Moving Bed Biofilm Reactor Retrofit for Ammonia and Nitrate Removal

1. Moving Bed Biofilm Reactor Retrofit for Ammonia and Nitrate Removal B&V SACWSD Lela Parsons, P.E. Greg Fabisiak Mark Maxwell, P.E. Joan Chavez 2002 RMSAWWA / RMWEA ANNUAL CONFERENCE

2. Phase 2 Project Components • Wastewater Collection System Master Plan • Utility Plan • Preliminary Design Report • Detailed Plans & Specifications • Contract Administration

3. Utility Plan Goals • Provide information required by DRCOG and for SRF Funding • Evaluation of existing facilities • Population & flow projections • Environmental assessment to support FNSI • Alternative analysis and recommendations • Implementation and financial plans • Public participation • Determine necessary wastewater facilities for capacity and regulatory compliance through 2020

4. Site Layout

5. WM WWTP Existing Unit Processes East Trickling Filter Final Clarifiers Chlorination P Flow Splitter Discharge to South Platte River Raw Wastewater Dechlorination Mechanical Screenings Primary Clarifiers Rotating Biological Contactors P P Chlorination West Trickling Filter Final Clarifier Combined Primary & MBBR Sludge Accelerated Air Drying of Dewatered Biosolids Prior to Ultimate Disposal of Class A Product Degritting Gravity Thickener Anaerobic Digesters Deskins “Quick-Dry” Filtration SystemTM P

6. WM WWTP Existing Unit Process Capacities

7. Treatment Issues • Regulatory Compliance • Reclassification of the South Platte River requires additional disinfection • Updated model of Segment 15 of the South Platte River resulted in imposition of effluent ammonia limit • Current and Future Water Quality Concerns • Dissolved oxygen • Ammonia • Nitrates • Nutrients

8. MWRD Central Plant SACWSD Bear Creek Clear Creek Chatfield Reservoir River South Platte Burlington Ditch Diversion Centennial Sand Creek Cherry Creek Brighton Littleton- Englewood Glendale Future Sand Creek Satellite WWTP Segment 15 Segment 14 Segments 14 & 15 of South Platte River (Not shown are non-point sources, diversion dams, reaeration structures etc.) South Platte Dischargers

9. Treatment Issues (con’t) • WM WWTP Treatment Capacity • Surge in residential and commercial activity in the service area • Current treatment capacity of 4.4 mgd forecasted to only be sufficient through 2003 • Limited room for additional expansion at the existing site

10. SACWSD Future Plan • Complete Phase 2 expansion at WM WWTP by 2004 • Phase 2 will provide capacity until 2008 • New WWTP will be needed by 2009- could be regional WWTP or SACWSD WWTP • Upgrade WM WWTP when appropriate to meet future water quality regulations

11. WM WWTP Expansion • Increase treatment capacity from 4.4 to 7.0 mgd • Notice to proceed issued September 2002 • Short-term - capacity expansion allows growth while new WWTP is designed and constructed • Long-term - WM WWTP will continue to serve the southern area of the District

12. Phase 2 Improvements • Major Expansions • Secondary Treatment Process • Solids Handling Process • Additional Improvements • Replace Manual Bar Screen • Demolish RBCs • Upgrade Disinfection Facilities • Add Stand-by Power Capacity • Expand Administration Building/Garage

13. Activated Sludge Anoxic/oxic basins WAS Pumping Station and Blower Building New Aerobic Sludge Handling Centrifuge Aerated sludge holding Biological Nutrient Removal (future) Fixed Film MBBR Anoxic/oxic basins Blower Building Additional Anaerobic Solids Processing Convert secondary digester to primary digester New secondary digester Chemical Phosphorous Removal (future) Post Denitrification (future) Treatment Alternatives Alternative A Alternative B

14. Alternative A slightly less expensive Alternative A more operationally complex- requires separate solids handling process Alternative B will require chemical addition for future phosphorous removal SACWSD has always utilized and prefers fixed film processes Alternative Evaluation

15. Fixed film process manufactured by Kaldnes Employs high-density polyethylene plastic media, coarse bubble aeration, and sieves Biofilm grows on inside of the media Specific gravity of 0.96 150 ft2/ft3 media surface area 0.93 %/ft clean water oxygen transfer rate Selected Alternative: Moving Bed Biofilm Reactors

16. Design Conditions • 100 mg/L influent BOD • 2 anoxic and 2 oxic reactors in series • 60% fill in each reactor • Coarse bubble diffuser system in oxic reactors • Submersible propeller mixers in anoxic reactors • 4 mg/L summer DO concentration • 5 mg/L winter DO concentration • 200% internal recycle for nitrate removal

17. East Plant Effluent BOD5 reduction <10 mg/L Total ammonia reduction <2 mg-N/L (complete nitrification) Total nitrate reduction <10 mg-NO3/L (partial denitrification) Blended Effluent (East and West Plant) CBOD reduction <25 mg/L Total ammonia reduction <10 mg-N/L Treatment Requirements

18. Selected Alternative Flow Schematic East Trickling Filter Anoxic MBBR Oxic MBBR Final Clarifiers Chlorination P P Discharge to South Platte River Raw Wastewater Dechlorination Mechanical Screenings Primary Clarifiers P Flow Splitter P Chlorination West Trickling Filter Final Clarifier Combined Primary & MBBR Sludge Accelerated Air Drying of Dewatered Biosolids Prior to Ultimate Disposal of Class A Product Degritting Gravity Thickener Anaerobic Digesters Deskins “Quick-Dry” Filtration SystemTM P Existing Facilities Phase 2 New Phase 2 Modified

19. Operational Issues • Portion of primary effluent must be bypassed around existing trickling filter • Requires construction of a new flow splitter structure • Prevents hydraulic surcharging of underdrains • Assures sufficient soluble BOD for denitrification • Allows ETF pumping station to be taken out of service • Trickling filter snail accumulation • Installed an automatic, self-cleaning strainer with 1/8- inch openings at the ETF pumping station

20. Engineer’s Construction Cost Opinion Low Bid Price Difference Between High and Low Bids Total Project Costs $13,283,000 $12,774,000 $475,300