Grantee Research Project Results

2023 Progress Report: HAB early mitigation by magnetic photocatalysts

EPA Grant Number: SV840420
Title: HAB early mitigation by magnetic photocatalysts
Investigators: Liu, Jia , Goodson, Boyd , Li, Ruopu , Senanayake, Ishani M , Khan, Nafeesa , Regmi, Sushmita , Wu, Di , Yang, Ning , Yang, Haoran , Kalinzi, Joseph , Wang, Minxiao
Current Investigators: Liu, Jia , Goodson, Boyd , Li, Ruopu , Senanayake, Ishani M , Yang, Ning , Yang, Haoran , Kalinzi, Joseph , Wang, Minxiao , Sabuj, Sonkorson Talukder , Sarker, Md Sayeduzzaman , Bhowmik, Partha Protim , Wang, Yuhua , Edidem, Michael , Kankanamge, Malithi Wanniarachchi , Forcade-Perkins, Nicolas
Institution: Southern Illinois University - Carbondale
EPA Project Officer: Page, Angela
Phase: II
Project Period: March 1, 2023 through April 23, 2025
Project Period Covered by this Report: March 1, 2023 through February 29,2024
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:

Harmful algal blooms (HABs) are increasingly a global concern and a major environmental problem in all 50 states in the U.S. It adversely affects water quality in freshwaters and coastal waters and poses negative health and economic impacts. HABs are often associated with high concentrations of cyanobacteria, which can produce cyanotoxins that are harmful to humans, pets, fish, birds, and other wildlife. In particular, HABs seriously affect the resilience of our communities by using surface water resources for recreational and drinking water purposes. Thus, mitigation strategies to combat HABs are critically important. However, current mitigation methods either add solid materials into sediments, potentially bring other contaminants into lakes, or can only treat harmful algae (e.g., cyanobacteria) but not the toxins produced by these algae. Moreover, the removal of nutrients (e.g., phosphorus, a possible reason for HABs) is largely omitted. Here, we create a smart strategy to mitigate HABs in their early stages by not only reducing the number of cyanobacteria, but also degrading the cyanotoxins, and removing the nutrient phosphorus. In addition, HABs in their early stages are detected and monitored by two different pathways: molecular detection following auto-sampling, and unmanned aircraft systems (UAS), to control HABs before their outbreaks. The research focuses on the Campus Lake at Southern Illinois University Carbondale (SIUC) and Carbondale Reservoir, which have been used for recreational purposes but have experienced HAB outbreaks. Lab-made γFe2O3/TiO2 nanomaterials are used under solar light to mitigate HABs. Owing to its magnetic property, this material can be easily recycled, thus minimizing the solids introduced to the sediments. Based on the success of HAB monitoring and mitigation by γFe2O3/TiO2 nanomaterials in bench scale in the Phase I project, the overall objective of the Phase II project is to expand early-stage HAB mitigation to a pilot scale. The specific objectives are as follows: 

1) HABs will be monitored using an integrated process of drone monitoring and auto-sampling for lab analysis. Statistical Inversion Model will be developed to predict HABs by associating drone images with water quality lab results (e.g., qPCR test) of 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), both powered by solar light with considerations of the lake area, the volume and flow paths in the reactor, the hydraulic retention time, and the lifespan of the nanomaterials. 

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

5) HAB early mitigation will be investigated in the Campus Lake of SIUC (or a HAB affected lake) in a pilot scale using the designed POU system under solar light. The intelligent floating station will be designed to move to the sites impacted by harmful algae. 

