Method for improving denitrification efficiency of A/O sewage treatment system under low carbon-nitrogen ratio condition

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a method for improving denitrification efficiency of an A / O sewage treatment system under a low C / N ratio water inlet condition. According to the scheme, when the carbon-nitrogen ratio in inlet water is low, an existing running A / O system is adjusted as follows: raw water is added into an aerobic reactor,that is, a part of the raw water exceeds an anoxic reactor and directly enters the aerobic reactor; wherein the average concentration of the organic matters entering the aerobic reactor is not higherthan 70mg / L*d; increasing the sludge reflux quantity of the secondary sedimentation tank, enabling a part of sludge to directly flow back into the aerobic reactor, and keeping the concentration of thesludge in the aerobic tank to reach 7000-12000 mg / L, wherein the proportion of the amount of sludge returned from the secondary sedimentation tank to the anaerobic tank to the aerobic tank is 0.5-2.5. According to the invention, the effluent quality of the existing sewage treatment process can be integrally improved, particularly the concentration of total nitrogen in effluent is reduced, and thesludge yield is reduced. The scheme provided by the invention is simple to operate and low in modification treatment cost, and can be used for upgrading and modifying the existing sewage treatment system.

Description

Technical field

[0001] The invention belongs to the technical field of water treatment, and specifically relates to an optimization method for biological sewage treatment, and in particular to a method for improving the denitrification efficiency of an A / O sewage treatment system under low C / N ratio inflow conditions. Background technique

[0002] With the development of the social economy and the improvement of living standards, urban domestic water consumption has increased rapidly, and the discharge of nitrogen-containing organic matter has increased, resulting in an increase in the nitrogen content of sewage, that is, a decrease in the carbon to nitrogen (C / N) ratio. Sewage treatment plants operating in accordance with the original design water quality are difficult to adapt to the continuously decreasing C / N ratio in the sewage, resulting in the discharge of ammonia nitrogen or total nitrogen in the effluent water. Therefore, low C / N ratio sewage treatment has become one of ...

Examples

Embodiment 1

[0079] Example 1. A sewage treatment plant adopts the A / O process with a daily processing capacity of 2 tons / day. The hydraulic retention time of A / O is 4h and 12h respectively. The weekly average influent COD is 150mg / L and ammonia nitrogen is 28.0 mg / L, total nitrogen TN is 35.0mg / L. The average weekly effluent COD is 15mg / L, ammonia nitrogen is 2.2mg / L, total nitrogen TN is 12.80mg / L. 20L / h of influent sewage directly enters the aerobic aeration tank to increase the sludge return flow of the secondary settling tank, and the ratio of the return sludge of the secondary settling tank into the anaerobic tank and the aerobic tank is 1.0. Adjust the sludge concentration in the aeration tank from 3700mg / L to 11200mg / L, without changing the aeration volume in the aeration tank, and control the dissolved oxygen at 2.5-4.60mg / L. After the system runs stably, the weekly average effluent COD is 12mg / L, ammonia nitrogen is 0.22mg / L, total nitrogen TN is 7.6mg / L, total phosphorus is 0.20...

Embodiment 2

[0080] Example 2. A sewage treatment plant adopts the A / O process with a daily processing capacity of 60,000 tons / day. The hydraulic retention time of A / O is 4h and 9h respectively. The weekly average influent COD is 205.1mg / L, and the ammonia nitrogen is 24.88mg / L, total nitrogen TN is 32.50mg / L, total phosphorus 3.45mg / L. The average weekly effluent COD was 35mg / L, ammonia nitrogen was 0.69mg / L, total nitrogen TN was 14.50mg / L, total phosphorus was 0.49mg / L. The above process is adjusted, and 700 tons / hour of influent sewage directly enters the aerobic aeration tank (1800 tons / hour still enters the anaerobic reactor from the front end), and increases the sludge return flow in the secondary settling tank. The ratio of the return sludge into the anaerobic tank and the aerobic tank in the secondary settling tank is 0.8. The sludge concentration in the aeration tank is adjusted from 3700mg / L to 8800mg / L without changing the aeration volume in the aeration tank. The internal MLSS...

Technical field

[0001] The invention belongs to the technical field of water treatment, and specifically relates to an optimization method for biological sewage treatment, and in particular to a method for improving the denitrification efficiency of an A / O sewage treatment system under low C / N ratio inflow conditions. Background technique

[0002] With the development of the social economy and the improvement of living standards, urban domestic water consumption has increased rapidly, and the discharge of nitrogen-containing organic matter has increased, resulting in an increase in the nitrogen content of sewage, that is, a decrease in the carbon to nitrogen (C / N) ratio. Sewage treatment plants operating in accordance with the original design water quality are difficult to adapt to the continuously decreasing C / N ratio in the sewage, resulting in the discharge of ammonia nitrogen or total nitrogen in the effluent water. Therefore, low C / N ratio sewage treatment has become one of ...

Examples

Embodiment 1

[0079] Example 1. A sewage treatment plant adopts the A / O process with a daily processing capacity of 2 tons / day. The hydraulic retention time of A / O is 4h and 12h respectively. The weekly average influent COD is 150mg / L and ammonia nitrogen is 28.0 mg / L, total nitrogen TN is 35.0mg / L. The average weekly effluent COD is 15mg / L, ammonia nitrogen is 2.2mg / L, total nitrogen TN is 12.80mg / L. 20L / h of influent sewage directly enters the aerobic aeration tank to increase the sludge return flow of the secondary settling tank, and the ratio of the return sludge of the secondary settling tank into the anaerobic tank and the aerobic tank is 1.0. Adjust the sludge concentration in the aeration tank from 3700mg / L to 11200mg / L, without changing the aeration volume in the aeration tank, and control the dissolved oxygen at 2.5-4.60mg / L. After the system runs stably, the weekly average effluent COD is 12mg / L, ammonia nitrogen is 0.22mg / L, total nitrogen TN is 7.6mg / L, total phosphorus is 0.20...

Embodiment 2

[0080] Example 2. A sewage treatment plant adopts the A / O process with a daily processing capacity of 60,000 tons / day. The hydraulic retention time of A / O is 4h and 9h respectively. The weekly average influent COD is 205.1mg / L, and the ammonia nitrogen is 24.88mg / L, total nitrogen TN is 32.50mg / L, total phosphorus 3.45mg / L. The average weekly effluent COD was 35mg / L, ammonia nitrogen was 0.69mg / L, total nitrogen TN was 14.50mg / L, total phosphorus was 0.49mg / L. The above process is adjusted, and 700 tons / hour of influent sewage directly enters the aerobic aeration tank (1800 tons / hour still enters the anaerobic reactor from the front end), and increases the sludge return flow in the secondary settling tank. The ratio of the return sludge into the anaerobic tank and the aerobic tank in the secondary settling tank is 0.8. The sludge concentration in the aeration tank is adjusted from 3700mg / L to 8800mg / L without changing the aeration volume in the aeration tank. The internal MLSS...

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