KR0165168B1 - Waste water treating equipment and method using pure oxygen activated sludge process having anaerobic sludge treating section - Google Patents

Abstract

In order to improve the precipitation and treatment efficiency of organic matter, phosphorus, nitrogen and the like in aerobic biological treatment using pure oxygen-aeration activated sludge, the reaction tank is made into a closed multi-stage structure, and the return sludge is treated in anaerobic / anaerobic sludge treatment tank. Processing apparatus and method. The water quality of the effluent after the anaerobic / anaerobic sludge treatment plant according to the present invention was compared with that of the present invention. The mean concentrations of dissolved COD, phosphorus, and total nitrogen were 60 mg / l, 2.1 mg / l and 18 mg / l, respectively, when there was no sludge treatment on the basis of the mean COD concentration of 850 mg / l. The mean effluent COD, phosphorus and total nitrogen concentrations were improved to 52 mg / l, 1.4 mg / l and 13 mg / l, respectively

Description

Apparatus and method for wastewater treatment by oxygen-aeration activated sludge method including anaerobic / anaerobic sludge treatment tank

FIG. 1 is a device conceptual view of the present invention.

Figure 2 shows a section A-A of Figure 1.

Figure 3 shows a cross section B-B in Figure 1.

FIG. 4 shows a C-C cross section (ie a partition) of FIG.

There are gas passing parts in the upper part 2 and waste water and sludge passing parts in the lower left part.

FIG. 5 is a graph comparing the COD of the inflowing sludge with the COD of the sludge treatment tank.

6 is a graph comparing nitrate nitrogen in the sludge treatment tank and nitrate nitrogen in the influent sludge.

7 is a graph comparing the phosphorus in the phosphorus and sludge treatment tanks of the inlet transport sludge.

DESCRIPTION OF THE REFERENCE NUMERALS

1: Oxygen inflow part 3: Closed vapor phase part of a multi-stage reaction tank

4: Liquid part of a closed multi-stage reaction tank 6: Stirrer

10: Settling tank, 11 ~ 15: Flow control valve

15: Return pump 21: Partial sludge treatment tank

22: Whole sludge treatment tank 24: Gas flow

2: Waste water inflow device 18, 19, 20: Sludge inflow location

7: baffle 5: swash plate

25: Wastewater and sludge flow

The present invention relates to an apparatus and a method for treating wastewater such as municipal sewage, industrial wastewater, livestock wastewater, sewage wastewater, sewage, and the like. More specifically, the present invention further comprises an anaerobic / anaerobic sludge treatment process after a pure oxygen- The present invention relates to a wastewater treatment apparatus and method that can increase the sedimentation efficiency and efficiently treat organic matter, phosphorus, nitrogen, and the like so that a partial or whole sludge treatment tank, a whole-amount conveyance line, or the like can be selected depending on the state and amount of the sludge.

Activated sludge method is widely used as a typical biological treatment method of organic wastewater. The general process consisted of the step of water → first settling tank → aeration tank → second settling tank → discharge stage and consists of concentrating and dehydrating the sludge obtained after the second settling tank and discarding it or returning it to the aeration tank immediately. However, in the general wastewater treatment process as described above, the effect of reducing the volume of disposal sludge by disposing the sludge without any special treatment or lowering the water content of the simple sludge to the original water content can be expected. However, the sedimentation efficiency of the wastewater, , Nitrogen and other disposal problems still remain as a problem.

Recently, interest in the efficient treatment of sludge has been increasing in the late 80s and 90s, and many studies have been conducted. According to the theory on which these studies are based, they are roughly classified into three categories as follows.

The first is to increase precipitation efficiency by extracellular materials. The dissolution of nutrient salts, including extracellular polymers (ECP), maintains good microbiological conditions, It is advantageous to agglomerate. The polymer of the cells is relatively excreted in the endogenous respiration phase, but not sufficient for cell aggregation, thus requiring a process of producing a polymer of sufficient cells for cell aggregation.

