Basics 101 Paul J. Delphos, Black & Veatch 757-456-5380, ext 12 - PowerPoint PPT Presentation

Membrane Filtration Basics 101 Paul J. Delphos, Black & Veatch 757-456-5380, ext 12 VA AWWA Plant Operations Committee Operators Conference Virginia Beach, VA May 19-21, 2014

Presentation Overview  Market Assessment  Membrane Theory  Example Applications

What’s The Big Deal??  1 st Significant MF/UF System in North America in 1993 (Saratoga, CA – 3.6 mgd)  Over 250 plants now on-line  Historically, small facilities (i.e. < 1 mgd) for small clients  Trend is to fewer, but larger facilities  Minneapolis – 70 and 90 mgd  Singapore – 72 mgd  Lancaster – 24 mgd, expandable to 36 mgd

Desalination Is Growing As Well Ca Capacity ity (mg (mgd) Numb Number er of of Inst Installa allation tions EDR EDR SWRO SWRO BWNF BWNF 15 44 92 20 71 110 110 250 BWRO BWRO

Other Perspectives  Membrane System Sales To Reach $9 Billion by 2008 (Mcllvaine Company, 2006)  $6.8 Billion in 2005 (33% Top End Growth) Nearly All New Revenues Are  Includes Desalination and Low-Pressure Membranes From New Projects  Microfiltration from $1.9 to $2.5 Billion  Only 2.5% of US Drinking Water is Treated with MF/UF Membranes  Expected to Reach $10 Billion by 2010

What Are Membranes? Submerged/Vacuum Cartridge/Pressure

Membrane Theory Overview Organic macromolecules Organic compounds Colloids Viruses Dissolved Bacteria salts Pollens Yeasts 0.0001 0.01 0.001 10 1 0.1 100 um Reverse osmosis Smallest Polio hair visible Giardia Nanofiltration microorganisms virus to naked Ultrafiltration eye Microfiltration Sand filter

How Do Membranes Work? Membranes can remove anything that is larger than its pores.

Giardia Cryptosporidium

Membrane Failure Mode • Membranes fail incrementally – one fiber at a time. • Statistically, individual fiber breaks are insignificant to the overall microbial water quality.

On-Line Integrity Testing Bubble point Air pressure Direct Measures Sonic wave Bio-challenge Turbidity Indirect Particle Measures monitoring The accepted standard is moving towards continuous (safety interlock) turbidimeters. Detection limit  0.001 NTU.

Some Key (and New) Terms OLD NEW  Overflow Rate  Flux  Declining Rate  Flux Decline  ????  Specific Flux/Permeability  Backwash  Reverse Filtration  Filter Breakthrough  Membrane Integrity  Filtered Turbidity  Log Removal  Backwash Volume  Recovery  Filter Head Loss  Transmembrane Pressure

Piloting Overview  Number of Systems?  Regulatory Acceptance  Verified Membrane Applicability  Basis of Design  Operator Experience

Data Evaluation  Flux  Recovery/Waste Disposal  Cold Water TMP Issues  Daily Cleans vs. Monthly Cleans City of Lancaster MF Pilot 60 12  Turbidity 50 10 40 8  TOC/UV254 gfd psi 30 6 20 4  Particle Counts – log removal 10 2  MIT’s 0 0 Nov Jan Mar Apr Jun ZW 500-C, Sp Permeability @ 20°C ZW 500-C, Instantaneous Flux ZW 500-C, Average TMP

Membrane Fouling Mitigation Measures Causes  Chlorination  Biological  Cross-Flow  Organic/Colloidal/  Backwash Particle  Chemical Cleaning  Chemical Scaling  Additives/Coagulants  Membrane Compression  Pretreatment  Synthetic Polymers

Membrane Fouling Directly Impacts Costs  Fouling is the limiting factor in most membrane system designs  By removing organics, or natural organic matter (NOM), membranes become much more effective  Coagulation removes NOM by:  Charge Neutralization  Adsorption To Precipitates  With membranes, coagulation is geared to TOC removal  The “cake layer” on pressure systems improves TOC removal

Membrane Fouling 16 14 12 Backwash & Chemical Cleaning Pressure - psi 10 Backwash 8 6 Irreversable Membrane Fouling Fouling 4 2 0 0 50 100 150 200 250 300 Time

Membrane Fouling Example Before and After Backwashing 22 (1) (3) (4) (5) (6) (7) (8) (2) (1) Vacuum increase due to flux increase corresponding to re-adjusted permeate flow. 20 (2) Rain event - organics/color raw water spike, alum dosage not increased to compensate. 18 (3) High vacuum alarm --> tank dumped, re-started with higher alum dosage. 16 (4) Caustic dosing interrupted. (5) High vacuum alarm --> clean 14 (6) Clean - vacuum recovers to 4"Hg. TMP (psi) (7) Ferric dosing interrupted? (Floc tank pH = 6.8). (8) High vaccum alarm --> system off for 6.5 hours and 12 then re-started. 10 8 6 4 2 0 22- 24- 26- 28- 30- 1- 3- 5- 7- 9- 11- 13- 15- 17- 19- 21- Jul Jul Jul Jul Jul Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Before BP Vacuum Date After BP Vacuum