Progress Summary:

1) Statistical inversion model
     Carbondale Reservoir and the Campus Lake, both located near or at SIUC, were selected for developing the lake monitoring procedure based on unmanned aerial vehicle (UAV) and lab testing. Our datasets include (1) 5-band UAV images collected from May to October 2021 (Bands: Red, Green, Blue, Near Infrared, Red Edge), and (2) water samples for testing chlorophyll-a (Chl-a, µg/L) that were collected at the same time with the UAV images collection. Two sampling points from each water body were selected. Pix4Dmapper image processing software was used to automatically conduct image stitching, radiometric calibration, and orthoimage generation. ArcGIS georeferencing tool was used to assign the ground truth coordinates to matched pixels on stitched UAV images. Seven indices were used to estimate the relationships between Chl-a and spectral indices. By analyzing vegetation indices derived from multispectral UAV images and Chl-a concentrations in the two lakes, statistical regression models were established for each waterbody. The model relates the spectral characteristics of the lake water to its algae biomass. Based on the best-fit model, the Chl-a concentration can be predicted from the UAV-based spectral indices. It was found that normalized difference vegetation index (NDVI) and blue-to-green band ratio (B/G) are the best-fit indices to the variation in Chl-a in Carbondale Reservoir and SIUC Campus Lake, respectively. It was found that NDVI, BNDVI, GNDVI, and RVI exhibit significant positive relationships with the concentrations of Chl-a in Carbondale Reservoir. NDVI was used to establish the best-fit model based on the coefficient of determination (R2 = 0.4881). For the Campus Lake, most spectral indices exhibit no statistically significant relationship except for NDRE (R2= 0.4674) and B/G (R2= 0.3915), which present significant inverse relationships with Chl-a, and B/G is used as the best-fit index to the variation in Chl-a in the Campus Lake. 

2) Impacts of environmental factors on HAB mitigation
a) Phosphorus removal
     Phosphorus adsorption in lake water and in simulated water were performed individually with γFe2O3/TiO2 nanocomposite as adsorbent using an automated shaker stirred at 180 rpm (orbit 1.91 cm). In other sets of batch experiments, humic acid (HA), NaHCO3 and NaCl were spiked to water samples to investigate the impacts of the stated parameters on the efficiency of the nanocomposite in phosphorus removal. Furthermore, impacts of different temperatures (i.e., 65, 75, and 85 ºF) and pHs (i.e., pH of 5.5, 6.5, and 7.5) were also investigated.   
     For deionized water, rapid phosphorus uptake on γFe2O3/TiO2 within several minutes contact time reached ~21% was followed by a relatively slower rate in adsorption time of 1 h and 3 h. Maximally 1.39 mg/g phosphorus was adsorbed on γFe2O3/TiO2 after 3 h, reaching ~35% removal. Phosphorus adsorption percentage increased from ~12% to 23% in 1 h of interaction for the lake water. When contact time was extended to 3 h, about similar adsorption percentage of 24% was achieved (indicating approaching equilibrium condition), reaching maximum phosphorus adsorption at 5.7 mg/g. When NOM increased from 22.9 mg/L to 75 mg/L, phosphorus removal efficiency in lake water decreased from 9% to 5%. Phosphorus adsorption was not affected by adding 2.5 mM of chloride ions, even though its concentration was almost three times higher than the phosphorus concentration in molar basis. The addition of 2.5 mM bicarbonate significantly affected phosphorus adsorption by γFe2O3/TiO2 nanocomposite, this result indicated that HCO3- actively competed for the sorption sites of γFe2O3/TiO2 nanocomposite. Rapid phosphorus uptake in deionized water on γFe2O3/TiO2 within several minutes contact time was achieved at each of the three temperatures (i.e., 65, 75, and 85 ºF) with ~ 48% of highest adsorption at 75 ºF. This was followed by a relatively slower rate in adsorption time of 1 h and 3 h with a highest final adsorption value ~73%. Maximally 2.05 mg/g phosphorus was adsorbed on γFe2O3/TiO2 after 3 h at 75 ºF, reaching ~73% removal. Rapid phosphorus uptake on γFe2O3/TiO2 within several minutes contact time was seen for pH 6.5 and 7.5 with ~23% of the highest adsorption at pH 6.5. For pH 5.5, initial adsorption was only ~7%. Then, a relatively slower adsorption rate was seen for pH 6.5 and 7.5 at the time of 1 h and 3 h with the highest final adsorption value of ~46% at pH 7.5. For pH 5.5, the later adsorption rate was ~45% after 3 h. Maximally 1.91 mg/g phosphorus was adsorbed on γFe2O3/TiO2 after 3 h at pH 7.5.  Around 64±1% of the adsorbed phosphorus (~0.22 mg/L of adsorbed phosphorus) was desorbed by 5 mM sodium bicarbonate after 4 h contact time. This indicates that the lab synthesized nanocomposite can be regenerated and reused for mitigation of algal bloom, making the nanomaterial economically feasible as well.  

