RO Membrane Cleaning via Direct Osmosis Backflow
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Solution Overview
Problem
Current direct osmosis methods for cleaning reverse osmosis membranes are limited by the need to stop the RO process, require costly equipment, can damage membranes, and are not environmentally friendly, with ineffective cleaning forces and limitations in brackish water desalination.
Innovation Solution
A direct-osmosis method using a super-saline solution with osmotic pressure higher than the raw saline solution is fed to the membrane to create a backward flow and lift foulants, allowing continuous RO operation without stopping the process, using existing equipment, and maintaining membrane integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct osmosis method is used to clean RO membrane, then cleaning effectiveness is improved, but RO process must be stopped
Solution Approach 1:
The patent enables continuous operation by allowing the RO process to proceed while simultaneously performing membrane cleaning through direct osmosis. The cleaning process does not require stopping the feed pump or interrupting permeate production, as the cleaning occurs in parallel with normal operation using a portion of the permeate flow
Solution Approach 2:
The system uses its own permeate output to perform the cleaning function. A portion of the produced permeate is redirected to the feed side of the membrane to create the direct osmosis effect, eliminating the need for external cleaning agents or separate cleaning systems
2Force
If high pressure is applied to permeate side for direct osmosis cleaning, then cleaning power is improved, but equipment cost increases significantly
Solution Approach 1:
The system utilizes the existing high-pressure feed pump and the natural osmotic pressure difference to generate the necessary cleaning force. The feed pump continues to operate at normal pressure, and the direct osmosis effect is achieved by redirecting permeate flow rather than introducing additional high-pressure equipment
Solution Approach 2:
The patent changes the operational parameters by adjusting the permeate flow distribution rather than increasing pressure. By controlling the ratio of permeate redirected for cleaning versus permeate sent to storage, the system achieves effective cleaning using existing pressure levels without requiring expensive high-pressure equipment modifications
3Reliability
If conventional cleaning chemicals are used, then foulant removal is improved, but environmental harm increases
Solution Approach 1:
The patent converts the normally discarded permeate stream into a beneficial cleaning agent. Instead of using harmful chemical cleaners, the system utilizes the physical properties of permeate water under direct osmosis conditions to remove foulants, turning a waste stream into a useful resource
Solution Approach 2:
The patent replaces chemical cleaning methods with a physical-mechanical cleaning process. The direct osmosis effect creates a backwash flow that mechanically lifts and removes foulants from the membrane surface without requiring chemical reactions or chemical agents
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 enables continuous membrane cleaning without stopping the RO process, reduces membrane damage, and is environmentally friendly, with effective foulant removal and prevention of bio-fouling and scaling, applicable to various water desalination systems.
Implementation Method 1
super saline solution having osmotic pressure POs>POr is fed for a predetermined injection time to the feed side of the membrane instead of the raw saline solution, such that backward flow of permeate towards the feed side is provided
Implementation Method 2
The process of reverse osmosis (RO) desalination of raw water includes basically the following: providing a semi-permeable membrane (RO membrane) which allows passing of the solvent (water) molecules and rejects dissolved salts
Data Source
AI summary
Direct-osmosis (DO) method for cleaning a semi-permeable membrane in a RO separation module, the membrane having a feed side with foulant located thereon, and an opposite permeate side. A normal RO separation process in the same module includes: feeding, under gauge pressure PGr, raw saline solution having osmotic pressure POr to the membrane feed side; collecting permeate (solvent) having osmotic pressure POp from the permeate side, under gauge pressure PGp; and removing residual brine from the membrane feed side. The method comprises feeding to the feed side of the membrane, for a predetermined injection time, super saline solution having osmotic pressure POs>POr, such that backward flow of permeate towards the feed side of the membrane is provided so as to lift the foulant from the feed side.