For example, Yun et al. (US Patent No. 5,128,040) discloses a method of treating a sludge of an anoxic / anaerobic tank in an anoxic / anaerobic tank to improve sedimentation of trickling filter (TF) (SVI) and suspended solids (SS) of the effluent by mixing them for a short period of time under aerobic conditions. The optimal anoxic tank retention time (HRT) was calculated at 0.68 ± 0.02 Kg COD / ㎥ d, and maximum of 160 mg ECP / gMLSS at 45 min anoxic retention time and at least 70 mg ECP / gMLSS at 90 min residence time The suspended solids (SS) of the effluent were 10 mg / l and 25 mg / l, respectively. Domestic experimental results showed a similar pattern. When the sludge volume index was 150, the polymer (ECP) of the cells showed 150 ~ 200 mg of ECP / gMLSS.

Second, it relates to improvement of sedimentation by anoxic / anaerobic selector and biological (P) removal principle. s. Some saturable microorganisms such as S. Natans, Type 021N, and Nostocoida may not utilize nitrate-nitrogen and nitrite-nitrogen as electron acceptors. In this condition, the flux-forming microorganism can utilize nitrate nitrogen as an electron acceptor without dissolved oxygen, so that the precipitation property and the high nitrogen removal efficiency can be expected in the precipitation tank.

The third is the theory of sedimentation and organic matter removal rate according to metabolic analysis of microorganisms. Microbial metabolism is divided into aerobic and anaerobic metabolism. The aerobic metabolism involves the synthesis of new microorganisms using organic matter and the respiratory metabolism to get energy. In aerobic treatment, about half of the organic matter is synthesized as microorganisms. However, the yield of microorganisms in anaerobic metabolism is about 1/10 that of aerobic metabolism (microorganism yield Y = 0.6 mg VSS / mgBOD _{5 for} aerobic metabolism _, 0.06 for anaerobic metabolism mgVSS / mg BOD ₅ ), and most of the organic substances are used to produce fermentation products through the fermentation metabolic pathway. Chdoba et al. (1991) reported that anaerobic conditions increase the sedimentation of sludge and reduce the amount of sludge generated in the modified activated sludge process, which anaerobically treats the transport sludge. Westgarth et. According to al (1964), when microorganisms grown in anaerobic conditions are converted to aerobic conditions, it is easier to consume oxygen, which means that organic matter removal is more effective. Sludge volume index (SVI) indicates that saturation bulking is suppressed as a result of anaerobic digestion. Microscopic examination revealed few species of Beggiatoa, a mysterious microorganism.

Among the above-mentioned researches on the recent sludge treatment, Yun patent (US Patent No. 5128240) mentioned above adopts the flesh-and-water method not the activated sludge method among the basic methods of wastewater treatment. The trickling filter, which removes organic matter by the microorganisms flowing on the surface of the filter media, flows downward when the wastewater flows over the fixed filter material filled with the gravel. The trickling filter is sensitive to temperature conditions and is a complete wastewater treatment method due to microbial desorption, I did not. In this way, since the commercial method does not perform its role as a biological treatment, it is not suitable for treating wastewater having a poor water quality or a large amount of wastewater. In addition, the spraying water does not require the energy required for oxygen supply, but there is also a problem that the installation area or the installation area is much larger than the activated sludge method. Due to these disadvantages, there are only a few cases where the spraying method is actually applied at home and abroad.

Chudoba et. Al treated the sludge with anaerobic stabilization process. (Chudoba et < RTI ID = 0.0 > al., ≪ / RTI > This is due to the physiological shock of insufficient oxygen and food to the microorganisms in the sludge for a long period of time of about 3 hours. When the ATP is used as an energy source and then converted into an exhalation state where the external substrate is supplied, energy is generated instead of microorganism growth It will be done. This study, which focused on lowering the yield of microorganisms in sludge by treating sludge in anaerobic condition for 3 hours or longer, showed the effect of reducing Sludge Volume Index (SVI) of aeration tank to 60 mg / l . However, the sludge volume was reduced by prolonged anaerobic treatment, but organic matter (140 mg / l) discharged was increased rather than the effluent (90 mg / l) by the anaerobic untreated activated sludge process. In addition, it is difficult to survive microorganisms due to prolonged anaerobic treatment. Furthermore, improvement of treatment efficiency such as nitrogen or phosphorus in wastewater was not considered.