b) Inactivation of Cyanobacteria
     In this study, Microcystis aeruginosa and Cylindrospermopsin raciborskii were selected as the target cyanobacteria. The inactivation of M. aeruginosa, C. raciborskii pure culture, and cyanobacteria in the collected lake water were performed individually with γFe2O3/TiO2 nanocomposite as photocatalysts using an automated shaker stirred at 180 rpm (orbit 1.91 cm). PowerVEG FS+UV light bulbs (EYE hortilux) were used for irradiation (light intensity 0.5 mW/cm2). The inactivation study was performed in the same experimental setup under different environmental parameters as stated before. After interaction, lake water samples were filtered, and DNA of the samples were extracted. The inactivation efficiency was presented as the percent reduction of gene copies (mcyE for Microcystis, rpoC for Cylindrospermopsis, and sxtA for saxitoxin producing cyanobacteria) in samples. Gene copies of the extracted DNA were calculated from threshold cycle (Cq) values obtained from qPCR. For pure culture, the cell counts were carried out by the hemacytometer and traditional OD600.   
     Inactivation of M. aeruginosa and C. raciborskii pure culture by γFe2O3/TiO2 photocatalysts under light with 100 mg/L of the nanoparticles showed efficient inactivation of M. aeruginosa by 95% when irradiated for 1 h under visible light. The inhibition percentage of C. raciborskii was found to be ~90%. The inactivation results from lake water samples indicated inactivation of 86% 16S rRNA, 88% mcyE, and 89% sxtA containing cyanobacteria. rpoC containing C. raciborskii was not detected in lake water samples. Addition of HA (final conc. at 75 mg/L of DOC) slightly inhibited inactivation of mcyE containing cyanobacteria by 23.0±21.8% and 16S rRNA (all cyanobacteria species) by 19.0±0.8%. OD600 values were implemented to assess the reduction in cell count of the two cyanobacterial species at three different temperatures of 65, 75, and 85 ºF. The highest reduction in cell count of C. raciborskii was about 36.0% at 85 ºF, and for M. aeruginosa, the highest reduction of ~34.5% was obtained at 65 ºF. It should be noted that OD600 does not differentiate between viable bacteria and dead bacteria. The highest reduction in cell count of C. raciborskii was achieved at pH 5.5. For M. aeruginosa, the highest reduction was obtained at pH 7.5.  

