NF-RO Membranes System: An Unique Treatment Approach for Removal of Unusual Organics in Groundwater

NF-RO Membranes System: An Unique Treatment Approach for Removal of Unusual Organics in Groundwater March 5, 2024 TUE04 Silvana Ghiu, PhD, PE Hazen and Sawyer Mario Bautista WRD Agenda Introduction to Brackish Groundwater Reclamation Program Goldsworthy Desalter – Existing Fouling Issues Pretreatment Pilot Preliminary Design Key Parameters Planning for Month Pilot Study Steps Forward Goldsworthy Fouling Issues Foulant Scraped from Stage Stage Membrane Organic Content (%) 86% 85% Inorganic Content (%) 14% Parameter Design Current Flow Split, CYW/DPW (%) 50/50 54/46 Reduced Production RO Feed Flow (gpm) 3,900 3,645 from 5 to 3.6 mgd RO Permeate Flow (gpm) 3,120 2,734 Reduced Recovery Recovery (%) 80 Membrane Array (Stage 1: Stage 2) 42:24 42: Train Flux, Stage1/Stage 2 (gfd) 12:12 12:8 High frequency of CIP Frequency of CIP (days) N/A 28 Pretreatment Pilot: Conclusions Lowest DOC removal by IX, requires regeneration (17, BV) New GAC removal higher than IX but non-regenerable media (24, BV) NF membranes: Highest removal by Hydracore50 Consistent DOC removal Specific flux decline due to organics fouling Flux restored after conventional/chlorine based CIP GAC and NF recommended for long-term piloting along with RO membranes Conceptual Design – Key Parameters NF as pretreatment for RO for organics removal “Loose” NF membrane (Hydracore50): High TOC removal Low inorganics rejection Rejection TDS 20% Calcium 30% Alkalinity 35% High NF recovery > 90% (92%) Need for low pH NF Feed! Same RO membranes as Goldsworthy Conceptual Design – Permeate Scaling ! Loose NF membrane allows Calcium and Alkalinity to pass to permeate Antiscalant rejected by membranes At high recovery, scaling can be present in permeate of tail elements Calculate LSI and CCPP in permeate, lower feed water pH Calcium Carbonate Scaling in Permeate Line Month Pilot Study – Objectives and Schedule Effectiveness of DOC removal by GAC and NF as pretreatment to RO system Confirm >90% recovery of NF system Document NF and RO membrane fouling, CIP frequency and success of cleaning Identify the need for lowering feed water pH Design parameters: flux, pressure, water quality Different NF and RO membrane performance Commissioning/Startup mid March 2024 Month Pilot Study – NF System Design Parameter Value Permeate Flow (gpm) Recovery 92% or larger Average Flux (gfd) 13.9 Concentrate Recirculation Membrane Make and Model Hydranutics Hyrdacore50 Element Surface Area (sf) Element D and L (in x in) 4×40 Stages Cartridge Filters 5 mm Interstage Booster Pumps yes.