Aeration, Destratification Aeration, Destratification and Algae Control and Algae Control

in Governor Bond Lakein Governor Bond LakeGreenville, ILGreenville, IL

Matt Willman, City of GreenvilleMatt Willman, City of Greenville

John Salonich, Venturi Aeration, John Salonich, Venturi Aeration, Inc.Inc.

Governor Bond LakeGovernor Bond Lake

Built late 1968’s to serve as reservoir for Built late 1968’s to serve as reservoir for City of Greenville (pop. 6,955) and other City of Greenville (pop. 6,955) and other communities in Bond County (tot. 18,253)communities in Bond County (tot. 18,253)

Lake Surface covers approx. 775 acres Lake Surface covers approx. 775 acres divided by a causewaydivided by a causeway

Lake is bordered by city owned land, small Lake is bordered by city owned land, small estates, planned communities and small estates, planned communities and small family farmsfamily farms

Stocked for fishing (catfish, bass, bluegill, Stocked for fishing (catfish, bass, bluegill, et. al.)et. al.)

Map of Gov Bond LakeMap of Gov Bond Lake

IssuesIssues Phosphorus and Nitrogen enter the lake Phosphorus and Nitrogen enter the lake

from farm fertilizer runofffrom farm fertilizer runoff Phosphorus is a major contributor to algal Phosphorus is a major contributor to algal

blooms which deplete Oblooms which deplete O22 in the lake during in the lake during hot summer months hot summer months

Algal blooms (blue-green algae or Algal blooms (blue-green algae or cyanobacteria) contribute to fish kills and cyanobacteria) contribute to fish kills and degrade water quality—taste and odordegrade water quality—taste and odor

A severe Thermocline was evident in A severe Thermocline was evident in summer months due to lack of natural summer months due to lack of natural TurnoverTurnover

Issues for City of GreenvilleIssues for City of Greenville

Complaints from Rate payers on Complaints from Rate payers on Odor and Taste of Water (earthy Odor and Taste of Water (earthy taste and musky smell)taste and musky smell)

Algal Blooms (risk of toxicity)Algal Blooms (risk of toxicity) A large Fish Kill (lack of Dissolved A large Fish Kill (lack of Dissolved

Oxygen and excessive N and P)Oxygen and excessive N and P) A Stratified lake causes stagnation A Stratified lake causes stagnation

and an anoxic bottom layer releasing and an anoxic bottom layer releasing Phosphorus promoting Algal bloomsPhosphorus promoting Algal blooms

Prior Attempts at Gov Bond Lake for Prior Attempts at Gov Bond Lake for Aeration and Turnover MixingAeration and Turnover Mixing

Air Sparing systems – caused Air Sparing systems – caused increases in turbidity and lifted Hincreases in turbidity and lifted H22S S in sediment off bottom in sediment off bottom (discontinued (discontinued after two weeks 7/7 to 7/17 2005 - after two weeks 7/7 to 7/17 2005 - influenced only 20 surface acres)influenced only 20 surface acres)

Floating Surface Aerator – caught in Floating Surface Aerator – caught in own anchor lines as lake volume own anchor lines as lake volume decreased also increased turbidity in decreased also increased turbidity in lake by drafting sediment off bottomlake by drafting sediment off bottom

Successful Experimental Aeration Successful Experimental Aeration System in 1996System in 1996

A venturi-type eductor-jet was used A venturi-type eductor-jet was used at Lake Evergreen (Bloomington, IL) at Lake Evergreen (Bloomington, IL) with reasonable successwith reasonable success

Improved the lake’s: physical, Improved the lake’s: physical, chemical and biological water quality chemical and biological water quality characteristicscharacteristics

Enhanced water quality taste and Enhanced water quality taste and eliminated odorseliminated odors

Use similar design from Lake Use similar design from Lake Evergreen StudyEvergreen Study

A venturi-type eductor-jet aerator A venturi-type eductor-jet aerator would be used.would be used.

Unlike Lake Evergreen a decision not Unlike Lake Evergreen a decision not to have power cable in the lake to have power cable in the lake (caused extended outages at Lake (caused extended outages at Lake Evergreen) and required helicopter Evergreen) and required helicopter to lift out assembly for repairto lift out assembly for repair

No submerged pump on lake bottomNo submerged pump on lake bottom Pump on shore for easy PM servicingPump on shore for easy PM servicing

Design CriteriaDesign Criteria

Richardson Stability Number – a unitless Richardson Stability Number – a unitless index measuring a lake’s mixing potentialindex measuring a lake’s mixing potential

Gov. Bond’s Summer RGov. Bond’s Summer Rii was 6,388 which was 6,388 which represents a highly stratified conditionrepresents a highly stratified condition

Using a flow of ~1300 gpm equates to Using a flow of ~1300 gpm equates to 1,872,000 gpd aerated and moved from 1,872,000 gpd aerated and moved from hypolimnion to epilimnion zone drafting an hypolimnion to epilimnion zone drafting an equal or greater volume with the rising equal or greater volume with the rising aerated water columnaerated water column

Theory of OperationTheory of Operation Stratification occurs because of Stratification occurs because of

differences in densities between differences in densities between hypolimnion and epilimnionhypolimnion and epilimnion

