Practical Approaches to Mitigate Reverse Osmosis (RO) Fouling and Reduce O&M Cost in Wastewater Treatment

Secret How to Reduce O&M Cost in Wastewater Treatment Energy Reduction Pretreatment & CIP Chemicals Membrane Replacement Energy Saving RO Elements Anti-Fouling RO Elements Durable RO Elements Low dP Feed Spacer Elements Compatible Biocides Avoid Oxidation (silica, boron, etc.) Energy Recovery Antiscalants Avoid Frequent CIP Lower Flux Design Optimize Chemical Dosing Avoid Physical Damage Fouling Prevention (MF/UF Pretreatment, MBR, RO System Design, Optimize O&M and Monitoring) © 2024 LG Chem, Ltd. Sato, Statistical Analysis of Foulant Composition from Membranes Collected from Reuse Applications, AWWA/AMAT MTC (2022) Energy Chemical (CIP) Membrane Replacement Increase DP Increase CIP Frequency Physical damage (high DP) Feed Pressure Increase Chemical damage (CIP) Permeate quality is deteriorated © 2024 LG Chem, Ltd. Secret How to Mitigate Organic Fouling Feed pressure increase is the indication of organic fouling in the system Organic Fouling: 1) Organic fouling is the irreversible flux decline due to the adsorption or deposition of dissolved or colloidal organic material. 2) In wastewater treatment, feed TOC or COD is very high Energy Chemical (CIP) Membrane Replacement Chemical damages due to Feed Pressure Increase Increase CIP Frequency aggressive CIP DP Increase (Organic colloids, Cake formation) Permeate flow is decreased. Secret Countermeasures: Carefully Select CIP Scheme Rigorous pretreatment can minimize adverse effects of organic fouling 1) Activated Carbon Filter (GAC), Powdered Activated Carbon (PAC) + UF 2) Oil Removal Filters 3) Synthetic Adsorbent 4) AOP: Ozone, O3/H2O2, UV/H2O2 However, these are burdens of CAPEX & OPEX The Easiest way to address organic fouling is to change CIP philosophy Normalized permeate flow has decreased 10% since startup or last cleaning Normalized salt passage has increased 10% since startup or last cleaning Normalized pressure drop from feed to concentrate has increased 15% since startup or last cleaning Normalized permeate flow has decreased 10% since stabilized or last cleaning Note: This kind of practice has been practiced in OCWD GWR M. Secret How to Design Low Flux RO Plants Low Flux Design Challenges Higher RO fluxes could actually reduce membrane fouling1 1) Improving hydraulics within the RO membranes 2) Maintaining better crossflow on membrane surface Needs to manage brine flow rates due to a concern on fouling Concentrate recycle may not be a good option Energy Chemical (CIP) Membrane Replacement Increase DP Increase CIP Frequency Chemical damage (CIP) Pressure may increase Scaling potential increase Permeate quality is deteriorated 1: G.