Accordingly, an object of the present invention is to improve the efficiency of biological wastewater treatment by adopting a pure oxygen-aeration activated sludge method in treatment of wastewater and maintaining a high microbial concentration by supplying pure oxygen into the reactor.

Another object of the present invention is to improve the precipitation efficiency when the sludge is recycled to the pure oxygen aeration tank by inducing the elution of the sticky substance such as polymer in the anaerobic / anaerobic state, thereby improving the removal efficiency of nitrogen and phosphorus as well as organic matter, And to provide a waste water treatment apparatus and method capable of reducing the discharge of waste water.

The third object of the present invention is to improve the concentration of the effluent when the concentration and the concentration of influent wastewater are changed so that the Biochemical Oxidation Demand (BOD), nitrogen and phosphorus are stable and low concentration And to provide a waste water treatment apparatus and method for discharging wastewater.

A fourth object of the present invention is to provide a wastewater treatment device capable of increasing the efficiency of wastewater treatment by selecting a partial total amount sludge treatment tank, a sludge return line, or the like depending on the season or the components of the wastewater, And methods.

A fifth object of the present invention is to provide an economical and efficient wastewater treatment by adding a sludge treatment tank and a line easily even if there is only a small space in a wastewater treatment apparatus according to the existing activated sludge method.

Hereinafter, the configuration of the present invention will be described.

In the activated sludge process, the pure sludge activated sludge process was first developed by Okun in 1949, but the process itself proved to be superior, but it was not widely available due to its high production cost of pure oxygen. However, as oxygen began to be produced by pressure swing adsorption (PSA) method, the potential of applying pure oxygen to wastewater treatment increased.

US Union Carbide applied pure oxygen to wastewater treatment in late 1966 and succeeded in applying wastewater treatment method using pure oxygen to Detroit with a sewage treatment capacity of 1,135,500㎥ / d in 1970 . Table 1 shows the comparison of activated sludge method using pure oxygen aeration activated sludge method and general air aeration method.

As shown in Table 1, the activated oxygen sludge method is a process that enables efficient treatment of wastewater during a short residence time by maintaining a high concentration of mixed micro-liquid suspended solids (MLSS) in a reactor and injecting pure oxygen. The return sludge of pure oxygen aeration activated sludge method has higher concentration than the sludge method of general air aeration activated sludge method. In Korea, the application of activated oxygen sludge method is applied to the desulfurization agent of Gunsan and the Hansol paper of Jeonju, but the second settling tank is likely to deteriorate because of the high concentration of microorganisms in the reaction tank. According to the sewage design standard, the design standard of the final sedimentation basin should meet the criteria of water surface area load of 20 ~ 30㎥ / ㎡ / d, solid matter load of 150 ~ 170Kg / ㎡ / d and overflow ware load of 190㎥ / m / d. Most are designed based on a number of area loads. According to the results of the study, it was found that the pure oxygen aeration activated sludge method is designed based on the water surface area load, which is not much different from the air aeration activated sludge method. However, in the activated sludge method, the concentration of microorganisms (MLSS) in the reactor sent to the settling tank is twice that of the general air-aeration activated sludge method, so that the instability of the second settling tank is expected. However, It is thought that the treatment efficiency of the conveying sludge is better than that of the conveying sludge.

Therefore, an anaerobic / anaerobic tank capable of treating a high concentration of sludge after the closed-type multi-stage pure oxygen aeration tank and the secondary settling tank was installed and the experiment was conducted.

