Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage
-
Upload
ezra-james -
Category
Documents
-
view
22 -
download
1
description
Transcript of Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage
![Page 1: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/1.jpg)
Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage
Christopher Barnes, P.E., City of Portage
Kendra Gwin, P.E., City of Portage
Daniel Starkey, P.E., AECOM
![Page 2: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/2.jpg)
City of Portage
• Population of 45,000
• Groundwater source of supply
• Water supply and distribution system operated under contract by United Water
City of Portage, Garden Lane Water Treatment Plant
![Page 3: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/3.jpg)
Background
• Portage operates 14 well fields located throughout the City
• Limited treatment includes chlorination, fluoridation and phosphate for iron sequestration
• Average day pumping: 5.5 MGD
• Peak day: 17.6 MG
City of Portage, Garden Lane Water Treatment Plant
Garden Lane Well Field
![Page 4: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/4.jpg)
Garden Lane Well Field Site
City of Portage, Garden Lane Water Treatment Plant
Well GL-3
Well GL-2
Well GL-1
Well GL-4 (New)
Treatment Plant Location
![Page 5: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/5.jpg)
Garden Lane Well Field• Three existing wells
• Wells contain elevated levels of iron, manganese and arsenic
• Two wells consistently above the 10 ug/L arsenic MCL
• All wells above the 0.3 mg/L iron SMCL
• Well field relegated to “stand-by” service
• This well field is in the center of the City and is a critical component of the overall water supply and distribution system
• Shift base load capacity to a more reliable and protected aquifer
City of Portage, Garden Lane Water Treatment Plant
![Page 6: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/6.jpg)
Feasibility Study Prepared in 2006
• Evaluated various treatment methodologies• Coagulation/filtration• Ion exchange• Chemical oxidation/filtration• Adsorption
• Treatment iron removal alternatives were considered• Pressure filtration• Aeration + Detention + Pressure Filtration• Aeration + Detention + Gravity Filtration• Partial Flow Treatment + Blending
• Pressure filtration was identified as the most cost-effective option
City of Portage, Garden Lane Water Treatment Plant
![Page 7: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/7.jpg)
Co-Precipitation of Arsenic and Iron using Pressure Filtration
• Proven technology
• Soluble iron (Fe 2+) and arsenic (As 3+) are oxidized to insoluble iron (Fe 3+) and arsenic (AS 5+)
• Arsenic is adsorbed and enmeshed in the resulting iron floc
• Filtration removes insoluble iron/arsenic precipitate
• Iron must be present in sufficient quantity
City of Portage, Garden Lane Water Treatment Plant
![Page 8: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/8.jpg)
Arsenic Treatment Process Selection Guide
City of Portage, Garden Lane Water Treatment Plant
• Iron must be present in sufficient quantity • Ratio of iron to arsenic of 20:1 (minimum) is “rule of thumb”• In Portage this ratio is 50+:1 with naturally occurring iron
![Page 9: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/9.jpg)
Preliminary Investigation
• City investigated various pressure filtration systems
• Three systems were selected for pilot testing in 2007
• Visits made to other cities to observe and seek input from operators
• Filtronics (Anaheim, CA) was selected• Use of proprietary media allows for higher than normal filtration rate• Short (4-min) backwash and at reduced interval (8-hour)• Backwash reclamation system was a standard offering• Significant experience in the western US where arsenic is a major problem
City of Portage, Garden Lane Water Treatment Plant
![Page 10: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/10.jpg)
Pilot Testing
• Well GL-2 with highest levels of arsenic was tested
• Chlorine (sodium hypochlorite) used as oxidant
• 3-inch pilot unit
City of Portage, Garden Lane Water Treatment Plant
![Page 11: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/11.jpg)
Pilot Testing Results
Raw Water Finished Water• Arsenic: 20 - 27 ug/L (range) 1.5 - 3.0 ug/L (range)
• Iron: 1.0 - 1.1 mg/L (range) ND- 0.002 mg/L (range)
• Manganese: 0.084 - 0.086 mg/L (range) 0.018 – 0.027 mg/L (range)
• Chlorine breakpoint concentration of 19 ppm
• Excellent removals observed at chlorine feed rates of 6 to 8 ppm
City of Portage, Garden Lane Water Treatment Plant
![Page 12: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/12.jpg)
System DesignSupply
• 3,000 GPM (4.32 MGD) firm capacity
• 4,000 GPM (5.76 MGD) total system capacity
• New 1,200 GPM supply well, GL-4
City of Portage, Garden Lane Water Treatment Plant
