Aeration, Destratification and Algae Control  in Governor Bond Lake Greenville, IL Matt Willman, City of Greenville John S...
Governor Bond Lake <ul><li>Built late 1968’s to serve as reservoir for City of Greenville (pop. 6,955) and other communiti...
Map of Gov Bond Lake
Issues <ul><li>Phosphorus and Nitrogen enter the lake from farm fertilizer runoff </li></ul><ul><li>Phosphorus is a major ...
Issues for City of Greenville <ul><li>Complaints from Rate payers on Odor and Taste of Water (earthy taste and musky smell...
Prior Attempts at Gov Bond Lake for Aeration and Turnover Mixing <ul><li>Air Sparing systems – caused increases in turbidi...
Successful Experimental Aeration System in 1996 <ul><li>A venturi-type eductor-jet was used at Lake Evergreen (Bloomington...
Use similar design from Lake Evergreen Study <ul><li>A venturi-type eductor-jet aerator would be used. </li></ul><ul><li>U...
Design Criteria <ul><li>Richardson Stability Number – a unitless index measuring a lake’s mixing potential </li></ul><ul><...
Theory of Operation <ul><li>Stratification occurs because of differences in densities between hypolimnion and epilimnion <...
 
Piping <ul><li>100 ft 8” HDPE Suction Intake Piping  (change from original design to save money)  at 502’ elevation but al...
Unique suction Manifold <ul><li>A suction manifold in the hypolimnion extracts stratified water into the pump and aerator ...
Suction Manifold
 
 
 
 
 
Venturi Eductor <ul><li>Located on lake bottom at elevation 501’ </li></ul><ul><li>Discharge nozzle 3’ above bottom minimi...
 
Dynamic Influence of lake surface <ul><li>Ripples caused by the rising water column ensure continuous air exchange at the ...
Temp and Dissolved Oxygen 2008
Change in dissolved oxygen
Phosphorus 1999 vs. 2008
Changes in Raw water:  pH, Alkalinity and Turbidity <ul><li>JULY 2007 averages </li></ul><ul><li>pH  = 8.4  [low 7.7  - hi...
Changes in Finished Water Quality <ul><li>JULY 2007 averages </li></ul><ul><li>pH  = 9.3  [low 8.4  - high 9.4] </li></ul>...
Summary After System Installation <ul><li>Richardson Stability No.  Δ  7 vs. 6,388 </li></ul><ul><li>Elimination of thermo...
Subsequent Changes to System <ul><li>Gate Valve – added in 2009 to protect the pump from cavitation </li></ul><ul><li>VFD ...
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Aeration And Destratification In Governor Bond Lake

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A PPS that discusses a successful project to destratify a reservoir in Illinois

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Aeration And Destratification In Governor Bond Lake

