The Boynton Beach Drinking Water ASR System A City Utilitys Perspective

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The Boynton Beach Drinking Water ASR System -

A City
Utilitys Perspective
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• What prompted ASR in Boynton Beach?
• Dependence on a coastal wellfield that was
  subject to
• Saltwater intrusion - Boynton Beachs eastern
  wellfield is located within 1 mile of the
  Intracoastal Waterway
• Decreasing output during drought conditions due
  to decreasing groundwater elevations
• NET RESULT - Limited raw water capacity

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Extremes in Water Table Elevation Seasonal
Demand

• During the 2000-01 drought, water table
  elevations in the east wellfield ranged from 3
  to 2 feet NGVD
• Pumpage ranged from approx. 75 million gallons/
  month to 250 million gallons/month

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Extremes in Water Table Elevation Seasonal
Demand (cont.)

• Just prior to the drought, water table elevations
  were unusually high due to a tropical storm (max.
  elevation approx. 7.5 feet).
• MOST OF THIS GROUNDWATER WAS LOST TO THE
  SALTWATER ENVIRONMENT

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Potential Groundwater Recovery from
Surficial Aquifer
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How Can Drinking Water ASR Assist Utilities in
Managing Raw Water Supply?

• ASR reduces dry season demand on surface sources
  regional water management systems
• Provides an immediate alternate source of water
  for potable supply
• Gives the utility an option when faced with
  seasonal droughts or low water conditions

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How Can ASR Be Used To Offset Peak Dry Season
Demands?

• In 2003 Annual average treated daily flow was
  15.51 MGD
• Peak Dry Season Month average was 16.05 MGD
• 3 other dry season months were also above the
  annual average daily flow

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Wet Season vs. Dry Season Demands
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Maximizing Storage in ASR By Using Surplus
Treatment Capacity During The Wet Season

• A hypothetical scenario based on reality
• System-wide treatment capability (ADF) 17.6 MGD
• Operating at 95 of capacity during Wet Season
  would allow storage of sufficient water to offset
  Dry Season impacts
• Following chart illustrates this scenario
• Wet season production increased to 16.72 MGD
• - Dry season production could be decreased to
  13.79 MGD

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• Potable Water ASR can make full use of available
  surplus treatment capacity

1.72 MGD below annual ADF
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Benefits to Utility

• ASR serves as an alternative water supply for
  coastal wellfields during dry season, if fully
  charged during wet season
• Provides a reliable water source during dry
  weather

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Benefits to the Environment

• ASR can make full use of existing surplus
  treatment capacity during wet seasons to
  alleviate impacts during dry seasons
• It can capture freshwater that would otherwise be
  discharged to estuaries, reducing environmental
  impacts
• Therefore, it can provide relief in the near
  term to stressed water resources

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Keys to Success in Boynton Beach

• Co-locating ASR with the Water Treatment Facility
• Simplicity of operation, under full control of
  Plant operators
• Multiple discharge points into plant process
  ranging from disinfection only to full treatment
• Cooperation of regulatory agencies

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Co-location of ASR Well on Plant Site
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Multiple discharge points into plant process
ranging from disinfection to full treatment

• Discharge to Recarbonation Basin provides
  chlorine contact time for disinfection
• Normal mode of operation
• Discharge to Backwash Basin is routed to plant
  influent, for full treatment
• Used during cycle start-up, and for blending
  during extended recovery cycles

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Conclusions

• ASR has a definite place in the Water Resource
  Management Plans for utilities in South Florida.
• It provides an alternative, highly reliable water
  source for seasonal use.
• ASR can also be used to meet peak seasonal
  demands while protecting the integrity of coastal
  wellfields. This has proven to be its greatest
  benefit to Boynton Beach.

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Conclusions (cont.)

• For greatest flexibility, Drinking Water ASR
  wells should be co-located with Water Treatment
  Facilities
• Drinking Water ASR is a technology that can be
  implemented on a large scale now using existing
  surplus plant capacity.

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And Now Ask Yourself Some Questions (especially
if you are a Utilities Manager)

• Does my treatment plant have surplus water
  capacity during the wet season (June through
  December)?
• Is my water supply stressed during dry seasons or
  prolonged dry weather
• Do I pray for rain (sometimes?- often?-
  constantly?)
• Do I hope for mandatory water restrictions, so I
  wont be the only one reducing pressure?
• Am I on a first name basis with everyone in the
  Water Use Permit Compliance Section?

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IF YOU ANSWERED YES TO MORE THAN ONE OF THE
PREVIOUS QUESTIONS-

• CONSIDER DRINKING WATER ASR

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THANK YOUQUESTIONS ARE WELCOME AT THIS TIME
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Chlorides

• Slope of curve varies with amount in storage, and
  rate of withdrawal
• Chloride is primary criteria for determining end
  of recovery cycles. (300 mg/l target)

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System Description

• 16 diameter carbon steel casing to a depth of
  804 bls, with an open hole construction to 909
  bls
• Completed in Suwanee limestone of Floridan
  Aquifer System

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PROFILE OF ASR - 1
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System Operation

• Operated cyclically now into cycle 21
• Storage volume of 12-132 MG/cycle

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Cycle test results

• Highest recovery at 91

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Added Benefit

• Adds capability to capture and store water
  accumulated during rainy season, which would
  otherwise be lost to tide

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Water Quality results

• Chlorides
• Hardness
• Turbidity

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Hardness

• Tracks closely with chlorides
• Tendency for hardness to increase during recovery
  cycle, primarily due to limestone matrix of
  storage zone

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Turbidity

• Initially high at the start of each recovery
  cycle, rapidly lowering to acceptable levels.
• May increase during times of increased pumping
  rate, but returns to low levels quickly

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What Are Its Benefits To The Utility?

• Can be used to meet peak dry season demands
• Serves as an alternate source for coastal
  wellfields during dry season, if fully charged
  during wet season
• Provides a reliable water source during dry
  weather
• Makes full use of surplus treatment capacity
  during wet season