3) POU system
AFS is designed to be remotely accessible through a private Long-Term Evolution (LTE) network. During the past year, we have successfully built an LTE network utilizing the 3.65 GHz Citizens Broadband Radio Service (CBRS) spectrum. Two private LTE stations have been installed on two campus locations. These base stations could enable the private LTE network coverage over the campus lake, help provide wireless signals to control the floating station and support the ongoing campus lake water quality monitoring process. The control system for the water treatment unit is installed in AFS. The solar panel has been installed. The Raspberry Pi 4 with 8GB RAM is the device that controls the system to keep the water treatment unit floating. The Raspberry Pi along with motors is utilized to facilitate the floating station. A mechanical arm is programmed to hold water bottles, which aims at taking water from the lake for auto-sampling. This mechanical arm will be connected to the floating station this summer. 
     For TFS, the modified designed volume of the treatment unit is ~30 L and the dimension of the whole treatment unit is ~6 ft × 3.5 ft. In a single row, eight connected borosilicate glass tubes will be placed, each having a dimension of 2 inches in diameter and 5 feet in length. After the pipe installation through the vent loop, the assembly will be initiated and terminated with valves for an enclosed system. The operating period of the treatment unit will be 12 hours per day and with a 1.0 h hydraulic retention time, and the treatment capacity is ~360 L water/day accordingly. Two magnetic bars will be attached to the treatment unit for the collection of the nanomaterials before the discharge of treated water.  
4) Synthesis and characterization of γFe2O3/TiO2 nanomaterial
     An amount of ~2.7 g of nanomaterial was produced in a single batch. Different batches of the nanomaterials have been successfully synthesized. The morphology and size of synthesized nanocomposite were determined by scanning electron microscope and transmission electron microscope. It was observed that the shape of the nanocomposite was spherical, and the size of an individual particle was about 15-100 nm. Energy-dispersive X-ray spectroscopy (EDX) detection showed the weight ratio of Fe to Ti is 2.2:1. The phase identification and crystal structure of the synthesized nanomaterial was investigated by X-ray diffraction (XRD). The XRD pattern consists of well-resolved peaks indicating the presence of γFe2O3 as hematite and TiO2 as anatase and rutile. The percent size distribution of the nanomaterial was determined by dynamic light scattering (DLS), and ~10.0% of the particles were less than 100 nm (with a mean of ~51 nm) attributed to the aggregation of the particles mainly due to their magnetic properties. Moreover, the magnetic properties of the freshly prepared nanomaterial were determined by Vibrating Sample Magnetometer (VSM). The nanomaterials showed the behavior of a soft ferromagnet with no measurable coercive field. Brunauer-Emmett-Teller (BET) specific surface area analysis was carried out and from the N2 adsorption-desorption isotherms the specific surface area of the synthesized nanomaterial is found to be 116.521 m2/g. Additionally, the surface composition of the nanomaterial was determined by X-ray photoelectron spectroscopy (XPS). The survey spectra confirm the presence of TiO2 and Fe2O3 in the synthesized nanomaterial. The percentage of the mass concentration in the nanomaterial for Fe, Ti, and O is 35.1%, 31.0%, and 33.9%, respectively. Band gap energy was determined from Tauc plot to be 2.6 eV, indicating responsive under visible light. Lastly, the zeta potential of the nanomaterial suspension at 100 mg/L concentration at different pHs was determined using a Zetasizer. Results indicate that the point of zero charge of the particles was at a pH of 5.9.  

 

 

Future Activities:

 In conclusion, this Phase II study presents a novel approach to mitigate HABs using γFe2O3/TiO2 nanomaterials under solar light on a pilot-scale. The study addresses the critical need for early-stage intervention and treatment of HABs, and the developed inversion models can be applied for monitoring HABs using a drone in both of the studied lakes. Through dedicated synthesis, characterization, and lab testing of γFe2O3/TiO2 nanomaterials, the efficacy of the proposed strategy is demonstrated. The innovative use of drone technology, auto-sampling, and solar-powered floating stations enhances monitoring and treatment capabilities. Overall, this research represents a significant advancement in HAB mitigation, offering a sustainable and effective solution to safeguard water quality and public health. 

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views

Other project views:	All 6 publications	2 publications in selected types	All 2 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Wu D, Li R, Liu J, Khan N. Monitoring algal blooms in small lakes using drones:a case study in Southern Illinois. Journal of Contemporary Water Research & Education. 2023;177(1):83-93.	SV840420 (2023)	Full-text: Wiley Full Text-HTML Exit

Supplemental Keywords:

Blue-green algae, excessive algae growth, nanoparticle 

Relevant Websites:

SIU Exit , Jia Liu Exit

Progress and Final Reports:

Original Abstract

2024 Progress Report

P3 Phase I:

HAB Early Mitigation by Magnetic Photocatalysts  | Final Report