The Indian Wells Valley Water District (District) in Ridgecrest, California, is located in the Mojave Desert about 150 miles inland from Los Angeles. As part of their planning for future water supplies, the District undertook a study to evaluate treatment of local brackish groundwater sources (TDS in the range of 1,300 to 2,000 mg/L). Pilot testing of treatment technologies to treat the local brackish groundwater was conducted. The treatment train to be tested (identified in the earlier feasibility study) included iron and manganese removal, followed by reverse osmosis (RO), with further treatment of the RO concentrate by electrodialysis reversal (EDR). Due to the location of the District, a zero-liquid discharge solution for brine management and disposal had to be found. Brine concentration of the EDR concentrate, followed by final disposal in small evaporation ponds was the configuration identified. A novel “reversible”configuration in the RO step was tested on the pilot plant. The reversible feature allows for the feed flow to each RO
membrane stage to be reversed periodically, thus making the lead element the lag element, and so on. A 25-gpm RO pilot plant was designed and built for the project. Results indicated that, when operating on a 24-hour reversible cycle, the performance during normal (full-time forward operation) and reversible operation was about the same. There was not much to distinguish the results. However, when the reversible cycle time was reduced to 12 hours and then to 8 hours, noticeable improvements in performance were observed, to the point where normalized net driving pressure flattened in both membrane stages indicating a reduction in fouling. Membrane autopsy results suggest that biofouling may be reduced by applying the reversible operation feature.
This presentation is available to AMTA Members only.
- Graham Juby, PhD, PE
- Carollo Engineers, Inc.
- AMTA Annual Meeting, San Diego, CA
- San Diego Biennial
- Reversible reverse osmosis, brackish groundwater, EDR, Concentrate