Cyclic Sulfur Denitrification Agent for Stable Nitrate Removal
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Solution Overview
Problem
Current denitrification methods using sulfur or iron sulfide as electron donors face issues with reduced denitrification efficiency due to sulfur oxidation, alkalinity decrease, and hydrogen sulfide odor generation, requiring frequent replenishment of electron donors and alkalinity adjustment.
Innovation Solution
An electron donor cyclic sulfur denitrification agent comprising sulfur particles, iron sulfide particles, iron hydroxide, sulfur oxidizing denitrifying bacteria, and sulfate reducing bacteria, where sulfur is circulated through internal reactions to maintain denitrification activity, reuse hydrogen ions, and convert sulfate ions back to sulfur particles, minimizing odor and alkalinity consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sulfur or iron sulfide is used as electron donor for denitrification, then denitrification reaction can proceed, but sulfur is oxidized to sulfate ion and consumed, causing denitrification efficiency to decrease and requiring frequent replenishment
Solution Approach 1:
The patent implements a cyclic system where sulfate ions produced by sulfur oxidation are converted back to sulfur particles by sulfate-reducing bacteria, creating a continuous loop that maintains denitrification activity without external replenishment. The system continuously cycles sulfur between oxidized and reduced states, ensuring sustained electron donor availability.
Solution Approach 2:
Instead of discarding the sulfate ions produced during sulfur oxidation, the patent recovers them by using sulfate-reducing bacteria to convert sulfate back into sulfur particles. This recovery mechanism transforms waste products back into useful electron donors, eliminating the need for frequent replenishment.
2Productivity
If sulfur oxidizing denitrifying bacteria are used for denitrification, then nitrate can be removed, but hydrogen ions are consumed causing alkalinity to decrease and requiring frequent alkalinity adjustment
Solution Approach 1:
The system incorporates a feedback mechanism where the sulfate ions produced during denitrification are detected and converted back to sulfur particles by sulfate-reducing bacteria. This feedback loop automatically regulates the system's chemical balance, converting excess sulfate and regenerating electron donors while maintaining alkalinity without external adjustment.
Solution Approach 2:
The denitrification system performs self-service by using the sulfate ions produced during nitrate removal to generate new sulfur particles through sulfate-reducing bacteria. The system automatically regenerates its own electron donors and maintains alkalinity balance without requiring external intervention or chemical addition.
3Productivity
If iron sulfide is used as electron donor, then denitrification can occur, but hydrogen sulfide odor is generated requiring frequent replacement
Solution Approach 1:
The patent converts the harmful hydrogen sulfide odor problem into a beneficial cycle by using sulfate-reducing bacteria to produce controlled amounts of sulfide that immediately react with iron to form iron sulfide particles. These particles serve as electron donors without releasing gaseous hydrogen sulfide, transforming a harmful emission into a useful solid-phase electron donor.
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 approach stabilizes denitrification reactions, reduces the need for frequent electron donor replenishment, maintains alkalinity, and eliminates hydrogen sulfide odor, ensuring long-term denitrification efficiency and water quality.
Implementation Method 1
the sulfur (S°) particles are converted to the sulfate ions (SO4 2-); any one iron sulfide particles or a mixture of two or more iron sulfide particles selected from a group of the iron sulfide particles including the Fe 2 S 3 particles, the FeS particles, and the FeS 2 particles is converted to the sulfate ions (SO4 2-)
Implementation Method 2
the mixture is used as the electron donors in the process of the sulfur oxidizing denitrifying bacteria decomposing the nitrate ions (NO3 -
Implementation Method 3
when the sulfate ion generated during the sulfur oxidation denitrification is converted to the hydrogen sulfide by the sulfate reducing bacteria (SRB)
Implementation Method 4
the iron hydroxide (Fe(OH) 3 ) chemically reacts in adsorption of these substances at a high rate to become the iron sulfide
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~4B
AI summary
Provided is an electron donor cyclic sulfur denitrification agent including sulfur (S°) particles; any one iron sulfide particles or a mixture of two or more iron sulfide particles selected from a group of iron sulfide particles including Fe2S3 particles, FeS particles, and FeS2 particles; iron hydroxide (Fe(OH)3) particles; sulfur oxidizing denitrifying bacteria; and sulfate reducing bacteria. In the electron donor cyclic sulfur denitrification agent of the present invention, since sulfur circulates through reactions in the forms of iron sulfide (an electron donor for denitrification) and iron hydroxide (adsorbent of H2S) by sulfur oxidizing denitrifying bacteria and sulfate reducing bacteria, it has an advantage of maintaining denitrification activity for a longer time by minimizing the replenishment of additional electron donors as compared with the denitrification reaction using sulfur (S0) in the related art. In addition, with respect to the electron donor cyclic sulfur denitrification agent of the present invention, when the sulfate ion generated during the sulfate denitrification is converted to the hydrogen sulfide by the sulfate reducing bacteria (SRB), the iron hydroxide (Fe(OH)3) chemically adsorbs and removes these substances, so that it has an advantage in that there is no odor caused by the hydrogen sulfide. In addition, the electron donor cyclic sulfur denitrification agent of the present invention reuses hydrogen ions generated during the S° denitrification reaction, minimizing the consumption of the alkalinity, so that it has an advantage of maintaining denitrification activity for a longer period of time than the denitrification reaction using only sulfur as a sole electron donor in the related art. Therefore, by using the electron donor cyclic sulfur denitrification agent of the present invention, it is expected that a stable denitrification reaction can be performed without generating odor and minimizing the supply of additional electron donors and the alkalinity.