Evaluation and Testing of Technologies for Brine Minimization at Eastern Municipal Water District

Eastern Municipal Water District (Eastern) in Southern California is facing increasing brine disposal challenges at its two inland desalter facilities. In most cases at inland sites, the disposal of brine involves either the dilution of the waste stream in another receiving body or the concentration of brine solutions (Truesdall et al., 1995). In the case of Eastern, brine streams from these facilities is discharged to the Santa Ana Regional Interceptor (SARI) line, which carries brine flow to coastal Orange County for disposal. However, due to increasing brine line costs and limited capacity, Eastern is looking to a future of brine minimization and, perhaps, Zero Liquid Discharge (ZLD) operation for greater water recovery. In order to determine the costs feasibility and future process components to achieve this goal, Eastern partnered with Carollo Engineers to perform a series of pilot scale, bench top and desktop evaluation of brine minimization and recovery technologies. This work is being funded, in part, by both California Prop 50 and United States Bureau of Reclamation (USBR) grants. This paper will present findings of this project, which started at the end of 2005. More specifically, this project utilized pilot testing to explore the use of secondary Reverse Osmosis (RO), seeded slurry RO, or Electrodialysis Reversal (EDR) for the concentration of existing primary, and existing, RO brine streams. Testing included intermediate brine softening, silica removal, and pH adjustment before treatment with secondary membrane systems. Parallel work was undertaken in collaboration with the University of Nevada-Reno (UNR) to investigate the use of Forward Osmosis (FO) and Membrane Distillation (MD) – two emerging technologies that may lead to economical treatment of brine streams. Evaluation of these processes was accomplished using existing Eastern brine samples and more concentrated brine streams produced from the secondary RO pilot process. Finally, brine concentration was studied using pilot testing of brine samples at RCC/Ionics and salt product recovery using the SALPROC™ process is being evaluated. All together, their analyses will allow for the evaluation of brine minimization and ultimate ZLD treatment at Eastern.