Comparison of MBBR and Suspended Growth BNR Performance at the HRWTF

2. COMPARISON OF MBBR AND Suspended growth BNR Performance at the HRWTF Erika L. Bailey, PE NC AWWA WEA Annual Conference November 16, 2015

3. 01 Introduction, Drivers, and Challenges Segregated Treatment Concept MBBR / Suspended Growth Comparison Conclusions Project Status 02 03 04 05

4. 01 Introduction, PROJECT DRIVERS, AND CHALLENGES

5. HRWTF is a publicly owned industrial treatment works • Located 20 miles southeast of Richmond, VA • 50 mgd capacity, currently treating 28 mgd • Small domestic base flow • 23,000 residents • LARGE industrial contribution • 85% of flow • High Purity Oxygen (HPO) activated sludge with denitrification • No nitrification currently

6. HRWTF Existing liquid treatment Process “HAP” Foul Condensate VAWCO RockTenn Industrial Headworks Reaeration Hercules Denit.Basin IndustrialPrimary Clarifiers HPO Aeration Tanks Evonik Final Clarifiers RAS Honeywell HOCl Domestic 2012 Improvements (Phase 1) DomesticHeadworks DomesticPrimary Clarifiers &Chlorine Contact Tanks Gravelly Run

7. Project Drivers • Nitrogen (TN) Reduction • Chesapeake Bay Nutrient TMDL • HRWTF currently purchases TN credits • Future market for credit purchases unknown • Ammonia (NH3-N) Reduction • Current NH3-N limit: 18.9 mg/L • 30% - 90% reduction anticipated • Monthly Avg: 2.0 – 14.2 mg/L • Daily max: 3.1 – 21.6 mg/L

8. Nitrogen Removal is Challenge at hRWTF

9. 02 Addressing BNR Challenges: Segregated Treatment Concept

10. Project development approach • Effectively build upon previous studies • “Segregated Treatment” alternatives to address key challenges • Leverage knowledge from previous testing • Effectively address nitrification inhibition 2007 Comprehensive Alternatives Evaluation identified Segregated Treatment as preferred alternative

11. Unique “Segregated Treatment” Approach Addresses Temperature Challenge • Separate high nitrogen and high temperature streams • Achieves biological nutrient removal on portion of flow • Eliminates need for cooling industrial influent • BUT • Honeywell wastewater contains nitrification inhibitors Domestic Honeywell Biological Nutrient Removal Segregated Stream Primary Treatment Ashland RockTenn VAWCO Evonik Honeywell Total Influent Final Effluent Combined Influent Secondary Treatment Primary Treatment

12. Segregated Treatment Approach Must Also Address Nitrification Inhibition • Limit Honeywell flow to Segregated Treatment • Use MBBR system for biological treatment • High rate process • Concentrated biomass; media provides high surface area to volume environment • Biofilm structure • Media contained within separate cells • Self-regulating system (do not manage SRT) MBBR: Moving Bed Biofilm Reactor BOD Removal Cell Nitrification Cells Anoxic Cell

13. Pilot Testing Conducted to Confirm Design Basis • Side-by-side comparison of suspended growth and MBBR processes • Both processes fed with the same influent flow stream • Domestic primary effluent • Gradually increased levels of Honeywell flow

14. 03 Comparison of MBBR / suspended Growth Performance

15. Pilot Testing Configuration

16. Pilot Testing Conditions

17. Scenario 1 – 40% Honeywell • TN removal in MBBR dropped when internal recycle was temporarily stopped. • TN removal quickly increased to the same levels as the Suspended Growth system once the recycle stream resumed.

18. Scenario 1 – 40% Honeywell • Ammonia reduction • Both systems achieved <1.0 mg/L NH3 for 85% of the time. • Solids removal • MBBR DAF unit provided greater and more consistent solids removal. • Polymer was not needed.

19. Scenario 2 – 70% Honeywell • MBBR • More stable removal of ammonia and TN • Suspended Growth • Drop in nitrification performance due to an unexplained loss of biomass

20. Scenario 2 – 70% Honeywell • Sudden increase in effluent TSS from the Suspended Growth system • Decrease in SRT and MLSS • SRT may have reached as low as 9 days (7 day aerobic SRT). • Nitrifier washout not expected (at 18 °C) • But continuous nitrification inhibition experienced in the Suspended Growth system would make it more sensitive to the low SRT impacts.

21. Scenario 2 – 70% Honeywell • Ammonia Removal • Suspended Growth system achieved <1.0 mg/L NH3 about 70% of the time. • MBBR achieved <1.0 mg/L NH3 for almost 100% of the time. • Solids removal: • MBBR DAF unit provided greater and more consistent solids removal. • Polymer was not needed.

22. Scenario 3 – 100% Honeywell • MBBR provides more stable performance in terms of ammonia and TN removal.

23. Scenario 3 – 100% Honeywell • Ammonia Removal • Both systems achieved <1.0 mg/L NH3 about almost 100% of the time. • MBBR achieved effluent ammonia < 0.1 mg/L 75% of the time • Suspended Growth achieved effluent ammonia < 0.1 mg/L 55% of the time • Solids removal: • MBBR DAF unit provided greater and more consistent solids removal. • Polymer was not needed.

24. Suspended Growth Performance Overview

25. MBBR Performance Overview

26. 04 Conclusions

27. Pilot Testing Confirms Selection of MBBR System • Typically outperformed Suspended Growth system • More stable • During loading condition transitions • At higher fractions of Honeywell in the combined influent • Better solids separation/control

28. Planned Segregated Treatment Process Upgrades Aeration Tanks (HPO) to Solids Handling Segregated Treatment Honeywell NaOH Screen Screen Screen Post Aeration DomesticWastewater SBS Denit Basin IndustrialWastewater RAS WAS to Solids Handling CCT Gravelly Run MBBR DAFT Grit Removal Grit Removal SecondaryClarifiers Domestic PCs Industrial PCs

29. 05 Project Status