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Biological Aerated Filtration (BAF) at the Denver Water Recycling Plant

Biological Aerated Filtration (BAF) at the Denver Water Recycling Plant. 2006 Water Reuse Workshop Golden, CO. Russell Plakke, Denver Water. Overview. Define the project quality goals for the BAF and Plant Construction Ammonia removal mechanisms utilized, a comparison

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Biological Aerated Filtration (BAF) at the Denver Water Recycling Plant

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  1. Biological Aerated Filtration (BAF) at the Denver Water Recycling Plant 2006 Water Reuse Workshop Golden, CO Russell Plakke, Denver Water

  2. Overview • Define the project quality goals for the BAF and Plant • Construction • Ammonia removal mechanisms utilized, a comparison • Chemical costs of operation • Operational issues/benefits • Results and performance tests

  3. Project Definition – Plant Quality • Ammonia goal: non-detectable • Total Coliform: 2.2/100 mlE. Coli: 126/100 ml • Turbidity: < 1.5 NTUTitle 22 < 2 NTU; Colorado < 3 NTU • Phosphorus: < 0.6 mg/l

  4. BAF Effluent Water Quality Requirements

  5. Reuse Treatment Process NaOH Cl2 Metro Secondary Clarifier Polymer Pump Station Burlington Ditch Biological Aerated Filters Rapid Mix Flocculation NaOH, NH3Sodium Bisulfite Coagulant Polymer Service Water Xcel Mainline Contact Basin Filters Sedimentation Storage Tank Cl2 NH3 NaOH Cl2 NaOH (NH3) Polymer Cl2 Cl2NH3

  6. BAF Implementation • Proposed ammonia removal facility at WWTP deleted – determined unnecessary to meet discharge regs • Fast track schedule necessary • $10 million change

  7. Kruger Biostyr Process

  8. BAF Cell Number Selection 6 cells ~ 60 lb/d/kcf 9 cells 30 mgd 7 cells ~ 5gpm/sf 45 mgd 10 cells

  9. Ammonia Reduction MechanismsUtilized • Breakpoint • Biological Nitrification • Combination

  10. Breakpoint NaOH Cl2 Metro Secondary Clarifier Polymer Pump Station Burlington Ditch Rapid Mix Flocculation Coagulant Polymer Service Water Xcel Mainline Contact Basin Filters Sedimentation Storage Tank Cl2 NH3 NaOH Cl2 NaOH (NH3) Polymer Cl2 Cl2NH3

  11. Operational IssuesBreakpoint Flow limiting Cost Corrosion caused by off gassing Maintaining effluent chlorine residual

  12. Chemical Cost - Breakpoint • Chlorine: • Typical chlorine dose = 119 mg/l • Daily chlorine usage = 6,000 ppd • Annual chlorine cost = $610,000 • Caustic: • Typical caustic dose = 223 mg/l • Daily caustic usage = 11,000 ppd • Annual caustic cost = $870,000

  13. Chemical Cost With BAF • Chlorine: • Typical chlorine dose = 6 mg/l • Annual chlorine cost = $31,000 • Caustic: • Typical caustic dose = 22 mg/l • Annual caustic cost = $90,000 • Savings • Projected annual savings = $1,359,000

  14. Operational Benefits of BAFs • Significantly reduced chemical dose requirements: • Primary ammonia removal mechanism was changed from breakpoint chlorination to BAFs • BAF aeration improved source water treatablity • Excellent ammonia removal

  15. Effluent Quality

  16. Cold Weather Performance Test

  17. Ammonia Swing Load Test 3000 2 Ammonia Load (Lbs/Day) BAF Effluent Ammonia (mg/L) 1.5 BAF Effluent mg/L NH3-N 1500 1 NH3 Load - Lbs ofNH3-N/Day 0.5 0 0 1 7 13 19 25 31 37 43 Time (Hours)

  18. Peak Ammonia Load Test 4500 3.5 Ammonia Load (Lbs/Day) BAF Effluent Ammonia (mg/L) Designed Peak 3 load for winter conditions: 2600 LBS/Day 2.5 3000 2 NH3 Load - Lbs of NH3-N/Day BAF Effluent mg/L NH3-N 1.5 1500 1 0.5 0 0 1 7 13 19 25 31 37 Time (Hours)

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