Grantee Research Project Results

Final Report: HAB early mitigation by magnetic photocatalysts

EPA Grant Number: SV840420
Title: HAB early mitigation by magnetic photocatalysts
Investigators:
Institution:
EPA Project Officer:
Phase: II
Project Period: March 1, 2023 through April 23, 2025
Project Amount: $100,000
RFA: 17th Annual P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2022) Recipients Lists
Research Category: P3 Awards

Objective:

In the current study, we are developing a smart technology to eliminate harmful algal bloom (HAB) outbreaks at early stages through early detection and treatment. In the Phase I project, we successfully monitored and mitigated HAB outbreaks in the bench scale. For detection, unmanned aircraft system (UAS) monitoring was conducted, followed by auto-sampling, and for treatment, a lab synthesized γFe₂O₃/TiO₂ nanomaterial was employed. In the Phase II project, the main objective is to expand this success to the pilot scale. The specific objectives of this project are as follows:

1) HABs will be monitored using an integrated process of drone-based monitoring and auto-sampling for lab analysis. A statistical inversion model will be developed to predict HABs by associating drone images with water quality results (e.g., qPCR test) from samples collected by the solar-powered auto-sampling station.

2) Lab tests will be conducted to understand the impacts of influential factors on HAB mitigation, such as natural organic matter, bicarbonate & carbonate, pH, and temperature of lake water, for optimizing the efficiency of the technology.

3) A point-of-use (POU) system will be designed and manufactured, which comprises an innovative and integrative automated floating station (AFS) followed by a treatment floating station (TFS), for pilot scale studies. Key parameters such as volume, flow path, hydraulic retention time, and nanomaterial lifespan will be considered.

4) Larger-scale synthesis and further characterization of the γFe₂O₃/TiO₂ nanomaterials will be conducted for application in the POU system to treat HABs.

5) Early-stage HAB mitigation will be investigated in a HAB impacted lake in Southern Illinois at the pilot scale using the designed POU system under solar irradiation.

Summary/Accomplishments (Outputs/Outcomes):

1. Statistical Inversion Model for Algal Monitoring

A UAV-based multispectral imaging system was successfully developed and validated for predicting chlorophyll-a (Chl-a) concentrations in two Southern Illinois water bodies. Regression models demonstrated that the Normalized Difference Vegetation Index (NDVI) best predicted algal biomass in Carbondale Reservoir, while the blue-to-green ratio (B/G) served as the most reliable predictor in Campus Lake. These models establish a cost-effective and scalable approach for remote monitoring of algal blooms.

1. Phosphorus Removal Using Nanocomposites

Batch experiments with γFe₂O₃/TiO₂ nanocomposites showed effective phosphorus adsorption in both deionized and lake waters, achieving removal efficiencies up to 73% under optimized conditions (75 °F, pH 7.5). Adsorption performance was adversely affected by high concentrations of natural organic matter and bicarbonate, which competed for sorption sites. Importantly, desorption studies confirmed that the material could be regenerated and reused, supporting its long-term feasibility for algal bloom mitigation.

1. Inactivation of Cyanobacteria

Photocatalytic inactivation studies using γFe₂O₃/TiO₂ under visible light achieved up to 95% reduction of Microcystis aeruginosa and ~90% reduction of Cylindrospermopsis raciborskii in pure cultures. Lake water experiments also confirmed cyanobacterial inactivation (≥85% reduction in key gene markers). Environmental factors such as humic acid, temperature, and pH influenced treatment efficiency, highlighting the importance of local conditions in field deployment.

1. Point-of-Use (POU) System Design and Manufacturing

A solar-powered, remotely accessible floating station (AFS/TFS) was successfully designed and constructed. The system integrates a photoreactor with UV-transmissive tubes, automated pumps for water loading and sampling, and an innovative magnetic nanoparticle recovery strategy. The platform is controlled by a Raspberry Pi with LTE connectivity, enabling real-time remote operation and monitoring of water treatment processes. Additionally, a programmed mechanical arm collects lake water samples for auto-sampling.

