Separate to Destroy? Considerations for Handling Emerging Contaminants in RO Concentrate

Considerations for Handling Emerging Contaminants in RO Concentrate Katie Walker, PE, March 5 at 1: PM (Some) Reasons to Select RO Membranes for PFAS Numerous Short- Multiple Desire to High PFAS Levels Chain PFAS Contaminants Implement Novel Compounds Treated by RO Technologies Example: sources Example: sources Example: limited heavily influenced with PFAS and options for Example: landfill by discharges 1,4-dioxane discharge of PFAS leachate with (Cape Fear) waste PFAS levels in the range of 10,000 ng/L Option Option Option Option 4 RO Membrane Treatment Challenges RO Membrane Stage Influent Permeate Very Clean! Project Location: Greensboro, NC Mitchell WTP Water source: Lake Brandt, Lake Townsend Operates the Mitchell WTP (Lake Brandt) and Townsend WTP (Lake Townsend) Emerging Contaminants: PFAS Greensboro: Pilot Study Nanofiltration Membrane Column 1/2: IX Column 3: GAC/NS Column 4: GAC Column 1: IX Column 2: GAC Column 3: NS To Electrochemical Destruction BenchScale Unit Electrochemical Destruction Foam Fractionation Greensboro Pilot Study: Influent PFAS Levels PFPeS PFPeA PFHpS PFBA PFOA PFOS PFNA PFHxS PFHpA PFDA PFBS 6: FTS Date )L/gn( SAFP Greensboro Pilot Study: Concentrate Column Overview Product Benefits Challenges Manufacturer EBCTs Less prone to Not PFAS Jacobi fouling (larger selective 10 minutes GAC AquasorbF23 media) Higher EBCT = 20 minutes Calgon F400 compared to IX more vessels IX Fouls easily Evoqua Dowex 2 minutes PFAS-selective More expensive Low EBCT = (but need less of fewer vessels it) Cyclopure NS 5 minutes Dexsorb Greensboro Pilot Study: Foam Fractionation Flotation Reagent PFAS Laden Concentrated Foam PFAS Waste Stream Effluent (Reduced PFAS Levels) Project Location: Randleman, NC Wholesale drinking water provider Partners: Cities of Archdale, Greensboro, High Point, and Randleman; Town of JFK WTP Jamestown, and Randolph County Water source: Randleman Lake Operates the JFK WTP Emerging Contaminants: PFAS, 1,4-dioxane Piloting Conclusions Membranes are incredibly effective at emerging contaminant treatment Significant competition in concentrate stream High oxidant doses (ozone or UV) are required for 1,4-dioxane treatment Concentrate Treatment Considerations Order of adsorption versus oxidation Test UV/AOP downstream of GAC/IX Understand change in performance as adsorption technology is exhausted Impact on organics removal Impact on DBP formation potential Concentrate Treatment Considerations Compare increased concentration using foam fractionation versus additional membrane recovery Evaluate blending or recycling Limit water waste Limit needed post-treatment Understand regulatory/permitting requirements.