Composite Semi-Permeable Membrane Thickness Ratio for Wastewater Clogging
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Solution Overview
Problem
Composite semi-permeable membranes used in high-pressure wastewater treatment face efficiency decline due to clogging and require frequent washing, which reduces treatment efficiency and membrane durability.
Innovation Solution
A composite semi-permeable membrane with a polymer porous layer on a nonwoven cloth layer and a polyamide separation function layer, where the thickness ratio of the polymer porous layer to the nonwoven cloth layer is 0.22 to 0.45, maintaining high permeation flux and efficiency even under elevated pressure, and enhanced by a polyvinyl alcohol coating for improved flux retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the membrane is operated at high pressure to treat high turbidity wastewater, then the treatment efficiency and permeation flux are improved, but the membrane is prone to clogging and requires frequent washing
Solution Approach 1:
The membrane support structure is segmented into multiple layers with different functions: a nonwoven cloth layer for mechanical strength, a polymer porous layer for flow distribution, and a polyamide separation layer for filtration. This segmentation allows each layer to optimize its specific function, reducing overall clogging susceptibility while maintaining high pressure operation capability
Solution Approach 2:
The membrane incorporates a polymer porous layer with controlled porosity and pore size distribution that allows efficient passage of water molecules under high pressure while preventing accumulation of suspended particles. The porous structure is designed to maintain open pathways that resist clogging even during continuous high-pressure operation
2Reliability
If the membrane is frequently washed to remove clogging, then the membrane surface is cleaned, but the treatment efficiency decreases due to operation stops
Solution Approach 1:
The membrane surface is pre-treated with a polyvinyl alcohol coating that creates a hydrophilic barrier before actual operation begins. This preliminary coating prevents particle adhesion and clogging formation during high-pressure operation, eliminating the need for frequent washing stops and maintaining continuous high treatment efficiency
Solution Approach 2:
The membrane structure is designed to be inherently resistant to clogging through its multi-layer construction and surface properties, allowing it to maintain performance without external intervention. The self-cleaning effect is achieved through the hydrophilic coating that prevents particle accumulation, eliminating the need for separate washing operations
3Reliability
If washing agents such as chlorine are used to clean the membrane, then the membrane is cleaned, but the membrane deteriorates
Solution Approach 1:
The polyvinyl alcohol coating on the membrane surface acts as a sacrificial protective layer that prevents direct contact between harsh washing agents and the underlying polyamide separation layer. This coating converts the harmful effect of chlorine exposure into a benign process where only the coating is affected, preserving the integrity of the critical separation function layer
Solution Approach 2:
The polymer porous layer and polyvinyl alcohol coating serve as intermediary protective layers between the harsh washing environment and the sensitive polyamide separation layer. This intermediary structure allows necessary washing operations to proceed while shielding the vulnerable separation layer from chemical deterioration
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 membrane maintains a permeation flux retention rate of 80% or more, ensuring high treatment efficiency and durability during continuous high-pressure operation, effectively addressing the issues of clogging and washing-related efficiency decline.
Implementation Method 1
a composite semi-permeable membrane having a polymer porous layer on one surface of a nonwoven cloth layer, and a polyamide separation function layer on the polymer porous layer
Implementation Method 2
water to be treated is continuously supplied to a membrane module having a spiral-type composite semi-permeable membrane element at a high pressure of about 1 to 7 MPa
Data Source
AI summary
The objective of the present invention is to provide a composite semi-permeable membrane having high processing efficiency even when processing of wastewater having a suspended matter content high enough to tend to result in clogging, said processing efficiency being unlikely to decline even under elevated-pressure operation accompanying continuous use at high pressure. The present invention pertains to a composite semi-permeable membrane having a polymer porous layer on one surface of a nonwoven cloth layer, and a polyamide separation function layer on the polymer porous layer, wherein the ratio of the thickness of the polymer porous layer to the thickness of the nonwoven cloth layer is 0.22 to 0.45.