Updated on 4-24-2024

Lake Jesup is a hydrologically complex system with a large, urbanized watershed and is the largest lake in Seminole County. The lake is shallow with a relatively low flushing rate that drains a 150-square-mile watershed, including portions of Oviedo, Sanford, Winter Park, Casselberry, Maitland, Longwood, Altamonte Springs, Lake Mary, Eatonville, Winter Springs and Orlando in Seminole and Orange counties.

Local stakeholder interest in restoring the lake began in 1993 with the Friends of Lake Jesup. In 2002, the District’s Governing Board designated Lake Jesup as a priority basin for restoration of water quality and fish and wildlife habitats. In 2008, in conjunction with the Lake Jesup Interagency Management Strategy, the Florida Department of Environmental Protection adopted a total maximum daily load for total phosphorus followed by the Lake Jesup Basin Management Action Plan (BMAP). As a result, progress is being made to reduce nutrient sources and concentrations to improve the lake’s water quality and clarity.

Lake Jesup intact cellular algae harvesting with simultaneous nutrient export

• This pilot project, conducted by AECOM, deployed a mobile algal harvesting unit that removed nitrogen and phosphorus through direct removal of the entire algae cell (known as intact cellular algae) and suspended solids located within the upper 12-inches of the water column in Lake Jesup. An innovative air flotation technology was utilized to attach microscopic air bubbles to the algae and sediment floc, creating buoyancy, to allow efficient separation of algal biomass and clarified water. Clarified water was returned to the lake while algal biomass were managed at Seminole County’s Yankee Lake Wastewater Treatment Plant. The harvesting unit was mounted on a barge and transported around Lake Jesup so that algae could be harvested at various locations.
• The pilot project received $1.7 million, in 2020, through a Florida Department of Environmental Protection Harmful Algal Bloom Innovate Technology Project Grant solicitation requesting proposals from government entities to prevent, detect, cleanup, or otherwise address harmful algal blooms in Florida’s waterways. This was a direct result of the 2019 Blue-Green Algae Task Force, formed by Gov. Ron DeSantis.
• AECOM periodically operated the algae harvesting system over a nine-month period and completed system operations in May 2022. System decommissioning and removal from Lake Jesup was completed in November 2022. The objective of this pilot project was to collect representative data to evaluate system efficiency and the cost effectiveness of a full-scale system that can help achieve the Lake Jesup Total Maximum Daily Load and Basin Management Action Plan goals.
• See final report here.

Lake Jesup Nutrient Reduction Project

Reducing the total nitrogen (TN) and total phosphorus (TP) concentrations in the water column is an important step for improving water quality in Lake Jesup. An analysis by CDM Smith in 2021 on behalf of the District determined that small footprint technologies, including media-based nutrient removal, could remove TN and TP from the water column at higher rates than a flow-through wetland system for a similar capital investment.

The goal of the Lake Jesup Nutrient Reduction project is to design, construct, and operate a nutrient removal system, using biosorption activated media-based technology, that cost-effectively removes TN and TP from Lake Jesup. The project will pump raw water from the lake, treat influent using media-based technology, and discharge water treated to state water quality criteria back to the lake. The full-scale treatment technology will be designed to remove TN and TP at rates at or above 50,000 and 5,000 pounds/year, respectively. The project location is a 9.7-acre upland property on the larger District-owned Lake Jesup east tract (see figure).

Design of the full-scale nutrient removal system began in January 2024. Part of the design work will be a pilot-scale study to evaluate the best media-based technology.

Project costs

• Total construction: $20–25 million (est. at 60% design level)
• Engineering: $1.1 million
• Operation and maintenance: $250,000–$400,000/year

Benefits

• Estimated total phosphorus reduction: 2,800 lbs./yr.
• Estimated total nitrogen reduction: 23,800 lbs./yr.
• Estimated increase in area suitable for submerged aquatic vegetation: 200–500 acres

Project schedule

• FY 2019–2020: Initiate design and permitting
• FY 2020–2022: Ongoing design and permitting
• FY 2022–2023:  Complete design and permitting
• FY 2023–2024: Bidding and begin construction (contingent on funding)

Lake Jesup sediment phosphorus flux treatment evaluation project

The Florida Department of Environmental Protection and the District are collaborating on an evaluation of chemical treatment technologies to reduce the flux of phosphorus from Lake Jesup’s sediments into the water column. The goal is to reduce the phosphorus concentration in the lake’s water to reduce algal bloom intensity, duration and frequency. The study will evaluate treatment efficiencies, phosphorus removal rates, cost efficiencies and determine which treatment technologies may reduce phosphorus flux rates in Lake Jesup to the greatest extent.

Phase 1 examined three treatment technologies in a laboratory bench-scale study identified in the Request for Information by the District in 2017 (updated in 2020). Each technology was designed to reduce net phosphorus flux from the sediments to the water column. The results of the study concluded that ViroPhos outperformed the other technologies and provided the most consistent level of phosphorus flux reduction. ViroPhos was also found to be the most cost-effective at reducing total phosphorus concentration.

Phase II is now underway to evaluate the effectiveness of the treatment technology in outdoor mesocosms to assess potential limitations in more realistic and complex conditions. The District solicited for the Phase II work, scoring and ranking companies based on project qualifications and evaluation criteria. The Governing Board awarded the contact in November 2022 to WSP (formally Wood Environmental).

WSP completed a series of sediment sampling in Lake Jesup in spring 2022 and eight mesocosms were deployed from May to December 2023 near the outlet of Howell Creek. Six of those mesocosms were treated with one of three test amendments to observe their ability to sequester phosphorus in the underlying sediment. WSP collected both zoo and phytoplankton samples as well as bi-weekly water quality samples within and outside of the mesocosms. Additionally, 32 sediment cores were collected to evaluate phosphorus flux from the sediment to the water column. Results will provide a better understanding of rates for phosphorus flux, which will help estimate the annual nutrient load from internal cycling. A final report for this study is expected at the end of September 2024.