1. CEE 426 September 15 2010 12:05 PM UW Madison Room _____ Engineering Hall Energy in Wastewater Treatment Plants Thomas E. Jenkins, P.E. 1

2. Energy in Wastewater Treatment Plants “Energy costs can account for 30 percent of the total operation and maintenance (O&M) costs of WWTPs” US EPA 2

3. Uses of Energy in WWTPs. Sources of Energy in WWTPs. Energy Conservation and Reduction Opportunities in WWTPs. Examples – Darlington and Beloit WI Energy in Wastewater Treatment Plants 3

4. How much energy is used in a typical WWTP? Uses of Energy in WWTPs 4 Average Energy Use at Wisconsin WWTPs (Joe Cantwell, Wisconsin Focus on Energy) Treatment Type Flow Range mgd kWh per Million Gallons Activated Sludge 0-1 5,440 1 to 5 2,503 >5 2,288 All 3,954 Aerated Lagoon0 to 1 7,288 Oxidation Ditch0 to 1.2 6,895

5. How much energy SHOULD be used in a typical WWTP? Uses of Energy in WWTPs 5 Average Energy Use at Wisconsin WWTPs (Joe Cantwell, Wisconsin Focus on Energy) Treatment Type Flow Range mgd Actual kWh per Million Gallons Best Practices kWh per Million Gallons Potential Savings Activated Sludge 0-1 5,440 3,06044% 1 to 5 2,503 1,65034% >5 2,288 1,76023% All 3,954 Aerated Lagoon0 to 1 7,288 3,54051% Oxidation Ditch0 to 1.2 6,895 4,32037%

6. How big is in a typical WWTP? Uses of Energy in WWTPs 6 Operating Wastewater Treatment Plants in the U.S. (2004) Design Flow Range (MGD) Number of Facilities Total Existing Flow (MGD) % Facilities 0 – 0.100 6,830 29841.2% 0.101 – 1.000 6,431 2,32738.8% 1.001 – 10.000 2,771 8,76616.7% 10.001 – 100.000 503 13,2333.0% 100.001 and greater 41 9,0330.2% Other 7 - - Total 16,583 33,657 100%

7. What are the uses of energy in a typical WWTP? Uses of Energy in WWTPs 7

8. What are the uses of energy in a typical WWTP? Uses of Energy in WWTPs 8

9. Pumping Examples –WAS, RAS Raw Wastewater Conveyance, Effluent Aeration Examples –Blowers, Mechanical Aerators, Trickling Filters Uses of Energy in WWTPs 9

10. Energy use varies with time of day Why? Energy in WWTPs 10

11. Energy use varies with time of day Energy in WWTPs 11

12. Aeration is the Most Significant Use Energy in WWTPs 12

13. Half the power in most WWTPs goes to the aeration blowers Energy in WWTPs 13

14. What are the sources of energy in a typical WWTP? Sources of Energy in WWTPs 14

15. What are the sources of energy in a typical WWTP? Electricity Gas –Natural, LP Wastewater –Methane, Heat Sources of Energy in WWTPs 15

16. Electricity is the Most Significant source of energy in a WWTP Most is used to power motors –Blowers for Aeration –Pumps –Belt Presses, Conveyors, Misc. Unit Processes Also Lighting, HVAC, UV etc. Sources of Energy in WWTPs 16

17. Energy Cost ≠ Energy Use Electricity is Billed for: –Consumption kWh –Time of Day – Power is Cheap at Night –Peak Usage Gas is Billed on Consumption Energy in Wastewater Treatment Plants 17

18. What are ways to minimize Energy use? Energy Conservation in WWTPs 18

19. What are ways to minimize Energy use? Specify Energy Efficient Equipment Avoid over-design Use Advanced Controls Energy Conservation in WWTPs 19

20. Specify Energy Efficient Equipment –Diffusers –Blowers –Pumps –Motors –Lighting Energy Conservation in WWTPs 20

21. Avoid over-design This is the most common problem in design! Oversized Equipment can’t match energy to process requirements Overdesigned equipment is a challenge for operators Energy Conservation in WWTPs 21

22. Use Advanced Controls Automate Process Controls Use instrumentation to monitor process Provide Human Machine Interface (HMI) to allow operators to visualize operations Variable Frequency Drives (VFDs) Dissolved Oxygen (DO) Control Energy Conservation in WWTPs 22

23. Process Requirements Come First! Systems should be justified by payback Energy Conservation in WWTPs 23

24. Obstacles to Energy Conservation: Design “Safety Factors” and Unknowns –Fear of inadequate performance –Mis-applied or Inappropriate “Standards” –Don’t know precise loading Lack of Operator Information –Don’t know energy costs –Don’t know options Lack of Incentives –Meeting Permit only criteria –No advantage to beating budget Financial Constraints –Lack of Budget –Bidding Process Energy Conservation in WWTPs 24

25. Beloit, WI –Currently 5 blowers, two with VFDs –Objective is to reduce blower power –Assignment is to determine cost effectiveness of adding additional 4160 VAC VFDs Example Energy Conservation Projects 25

26. Darlington, WI –Currently oxidation ditches with mechanical aerators –Objective is to reduce aeration power –Assignment is to determine cost effectiveness of replacing mechanical aeration with diffused aeration Example Energy Conservation Projects 26

27. Energy in Wastewater Treatment Plants Questions? 27