  1. 1. Aeration, Destratification and Algae Control in Governor Bond Lake Greenville, IL Matt Willman, City of Greenville John Salonich, Venturi Aeration, Inc.
  2. 2. Governor Bond Lake <ul><li>Built late 1968’s to serve as reservoir for City of Greenville (pop. 6,955) and other communities in Bond County (tot. 18,253) </li></ul><ul><li>Lake Surface covers approx. 775 acres divided by a causeway </li></ul><ul><li>Lake is bordered by city owned land, small estates, planned communities and small family farms </li></ul><ul><li>Stocked for fishing (catfish, bass, bluegill, et. al.) </li></ul>
  3. 3. Map of Gov Bond Lake
  4. 4. Issues <ul><li>Phosphorus and Nitrogen enter the lake from farm fertilizer runoff </li></ul><ul><li>Phosphorus is a major contributor to algal blooms which deplete O 2 in the lake during hot summer months </li></ul><ul><li>Algal blooms (blue-green algae or cyanobacteria) contribute to fish kills and degrade water quality—taste and odor </li></ul><ul><li>A severe Thermocline was evident in summer months due to lack of natural Turnover </li></ul>
  5. 5. Issues for City of Greenville <ul><li>Complaints from Rate payers on Odor and Taste of Water (earthy taste and musky smell) </li></ul><ul><li>Algal Blooms (risk of toxicity) </li></ul><ul><li>A large Fish Kill (lack of Dissolved Oxygen and excessive N and P) </li></ul><ul><li>A Stratified lake causes stagnation and an anoxic bottom layer releasing Phosphorus promoting Algal blooms </li></ul>
  6. 6. Prior Attempts at Gov Bond Lake for Aeration and Turnover Mixing <ul><li>Air Sparing systems – caused increases in turbidity and lifted H 2 S in sediment off bottom (discontinued after two weeks 7/7 to 7/17 2005 - influenced only 20 surface acres) </li></ul><ul><li>Floating Surface Aerator – caught in own anchor lines as lake volume decreased also increased turbidity in lake by drafting sediment off bottom </li></ul>
  7. 7. Successful Experimental Aeration System in 1996 <ul><li>A venturi-type eductor-jet was used at Lake Evergreen (Bloomington, IL) with reasonable success </li></ul><ul><li>Improved the lake’s: physical, chemical and biological water quality characteristics </li></ul><ul><li>Enhanced water quality taste and eliminated odors </li></ul>
  8. 8. Use similar design from Lake Evergreen Study <ul><li>A venturi-type eductor-jet aerator would be used. </li></ul><ul><li>Unlike Lake Evergreen a decision not to have power cable in the lake (caused extended outages at Lake Evergreen) and required helicopter to lift out assembly for repair </li></ul><ul><li>No submerged pump on lake bottom </li></ul><ul><li>Pump on shore for easy PM servicing </li></ul>
  9. 9. Design Criteria <ul><li>Richardson Stability Number – a unitless index measuring a lake’s mixing potential </li></ul><ul><li>Gov. Bond’s Summer R i was 6,388 which represents a highly stratified condition </li></ul><ul><li>Using a flow of ~1300 gpm equates to 1,872,000 gpd aerated and moved from hypolimnion to epilimnion zone drafting an equal or greater volume with the rising aerated water column </li></ul>
  10. 10. Theory of Operation <ul><li>Stratification occurs because of differences in densities between hypolimnion and epilimnion </li></ul><ul><li>Blend the stratified water by mixing the hypolimnion water into epilimnion equalizing temperature and minimizing dissolved oxygen differences </li></ul><ul><li>Minimize differences in water densities and temperature </li></ul>
  11. 12. Piping <ul><li>100 ft 8” HDPE Suction Intake Piping (change from original design to save money) at 502’ elevation but allows water near WTP intake to be treated </li></ul><ul><li>350 Ft 8” SDR 21 PVC piped to venturi aerator at 501’ elevation (lake bottom) </li></ul>
  12. 13. Unique suction Manifold <ul><li>A suction manifold in the hypolimnion extracts stratified water into the pump and aerator </li></ul><ul><li>Located above the organics and silt to inhibit their resuspension which occurs with other technologies </li></ul>
  13. 14. Suction Manifold
  14. 20. Venturi Eductor <ul><li>Located on lake bottom at elevation 501’ </li></ul><ul><li>Discharge nozzle 3’ above bottom minimize disturbance of sedimentary oragnics </li></ul><ul><li>Creates aerated rising water column </li></ul><ul><li>Drafts >2x’s additional water in hypolimnion to surface to effect Turnover </li></ul>
  15. 22. Dynamic Influence of lake surface <ul><li>Ripples caused by the rising water column ensure continuous air exchange at the air/liquid interface as a component of the mechanically induced Turnover </li></ul><ul><li>Causes air exchange in times that would otherwise be placid if there is no wind to effect air exchange </li></ul>
  16. 23. Temp and Dissolved Oxygen 2008
  17. 24. Change in dissolved oxygen
  18. 25. Phosphorus 1999 vs. 2008
  19. 26. Changes in Raw water: pH, Alkalinity and Turbidity <ul><li>JULY 2007 averages </li></ul><ul><li>pH = 8.4 [low 7.7 - high 9.1] </li></ul><ul><li>Alk = 111 [low 98 – high 122] </li></ul><ul><li>Turb = 17 [low 7 – high 132] </li></ul><ul><li>JULY 2010 averages </li></ul><ul><li>pH = 7.6 [low 7.2 - high 7.9] </li></ul><ul><li>Alk = 89 [low 78 – high 110] </li></ul><ul><li>Turb = 8 [low 6 – high 14] </li></ul>
  20. 27. Changes in Finished Water Quality <ul><li>JULY 2007 averages </li></ul><ul><li>pH = 9.3 [low 8.4 - high 9.4] </li></ul><ul><li>Alk = 38 [low 24 – high 48] </li></ul><ul><li>Turb = 0.17 [low 0.11 – high 0.26] </li></ul><ul><li>JULY 2010 averages </li></ul><ul><li>pH = 7.5 [low 7.2 - high 7.9] </li></ul><ul><li>Alk = 36 [low 28 – high 56] </li></ul><ul><li>Turb = 0.10 [low 0.05 – high 0.16] </li></ul>
  21. 28. Summary After System Installation <ul><li>Richardson Stability No. Δ 7 vs. 6,388 </li></ul><ul><li>Elimination of thermocline due to efficient mixing to < 3˚C at 21’ Temperature uniformity </li></ul><ul><li>Residual DO levels at 6 mg/L or> </li></ul><ul><li>Reduced turbidity while aerating and mixing –organic bottom undisturbed </li></ul><ul><li>Enhances the taste and eliminates odors in finished water </li></ul><ul><li>1 system is treating ~300+ acres SW of causeway </li></ul><ul><li>Elimination of algal blooms </li></ul>
  22. 29. Subsequent Changes to System <ul><li>Gate Valve – added in 2009 to protect the pump from cavitation </li></ul><ul><li>VFD – added in 2010 for energy savings </li></ul>

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