Reversing the Flow – Full-Scale Operations of the First Municipal Flow Reversal Reverse Osmosis for Brackish Groundwater

Full-Scale Operations of the First Municipal Flow Reversal Reverse Osmosis for Brackish Groundwater Alex Waite, City of Santa Monica March 5, 2024 Goals of the City’s Sustainable Water Master Plan Diverse, sustainable, & drought resilient water supply to support a sustainable community Reduction of energy footprint to support carbon reduction goals for the City Long term cost benefits for rate payers Closing the Loop on the One Water Cycle Component Conservation Potable Water Wastewater To City of Los Angeles Arcadia WTP Clean Beaches Charnock Recycled SWIP Initiative Tank Water AWTF + Component SMURRF New Local Groundwater Olympic Well Field Restoration Component Alternative Water Supply Olympic Well Field Restoration Project New UV/AOP + GAC well head treatment Removal of key contaminants: 1,4-Dioxane, TCE, PCE, & 1,2,3-TCP One of the highest 1,4Dioxane removal applications in United States (2.6 log removal) Arcadia WTP Production Efficiency Enhancement Increase maximum influent capacity from 10 mgd to 13 mgd Retrofit existing RO skids to achieve 90% or greater recovery Changes from Conventional to FRRO Parameter Original Retrofitted PV Stage 39:19:9 43:21: Configuration (1st:2nd:3rd) Maximum Recovery 85% 90%+ (true operating max of 83%) Design Flux 13.5 gfd 12.8 gfd Interstage Booster 2nd stage booster only Replaced 2nd stage and new 3rd stage with inline vertical centrifugal pumps Rotating Block Static – 10 static 1st stage vessels Configuration – 14 rotating blocks of 3 vessels each “A” thru “N” for 1st/3rd stage operations – 21 2nd stage vessels rotating as one Instrumentation Existing typical Existing plus new pressure transmitters, flow instrumentation meters, and permeate/conductivity probes Controls Existing PLC and train RIO New PLC, existing train RIO plus new RIO cabinet Specific Energy Consumption (SEC) Compared to Conventional System FRRO average SEC of Incomplete CIP 0.25 kWh/m3 performed on 12/18 (At 83% recovery, conventional system SEC was 0.29 kWh/m3) Other Full-Scale Design Considerations Many MANY pneumatic valves Position indicators and feedback are key Check pneumatic throttling valves Set preventative maintenance schedule early Maintain higher pneumatic air pressure for more optimized valve closure times Set your shims – proper membrane loading is critical Retrofit vs. Next Steps Continue 2-month full-scale contractual testing period to prove out performance guarantee Optimize FRRO to reduce transition time and increase overall recovery 2nd stage rotation every other cycle Decrease valve closure times Increase plug-flow mode duration between transitions Finalize permit amendment for Olympic Well Field Restoration.