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 ml E. Coli: 126/100 ml Turbidity: < 1.5 NTU Title 22 < 2 NTU; Colorado < 3 NTU Phosphorus: < 0.6 mg/l

4. BAF Effluent Water Quality Requirements

5. Reuse Treatment Process Service Water Xcel Mainline Metro Secondary Clarifier Pump Station Burlington Ditch Rapid MixFlocculation SedimentationFiltersContact Basin Storage Tank Biological Aerated Filters Cl 2 NH 3 NaOH NaOH, NH 3 Sodium Bisulfite Coagulant Polymer Polymer Cl 2 Cl 2 NaOH (NH 3 ) Cl 2 NH 3 NaOH Cl 2 Polymer

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

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

18. Ammonia Reduction Mechanisms Utilized Breakpoint Biological Nitrification Combination

19. Breakpoint Service Water Xcel Mainline Metro Secondary Clarifier Pump Station Burlington Ditch Rapid MixFlocculation SedimentationFiltersContact Basin Storage Tank Cl 2 NH 3 NaOH Coagulant Polymer Polymer Cl 2 Cl 2 NaOH (NH 3 ) Cl 2 NH 3 NaOH Cl 2 Polymer

20. Operational Issues Breakpoint Flow limiting Flow limiting Cost Cost Corrosion caused by off gassing Corrosion caused by off gassing Maintaining effluent chlorine residual Maintaining effluent chlorine residual

21. 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

23. 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

25. 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

26. Effluent Quality BreakpointBio (BAF) Sodium (mg/l) 180120 Chloride (mg/l) 15885 Conductivity1180929 Nitrate (mg/l as N) 6.6314.0 NH3 (Inf) (mg/l as N) 12.69.7

29. Cold Weather Performance Test InfluentEffluentReduction CBOD (mg/l) 13562% TSS (mg/l) 12558% Ammonia (mg/l) 15.80.1599% Nitrite (mg/l) 0.3270.01795% Alkalinity (mg/l) 1586658% pH (SU) 6.606.65

30. Ammonia Swing Load Test 0 1500 3000 17131925313743 Time (Hours) NH3 Load - Lbs of NH3-N/Day 0 0.5 1 1.5 2 BAF Effluent mg/L NH3-N Ammonia Load (Lbs/Day) BAF Effluent Ammonia (mg/L)

31. Peak Ammonia Load Test 0 1500 3000 4500 171319253137 Time (Hours) NH3 Load - Lbs of NH3-N/Day 0 0.5 1 1.5 2 2.5 3 3.5 BAF Effluent mg/L NH3-N Ammonia Load (Lbs/Day)BAF Effluent Ammonia (mg/L) Designed Peak load for winter conditions: 2600 LBS/Day