The three-stage, multi-stage, sealed reaction tank applied to the invention has a structure of a fl ow flow tank. In a CFSTR (continuous flow stirred-tank reactor), aerobic biological treatment often causes bulking due to overproduction of pathogenic microorganisms, and it is difficult to obtain stable effluent under impact loading. However, the plug flow reactor (PFR) adopted by the present invention is resistant to bulking and impact loads. In the case of a single mixed reaction tank, bulking occurs due to marsh microorganisms that grow well at low concentration when the amount of influent organic matter decreases in the reaction tank. However, in the case of the fl uid flow reactor, concentration gradient is generated according to the flow and it acts as a microorganism selection tank. And can cope with the shock load stably.

In addition, the reaction tank of the present invention can prevent a phenomenon that treatment efficiency is lowered due to temperature deterioration due to a high efficiency of using pure oxygen and a very small amount of discharged exhaust gas.

Further, the anaerobic / anaerobic sludge treatment tank of the present invention utilizes the characteristic of the secondary precipitation sludge, that is, it contains a large amount of microorganisms. When the microorganisms contained in the secondary precipitation sludge are treated for a suitable period of time under a specific environment or an anaerobic / anaerobic condition, the sludge secretes the mucous component such as the polymer of the cells. Therefore, when the sludge treated in the anaerobic / anaerobic sludge treatment tank of the present invention is returned to the aeration tank, it is possible to remarkably improve the sedimentation efficiency of the secondary settling tank. This mucilage component has an increased chemical oxygen demand (COD), nitrogen and phosphorus, and can improve the effluent treatment efficiency. That is, the sludge treatment tank of the present invention is used not only for removing organic matter but also for treatment of nitrogen and phosphorus, which is a problem in the water system.

The anaerobic / anaerobic sludge treatment tank of the present invention may be misunderstood to be the same or similar to the anaerobic tank in the anaerobic stabilization process of Chudoba. Chudoba's anaerobic tank is an anaerobic digestion reactor for digesting sludge by staying in the sludge for a long period of time and its main purpose is to reduce sludge volume. However, the sludge treatment tank of the present invention is a reaction tank for retaining microorganisms for up to 2 hours, preferably 30 to 60 minutes under the special condition of anaerobic / anaerobic to secrete a mucus component called extracellular polymer. Which can be significantly improved and further functions as a microbial selector to select the flux-forming microorganisms and to remove nitrogen and phosphorus.

Let's look at the problem of inhalation in the wastewater. Inorganic microorganisms release Ortho-P in solution under anaerobic conditions, which is called phosphorus release. When microorganisms are converted from anaerobic conditions to aerobic conditions, the phosphorylated microorganisms are synthesized as Poly-P by over-consuming the solution of polyphosphoric acid. This is called Phosphorus Luxury Uptake. The most important bacteria involved in the removal of such phosphorus is Acinetobacter spp. However, there is a case where phosphorus is released due to the result of self-decomposition of excess sludge, which is called secondary P-release. Wenzel et al. (1986) reported that the second round of the anaerobic conditions made phosphorus ingestion impossible in the subsequent process, leading to the death of the important phytophthora, Ashinotobacter, and the mass reduction of the spider organism. (M.C., Wenzel et al., Water S. A., vol. 12 (4), p209 (1986).) Increasing the anaerobic residence time excessively has a negative effect on the phosphorus removal efficiency due to secondary release. Therefore, the anaerobic / anaerobic sludge treatment process of the present invention is preferably carried out for 30 to 60 minutes, thereby achieving the purpose of the inhalation by causing the phenomenon of excessive intake of phosphorus when recycled to the net aeration tank.

