Toledo Waterways Initiative and 185 mgd HRT Facility Wet Weather Partnership CSO Workshop Chicago, I

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Toledo Waterways Initiative and 185 mgd HRT
FacilityWet Weather Partnership CSO
WorkshopChicago, IL

• Larry Jaworski - Black Veatch
• F. Chris Middlebrough City of Toledo, OH
• Carol L. Hufnagel Tetra Tech

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Background

• Late 80s Early 90s Three CSO storage
  tunnels constructed.
• October 1991 Original US/OEPA vs. Toledo
  lawsuit.
• July 2002 Toledo voters approve ordinance to
  settle lawsuit.
• Consent decree.
• Start of Toledo Waterways Initiative.

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Consent Decree Requirements

• Discharge from Outfall 002 allowed only when flow
  exceeds 400 MGD
• Activated sludge treatment of all flows up to 195
  MGD
• 60 MG EQ basin (reduced to 25 MG pending EPA
  approval) dewatered flows must receive activated
  sludge treatment
• 185 MGD high rate clarification facilities may
  discharge only when flow exceeds 195 MGD EQ
  basin is full
• Prohibited return of wet weather treatment solids
  to main plant headworks

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Bay View WWTP Flows

• Toledo, OH sewer system is 30 combined
• Bay View WWTP flows
• 45 MGD dry weather
• 70 MGD average annual
• 130 MGD peak month
• 400 MGD peak hour
• Maximum flow through secondary treatment is
  approximately 195 MGD

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HRT Milestones

• February 2003 - Pilot Test Completed
• HRT - DensaDeg vs. Actiflo
• UV Disinfection - Medium Pressure vs. LPHO
• 2005 Construction Started
• October 2006 Performance Testing of HRT
• 2007 Begin Two-Year Effectiveness Study

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HRT Evaluation Factors

• Discharge Requirements
• Frequency of Use/Chemical Usage
• Pretreatment Needs
• Pumping
• Fine Screening
• Grit Removal
• Odor Control
• Startup Shutdown Requirements
• Solids Handling Requirements
• Flexibility to Use for Primary Tertiary
  Treatment

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HRT Pilot Test

• Actiflo - Kruger (Veolia Water)
• DensaDeg - IDI

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Actiflo DesignConsiderations

• Fine Screening (lt 1/4 inch openings)
• f (Hydrocyclone opening)
• Requires Grit Removal
• Thin Sludge (lt0.5 solids)
• Volume 2 to 3 of Influent Flow
• ( capacity of recirculation
• pumps)
• Media Recirculation
• Cleaning System

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DensaDeg Design Considerations

• Less Consistent Performance Due to Ballast Media
  (Sludge) Variability

• Fine Screening (lt 1/2 inch openings)
• Concentrated Sludge (3 to 4 solids)
• Slower Startup Due to Reliance on Sludge
  Recirculation
• Potentially deeper settling compartment than
  Actiflo

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HRT Intermittent Operation Issues

• Dry process startup time required to establish
  process equilibrium
• Handling off-spec effluent
• Bringing parallel units on-line
• Maintaining a standby operational mode
• necessary for Actiflo
• Dewatering to prevent nuisance conditions

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Other Uses for HRT

• Primary Treatment
• Derate to about 1/3 to ½ of Wet Weather Treatment
  Capacity
• Uses less Ferric Chloride than for Wet Weather
  Treatment
• Densadeg better than Actiflo due to solids
  thickening feature
• Dry Weather Tertiary Treatment
• Lowers TSS phosphorus concentrations
• Improves chances of meeting 7-day limits when
  averaged with wet days

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HRT Costs

• Capital costs very close to the same in most
  cases
• Smaller footprint for Actiflo due to higher
  loading rates
• Less pretreatment required for DensaDeg
• If solids cannot be returned to plant influent,
  solids handling costs are lower for DensaDeg
• OM costs slightly less for DensaDeg due mostly
  to lower pretreatment requirements

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Reasons for Selection of DensaDeg

• No additional sludge processing facilities
  required
• No additional fine screening facilities required,
  increasing amount of screening equipment to be
  maintained and screenings to be handled
• Rapid startup is not an issue
• Equipment is the same as existing equipment to
  service and maintain
• No need to maintain a standby mode
• No microsand and related maintenance and
  housekeeping issues

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High Rate Clarification
EQ BASIN
UP TO 400 MGD
27 MGD
UP TO 205 MGD
SCREENING GRIT REMOVAL
SECONDARY CLARIFIERS
BAY VIEW PUMP STATION
CHLORINE CONTACT BASIN
232 MGD
CHLORINE CONTACT REAERATION
AERATION BASINS
168 MGD
PRIMARY CLARIFIERS
UP TO 195 MGD
PRIMARY CLARIFIERS
GRIT REMOVAL
SKIMMINGS REMOVAL
UP TO 400 MGD
EFFLUENT PUMPING
NEW WET WEATHER FACILITIES
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Bay View WWTP Layout
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Toledo, OhioBay View Wastewater Treatment Plant
Reaeration Chlorination
Main WWTP
XS Flow
DensaDeg
EQ Basin
Vortex Grit Removal Screening (1 sewer)
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Toledo, OH DensaDeg Layout
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Toledo, OH DensaDeg HRT
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HRT Pipe Gallery Sludge Pumps
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HRT and EQ Basin
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HRT Treatment Results

• Performance testing results
• Effluent TSS 7 to 38 mg/L with average of 25
  mg/L.
• TSS removal averaged approximately 80.
• Effluent CBOD 22 to 177 mg/L with average of 52
  mg/L.
• CBOD removal averaged approximately 55.
• Mixture of dry and wet weather conditions during
  performance testing.
• 2-year effectiveness study ongoing thru 2008.

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First 6 Months of 2-year Effectiveness Study
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Wet Weather Treatment System Performance
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Two-Year Effectiveness Study

• Ongoing.
• Performance testing results verified.
• Continuing optimization.
• Have met final effluent limitations at flows up
  to 390 MGD. Including the big rain events of
  late August 2007.

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Facility Optimization

• Pilot study and performance testing used 40 mg/L
  or more FeCl3 and up to 3 mg/L of polymer
• while City now generally doses 10-30 mg/L
  FeCl3and 0.5-2 mg/L of polymer.
• A lot of DensaDeg effluent sent to activated
  sludge system.
• Jar testing of recent events to further optimize
  FeCl3 to polymer ratios.
• Generally constant ratio whether dosing 45 and
  1.5 mg/L or 15 and 0.5 mg/L (FeCl3 and polymer,
  respectively).

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Some Lessons Learned

• Density meters and blanket sludge depth detectors
  not necessary for intermittent operation
• Startup for intermittently operating facility
  takes longer to work out glitches longer
  warranty period is helpful
• Returning HRT effluent to secondary can inhibit
  nitrification
• Alkalinity consumption (HRT nitrification) ?
  loss of effluent buffering capacity (pH concerns)

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HRT Construction Costs
232 MGD Capacity
0.29/gpd
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HRT Annual OM Costs
Treating 1000 MG/yr
89/MG
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• Questions ???