Multistage A/O Wastreatment for Low-Temperature Nitrogen Removal
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Solution Overview
Problem
Traditional biological wastewater treatment systems face challenges in achieving stringent nitrogen removal standards, especially at low temperatures, due to limited nitrification performance and high energy consumption, which is not environmentally friendly.
Innovation Solution
A biological nitrogen removal method using multistage feeding and multistage anoxic/aerobic chambers with biofilms in different functional reaction zones, incorporating reflux ratios and external carbon sources to optimize nitrogen removal, reducing hydraulic loading and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional activated sludge system uses single-stage or multi-stage A/O processes, then nitrogen removal can be achieved, but at low temperature the nitrification performance is limited and sludge age and hydraulic retention time must be much longer
Solution Approach 1:
The system divides the nitrogen removal process into multiple stages with distinct functions: anoxic zones for denitrification, aerobic zones for nitrification, and specific functional zones for ammonia removal and phosphorus removal. This segmentation allows each zone to operate optimally for its specific function, achieving high nitrogen removal efficiency without requiring excessively long retention times.
Solution Approach 2:
Different zones within the system are designed with locally optimized conditions: anoxic zones have conditions favorable for denitrifying bacteria, aerobic zones have conditions for nitrifying bacteria, and specific zones have conditions for ammonia-oxidizing bacteria. This local quality optimization enables efficient nitrogen removal at low temperatures without extending overall retention time.
2Productivity
If air flow is increased to maintain nitrobacteria activity at low temperature, then nitrogen removal is improved, but energy consumption increases
Solution Approach 1:
The system separates aeration requirements into specific aerobic zones rather than aerating the entire system continuously. This allows aeration to be applied only where and when needed for nitrification, significantly reducing overall energy consumption while maintaining nitrogen removal efficiency.
Solution Approach 2:
The system maintains continuous nitrogen removal through the multi-stage process with optimized hydraulic flow, eliminating the need for excessive aeration to compensate for slow reaction rates at low temperatures. The continuous flow through optimized zones ensures efficient nitrogen removal without energy waste.
3Productivity
If larger biochemical reactors are constructed to ensure nitrogen removal biomass quantity, then nitrogen removal capacity is improved, but capital investment on civil works increases
Solution Approach 1:
The system achieves high nitrogen removal capacity through multiple compact functional zones rather than one large reactor. This segmentation allows for more efficient space utilization and reduces the overall civil works required while maintaining or enhancing nitrogen removal capacity.
Solution Approach 2:
Each zone is optimized for its specific function with appropriate biomass concentration and reaction conditions, maximizing the nitrogen removal efficiency per unit volume. This local optimization reduces the total reactor volume needed compared to a conventional single-stage system.
4Device complexity
If activated sludge is exposed to anoxic/aerobic environment alternately, then treatment process is simplified, but bacteria with specific functionality cannot be cultured effectively
Solution Approach 1:
The system maintains simplicity through a continuous flow process while segmenting the environment into distinct anoxic and aerobic zones. This allows different functional bacteria to be cultured simultaneously in their respective zones without requiring complex alternating operations, achieving both simplicity and specific bacterial functionality.
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 achieves efficient nitrogen removal, with total nitrogen removal rates of up to 82.49% and ammonia nitrogen removal rates of 99.51% at low temperatures, while significantly reducing energy consumption and operational costs.
Implementation Method 1
facultative heterotrophic biofilms attached to surfaces of the suspended biofilm carriers remove nitrate nitrogen through influent carbon source denitrification
Implementation Method 2
aerobic heterotrophic biofilms attached to surfaces of the suspended biofilm carriers remove organic matters in wastewater
Implementation Method 3
aerobic autotrophic biofilms attached to surfaces of the suspended biofilm carriers remove organic nitrogen and ammonia nitrogen in wastewater
Data Source
AI summary
A biological nitrogen removal method based on multistage feeding and anoxic/aerobic chambers for adopting a constant flow operation mode, enabling wastewater subjected to primary treatment to enter a first-stage and a second-stage A/O reaction units from two position points; lifting and refluxing an effluent to an influent end of the first-stage units; lifting and refluxing an effluent to an influent end of the second-stage units; and clarifying, separating and discharging an effluent from an outlet end of a third-stage A/O reaction unit. The wastewater treatment mode combines a process based on two-stage wastewater feeding and three-stage anoxic/aerobic chambers with biofilms in different reaction zones, =optimizing and controlling a reflux ratio of each segment according to an amount of organic matters available for denitrification in influent, reducing the impact of hydraulic loading at the cross section in the reactors while removing organic matters and nitrogen-containing pollutants at a low temperature.