In the present invention, the wastewater is first introduced into the closed-type pure oxygen aeration tank, and the wastewater discharged through the pure oxygen aeration tank is subjected to the anaerobic or anaerobic settling tank and the sludge treatment tank through the settling tank. Thereafter, the sludge treated for 30 to 60 minutes in the sludge treatment tank is introduced into the pure oxygen aeration tank again according to the route selection, and the polymer of the eluted cell can remarkably improve the sedimentation efficiency. The anaerobic or anoxic sludge treatment tank has the effect of suppressing the growth of the sludge causing the sludge bulking and the growth of the sludge-forming microorganism, thereby selecting the floc-forming microorganism. Therefore, it is possible to prevent the sludge- And the removal efficiency of organic substances, suspended substances, nitrogen and phosphorus can be increased.

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

As a condition of aerobic biological treatment, pure oxygen (1) is injected into the first stage (3), and pure oxygen is dissolved in the first stage (4) of the liquid phase by the agitator (6) do. The inflowing oxygen flows like 24 in FIG. 2 at a pressure low enough to cause a gaseous flow, and the partition (8) is installed slightly higher than the water surface so that the reactor has a closed structure. The liquid phase enters the inflow wastewater 2, the transport sludge 19, and the treated sludge 18, 20 just above the water surface as shown in FIG. The flow passes through the lower portion of each stage as shown in 25 of FIG. 3, and the swash plate 5 is installed at each end so that no blind spots are generated when mixing at each stage. At each end, the partition (7) is shifted as shown in Fig. 3 to make the structure of the whole reactor and the fl ow flow reaction tank. And a cross-sectional view of the partition structure for 7 is similar to FIG. The effluent treated in the reaction tank is discharged (23) via the pipe (9) through the settling tank (10).

Sludge treatment can be divided into two processes. The first is the case of processing the entire transport sludge. The second method is to process only a part of the return sludge and return the remaining part to the first stage. A large reaction tank should be used for full-volume treatment and a reaction tank that is not large for some treatments. If the sludge is discharged in excess, two sludge treatment tanks may be used at the same time. Depending on the type, composition and amount of wastewater, the sludge can be treated in whole or in part. If necessary, the sludge may be discharged as an abandonment tank.

That is, the constitution of the present invention is a multi-stage reaction tank for pure acid vesicles; Sedimentation tank; An anaerobic / anaerobic and a complex and selective sludge treatment tank. The configuration of the present invention is illustrated in FIG. However, FIG. 1 is only one example of the configuration of the present invention, and the configuration of the present invention is not limited to the first embodiment and the drawings.

As shown in FIG. 1, each of the valves 1 (11) to 5 (15) is constructed in order to apply the most suitable sludge treatment method to the multistage reaction tank according to various wastewater conditions .

First, valve 1 (11), valve 2 (12), valve 3 (13) and valve 5 (15) are closed when conveying without sludge treatment. Valve 2 (12) is a valve for regulating the sludge concentration (MLSS) in the reactor, and opens the sludge if necessary. And the valve 1 (11) can adjust the flow rate.

Second, in the case of the full sludge treatment, in the case where the valve 3 (13), the line 16, the partial sludge treatment tank 21, the line 18, the valve 4 (14) The valve 1 (11) is opened and the entire amount is sent to the sludge treatment tank (22) through the pump (15). The treated sludge enters the first stage via line 20.

Third, in the case of partial sludge treatment, the valve 5 (15), the line 17, the total amount sludge treatment tank 22, the line 20 are absent or not operated, (Line 18 flow rate / line 19 flow rate = 0.1 to 0.9) is sent to the partial sludge treatment tank 21 through line 15 and flows into the third-stage inlet (22 in FIG. 2) through line 18 . Some of the remaining untreated secondary settler flow (line 18 flow rate / line flow = 0,1 to 0.9) sludge opens valve 4 (14) through line 17 and flows first through line 19.

