KR20100046745A - Methods of advanced wastewater treatment - Google Patents

Abstract

PURPOSE: An advanced sewage processing method is provided to improve removal efficiency of phosphorus and nitrogen when sewage is biochemically processed, and to prevent environmental contamination of water. CONSTITUTION: An advanced sewage processing method includes the following steps: processing inflow water with phosphorus in an anaerobic tank(100); denitrifying outflow water of the anaerobic tank in an anoxic tank(200); nitrifying and performing a dephosphorus process of the outflow water in an aerobic tank(300); precipitating the outflow water in the aerobic tank; and denitrifying the outflow water in a sulfur-based denitrification tank(500). The aerobic tank is filled with fluidized bed microbial carriers.

Description

Methods of Advanced Wastewater Treatment

The present invention relates to a high sewage treatment method, and more particularly, to a sewage treatment method capable of effectively removing nitrogen and phosphorus contained in sewage.

Generally, sewage treatment methods can be largely classified into physical methods, chemical methods, and biological methods, and each treatment method is determined by the characteristics of the incoming sewage, the use of the treated effluent, the suitability and economical efficiency of the treatment method.

As the physical sewage treatment method, ammonia removal by filtration, filtration, distillation, flotation, foam secretion method, cooling, separation using a gas layer, surface dispersion method, reverse osmosis method and absorption are selectively used. As the chemical sewage treatment method, activated carbon adsorption, agglomeration, precipitation, ion exchange electrochemical treatment, electrodialysis, oxidation and reduction are selectively used. Biological sewage treatment methods include bacterial assimilation, algae extraction and nitrification-denitrification or denitrification-nitrification.

Nitrogen and phosphorus contained in sewage are nutrients, and if discharged without proper removal, it is a major cause of eutrophication, causing abnormal breeding of algae in the closed waters of the lake and polluting water supply and industrial water. Since it is caused, there is a need to effectively remove nitrogen and phosphorus contained in the sewage.

A representative sewage treatment method currently used to remove nitrogen and phosphorus in sewage is an activated sludge process. However, the activated sludge process has a disadvantage in that most of the nitrogen and phosphorus are discharged together with the discharged water because the removal efficiency of nitrogen and phosphorus in the sewage is very low.

In order to solve the above problems, many chemical and biological methods for removing nitrogen and phosphorus contained in sewage have been developed.

Conventional methods for removing biological nitrogen and phosphorus include anaerobic / oxygen-free / aerobic processes (A 2 O), Bardenpho process, and UCT process. Each of the processes is basically equipped with one or more anaerobic tank, anoxic tank, aerobic tank, the deformation is made in the process such as internal conveying or sludge conveying.

In the biological process, when the first treated water flows into the anaerobic tank, low molecular weight organic matter is produced by fermentation of microorganisms in the anaerobic tank, and the phosphorus-removing microorganism using these organic matters forms polyhydrobutylate (PHB) as an intracellular storage material in the anaerobic tank. It will release phosphoric acid during synthesis. Conversely, in the aerobic tank, the phosphorus-removing microorganism decomposes polyhydrobutylate (PHB) while ingesting excessive amounts of phosphoric acid above the amount of phosphoric acid released from the anaerobic tank, and the microorganisms ingesting excessive phosphorus are removed in the form of excess sludge.

On the other hand, in the case of nitrogen, organic nitrogen is converted to ammonia, ammonia is converted into nitric acid form by nitrifying microorganisms in an aerobic tank, and nitric acid is discharged into the air through a process of being converted into nitrogen gas by denitrifying microorganism bacteria in an anoxic tank. Nitrogen content in sewage is reduced.

However, even with such a conventional biological sewage treatment method, there is a disadvantage in that it is difficult to stably obtain sufficient removal efficiency of nitrogen and phosphorus, and in particular, it is necessary to supplement nitrogen removal. In particular, domestic sewage is difficult to remove nitrogen because the total amount of organic matter is low compared to the total amount of nitrogen included in the influent required for biological treatment, there is a problem that the denitrification effect by biological treatment is not good.

