Rotating Membrane Filter Discs for Wastewater Fouling Reduction
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Solution Overview
Problem
Membrane fouling in membrane bioreactors (MBRs) reduces filtration capacity and increases costs due to the challenge of achieving sufficient cross flow and shear on membrane surfaces, particularly when dealing with non-Newtonian fluids like sludge.
Innovation Solution
A pressurized filtration apparatus with rotatable membrane filter discs arranged eccentrically or oval-shaped within a cylindrical pressure vessel, generating high shear through a specific flow pattern and swirls, and utilizing porous aeration pipes to enhance oxygen dissolution and retention, thereby reducing fouling and maintaining higher permeate flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If obstruction elements or rotating shear generating elements are introduced to increase cross flow and shear on membrane surface, then fouling reduction and permeate flow are improved, but device complexity increases
Solution Approach 1:
The patent employs asymmetric positioning of the shaft relative to the pressure vessel, creating an eccentric arrangement where the shaft is offset from the center. This asymmetry generates non-uniform flow patterns and shear distribution across the membrane surface, enhancing cross-flow and reducing fouling without requiring additional complex mechanical components.
Solution Approach 2:
The patent utilizes the dynamic rotation of the shaft to generate time-varying flow patterns. The rotating membrane filter discs create continuously changing shear forces and cross-flow velocities across the membrane surface, effectively reducing fouling accumulation while maintaining a relatively simple static structure.
2Productivity
If higher cross flow is established to reduce fouling, then filtration capacity is improved, but energy consumption increases
Solution Approach 1:
The system utilizes the permeate pressure differential itself to drive the rotation of the shaft and membrane discs, creating a self-sustaining flow generation mechanism. The pressure gradient that drives filtration also powers the cross-flow generation, reducing the need for additional energy input while maintaining high filtration capacity.
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 apparatus effectively reduces membrane fouling by generating high shear and maintaining a higher permeate flow, allowing for efficient wastewater treatment with reduced operational costs and increased treatment capacity.
Implementation Method 1
The shear stress, T, is the product between viscosity, η, and strain rate, γ
Implementation Method 2
The cross flow depends on the velocity relative to the membrane surface and the cross flow influences the shear stress on the membrane
Implementation Method 3
utilizing porous aeration pipes to enhance oxygen dissolution and retention
Data Source
AI summary
A filtration apparatus (2), comprising a pressurised cylindrical pressure vessel (4) having a longitudinal axis (X); a shaft (8) having a longitudinal axis (Y) extending parallel to the longitudinal axis (X) of the pressure vessel (4); a plurality of rotatable membrane filter discs (6) arranged along the length of the shaft (8). The membrane filter discs (6) are spaced from each other attached to the shaft (8) and oriented transverse to the longitudinal axis (Y) of the shaft (8). The interior (10) of the membrane filter discs (6) are in fluid communication with a permeate discharge channel (12) extending parallel to the longitudinal axis (X) of the pressure vessel (4). The pressure vessel (4) has a cylindrical inner geometry without any significant obstruction elements. The longitudinal axis (X) of the pressure vessel (4) is laterally offset from the longitudinal axis (Y) of the shaft (8) and/or the membrane filter discs (6) are oval-shaped.