1. Nanomaterial Synthesis and Optimization

The γFe₂O₃/TiO₂ nanocomposite was synthesized and extensively characterized, confirming its nanoscale size (15–100 nm), high surface area (116 m²/g), and photocatalytic activity under visible light. Due to limitations in magnetic separation, a modified Fe₃O₄@SiO₂@γFe₂O₃/TiO₂@rGO nanohybrid was developed. This improved material demonstrated faster magnetic recovery (20 min vs. >1 hr) while maintaining comparable phosphorus removal and cyanobacteria inactivation performance.

1. Pilot-Scale Testing

Pilot-scale implementation could not be conducted due to funding termination and the lack of active HAB events in regional lakes after the POU system was established but before the project period ended. Nevertheless, preliminary identification of phosphorus-rich lakes highlights potential future sites for field application.

Conclusions:

In this Phase II project, we developed an integrated and cost-effective strategy for early detection and mitigation of HABs. A drone-based monitoring technique with inversion models was successfully established for real-time assessment in both studied lakes. In parallel, reusable Fe₃O₄SiO₂γ-Fe₂O₃/TiO₂ core double-shell nanohybrids were synthesized, characterized, and demonstrated to effectively mitigate HABs under solar irradiation. A pilot-scale POU system, consisting of solar-powered floating station with auto-sampling capability, was fabricated for HAB mitigation. Together, these innovations address the critical need for early-stage HAB intervention and treatment, representing a significant advancement toward the P3 program’s goal of ensuring clean and safe water. This research provides a sustainable and practical solution to protect water quality and public health.

References:

Publications 

• Khan N., P.P. Bhowmik, M.S. Sarker, H.R. Yang, R.P. Li, J. Liu (2025). Impact of water quality parameters on harmful algal bloom mitigation and phosphorus removal by lab-synthesized γFe₂O₃/TiO₂ magnetic photocatalysts. Algal Research - Biomass Biofuels and Bioproducts. 86, March 2025, 103932. 
• Wu D., R.P. Li, J. Liu, N. Khan (2023). Monitoring algae blooms in small lakes using drones: a case study in Southern Illinois. Journal of Contemporary Water Research & Education. 177, March 2023.
• Madany P., C.J. Xia, L. Bhattacharjee, N. Khan, R.P. Li, J. Liu (2021). Antibacterial activity of γFe₂O₃/TiO₂ nanoparticles on toxic cyanobacteria from a lake in Southern Illinois. Water Environment Research. 93(11): 2807–2818.

Presentations

• Liu J., C.J. Xia, L. Bhattacharjee, P.C. Williams, P. Madany, N. Khan, H.R. Yang, M. Campobasso (2024). Environmental applications and impacts of transition metal-based nanomaterials. 24th International Conference on Environmental Indicators, June 10, SIUE, Edwardsville IL.Liu J. (2022). Harmful algal bloom mitigation by magnetic photocatalysts under visible light. North Central Region Water Network. Algal Bloom Action Team Webinar. June 01. 
• Khan N., E.N. O'Brien, S. Baral, J. Liu (2022). Efficient HAB mitigation by magnetic visible-light driven photocatalysts. 2nd Annual Virtual Harmful Algal Bloom Symposium. January 06.
• Khan N., P. Madany, C.J. Xia, S. Baral, I.M. Senanayake, D. Wu, S. Sarkar, L. Bhattacharjee, J. Liu, R. Li, K. Chen, B.M. Goodson (2021). Harmful algal bloom (HAB) early mitigation by magnetic photocatalysts. EPA P3 National Student Design Expo. June 21-25. 
• Khan N., E.N. O'Brien, S. Baral, J. Liu (2021). Efficient harmful algal bloom (HAB) mitigation by magnetic visible-light-driven photocatalysts. Annual Mid-American Environmental Engineering Conference. Three Minute Thesis Presentations. St. Louis, MO. September 25.  

Journal Articles:

No journal articles submitted with this report: View all 6 publications for this project

Supplemental Keywords:

Blue-green algae, excessive algae growth, nanoparticle

Relevant Websites:

SIU News Article Exit

Progress and Final Reports:

Original Abstract

2023 Progress Report

2024 Progress Report

P3 Phase I:

HAB Early Mitigation by Magnetic Photocatalysts  | Final Report