Salinity Gradient Power Plant for Zero Liquid Discharge Salt Byproduct
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Solution Overview
Problem
The disposal of high salinity waste streams from desalination plants poses significant environmental and economic challenges, including increased salinity in water sources and high costs for landfilling or sequestration, and the low value of municipal wastewater effluent limits its recycling and reuse options.
Innovation Solution
A salinity gradient power generation plant utilizing a high salinity feed from zero liquid discharge desalination plants and a low salinity feed from municipal wastewater treatment plants to produce a mixed water output, which can be discharged into a body of water, leveraging the salinity difference to generate power through membrane-based processes like pressure retarded osmosis or reverse electrodialysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high salinity waste stream is discharged back into the environment, then disposal cost is reduced, but salinity of local water sources increases
Solution Approach 1:
The patent converts the harmful high salinity waste stream into a beneficial resource by using it as feedstock for salinity gradient power generation. The high salinity stream, which would otherwise be an environmental pollutant, is now utilized to drive osmotic power generation processes, simultaneously disposing of the waste and generating electricity.
Solution Approach 2:
The patent changes the salinity parameter of the waste stream by mixing it with low salinity water from municipal wastewater treatment plants. This parameter change enables the mixed stream to serve as suitable feedstock for salinity gradient power generation while reducing the harmful salinity concentration before environmental discharge.
2Productivity
If ZLD technologies are used to reduce desalination byproducts to solid salts, then water recovery is enhanced, but energy consumption and cost increase
Solution Approach 1:
Instead of completely converting all high salinity waste to solid salts through energy-intensive crystallization, the patent applies partial action by using a portion of the waste stream for power generation and mixing the remainder with municipal wastewater effluent for discharge. This partial approach achieves water recovery goals while avoiding the excessive energy consumption of complete ZLD.
Solution Approach 2:
The patent merges two waste streams - high salinity desalination brine and low salinity municipal wastewater effluent - to create a mixed stream with intermediate salinity suitable for salinity gradient power generation. This combining approach allows both streams to be utilized productively while reducing overall disposal costs and energy requirements.
3Quantity of substance
If municipal wastewater effluent is discharged offshore, then disposal capacity is increased, but environmental disruption occurs due to salinity and density differences
Solution Approach 1:
The patent changes the salinity parameter of municipal wastewater effluent by mixing it with high salinity desalination brine. This parameter adjustment reduces the salinity and density difference between the discharged water and receiving seawater, thereby minimizing environmental disruption while maintaining disposal capacity.
4Loss of energy
If salt byproduct is landfilled or sequestered, then disposal is achieved, but cost and uncertainty increase
Solution Approach 1:
The patent transforms the problematic salt byproduct into a valuable resource for power generation. Instead of landfilling or sequestering the salt waste with associated costs and uncertainties about long-term environmental behavior, the patent utilizes it as high salinity feedstock to generate electricity through osmotic processes.
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 transforms waste into a valuable energy source, reducing landfill costs, providing a sustainable solution for desalination byproducts and wastewater treatment, while generating clean power and improving the environmental compatibility of effluent discharge.
Implementation Method 1
leveraging the salinity difference to generate power through membrane-based processes like pressure retarded osmosis or reverse electrodialysis
Implementation Method 2
leveraging the salinity difference to generate power through membrane-based processes like pressure retarded osmosis
Implementation Method 3
leveraging the salinity difference to generate power through membrane-based processes like reverse electrodialysis
Data Source
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Figure 3a
AI summary
A method and apparatus are described for disposing of salt byproduct from a zero liquid operation, such as a zero liquid discharge desalination plant. The present method and apparatus concern a power generation plant, comprising a salinity gradient power unit (SGPU) comprising a high salinity feed, a low salinity feed, and a mixed water output. The high salinity feed is comprised of salt byproduct from a ZLD operation. The mixed water output empties into a body of water.