AWWA ACE68911

Eastern Municipal Water District (EMWD), located in southern California, recently completed two brine treatment studies, one for the California Department ofWater Resources (DWR) and the other for the United States Department of Interior, Bureau ofReclamation (USBR). These studies investigated the cost of different alternative processtreatment trains to recover additional usable water from primary reverse osmosis (RO) brine,and either reduce the volume of brine significantly, or go to complete zero-liquid discharge(ZLD). The studies included pilot scale, bench scale and desktop evaluations of bothestablished and emerging technologies for brine treatment. Chemical softening of primary RObrine followed by either a second RO process or electrodialysis reversal (EDR) is an example ofso-called established technologies; emerging technologies investigated included membranedistillation (MD), forward osmosis (FO) and seeded reverse osmosis. A 50-gpm chemicalsoftening process was operated for 6-months and provided feed water to RO and EDR pilotunits. MD and FO were tested at bench scale, and seeded RO was operated in a batch pilot plant.Capital and operation and maintenance (O&M) cost estimates were established for several treatment configurationsthat also included brine concentration, crystallization and pond evaporation. These were thencompared. Overall, total annual costs for 14 different treatment train combinations weregenerally within about 10-percent of each other. Treatment for removal and recovery of salablesalt byproducts was, however, more costly, probably because of the capital costs associatedwith selective precipitation and washing and processing of the salts. Treatment trains thatincluded a third concentration step (using the seeded RO process) ahead of thermal mechanicalevaporation appeared to have slightly lower overall costs. This is attributed to the reduced sizeof the thermal evaporation process. Additional work on MD, FO and the seeded RO processesis needed. Includes 4 references, tables, figure.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

57

File Size:

1 file , 1.2 MB