Grantee Research Project Results
Final Report: Novel Mineral-Hydrogel Composites for Effective Nutrient Removal to Manage Harmful Algal Blooms
EPA Grant Number: R840084Title: Novel Mineral-Hydrogel Composites for Effective Nutrient Removal to Manage Harmful Algal Blooms
Investigators: Jun, Young-Shin , Tang, Yinjie
Institution: Washington University in St. Louis
EPA Project Officer: Ludwig-Monty, Sarah
Project Period: September 1, 2020 through August 31, 2023 (Extended to August 31, 2024)
Project Amount: $800,486
RFA: Approaches to Reduce Nutrient Loadings for Harmful Algal Blooms Management (2020) RFA Text | Recipients Lists
Research Category: Harmful Algal Blooms , Water
Objective:
Harmful algal blooms (HABs), which can produce cyanobacterial toxins, degrade water quality, threaten public health, harm ecosystems, and impact the economic output of industries. One major contribution to HABs is nutrient pollution from anthropogenic activities, mainly by nitrogen (N) and phosphorus (P). To reduce nutrient pollution, we have developed novel mineral–hydrogel composites to effectively remove P and N, and we have determined their impacts on algal growth control. Calcium alginate hydrogels seeded with calcium phosphate (CaP), wollastonite (CaSiO3), or struvite (MgNH4PO4) are synthesized for effective phosphate and ammonium removal and recovery. After that, we examined the mineral–hydrogel composites’ effectiveness for HAB mitigation by both bench- and pilot-scale cyanobacteria growth experiments.
Summary/Accomplishments (Outputs/Outcomes):
First, we developed Ca-Alg/CaP composite platforms by adding CSH and constructing a microstructure of the composites. By varying the formulation used to synthesize mineral–hydrogel composites, we concluded that CaP mineral seeds synthesized using higher concentrations of calcium in the gelation bath and using more ionic P precursor perform better with regards to P removal to low P concentrations. These findings enable the newly developed composites’ application for HAB mitigation through removal of excess phosphate in surface waters, a key nutrient implicated in HAB formation. Furthermore, we successfully integrated CSH into the CaP mineral–hydrogel composites by addition of sodium silicate to the formulation. The synergistic combination of CSH and CaP inside the mineral–hydrogel composites enable the fast removal of P and expands the aqueous conditions in which the mineral–hydrogel composites can effectively recover P. This strategy also provides a way to lower the chemical requirements for synthesis, which is important for optimizing the cost of the mineral–hydrogel composites.
Based on the synergistic combination of fast-dissolving CSH and CaP mineral seeds, we created and tested mineral–hydrogel composites that combine wollastonite and CaP. We determined that wollastonite’s slower dissolution limits the homogeneous nucleation of CaP particles that may be mobile and releasable to the environment. Wollastonite’s use resulted in excellent heterogeneous P removal performance (from 6.2 mgP/L to 0.067 mg-P/L in 72 hours) inside the mineral–hydrogel composites and improved their overall Premoval capacity. The demonstrated P-removal performance of the mineral–hydrogel composites will ensure lower P concentrations to mitigate HABs. Meanwhile, the P captured inside the mineral–hydrogel composites can be reused as a slow-release P source/fertilizer for supplying photo-biorefineries.
Synthesis of millimeter-scale heterogeneous (compartmentalized) mineral–hydrogel composites with various mineral seeds in different compartments of the hydrogel (e.g., in the center and on the outside of a spherical particle) was accomplished using a 3D printed nozzle. The use of heterogeneous mineral– hydrogel composites allowed us to tailor the mineral–hydrogel composites compositions and architectures for more effective P and nitrogen (N) removal/recovery.
In addition, a conditioning treatment to increase the operating lifespan of the Ca-Alg/CaP+Wollastonite was demonstrated. The conditioning treatment was able to restore P-uptake ability after one cycle, supporting multiple cycle reuse of the mineral–hydrogel composites. Furthermore, a salt pretreatment before drying the composites improved their reswelling ability. These advances improve the scalability and applicability of the mineral–hydrogel composites.
Furthermore, we examined the simultaneous N and P removal, which is crucial for curbing harmful algal growth and balancing the N/P ratio. Our newly developed mineral–hydrogel composites incorporated struvite minerals (Ca-Alg/CaP+Struvite), enabling simultaneous removal of N and P. The new composites significantly reduced final N and P concentrations, lowering phosphate levels below 0.01 ppm (the reported concentration level that can trigger eutrophication) with a 1.0 g dose of dry hydrogel/L. We also verified the efficacy of these mineral–hydrogel composites in removing N and P in the presence of various environmentally abundant substances. Moreover, we demonstrated the reusability of these composites.
As a new design of the mineral–hydrogel composite, we developed core-shell structures by utilizing a positively charged polymer as a shell material. While a polyethyleneimine (PEI) coating on CaAlg/CaP+Wollastonite slightly improved P removal, further development should be made to offset the added coating and operational costs. A PEI coating can be used to remove other nutrients, such as nitrate, adding a dual functionality to the core-shell structure.
