AOO municipal sewage treatment method

Abstract

The invention relates to the technical field of sewage treatment, in particular to an AOO municipal sewage treatment method. According to the method, the municipal sewage is subjected to primary carbonization treatment, secondary carbonization treatment and nitrification treatment, so that the concentration of COD (Chemical Oxygen Demand) in effluent can be reduced to be below 50mg / L, ammonia nitrogen is controlled to be below 1mg / L, total nitrogen is controlled to be below 15mg / L, and the treatment requirements can be met; meanwhile, in the method, a high linear speed is adopted in the denitrification reactor, on one hand, no bubble enrichment exists in a filler layer, on the other hand, the treatment efficiency is greatly improved, the denitrification time can be controlled within 1 h, and through a subsequent natural oxygenation method, energy consumption caused by aeration of a traditional air blower is avoided, more energy is saved, and the method is suitable for large-scale popularization and application. Meanwhile, the secondary carbonization rate of COD and the nitrification rate of ammonia nitrogen are high, the whole treatment process is faster and more efficient, more energy is saved, the environment is better protected, and the method has extremely high research value and wide application and popularization prospects.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for treating municipal wastewater in AOO. Background Technology

[0002] Wastewater generated during production and daily life is generally purified and treated in wastewater treatment plants. Domestic sewage is usually treated in municipal wastewater treatment plants to achieve water resource recycling. Since domestic sewage contains COD, nitrate nitrogen, ammonia nitrogen, and phosphorus, existing treatment methods mostly use biological methods, such as anaerobic + anoxic + aerobic treatment processes. Through the activity of microorganisms, COD removal, ammonia nitrogen oxidation, nitrate nitrogen removal, and phosphorus solidification are achieved.

[0003] Existing methods for denitrification generally take a long time, which is not conducive to efficient wastewater treatment. At the same time, the wastewater after denitrification is usually nitrified by aeration and oxygenation, and the nitrified liquid is returned to the front end of the anoxic reaction to achieve denitrification. In this process, aeration requires a lot of energy, which is not conducive to resource conservation and environmental protection.

[0004] Therefore, this invention proposes an AOO municipal wastewater treatment method; by using a biofilm and a high linear velocity, the time required for the denitrification process is greatly shortened; and by using natural air oxygenation for carbonization and nitrification, the effluent quality meets the standards while effectively reducing energy consumption, making it more energy-efficient and environmentally friendly. It has extremely high research value and broad prospects for promotion and application. Summary of the Invention

[0005] The purpose of this invention is to provide an AOO municipal wastewater treatment method to solve the problem that existing wastewater treatment processes consume a lot of energy due to the use of blowers for aeration, which is not conducive to energy conservation and consumption reduction.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for treating municipal wastewater in AOO, comprising the following steps: S1. Perform anoxic carbonization reaction on the wastewater influent; The aforementioned anoxic carbonization reaction is a denitrification reaction. Through denitrification, the COD in the wastewater is carbonized and nitrate nitrogen is removed. S2. The wastewater after the anoxic carbonization reaction of S1 is subjected to an aerobic carbonization reaction. The aforementioned aerobic carbonization reaction is the further carbonization of COD and partial nitrification oxidation of ammonia nitrogen in wastewater after the anoxic carbonization reaction under natural oxygenation conditions. S3. Nitrification reaction is carried out on the wastewater after the aerobic carbonization reaction in S2. The nitrification reaction is the further nitrification and oxidation of residual ammonia nitrogen in the water body after the aerobic carbonization reaction under natural oxygenation conditions. S4. The wastewater after nitrification in S3 is partially used as effluent and partially recycled to the front end of the anoxic carbonization reaction, and mixed with the raw wastewater as the wastewater influent for the anoxic carbonization reaction.

[0007] Furthermore, in S1, the anoxic carbonization reaction is carried out in a denitrification reactor, which includes multiple denitrification reactor units connected in series, and the wastewater influent operates at high linear velocity in the denitrification reactor unit.

[0008] Furthermore, the denitrification reactor unit has a diameter of 800 mm and a height of 2000 mm; the linear velocity of the wastewater in the denitrification reactor unit is 5~8 m / h.

