Forward Reverse Osmosis Desalination System for Low Pressure Operation
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Solution Overview
Problem
Conventional reverse osmosis desalination systems require high pressures, leading to high energy consumption, frequent membrane fouling and scaling, and costly maintenance, making them inefficient and expensive.
Innovation Solution
A pressure-reduced saline water treatment system combining forward osmosis and reverse osmosis units, where seawater is first treated in a forward osmosis unit and then in a reverse osmosis unit, operating at lower pressures and utilizing hydraulic pressure from the reverse osmosis unit to enhance water transport in the forward osmosis unit, reducing energy consumption and extending membrane life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high pressure is applied in reverse osmosis to overcome osmotic pressure and achieve efficient desalination, then salt removal efficiency is improved, but energy consumption increases and membrane fouling accelerates
Solution Approach 1:
The desalination process is divided into two separate stages: forward osmosis for initial concentration and reverse osmosis for final purification. This segmentation allows each process to operate under optimal pressure conditions, with FO handling bulk concentration at low pressure and RO providing final polishing at high pressure, thereby reducing overall energy consumption while maintaining high salt removal efficiency
Solution Approach 2:
Forward osmosis performs preliminary concentration of seawater before reverse osmosis processing. By pre-concentrating the feed water in FO, the subsequent RO stage operates on more concentrated stream, improving its efficiency and reducing the total pressure-time product required, thus lowering energy consumption while achieving the desired salt removal
2Manufacturing precision
If high pressure is applied in reverse osmosis to achieve efficient desalination, then salt removal efficiency is improved, but membrane fouling and scaling increase requiring frequent maintenance
Solution Approach 1:
The system segments the desalination process into FO and RO stages, with FO handling the bulk of concentration work under low pressure. This protects the RO membrane from exposure to high volumes of concentrated feed at high pressure, reducing fouling and scaling rates, thereby extending membrane service life while maintaining high salt removal efficiency
Solution Approach 2:
Forward osmosis acts as a protective cushion before the RO stage by performing preliminary concentration under low pressure. This pre-treatment reduces the burden on the RO membrane, cushioning it against severe fouling and scaling conditions, thus extending its operational life while achieving efficient desalination
3Manufacturing precision
If high pressure reverse osmosis is used for desalination, then salt removal efficiency is improved, but system cost increases due to expensive materials and maintenance
Solution Approach 1:
The system is segmented into FO and RO units, allowing different material specifications for each stage. The FO unit can use less expensive materials since it operates at low pressure, while the RO unit uses high-pressure rated materials only where necessary. This segmentation reduces overall system cost while maintaining high salt removal efficiency
Solution Approach 2:
The system changes the pressure parameter across different stages: low pressure in FO and high pressure in RO. This parameter variation allows optimization of material selection and system design for each stage, reducing overall system cost while achieving efficient desalination through the combined process
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 system operates at lower pressures, reducing energy consumption, extending membrane life, and lowering maintenance costs, while enabling integration with renewable energy sources and using cost-effective materials, thus providing a more efficient and sustainable desalination process.
Implementation Method 1
water flows through a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration based on the osmotic pressure difference
Implementation Method 2
A "draw" solution or solution of high concentration relative to that of the feed solution is used to induce a net flow of water through the membrane into the draw solution
Implementation Method 3
an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential differences of the solvent
Implementation Method 4
In reverse osmosis, an applied pressure is used to overcome osmotic pressure
Data Source
AI summary
The pressure-reduced saline water treatment system combines both forward osmosis and reverse osmosis techniques for the desalination of salt water, such as seawater. A feed side of the reverse osmosis desalination unit is in fluid communication with the feed side of the forward osmosis desalination unit, such that seawater drawn through the feed side of the forward osmosis desalination unit is fed into the feed side of the reverse osmosis desalination unit. The reverse osmosis desalination unit outputs product water extracted from the seawater from a permeate side thereof. The feed side of the reverse osmosis desalination unit outputs a reject stream, which is fed to a draw side of the forward osmosis desalination unit, such that the draw side of the forward osmosis desalination unit receives the reject stream and outputs concentrated brine.