The Osprey Marsh Algal Turf Scrubber® (ATS) facility is a full-scale surface-water treatment system located in Indian River County, Florida. The facility uses ATS technology to support nutrient management, water quality improvement, and long-term operational evaluation under Florida field conditions.
Osprey Marsh ATS floway viewed from the downstream end of the treatment system. The broad, shallow floway surface supports attached algal growth used for nutrient polishing and biomass recovery.
Facility Summary
Facility: Osprey Marsh ATS
Location: Indian River County, Florida
Technology: Algal Turf Scrubber®
Scale: 10 MGD
Status: Operating
Initial Operation: 2015
Source Water: South Relief Canal surface water blended with South County Water Treatment Plant RO concentrate
Operating Context: Low-nutrient surface-water polishing with RO concentrate blending
Application: Nutrient reduction / surface-water restoration / RO concentrate management
Owner: Indian River County
HydroMentia Role: Technology provider, design support, and operational reference
Operating Context
Osprey Marsh ATS treats a blended flow consisting primarily of South Relief Canal surface water, with a smaller contribution of reverse osmosis concentrate from Indian River County’s South County Water Treatment Plant. This operating context distinguishes Osprey Marsh from many conventional nutrient treatment projects because the system is not treating high-strength wastewater. Instead, it is polishing relatively low-nutrient surface water while also providing a management pathway for RO concentrate.
Indian River County’s 2016 Annual Performance Review reported average 2016 flows of approximately 7.24 MGD from the South Relief Canal and 0.76 MGD of demineralization concentrate, producing an average blend ratio of approximately 9.5:1. The blended flow was introduced at the Osprey Marsh headworks and distributed across the ATS floways for treatment.
This low-concentration operating environment is important because nutrient removal becomes increasingly challenging as influent concentrations approach background conditions. Osprey Marsh therefore provides a useful full-scale reference for evaluating ATS performance in applications where the objective is not simply bulk nutrient removal, but sustained polishing toward low receiving-water nutrient concentrations.
Operational Significance
Osprey Marsh ATS is significant because it demonstrates long-term, utility-scale operation of Algal Turf Scrubber® technology under low-nutrient surface-water conditions while receiving a blended contribution of RO concentrate. This combination makes the facility especially relevant to future nutrient-polishing applications where nitrogen reduction to low effluent concentrations may be the limiting compliance challenge.
Long-term monitoring data summarized for the January 2022 through April 2025 period reported mean outflow concentrations of approximately 0.775 mg/L total nitrogen and 0.079 mg/L total phosphorus. Many total phosphorus measurements during this period were undetected at the analytical detection limit of 0.070 mg/L, suggesting that the true mean TP outflow concentration may be lower.
This performance is particularly relevant for applications where cost-effective nitrogen polishing from low influent concentrations is required. While conventional treatment methods can often achieve low phosphorus concentrations, sustained nitrogen reduction at low influent concentrations can be more difficult. Osprey Marsh therefore provides a full-scale operating reference for ATS as nutrient-polishing infrastructure for stringent nitrogen reduction applications.
Photographs
Osprey Marsh ATS floway on July 22, 2025. The right side shows approximately 4 days of algal turf regrowth after harvest, while the left side shows approximately 20 days of regrowth, illustrating the staged harvest cycle used to maintain active biomass production.
View Osprey Marsh ATS photo gallery
Additional facility photographs are available in HydroMentia’s Facebook photo archive. Facebook may require visitors to sign in to view the complete gallery.
Reports and Publications
Indian River County’s 2016 Osprey Marsh Annual Performance Review Report summarizes 2016 monitoring, operations, permit compliance, nutrient removal performance, flow data, water quality monitoring, and harvesting for the Osprey Marsh ATS Wetland Treatment System.
Additional reports and publications related to Algal Turf Scrubber technology and facility-scale applications are available in HydroMentia’s ATS Library.
Related Facilities
Related HydroMentia ATS facilities and demonstrations include Egret Marsh ATS, S-154 ATS, and other full-scale and pilot-scale systems.