Reverse Osmosis Membrane Scaling Prevention via Sulfur Dioxide Injection
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Solution Overview
Problem
Reverse osmosis filtration systems face challenges with scaling and microbial buildup, leading to reduced membrane performance and increased operational costs, particularly in handling brine retentates that are not suitable for land application due to high osmotic pressure and bicarbonate levels.
Innovation Solution
The method involves injecting sulfur dioxide (SO2) into the feed water to generate sulfurous acid, which reduces alkalinity scaling, self-agglomerates solids, disinfects, and maintains osmotic pressure balance, allowing for the recovery and conditioning of brine retentates for land application by reducing bicarbonate levels and preventing biofilm formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse osmosis filtration is used to purify water, then product water filtrate is produced, but scaling and microbial buildup on membranes reduces performance over time
Solution Approach 1:
The patent applies preliminary action by injecting sulfur dioxide into the feed water before it reaches the reverse osmosis membranes. This pre-treatment converts bicarbonate to carbon dioxide and lowers pH, preventing scaling and microbial buildup on the membrane surfaces before the filtration process begins, thereby maintaining membrane performance and extending service life
Solution Approach 2:
The patent converts the harmful effect of bicarbonate (which causes scaling) into a beneficial outcome by using sulfur dioxide to transform it into carbon dioxide gas that can be vented. The bicarbonate is converted to carbonic acid, which decomposes to CO2 and water, eliminating the scaling problem while the resulting acidic environment also prevents microbial growth
2Adaptability or versatility
If brine retentate is discharged without treatment, then high osmotic pressure and bicarbonate levels cause scaling in discharge conveyance systems, but treatment is needed to enable land application
Solution Approach 1:
The patent applies parameter changes by adjusting the pH of the brine retentate through sulfur dioxide injection. This changes the chemical parameters of the brine, converting bicarbonate to carbon dioxide and lowering the pH to a range that prevents scaling in conveyance systems while making the brine suitable for land application to vegetation
3Object-affected harmful factors
If sulfur dioxide is injected to reduce alkalinity scaling, then scaling is reduced, but osmotic pressure must be maintained
Solution Approach 1:
The patent applies feedback by continuously monitoring the pH and alkalinity of the feed water and adjusting the sulfur dioxide injection rate accordingly. This feedback control ensures that scaling is prevented while maintaining the osmotic pressure balance necessary for effective reverse osmosis filtration, as the system dynamically responds to changing water quality parameters
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 extends membrane life, reduces cleaning frequency, and enables the reuse of treated water for irrigation by maintaining osmotic pressure and preventing biofilm growth, thereby lowering operational costs and enhancing water recovery.
Implementation Method 1
injecting into the feed water sulfur dioxide at a pH which generates sufficient SO2 to reduce alkalinity scaling conditions
Implementation Method 2
disinfects the water to inhibit bacterial growth on the separation membranes
Implementation Method 3
self agglomerates the solids to minimize adherence to the separation membranes
Implementation Method 4
Reverse osmosis is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure
Implementation Method 5
The magnitude of the pressure required to impede completely the flow of solvent is defined as the 'osmotic pressure'
Data Source
AI summary
A method for cleaning and maintaining reverse osmosis membrane filters by injecting sulfurous acid into water to form sulfurous acid (H2SO3), and then sequentially filtering the acidified water through membrane filters to reduce alkalinity and mineral scaling, add sufficient SO2 as a biocide to attack bacteria and other micro organisms to prevent membrane fouling, reduce iron to prevent iron deposit build-up, scavenge and remove dissolved oxygen prior to filtration to prevent membrane oxidation, and prevent concentrated salts within the retentate from precipitating out of solution during transport for land application.