![Page 13: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/13.jpg)
System Design
City of Portage, Garden Lane Water Treatment Plant
Filtronics Treatment and Filtration System
![Page 14: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/14.jpg)
System Design
Filtration
• Reaction vessels (2)– 3.5 minutes CT at design flow rate
• Filtration vessels (4)– Filtration rate 10 gpm/ft2
– Backwash rate 20 gpm/ft2
– Filter area 100 ft2 per filter
• Provisions for future addition of a 5th filter
City of Portage, Garden Lane Water Treatment Plant
![Page 15: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/15.jpg)
Raw Water Quality
City of Portage, Garden Lane Water Treatment Plant
![Page 16: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/16.jpg)
Finished Water Quality
City of Portage, Garden Lane Water Treatment Plant
![Page 17: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/17.jpg)
Waste Backwash Water Management Options
• On-site management using ponds or infiltration beds• High groundwater table• Heavy, “muck”-type soils• Limited soil permeability would result in large ponds • Well field located in a park setting
• Discharge to municipal sewer system• Arsenic limits would likely be exceeded without pretreatment• Prohibitively expensive
• Reclamation and re-use • Separate solids and reuse backwash water• Dewater and dispose iron/arsenic solids in a Type II landfill
City of Portage, Garden Lane Water Treatment Plant
![Page 18: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/18.jpg)
Filter Backwash
City of Portage, Garden Lane Water Treatment Plant
![Page 19: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/19.jpg)
Filter Backwash
• Backwash interval: 8 hours
• Backwash duration: 4 minutes
• Rinse duration: 1 minute
• Backwash rate: 20 gpm/ft2
• Rinse rate: 10 gpm/ft2
City of Portage, Garden Lane Water Treatment Plant
![Page 20: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/20.jpg)
Filter Backwash
• Waste backwash volume: 9,000 gallons per backwash
• Tank sized to accommodate 16 filter backwashes
• 150,000 gallon total capacity
• Iron/arsenic precipitate settles in the conical tank bottom
City of Portage, Garden Lane Water Treatment Plant
![Page 21: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/21.jpg)
Backwash Reclamation• Decanter collects supernatant, which
is pumped to the head of the plant for filtration and reuse
• Backwash recycle rate is limited to <10% of the forward flow
City of Portage, Garden Lane Water Treatment Plant
![Page 22: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/22.jpg)
Backwash Reclamation
• Solids accumulate in the waste backwash tank
• Estimated that solids will be removed 2x year
• Plate and frame filter press is provided to dewater precipitate
• Solids were tested during pilot study and are non-hazardous
City of Portage, Garden Lane Water Treatment Plant
![Page 23: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/23.jpg)
City of Portage, Garden Lane Water Treatment Plant
![Page 24: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/24.jpg)
City of Portage, Garden Lane Water Treatment Plant
![Page 25: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/25.jpg)
City of Portage, Garden Lane Water Treatment Plant
![Page 26: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/26.jpg)
City of Portage, Garden Lane Water Treatment Plant
![Page 27: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/27.jpg)
New Well House, GL-4
City of Portage, Garden Lane Water Treatment Plant
![Page 28: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/28.jpg)
New Well, GL-4
City of Portage, Garden Lane Water Treatment Plant
![Page 29: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/29.jpg)
Sustainability Features
• Natural Lighting
• Pervious Pavement (Parking Area)
• Natural Prairie Site Restoration
• Stormwater “Rain Garden”
City of Portage, Garden Lane Water Treatment Plant
![Page 30: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/30.jpg)
Current Status• System was started in June 2010
• Arsenic and iron removals have been consistent with results of pilot work
• Finished water quality:• Arsenic 2-3 ug/L• Iron <0.01 mg/L
• Waste backwash sludge dewatering not performed to date
• Resolving communication issues between the local filter control panel and the central SCADA system
• Developing a level of comfort with operating the City of Portage’s first full-scale treatment system
City of Portage, Garden Lane Water Treatment Plant
![Page 31: Arsenic/Iron Co-Precipitation and High Rate Filtration in the City of Portage](https://reader038.fdocuments.us/reader038/viewer/2022110211/56813066550346895d963e7e/html5/thumbnails/31.jpg)
Ribbon Cutting Ceremony August 2, 2010
City of Portage, Garden Lane Water Treatment Plant