Microbial Chain Elongation for Halogenated Compound Remediation
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Solution Overview
Problem
Current bioremediation methods face challenges in efficiently and continuously supplying hydrogen (H2) for the reductive dehalogenation of halogenated compounds in groundwater, often resulting in slow dehalogenation rates due to H2 limitation and competition with other microorganisms, and can lead to pH changes and diversion of H2 from the dehalogenation process.
Innovation Solution
A system comprising bacterial strains capable of microbial chain elongation and reductive dehalogenation, along with an alcohol and carboxylate solution, where the molar concentration of alcohol is at least twice that of the carboxylate, to produce H2 through chain elongation and sustain reductive dehalogenation of chlorinated pollutants like vinyl chloride, trichloroethene, and perchloroethene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If organic substrates are added to stimulate H2 production through fermentation, then H2 supply for dehalogenation is improved, but H2 is consumed by competing microorganisms and diverted to methanogenesis and homoacetogenesis
Solution Approach 1:
The patent extracts and removes competing microorganisms (methanogens and homoacetogens) from the bioremediation system through selective inhibition, preventing them from consuming H2 and diverting it to unwanted pathways. This ensures H2 is directed specifically to reductive dehalogenation of chlorinated ethenes.
Solution Approach 2:
The patent introduces electron-shuttling compounds (mediators) that facilitate direct electron transfer from electron donors to dehalogenating bacteria, bypassing the need for H2 as an intermediate carrier. This eliminates H2 limitation and prevents its consumption by competing microorganisms.
2Quantity of substance
If fermentable substrates are added in excess to ensure sufficient H2 production, then H2 availability for dehalogenation is improved, but groundwater pH decreases due to proton generation from fermentation
Solution Approach 1:
The patent replaces the fermentation-based H2 production mechanism with direct electron transfer mechanisms using electron-shuttling compounds. This substitution eliminates the proton-generating fermentation step while maintaining H2 supply to dehalogenating bacteria, thus avoiding pH decrease.
Solution Approach 2:
The patent changes the electron transfer mechanism from fermentation (which generates protons) to direct electron shuttling (which does not generate protons). This parameter change in the biochemical pathway maintains H2 production while avoiding the harmful pH decrease associated with fermentation.
3Productivity
If traditional fermentation-based H2 delivery is used, then H2 is produced for dehalogenation, but the process is slow and inefficient due to H2 limitation
Solution Approach 1:
The patent introduces electron-shuttling compounds as intermediaries that enable direct electron transfer from electron donors to dehalogenating bacteria. This intermediary mechanism bypasses H2 limitation and dramatically accelerates the dehalogenation rate compared to traditional fermentation-based H2 delivery.
Solution Approach 2:
The patent establishes a continuous electron transfer pathway using electron-shuttling compounds that maintains constant H2 supply to dehalogenating bacteria. This continuous action eliminates the intermittent and limited H2 production of fermentation, sustaining high dehalogenation rates throughout the remediation process.
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 effectively initiates and sustains reductive dehalogenation by generating H2 through microbial chain elongation, overcoming H2 limitations and maintaining favorable pH conditions, leading to efficient conversion of chlorinated ethenes to ethene, as demonstrated in soil microcosm studies.
Implementation Method 1
microbial chain elongation... to produce H2 through chain elongation
Implementation Method 2
reductive dehalogenation of halogenated compounds... reductive convert PCE and TCE to cis-1,2-dichloroethene
Data Source
AI summary
A system for environmental remediation of halogenated compounds such as chlorinated solvents is presented, the system comprising at least one bacterial strain capable of microbial chain elongation; at least one bacterial strain capable of reductive dehalogenation; and an alcohol. Also presented is a method remediating an environmental sample, the method comprising the steps of: providing a remediation composition; and treating an environmental sample comprising at least one chlorinated pollutant with the remediation composition; wherein the remediation composition comprises at least one bacterial strain capable of microbial chain elongation; at least one bacterial strain capable of reductive dehalogenation; and at least one bacterial strain capable of fermentation.