2015 Spring Conference Wilmington, NC April 13, 2015 Recent Advances in Membrane Technologies Peter D Adamo, Ph.D., P.E. 2014 HDR, Inc., all rights reserved.
Membrane Filtration Basics Recent Membrane Advances Operational Considerations Conclusions
Membrane Filtration Basics
Membranes vs. Granular Media Membrane filtration mechanism o Sieving/Straining Granular media filtration mechanism o Interception, collision, electrostatic attraction
Membrane Classifications (Pore Size, microns) Visible to naked eye Organic Macromolecules Colloids Bacteria Viruses Dissolved Salts Yeasts 10 Ultrafiltration Microfiltration Organic Compounds 1 0.1 0.01 0.001 0.0001 Red CryptosporidiumSmallest globule microorganisms Sand Filter ~ Polio virus Reverse Osmosis Nanofiltration
Membranes Classification (Driving Force) Vacuum (Submerged Membranes) o Compatible with Higher Solid Concentration o Can Be Used for Retrofit o Higher Energy Demand with Air Scouring o Noise, Corrosion & Evaporation Concerns
Membranes Classification (Driving Force) Pressure (Canister Membranes) o More Compact Design o High Solid Concentrations Problematic (> 100 NTU) for a Substantial Period of Time
Membranes Classification (Configuration) Polymeric Material (polyethersulfone (PES) or polyvinylidene difluoride (PVDF), others) Hollow Fiber Membranes (ID < 1.5 mm) Mostly used in MF & UF
Flux Cleaning Operational Considerations
Typical Pressure MF/UF System Permeate Air System B/W Water Cl 2 Finished Water Pumping Raw Water Source Supply Pump Pretreatment Particle Strainer Membrane Modules Backwash Waste/ Concentrate Finished Water Storage CIP System To Disposal
Submerged - Enhanced Coagulation Feed Water Coagulant Flash Mixer Pretreatment Permeate Pump Flocculation Chamber Bleed/Concentrate Air CIP System
Key Membrane Terminology Flux Flow across Membrane (gallons/sf/day, GFD) Temperature Corrected Flux (Standard 20-degree C) Transmembrane Pressure Water Pressure Change across Membrane, TMP) Specific Flux Flux/TMP Specific Permeability Filtrate flow/(membrane area * TMP) Integrity Testing (Pressure Decay Test, Bubble Point Test) LRV Log Removal Value
Membrane Cleaning Hydraulic Cleaning (every 15 to 45 minutes) Maintenance Wash (every 12 to 48 hours) Clean-in-Place (every 4 to 8 weeks) Water/Air Backwash Air Scouring Water Flushing Hypochlorite or citric acid Chemical recirculation Water Flushing Hypochlorite and Citric Acid Acid/Base Proprietary Chemicals (surfactants)
Membrane Fouling 16 14 Pressure - psi 12 10 8 6 4 Backwash Membrane Fouling Backwash & Chemical Cleaning Irreversable Fouling 2 0 0 50 100 150 200 250 300 Time
Recent Membrane Advances
Membrane Fiber Breakage Management When will fibers break? o During shipment, installation, o start-up and operation Why will fibers break? o Fibers dried out o Mechanical abrasion o Embrittlement o Abrading each other o Debris (raw water or backwash water) o Poor quality
Changes to Membrane Designs Materials of construction Configuration
Materials of Construction (Polymeric) Polymeric membranes o Improved chemistry for slightly better chemical resistance o Enhanced permeability o Larger diameter fibers with thicker walls to resist fiber breakage o Some vendors have changed potting materials Pall Microza GE Zenon Common Municipal Membrane Vendors Evoqua (Siemens) Memcor N Modules None really Recent Changes Thicker fibers for ZW-1000 New modules for ZW-1500 system Thicker fibers New potting materials
Advancements in Permeability and Abrasion Resistance Research shows membrane permeability of a membrane fiber directly correlates to abrasion resistance of the membrane fiber Evoqua N Fiber after 1 month of harsh, accelerated abrasion testing Little visible evidence to suggest degradation
Improved Fiber Morphology Drives System Improvements
Yuba City Water Treatment Plant - First Two Years of Operation Summary Membrane permeability remained high Treated water quality was excellent Pressure decay test values began to rise and log removal values fell Membrane integrity issues became a concern and Memcor was contacted Memcor began pilot testing in 2010 to gain understanding of problem
Pilot Testing Summary Pilot testing of the originally installed S10V modules conducted August 2010 through June 2011 Pilot unit experienced same integrity issues as the full scale system Cause identified as abrasion of the fibers by small particles such as diatoms, which compromised the outer surface of the fibers Pilot testing of the new S10N UF modules conducted August 2011 through June 2012 Pilot unit modules showed dramatic improvement in integrity TMP remained low and permeability high throughout the test period
Pilot Testing Results for N Module at Yuba City
Integrity Testing Results for N Module at Yuba City
And with the Resulting Permeability Enhancement a Reduction in Pumping Requirements
inge Multibore Membranes Polymeric MF membranes with large, multiple lumens in one fiber Improved physical strength (no fiber breakage) Tolerate high turbidity
What are Ceramic Membranes? Aluminum oxide porous base material Often used for difficult industrial applications System for potable water developed by NGK, Japan in 1990s Very expensive but nearly indestructible o Less pre-treatment requirements o ph, oxidant resistant Very low O&M costs o Membranes last 50+ years
Ceramic versus Polymeric Monolith Variable Ceramic Polymeric Flux (gfd) 100-220 30-85 Turbidity (NTU) < 1,500 <100 TSS (mg/l) < 3,000 < 200 TOC/DOC (mg/l) < 100 < 30 Coagulant (mg/l) < 200 < 30 Recovery (%) > 98 > 96 1,000 s of HF lumens Filtration Interval (hrs) 1-2 0.25 0.67 CEB Interval (day) 2 4 1 CIP Interval (month) 6 1
Ceramic Membrane process train requires less pretreatment ClO 2 or KMNO 4 Coagulant Chlorine Deer Creek PS PAC Influent Tank (Aeration/PAC) Flocculation Ceramic Membranes BWW GAC UV (Future) Clearwell Effluent
35 Ceramic Membranes are Robust and Becoming more Cost Effective Ability to handle high turbidity, PAC and coagulants 20-year membrane warranty New Dutch design improves economics
Pall Kruger Siemens Membrane Pre-Selection Procurement Bid Tabs Line Item Costs by Membrane Manufacturer Total Membrane System Capital Cost Total Membrane Plus Pretreatment Capital Cost (Tax Included) Total of Annual Operating Costs (Present Worth) 20-Year Present Worth of Annual Cost For Membrane Replacement Pretreatment Present Worth O&M Total 20-Year Present Worth Total $1,383,828 $3,088,188 $1,172,569 $2,078,658 $3,170,125 $1,867,399 $1,729,076 $737,577 $1,667,222 $260,211 $265,139 $516,072 $493,206 $362,067 $499,461 $4,561,150 $4,534,908 $4,550,154
Take Away Points Membranes Offers a Wide Range of Applications Membrane is a Mature Technology but New Advances Every Year Industry Moving more Towards Plug and Play A Successful Membrane Operation Depends on o The Selection of an Appropriate System o Proper Pretreatment for water supply and technology
Questions? 2014 HDR Architecture, 2014 HDR, Inc., all rights reserved.