Odor Dispersion Modeling, Priority Odor Sources, and Recommended Improvements. May 25, 2012

Transcription

1 Odor Dispersion Modeling, Priority Odor Sources, and Recommended Improvements May 25, 2012

2 Agenda Background Information Sampling and Monitoring Odor Modeling Background Existing System Results Control Results Conceptual Treatment Alternatives Existing Treatment Performance Next Steps

3 Location

4 Rowlett Creek Water Recycling Center

5 Field Monitoring and Testing Odor Potential, Chemical treatment performance, superoxygenation evaluation On-site, direct measurement. Liquid Phase Vapor Phase Off-site, laboratory measurement. Odor Dispersion Modeling, Odor treatment performance, Odor Characterization

6 Site No. Total Sulfide (mg/l) Water Temperature ( C) Dissolved Oxygen (mg/l) ph (std units) Oxidation Reduction Potential (mv) Oxygen Uptake Rate (mg/l/hr) ISCO 24 Hour Total Sulfides Odalog Direct Jerome Flux Chamber Dilution-to-Threshold (odor units) Drager Tubes D Observations Field Monitoring and Testing LIQUID PHASE SAMPLING GAS PHASE SAMPLING Treatment Unit Sample Location Old Rowlett Pump Station Transfer Pump Station Eastern Hill Pump Station Influent Wet Well 1 X X X X X X X X X X X Influent Wet Well Location 2 X X X X X X X X X X Influent Wet Well- Exhaust 3 X X X X X X X X Influent Wet Well- Turbulent Location 4 X X X X X X X X X Headworks Building B Influent Channel 5 X X X X X X X X X X Grit Basins Parshall Flume 6 X X X X X X X X Grit Basin 7 X X X X X Splitter Box 8 X X X X X X X X X Center Well 9 X X X X X X X X X Primary Clarifiers Effluent Weir 10 X X X X X X X X X Effluent Trough 11 X X X X X X X Effluent Box 12 X X X X X X X X Combined Effluent Box 13 X X X X X X Primary Effluent Pump Station Open Grating Surface Prior to Wetwell 14 X Wet Well- Location 1 15 X X X X X X X X X X X Equalization Basin NE Upstream Location 16 X X X X X X X X X X X Trickling Filter Splitter Box Splitter Box 17 X X X X X X X X X Top - Along Arm 18 X X X X X X X X X X

7 Specific On-Site Sample Analyses Ferric Chloride Feed Effectiveness questioned during the kickoff meeting Liquid sulfide measurements Relatively high concentration (2.3 mg/l) Higher in pump station wetwell than in raw water Vapor Phase [H 2 S] > 30 ppm

8 Specific On-Site Sample Analyses Superoxygenation for Rowlett Pump Station OUR = 12 mg/l per hour Short forcemain limits pounds of oxygen added (avoid oxygen enriched atmosphere) Dissolved sulfide requirements Detention Time

9 Vapor Phase Sample Locations

10 Vapor Sampling Methodology Flux Chamber 5 l/min N 2 25min 2 l/min Tedlar Bag ASTM E-679

11 Specific On-Site Sample Analyses Priority Sources (Based on Observations, H 2 S Data and Previous Studies) Anaerobic Digesters Dewatering Building (Specifically the GBTs) Raw Wastewater Pump Station Primary Effluent Pump Station Grit Basins Trickling Filters Dewatered Sludge Dumpsters

12 Why Model (it s complicated) Variables to consider: Quality of influent f(rainfall, temperature, collections system condition, lift stations, loading, ) Performance of treatment units Meteorology f(flow rate, design conditions, physical condition, operations, ) Odor composition f(rainfall, temperature, terrain, surface roughness, moisture, stability ) Odor composition (more to follow)

13 Odor Modeling Background Analytical Methods Gas chromatography, representative chemical Synthetic and Qualitative Methods Dilution to threshold/odor panels

14 Odor Terminology SAME Dilution to Threshold (DT) Odor Unit [per cubic meter] Odor Flux (odor unit per second per area) flux chamber sampling Odor Emission (odor unit per second) One 9 balloon released in a standard gymnasium: DT of 30,000

15 Useful DT Values Example Modeling

16 Air/Dispersion and WWTPs Three General Areas of Observation Federal Requirements for HAPs/NAAQs NOx, SOx, PM, lead, etc. NSR/PBR Standards for Combustion Generator/Flare Sources Odors Ordinances, Health, Nuisance Today s Discussion

17 Odor Modeling Limitations Comparatively little research Emissions not 100% additive Indirectly measured data Assumed units of measurement Difficult to Calibrate

18 Existing Conditions: Peak Values: 103 Dumpsters

19 Proposed Control - Digesters 22 Dumpsters onsite Ferric Chloride feed system operating Digester Odors Controlled

20 Proposed Control Gravity Belt Thickeners 22 Dumpsters onsite Ferric chloride feed system operating Gravity belt odors conveyed to treatment unit

21 Proposed Control Raw Wastewater Pump Stations 22 Dumpsters onsite Ferric Chloride feed system operating Raw wastewater pump station odors directed to a treatment unit

22 Proposed Control PEPS Wetwell 22 Dumpsters onsite Ferric Chloride feed system operating PEPS Wetwell odors routed to existing biofilter

23 Proposed Control PEPS Wetwell Biofilter Performance >99 percent removal of H2S >90 percent removal of Odors EBCT = feet of media depth EBCT = 54 5 feet of media depth H 2 S Concentration Odor Unit Inlet (mg/l) Exhaust (mg/l) Inlet (D/T) Exhaust (D/T) ,

24 Recommendations Raw Wastewater Pump Stations: Optimize ferric chloride feed in raw wastewater. Construct foul air collection ductwork. Construct bioscrubber with future carbon polishing option. Solids Dewatering Building Improve the HVAC system in the belt press room. Install covers over the belt presses and add air dispersion fans. Improve the covers at the GBTs to more completely capture odors from this area. Increase the GBT ventilation rate and exhaust the foul air to a bioscrubber.

25 Recommendations Primary Effluent Pump Station Cover and exhaust to the existing foul air treatment system at the primary clarifiers. Modify the foul air fan to accommodate the increased airflow. Fill biofilter to full depth. Additional Monitoring and Future Concerns Continue to monitor odors from flow equalization, trickling filters, and anaerobic digesters. Upon implementation of BNR, provide odor control for the anaerobic and anoxic zones in the BNR reactor odorous emissions.

26 Recommendations - OPCCs Rowlett and Transfer Pump Station $1,4 M Primary Effluent Pump Station $500 K Gravity Belt Thickeners $830 K

27 Questions?