In the biological sewage treatment method, the present invention seeks to provide an advanced sewage treatment method capable of improving the removal efficiency of phosphorus while removing nitrogen more efficiently.

Sewage treatment method according to an embodiment of the present invention comprises the steps of phosphorylating the influent in an anaerobic tank under anaerobic conditions; Firstly denitrifying the effluent of the anaerobic tank in an anaerobic tank; Dephosphorizing and nitrifying the effluent of the anaerobic tank in an aerobic tank; Precipitating the effluent of the aerobic tank in the settling tank; And a second denitrification treatment of the effluent of the settling tank in the denitrification tank, wherein the aerobic tank is filled with a sponge-type fluidized bed microbial carrier, and the denitrification tank is filled with granular conditions.

In other words, the influent is subjected to phosphorylation in an anaerobic tank under anaerobic conditions. At this time, the anaerobic tank under anaerobic conditions contains anaerobic microorganisms, and under the anaerobic conditions, the organic matter in the influent flowing out of the primary sedimentation tank into the anaerobic tank is fermented with a low molecular weight substance to phosphorylate through a biological reaction that releases phosphoric acid. You will perform the steps.

Next, the first step of denitrification is carried out in the anaerobic tank effluent. The denitrification microorganism group included in the anoxic tank under anoxic conditions converts nitric acid (NO ₃ ) into nitrogen (N ₂ ) gas using low molecular weight organic materials and discharges nitrogen (N ₂ ) gas into the air. Will be performed.

Here, it is preferable to further include a step of separating a part of the inflow water flowing into the anaerobic tank to flow into the anaerobic tank without going through the anaerobic tank. That is, a low molecular weight organic material introduced into the anaerobic tank may be consumed by a fermentation reaction for releasing phosphoric acid by the anaerobic microorganism, resulting in a lack of an energy source of the denitrifying microorganism in the anoxic tank. In order to compensate for this, by separating a part of the influent flowing into the anaerobic tank and flowing directly into the anaerobic tank without going through the anaerobic tank, the low molecular organics contained in the influent can be supplied as an energy source for the denitrification microorganism of the anaerobic tank. At this time, a part of the influent flowing into the anoxic tank is 80% by volume or less of the total influent volume, thereby further improving the efficiency of dephosphorization in the anaerobic tank and primary denitrification in the anaerobic tank.

Next, the step of dephosphorizing and nitrifying the effluent of the acid-free tank in an aerobic tank is performed. The dephosphorus microorganism group included in the aerobic tank under aerobic conditions is ingested in excess of phosphoric acid generated in the anaerobic tank, and the dephosphorus microorganism group absorbing phosphoric acid is subjected to a dephosphorization treatment through a separate separation process. In addition, nitrifying the nitrification microorganism group included in the aerobic tank under aerobic tidal phase is to perform the nitrification step to convert the ammonia of the influent water introduced from the anoxic tank to nitric acid. As such, the step of dephosphorization and nitrification is carried out simultaneously in an aerobic bath under aerobic conditions.

At this time, the aerobic tank is filled with a sponge-type fluidized bed microbial carrier to include dephosphorized and nitrified microorganism groups. The material of the sponge-type fluidized bed microbial carrier is preferably in the form of a porous foam made of polyurethane. Sponge-type fluidized bed microbial carrier is in the form of a cube of 12 to 15mm, and includes a microbial group that removes organic matter while flowing in an aerobic tank, a nitrification microorganism group that performs nitrification, and a dephosphorous microorganism group that excessively ingests phosphorus. The fluidized bed microbial carrier preferably has a specific gravity of at least one after microbial attachment.

Here, it is preferable to further include a step of introducing a part of the effluent from the aerobic tank into the anaerobic tank while flowing the effluent from the aerobic tank into the settling tank for the next step of the sedimentation treatment. That is, part of the effluent from the aerobic tank containing a large amount of nitric acid (NO ₃ ) by the nitrifying microorganism group in the aerobic tank is returned to the anoxic tank, and the nitric acid (NO ₃ ) is converted into nitrogen (N ₂ ) gas by the denitrifying microorganism in the anoxic tank. By converting and discharging the nitrogen (N ₂ ) gas into the air, the efficiency of primary denitrification can be further improved. At this time, the denitrifying microorganism separates a part of the inflow water flowing into the anaerobic tank for sufficient supply of low molecular weight organic matter which is needed as an energy source in converting nitric acid (NO ₃₎ into nitrogen (N ₂ ) gas, and does not go through the anaerobic tank. It is possible to further improve the primary denitrification efficiency by performing simultaneously with the replenishment process by inflow immediately.

