Post-Aerobic Digester with Bioaugmentation Pilot Study City of Meridian, ID WWTP PNCWA 2010

Transcription

1 Post-Aerobic Digester with Bioaugmentation Pilot Study City of Meridian, ID WWTP by: William Leaf Adrienne Menniti Bruce Johnson CH2M HILL, Inc. Clint Dolsby Tracy Crane City of Meridian October 26, 21 PNCWA 21 Introduction Existing Facility Total Nitrogen Removal Study Post Aerobic Digestion Pilot Conclusions 1

2 Existing facilities WWTP and Biosolids Disposal Recycled water facilities Meridian WWTP - PFD Raw Sewage Primary Clarifiers BNR Aeration Basin Secondary Clarifiers Filters Plant Effluent DAFT Thickening Anaerobic Digestion Centrifuge Dew atering Biosolids 2

3 Existing facilities Aeration Basins Primary Clarifiers Secondary Clarifiers Filtration Post Aeration Headworks UV Disinfection Photo Courtesy David Keil/HDR Outfall Chlorination Existing Treatment and Effluent Criteria Current NPDES Permit Five Mile Creek Boise River Municipal Wastewater Reuse Permit Class A Class D 3

4 Current NPDES Permit Five Mile Creek TABLE 1 NPDES Effluent Limits for Outfall 1 - Five Mile Creek Parameter Units Monthly Average 1999 NPDES Permit Weekly Average Daily Maximum Limit ph ph BOD 5 2 Dilution ratio 1 : < 4:1 mg/l Dilution ratio 1 : > 4:1 mg/l TSS 2 85% Removal Requirement mg/l Dissolved Oxygen mg/l > 6 Fecal Coliform Bacteria geometric mean based on min. 5 samples per month (for monthly average) or 5 samples per w eek (for w eekly average). # / 1 ml 1/1 ml 2/1 ml 8/1 ml 1. Dilution ration is the ratio of Five Mile creek flow upstream to effluent flow % removal requirement. Municipal Wastewater Reuse Permit Key Permit Requirements Category Permit Limits and Conditions Type of Wastewater Class A Municipal Wastewater Class D Municipal Wastewater Growing Season March 15 October 31 March 15 October 31 WWTP Effluent TN WWTP Effluent BOD5 WWTP Effluent Turbidity Limit WWTP Effluent Total Coliform Limit 15.5 mg/l, Seasonal Average 1 mg/l, Monthly Average Instantaneous Maximum < 5 NTU 24-hr Avg < 2 NTU Median Number < 2.2 per 1 ml Total Number < 23 per 1 ml in an sample NA NA NA Median Number < 23 per 1 ml Total Number < 23 per 1 ml in an sample 4

5 Sidestream Nitrogen Removal Study Anticipated Total Nitrogen and Total Phosphorus removal at WWTP Dewatering centrate stream rich in TP and TN Other study looked at TP removal City interested in evaluating TN removal from dewatering centrate Sidestream Nitrogen Removal Study Total Nitrogen Removal from Dewatering Centrate Reduce Ammonia from being returned to secondary treatment system Provide level of bioaugmentation (augment the nitrifiers in the aeration basin) Allows lower Solids Residence Time operation Increase in system nitrification capacity 5

6 Reduced SRT Operation Effectively controls Microthrix but reduces cold weather Temperature Effluent Ammonia nitrification 2 1. Temperature (deg C) Effluent NH 4 (mg/l). 1/24 11/3 11/13 11/23 12/3 12/13 12/23 1/2 1/12 Reduced SRT Operation Bioaugmentation can maintain nitrification and control Temperature Effluent Ammonia Microthrix 2 1. Temperature (deg C) Effluent NH 4 (mg/l) Bioaugmentation. 1/24 11/3 11/13 11/23 12/3 12/13 12/23 1/2 can mitigate 1/12 this 6

7 Sidestream Nitrogen Removal Study Total Nitrogen Removal Technologies evaluated InNitri (Inexpensive nitrification, by m2t Technologies) BABE (bioaugmentation batch-enhanced, by DHV) Post Aerobic Digestion Sidestream Nitrogen Removal Study Conclusions Process Advantages Disadvantages InNitri BABE Post aerobic digestion Improved capacity through nitrifier bioaugmentation No impact on struvite harvesting Improved capacity through nitrifier bioaugmentation No impact on struvite harvesting Improved stabilization of biosolids Reduction of biosolids for disposal Improved capacity through nitrifier bioaugmentation Provides total nitrogen removal without chemical addition High operational complexity High capital cost Requires alkalinity addition Requires alkalinity addition Operationally more complex than post aerobic digestion Least proven of three alternatives Complicated implementation of struvite harvesting 7

