Nitrogen Removal Using Ferrous Ferric Sulfate Mixture

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Solution Overview

Problem

Current methods for nitrogen removal from aqueous solutions, such as CANDO, require additional steps and materials like carbonate green rust, which can be costly and complex, and there is a need for more efficient alternatives.

Innovation Solution

A method using a mixture of ferrous sulfate and ferric sulfate to reduce NO2− to N2O, eliminating the need for carbonate sources and simplifying the process by directly adding the sulfate mixture to the reaction, enhancing the Fe(II)-mediated reduction and optimizing the conversion of NH4+ to N2, with real-time spectrophotometric measurement for precise reduction agent addition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If carbonate green rust or siderite is used for reduction of NO2− to N2O, then the reduction efficiency is maintained, but the process complexity and cost increase due to additional steps for producing green rust and adding carbonate sources

Engineering Contradiction:

Improvereduction efficiencyVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the unnecessary carbonate green rust production step and carbonate source addition from the CANDO process. By using a simplified Fe(II) salt system instead of requiring green rust synthesis, the patent removes complex preparatory steps while maintaining the core reduction function, thus reducing process complexity without sacrificing nitrogen removal efficiency

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the expensive and complex carbonate green rust with inexpensive, readily available Fe(II) salts that can be directly added to the system. These simple iron salts serve the same functional purpose of providing Fe(II) for nitrite reduction but are much cheaper and easier to handle, eliminating the need for complex green rust synthesis and stabilization

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If carbonate green rust is used for reduction of NO2− to N2O, then the reduction function is achieved, but the number of process steps increases

Engineering Contradiction:

Improvereduction functionVSAvoidnumber of process steps

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The invention merges the reduction function directly into the existing CANDO process by adding Fe(II) salts in the anoxic zone, eliminating the need for separate green rust production and addition steps. This integration maintains the reduction function while reducing the number of discrete process steps, making the overall nitrogen removal process more efficient and easier to operate

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If more iron is added to enhance N2O release and ammonia removal, then the nitrogen removal efficiency increases, but the amount of substance added increases

Engineering Contradiction:

Improvenitrogen removal efficiencyVSAvoidamount of iron added

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent optimizes the Fe(II) to Fe(III) ratio and the total iron dosage to achieve maximum nitrogen removal efficiency. By carefully controlling these parameters, the system achieves high productivity without requiring excessive amounts of iron salts, thus balancing effectiveness with material consumption

Inventive Principle:

Principle #35Parameter changes

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 reduces nitrogen levels in wastewaters with improved efficiency and reaction rates, minimizing steps and costs, while maintaining energy recovery and ammonia removal, even in wastewaters with high nitrogen concentrations, and allows for precise control of reduction agents.

Implementation Method 1

a mixture of ferrous sulfate and ferric sulfate is used for reduction of NO2− to N2O

Methodology Applied

Scientific EffectFe(II)-mediated reduction: Redox Reactions

Implementation Method 2

The addition of the mixture of ferrous sulfate and ferric sulfate directly to step (b) produces fresh amorphous iron oxyhydroxide

Methodology Applied

Scientific EffectThe addition of the mixture of ferrous sulfate and ferric sulfate directly to step (b) produces fresh amorphous iron oxyhydroxide, which enhances the Fe(II)-mediated reduction of NO2−: Precipitation

Implementation Method 3

converting NH4+ in the aqueous medium to NO2− by partial aerobic nitrification

Methodology Applied

Scientific EffectPartial aerobic nitrification: Oxidation

Implementation Method 4

partially reducing the obtained NO2− to N2O in anoxic conditions

Methodology Applied

Scientific EffectPartial anoxic denitrification: Reduction

Implementation Method 5

N2O conversion to N2 with energy recovery via catalytic decomposition of N2O

Methodology Applied

Scientific EffectCatalytic decomposition of N2O: Decomposition (biological)

Data Source

PatentUS10167215B2Method for nitrogen removal from aqueous medium

Publication Date: 2019.01.01 KEMIRA OY

AI summary

The invention relates to a method for nitrogen removal from aqueous medium, comprising steps of (a) converting NH4+ in the aqueous medium to NO2− by partial aerobic nitrification, (b) partially reducing the obtained NO2− to N2O in anoxic conditions, and (c) decomposing N2O to N2 with energy recovery. A mixture of ferrous sulfate and ferric sulfate is used in step (b) for reduction of NO2− to N2O.