AWWA WQTC64104

A research project, funded by AwwaRF and the California Energy Commission (CEC), has been conducted to develop a treatment technique that reduces energy consumption and treatment costs for inland desalination with zero liquid discharge (ZLD). The project title is Zero Liquid Discharge and Volume Minimization for Inland Desalination and the final report will be issued in 2007. In ZLD desalination the concentrate is treated to produce desalinated water and essentially dry salts, and there is no discharge of liquid waste from the site. The technical approach involved treating the concentrate from a primary RO in a fluidized bed crystallizer to remove recovery limiting salts, then passing the treated concentrate through a secondary RO for further recovery. After the secondary RO the total recovery for most brackish water applications is expected to be 95 to 99 percent. The final concentrate volume would thus be reduced to a flow where evaporation ponds, enhanced evaporation systems, or thermal desalination become feasible for final separation of water from the salts. The research methodology included computer modeling, bench-scale testing, and pilot-scale testing. Testing was conducted on groundwater, surface water, finished water, and reclaimed water provided by the project utility partners, City of Phoenix, Southern Nevada Water Authority (SNWA), City of Scottsdale, Beverly Hills, and San Antonio Water System (SAWS). The project approach and some of the bench-scale results are discussed in this paper. Includes 4 references, tables, figures.