Reverse Osmosis Membrane Cleaning via Intermittent Alkaline Water Contact
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Solution Overview
Problem
Current reverse osmosis membrane processing methods face challenges with membrane fouling and high cleaning chemical costs when processing highly alkaline water with ammonia and high TOC concentrations, as they require frequent and costly chemical cleaning to maintain membrane efficiency.
Innovation Solution
The method involves adjusting the pH of processing-target water from 9.5 or higher to 4 to 8 and passing it through a reverse osmosis membrane device, using alkaline water from a different step for intermittent cleaning, which inhibits slime formation and reduces cleaning chemical costs by utilizing waste water for membrane cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chlorine-based oxidizing agent is added to sterilize processing-target water, then microorganism proliferation is prevented, but oxidative degradation of the permeable membrane occurs
Solution Approach 1:
The patent converts the harmful effect of chlorine on polyamide membranes by using polyvinylidene fluoride (PVDF) membranes instead, which have inherent chlorine resistance. The harmful interaction between chlorine and polyamide is avoided by substituting the membrane material with one that can withstand chlorine exposure without degradation.
Solution Approach 2:
The patent changes the membrane material parameter from polyamide to polyvinylidene fluoride (PVDF), which fundamentally alters the membrane's chemical resistance properties. PVDF membranes can withstand chlorine-based disinfectants without oxidative degradation, thereby maintaining sterilization effectiveness while preventing membrane damage.
2Productivity
If pH is adjusted to 9.5 or higher for highly alkaline water processing, then flux deterioration is prevented, but ammonia removal efficiency decreases
Solution Approach 1:
The patent applies preliminary action by conducting alkaline treatment (pH adjustment to 9.5 or higher) intermittently before RO processing to prevent slime formation and flux deterioration. By maintaining the membrane surface in an alkaline state during intervals, the membrane remains clean and flux is preserved, while ammonia removal is optimized during the actual RO processing phases.
Solution Approach 2:
The patent implements periodic action through intermittent alkaline water circulation and pH adjustment cycles. The system alternates between alkaline treatment phases (for slime prevention and flux maintenance) and RO processing phases (for ammonia removal), optimizing both flux productivity and ammonia removal efficiency through time-dependent operational cycles.
3Productivity
If frequent membrane cleaning is performed to prevent fouling, then membrane efficiency is maintained, but cleaning chemical costs increase
Solution Approach 1:
The patent applies self-service by using the process water itself (highly alkaline water with pH 9.5 or higher) for membrane cleaning instead of external cleaning chemicals. The alkaline process water naturally prevents slime formation and can be used to clean the membrane surface, eliminating the need for separate cleaning chemical inputs while maintaining membrane efficiency.
Solution Approach 2:
The patent implements multi-functionality by making the highly alkaline water serve dual purposes: (1) as the processing medium for RO treatment to prevent flux deterioration during operation, and (2) as the cleaning agent for membrane maintenance. This eliminates the need for separate cleaning chemicals and reduces overall substance consumption.
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 inhibits membrane fouling, reduces cleaning chemical costs, and allows for more frequent cleaning without the need for alkaline chemicals or specialized equipment, ensuring efficient ammonia removal and low operational expenses.
Implementation Method 1
reverse osmosis membrane separation processing in which suspended matter, dissolved substances, or ions in processing-target water are separated using a reverse osmosis membrane (RO membrane)
Implementation Method 2
bringing highly alkaline water having a pH of 9.5 or higher into contact intermittently with an RO membrane device to prevent contamination of a permeable membrane due to microorganisms
Data Source
AI summary
This reverse osmosis membrane processing method comprises adjusting processing-target water to a pH range of 4 to 8 and passing the water through a reverse osmosis membrane device. The reverse osmosis membrane processing method is characterized in that alkaline water having a pH of 9.5 or higher is brought into contact intermittently with the reverse osmosis membrane of the reverse osmosis membrane device. Raw water may be preprocessed with active carbon, or the like, to serve as the processing-target water. If the processing-target water has a pH of 9.5 or higher, this processing-target water may be used as the alkaline water.