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??

 1st 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

SWRO BWRO EDR BWRO SWRO EDR BWNF

250

20 15

71 110 92

44

110

BWNF

Numb Number er of

• f Inst

Installa allation tions Ca Capacity ity (mg (mgd)

Other Perspectives

 Membrane System Sales To Reach $9 Billion by

2008 (Mcllvaine Company, 2006)

 $6.8 Billion in 2005 (33% Top End Growth)  Includes Desalination and Low-Pressure Membranes

 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

Nearly All New Revenues Are From New Projects

What Are Membranes? Cartridge/Pressure Submerged/Vacuum

Membrane Theory Overview

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

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

Giardia Cryptosporidium

• Membranes fail incrementally – one fiber at a time.
• Statistically, individual fiber breaks are insignificant

to the overall microbial water quality.

Membrane Failure Mode

Bubble point Air pressure Sonic wave Bio-challenge Turbidity Particle monitoring

Direct Measures Indirect Measures

The accepted standard is moving towards continuous (safety interlock) turbidimeters. Detection limit  0.001 NTU.

On-Line Integrity Testing

Some Key (and New) Terms

NEW

 Flux  Flux Decline  Specific Flux/Permeability  Reverse Filtration  Membrane Integrity  Log Removal  Recovery  Transmembrane Pressure

OLD

 Overflow Rate  Declining Rate  ????  Backwash  Filter Breakthrough  Filtered Turbidity  Backwash Volume  Filter Head Loss

Piloting Overview

 Number of Systems?  Regulatory Acceptance  Verified Membrane

Applicability

 Basis of Design  Operator Experience

Data Evaluation

City of Lancaster MF Pilot

 Flux  Recovery/Waste Disposal  Cold Water TMP Issues  Daily Cleans vs. Monthly

Cleans

 Turbidity  TOC/UV254  Particle Counts – log removal  MIT’s

Membrane Fouling

Causes

 Biological  Organic/Colloidal/

Particle

 Chemical Scaling  Membrane Compression  Synthetic Polymers

Mitigation Measures

 Chlorination  Cross-Flow  Backwash  Chemical Cleaning  Additives/Coagulants  Pretreatment

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

2 4 6 8 10 12 14 16 50 100 150 200 250 300

Time

Pressure - psi

Membrane Fouling Backwash Irreversable Fouling Backwash & Chemical Cleaning

Membrane Fouling Example

Before and After Backwashing

2 4 6 8 10 12 14 16 18 20 22 22- Jul 24- Jul 26- Jul 28- Jul 30- Jul 1- Aug 3- Aug 5- Aug 7- Aug 9- Aug 11- Aug 13- Aug 15- Aug 17- Aug 19- Aug 21- Aug

Date TMP (psi)

Before BP Vacuum After BP Vacuum

(1) Vacuum increase due to flux increase corresponding to re-adjusted permeate flow. (2) Rain event - organics/color raw water spike, alum dosage not increased to compensate. (3) High vacuum alarm --> tank dumped, re-started with higher alum dosage. (4) Caustic dosing interrupted. (5) High vacuum alarm --> clean (6) Clean - vacuum recovers to 4"Hg. (7) Ferric dosing interrupted? (Floc tank pH = 6.8). (8) High vaccum alarm --> system off for 6.5 hours and then re-started.

(1) (2) (3) (5) (4) (6) (7) (8)

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

 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

Potential Applications For Low Pressure Membranes

Typical Pressure MF/UF System

Air System B/W Water Cl2 Raw Water Source Supply Pump Particle Strainer CIP System Membrane Modules Backwash Waste/ Concentrate To Disposal Finished Water Storage Finished Water Pumping Permeate

Submerged - Enhanced Coagulation

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

Filtered Water

5 to 50 psi

Filtered Water Filtered Water Solids and Liquids Under Pressure

Pressure vs. Submerged

Pressure vs. Submerged

Pressure

 Advantages



Skid-mounted



Easy to install



Great for small systems



Easy competition



High Fluxes

 Disadvantages



Larger systems



Fouling/energy



Low Dosages of Coagulant



Backwashing

Submerged

 Advantages



Use of existing tanks



Larger systems



Low energy



Great for poor raw water



Low fouling



Backwash recovery

 Disadvantages



Modifications can be expensive



Low flux rates



Concentrate with fiber breakage

Filtered Water

5 to 50 psi

Filtered Water Filtered Water Solids and Liquids Under Pressure

Outside-In vs. Inside-Out

Outside-In vs. Inside-Out

Outside-In

 Advantages

 Submerged option  Larger active area  Higher solids  Lower Pressure  Dead-end flow

 Disadvantages

 Lower comparative flux  Irreversible fouling?

Inside-Out

 Advantages

 Great with clean water  Cross-flow operation minimizes

irreversible fouling

 Disadvantages

 Recirculation required  Higher flux requirements  High fouling potential  Increased energy

MF/UF Modes of Operation

Conventional

(Dead-End)

Feed

membrane filter

Cross-flow Feed

membrane filter

Principal Suppliers of Low Pressure Drinking Water Membrane Systems

Membrane System Suppliers

 Pall Corporation (MF/UF)  GE - Zenon Environmental, Inc.

