Depth Filtration with Microfiber Cloth Enhances Performance of Ultrafiltration as Pretreatment to Seawater Desalination Systems Emerging Technologies in Filtration October 6, 2015 David Holland, Terence K. Reid, Aqua-Aerobic Systems, Inc. Diane Gatza, West Basin Municipal Authority
Presentation Outline Problem Introduction Project Background Methods Results Summary
Sea Water Reverse Osmosis The impact of ineffective pre-treatment Net driving pressure ΔP across vessel Cleaning Frequency Operational Costs RO membrane Life Normalized permeate flow Plant availability Reliability
Basis for Study What if Cloth Media Filtration? Microfiber Media Technology Extensive application in Water Reclamation Market High Solids (>100 mg/l) High Flux (17,000 L/m2/hr) Low Energy (<.01 kw/m3)
Desalination Pre-Treatment Study Research Objectives 1. Investigate performance using microfiber cloth on sea water 2. Evaluate performance benefits of depth filtration 3. Identify Operation & Maintenance (O&M) benefits of prefiltration with microfiber cloth 4. Assess design optimization considerations
Sea Water Pre-Treatment Study Where to Test Rockford, IL?
West Basin Municipal Water District Ocean-Water Desalination Demonstration Facility and Water Education Center
Open Sea Intake Redondo Beach, CA
Source Water Intake 1,600 ft Off Shore WEST BASIN MUNICIPAL WATER DISTRICT OCEAN-WATER DESALINATION DEMONSTRATION FACILITY AND WATER EDUCATION CENTER (and SEA LAB)
Source Water Intake Wedgewire Screen, 8 dia. Pipe
Sea Water Characteristics Open-intake Total Suspended Solids from 5 to 250 mg/l o 89% of particles smaller than 10 µm Total Dissolved Solids from 30 to 45 g/l Biochemical Oxygen Demand: 50 to 75 mg/l ph: 7-8 Presence of Microorganisms Algae levels less than 5 µg/l and averaged 0.6 µg/l Total Hardness: 500 to 2,000 mg/l Seawater Desalination Plant Operations, Maintenance and Trouble shooting. By Rajesh Mon
Sea Water Pretreatment Study Process Flow Diagram Feed Tank Cloth Media Filter UF-1 Collection Tank 100µm Strainers UF-2 Return to Ocean Seawater Intake Screen
TSS Removal Expected Performance Filtration Spectrum - µm 0.001 0.01 0.1 1.0 10 100 1000 Ions Salts Virus Crypto Giardia Bacteria Colloids Nanofiltration Microfiltration Disc Screens RO Ultrafiltration Rapid Gravity Sand Filters Cloth Media Filtration
Filtration Removal Mechanisms Surface Mechanism Depth Filtration
Depth Filtration Removal Mechanisms Straining Surface Mechanism Sedimentation Impaction Interception Depth Filtration Adhesion Flocculation
Cloth Media Filtration General Structure Pile Construction Polyester Support Backing
Cloth Media Filtration True Depth Filtration Rapid Sand Filter D=d 10 =0.6 mm PES-14 Microfiber D 0.007 mm L=300-600 mm L=3-5 mm When wet L/D = 500-1000 L/D = 425-715
Cloth Media Filtration Aqua MiniDisk Chlorine-resistant polyester Outside-In, Dead-End 1 m 2 disk 5 µm rating (nominal)
Cloth Media Filtration Nominal 100,000 GPD Pilot
Ultrafiltration Aqua Multi-Bore Membranes (7) capillaries in one fiber Inside-Out, Dead-End 4.0 mm O.D., 0.9 mm I.D. 0.02 µm pore size (nominal)
UltraFiltration Two Independent 2,160 gpd Trains dizzer (2.5m 2 ) Train 1 of 2 Master Control Skid
Sea Water Pre-Treatment Study Daily Testing Schedule Sample Location 1. Source Water 2. Filter Effluent 3. UF-1 4. UF-2 Parameter Type Responsibility Volume (ml) Mon Tue Wed Thu Fri Turbidity Composite/Grab AASI x x x x x UVT Composite/Grab AASI x x x x x SDI 15 Grab AASI x x x x x PSD Grab AASI x x x x x TSS Composite Weck Labs 1000 x x x x x TDS Grab Weck Labs 500 x Chlorophyll Composite Weck Labs 100 x Chlorides Grab Weck Labs 250 x
Silt Density Index Cloth Media and Membranes Effluent SDI with pre-filtration was 14.3% less than without pre-filtration
System Performance Daily Average Turbidity > 82% reduction overall
Filter Performance Effect on Membranes Pre-filtration provided 14.1% more flow
Membranes Importance of Pre-Treatment 100µm Screen Captured Material Train 2 had to be taken offline every 3 to 5 days for strainer cleaning
Membranes Effects of Pre-Filtration after 50 days Multi-Bore with Pre-Filtration Multi-Bore with only 100µm Screening During high solids loading, Train 2 shut down on high TMP
Membrane Performance Energy Costs
Desalination Pre-Treatment Study Summary UF pretreatment permits extended RO operation Microfiber improved SDI performance by 14% Pre-filtration with microfiber eliminated abrasive sand to UF Feed pump energy dropped about 20% with pre-filtered feed Microfiber and UF provide cost-effective RO pre-treatment
Thank You Acknowledgements: Rich Nagle, Diane Gatza