At this time, it is preferable that a part of the outflow water from the aerobic tank flowing into the anoxic tank recycles 100 to 250% by volume of the total inflow volume of the inflow water first.

Next, the step of precipitating the effluent of the aerobic tank in the sedimentation tank. Precipitation treatment step is separated into sedimentation water and sludge from the sedimentation tank, the sedimentation treatment water is discharged to the denitrification tank of the post-process, the sludge is separated into the return sludge and waste sludge, return sludge flow into the anaerobic tank, waste sludge It is desirable to discard.

Next, the effluent of the settling tank is subjected to the second denitrification treatment in the denitrification tank. That is, in order to supplement the denitrification by the first denitrification step, the denitrification tank filled with the granular situation is once more denitrified to further improve the denitrification efficiency.

The inflow water flowing out of the settling tank into the denitrification tank is denitrified through the granular state filled in the denitrification tank and the reaction as in Scheme 1.

Scheme 1

^{_{1.06NO 3 - + 1.11S + 0.3HCO 3}} + 0.485H 2 O -> 0.5N 2 + 1.11SO 4 2- + 0.86H + + 0.06C 5 H 7 O 2 N

At this time, it is preferable that the granular state filled in the denitrification tank is configured to include 50 wt% or more of the spherical grain size having a maximum long diameter of 3 to 7 mm. That is, the granular state filled in the denitrification tank includes a spherical grain size of 3 to 7 mm in diameter of 50% by weight or more, so that an appropriate filtration rate can be secured and voids can be prevented due to microbial growth. .

Here, the spherical grain shape does not have to be a geometrically perfect sphere, but it means that it is a spherical shape rather than a plate or needle shape.

Moreover, it is preferable to improve the denitrification reaction efficiency of the granular situation filled in a denitrification tank by making the sulfur content of a spherical granular situation into 99 weight% or more. That is, when the sulfur content of the spherical grains is less than 99% by weight, the denitrification reaction efficiency is lowered, so that the sulfur content of the spherical grains is made 99% by weight or more, thereby reducing the amount of grains filled in the denitrification tank. .

Particularly, when the granular state filled in the denitrification tank contains 50 wt% or more of a spherical grain size of 3 to 7 mm or more in diameter, and the sulfur content of the spherical grains is 99 wt% or more, the spherical grain filled in the denitrification tank situation is filled with 800 ~ 1300 kg, based on the inflow quantity 10 m ³ / d coming from the settling tank, the residence time of the influent sulfur denitrification tank of from the settling tank is based on the inflow quantity that flows from the settling tank 10 m ³ / d By using 1 to 1.5 hours, it is possible to provide a sufficient amount of spherical particle situation and time to maximize the denitrification reaction efficiency of the influent water flowing from the sedimentation tank.

The present invention provides a sewage treatment method capable of improving the removal efficiency of phosphorus while removing nitrogen more efficiently in a biological sewage treatment method.

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

Figure 1 shows the overall process of the advanced sewage treatment method according to an embodiment of the present invention.

That is, the anaerobic tank 100, the anaerobic tank 200, the aerobic tank 300 and the degassing tank 350, the settling tank 400 and the denitrification tank (500), each of the reaction tank capacity and residence time flow inflow 18m ^The design was based on ³ / day, and the results are shown in Table 1.

division Capacity (m ³ ) Retention time (hr) Anaerobic tank 1.08 1.44 Anaerobic 2.92 3.89 Aerobic 4.17 5.56 Degassing tank 0.17 0.23 Sedimentation tank 3.75 5.00 Denitrification 1.84 2.45

In addition, the operating path of the treated water in the process of the first discharged through the anaerobic tank 100, the anaerobic tank 200, the aerobic tank 300, the sedimentation tank 400 and the denitrification tank 500 was finally discharged.

