Algae Control with Dissolved Air Flotation in Bellingham, WA
Transcript of Algae Control with Dissolved Air Flotation in Bellingham, WA
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Algae Control with Dissolved Air Flotation in Bellingham, WA
PNWS-AWWA Conference 2016
Joshua Kennedy/CH2M
Bill Evans/City of Bellingham
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Outline
• Algae in the Pacific Northwest
• Bellingham WTP background
• Alternatives and pilot study
• Chlorine gas conversion
• Conclusion
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Algae in the Pacific Northwest
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Climate change and algal blooms
• Increased temperatures result in rising lake temperatures
• Increased Proliferation of Algae & Algal Toxins
Lake Erie Algal Bloom, 2013, Source: NOAAWorldwide Lake Warming 2015, Source: NASA
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Algal blooms in Oregon
Source: https://public.health.oregon.gov/HealthyEnvironments/DrinkingWater/Operations/Treatment/Pages/algae.aspx
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Impacts of algae
Taste and odor events
Disruption of treatment equipment
Water quality issues
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Impacts of algae: Mitigation techniques
Source Management
Ozone
Chemical oxidation
Activated carbon (PAC,
GAC)
Dissolved Air Flotation
Operational Changes
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Bellingham WTP Background
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Whatcom Falls Treatment Plant background
Constructed in 1968
In-line Filtration Plant
Limited pre-treatment
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Whatcom Falls Treatment Plant background
Treatment
Plant
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Whatcom Falls Treatment Plant background
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Whatcom Falls Treatment Plant background:2009 algae event
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Alternatives and Pilot Study
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Treatment alternatives
No action
Relocation of the intake
Filter expansion
Construction of a pretreatment facility
Triple bottom line scoring was used for evaluation
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Chosen alternative
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Chosen alternative
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Pilot study
• Rented DAF unit, used existing pilot filter columns
• Tested loading rates of 10 to 20 gpm/sf
• Varied polymer dose and flocculation times
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Pilot study: Results
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Whatcom Falls Treatment Plant background
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Wat
er D
eman
d (
mgd
)
THM
in p
arts
per
bill
ion
Total Trihalomethane (THM) Averages and Water Demand 2003-2015
Farthest Sampling Site from Treatment Plant Average Water Used per Day (mgd)
The maximum THM allowed is 80 parts per billion
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Moving forward with DAF
• First DAF installation for drinking water in the NW
• One of the highest rate DAF units ever designed
• Climate considerations
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Chlorine gas conversion
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Chlorine gas conversion
Opportunistic time to consider conversion
Several associated risks
• Chlorine gas
• No scrubbers
• Outdoor storage
• Park Setting
• Operator space/parking nearby
• Supply chain issues
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Chlorine gas conversion: Alternatives Analysis
• Selected based on safety and O&M considerations
On-site generation
• Not selected due to potential environmental impacts and off-gassing
Bulk hypo
• Most familiar technology but not deemed safe for the City moving forward
Gas chlorine
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Chlorine gas conversion: Key benefits
Safety concerns
Environmental impacts
Supply issuesReduce no. of
deliveries
Chlorine gas
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Conclusion
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Bellingham project status
Going out to bid for
construction this year
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Bellingham project approach
Quickly and efficiently analyzing
alternatives
Early generation of 3D models
and site layouts
CH2M CPES™ Cost estimating
tool
30% deliverable drawings created in SketchUp
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Bellingham project approach
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Bellingham project approach
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Thank You