1. Energy Efficiency Opportunities at Wastewater Treatment Facilities UW – Madison Class November 3, 2010 Focus on Energy Joseph Cantwell, P.E.

2. Economic Benefits of Efficiency Reduces the need for new power plants New power plant cost >$3,000/kW Efficiency program cost <$500/kW Reduced environmental impacts, including $$

3. Why? Why energy? – Limited resource – Costs are increasing – Major component of facility budgets – Can be managed Why Water & Wastewater? – Facilities consume 35% of energy used by municipalities – Operation is 24/7 – W/WW energy costs are $9 billion/yr – W/WW consume 70 billion kWh/yr

4. Energy Baseline Find out where you’re at (baseline)... …so you can figure out where you want to go (benchmark).

5. Implementation Value  Single shift – (8 hrs/day) (5 days/wk) (52 wks/yr) = 2,080 hrs/yr  Continuous – (24 hrs/day) (365 days/yr) = 8,760 hrs/yr  8,760 hrs/yr / 2,080 hrs/yr = 4.2

6. Electricity Requirement for Typical Activated Sludge Facilities (WEF)

7. Water/Wastewater Approach Site surveys — How performed Data requested Discussions with operators Assessment approach Assessment report

8. Assessment Approach Explore major energy uses Address facility operations Modify/adjust operations Level of interest of operator Acceptance of assessment Cooperation to implement

9. Data to Gather Energy bills Demand consumption Size of treatment units Design memorandum Existing loading information Effluent limits Site input Equipment data

10. Basic Assessments Plot energy consumption and demand Percent loading – components and systems Variability of process equipment Variation in loading hourly/daily/weekly Distribution of energy consumption Obtain Amp, Watt or DO readings Meet and review operations with site personnel

11. Identified Energy Saving Opportunities Wastewater  Aeration  Pumping  Variable Speed Drives  Automatic Controls  Solids Management  Operation  Equipment Selection Water  Pressure  Throttled Valves  Drives  Controls  Pumps  Operation

12. Electric Energy Bill Basics Kilowatt (kW) = Power or Electric Demand ─ kW is measured over 15-minute periods (averaged kW) ─ Equals KWH measured over 15 minutes * 4 KWH (Kilowatt hour) = Energy Used ─ KWH = kW * hours ─ On-peak kWh = kWh used during weekday ─ Off-peak kWh = kWh used during weeknight and weekends

13. Demand-side management Demand  Learn when “on-peak” demand is  Review when changes in equipment occur  Schedule maintenance/equipment tests  Maintenance operations (welding, pump station cleaning, filter backwashing)  Treating hauled in wastes

14. Impact on demand Demand  Change in blowers  Change in pumps  Utilize standby generator  Interior and exterior lighting  Exercising equipment  Stagger large energy processes

15. Understand Electric Demand

18. Aeration

19.  Organic loading Biochemical oxygen demand (BOD) Ammonia  Mixing 0.125 cfm/SF 0.25 cfm/SF  Aeration “capability” to meet code  Diffuser density  Flexibility of blower selection  Existing and design loading Must assess:

20. Effect of bubble size The smaller the bubbles, the larger the area-to-volume ratio The smaller the bubbles, the slower the bubble rise rate Smaller bubbles have more surface area and longer residence time in the liquid. Both increase the clean water oxygen transfer. Aeration

21. Bubble size comparison One hundred seventy-five golf balls fit into the volume of a basketball. So, with the same volume, you increase the surface area for O 2 transfer by about 5.6 times. 434.9/2.5 = 175 175 X 8.9 = 1557.5/277.6 = 5.6 Diameter (in) Surface area (in 2 ) Volume (in 3 ) Golf ball1.78.92.5 Baseball2.925.812.3 Basketball9.4277.6434.9 Aeration

22. Energy Savings from DO Management ActualSetpointSavings DO Fraction% 22-- 321/812.5 422/825 523/837.5 624/850 725/867.5 826/875

