Upgrading MSD's Facility Plan: Goals, Scope, and Innovations

1. NC AWWA-WEA Annual Conference November 17, 2015 Planning for the Future --- MSD’sFacility Plan Update Peter Weed and Hunter Carson, MSD Mary Knosby, HDR

2. Agenda • MSD & WRF Background • Need for Facility Plan Update • Goals, Objectives, Drivers • Project Scope • Facility Plan Update • RBC Replacement • Next Steps / Implementing the Plan

3. MSD History MSD is a municipal corporation created by State Statute in 1962 serving most of Buncombe County (Asheville and surrounding towns) and part of Henderson County. The original treatment plant went online in 1967 with only 30 miles of interceptor. The collection system spans over 1000 miles of pipe due to consolidation with local systems expansion. Prior to 1967 all collected sewage was discharged untreated straight into the French Broad River.MSD owns and operates the public sewer system and is solely supported by its ratepayers.

4. Original treatment plant… 25MGD rated

5. Green energy – circa 1916

6. Expanded to 40 MGD in 1985

7. Largest Rotating Biological Contactor (RBC) plant operating – 152 units Redesigned in the 80’s with aerated grit removal, primary & secondary microscreens, and RBC’s. Utilizing “innovative” technologies qualified MSD for 80% federal grant funding. …but not everything innovative always works as planned; and revising plans may never end. WRF redesigned for “Innovation”

8. Need and Scope of Facility Plan Update • Follow-up to 2007 Facility Plan • MSD needed updated recommendations on various aging and failing processes • Grit Removal System • Biological Treatment – near term and long term • Primary Clarification

9. Failing Grit Removal System Post-Cleaning Pre-Cleaning Installed in 1988 Upgraded in 2008 with new classifiers and new air diffuser blowers Substantial amount of grit being conveyed to downstream processes RBC Basins require cleaning every 3-5 years – $120k+

10. Biological Treatment – Near Term • RBCs installed in 1988 and continue to perform well and meet NPDES permit limits for BOD and TSS • Prior to Facility Plan Update, 35 of 152 RBC units out of service (23%) • MSD is interested in ways to preserve existing units and delay major capital expenditures • Procure used RBCs units • Replace isolation gates to dry media and reduce shaft weight • Primary Clarification

11. Need for Primary Clarification Reduce BOD and Solids loading on RBCs 30-40% BOD removal may extend life of RBCs (by reducing weight) and allow for better biological treatment Removal of solids (both settleable and suspended) will improve downstream processes (i.e. RBCs, Clarifiers, Cloth Media Filters) and will increase sludge btu value for incineration

12. Ammonia Reduction Evaluation and Long Term Biological Treatment • As part of NPDES renewal, NCDENR required MSD to evaluate feasibility and cost of: • Optimizing ammonia removal at the current plant via operational improvements • Upgrading the plant to meet summer ammonia limits of 6.9 mg/l and winter limits of 17mg/L (monthly averages) • MSD currently has no nutrient limits, but expects Ammonia or Total N limits in future permit cycles • Facility Plan Update to address these treatment challenges with current facility

13. Facility Plan Update

14. Facility Plan Update Site constraints Wet weather Headworks issues Primary constraints Hydraulics RBCs Long term biological Phasing and sequencing Ammonia Reduction Evaluation

15. Facility Plan Update Insert final site plan (discuss “backwards”)

16. Project Summary • Facility Assessment • Regulatory Assessment • Establish Planning Criteria • Preliminary & Primary Treatment • Biological Treatment • Short-term, phased, long-term, regulatory • Interim RBC retrofit plan • Actifloand CoMag Pilot Testing • Ammonia Reduction Evaluation

17. Evaluation Assumptions/Recommendations • System upgrades performed in process order • Facilitate operations • Allow elevation of hydraulic profile • Influent pumping, Fine screening, Grit removal, and Primary Treatment improvements will be implemented prior to biological process upgrade • Influent Screening and Pumping Station • ¾” screens can be replaced with ½” traveling rake and hinged overflow plate • At least 2 influent pumps will be replaced/upgraded with higher trimmed impellers • Fine Screening • ¼” Perforated plate

18. Evaluation Assumptions/Recommendations • Grit Removal • Forced Vortex • Not necessary to maximize removal efficiency of the finer grit • Surge/Equalization system • Limits peak flow to 65 mgd, while treating 80 mgd through the screening and grit facility • Primary Treatment • Chemically Enhanced High Rate Primary Treatment recommended (site constraints) • Target performance

19. Evaluation Assumptions/ Recommendations, cont’d • Restoration of the RBC process • Transitional upgrade strategy • Long-term biological alternatives are sized based on achieving ammonia reduction scenarios • Activated Sludge All options assume • MBBReliminating • IFASthe Intermediate PS

20. Recommended Near-Term Improvements • Replacement of Broken RBCs • Ongoing • Fine screening • Grit Removal Improvements • Surge EQ for Wet Weather Flow Management • Primary Treatment • 5-10 years for near-term improvements

21. Recommended Site Layout

22. Biological Upgrade Strategy • Continue with the option for quarterly chronic toxicity monitoring as continued option for compliance with the existing ammonia toxicity policy. • Allows time needed to: • Complete the RBC optimization program • Phased near-term improvements • Conduct a monitoring program to quantify additional ammonia removal achieved. • Consider alternative biological treatment processes for enhanced ammonia removal • If additional ammonia reduction required beyond what the optimized treatment process can achieve • When the RBCs have reached the end of their useful life

23. Biological Treatment Upgrade Evaluation Approach • Summary of Influent Flows / Load Development for 40 mgd permitted capacity • Effluent objectives • Numerical NH3-N targets • Size for year-round nitrification • Assume near-term phased improvements completed • Assume NH3-N limit would not be in place until biological upgrades complete • Critical for MOPO plan

24. Conceptual Development of Long-Term Biological Alternatives • Screening / initial evaluation process • Three feasible long-term biological alternatives • Conventional Activated Sludge Nitrification in Basin 2 with Pre-Anoxic in Basin 1 • Maintain RBCs in Basin 1 for CBOD removal and install Nitrifying MBBR in Basin 2 with future transition to a pre-anoxic zone in Basin 1 • Conversion to IFAS Process with Pre-Anoxic Zone in Basin 1 • Pre-anoxic zone included for alkalinity recovery

25. MBBR Alt, with Basin 1 as Pre-Anoxic

26. Replacing RBC’s can be very costly… or maybe not (?) Extend the life of current assets Over 25% of the RBC’s have failed – 40 units

27. RBC Replacement Replacement RBC from Parkersburg, VA at 10% cost of new Sometimes the way forward can look a lot like stepping back…

28. Running smoothly

29. And what’s next? Next Steps / Implementing the Plan

30. Facility Plan Implementation Incinerator Upgrade (in construction) NPDES permit renewal (in progress) Headworks / Preliminary Treatment Improvements project (in design) Additional RBC Replacements (April 2016) High Rate Primary Treatment project Re-evaluate biological upgrade options and timing

31. Discussion