That is, the first inflow (A) is separated into the inflow (A-1) flowing into the anaerobic tank 100 and the inflow (A-2) directly flowing into the anaerobic tank 200 without passing through the anaerobic tank 100, respectively At this time, the inflow of the influent (A-2) flowing directly into the anaerobic tank 200 was adjusted to be 30 to 50% by volume of the total volume of the initial influent (A).

The effluent B treated in the anaerobic tank 100 was introduced into the anaerobic tank 200, and the effluent C treated in the anaerobic tank 200 was introduced into the aerobic tank 300. The outflow water D, which is processed in the aeration tank 300 and flows out through the degassing tank 350, is respectively an inflow water D-1 flowing into the settling tank 400 and an inflow water D-2 flowing into the anaerobic tank 200. At this time, the inflow of the influent (D-2) flowing into the anaerobic tank was adjusted to be 100 to 130% by volume of the total volume of the initial influent (A).

The sedimentation treatment water (E) treated from the sedimentation tank (400) was introduced into the denitrification tank (500), and the sludge (S) separated from the sedimentation tank (400) was conveyed sludge (S-1) and waste sludge (S2). The sludge S-1 was returned to the anaerobic tank 100, and the waste sludge S-2 was disposed of. At this time, the inflow flow rate of the return sludge (S-1) was adjusted to be 40 to 50% by volume relative to the total volume of the initial inflow water (A), and the waste sludge (S-2) was 1.11 to 2.5% of the initial inflow water. Was adjusted to

In addition, the entire treatment process path was installed to discharge the final discharged water F after the denitrification treatment of the inflow water E introduced from the settling tank 400 in the denitrification tank 500.

Through the treatment process route, the hydraulic residence time of the bioreactor consisting of the anaerobic tank 100, the anaerobic tank 200, the aerobic tank 300, and the degassing tank 350 was configured to be about 11.12 hours in total.

In addition, the anaerobic tank 100 includes anaerobic microorganisms which can release phosphoric acid by fermenting the organic material of the influent into a low molecular weight material.

The oxygen-free tank 200 includes a denitrification microorganism capable of converting nitric acid (NO ₃ ) into nitrogen (N ₂ ) gas using an organic material.

The aerobic tank 300 includes a 15% sponge-based fluidized bed microbial carrier 311 containing a dephosphorous microorganism group capable of incorporating phosphoric acid and a nitrification microorganism group capable of converting ammonia and the like into nitric acid, based on aerobic tank volume, and aerobic conditions. Air bubbles were injected from the bottom of the aerobic tank 300 to be. At this time, the material of the sponge-type fluidized bed microbial carrier is formed of polyurethane.

In the denitrification tank 500, the inflow water (E) is introduced from the sedimentation tank 400, which is composed of a sulfur content of 99 wt% or more and 80 wt% of a spherical grain of about 5 mm in diameter. ) Was filled up to 970 kg based on 10 m ³ / d. In addition, the time in which the inflow water E from the settling tank 400 stays in the denitrification tank was set to 1.5 hours based on the inflow amount of 10 m ³ / d introduced from the settling tank 400. In addition, the denitrification tank 500 has a residence time of 24 hours while blocking the inflow of the treated water from the anaerobic tank 100, the anaerobic tank 200, the aerobic tank 300 during the culture period of the autotrophic denitrification microorganisms. The microorganisms were acclimatized by supplying excess nitrate nitrogen while gradually decreasing to about 1 hour at, followed by denitrification by introducing the treated water from the bioreactor after a certain period of microorganism acclimation.

Other denitrification tank design factors are shown in Table 2 below.

