Membrane Cleaning with Pulsed Water Hammer and Osmotic Backwash
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Solution Overview
Problem
Existing membrane cleaning methods for semi-permeable membranes used in Reverse Osmosis processes are inefficient and environmentally harmful, as they require stopping the process, use harsh chemicals, and cannot effectively remove biofilm-like fouling.
Innovation Solution
A method involving directional gauge pressure strokes in the permeate or residual brine stream to induce membrane feed forward sagging pulses and simultaneous permeate backward flow, mechanically shaking the membrane to detach fouling biofilm, without changing the process from reverse osmosis to forward osmosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard CIP cleaning method is used with harsh chemicals, then fouling is removed, but environmental problems arise and process interruption occurs
Solution Approach 1:
The patent replaces chemical cleaning with a mechanical cleaning system that uses controlled pressure oscillations and vibrations to remove fouling from membranes. The mechanical vibration system generates oscillating flows that physically dislodge fouling deposits without requiring harsh chemicals, thereby eliminating environmental problems associated with chemical disposal while maintaining effective fouling removal.
Solution Approach 2:
The patent employs periodic pressure oscillations and vibrations applied to the membrane system to enhance fouling removal. By applying oscillating pressures at specific frequencies, the system creates periodic flow patterns that prevent fouling accumulation and facilitate its removal, allowing continuous operation without process interruption while avoiding chemical use.
2Reliability
If tangential vibration is applied to membrane elements, then colloidal suspension is separated, but power consumption increases and membrane wear accelerates
Solution Approach 1:
The patent applies dynamic pressure oscillations rather than continuous vibration, adjusting the frequency and amplitude of pressure waves to match the natural frequency of fouling detachment. This dynamic approach reduces energy consumption by applying vibration only when most effective for fouling removal, rather than continuous operation, while still achieving effective separation.
Solution Approach 2:
The patent changes the parameters of pressure oscillation (frequency, amplitude, duration) to optimize cleaning effectiveness while minimizing energy consumption and membrane stress. By carefully controlling these parameters, the system achieves effective fouling removal with reduced power input and minimized mechanical wear on membrane elements.
3Reliability
If continuous vibration is applied during normal operation, then fouling is prevented, but membrane wear and power consumption increase
Solution Approach 1:
The patent uses periodic, intermittent vibration cycles rather than continuous vibration during normal operation. The system applies vibration at specific intervals or when fouling detection thresholds are reached, providing sufficient anti-fouling protection while allowing the membrane to operate without constant mechanical stress, thereby extending membrane service life while maintaining fouling prevention.
4Reliability
If membrane cleaning is performed by stopping the RO process, then chemical CIP can be applied, but productivity is reduced
Solution Approach 1:
The patent enables continuous membrane cleaning during normal RO operation by integrating the mechanical vibration system into the operating process. The system can apply cleaning vibrations without stopping the feed pump or interrupting permeate production, maintaining continuous productivity while effectively removing fouling. The oscillating pressure waves are superimposed on the normal operating pressure, allowing simultaneous production and cleaning.
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 method effectively removes biofilm fouling with minimal environmental impact, enhancing membrane performance and efficiency by synchronizing mechanical shaking with osmotic backward flow, reducing the need for chemical cleaners and process interruptions.
Implementation Method 1
A generator of water stroke may be positioned in said permeate stream or in said residual brine stream to create a pressure wave
Implementation Method 2
a semi-permeable membrane (14) having a feed side (8) and a permeate side (15)
Implementation Method 3
the gauge pressure on the feed side is higher than the gauge pressure on the permeate side. As a result, under these circumstances the membrane surface gets a wave-like profile
Data Source
Figure 1a~1c
Figure 2~3
Figure 4~5
AI summary
Apparatus and method for semi-permeable membrane cleaning in particular, applying series of pulsed water stroke, made simultaneously with osmosis backward flow causing superposed membrane directional shaking and fouling detachment. Pulsed water stroke provided by water stroke generator as several momentum sharp changes in gauge pressure and induce velocity pulse of residual brine flow. The pulsed water strokes ideally induce resonance in the membrane. Osmosis backward wash may be provided either by injection for predetermined injection time, additional solution selected in such way that net driving pressure becomes opposite to normal osmotic operation thereby providing a backward flow of permeate towards to the side opposite to normal operation mode, so as to lift said foulant, or by throttling permeate exiting from the permeate enclosure, until the net driving pressure value become equal to zero, during application of precise synchronized and opposing brine and permeate pressure strokes thereby providing a plurality of quick RO-FO-RO process changes. These procedures allow a membrane to be kept continuously clean and operate at higher recovery.