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Increasing Energy Efficiency at the Allegan WWTP

Increasing Energy Efficiency at the Allegan WWTP. MWEA/AWWA Joint Annual Conference August 19, 2010. Project Background. Current treatment plant built in the early 70’s Headworks, manual 1 ½” bar screen, grit removal system has not been operation for 25 years.

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Increasing Energy Efficiency at the Allegan WWTP

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  1. Increasing Energy Efficiency at the Allegan WWTP MWEA/AWWA Joint Annual Conference August 19, 2010

  2. Project Background • Current treatment plant built in the early 70’s • Headworks, manual 1 ½” bar screen, grit removal system has not been operation for 25 years. • Freezing at headworks during winter months.

  3. Project Background • Aeration basin 2 inoperable due to failed air header, failing air header and extensive weed growth the in grit and sludge in basin. • Fine bubble diffuser in aeration basins and underground sludge storage tank added in 1992 • Aeration basin 3 and clarifier added in 1995 for addition BOD capacity.

  4. Project Background • (3) 150Hp Hoffman blowers for 3 aeration basins. • No auto controls on blowers to track D.O. • Blowers and motors were in needed new bearings. • Aeration basin 3 utilized existing blower designed for basin 1/3 its size. • (2) 75hp centrifugal blowers were used on the aerobic digester, no timer or automated controls.

  5. Project Background • Centrifugal wasting pumps held together with wooden wedges, pumped 50gpm above rated capacity. • Centrifugal sludge transfer pumps were unable to move thickened sludge over 3% solids. • Significant Industrial flow from Perrigo Corporation with no pretreatment other than pH adjustment.

  6. Project Goals/Constraints • Rehabilitate/replace existing process equipment • Modify/improve activated sludge process to improve performance, increase efficiency and add organic treatment capacity for Perrigo • Accomplish improvements on existing site which is surrounded by floodplain, old municipal dump and Rockwell Superfund site (utilize existing tankage or build structures primarily above grade).

  7. Aeration Energy Efficiencies • Diffusers • Replaced fine bubble diffusers with new, more efficient diffusers in aeration basins 1 and 2.

  8. Aeration Energy Efficiencies • Energy Savings from Diffuser Replacement

  9. Aeration Energy Efficiencies • Energy Savings from Diffuser Replacement

  10. Aeration Energy Efficiencies • Energy Savings from Diffuser Replacement

  11. Aeration Energy Efficiencies • Sensors • Dissolved oxygen sensors were installed at the end of aeration tanks 1 and 2 to provide automatic feedback/control of blower inlet valves based on operator set D.O. control point.

  12. Design Point: 114 HP Operating Point: 70 HP Aeration Energy Efficiencies • Energy Savings from Automatic Blower Control • Savings of just over $5,000/yr for every 10 HP reduced

  13. Aeration Energy Efficiencies 3. Biological Nitrogen Removal • If nitrification is occurring in the aeration basins, nitrates (NO3) can be returned to the anoxic zone (no or low dissolved oxygen). • Bugs utilize oxygen in nitrates. • Nitrogen (N2) is released as a gas and oxygen needs are reduced in aeration basin.

  14. Aeration Energy Efficiencies • Basin configuration made returning nitrates very simple, and anoxic zone was already in place due to new divider wall. • External carbon source is sometimes required (in addition to raw sewage) for de-nitrification reaction to be optimal.

  15. Aeration Energy Efficiencies • We may not optimize this process, just get some added benefit at a low up-front cost. • After system is more fully loaded will test BNR process to determine if further optimization is desired.

  16. Septage/Treatment Energy Efficiency • Mix septage in aerated tank with waste-activated sludge. • Pump contents to sludge storage tank. • Decant from sludge tank back to liquid end of plant is treated in liquid process. • Load to the aeration system is reduced due to less flow and lower organic loading.

  17. Septage/Treatment Energy Efficiency • Energy Savings from Septage Treatment System • Sludge Decant: 140 mg/l CBOD • Septage: 4,550 mg/l CBOD • Estimated Annual Septage: 3,000,000 gallons

  18. Miscellaneous Efficiencies • Biological phosphorus removal system results in less sludge produced (less chemical deliveries). • Automatic flow control system for high flows routes flows to either the EQ tank or aeration tank 3 (standby tank) to maintain treatment efficiency of main treatment tanks.

  19. Miscellaneous Efficiencies • New Headworks • ¼” automatic fine screen • Self-cleaning wet well • High efficiency grit removal

  20. Miscellaneous Efficiencies • New clarifiers with energy dissipating influent well and stamford baffles • New RAS pumps with VFDs

  21. Miscellaneous Efficiencies • Replaced gaseous chlorine disinfection system with Ultraviolet Disinfection (no more chlorine gas or sodium bisulfite deliveries).

  22. Building Systems Efficiencies • New natural gas fed Pulse Boiler • Indoor lighting • Replaced all fluorescent bulbs (T12 to T8) • Occupancy sensors installed in new areas of building • Option to control multiple bulbs in each fixture • Outdoor lighting • Replace mercury vapor lights with 2 stage induction lighting with motion detector (10 pole mounted fixtures)

  23. Treatment Results • Average effluent results: • CBOD: 8 mg/l • SS: 17 mg/l • T. Phos. .6 mg/l • Septage receiving: • 250,000 gallons per month • CBOD: 4,500 mg/l • SS: 20,000 mg/l • Decant from aerated sludge storage: • CBOD: 140 mg/l • SS: 218 mg/l

  24. Operational Efficiencies • New SCADA system provides full automation of plant • Automatic sludge wasting • Automatic sludge pumping • PD Sludge Blower control • UV control pacing • Automated headworks (fine screen control, grit collection, raw sewage pumps) • Personnel requirements • More duties (e.g. septage operation), less personnel • 1990’s: total of 5 staff • Present: total of 3 (possibly 4) staff

  25. Original POTW Found • The wastewater plant that was built in the 1930’s was located during construction. • It was supposed to have been removed and filled.

  26. Increasing Energy Efficiency at the Allegan WWTP MWEA/AWWA Joint Annual Conference August 19, 2010

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