Economical and sustainable disposal of zero liquid discharge salt byproduct
View Patent ↗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.
1. A method of generating power comprising:
i) providing dehydrated high salinity output (DHSO) from a zero liquid discharge (ZLD) desalination plant and rehydrating said DHSO to form a rehydrated high salinity feedwater (RHSF) having a salinity content of between about 150,000-300,000 ppm;
ii) providing a low salinity feedwater comprising effluent from a wastewater treatment plant said low salinity feedwater having a salinity content of about 500-2,000 ppm;
iii) feeding said RHSF from i) to a salinity gradient power unit (SGPU) as a high salinity feed to said SGPU;
iv) feeding said low salinity feedwater from ii) to a SGPU as a low salinity feed to said SGPU;
v) generating electrical power in said SGPU;
vi) producing a mixed water output from said SGPU; and
vii) discharging said mixed water output into a body of water whereby the salinity of said mixed water output does not exceed the salinity of said body of water by more than 3%.
2. The method as recited in claim 1 wherein said low salinity feedwater from ii) is used to rehydrate said DHSO.
3. The method as recited in claim 1 wherein said SGPU is a reverse electrodialysis unit.
4. The method as recited in claim 1 wherein said SGPU is a pressure-retarded osmosis unit.
5. The method as recited in claim 1 wherein said mixed water output is mixed with said low salinity feedwater before being discharged into said body of water.