Blend the stratified water by mixing Blend the stratified water by mixing the hypolimnion water into the hypolimnion water into epilimnion equalizing temperature epilimnion equalizing temperature and minimizing dissolved oxygen and minimizing dissolved oxygen differences differences

Minimize differences in water Minimize differences in water densities and temperaturedensities and temperature

PipingPiping 100 ft 8” HDPE Suction Intake Piping 100 ft 8” HDPE Suction Intake Piping

(change from original design to save (change from original design to save money)money) at 502’ elevation but allows at 502’ elevation but allows water near WTP intake to be treatedwater near WTP intake to be treated

350 Ft 8” SDR 21 PVC piped to 350 Ft 8” SDR 21 PVC piped to venturi aerator at 501’ elevation venturi aerator at 501’ elevation (lake bottom)(lake bottom)

Unique suction ManifoldUnique suction Manifold

A suction manifold in the A suction manifold in the hypolimnion extracts stratified water hypolimnion extracts stratified water into the pump and aeratorinto the pump and aerator

Located above the organics and silt Located above the organics and silt to inhibit their resuspension which to inhibit their resuspension which occurs with other technologiesoccurs with other technologies

Suction ManifoldSuction Manifold

Venturi EductorVenturi Eductor

Located on lake bottom at elevation Located on lake bottom at elevation 501’501’

Discharge nozzle 3’ above bottom Discharge nozzle 3’ above bottom minimize disturbance of sedimentary minimize disturbance of sedimentary oragnicsoragnics

Creates aerated rising water columnCreates aerated rising water column Drafts >2x’s additional water in Drafts >2x’s additional water in

hypolimnion to surface to effect hypolimnion to surface to effect TurnoverTurnover

Dynamic Influence of lake surfaceDynamic Influence of lake surface

Ripples caused by the rising water Ripples caused by the rising water column ensure continuous air column ensure continuous air exchange at the air/liquid interface exchange at the air/liquid interface as a component of the mechanically as a component of the mechanically induced Turnoverinduced Turnover

Causes air exchange in times that Causes air exchange in times that would otherwise be placid if there is would otherwise be placid if there is no wind to effect air exchangeno wind to effect air exchange

Temp and Dissolved Oxygen 2008Temp and Dissolved Oxygen 2008

Change in dissolved oxygenChange in dissolved oxygen

Phosphorus 1999 vs. 2008Phosphorus 1999 vs. 2008

Changes in Raw water: Changes in Raw water: pH, Alkalinity and TurbiditypH, Alkalinity and Turbidity

JULY 2007 averagesJULY 2007 averages pH = 8.4 [low 7.7 - high 9.1]pH = 8.4 [low 7.7 - high 9.1] Alk = 111 [low 98 – high 122]Alk = 111 [low 98 – high 122] Turb = 17 [low 7 – high 132]Turb = 17 [low 7 – high 132]

JULY 2010 averagesJULY 2010 averages pH = 7.6 [low 7.2 - high 7.9]pH = 7.6 [low 7.2 - high 7.9] Alk = 89 [low 78 – high 110]Alk = 89 [low 78 – high 110] Turb = 8 [low 6 – high 14]Turb = 8 [low 6 – high 14]

Changes in Finished Water QualityChanges in Finished Water Quality

JULY 2007 averagesJULY 2007 averages pH = 9.3 [low 8.4 - high 9.4]pH = 9.3 [low 8.4 - high 9.4] Alk = 38 [low 24 – high 48]Alk = 38 [low 24 – high 48] Turb = 0.17 [low 0.11 – high 0.26]Turb = 0.17 [low 0.11 – high 0.26]

JULY 2010 averagesJULY 2010 averages pH = 7.5 [low 7.2 - high 7.9]pH = 7.5 [low 7.2 - high 7.9] Alk = 36 [low 28 – high 56]Alk = 36 [low 28 – high 56] Turb = 0.10 [low 0.05 – high 0.16]Turb = 0.10 [low 0.05 – high 0.16]

Summary After System InstallationSummary After System Installation Richardson Stability No. Richardson Stability No. ΔΔ 7 vs. 6,388 7 vs. 6,388 Elimination of thermocline due to efficient Elimination of thermocline due to efficient

mixing to < 3˚C at 21’ Temperature mixing to < 3˚C at 21’ Temperature uniformityuniformity

Residual DO levels at 6 mg/L or>Residual DO levels at 6 mg/L or> Reduced turbidity while aerating and Reduced turbidity while aerating and

mixing –organic bottom undisturbedmixing –organic bottom undisturbed Enhances the taste and eliminates odors in Enhances the taste and eliminates odors in

finished waterfinished water 1 system is treating ~300+ acres SW of 1 system is treating ~300+ acres SW of

causewaycauseway Elimination of algal bloomsElimination of algal blooms

Subsequent Changes to SystemSubsequent Changes to System

Gate Valve – added in 2009 to Gate Valve – added in 2009 to protect the pump from cavitationprotect the pump from cavitation

VFD – added in 2010 for energy VFD – added in 2010 for energy savingssavings