SEM Images of Fouling Layer (UF Membrane, CA, 100k MWCO)  Clean Membrane  Growth of NOM Fouling Layer Over Time  Effect of Backwashing on Fouling Layer  HIOP Cake Layer with Sorbed NOM  Effect of Backwashing on Cake Layer

Clean Membrane, CA 100k MWCO

Dead-End Filtration – 30 Minutes

Dead-End Filtration – 1 Hour

NOM Layer Before Backwash

NOM Layer After Backwash

Coagulant Aid (HIOPS) + NOM Before BW

Coagulant Aid + NOM After BW

Potential Applications For Low Pressure Membranes  Turbidity/pathogen/TOC removal on raw water  Replace conventional filters following flocculation/sedimentation  Treatment of conventional filter backwash water  Pretreatment ahead of RO or NF membrane system  Fe/Mn removal following oxidation  Arsenic Removal  Pathogen removal following conventional treatment

Typical Pressure MF/UF System Permeate Cl 2 Finished Air System Water B/W Water Pumping Supply Particle Pump Strainer Raw Membrane Finished Water Modules Water Backwash Waste/ Source Storage Concentrate To CIP System Disposal

Submerged - Enhanced Coagulation Coagulant Permeate Pump Flash Mixer Feed Water Bleed/Concentrate Flocculation Chamber High solids concentration in tank Air

Pressure vs. Submerged Filtered Filtered Filtered Water Water Water 5 to 50 psi Solids and Liquids Under Pressure

Pressure vs. Submerged Pressure Submerged  Advantages  Advantages Skid-mounted Use of existing tanks   Easy to install Larger systems   Great for small systems Low energy   Easy competition Great for poor raw water   High Fluxes Low fouling   Backwash recovery  Disadvantages   Disadvantages Larger systems  Fouling/energy Modifications can be   expensive Low Dosages of Coagulant  Low flux rates  Backwashing  Concentrate with fiber  breakage

Outside-In vs. Inside-Out Filtered Filtered Filtered Water Water Water 5 to 50 psi Solids and Liquids Under Pressure

Outside-In vs. Inside-Out Outside-In Inside-Out  Advantages  Advantages  Submerged option  Great with clean water  Larger active area  Cross-flow operation minimizes irreversible fouling  Higher solids  Disadvantages  Lower Pressure  Recirculation required  Dead-end flow  Higher flux requirements  Disadvantages  High fouling potential  Lower comparative flux  Increased energy  Irreversible fouling?

MF/UF Modes of Operation Cross-flow Conventional (Dead-End) Feed Feed membrane filter membrane filter

Principal Suppliers of Low Pressure Drinking Water Membrane Systems Membrane System Suppliers Membrane Module Suppliers  Pall Corporation (MF/UF)  GE (UF  GE - Zenon Environmental, Inc.  Evoqua (MF) (MF/UF)  Dow (UF)  Evoqua Water Technologies  Toray (UF) (Siemens - US Filter/Memcor   Hydronautics, Inc. (UF) (MF) )  Asahi (MF)  Wigen, Inc. (UF)  H2O Installations  WesTech  Kruger

Primary Elements of Low-Pressure Membrane System  Feed water/vacuum pumps  Ancillary pumps  Automatic screens  Skids with PLC-based controls  Clean-in-place (CIP)  SCADA system/PLC network  Air delivery system  Waste holding tank/pumps  Neutralization tank/pumps

Roanoke, VA – Crystal Spring  Spring has been used for drinking water since 1880s  In summer of 2000, VDH determine spring was GWUI as coliform counts increased  Virginia Membrane Plants - Memcor - 14 Koch - 1  VDH “Approved” Other Membrane Manufacturers  Competitive Bid Between Memcor and Pall

Crystal Spring WTP - Design Conditions  5 mgd firm (one rack out of service)  99.5% recovery (backwash recovery)  No pretreatment (chlorine was recommended by Pall)  30 day cleaning cycle  60 minute backwash frequency  10-year membrane warranty  Performance testing for successful bidder

Crystal Spring WTP - Bid Summary Cost US Filter - Pall Component Memcor Capital $1,600,317 $1,960,000 O&M (20-yr $436,625 $303,176 PW) Membrane Repl. $357,822 $429,130 (20-yr PW) Total 20-yr PW $2,394,764 $2,692,306

Performance Testing Operating Results  Flux: 34.8 gfd @ 15 o C  TMP: 1 psi increase per 15 to 18 days  Average TMP: 10.5 psi  Backwashing: 150 sec/90 minutes  97% Recovery  CIP Interval of Over 90 days