[Example]

For the purpose of improving the treatment efficiency by using the pure oxygen reflux and multi - stage sludge treatment tank, the experimental reactor was a sealed three - stage structure with a size of 38 cm W x 131 cm L x 20 cm H (99.6 L). The amount of oxygen introduced into the first stage was 200 ~ 300ml / min when 100% oxygen was injected, and the amount and concentration of oxygen discharged from 3rd stage were 40 ~ 80% (volume ratio) and 10 ~ 30ml / min. The stirring speed of the reactor was set to 60 rpm to induce the mixing of oxygen dissolved and non-dissolved matter. In the sludge treatment tank, all or part of the transport sludge is retained in the anaerobic or anaerobic condition for a predetermined time together with stirring (stirring rate: 60 rpm), and then sent to the reaction tank.

- Total size of sludge treatment tank = 14 cmΦ * 50 cm H = 7.71

- Size of partial sludge treatment tank = 8cmΦ * 40cmH = 2.01

The wastewater used in the present invention was a wastewater containing 280 mg / l of glucose, 280 mg / l of acetic acid, 30 mg / l of yeast extract and 384 mg / l of ethanol as the carbon source and a nutrient source (nitrogen, phosphorus) The elements were injected in a similar manner to the sewage component ratios of 850 mg / l of dissolved COD concentration, 40 mg / l of ammonia nitrogen (NH-N) and 5 mg / l of phosphorus (PO-P). The average concentration of microorganisms (MLSS) in the reaction tank during operation was about 2000 mg / l. In addition, the influent pH was 6.5 and the water temperature was 16 ± 2 ° C. Table 2 shows the operating conditions for the oxygen uptake experiment, and the experimental values over time were measured as stable as possible. The results of the experiment are shown in Table 3.

In order to maintain at least 4000 mg / l of the microorganism (MLSS) in the original reaction tank, the experiment was carried out by keeping the microorganism (MLSS) in the reaction tank at about 2000 mg / It was because of the addition of acetic acid and ethanol in the acetic acid, ethanol, glucose and yeast extract, which constitute the carbon source. In particular, it is known that acetic acid is a low-molecular-weight, soluble carbohydrate, which causes excessive growth of mature microorganisms upon injection. However, as shown in FIGS. 5 and 6 of FIG. 4, the treatment efficiencies of the whole sludge treatment tank and the partial slush treatment tank were improved by the lysis of the nutrient salts including the polymer of the cells, and the release of phosphorus was also measured .

*week;

1. Time elapsed: Time elapsed after at least 1 day. Therefore, it is usually 1 day, but in some cases, when an external incident occurs, the system is restored to its stable state, that is, it is analyzed after 2 to 3 days.

2.COD: chemical oxygen demand

3.TN: Total Nitrogen

The mean concentrations of dissolved COD, phosphorus, and total nitrogen were 60 mg / l, 2.1 mg / l and 18 mg / l, respectively, when there was no sludge treatment on the basis of the mean COD concentration of 850 mg / l. The mean effluent COD, phosphorus and total nitrogen concentrations were improved to 52 mg / l, 1.4 mg / q and 13 mg / l, respectively.

As described above, the present invention solves the disadvantage of the spraying imaging method, which is not suitable for treating wastewater having a poor water quality or a large amount of wastewater in the patent of Yun et al. That is, by adopting the activated sludge method of pure oxygen aeration, the present invention increases the efficiency of biological wastewater treatment by supplying pure oxygen into the reactor to maintain a high microbial concentration.

In addition, the present invention compared to the one in which the volume of the anaerobic tank is 1 to 2.5 times the volume of the aeration tank in the experiment of Chudoba et al., The sludge treatment tank of the present invention is 0.02 ~ 0.08 of the aeration tank, And solved the problems such as non-economical due to construction.

Thirdly, the present invention takes an anaerobic / anaerobic sludge treatment process only for about 30 to 60 minutes, and thus, when the anaerobic stabilization for 3 hours or more as in Chudoba's experiment is carried out for a long time, it becomes difficult or impossible to survive microorganisms. But did not significantly affect the biological treatment efficiency of the sludge.

Fourth, the present invention improves the sedimentation efficiency when the sludge is recycled to the pure oxygen aeration tank by inducing elution of the sticky material such as polymer of the cell by treating the sludge in an anaerobic / anaerobic condition for 30 to 60 minutes.

