Microbial Electrolysis Cell for Nitrate Removal
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Solution Overview
Problem
Current methods for removing oxidized nitrogen compounds from water, such as biological denitrification and bioelectrochemical systems, are inefficient and energy-intensive, particularly at varying nitrate concentrations, and do not effectively minimize greenhouse gas emissions like nitrous oxide.
Innovation Solution
A microbial electrolysis cell (MEC) system with a potentiostat-controlled cathode potential range of -0.20 to 0.0 V vs Standard Hydrogen Electrode, using a cation exchange membrane and denitrifying bacteria to reduce oxidized nitrogen compounds to nitrogen gas, optimizing electron flux and energy availability for efficient nitrate removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If biological heterotrophic denitrification is used to remove nitrates from water, then nitrate is transformed to harmless nitrogen gas, but considerable amount of sludge is produced which requires additional treatment and the method is only suitable for low concentration nitrates
Solution Approach 1:
The patent changes the fundamental parameters of the denitrification process by using autotrophic denitrifying bacteria instead of heterotrophic bacteria. This requires no external carbon source and produces minimal sludge, while maintaining high nitrate removal efficiency through the natural metabolic pathways of autotrophic bacteria that use inorganic electron donors.
Solution Approach 2:
The invention extracts and eliminates the need for external carbon sources from the denitrification process. By using autotrophic bacteria that can perform denitrification with inorganic electron donors (such as hydrogen, sulfur compounds, or iron), the system removes the requirement for organic carbon addition, thereby preventing sludge production while maintaining productivity.
2Productivity
If external carbon source is added to support biological denitrification of high concentration nitrate, then nitrate removal is enhanced, but operational costs increase and sludge production increases
Solution Approach 1:
The patent implements self-service by using autotrophic denitrifying bacteria that can sustain the denitrification process using inorganic electron donors present in the system or easily obtainable from the environment. This eliminates the need for continuous addition of external carbon sources, reducing operational costs while maintaining high nitrate removal efficiency.
Solution Approach 2:
The invention converts the limitation of high nitrate concentration (which typically requires large amounts of carbon source) into an advantage by using autotrophic bacteria. These bacteria can handle high nitrate loads efficiently using inorganic electron donors, transforming what would be a costly requirement for carbon addition into a low-cost process using naturally available inorganic substances.
3Object-generated harmful factors
If inorganic electron donors such as hydrogen are used through electrolysis for autotrophic denitrification, then carbon dioxide emission is reduced, but high energy input is required
Solution Approach 1:
The patent optimizes the energy parameters by selecting specific inorganic electron donors and optimizing their dosing rates. Instead of using hydrogen through electrolysis which requires high energy input, the system uses alternative inorganic electron donors that can be more efficiently utilized by the autotrophic bacteria, thereby reducing energy consumption while maintaining low carbon dioxide emissions.
Solution Approach 2:
The invention converts the potential harm of high energy consumption into a benefit by carefully selecting and optimizing the use of inorganic electron donors. The system achieves autotrophic denitrification with minimal energy input by using electron donors that match the metabolic capabilities of the specific autotrophic bacterial strains employed, transforming an energy-intensive process into an energy-efficient one.
4Productivity
If conventional bioelectrochemical systems are used for nitrate removal, then nitrate is reduced, but the systems are inefficient at varying nitrate concentrations and do not effectively minimize greenhouse gas emissions
Solution Approach 1:
The patent introduces dynamic control mechanisms that allow the system to automatically adjust to varying nitrate concentrations. By using real-time monitoring and feedback control of the electron donor dosing and electrical parameters, the system dynamically optimizes its operation to maintain high nitrate removal efficiency across a wide range of influent concentrations, thereby achieving both productivity and adaptability.
Solution Approach 2:
The invention implements feedback control where the system continuously monitors nitrate concentration, current production, and other key parameters, and uses this information to adjust operational parameters such as electron donor dosing rate, applied voltage, or hydraulic flow rate. This feedback mechanism ensures the system remains efficient and adaptable to varying conditions while minimizing greenhouse gas emissions through optimized denitrification.
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 MEC system achieves high nitrate reduction efficiency (up to 93.9%) with reduced operational costs and minimal greenhouse gas emissions, adapting to varying nitrate concentrations and maintaining water quality standards, while being economically competitive with conventional technologies.
Implementation Method 1
the cathode potential is poised in a range comprised of from -0.20 and 0.0 V vs Standard Hydrogen Electrode (SHE)... denitrifying bacteria to reduce oxidized nitrogen compounds to nitrogen gas
Implementation Method 2
using a cation exchange membrane
Implementation Method 3
A microbial electrolysis cell (MEC) system with a potentiostat-controlled cathode potential range of -0.20 to 0.0 V vs Standard Hydrogen Electrode, optimizing electron flux and energy availability
Data Source
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AI summary
The invention relates to a method and microbial electrolysis cell (MEC) for the treatment of contaminated water, by biocatalysed reduction of oxidised nitrogen compounds (nitrate, nitritre and nitrous oxide) to nitrogen gas. The cathode potential is poised to -0.220 to 0 V vs SHE with a potentiostat.