganisms are separated from the separation tank (2) to denitrate under anoxic state. Since only transfer to the reaction tank (9), the effect on the nitrifying bacteria which are relatively vulnerable to toxicity is reduced, so that the nitrification reaction in the nitriding reaction tank can be carried out without difficulty.

In addition, in the case of the nitrification reactor, the conventional single reaction tank is separated into three nitrification tanks to induce tubular flow to effectively proceed the nitrification reaction with slow reaction rate, and the nitrification of slow growth can be concentrated by using a carrier or a medium. The time required for the reaction can be shortened, and as a result, the volume of the reactor can be reduced. It can be widely applied to clean domestic small-scale sewage and wastewater as well as livestock and industrial wastewater.

Claims (2)

An anaerobic adsorption tank (1), which is responsible for adsorption of organic substances and toxic substances in the introduced wastewater and induces phosphorus release; A separation tank (2) for separating the solids and the dissolved substances, A first intermittent aeration tank 3 connected to the separation tank 2 and performing nitrification and denitrification; A second nitriding reactor (6) and a third nitriding reactor (8), which are connected to the first intermittent aeration tank (3) and perform nitrification more completely; A denitrification tank (9) connected to the third nitriding reactor (8) and denitrification of the nitrate introduced from the third nitrification reactor (8) using an organic material adsorbed to the activated sludge flowing from the separation tank (2); An intermittent aeration tank (10) connected to the denitrification tank (9) and decomposing the organic nitrogen introduced from the denitrification tank and nitrifying the ammonia nitrogen and denitrification of the residual nitrate; A reaeration tank 11 connected to the intermittent aeration tank 10 in which degassing of nitrogen gas as a denitrification by-product and nitrification of residual ammonia nitrogen proceed; In connection with the re-aeration tank 11 and separating the activated sludge and the supernatant flowing from the re-aeration tank 11, the supernatant is discharged and composed of a settling tank 12 is returned to the anaerobic contact tank (1), Separation of the nitrification reaction tank followed from the separation tank (2) into three to perform nitrification more stably through the tubular flow, and the intermittent aeration tank after the denitrification reaction tank, characterized in that the wastewater treatment method. The wastewater according to claim 1, wherein the first intermittent aeration tank 3 is operated as an intermittent aeration to induce a denitrification reaction with organic substances contained in the supernatant flowing from the separation tank 2 to reduce the concentration of nitrate in the effluent. Treatment method.