Fifth, the present invention promotes the removal efficiency of nitrogen and phosphorus as well as organic matter by inducing excessive intake of phosphorus through the oxygen-aeration process after the anaerobic / anaerobic sludge treatment process.

Sixth, the present invention can discharge the biochemical oxygen demand (BOD), nitrogen and phosphorus in a stable and low concentration even when the mode pure oxygen is uniformly distributed at each end of the aeration tank and the state and concentration of the influent wastewater are changed greatly It is expected.

Seventh, the present invention can increase the efficiency by seasoning wastewater according to the season or wastewater components, or by selecting part or whole amount sludge treatment tank, sludge return line, etc. according to sludge, condition and amount.

Eighthly, since the sludge treatment tank and the line can be easily added even if there is only a small space in the wastewater treatment apparatus according to the existing activated sludge method, the installation cost is very economical.

Claims (15)

A pure oxygen uptake process in which pure oxygen is introduced into the wastewater to maintain the microorganism at a high concentration and the wastewater can be treated during a short residence time; A precipitation step of separating the discharged water subjected to the pure oxygen-aeration process into a solid and a liquid; An entire amount or partial sludge treatment step of treating the sludge separated in the precipitation step in an anaerobic / anoxic tank to elute the extracellular polymer to increase the sedimentation efficiency; And recycling the sludge having undergone the sludge treatment process to the pure oxygen aeration process. The method of claim 1, wherein the sludge recycling process recycles the sludge after the entire sludge treatment process to the first stage of the pure oxygen aeration process. The method of claim 1, wherein the sludge recycling process recycles the sludge after the sludge treatment process to the aeration tank after the second stage of the pure oxygen aeration process. The method according to claim 1, wherein the sludge recycling process recycles the sludge having undergone the sludge treatment process after the partial sludge disposal process to a stage subsequent to the second stage of the net vesiculation process, and recycles the sludge conveyed without passing through the sludge disposal tank to the first end disposal tank Wherein the wastewater treatment method comprises the steps of: The method for treating wastewater according to claim 1, wherein the anaerobic / anoxic sludge treatment is performed within a range of 30 minutes to 2 hours. The method for treating wastewater according to claim 5, wherein the anaerobic / anoxic sludge treatment is performed within a range of 30 minutes to 60 minutes. The method of claim 1, wherein the pure oxygen aeration process is a fl ow flow process that is resistant to impact loads and reduces bulking. An effluent treatment system comprising a sludge return line and an anaerobic / anaerobic sludge treatment tank. The wastewater treatment device according to claim 8, wherein the pure oxygen aeration tank has a three-stage or more multi-stage structure. 10. The method of claim 8, Wherein the pure oxygen aeration tank is a closed aeration tank capable of increasing pure oxygen efficiency. 9. The wastewater treatment apparatus according to claim 8, wherein the pure oxygen aeration tank comprises a swash plate at the bottom of the aeration tank and at the bottom of the partition for smooth mixing of pure oxygen and wastewater. 9. The wastewater treatment apparatus according to claim 8, wherein the pure oxygen aeration tank includes an agitation device in each aeration tank to increase oxygen dissolution. 9. The wastewater treatment apparatus according to claim 8, wherein the anaerobic / anoxic sludge treatment tank includes an agitation device. 9. The wastewater treatment device according to claim 8, wherein the vapor phase portion of the aeration tank prevents the respective ends of the aeration tank from being blocked from each other in order to smoothly dissolve and flow pure oxygen at each end of the aeration tank. The method according to claim 8, wherein the sludge conveying line includes a sludge treating tank and a conveying line depending on the amount and condition of the sludge discharged after the settling step; Residual sludge treatment tank; A path for conveying the aeration tank without passing through the sludge treatment tank; And a complex sludge treatment tank and a return line configured to be able to select one or more paths among the sludge treatment tank and the return line.