Lake Restoration Using Aeration and Alum: When Watershed Management is Not Enough Patrick Goodwin Research Biologist M.S. Lake Management Candidate

Affordability Technical effectiveness Institutional acceptability 3 legged stool of lake management

Study location: Bahia del Mar– St. Petersburg, FL Brackish Water Lake Area: 14 Acres Max Depth 51ft Man-Made Borrow Pit

Major Issues: Internal Loading Poor Water Clarity Low DO, Odor, Fish Kills Intense algal blooms

Understanding the Watershed Seepage Lake Small Watershed Seepage Lakes v 100% urban High WRT

Understanding the Watershed Dillon & Chanton., 2005 Precipitation: 47.5 to 199 μg/L PO4 229 to 3,472 μg/L NO3 Stormwater Run-off: 332 to 1,310 μg/L PO4 211 to 40,176 μg/L NO3 Average P in Precipitation Florida ~50 µg/L (eutrophic) North East ~20 µg/L (mesotrophic) Nutrient levels in Rainwater and Urban Run-off, FL? Seepage Lakes

Understanding the Watershed A Lake is Only as Good as it’s Reference Condition!

1.Internal Vs. External Nutrient Loading Reducing External loading doesn’t always mean an Improved lake. (Forsberg, 1988; Sas et al., 1989; Jeppesen et al., 1991; Welch and Cooke, 1995). 2.Evaluating Management Options Internal o Aeration/Alum o Dredging External o Storm water Management/BMP’s 3.Science, Acceptability, and Cost Developing a Management Plan

Affordability- Poor, >$Millions Technical Effectiveness- Fair, ?? $$ Acceptability- Poor, current issues? Science, Acceptability and Cost Stormwater Management and BMP’s Rain Water/Waterfowl? Current Issues? Evaluating Management Options: External Loading

Less expensive but don’t last as long Offers more immediate relief Technique Cost per/acre Longevity (yrs.) Acceptability Aeration $ N/AGood Alum $ to 20Good Dredging $50, , to >200Fair-Poor Science, Acceptability and Cost Evaluating Management Options: Internal Loading

P P P P P P P P P P P P P P P Lake Sediment Lake Water P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P Internal Cycling of Phosphorus P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P P >100 times more P in sediments than in water 10cm P P P Al Alum is used to improve water clarity and reduce Phosphorous.

Methods: Dosing Alum Jar test results Find point where P reduction is greatest (50-70ppm) Maintain a pH >6.5

Aeration is used for improving multiple aspects of a lake Physical Stratification Odor Turbidity Water depth (muck) Chemical Dissolved Oxygen Nitrogen Phosphorous pH Biological Algae Zooplankton Fisheries

1) Degree of Impairment: 250 mg/m^3/day of oxygen 2,000 to 4,000 mg/m^3/day (Jones and Taggart, 2001). Vs Eutrophic Oligotrophic Methods: Sizing Aeration 2) Aerations Benefits and Lake Goals: –W–W ater quality –P–P hytoplankton –F–F isheries –S–S ediment quality –B–B enthic fauna -EPA, 1977 Sizing to the highest denominator

Methods: Sizing Aeration Monzur & Takashi, 2000 Same Air Flow: 25.4 CFM Different # of Air Station

Restoration Timeline: August 2011 First Aeration Install January 2012 ASI/Vertex Contracted Lake Study Began April 2012 Beginning of Restoration: Redesigned Aeration August 2012 First Alum Treatment September 2012 Second Alum Treatment 2015 Monitoring 2014 Monitoring 2013 Monitoring

Results: Vertex Aeration Design: Turnovers: 2.14 per/day Existing Aeration Original Aeration Design: Turnovers:.60 per/day August 2011 January 2012 Institutional Acceptability?

Undersized 1 Month After New Design 9 Months Results: Dissolved Oxygen

Aeration alone is often times not enough to reduce P. Need to add more binding sites.

Aeration Works well on Nitrogen Alum does not Toxic Levels of Ammonia were Causing Fish kills

Takes time for Aeration to acclimate and work.

New Aeration Design is Meeting O2 Demands

In 11 months the lake was restored back to it’s reference condition

Where is the lake at now (2012-Present)? Dissolved Oxygen has been maintained Nutrients are still at acceptable levels Minor green algae blooms (no fish kills)

Thank You! Questions?