23. Aeration 1.Aeration Tank Volume: 50 ft x 250 ft x 18 ft = 225,000 ft 3 2.Floor Area: 50 ft x 250 ft x 0.125 cfm/ft 2 = 1,563 cfm (Mixing) 3. Code (air rate capability)@ 20 cfm/1000 ft 3 = 4,500 cfm (Mixing) 4. Organic Loading: (3.5 MGD) BOD = 4,500 lb/day & NH 3 = 625 lb/day (4,500 lb/day x 1.1lbO 2 /BOD x ft 3 /0.0172 lbO 2 /ft 3 air x day/1440 min)/0.20 eff = 1,000 cfm (625 lb/day x 4.6 lbO 2 /lbNH 3 x ft 3 /0.0172 lbO 2 /ft 3 air x day/1440 min)/0.20 eff = 580 cfm 1,000 cfm + 580 cfm = 1,580 cfm EXAMPLE – AERATION CONTROL PARAMETER

24. Aeration Organic Loading Controlled @ 1,580 cfm: 1,580cfm @8.5 psi = 75 hp x (0.746 kWh/hp/0.90 eff ) x 8,760 hr/yr x $0.08/kWh = $43,570/yr Mixing (use 20 cfm/1000 ft 3 ) 4,500cfm @8.5 psi = 200hp x (0.746 kWh/hp/0.90 eff ) x 8,760 hr/yr x $0.08/kWh = $104,240/yr SAVINGS = $60,670/yr EXAMPLE – AERATION CONTROL PARAMETER

25. Energy Intensive Processes - Pumping

26. Pump performance curve Drive (if applicable) Motor specifications Design information Amp draw (field-measured) Existing flow conditions Discussion with operations personnel System components – Static – Dynamic – conveyance configuration Pumping Assessment

27. Pumping System Efficiency Range of Eff. LowAveHigh Motor85-95.85.9.95 Drive20-98.20.6.98 Pump30-85.30.6.85 Eff. of System.05.32.80 5 to 80%

28. Variable speed pump selection Energy-Intensive Processes - Pumping

29. Energy Savings Obtained Through Installed Projects Oxidation Ditch

30. Energy Savings Obtained Through Installed Projects Package Plant

31. Energy Savings Obtained Through Installed Projects Activated Sludge

33. Ensuring a Sustainable Future: An Energy Management Guidebook for Wastewater and Water Utilities http://www.epa.gov/waterinfrastructure/bettermanagement_energy. html

34. Energy Benchmarking MGD = million gallons per day Source: Focus on Energy," Water and Wastewater Energy Best Practice Guidebook”

35. Energy Savings Identified

36. What We Learned with Focus Energy Awareness – Management Knowledge of energy use is critical Energy efficiency w/o impact to effluent limits Significant savings available System assessment necessary Savings are long-term Publicize the need for energy efficiency

37. What We “Also” Learned with Focus Must overcome barriers Designers need to become aware of value Need to address electric charge rates Need to develop more training in energy efficiency Require energy efficiency/education for certification Agencies need to address energy efficiency

38. Design  Design development needs to be energy efficient from start up through design life of system

39. Operation  Does all equipment need to be in operation?  Flexibility in equipment selection  Range of operation  Energy efficient throughout range

40. Aerated Lagoons

41. Wastewater Treatment Facility An aerated lagoon wastewater treatment facility consisting of three lagoons (two aerated and one settling). The two aerated lagoons work by using helixor aerators with three 40 hp blowers. The annual electric consumption was 494,710 kWh/yr, relating to 7,340 kWh/million gallons. The village installed a new fine-bubble diffusion system and reduced the speed of the existing blowers. Resulting in energy savings of 264,000 kWh/yr

42. Installed Projects ….

43. Assessed Project…

45. Municipal Wastewater Treatment Facility An activated sludge facility, oxidation ditch The WWTF is not loaded at design The annual electric consumption reduction potential was forecasted to be 200,000 kWh for aeration and 250,000 for mixing The Municipality changed operations to reduce on – peak electric consumption The Municipality has additional opportunities to reduce energy through more awareness of operational impact on energy consumption Assessed Project …

46. IF YOU HAVE QUESTIONS, PLEASE CONTACT: Joseph Cantwell, P.E. Focus on Energy/SAIC 1845 Derrin Lane Brookfield, WI 53045 Tel: (262) 786-8221 Fax: (262) 786-5925 cantwellj@saic.com