Item value Inflow (m ^{3 /} day) 10 Reactor Volume (m ³ ) 0.92 Retention time (hr) 1.5 Volume load ^{_{(kg NO 3 -N / m 3}} · day) 0.28 Porosity (%) 36 Linear velocity (m / hr) 0.83 Backwash flow rate (m ³ / hr) 6

As an embodiment of the present invention as described above, the advanced sewage treatment apparatus was installed in G sewage treatment plant in Beijing, China, and operated for about four months from September 17, 2007 to January 19, 2008, and BOD ₅ ( Biological oxygen demand), COD _cr (chemical oxygen demand), SS (MLSS; suspended solids concentration: particulate matter above 0.45 micrometers in water), TN (total nitrogen content), NH ₃ -N (ammonia nitrogen), NO ₃ -N (nitric acid nitrogen), TP (total phosphorus), PO ₄ -P (phosphate) were measured using UV Spectrophotometer DR 2000 (HACH), and the measurement cycle was performed once a day. 2 to 9 are the same.

In the graphs of FIGS. 2 to 9, the measurement result of the first inflow water (A) is 'inflow water', and the measurement result of the sedimentation treatment water (E) is 'sedimentation treated water', and the final discharge water F, which is a denitrified water, is treated. The measurement results were expressed as 'desulfurization tank treated water'.

2 to 4, even in the BOD ₅ , COD _cr , SS (MLSS) in spite of the variation of the inflow (A), both the seed treatment and the denitrification tank treated water evenly and lower than about 50mg / L appear.

5 and 6, in the TN (total nitrogen amount) and TP (total phosphorus amount), despite the high inflow of nitrogen and phosphorus contained in the inflow water (A), both the needle treatment water and the denitrification tank treated water are denitrified and dephosphorized. Treatment results were obtained, and in particular, as can be seen from the TN (total nitrogen content) measurement results, it was about 15 to 20 mg / L (TN) for the seed treatment water, but about 5 to 10 mg / for denitrification tank treated water. It is indicated by L (TN), it can be seen that there was an excellent denitrification effect by the denitrification tank. In addition, in the TP (total phosphorus) measurement result, the total phosphorus content of the denitrification tank treated water was slightly lower than that of the seed treatment water, and the effect of dephosphorization was further increased by the effect of the denitrification tank. .

7 to 9 show the first inflow (A), the aeration tank treated water (B), anoxic tank treated water (C), aerobic tank treated water (D), sedimentation tank treated water (E) and denitrification tank treated water (F). For each of the COD _cr , NH ₃ -N (ammonia nitrogen), NO ₃ -N (nitric acid nitrogen), TP (total phosphorus amount), PO ₄ -P (phosphate phosphate) is measured and the average value is shown.

As shown in FIG. 7, the CDOcr was significantly lowered from the anaerobic treatment water (B), but gradually lowered through the subsequent step, and it can be seen that the minimum value is 16.9 mg / L in the denitrification tank treatment water.

As shown in FIG. 8, it can be seen that both ammonia nitrogen and nitrate nitrogen are denitrated in the denitrification tank treated water than the results of measurement of the aerobic treated water or the seed needle treated water which are the treatment result of the bioreactor. In particular, the inflow water (D-1) that is nitrified in the aerobic tank (300) and flows into the settling tank (500) includes a significant increase in nitrate nitrogen from the aerobic tank treated water (D), which is denitrated in a denitrification tank to the final effluent. By discharging to (F), there is an effect that can significantly reduce the amount of nitrogen in the discharged water (F).

In addition, as shown in Figure 9, the total phosphorus and phosphate phosphorus of the influent (A) is significantly increased in the anaerobic tank treated water (B), and greatly reduced while passing through the anaerobic tank (200), aerobic tank (300), denitrification tank (500) It can be seen that also slightly dephosphorized by).

Among the measurement results, the water quality analysis results and removal efficiencies of general items (BOD ₅ , COD _cr , SS, TN, and TP) are shown in Table 3.

