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Microfiltration / Reverse Osmosis The 1-2 Punch for Water Treatment
Presented by: Don Burgess DWG Process Supply Ltd.
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R A N G E S O F F I L T R A T I O N P R O C E S S E S
Material Sizes R A N G E S O F F I L T R A T I O N P R O C E S S E S CLOTH & DEPTH FILTERS MICROFILTRATION MEMBRANE TYPE ULTRAFILTRATION SCREENS & STRAINERS NANO- FILTRATION REVERSE OSMOSIS LATEX EMULSIONS METAL IONS RED BLOOD CELLS OIL EMULSIONS HUMAN HAIR RELATIVE SIZE OF COMMON MATERIALS VOC’S, PCD, SUSP. OIL VIRUS DISSOLVED ORGANICS PAINT PIGMENT AQUEOUS SALTS CARBON BLACK BACTERIA SAND ATOMIC RADII Giardia Cyst Cryptosporidium Oocyst PROTEINS/ENZYMES PARTICLE SIZE (MICRONS) PARTICLE SIZE , , , (ANGSTROMS) APPROXIMATE , ,000 MOLECULAR WT. Source: GE Water
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Filtration Processes Microfiltration / Ultrafiltration
Removes turbidity Provides barrier to Crypto/Giardia Backwashable “Surface Water” “Spaghetti removes Solids” Reverse Osmosis / Nanofiltration Removes dissolved compounds Typically can not backwash Fouled by turbidity “Ground Water” “Layered removes Liquids”
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Microfiltration
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How Small is Small? Membrane Pore Sizes – 0.01 to 0.2 micron
Pencil Dot (40 µm) Large Siliceous Particle (20 µm) E-Coli (.45 µm) Giardia Cyst ( µm) Cryptosporidium Oocyst (2 - 5 µm) [Anthrax Spore] Typical Bacterium (0.2 µm) Membrane Pore Sizes – 0.01 to 0.2 micron
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Why Microfiltration? Turbidity and Microbiology removal with no chemistry Turbidity < 0.1 NTU 0.02 to 0.04 NTU Cryptosporidium > % Removal Giardia > % Removal TOC / Colour removal Chemical precipitation Coagulation with Alum / acid / PAC Removal of precipitate with membrane
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Pressure Membranes MF Fiber = 0.1 micron
PVDF - Oxidant Resistant (Chlorine, Ozone & Chlorine Dioxide) Outside – In Rack Mounted Vertically Inlet Section Source: Pall Canada
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Immersed Membranes UF Fiber = 0.035 micron Composite Outside – In
Vacuum Mounted in Below or Above Grade Tanks Source:
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How the Pressure System Works
Microza® hollow fiber systems have three modes of operation: Filtration Regeneration Clean-In-Place (CIP)
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Forward Water Production
Filtrate Feed Pump Excess Recirculation MF/UF Module
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Reverse Filtration MF/UF Module Pump To Drain Chlorine Optional
Filtrate To Drain Chlorine Optional
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Why Reverse Filtration?
TMP increases with time TMP Longer cycle with Reverse Filtration Time
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Clean-In-Place (CIP) Chemical wash of the membranes to remove foulants and restore flow capacity. Chlorine and caustic – Remove organics Citric acid – Remove inorganics
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Pressure System (35 MLD - Pall)
Source: Pall Canada
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Immersed Wastewater System (Zenon)
Source:
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Town of Whitecourt 4.8 to 16 MLD
1 of 2 valve racks Ultimate capacity of 16 MLD Dummy modules for startup Initial installed modules for 4.8 MLD
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Modular System 1.3 to 2.0 MLD
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Nobleford Pilot Raw water 2 to 7 NTU 3 mg/L TOC Treated Water
0 to 1 particles 50% TOC red.
