Membrane Protection via Redox Potential Control
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Solution Overview
Problem
Reverse osmosis membranes in desalination plants face oxidative degradation and fouling due to chemical substances and biofouling, leading to unstable operations and increased costs, as existing methods for preventing oxidative degradation are either ineffective or costly.
Innovation Solution
A method involving the intermittent or continuous dosing of a scale inhibitor with a reducing function, such as phosphorous acid-based organic compounds, upstream from the semipermeable membrane module to maintain the oxidation-reduction potential at a threshold value, combined with the use of oxidants for sterilization and reductants for neutralization, to prevent oxidative degradation and fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxidants are dosed to prevent biofouling, then biofilm formation is inhibited, but reverse osmosis membranes suffer oxidative degradation
Solution Approach 1:
The patent introduces a reductant as an intermediary substance that neutralizes oxidants before they contact the reverse osmosis membranes. The reductant acts as a mediator between the oxidant dosing system and the membrane, allowing biofouling prevention while protecting the membrane from oxidative damage.
Solution Approach 2:
The patent extracts the harmful oxidative function from the water stream by dosing reductants that specifically target and neutralize oxidants. This separates the beneficial biofouling prevention effect (achieved through controlled oxidant dosing) from the harmful membrane degradation effect (prevented through reductant neutralization).
2Object-affected harmful factors
If reductants are dosed to neutralize oxidants, then oxidative degradation is prevented, but operation costs increase
Solution Approach 1:
The patent applies partial action by dosing reductants at controlled levels sufficient to neutralize oxidants but not excessive. The dosing is optimized to achieve the minimum necessary protection against oxidative degradation while minimizing chemical consumption and operation costs.
Solution Approach 2:
The patent changes the chemical parameters of the water stream by introducing reductants that alter the oxidation-reduction potential. This parameter change enables the system to maintain protective conditions for membranes while controlling chemical dosage and associated costs.
3Object-affected harmful factors
If sufficient pretreatment is carried out to protect membranes, then oxidative degradation is reduced, but pipe lines become fouled
Solution Approach 1:
The patent converts the harmful effect of oxidants (which cause membrane degradation) into a beneficial effect for pipe line protection. By dosing oxidants upstream where they can prevent biofouling in pipes, and then neutralizing them before membrane contact, the system transforms a potentially harmful substance into a useful protective agent for the distribution system.
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 the operation of reverse osmosis membranes by preventing oxidative degradation and fouling, ensuring efficient and cost-effective fresh water production from seawater and other raw waters while maintaining membrane integrity.
Implementation Method 1
A method involving the intermittent or continuous dosing of a scale inhibitor with a reducing function, such as phosphorous acid-based organic compounds, upstream from the semipermeable membrane module to maintain the oxidation-reduction potential at a threshold value
Implementation Method 2
The reverse osmosis technology having been applied to desalination of seawater and reuse of sewage or wastewater allows production of desalinated water by applying pressure higher than osmosis pressure to water containing solutes such as salts, and forcing the water to pass through semipermeable membranes
Data Source
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AI summary
The present invention relates to a fresh water generation method including: feeding raw water or pretreated water thereof as feed water into a semipermeable membrane module in a pressurized state using a booster pump, thereby separating the feed water into a concentrate and a permeate having a low concentration, in which a scale inhibitor having a reducing function is dosed intermittently or continuously upstream from the semipermeable membrane module, thereby inhibiting scale generation and maintaining an oxidation-reduction potential of at least either the feed water or the concentrate to a threshold value or lower.