Moving Bed Biofilm Reactor Retrofit for Ammonia and Nitrate Removal

1
Moving Bed Biofilm Reactor Retrofit for Ammonia
and Nitrate Removal

• BV SACWSD
• Lela Parsons, P.E. Greg Fabisiak
• Mark Maxwell, P.E. Joan Chavez

2002 RMSAWWA / RMWEA ANNUAL CONFERENCE
2
Phase 2 Project Components

• Wastewater Collection System Master Plan
• Utility Plan
• Preliminary Design Report
• Detailed Plans Specifications
• Contract Administration

3
Utility Plan Goals

• Provide information required by DRCOG and for SRF
  Funding
• Evaluation of existing facilities
• Population flow projections
• Environmental assessment to support FNSI
• Alternative analysis and recommendations
• Implementation and financial plans
• Public participation
• Determine necessary wastewater facilities for
  capacity and regulatory compliance through 2020

4
Site Layout
5
WM WWTP Existing Unit Processes
East Trickling Filter
Final Clarifiers
Chlorination
P
Flow Splitter
Discharge to South Platte River
Raw Wastewater
Dechlorination
Mechanical Screenings
Primary Clarifiers
Rotating Biological Contactors
P
P
Chlorination
West Trickling Filter
Final Clarifier
Combined Primary MBBR Sludge
Accelerated Air Drying of Dewatered Biosolids
Prior to Ultimate Disposal of Class A Product
Degritting
Gravity Thickener
Anaerobic Digesters
Deskins Quick-Dry Filtration SystemTM
P
6
WM WWTP Existing Unit Process Capacities
7
Treatment Issues

• Regulatory Compliance
• Reclassification of the South Platte River
  requires additional disinfection
• Updated model of Segment 15 of the South Platte
  River resulted in imposition of effluent ammonia
  limit
• Current and Future Water Quality Concerns
• Dissolved oxygen
• Ammonia
• Nitrates
• Nutrients

8
South Platte Dischargers
9
Treatment Issues (cont)

• WM WWTP Treatment Capacity
• Surge in residential and commercial activity in
  the service area
• Current treatment capacity of 4.4 mgd forecasted
  to only be sufficient through 2003
• Limited room for additional expansion at the
  existing site

10
SACWSD Future Plan

• Complete Phase 2 expansion at WM WWTP by 2004
• Phase 2 will provide capacity until 2008
• New WWTP will be needed by 2009- could be
  regional WWTP or SACWSD WWTP
• Upgrade WM WWTP when appropriate to meet future
  water quality regulations

11
WM WWTP Expansion

• Increase treatment capacity from 4.4 to 7.0 mgd
• Notice to proceed issued September 2002
• Short-term - capacity expansion allows growth
  while new WWTP is designed and constructed
• Long-term - WM WWTP will continue to serve the
• southern area
• of the District

12
Phase 2 Improvements

• Major Expansions
• Secondary Treatment Process
• Solids Handling Process
• Additional Improvements
• Replace Manual Bar Screen
• Demolish RBCs
• Upgrade Disinfection Facilities
• Add Stand-by Power Capacity
• Expand Administration Building/Garage

13
Treatment Alternatives
Alternative A
Alternative B

• Activated Sludge
• Anoxic/oxic basins
• WAS Pumping Station and Blower Building
• New Aerobic Sludge Handling
• Centrifuge
• Aerated sludge holding
• Biological Nutrient Removal (future)

• Fixed Film
• MBBR
• Anoxic/oxic basins
• Blower Building
• Additional Anaerobic Solids Processing
• Convert secondary digester to primary digester
• New secondary digester
• Chemical Phosphorous Removal (future)
• Post Denitrification (future)

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Alternative Evaluation

• Alternative A slightly less expensive
• Alternative A more operationally complex-
  requires separate solids handling process
• Alternative B will require chemical addition for
  future phosphorous removal
• SACWSD has always utilized and prefers fixed film
  processes

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Selected Alternative Moving Bed Biofilm Reactors

• Fixed film process manufactured by Kaldnes
• Employs high-density polyethylene plastic media,
  coarse bubble aeration, and sieves
• Biofilm grows on inside of the media
• Specific gravity
• of 0.96
• 150 ft2/ft3 media
• surface area
• 0.93 /ft clean
• water oxygen
• transfer rate

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Design Conditions

• 100 mg/L influent BOD
• 2 anoxic and 2 oxic reactors in series
• 60 fill in each reactor
• Coarse bubble diffuser system in oxic reactors
• Submersible propeller mixers in anoxic reactors
• 4 mg/L summer DO concentration
• 5 mg/L winter DO concentration
• 200 internal recycle for nitrate removal

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Treatment Requirements

• East Plant Effluent
• BOD5 reduction lt10 mg/L
• Total ammonia reduction lt2 mg-N/L (complete
  nitrification)
• Total nitrate reduction lt10 mg-NO3/L (partial
  denitrification)
• Blended Effluent (East and West Plant)
• CBOD reduction lt25 mg/L
• Total ammonia reduction lt10 mg-N/L

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Selected Alternative Flow Schematic
East Trickling Filter
Anoxic MBBR
Oxic MBBR
Final Clarifiers
Chlorination
P
P
Discharge to South Platte River
Raw Wastewater
Dechlorination
Mechanical Screenings
Primary Clarifiers
P
Flow Splitter
P
Chlorination
West Trickling Filter
Final Clarifier
Combined Primary MBBR Sludge
Accelerated Air Drying of Dewatered Biosolids
Prior to Ultimate Disposal of Class A Product
Degritting
Gravity Thickener
Anaerobic Digesters
Deskins Quick-Dry Filtration SystemTM
P
Existing Facilities
Phase 2 New
Phase 2 Modified
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Operational Issues

• Portion of primary effluent must be bypassed
  around existing trickling filter
• Requires construction of a new flow splitter
  structure
• Prevents hydraulic surcharging of underdrains
• Assures sufficient soluble BOD for
  denitrification
• Allows ETF pumping station to be taken out of
  service
• Trickling filter snail accumulation
• Installed an automatic, self-cleaning strainer
  with 1/8- inch openings at the ETF pumping station

20
Total Project Costs

• Engineers Construction
• Cost Opinion
• Low Bid Price
• Difference Between High
• and Low Bids

13,283,000 12,774,000 475,300