[0009] Furthermore, in S1, the COD concentration in the wastewater influent is 100-150 mg / L, the nitrate nitrogen concentration is 9-13 mg / L, and the ammonia nitrogen concentration is 7-11 mg / L; after the wastewater influent undergoes anoxic carbonization reaction, the COD concentration in the wastewater is 50-80 mg / L, and the nitrate nitrogen concentration is 1-3 mg / L.

[0010] Furthermore, in S2, the aerobic carbonization reaction is carried out in the carbonization reactor. After the anoxic carbonization reaction, the wastewater falls into the carbonization reactor from above in the form of thin lines or beads, and is fully in contact with the air during the falling process; there is no water accumulation in the carbonization reactor.

[0011] Furthermore, after the aerobic carbonization reaction, the COD concentration in the wastewater is 30-40 mg / L, and the ammonia nitrogen concentration is 3-7 mg / L.

[0012] Furthermore, in S3, the nitrification reaction is carried out in a nitrification reactor. After the aerobic carbonization reaction, the wastewater falls into the nitrification reactor from above in a thin line or bead-like shape, and is fully in contact with the air during the falling process; there is no water accumulation in the nitrification reactor.

[0013] Furthermore, after the nitrification reaction, the COD concentration in the wastewater is 30~35 mg / L, and the ammonia nitrogen concentration is 0.1~1 mg / L.

[0014] Furthermore, in S4, the wastewater after nitrification is partially returned to the front end of the nitrification reaction, and the ratio of the amount returned to the front end of the nitrification reaction to the original wastewater is 50-100%; the ratio of the amount returned to the front end of the anoxic carbonization reaction to the original wastewater is 200-400%.

[0015] The beneficial effects of this invention are: 1. This invention uses a biofilm method for denitrification, and controls a relatively large linear velocity during the process. On the one hand, this will not cause the accumulation of bubbles in the packing layer, and on the other hand, it can greatly reduce the time consumption of denitrification, which helps to improve the treatment efficiency. 2. This invention avoids the traditional aeration-enriched nitrification method and adopts a natural air oxygenation method of carbonization + nitrification. This not only reduces energy consumption but also effectively ensures the quality of the effluent and has a fast treatment speed, further improving treatment efficiency. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the method of the present invention.

[0017] The names corresponding to each mark in the diagram: 1. Mixing tank; 2. Denitrification reactor; 21. Exhaust pipe; 3. Carbonization reactor; 4. Nitrification reactor. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0019] like Figure 1 As shown, in the process of this invention, the raw water inlet and the reflux nitrified liquid in the effluent tank of the nitrification reactor are mixed in the mixing tank 1 and then introduced into the denitrification reactor 2.

[0020] The denitrification reactor 2 includes multiple denitrification reactor units connected in series. In one embodiment of the present invention, it includes four denitrification reactor units, and is configured with three in use and one in standby by controlling the valves on the corresponding pipelines. An exhaust pipe is provided above each denitrification reactor 2 (although the bubbles generated by denitrification are carried out and do not accumulate in the packing layer, a small amount of gas will accumulate inside the upper part of the denitrification reactor unit, which needs to be vented periodically or in a timely manner).

[0021] A carbonization reactor 3 is installed at the rear end of the denitrification reactor 2. The effluent from the denitrification reactor 2 is sprayed into the carbonization reactor 3. The effluent from the carbonization reactor 3 and the effluent tank of the carbonization reactor are pumped to the top of the nitrification reactor 4, and then sprayed into the nitrification reactor 4. The effluent from the nitrification reactor 4 is discharged (after downstream chemical phosphorus removal), with part of the effluent flowing back to the mixing tank 1 and part flowing back to the top of the nitrification reactor 4. The carbonization reactor 3 or the nitrification reactor 4 can be set in multiple stages at intervals. The effluent from the upper stage flows into the next stage in a thin line or beaded manner. There is no liquid accumulation in the carbonization reactor 3 or the nitrification reactor 4, that is, water storage is avoided and obvious liquid level layers are avoided. The carbonization reactor 3 or the nitrification reactor 4 can be set up with one standby reactor.

[0022] A flushing pipe (not shown in the figure) is installed above the denitrification reactor 2, carbonization reactor 3 and nitrification reactor 4 to flush the internal packing. Correspondingly, an emptying pipe (not shown in the figure) is installed at the bottom of the effluent tanks of the denitrification reactor 2, carbonization reactor and nitrification reactor.

