AOAO Bioreactor with Sludge Double-Reflux for Nitrogen Removal
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Solution Overview
Problem
Domestic sewage treatment faces challenges in simultaneous nitrogen and phosphorus removal due to low C/N water quality, requiring efficient biological methods that conserve carbon sources and maintain effective nitrogen removal rates.
Innovation Solution
The AOAO process with sludge double-reflux in an anaerobic/aerobic/anoxic/aerobic bioreactor system utilizes partial denitrification and anammox reactions, enhanced by anammox fillers and denitrifying phosphate accumulating bacteria, to provide a nitrite substrate and internal carbon sources for nitrogen removal, while minimizing carbon source consumption and promoting phosphorus removal through anaerobic phosphate release and aerobic uptake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional biological nitrogen removal methods are used, then nitrogen removal can be achieved, but carbon source consumption increases and processing efficiency decreases
Solution Approach 1:
The patent changes the nitrogen removal pathway by shifting from traditional nitrification-denitrification to anammox process, utilizing ammonia and nitrite as substrates instead of organic carbon and nitrate, thereby fundamentally altering the chemical parameters of the removal reaction to eliminate external carbon source requirements
Solution Approach 2:
The system uses internally stored carbon sources (poly-β-hydroxybutyrate or PHB) accumulated during anaerobic phases to support denitrification, eliminating the need for external carbon source addition. The bacteria serve themselves by utilizing their own stored reserves
2Reliability
If simultaneous nitrogen and phosphorus removal is implemented, then effluent quality improves, but system complexity increases due to low C/N water quality constraints
Solution Approach 1:
The patent combines nitrogen removal (via anammox and denitrification) and phosphorus removal (via enhanced biological phosphorus removal) into a single integrated AOAO bioreactor system, achieving simultaneous removal of both nutrients through coordinated bacterial communities and process design
Solution Approach 2:
The bioreactor is divided into distinct functional zones (anaerobic, anoxic, aerobic sections) with specific hydraulic retention times and operational parameters optimized for different bacterial processes, allowing simultaneous nitrogen and phosphorus removal through spatial segmentation of reactions
3Productivity
If external carbon sources are added for denitrification, then nitrogen removal efficiency improves, but operational costs increase
Solution Approach 1:
The system accumulates and utilizes internally stored carbon sources (PHB) during anaerobic phases to fuel denitrification during anoxic phases, making the process self-sufficient and eliminating continuous external carbon source addition and associated operational costs
Solution Approach 2:
The patent optimizes hydraulic retention times (anaerobic: 2-4h, anoxic: 5-7h, aerobic: 3-4h) and dissolved oxygen concentrations (2-4mg/L) to maximize internal carbon source accumulation and utilization efficiency, thereby maintaining high nitrogen removal rates without external carbon addition
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves advanced nitrogen and phosphorus removal from domestic sewage, increasing processing load and reducing external carbon source needs, with efficient nitrogen conversion rates and stable nitrification performance, meeting discharge standards with reduced operational costs.
Implementation Method 1
The anammox (anaerobic ammonium oxidation) is a reaction in which anammox bacteria use ammonia-nitrogen as an electron donor to reduce nitrite-nitrogen to nitrogen under anoxic conditions
Implementation Method 2
Endogenous denitrification refers to a process in which heterotrophic denitrifying bacteria use endogenous substances stored in the body as electron donors to reduce nitrate-nitrogen or nitrite-nitrogen to nitrogen
Implementation Method 3
Denitrifying dephosphatation is a process in which the use of denitrifying phosphate accumulating bacteria to release phosphate in an anaerobic environment while volatile fatty acids (VFA) in the domestic sewage is absorbed into the cell to synthesize intracellular carbon sources (PHAs)
Data Source
AI summary
A method for advanced nitrogen and phosphorus removal of domestic sewage based on DEAMOX in AOAO process with sludge double-reflux is disclosed. The method comprises allowing domestic sewage and returned sludge of the secondary sedimentation tank (3) to enter the anaerobic zone (2.1) of the AOAO reactor (2), firstly performing partial denitrification by the denitrifying bacteria, reducing nitrate-nitrogen in the returned sludge to nitrite-nitrogen, then converting ammonia-nitrogen and nitrite-nitrogen into nitrogen by anammox bacteria, and phosphate accumulating bacteria and denitrifying phosphate accumulating organisms performing anaerobic phosphate release and storing internal carbon source; then allowing part of the mixed liquid to enter the intermediate aerobic zone (2.2) of the AOAO bioreactor (2) to carry out phosphate uptake and nitrification reaction, allowing another part of the mixed liquid to enter the anoxic zone (2.3) of the AOAO bioreactor (2), at same time allowing all the mixed liquid of the intermediate aerobic zone (2.2) and part of returned sludge of the secondary sedimentation tank (3) to enter the anoxic zone (2.3), using the internal carbon source stored in the anaerobic compartment and the internal carbon source in the returned sludge to carry out partial denitrification, anammox, denitrifying dephosphatation, and then allowing the mixed liquid to enter the post aerobic zone (2.4) and subsequently enter the secondary sedimentation tank (3) for mud-water separation. An apparatus for advanced nitrogen and phosphorus removal of domestic sewage based on DEAMOX in AOAO process with sludge double-reflux is also disclosed.