Immersed Membrane Cross-Flow Scouring to Reduce Fouling Energy
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Solution Overview
Problem
Immersed membrane systems face issues with fouling and sludging due to the accumulation of solids, which are typically addressed using air bubbles for cleaning, leading to high energy consumption and operational costs.
Innovation Solution
Utilizing a cross flow liquid velocity of at least 0.01 m/s to scour the membrane surfaces, reducing or eliminating the need for air-based aeration, and optimizing the liquid flow rate and membrane spacing to enhance cleaning efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air bubbles are used to scour membrane surfaces, then fouling and sludging are inhibited, but energy consumption increases significantly
Solution Approach 1:
The patent replaces the mechanical aeration system (blowers and aerators) with a hydraulic flow system. Liquid feed flows are directed to create cross-flow velocities of 0.01-0.1 m/s across membrane surfaces, eliminating the need for separate aeration equipment and significantly reducing energy consumption while maintaining membrane cleanliness through hydrodynamic scouring
Solution Approach 2:
The invention transitions from pneumatic cleaning (air bubbles) to hydraulic cleaning (liquid cross-flow). By optimizing liquid flow rates and distribution, the system achieves effective membrane scouring through water shear forces, replacing the energy-intensive air injection process with a more efficient hydraulic mechanism
2Reliability
If liquid flow rate is increased to maintain low solids concentration, then membrane fouling is reduced, but operational costs increase
Solution Approach 1:
The patent optimizes liquid cross-flow velocity parameters to a specific range (0.01-0.1 m/s) that provides sufficient scouring power to prevent fouling while minimizing the energy required for liquid circulation. This parameter optimization balances membrane performance maintenance with reduced operational costs compared to conventional high-velocity systems
3Reliability
If air aeration is used to prevent sludging, then membrane module permeability is maintained, but device complexity increases
Solution Approach 1:
The invention extracts and eliminates the aeration subsystem (blowers, aerators, air distribution manifolds) from the membrane system. By using the existing liquid feed flow to create cross-flow velocities that prevent sludging, the system maintains module permeability without requiring separate aeration equipment, thereby reducing overall system complexity
Solution Approach 2:
The liquid feed flow serves dual functions: it provides the necessary cross-flow velocity for membrane scouring and simultaneously prevents sludging accumulation. This multi-functionality eliminates the need for dedicated aeration equipment, simplifying the overall system while maintaining membrane performance
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 reduces energy consumption and operational costs by using liquid flow as the primary cleaning mechanism, effectively preventing fouling and sludging while maintaining membrane performance.
Implementation Method 1
providing a liquid flow at an appropriate rate and velocity in a cross flow pattern past the surface of a membrane allows the liquid flow to be used as the primary or sole means to keep membrane surfaces clean. The volume and rate of the liquid flow is selected to provide enough shearing of the surface so as to clean the membrane surface.
Implementation Method 2
providing a liquid flow past the surface of the membranes at a cross flow velocity of at least 0.01 m/s
Data Source
AI summary
A method of operating an immersed membrane filtration system includes a step of providing a liquid flow, for example a recirculation flow, past the surface of the membranes to clean, or help clean, the membrane surface. Since immersed outside-in membranes are effectively filtering out clean water from the effluent, they are also dewatering the effluent. To avoid solids concentration, most immersed membrane systems require that a certain amount of effluent liquid is recirculated back to an area upstream of the membranes. This is called a recirculation flow in general and is, for example, associated with the flow of return activated sludge (RAS) in a membrane bioreactor (MBR). In systems and methods described herein, we control a recirculating flow to have enough energy to scour the surface of the membranes, thus combining its use of providing liquid to the membranes and scouring their surfaces.