[0023] Example 1 In this embodiment, effluent from the anaerobic tank of a wastewater treatment plant was taken. After testing, the ammonia nitrogen in the effluent was about 40 mg / L. An appropriate amount of carbon source was added to control the COD to about 400 mg / L, which basically simulated the influent conditions of a real biological anoxic tank. This water sample was used as the raw wastewater in this embodiment.

[0024] The raw wastewater is fed into the denitrification reactor of this invention. In this embodiment, the denitrification reactor includes four denitrification reactor units connected in series, with three in use and one as a backup. In this embodiment, each denitrification reactor unit has a diameter of 800 mm and a height of 2000 mm, and is filled with packing material. Volcanic rock packing material (commercially available) with a particle size of 6-8 mm is used. The volcanic rock packing material is soaked in the effluent tank of the secondary sedimentation tank for one week and then filled into the denitrification reactor after forming a biofilm. The filling height is about 1700 mm, and the porosity of the packing layer is controlled at 30-35%. A supporting sieve plate is set below the packing layer, and a packing pressure plate with sieve holes is set above the packing layer.

[0025] In the initial stage of the reaction, the effluent from the anaerobic tank was diluted and supplemented with nitrate nitrogen before being fed into the denitrification reactor. During the process, the concentration of COD in the influent to the denitrification reactor was controlled at 100~150 mg / L, the concentration of ammonia nitrogen at 9~13 mg / L, and the concentration of nitrate nitrogen at 7~11 mg / L. After the system was running stably, part of the effluent after nitrification was returned to the front end of the denitrification reactor. The return ratio (the ratio of return flow rate to raw influent) was controlled at 200~400%. The return ratio was adjusted to control the ammonia nitrogen concentration in the wastewater influent to generally not exceed 13 mg / L. The influent flow rate to the denitrification reactor was controlled so that the linear velocity of the water flow in the denitrification reactor was 5~8 m / h. Due to the high linear velocity of the water flow, the gas generated by denitrification could be carried out in time. During the experiment, no bubble accumulation was observed in the packing layer, and the system was running stably.

[0026] During the experiment, the denitrification process was completed in approximately 45 minutes, demonstrating high treatment efficiency. Furthermore, after the system stabilized, the raw water flow rate to the denitrification reactor was controlled at 0.3 m³ / min. 3 The nitrification effluent recirculation ratio was 300% per hour. Sampling and monitoring of the denitrification process were conducted, and the data are recorded below: Table 1. Statistical Table of Denitrification Process Data

[0027] It can be seen that the denitrification process can achieve partial carbonization of COD and removal of nitrate nitrogen. The COD removal rate can reach 40%, and the nitrate nitrogen removal rate can reach 70%, which can meet the requirements of denitrification effluent in actual engineering.

[0028] The denitrification effluent undergoes secondary carbonization treatment in the carbonization reactor of this invention. In this embodiment, the carbonization reactor is cylindrical, with a diameter of 1000 mm and a height of 600 mm. The bottom is a sieve plate with 3 mm aperture holes, arranged vertically with a spacing of 500 mm between the two sieves. Carbonization packing material is filled into the carbonization reactor. In this embodiment, the carbonization packing material is commercially available biological ceramic granules with a particle size of 6-8 mm. The packing material is soaked in the secondary sedimentation tank effluent for one week to allow biofilm formation before being filled into the carbonization reactor. After the system stabilizes, the carbonization process is sampled and monitored, and the data is recorded as follows: Table 2. Statistical Table of Carbonization Process Data

[0029] It can be seen that during the carbonization reaction process, COD in the water can be further removed, and some ammonia nitrogen is oxidized accordingly. The COD removal rate is about 50%, and the ammonia nitrogen removal rate is about 40%, resulting in an effluent COD of about 30 mg / L. Experimental studies have shown that when the COD concentration reaches about 30 mg / L, the COD carbonization reaction basically stops due to the low COD concentration. It should be noted that a small amount of sludge will be produced in the carbonization reactor in this embodiment. The packing layer should be flushed regularly to avoid clogging.