8 Existing Tanks Available Making bioaugmentation a feasible option Post Aerobic Digestion (PAD) Raw Wastewater Treated Effluent Benefits Simple sidestream nitrogen removal helps Meridian with effluent TN and eases ammonia loading to aeration basins No chemical addition Additional volatile solids destruction Reduced operating cost for sidestream N Removal Biosolids Mesophilic Anaerobic Digester Post Aerobic Digester 8

9 Bioaugmentation with PAD Biomass Raw Wastewater Treated Effluent Mesophilic Anaerobic Digester Bioaugmentation Concept Nitrifiers Effectiveness of bioaugmented nitrifiers? Amount of PAD biomass that can be recycled? Biosolids Post Aerobic Digester Pilot Study Goals 1. Determine feasibility of nitrifier bioaugmentation with PAD biomass 2. Determine TN removal performance across the post-aerobic digester 3. Verify volatile solids reduction with anaerobic biosolids produced at the Meridian WWTP 9

10 Pilot System Overview Activated Sludge Reactors 16-L Test and Control Reactors Fed with plant PE and configured like full scale plant Temperature = C SRT < 5 days Post-Aerobic Digester 16.5 L, 25-3 C Fed with Anaerobic Biosolids SRT = 7-14 days On/Off Aeration Cycles Post- Aerobic Digester Control Reactor Test Reactor Bioaugmentation Proof of Concept 2 15 unstable nitrification without bioaugmentation stable nitrification with bioaugmentation Effluent NH4 (mg/l) 5 Time 1

11 Post Aerobic Digester Results Mesophilic Digester Performance 8 Centrate Ammonia Anaerobic VSR Centrate NH4 (mg/l N) Average Centrate Ammonia 7 mg/l N Average Anaerobic VSR = 56% VSR (%) 1 1 1/24 11/3 11/13 11/23 12/3 12/13 12/23 1/2 1/12 11

12 Nitrogen Removal Nitrogen Conc (mg/l N) 1, Influent NH4 Effluent NH4 Effluent NOx SRT = 14 days SRT = 7 days SRT = SRT = 9 days 14 days Digester Optimization 8% ammonia removal and complete denitrification WITHOUT chemical addition ph = 6.2, Effluent Alkalinity = 13 mg/l as CaCO 3 Turned off digester feed for 1 day 1/24/9 11/13/9 12/3/9 12/23/9 1/12/1 Aeration Cycle 2 Optimized aeration cycle 2 minutes: 4 on/16 off 1.5 DO (mg/l) Time (minutes) 12

13 Volatile Solids Reduction PAD achieved 3% additional VSR at an SRT of 9 days Digester Volatile Solids Reduction 1 SRT = 14 days SRT = 7 days SRT = SRT = 9 days Digester Start-Up 14 days 8 VSR (%) /24/9 11/13/9 12/3/9 12/23/9 1/12/1 Bioaugmentation Results 13

14 Operation for unstable nitrification Ammonia Conc. (mg/l N) mg/l N Test Reactor Effluent Ammonia Bioaugmentation Begins Influent pump broken 11/13/9 12/3/9 12/23/9 1/12/1 Operation for unstable nitrification 16 Test Reactor Effluent TSS Effluent wasting only SRT = 4.5 ± 3.2 days Test Reactor SRT Intentional wasting SRT = 4.2 ±.8 days 16 TSS Conc (mg/l) Bioaugmentation Begins SRT (days) 11/13/9 12/3/9 12/23/9 1/12/1 14

15 Bioaugmentation Results Bioaugmentation resulted in 1 days of stable nitrification Ammonia Conc. (mg/l N) mg/l N Test Reactor Effluent Ammonia Bioaugmentation Begins Influent pump broken Difficulty recovering nitrification after upset shows that there is more research to done understanding and optimizing the system 11/13/9 12/3/9 12/23/9 1/12/1 Pilot Study Results Post Aerobic Digester Performance The post aerobic digester achieved 8% ammonia removal and complete denitrification. 3% additional VSR was observed at a post aerobic digester SRT of 9 days. Bioaugmentation 1 days of stable nitrification shows that bioaugmentation with PAD biomass is feasible. However, uncertainty related to the pilot results demonstrate the need for further research. 15

16 Full Scale Implementation Convert existing anaerobic holding tank to post aerobic digester, feed PAD biomass into splitter structure 15% reduction in aeration basin ammonia loading, 2-3 mg/l effluent TN reduction Conclusions 1. PAD achieved 8% ammonia removal and complete denitrification without chemical addition. 2. Full scale implementation would provide 15% reduction in secondary ammonia loading and 2-3 mg/l reduction in effluent total nitrogen. 3. 3% additional VSR was observed at a PAD SRT of 9 days. 4. PAD alone can provide $6,-$8, in operational cost savings per year. 5. This new bioaugmentation concept is feasible and deserves further study. 6. Currently being evaluated in the Facility Plan (City of Meridian, CH2M HILL, HDR) 16

17 Thank you QUESTIONS? 17