To Clean, or Not to Clean, That is the Question

Agenda Facility Background Cleaning Performance Evaluation Cost-Benefit Analysis Recommendations and Next Steps Northern WTP History Multi-phase MGD Capacity MGD Capacity MGD Capacity renewable water RO Trains 1 + RO Trains 3 + RO Train 5 project UV Bypass Redundant 4th 5, AFY Stage brackish Replaced Phase 1 groundwater wells elements Facility Design Criteria Well Capacity: 15, GPM RO Bypass: 10-30% Finished Water Flow: 13, GPM Overall Recovery: 94.75% Parameter Value Unit RO System 1st and 2nd Stage Number of RO Trains 4 (LPRO) Total Permeate 9, GPM Design Criteria Total Concentrate 1, GPM Recovery 85% Array 48:24 (7 elements/vessel) Stage Membrane Toray TMH20A-400C Ultra-low pressure brackish water 99.3% Rejection 3rd and 4th Stage Number of RO Trains 4 (HPRO) Total Permeate 1, GPM Total Concentrate GPM Recovery 60-65% Array 12:6 (6 elements/vessel) Membranes Toray TMG20D- Low pressure brackish water 99.7% Rejection Source Water Quality Silica and hardness limit recovery Silica controlled by anti-scalant ahead of LPRO Calcium carbonate controlled by hydrochloric acid between 2nd and 3rd stages ECCV’s Common Cleaning Triggers LPRO Skids – Feed pressure above 160 psi OR Differential pressure above 20 psi OR Caustic + Acid Pump speed above 93% HPRO Skids – Stage 3 pressure above 200 psi OR Stage 4 normalized permeate Acid + Silica production below 40 gpm Toray’s TMM- Guidelines for RO Cleaning Normalized differential pressure increases more than 20% OR Normalized permeate flow rate decreases by more than 10% OR Normalized salt passage increases by more than 20% Cleaning Performance Evaluation Focused on: Feed pressure as primary indicator for cleans HPRO Skids Proprietary silica cleans Last two operating years Limitations: Cleaning logs have limited information Cost Benefit Analysis $480/element $7k/proprietary clean 108 – 144 elements per HPRO Skid Proprietary clean needs to extend life at least 3 months to be worthwhile at 3 $52-69k per HPRO for complete years of operation element replacement Proprietary clean needs to extend life at Typical RO element life 3 to 7 years least 9 months to be worthwhile at ECCV HPRO element life 3 to 5 years years of operation NPV for each month of operation Does not account for additional energy $800-2000 for 3 to 7 year lifespan costs or salt passage impacts Recommendations and Next Steps Always perform acid clean prior to silica clean Monitor length of time following acid + silica cleans until cleaning trigger is hit If acid + silica clean does not decrease feed pressures for at least 3 to 9 months  consider replacement of elements Complete PFAS rejection piloting for aged and deteriorated elements Must monitor salt passage of elements to determine if replacement required regardless of cleaning recovery.