Item Initial influent (A) reading (mg / L) Seed treatment Denitrification tank Measured value (mg / L) Processing efficiency (%) Measured value (mg / L) Processing efficiency (%) BOD ₅ 219.6 10.4 95.3 6.7 97.0 COD _cr 358.9 20.4 94.3 16.9 95.3 SS 161.8 8.1 95.0 7.0 95.5 T-N 53.2 15.9 70.1 6.1 88.6 T-P 5.4 1.9 64.8 1.6 69.9

That is, in BOD ₅ , COD _cr , and SS, the treatment efficiency of the seed treatment and the denitrification tank was similar, or the treatment efficiency of the denitrification tank was about 1 to 2% higher than the treatment efficiency of the seed treatment. In the denitrification treatment, it can be seen that the treatment efficiency of the denitrification tank treatment water is increased by about 18% from the treatment efficiency of the seed treatment water, and the denitrification effect is greatly improved by the denitrification tank. Also, in the dephosphorization efficiency, the treatment efficiency of the denitrification tank treated water increased by about 5% from the treatment efficiency of the seed treatment water, and it can be seen that the dephosphorization effect was also improved by the denitrification tank.

1 is an overall process treatment diagram of the advanced sewage treatment method according to an embodiment of the present invention.

2 to 9 show results of the implementation of one embodiment of the present invention BOD ₅ , COD _cr , SS (MLSS), TN (total nitrogen content), NH ₃ -N (ammonia nitrogen), NO ₃ -N (nitric acid nitrogen) , TP (Total Phosphorus), PO ₄ -P (Phosphate Phosphate), etc. are measured.

* Explanation of symbols on the main parts of the drawing

A: initial influent, A-1: anaerobic influent

A-2: Anaerobic Tank Influent Separated from Initial Influent

B: anaerobic tank treated water, C: anaerobic tank treated water

D: aerobic treatment water, D-1: sedimentation tank influent

D-2: anoxic tank influent separated from aerobic tank treated water

E: sedimentation tank treated water, F: denitrification tank treated water

S: Sedimentation Tank Sludge, S-1: Return Sludge

S-2: Waste Sludge

100: anaerobic tank, 200: anaerobic tank

300: aeration tank, 350: degassing tank

400: sedimentation tank, 500: denitrification tank

Claims (7)

Phosphorylating the influent in an anaerobic tank under anaerobic conditions; Firstly denitrifying the effluent of the anaerobic tank in an anaerobic tank; Dephosphorizing and nitrifying the effluent of the anaerobic tank in an aerobic tank; Precipitating the effluent of the aerobic tank in the settling tank; And performing a second denitrification treatment on the effluent of the second settling tank in a denitrification tank. The aerobic tank is filled with a sponge-type fluidized bed microbial carrier, The denitrification tank is an advanced sewage treatment method characterized in that the filling in the granular situation. 2. The advanced sewage treatment according to claim 1, wherein the granular state filled in the denitrification tank in the second denitrification treatment comprises at least 50 wt% of a spherical grain size of 3 to 7 mm in diameter. Way. The method of claim 2, wherein the spherical grains of the denitrification tank are made of sulfur of 99% or more. The method of claim 3, wherein the denitrification tank in the second denitrification step is filled with 800 ~ 1300 kg of the spherical grains on the basis of the inflow of water 10 m ³ / d flowing from the secondary sedimentation tank, The high sewage treatment method, characterized in that the residence time of the influent water from the secondary sedimentation tank in the denitrification tank is 1 to 1.5 hours based on the amount of inflow water 10 m ³ / d flowing from the secondary sedimentation tank. The method of claim 1, further comprising introducing a portion of the inflow into the anaerobic tank while introducing the inflow into the anaerobic tank, wherein a part of the inflow flowing into the anaerobic tank is 80% by volume or less of the total inflow volume. Advanced sewage treatment method, characterized in that. The method of claim 1, further comprising the step of introducing a portion of the effluent from the exhalation tank into the anoxic tank while introducing the effluent from the exhalation tank into the settling tank, wherein the part of the effluent from the aerobic tank flowing into the anoxic tank is firstly introduced. Advanced sewage treatment method, characterized in that 100 to 250% by volume of the total inflow of the influent. The method of claim 1, wherein the step of treating the sediment is separated into sedimentation treatment water and sludge from the sedimentation tank, the sedimentation treatment water is discharged into the denitrification tank, and the sludge is separated into a conveying sludge and waste sludge, Sludge is introduced into the anaerobic tank, the waste sludge is characterized in that the wastewater treatment method.

Images