After developing the mineral–hydrogel composites, we examined their effects on algal systems through bench- and large-scale growth tests. The mineral–hydrogel composites are chemically stable during algal growth and removed >90% P from synthetic wastewater. Moreover, the use of mineral–hydrogel composites to pretreat the synthetic wastewater reduced algal growth rate by 75% (pure cyanobacterial culture) and by 48% (natural algal community from a local lake). In addition, the composites can be placed in algal cultures as a P source without negative growth impacts (shading effect). Furthermore, in complex wastewaters, the composites effectively reduced P. After the treatment, the growth of algal species (including fast growing Synechococcus elongatus, toxin-producing Microcystis aeruginosa, and algal natural consortia from a local pond) was reduced, showing that the mineral–hydrogel composites can restrict algal growth through nutrient removal from complex wastewater matrices. Furthermore, we found that recovered P and N from composites can be released as fertilizers, achieving sustainable nutrient recovery and reuse. Additionally, we examined the composites’ efficacy using nature algal species collected from three distinct harmful algal bloom areas in Missouri and Illinois. In bench-scale studies, treated water consistently exhibited reduced algal growth compared to the control.
Moving toward scale-up of the composite applications, we successfully operated a 20 L setup for mineral hydrogel fabrication and wastewater treatment. Compared to bench-scale operations, scaling up required a higher dose of mineral–hydrogel composites to achieve similar removal efficiencies. Algal growth in the larger-scale wastewater treatment showed the similar behaviors with that observed in bench-scale experiments. The algal growth was successfully controlled in the larger scale.
Finally, we built a multi-substrate and multi-species kinetic model to simulate algal growth and consortia interactions under N- and P-limited conditions. The model can also predict algal growth and toxin productions under different HAB treatment conditions. To predict microbial growth under different nutrient and environmental conditions, we developed a MATLAB-based platform called MAGMA (Micro-Algae Growth Modeling Application, hosted on GitHub https://github.com/xav1002/MAGMA ). This tool can be useful for uncovering HAB dynamics and toxin production. To suggest future directions for the technology, we conducted the technoeconomic analysis to figure out the economic bottleneck of the mineral–hydrogel composites generating process. Optimal process size determination and securing a reasonable but sturdy syringe filter unit and affordable cost of sodium alginate will allow the economic feasibility of our technology.
Conclusions:
Overall, mineral–hydrogel composites developed in our work could function as an effective mitigation and a remediation platform to address nutrient pollution and have a beneficial usage (upcycling) as slow-release fertilizer to sustain P management. We believe that our technology can support HAB mitigation by thorough N and P control.
Journal Articles on this Report : 8 Displayed | Download in RIS Format
| Other project views: | All 19 publications | 8 publications in selected types | All 8 journal articles |
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Jun Y, Zhu Y, Wang Y, Ghim D, Wu X, Kim D, Jung H. Classical and nonclassical nucleation and growth mechanisms for nanoparticle formation. Annual Review of Physical Chemistry 2022;73:453-477. |
R840084 (2021) R840084 (Final) |
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Lee H, Xu V, Diao J, Zhao R, Chen M, Moon T, Liu H, Parker K, Jun Y, Tang Y. The use of a benign fast-growing cyanobacterial species to control microcystin synthesis from Microcystis aeruginosa. Frontiers in Microbiology 2024;15. |
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Xu V, Lee H, Long B, Yuan J, Tang Y. MAGMA: microbial and algal growth modeling application. Journal of Allergy and Clinical Immunology 2025;85:16-22. |
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Xiao Z, Tan AX, Xu V, Jun YS, Tang YJ. Mineral-hydrogel composites for mitigating harmful algal bloom and supplying phosphorous for photo-biorefineries. Science of The Total Environment 2022;847:157533. |
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Jun YS. Catalyst:the roles of chemistry in clean water for all. Chem 2023;9(6):1335-1339. |
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Tan AX, Jun YS. Opportunities for emerging wastewater phosphorus recovery technologies to enable circular phosphorus usage in nontraditional hydroponic agriculture. ACS Agricultural Science & Technology 2023;3(4):318-321. |
R840084 (Final) |
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Tan AX, Michalski E, Ilavsky J, Jun YS. Engineering calcium-bearing mineral/hydrogel composites for effective phosphate recovery. ACS ES&T Engineering 2021;1(11):1553-64. |
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Tan XA, Jun YS. Enhanced phosphate removal through combination of wollastonite and calcium phosphate mineral seeds in alginate hydrogels. Presented at the 2022 Association of Environmental Engineering and Science Professors (AEESP) Research Conference, St Louis, MO, June 28-30, 2022. |
R840084 (Final) |
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Supplemental Keywords:
Harmful Algal Blooms, hydrogels, calcium phosphate, nitrogen, composites, phosphate, calcium silicate hydrate, nitrate, cyanotoxinRelevant Websites:
Environmental NanoChemistry Laboratory - The Jun Group Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.