Energy and Rejection Considerations in RO Membrane Selection

Orange County Water District Acknowledgements Mehul Patel Operations Staff SPI Derrick Mansell Jim Vickers Craig Liebzeit Dave Henry Outline of Presentation GWRS System Pilot Testing Energy Cost Calculation Takeaway Key Points OCWD – SPI History SPI and OCWD working together since the 1980’s OCWD as early adopter of membrane technology for municipal wastewater treatment beginning with Water Factory 21 in 1976. SPI guidance 400 – 700 million data points per year Data is filtered, averaged, calculated, and archived SPI provides operational support and training OCWD – GWRS System RO Units 5 mgd design capacity Units (rated at 130 mgd, 1 spare) 2007 Original Units (Train A-E) 2015 Additional Units (Trains F&G) 2022 Additional Units (Trains H&I) RO Element Facts  6 different elements from 4 different suppliers  28,350 membranes installed (27×1050)  >66,000 membranes placed in service since 2007 GWRS Membranes Manufacturers through 17 years of operation CSM Hydranautics LG Filmtec (Dow, now Dupont) Why not stick with one? GWRS Membranes Why not stick with one? Many Variables Membranes Change Performance Changes Water Quality Changes Regulatory aspect Changes OCWD – Pilot Testing What do we test for? Permeate Water Quality Fouling behavior in our feed water matrix Specific Flux Cleanability OCWD – Pilot Testing How do we test? 5000 – 8000 h of filtration Operate till threshold once more 400 h for initial stabilization Clean membranes with aggressive procedure Set cleaning threshold Clean membranes with standard procedure At parameters: pH, Temp., Conc., Duration Data Allow for stabilization (~200h) OCWD – Pilot Testing Ranking from 2018 Ranking Ranking Membrane Specific Rejection Flux LG BW ES 0.158 99.22 Dow BW30 – XFRLE 0.137 99.41 Hydranautics ESPA2-LD 0.113 99.46 Toray TMG 20D 0.114 99.43 Energy Cost Calculation Initial Results LG pilot test vs full unit LG highest operational cost Ranking Membrane Specific Rejection Flux LG BW ES 0.158 99.22 Dow XFRLE 0.137 99.41 Hydranautics ESPA2-LD 0.113 99.46 Toray TMG 20D 0.114 99. Parameter LG BW ES Dow XFRLE Specific Flux Pilot 0.158 0. Specific Flux Year 1 0.090 0.114 Lower specific flux membrane produces permeate with superior Feed electrical conductivity quality? ~1,750 μS/cm Turbidity equal (MF Effluent) Potential difference in feed water Both membranes produced quality cause for more fouling? a ~20 μS/cm permeate. 2. Energy Cost Calculation – Dow & Dupont What impact did this difference have? At MGD production new Dupont membrane showed 9% higher feed pressure Year Avg. 34% higher total unit kW Membrane: Dow Dupont Feed Pressure 144 157 12% lower specific flux Feed Pressure kW 234 Boost Pressure average 20 Boost Pressure kW 16 Total kW 251 Area weighted SF 0.115 0. Operational cost difference?