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Vernon Pilot Turbidity < 0.1 NTU Particle counts – 0 to 1
Successful operation w/o pretreatment 65% TOC red. w/ pretrtmnt
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MF Test Results Site 1 Site 2 Treated Water Raw Water Turbidity (NTU)
1 to 7 10 to 25 <0.02 TOC (mg/L) 9 to 11 10 to 15 4 to 6 Colour (TCU) 5 to 40 23 to 40 < 5 Chemical Dosages Alum (mg/L) 100 75 to 100 PAC (mg/L) 10 13
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MF Membrane Technology Benefits
Exceeds Environmental Treatment Standards Consistent treatment quality Modular, Compact and Cost Saving System Configurations Some Membranes Warranted for 10 Years Automatic Integrity Testing On-Line Technical Support and System Diagnosis
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Reverse Osmosis / Nanofiltration
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RO / Nano filtration Removes dissolved compounds Non-backwashable
Max 0.5 to 1 NTU Max SDI = 3.0 “Ground Water” “Layered removes Liquids”
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Applications Ground water treatment TDS Hardness
Metals such as arsenic GWUI Surface water Organics
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Pre-Treatment for Nano/RO
Pre-Filtration for Solids Removal Raw Water Nano / RO SDI < 3 Permeate Microfiltration Concentrate Pre-Oxidation for Iron/Mg Removal Raw Water Nano / RO Pre-oxidation Filtration Permeate Concentrate
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Pre-treatment Required Cartridge Filters (5 micron)
Antiscalant (chemical) As Needed Multi Media Filtration (Iron Removal) MF/UF (suspended solids, turbidity)
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Post-Treatment Required pH adjustment (caustic, lime) Disinfection
As Needed Degasifier
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RO or Nano Reverse Osmosis
Low energy membranes provide high efficiency removal Removes 97 to 99% of all dissolved compounds Blend w/ raw water to meet guidelines and restabilize treated water Nanofiltration Removes 60 to 80% of dissolved compounds Use for GWUI as treat entire flow stream “Softening” filter Specially formulated membrane to resist organic (TOC) fouling
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Pros and Cons Pros Ease of operation Superior water quality
Reduced footprint Membrane elements are standardized Modular units Cons Higher energy costs High waste volumes – 60 to 80% recovery
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System Operation Feed water boosted to approx 175 psi to drive flow through membranes Water is clarified as it passes through membrane to produce “permeate” Rejected compounds are concentrated in waste water referred to as “concentrate” Run at one flow rate – “On/Off” operation
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Flow Schematic
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Feed Water Conditions Pressure - 30-60 psi Turbidity - <1 NTU
Silt Density Index - <4 for 15 minute test
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Design Considerations
Pretreatment SDI Hardness Iron / Manganese System Recovery Keep compounds within saturation limits Antiscalants
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Full Scale Systems
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Meander River – 800 m3/D Blending 80% RO permeate with 20% raw water
Reducing TDS from 2000 to 500
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1,630 M3/Day
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Pilot Testing Treating surface water for TOC reduction
Slow sand filtration pretreatment Reducing TOC from 10.5 mg/L to <0.5 Key issue – minimize organic fouling of membrane
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Is It Worth It? RO/Nano provides specific function
Often replaces 2 or 3 other processes Sometimes the only process that will work It is worth looking after your system
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Process Applications
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Remember Microfiltration / Ultrafiltration RO / Nano “Surface Water”
Turbidity and particle removal Crypto/Giardia barrier Backwashable “Spaghetti removes Solids” RO / Nano “Ground Water” Dissolved compound reduction Do not even think of backwashing “Layered removes Liquids”
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Contaminants Surface Water Turbidity Crypto/Giardia Iron/Mang/Arsenic
Organics Hardness Ground Water TDS Hardness Iron/Mang/Arsenic Organics Turbidity
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Treatment Options Contaminant Conventional Process Membrane Process
Turbidity Floc/Coag/Clarifier /Filter MF Crypto/Giardia Iron/Mang/Arsenic Chem Precip / Mang Greensand Chem Precip and MF or RO Hardness Lime softng/Recarb / Filter RO Organics Oxidation and GAC TDS Not readily available
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System Assessment Look at compounds that are process dependant, and then add other processes as required for remaining compounds
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Surface Water Contaminant Membrane Process Turbidity MF Crypto/Giardia
Iron/Mang/Arsenic MF + Chem Precip Hardness MF + RO Organics MF + Enh Coag, or RO
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Ground Water Contaminant Membrane Process TDS RO Iron/Mang/Arsenic
RO or Chem Precip +MF Hardness Organics Turbidity MF GUDI
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Treatment Quality Turbidity Crypto/Giardia Iron/Mang/Arsenic Organics
Hardness TDS < 0.1 NTU Avg 1 to 4 particle counts Below guideline limits < 2 mg/L < 100 < 500
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1. MF Feed to NF for Organics
Process Flow River water Upflow clarifier Microfiltration Nanofiltration for organics reduction
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Results - MF to NF for Organics
Parameter Raw Water Clarifier Effluent MF Perm NF Perm TOC (mg/L) 13.1 3.5 3.6 <0.5 Iron (mg/L) 0.32 <0.06 Manganese (mg/L) 0.039 0.077 0.076 <0.004 TDS 120 170 160 <10 Hardness (mg/L) 96 110
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2. MF-NF for Organics Redn
River water source Sedimentation clarifier Microfiltration Transfer tank NF for organics reduction
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Results – MF-NF for Org Redn
Parameter Raw Water MF Feed MF Perm RO Perm Turbidity 2 4.5 0.010 TDS 255 263 264 149 Hardness 198 176 195 88 TOC 15.6 12.3 12.0 0.05
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3. MF-NF for Turb, Organics, Hardness
Process Flow River water Raw water pond Microfiltration for turbidity reduction and crypto / giardia barrier Nanofiltration for organics / hardness reduction
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Results - MF to NF Parameter Raw Water MF Perm NF Perm TOC (mg/L) 15.8
12.4 <0.1 Turbidity (NTU) 0.86 0.02 Manganese (mg/L) 0.005 <0.002 TDS 751 749 <5 Hardness (mg/L) 527 530 1.0
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Summary The 1-2 Punch of MF / RO’s, can treat most common contaminants in water. Reduced number of processes, generally results in smaller footprint. Effluent quality from membrane treatment is consistent.
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Questions
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