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Kailua Regional WWTPand Collection SystemOdor Control Improvements
Hawaii Water Environment Association
February 15, 2011
Overview
• Background
• Existing Conditions/Challenges
• Project Strategy and Goals
• Design Improvements
• Current Project Status
Brown and Caldwell
Background
Brown and Caldwell
• Hydrogen Sulfide (H2S)• <0.5 ppb Detection threshold (lab conditions)• 2 to 5 ppb Practical threshold in open atmosphere• 20 to 30 ppb Complaint level
• 10 ppm OSHA limit• 10 to 50 ppm Eye, nose, throat irritation• 50 to 300 ppm Eye/respiratory injury• >300 ppm Life threatening
• Hydrogen sulfide production
Sulfuric acid corrosion
Background
Brown and Caldwell
H2S
SO4
H2S
Sulfate Reducing Bacteria (Desulfobacter / Desulfovibrio)Conversion of Sulfate to Sulfide
Deposits
• Sulfuric acid (H2SO4) production
Background
Brown and Caldwell
Sulfate Oxidizing Bacteria (Thiobacillus thioxidans or Thiobacillus
concretivorous)Conversion of Sulfide back to Sulfate
Deposits
SO4
H2S H2S H2SO4
• Sulfuric acid damage• Ferrous metals• Concrete
Sulfuric acid corrosion
Background
Brown and Caldwell
• ROSE Program• Wastewater Odor Master Plan• Preliminary Engineering Report
• Sampling/Data CollectionH2S concentrationsDissolved sulfide testingAir flow measurementsStatic pressure measurementsSmoke tests
• Identification of Problem Areas• Design Recommendations
Background - History
Brown and Caldwell
Static Pressure Testing
Smoke Testing
Background – Project Sites
Brown and Caldwell
Ahuimanu Pretreatment Facility
Kaneohe Pretreatment Facility
Background – Project Sites
Brown and Caldwell
Kailua Road WWPS
Kailua Regional WWTP
Kailua Regional Wastewater Treatment Plant
Background – Project Sites
Brown and Caldwell
• Headworks Odor Control (HOC)• Influent pump station, headworks• Stage 1 - single chemical scrubber
• Proprietary chemicals
• Monthly cleaning – sulfur deposition
• Stage 2 - two activated carbon vessels• Single bed
• Operation in parallel
• Actual air flow measured lower than designed
Headworks Odor Control System
Existing Conditions and Challenges
Brown and Caldwell
• Primary Odor Control (POC)• Primary clarifiers, biotower pump station, DAFTs
Primary Odor Control System
Existing Conditions and Challenges
Brown and Caldwell
• Stage 1 - two chemical scrubbers• Proprietary chemicals
• Monthly cleaning – sulfur deposition
• Stage 2 - three activated carbon vessels• Single bed
• Operation in parallel
• Actual air flow measured lower than designed
• Secondary Odor Control (SOC)• Biotowers, solids contact tanks
Secondary Odor Control System
Existing Conditions and Challenges
Brown and Caldwell
• Stage 1 - two chemical scrubbers• Proprietary chemicals
• Minimal cleaning due to much lower H2S concentrations
• Stage 2 - four activated carbon vessels• Single bed
• Operation in parallel
• Actual air flow measured lower than designed
• Dewatering Building Odor Control (DOC)• Dewatering building second floor only
Secondary Odor Control System
Existing Conditions and Challenges
Brown and Caldwell
• Activated carbon• Fugitive emissions during
operation (open louvers, open doors, open truck rollup door, open rear enclosure)
• Key Areas• Primary clarifiers• DAFTs• Dewatering building
• Why?• Extended collection system to
generate high sulfides• Containment issues – missing
gaskets, open covers, doors open• Inadequate exhaust ventilation rate
– not achieving a negative pressure under process tank covers
Smoke test
Existing Conditions and Challenges
Brown and Caldwell
• Implement odor improvements• Chemical addition• Improved containment• Improved air flow• Improved treatment
• Meet regulatory requirements
• Reduce nuisance odors for neighbors
• Simplify odor system operation and maintenance
• Improve operator safety
Project Strategy and Goals
Brown and Caldwell
• Chemical Addition• 3 collection system sitesGoal – 0.5 mg/l dissolved sulfide conc entering
Kailua RWWTP
Jar testing – selection of chemicals for pilot testing
Pilot testing – testing of effectiveness, estimation/optimization of dosage
Calcium nitrate selected
• Headworks system• Polishing/emergency system
• Sodium hypochlorite selected
Design Improvements
Brown and Caldwell
• Headworks Odor Control (HOC)• New, larger ductwork and fans• Two new biotrickling filters (replaces chemical scrubber)• Two new activated carbon vessels (four total)• Odor exhaust stack extension
Design Improvements
Brown and Caldwell
• Biotrickling Filter Schematic
Design Improvements
Brown and Caldwell
• Primary Odor Control (POC)• ABANDONED• DAFT air flow diverted• PC air flow diverted• Biotower PS air flow diverted
Design Improvements
• Biotower Pump Station Odor Control (BOC)• New packaged carbon
system
Brown and Caldwell
• Secondary Odor Control (SOC)• New, larger ductwork and fans• Conversion of biotowers (replaces chemical scrubbers)• Primary clarifier air flow directed to biotowers • Odor exhaust stack extension
Design Improvements
Brown and Caldwell
• Biotower Schematic
Design Improvements
Brown and Caldwell
• Dewatering Building Odor Control (DOC)• Enclosure of first and second floors,
including truck bay• New supply and exhaust air system for
second floor• New two-speed supply and exhaust air
system in first floor truck bay• New activated carbon vessels (one for
each floor)
Design Improvements
Brown and Caldwell
Short dewatering truck
Long dewatering truck
• DAFT Improvements• Reroute of DAFT overflow to Biotower
Pump Station• Piping improvements of primary sludge
line to allow bypass of DAFT• Replace access hatches• Installation of brush attachments to
facilitate weir cleanings
• New enclosed digester waste gas burner
• New odor monitoring system
Design Improvements
Brown and Caldwell
DAFT access hatch
Existing waste gas burner
• Phase 1• Construction started Nov 2010• Completion early 2012• Construction cost ~$12 million
• Phase 2• Currently out to bid• Completion end of 2012• Construction cost estimated ~$4 million
Current Project Status
Brown and Caldwell
Questions?
Kailua Regional WWTP and Collection System Odor Control Improvements
Brown and Caldwell