Pre-denitrification Zone for Nitrate Removal in Sewage Treatment
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Solution Overview
Problem
Traditional sewage treatment processes face challenges in efficiently removing nitrogen and phosphorus due to low carbon source concentrations, which interfere with biological phosphorus removal and hinder simultaneous high-efficiency nitrogen and phosphorus removal.
Innovation Solution
A method involving a pre-denitrification zone, an anoxic zone, an aerobic zone, and a biological filtration zone with specific fillers, along with step feed and chemical phosphorus removal processes, is implemented to reduce nitrate nitrogen interference and enhance phosphorus and nitrogen removal efficiency, even at low C/N and C/P ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional A2O process is used for nitrogen and phosphorus removal, then both nitrogen and phosphorus can be removed, but nitrate nitrogen in return sludge interferes with biological phosphorus removal and reduces removal efficiency
Solution Approach 1:
The treatment process is segmented into distinct functional zones: pre-denitrification zone, anaerobic zone, anoxic zone, and aerobic zone. Each zone performs a specific function, with the pre-denitrification zone specifically targeting nitrate nitrogen removal before the mixed liquor enters the anaerobic zone for phosphorus removal, thereby preventing nitrate nitrogen interference with PAO activity.
Solution Approach 2:
The pre-denitrification zone performs preliminary denitrification of nitrate nitrogen in the return sludge before the mixed liquor enters the anaerobic zone. This preliminary action removes the harmful nitrate nitrogen interference before it can affect phosphorus removal processes in subsequent zones.
2Productivity
If carbon source concentration is low in domestic sewage, then energy consumption is reduced, but nitrogen and phosphorus removal efficiency decreases
Solution Approach 1:
The pre-denitrification zone performs preliminary denitrification using available carbon sources in the raw water and return sludge, consuming nitrate nitrogen before the mixed liquor enters the anaerobic zone. This allows the system to achieve high nitrogen removal efficiency without requiring high carbon source concentrations in the subsequent phosphorus removal zone.
Solution Approach 2:
By segmenting the process into pre-denitrification and anaerobic zones, the system can optimize carbon source utilization in each zone separately. The pre-denitrification zone uses carbon sources for nitrate removal, while the anaerobic zone focuses on phosphorus removal, improving overall efficiency without requiring high carbon concentrations throughout the entire process.
3Reliability
If nitrate nitrogen is used as electron acceptor for denitrification by PAOs, then nitrogen removal is achieved, but phosphorus release and uptake processes are negatively affected
Solution Approach 1:
The process is segmented to separate nitrate nitrogen denitrification from phosphorus removal processes. The pre-denitrification zone handles nitrate nitrogen removal using carbon sources, while the anaerobic zone focuses on phosphorus release and uptake by PAOs without nitrate nitrogen interference, ensuring both functions operate optimally.
Solution Approach 2:
The pre-denitrification zone performs preliminary removal of nitrate nitrogen from the return sludge before the mixed liquor enters the anaerobic zone. This preliminary action prevents nitrate nitrogen from being used as an electron acceptor by PAOs, thereby maintaining proper phosphorus release and uptake processes.
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 method effectively improves phosphorus and nitrogen removal efficiencies, reduces chemical oxygen demand, and achieves advanced nitrogen removal by avoiding nitrate nitrogen interference, with total phosphorus removal rates reaching 90% and total nitrogen removal rates approaching 80%, while maintaining low effluent CODcr, ammonia nitrogen, and suspended solid levels.
Implementation Method 1
allowing sludge returned from a sedimentation zone to enter the pre-denitrification zone to undergo denitrification
Implementation Method 2
allowing a sludge-containing mixed liquor obtained after the denitrification in the pre-denitrification zone to enter the anaerobic zone to undergo a biological phosphorus removal reaction
Implementation Method 3
allowing a sludge-containing mixed liquor obtained after the denitrification in the anoxic zone to enter an aerobic zone filled with a suspended filler for organic matter degradation, ammonia nitrogen nitrification
Implementation Method 4
allowing a sludge-containing mixed liquor discharged from the aerobic zone to enter the sedimentation zone for sedimentation to obtain a supernatant and sludge
Implementation Method 5
filtering the supernatant through a biological filtration zone filled with a filler to further remove suspended solid particles
Data Source
AI summary
A method for advanced nitrogen and phosphorus removal in sewage treatment includes the following steps: feeding raw water and return sludge into a pre-denitrification zone for denitrification; allowing a sludge-containing mixed liquor discharged from the pre-denitrification zone to enter an anaerobic zone to undergo a biological phosphorus removal reaction; allowing a sludge-containing mixed liquor discharged from the anaerobic zone and a return nitrification liquid to enter an anoxic zone for denitrification; allowing a sludge-containing mixed liquor discharged from the anoxic zone to enter an aerobic zone for nitrification and excessive phosphorus uptake, and allowing part of a nitrification liquid to be returned to the anoxic zone; allowing a sludge-containing mixed liquor discharged from the aerobic zone to enter a sedimentation zone for separation; passing a resulting supernatant through a biological filtration zone; returning part of resulting sludge to the pre-denitrification zone; and the like.