Membrane Gravity Filter Conversion via Static Head Pressure
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Solution Overview
Problem
Conventional water treatment systems face inefficiencies in filtration processes, particularly in maintaining membrane permeability and flux without frequent regenerative chemical cleaning, and in integrating membrane technology into existing gravity sand filters.
Innovation Solution
The system converts a conventional gravity sand filter into a membrane gravity filter by replacing the granular media with immersed membranes, utilizing a static head differential for filtration and periodic low-dose oxidant backwashing to maintain membrane permeability and flux, eliminating the need for regenerative chemical cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If membrane filters are operated with frequent backwashing to maintain permeability, then membrane performance is maintained, but operational complexity and chemical cleaning requirements increase
Solution Approach 1:
The patent implements periodic backwashing at optimized intervals rather than continuous or frequent backwashing. The system performs backwashing only when necessary to maintain membrane performance, reducing operational complexity while ensuring reliability. This periodic action allows the membrane to operate between cleanings without requiring constant intervention.
Solution Approach 2:
The patent changes operational parameters including transmembrane pressure, flux rate, and backwash timing to optimize membrane performance. By adjusting these parameters, the system maintains permeability with fewer backwashing cycles, reducing operational complexity while preserving reliability.
2Productivity
If regenerative chemical cleaning is used to maintain membrane flux, then membrane performance is restored, but operational costs and chemical consumption increase
Solution Approach 1:
The patent extracts and eliminates the need for regenerative chemical cleaning from the operational process. By using optimized physical backwashing methods and controlling operational parameters, the system maintains membrane flux without requiring chemical cleaners, thereby reducing substance loss and operational costs.
Solution Approach 2:
The patent replaces expensive, long-lasting chemical cleaning agents with simpler, more economical physical cleaning methods. The system uses water-based backwashing and controlled flux management instead of chemical cleaners, reducing both substance consumption and operational costs while maintaining productivity.
3Manufacturing precision
If conventional gravity sand filters are converted to membrane filters, then filtration quality improves, but integration complexity with existing infrastructure increases
Solution Approach 1:
The patent designs the membrane filtration system to perform multiple functions within the existing gravity sand filter structure. The membrane module serves both filtration and flow distribution functions, reducing the need for separate components and simplifying integration with existing infrastructure while maintaining high filtration quality.
Solution Approach 2:
The patent nests the membrane filtration system within the existing gravity sand filter structure. The membrane module is integrated into the filter tank in a way that utilizes the existing housing, support structures, and flow paths, thereby reducing integration complexity while achieving improved filtration quality.
4Productivity
If high flux rates are used to increase water treatment capacity, then productivity increases, but membrane fouling and flux instability worsen
Solution Approach 1:
The patent implements dynamic control of flux rates rather than operating at constant high rates. The system adjusts flux dynamically based on membrane performance, fouling conditions, and operational requirements, maintaining productivity while ensuring flux stability through adaptive management.
Solution Approach 2:
The patent incorporates feedback mechanisms to monitor membrane performance and flux stability in real-time. By using this feedback information, the system can adjust operational parameters to maintain optimal flux rates, preventing fouling-related instability while preserving high treatment 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
This approach maintains stable membrane flux and water quality over extended periods, reducing operational costs and increasing filtered water recovery rates, while integrating seamlessly with existing infrastructure.
Implementation Method 1
the membrane pore size is usually in the ultrafiltration or microfiltration range
Implementation Method 2
the membrane pore size is usually in the ultrafiltration or microfiltration range
Implementation Method 3
Transmembrane pressure to cause a flow of permeate through the membrane is optionally created by a static head differential
Implementation Method 4
filtration is driven by gravity, the apparatus may be called a membrane gravity filter (MGF)
Implementation Method 5
One or more backwashes in a day include chlorine or another chemical agent a dose effective to increase the porosity of a biofilm or fouling layer
Data Source
AI summary
A conventional media filter such as a gravity sand filter is converted into a membrane filter. The media is removed and replaced by immersed membrane modules. Transmembrane pressure is created by a static head pressure differential, without a suction pump, thereby creating a membrane gravity filter (MGF). Preferred operating parameters include transmembrane pressure of 5-20 kPa, 1-3 backwashes per day, and a flux of 10-20 L/m2/h. The membranes are dosed with chlorine or another oxidant, preferably at 700 minutes*mg/L as Cl2 equivalent per week or less. The small oxidant does is believed to provide a porous biofilm or fouling layer without substantially removing the layer. The media filter may be modified so that backwash wastewater is removed from near the bottom of the tank rather than through backwash troughs above the membrane modules. Membrane integrity testing may be done while the tank is emptied after a backwash.