Lake Eola, in downtown Orlando, was the subject of extensive research to determine the impact of stormwater runoff to the lake and possible management alternatives. The focus of this research was stormwater treatment by chemical coagulation followed by detention. Phosphorus was the main parameter targeted for removal. Various chemical parameters were also evaluated included: TSS, VSS, NVSS, COD, TKN, NH3, TOC, TP, Ca, As, Cd, Cu, Cr, Ni, Mg, Zn, Fe, and Pb. The chemical coagulants used for this research included: alum, ferric chloride, and lime. The study involved settling column tests for the various treatment methods to determine stormwater settling characteristics and pollutant removal rates by depth and time. Detention of the runoff in the column for 120 minutes resulted in average removal rates of 55% for TSS and 30% for TP. Both alum and ferric chloride coagulation followed by 60 minutes of settling resulted in average removal rates of over 90% for both TSS and TP. Lime coagulation followed by 60 minutes of settling resulted in over 50% removal for both TSS and TP. Regression analysis was used to develop equation relating pollutant removal with time and settling velocity. Isoconcentration lines were also developed to predict pollutant removal rates for specific parameters.

The settling characteristics of urban stormwater runoff emanating from the Lake Eola Watershed (Orlando, Florida) were evaluated through a series of 7 column studies. The percentage removal that occurred due to sedimentation was observed for various stormwater pollutants and constituents. These included the General Water Quality Parameters: Total Suspended Solids, Non-volatile Suspended Solids, Volatile Suspended Solids, Chemical Oxygen Demand, Total Kjeldahl Nitrogen, Ammonia Nitrogen, Total Organic Carbon, and Total Phosphorus. The metals parameters: Zinc, Cadmium, Arsenic, Nickel, Copper, Magnesium, Iron, Lead, Chromium and Calcium were also considered. The results of the settling analysis indicates that the quality of Lake Eola stormater can be improved by plain sedimentation of detention as convincing removals were displayed by the solid parameters displayed trends of weak removal. Regression equations were developed that describe percent removal as a linear and logarithmic function of time and settling velocity. Isoconcentration lines were also developed for total suspended solids and total phosphorus removals. In addition, the effect of this treatment on the productivity of Lake Eola was assessed in terms of existing trophic state models.

Lake Eola is a land-locked lake located in downtown Orlando, Florida. Its surface area is approximately 27.0 acres (11.0 Ha) and water depth is 2 to 3 feet (0.6 to 0.9 meters) near the shore and 22 feet (6.7 meters) toward the center. Periodical water samples were collected from the lake and storm drains for various stormwater events and physiochemical parameters were analyzed to calculated loading rates from nutrients and heavy metals released to Lake Eola. Algal bioassay studies were performed to investigate stormwater impacts on productivity. Periodical water samples were collected from the lake mixed and filtered for limiting nutrient studies using various concentrations of N, P, and Fe. Unialgal species of Selenastrum, Chlorella and indigenous species were used and changes in chlorophyll "a" and biomass were measured. Results indicate that phosphorus or nitrogen can be limiting at some times of the year. However, the ratio of P:N can be ore important than actual concentration of phosphorus and nitrogen separately. Similar algal bioassays were performed on a mixture of stormwater, coagulated stormwater and lake water at different ratios.