(MF/UF)

 Evoqua Water Technologies



(Siemens - US Filter/Memcor (MF) )

 Wigen, Inc. (UF)  H2O Installations  WesTech  Kruger

Membrane Module Suppliers

 GE (UF  Evoqua (MF)  Dow (UF)  Toray (UF)  Hydronautics, Inc. (UF)  Asahi (MF)

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

Performance Testing Operating Results

 Flux: 34.8 gfd @ 15oC  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

Crystal Spring WTP – Performance Testing Criteria

 Flux:

34.6 gfd

 Recovery:

95% w/o backwash recovery 99.5% w/ backwash recovery

 Backwash:

150 sec/60 min

 CIP Interval:

30 days

 Chemical Consumption Limits  Power Consumption Limits  100 – day Duration

Performance Testing Water Quality Results

 Turbidity

 Raw: 0.06 NTU to 0.14 NTU  Permeate: 0.02 NTU (lower limit of turbidimeter)

 Particle Counts

 Raw: 25 to 75 >2 um/mL  Permeate:

2 to 8 >2 um/mL

 1 to 1.5 log removal

Pilot Turbidity Spike Data

9.8 9.9 10 10.1 10.2 10.3 10.4 10.5 10.6 14:15 14:40 15:11 15:39 15:44 16:12 16:23 16:40 16:46 Time TMP (psi) 5 10 15 20 25 30 35 Feed Turbidity (NTU) TMP Turbidity ``

Permeate <0.023 NTU

Crystal Spring WTP

Spring, Pumps and Screens

Installed Membrane System

Installed Membrane System

CIP System

Membrane System Piping

Operating Data - Flow

0.00 1.00 2.00 3.00 4.00 5.00 6.00 December January Febuary March April May June July August Month Flow (mgd)

Operating Data - Flux

20 22 24 26 28 30 32 34 December January Febuary March April May June July August

Month Flux (gfd)

Operating Data - Recovery

90% 91% 92% 93% 94% 95% 96% 97% 98% 99% 100% December January Febuary March April May June July August Month Recovery (%)

Operating Data - Turbidity

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 December January Febuary March April May June July August Month Turbidity

Operating Data - TMP

5 10 15 20 25 30 Febuary March April May June July August Month TMP (psi) Filter 1 Filter 2 Filter 3 Filter 4 Filter 5

Other 1st Year Results

 CIP Interval: 1 per 6 months  Zero Fiber Breaks (over 10 million fibers)  Manpower Reqt’s: < 2 h/d, 5 d/wk  “The Plant Runs Itself” – Greg Belcher, City of Roanoke

Chesapeake, Virginia

 7.5 MGD Submerged Membrane Plant  Dedicated in April 2006  Raw Water TOC – 4 to 6 mg/L  Raw Water Turbidity 25 to 50 NTU  Coagulant Feed – 20 to 25 mg/L  Coagulant pH – 5.5 to 6.0

Chesapeake TOC Data Sample May 8 May 22 May 30 Jun 7 Raw 4.10 4.22 4.50 4.29 Permeate 1.36 1.77 1.88 1.82 % Reduction 67% 60% 58% 58% Alum Dose (mg/L) 25 20 20 20 pH 5.46 5.87 5.90 5.85

Raw Water Strainers

Pretreatment Tanks

Membrane Tanks

Multiple Membrane Trains with Crane

Lancaster Pennsylvania

 24 and 12 MGD WTPs  Regulatory Drivers



LT2 ESTWR (Crypto Removal)



Stage 2 D/DBP Rule



Future Rules

 Conventional Facilities  Zenon 500 Upgrade  Direct vs. Clarified Feed

Lancaster, PA

 24 and 12 mgd Membrane Facilities  Two of the Largest on the East Coast  Includes State-of-the-Art Thickening Process  Include Two-Stage Membrane Treatment with UV

Disinfection

 Over $70 million  Great client reference

Lancaster, PA - Pilot Operation

Raw

 Pre-screened River

Water

 Alum Feed

 Acid

 15 minute floc  99.7% recovery  PACl later

Clarified

 Post-clarification  Daily Cleans vs.

Monthly Cleans

 95% Recovery  EC Jar Tests

Data Evaluation - Permeate

Parameter Raw MF/UF Clarified MF/UF EC Alum Dose 50 mg/L 30 mg/L 70 mg/L Turbidity <0.03 NTU <0.03 NTU <0.3 NTU Particle Cts (#/mL) <10 <10 NA TOC Removal 35-50% 15-25% 35-50% DBP’s 1 3 2

Lancaster – Other Findings

 Raw will work on flashy river water

 Need to pay attention closely during flashy events

 Daily cleans – Helped when working  Heated daily cleans/backwashes helped short-

term

 High fluxes can be unstable

Lancaster – Other Findings (cont.)

 Clarification process is not necessarily an

additional barrier or a reduction of risk

 Constructability and retrofit costs can be very

difficult to quantify

 Cold water (<3oC) was difficult  PACl worked best in cold water  Raw water membrane costs (capital and

• perating) – 30 to 40% above clarified

Swansea Water District, MA

 First Desalination Project on East Coast for HDR  1.5 mgd Desalination plus 1 mgd Fe/Mn

Groundwater Membrane Plant

 Upon completion, will be the 2nd surface water

desalination facility north of Florida

 Pall/Toray

Summary

 Membranes are here and will become a more

technology in the future.

 Membranes are a great particle removal

mechanism

 Significant fractions of organics are not normally

removed with MF/UF, but when coupled with a coagulant, removals are equal to or better than conventional facilities

 Membranes will work on all waters, cost is just the

major factor – so, pick the correct system!!!!!!

For more information, contact: Paul J. Delphos DelphosP@bv.com 757-456-5380, ext 12

Membrane Filtration Basics 101