Reverse Osmosis Membrane Element Design for Fouling Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Reverse osmosis membranes used in treating water containing high-molecular-weight organic matter, such as MBR-treated water, experience significant fouling, leading to decreased permeate flux and increased differential pressure, which existing technologies fail to address effectively.
Innovation Solution
A reverse osmosis membrane device with a spiral-type membrane element having a membrane surface area satisfying the formula membrane surface area ≥ n^2 × (11/16), operated at a permeate flux of 0.6 m/d or less, and a hydraulic linear velocity of 0.1 m/s or more, to reduce concentration polarization and prevent fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the raw water spacer is increased to prevent clogging by suspended matter, then the differential pressure increase is avoided, but the membrane surface area per element becomes smaller and the permeate flow rate per element is reduced
Solution Approach 1:
The invention changes the thickness parameter of the raw water spacer from conventional large thickness to specifically 0.3-0.5mm, optimizing it to balance between preventing clogging and maintaining membrane surface area. This parameter optimization resolves the contradiction by finding the optimal thickness value that provides sufficient channel clearance while maximizing membrane area per element.
2Productivity
If the thickness of the raw water spacer is reduced to increase the membrane surface area per element, then the permeate flow rate per element increases, but the channels tend to be clogged by suspended matter
Solution Approach 1:
The invention optimizes the raw water spacer thickness to 0.3-0.5mm, which is thinner than conventional spacers but sufficient to prevent clogging. This parameter change enables achieving both goals: increased membrane surface area (60-70% increase) while maintaining adequate channel clearance to prevent suspended matter accumulation.
3Reliability
If a large thickness of raw water spacer is used to prevent clogging, then the differential pressure stability is improved, but the adsorption of membrane contaminants still causes decrease in permeate flux
Solution Approach 1:
The invention changes the spacer thickness to 0.3-0.5mm and combines it with optimized operating conditions (permeate flux 0.4-0.6 m/d, hydraulic linear velocity 0.08-0.12 m/s) to simultaneously address both differential pressure stability and permeate flux stability, preventing both clogging and contamination effects.
Solution Approach 2:
The invention optimizes the hydraulic linear velocity to 0.08-0.12 m/s to create sufficient shear force at the membrane surface that prevents contaminant adsorption and maintains permeate flux. This dynamic parameter optimization works together with the spacer thickness to resolve the contradiction between differential pressure stability and permeate flux stability.
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
The solution stabilizes the treatment of water with high-molecular-weight organic matter by maintaining permeate flow rates and preventing fouling, allowing for long-term stable processing.
Implementation Method 1
reverse osmosis membranes have been used for removing ions, organic matter, or similar from raw water
Implementation Method 2
the pressure difference between the raw water and concentrate sides of the membrane element
Implementation Method 3
a phenomenon called concentration polarization occurs on the membrane surface, and a great degree of concentration polarization leads to a high concentration of the solute on the membrane surface
Data Source
AI summary
Provide is a reverse osmosis membrane device that is capable of treating raw water containing membrane-fouling substance in large quantities, such as MBR-treated water, in a stable manner while preventing decreases in permeate flow rate, and a method for operating thereof. A method for operating a reverse osmosis membrane device that treats raw water containing high-molecular-weight organic matter, wherein the raw water contains high-molecular-weight organic matter having a molecular weight of 10,000 or more at a concentration of 0.01 ppm or more, wherein the reverse osmosis membrane device is equipped with a spiral-type reverse osmosis membrane element that has a membrane surface area satisfying the below formula (1), and wherein the reverse osmosis membrane device is operated at a permeate flux of 0.6 m/d or less:membrane surface area(m2)≥n2×(11/16) (1)wherein n represents a diameter (inches) of the reverse osmosis membrane element.