[0030] Therefore, the effluent from the aerobic carbonization reaction is further oxidized to achieve nitrification of ammonia nitrogen. The nitrification reactor is arranged in the same way as the carbonization reactor described above. During the operation of the nitrification reactor, a portion of the nitrated liquid is recycled back to the front end of the reactor. The recycling rate of this portion of the nitrated liquid is 100% (the ratio of the recycling flow rate to the influent flow rate) to ensure the effectiveness of the nitrification reaction. The nitrification process is sampled and monitored, and the data is recorded as follows:

[0031] It can be seen that as the COD concentration in the water decreases, the COD carbonization reaction basically stops, and the natural oxygenation in the water is mainly used for the oxidation of ammonia nitrogen. During the process, the ammonia nitrogen in the effluent can be controlled below 1 mg / L, which can fully meet the effluent water quality requirements. At the same time, in the experimental operation, the carbonization and nitrification reactions are short, and the contact time between the wastewater and the carbonization reactor or nitrification reactor is only 20~40 seconds, which can greatly improve the efficiency of wastewater treatment. It has extremely high research value and broad prospects for promotion and application.

[0032] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for treating municipal wastewater in AOO, characterized in that, Includes the following steps: S1. Perform anoxic carbonization reaction on the wastewater influent; The aforementioned anoxic carbonization reaction is a denitrification reaction. Through denitrification, the COD in the wastewater is carbonized and nitrate nitrogen is removed. S2. The wastewater after the anoxic carbonization reaction of S1 is subjected to an aerobic carbonization reaction. The aforementioned aerobic carbonization reaction is the further carbonization of COD and partial nitrification oxidation of ammonia nitrogen in wastewater after the anoxic carbonization reaction under natural oxygenation conditions. S3. Nitrification reaction is carried out on the wastewater after the aerobic carbonization reaction in S2. The nitrification reaction is the further nitrification and oxidation of residual ammonia nitrogen in the water body after the aerobic carbonization reaction under natural oxygenation conditions. S4. The wastewater after nitrification in S3 is partially used as effluent and partially recycled to the front end of the anoxic carbonization reaction, and mixed with the raw wastewater as the wastewater influent for the anoxic carbonization reaction.

2. The AOO municipal wastewater treatment method according to claim 1, characterized in that: In S1, the anoxic carbonization reaction takes place in a denitrification reactor, which includes multiple denitrification reactor units connected in series. The wastewater influent operates at high linear velocity in the denitrification reactor unit.

3. The AOO municipal wastewater treatment method according to claim 2, characterized in that: The denitrification reactor unit has a diameter of 800 mm and a height of 2000 mm; the linear velocity of the wastewater in the denitrification reactor unit is 5~8 m / h.

4. The AOO municipal wastewater treatment method according to claim 1, characterized in that: In S1, the COD concentration in the wastewater influent is 100-150 mg / L, the nitrate nitrogen concentration is 9-13 mg / L, and the ammonia nitrogen concentration is 7-11 mg / L; after the wastewater influent undergoes anoxic carbonization reaction, the COD concentration in the wastewater is 50-80 mg / L, and the nitrate nitrogen concentration is 1-3 mg / L.

5. The AOO municipal wastewater treatment method according to claim 4, characterized in that: In S2, the aerobic carbonization reaction is carried out in the carbonization reactor. After the anoxic carbonization reaction, the wastewater falls into the carbonization reactor from above in the form of thin lines or beads, and is in full contact with the air during the falling process; there is no water accumulation in the carbonization reactor.

6. The AOO municipal wastewater treatment method according to claim 5, characterized in that: After the aerobic carbonization reaction, the COD concentration in the wastewater is 30-40 mg / L, and the ammonia nitrogen concentration is 3-7 mg / L.

7. A method for treating municipal wastewater in AOO as described in claim 6, characterized in that: In S3, the nitrification reaction takes place in a nitrification reactor. After the aerobic carbonization reaction, the wastewater falls into the nitrification reactor from above in a thin line or bead-like shape, and is fully in contact with the air during the falling process; there is no water accumulation in the nitrification reactor.

8. The AOO municipal wastewater treatment method according to claim 7, characterized in that: After the nitrification reaction, the COD concentration in the wastewater is 30~35 mg / L, and the ammonia nitrogen concentration is 0.1~1 mg / L.

9. A method for treating municipal wastewater in AOO according to claim 1, characterized in that: In S4, the wastewater after nitrification is partially returned to the front end of the nitrification reaction, and the ratio of the amount returned to the front end of the nitrification reaction to the original wastewater is 50-100%; the ratio of the amount returned to the front end of the anoxic carbonization reaction to the original wastewater is 200-400%.

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