Method and apparatus for treating municipal sewage by AOA process via endogenous partial denitrification coupled with anammox in anoxic zone

Patent metadata

Field	Value
Publication number	US-11319230-B2
Application number	US-202017041365-A
Country	US
Kind code	B2
Filing date	Apr 2, 2020
Priority date	Apr 30, 2019
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

An apparatus for treating municipal sewage by anaerobic/aerobic/anoxic (AOA) [1] process via simultaneous endogenous partial [2] denitrification coupled with anammox in anoxic zone is disclosed. The apparatus mainly includes a raw water tank (1) for sewage, an AOA reactor (2) and a sedimentation tank (3), the sludge flows back from the bottom of the sedimentation tank (3) to the anoxic zone (2.4) and the anaerobic zone (2.2) respectively, and biofilm filler is added to the anoxic zone (2.4). The sewage enters the AOA reactor (2), and the intracellular carbon source is stored in the anaerobic zone (2.2) to remove the organic matter in the raw water. Then it enters the aerobic zone (2.3) for nitrification, and the generated nitrate-nitrogen enters the anoxic zone (2.4) for endogenous partial denitrification. The filler in the anoxic zone (2.4) uses the generated nitrite-nitrogen by endogenous partial denitrification and the remaining ammonia-nitrogen in the raw water to perform anammox reaction. The generated nitrate-nitrogen can be further removed by endogenous denitrification in the anoxic zone (2.4). Endogenous partial denitrification coupled with anammox is used for nitrogen removal in the anoxic zone (2.4), which can reduce the requirement of aeration in the aerobic zone (2.3) and the carbon sources in the anoxic zone (2.4), and suitable for low C/N ratio municipal sewage treatment. A method for treating municipal sewage by AOA process via endogenous partial denitrification coupled with anammox in anoxic zone is also provided.

First claim

The invention claimed is:

1. A method for treating municipal sewage, the method comprising:
1) obtaining an apparatus that is configured to treat the municipal sewage by an anaerobic/aerobic/anoxic (AOA) process via endogenous partial denitrification coupled with anaerobic ammonium oxidation in an anoxic zone,
wherein the apparatus comprises a raw water tank for sewage, an AOA reactor and a sedimentation tank which are sequentially connected; wherein the raw water tank for sewage is equipped with an overflow pipe and a blow-down pipe; the raw water tank for sewage is connected to the AOA reactor through an intake pump; the AOA reactor includes eight compartments and is divided into an anaerobic zone, an aerobic zone and the anoxic zone according to a direction of water flow, each of the eight compartments has an equal volume, and is equipped with connecting holes cross-connected up and down according to the direction of water flow; the anaerobic zone is equipped with an agitator; the aerobic zone is equipped with an air pump, an aerator, a gas flowmeter; the anoxic zone is equipped with an agitator, a filler frame; sludge at the bottom of the sedimentation tank is transferred to the anaerobic zone through a first sludge reflux pump to form a first sludge reflux, transferred to the anoxic zone through a second sludge reflux pump to form a second sludge reflux, and finally discharged through a drainage pipe;
2) utilizing the apparatus to perform a start-up stage of nitrification and endogenous denitrification,
wherein floc sludge is inoculated with nitrification and denitrification sludge, and a filler is anammox filler; wherein a reflux ratio R 1 of the first sludge reflux to a first compartment of the anaerobic zone is equal to 100%, and a reflux ratio R 2 of the second sludge reflux to a first compartment of the anoxic zone is equal to 100%; during the start-up stage of nitrification and endogenous denitrification, the eight compartments are two anaerobic compartments, three aerobic compartments and three anoxic compartments; mixed liquid suspended solids (MLSS) in the anaerobic zone and aerobic zone is maintained at 3000-4000 mg/L and the MLSS in the anoxic zone is maintained at 4000-5000 mg/L; dissolved oxygen in the aerobic zone is controlled to 1-2 mg/L; C/N ratio is controlled to be greater than 4 by adding an external carbon source; and hydraulic retention time is 16 h; if an intracellular carbon source storage rate reaches 90% or above in a last compartment of the anaerobic zone, total nitrogen in an effluent from the drainage pipe is less than 15 mg/L, which are maintained stably for more than 5 days, the nitrification and endogenous denitrification stage is considered to be successfully started;
3) utilizing the apparatus to perform a start-up stage of endogenous partial denitrification coupled with anammox,
wherein during start-up stage of endogenous partial denitrification coupled with anammox, an anammox filler frame is added to the anoxic zone; ammonia-nitrogen in an effluent from the aerobic zone is controlled by adjusting a volume of the aerobic zone; if NH 4 + —N concentration in a last compartment of the aerobic zone is less than or equal to 5 mg/L, the last compartment of the aerobic zone is changed into an anoxic compartment by removing the aerator and adding a stirring device; if NH 4 + —N concentration in the last compartment of the aerobic zone is more than or equal to 10 mg/L, the first compartment of the anoxic zone is changed to an aerobic compartment; if NH 4 + —N concentration in the last compartment of the aerobic zone is in a range of 5 mg/L to 10 mg/L, the eight compartments are maintained as two anaerobic compartments, two aerobic compartments and four anoxic compartments; in this stage, the MLSS in the anaerobic zone and aerobic zone is maintained at 3000-4000 mg/L and the MLSS in the anoxic zone is maintained at 4000-5000 mg/L; dissolved oxygen in the aerobic zone is controlled to 1-2 mg/L; a reflux ratio of the first and second sludge reflux is 100% respectively, and hydraulic retention time is 16 h; if total nitrogen removal reaches more than 50% by the anammox in the anoxic zone, which is maintained stably for more than 10 days, the endogenous partial denitrification coupled with anammox stage is considered to be successfully started; and
4) utilizing the apparatus to perform a long-term operation stage,
wherein in a long-term operation, the eight compartments are two anaerobic compartments, two aerobic compartments and four anoxic compartments; the hydraulic retention time is adjusted according to a total nitrogen concentration in the effluent: if the total nitrogen concentration in the effluent is less than or equal to 5 mg/L, the hydraulic retention time is reduced by 2 h, if the total nitrogen concentration in the effluent is more than or equal to 15 mg/L, the hydraulic retention time is extended by 2 h, if the total nitrogen concentration in the effluent is in a range from 5 mg/L to 15 mg/L, the hydraulic retention time is maintained at 16 h; the floc MLSS is 3000-4000 mg/L in the anaerobic zone and aerobic zone and 4000-5000 mg/L in the anoxic zone; and dissolved oxygen in the aerobic zone is controlled to 1-2 mg/L.

Assignees

• Univ Beijing Technology

Inventors

• Peng Yongzhen
• Gao Xinjie
• Xu Zaizhou
• Li Xiyao
• Zhang Qiong

Classifications

• C02F2301/046

  Recirculation with an external loop · CPC title

• C02F2209/16

  Total nitrogen (tkN-N) · CPC title

• C02F2203/006

  details of construction, e.g. specially adapted seals, modules, connections · CPC title

• C02F2209/14

  NH3-N · CPC title

• C02F3/307 Primary

  characterised by direct conversion of nitrite to molecular nitrogen, e.g. by using the Anammox process · CPC title