Biological Filtration Zone with Segmented Anoxic Tanks for Nitrogen Removal
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Solution Overview
Problem
Traditional sewage treatment processes face challenges in achieving efficient nitrogen and phosphorus removal, particularly when the carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratios in sewage are low, leading to interference with biological phosphorus removal and high costs associated with filtration technologies.
Innovation Solution
A device comprising a pre-denitrification zone, anaerobic zone, anoxic zone, aerobic zone, sedimentation zone, biological filtration zone, and clear water zone, with integrated sludge and nitrification liquid return systems, and a filler layer for biological filtration, which optimizes the treatment process to reduce nitrate nitrogen interference and improve phosphorus and nitrogen removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional A2O process is used for nitrogen removal, then denitrification can be completed, but nitrate nitrogen in return sludge interferes with biological phosphorus removal when C/N and C/P ratios are low
Solution Approach 1:
The patent divides the traditional single anoxic tank into two separate anoxic tanks: a first anoxic tank dedicated to denitrification of return sludge, and a second anoxic tank for denitrification of nitrification return liquid. This segmentation prevents nitrate nitrogen from the first anoxic tank from interfering with phosphorus removal in the anaerobic tank, while maintaining effective nitrogen removal through coordinated operation of both anoxic zones.
Solution Approach 2:
The patent introduces an intermedi— a first anoxic tank as a buffer zone between the anaerobic tank and the second anoxic tank. This intermediary tank receives return sludge and performs preliminary denitrification, preventing nitrate nitrogen from directly entering the anaerobic tank and interfering with phosphorus accumulating organisms, thus mediating the conflict between nitrogen and phosphorus removal processes.
2Manufacturing precision
If mid-pass fiber membrane or flat membrane filtration is used, then suspended solid particle concentration can be kept below 10 mg/L, but service life is limited resulting in high investment, cleaning, maintenance, and replacement costs
Solution Approach 1:
The patent replaces expensive, limited-life membrane filtration systems with a more economical filtration approach using affordable filter media that can be easily replaced. The system uses filter materials such as quartz sand, activated carbon, or ceramic particles in a gravity-driven filtration tank, eliminating the need for costly membrane replacements while maintaining effluent quality standards.
Solution Approach 2:
The patent replaces the mechanical pump-based membrane filtration system with a gravity-driven filtration system. The filtration process relies on natural gravity flow through the filter media bed, eliminating the need for complex mechanical filtration equipment, high-pressure pumps, and extensive cleaning mechanisms, thereby reducing both capital investment and operational complexity.
3Manufacturing precision
If sand filtration device is used for decentralized sewage treatment, then filtration can be achieved, but investment cost per ton of water is relatively high and backwash process involves high energy consumption
Solution Approach 1:
The patent implements a periodic backwash system that operates only when necessary, rather than continuous high-energy filtration. The gravity-driven filter allows operation without energy input during normal filtration, and uses periodic low-energy backwashing with collected effluent water to restore filter media, significantly reducing overall energy consumption compared to continuous mechanical filtration systems.
Solution Approach 2:
The filtration system is designed to be self-sufficient by using the treated effluent itself for the backwash process. The system collects clean effluent from the filtration outlet and redirects it to the backwash inlet, creating a closed-loop system that eliminates the need for external water sources or high-energy pumping, allowing the system to maintain itself using its own output.
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
The device effectively enhances phosphorus and nitrogen removal efficiencies, reduces chemical oxygen demand (COD), and lowers operational costs by minimizing the need for additional filtration systems and energy consumption, especially for sewage with low C/N and C/P ratios.
Implementation Method 1
a filler layer is provided in the biological filtration zone, and the filler layer divides a cavity in the biological filtration zone to form an upper water inlet cavity and a lower water outlet cavity
Implementation Method 2
a backwash aeration pipe is provided in the water outlet cavity
Implementation Method 3
a sludge return system is provided between the pre-denitrification zone and the sedimentation zone, and the sludge return system can return sludge in the sedimentation zone to the pre-denitrification zone
Implementation Method 4
a nitrification liquid return system is provided between the anoxic zone and the aerobic zone, and the nitrification liquid return system can return a nitrification liquid in the aerobic zone to the anoxic zone
Implementation Method 5
The denitrification in an ordinary anaerobic/anoxic/oxic (A2O) process is completed by an anoxic tank and an anaerobic tank, where nitrate nitrogen in return sludge undergoes denitrification in the anaerobic tank
Implementation Method 6
nitrate nitrogen in nitrification return liquid undergoes denitrification in the anoxic tank
Implementation Method 7
there is still enough carbon source for phosphate accumulating organisms (PAOs), and thus the biological phosphorus removal effect will not be affected
Implementation Method 8
a sedimentation zone, with integrated sludge and nitrification liquid return systems
Data Source
AI summary
A device for advanced nitrogen and phosphorus removal in sewage treatment includes a pre-denitrification zone, an anaerobic zone, an anoxic zone, an aerobic zone, a sedimentation zone, a biological filtration zone, and a clear water zone, where a sludge return system is provided between the pre-denitrification zone and the sedimentation zone; a nitrification liquid return system is provided between the anoxic zone and the aerobic zone; a filler layer is provided in the biological filtration zone, and the filler layer divides a cavity in the biological filtration zone to form an upper water inlet cavity and a lower water outlet cavity; a backwash aeration pipe is provided in the water outlet cavity, and a backwash water outlet is formed in the water inlet cavity; and the backwash water outlet is connected to a sludge concentration and storage tank or the pre-denitrification zone.