Grantee Research Project Results
2023 Progress 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 Period Covered by this Report: September 1, 2022 through August 31,2023
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 ecosytems, and impact the economic output of industries. One major contribution to HABS is nutrient pollution from anthropogenic activities. To reduce nutrient pollution, we are developing novel mineral-hydrogel composites to effectively remove phosphorus (P) and nitrogen (N), and we will also determine their effects on algal growth. Calcium alginate hydrogels seeded with calcium phosphate (CaP), wollastonite (CaSiO3), or struvite (MgNH4PO4) are synthesized for effective phosphate and ammonium removal and recovery. We further demonstrate the mineral-hydrogel composites’ effectiveness for HAB mitigation in both benchtop cyanobacteria cultures and scaled up photobioreactor growth experiments.
Progress Summary:
We examined the simultaneous removal of nitrogen and phosphorus, 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.
We developed core-shell structures for the mineral-hydrogel composites by utilizing a positively charged polymer as a shell material. While a PEI coating on Ca-Alg/CaP+Wollastonite slightly improved P removal, further development should be made to offset the added coating and operational costs. In the future, we plan to utilize a PEI coating to remove other nutrients, such as nitrate, adding a dual functionality to the core-shell structure.
The water treated by mineral-hydrogel composites effectively reduced the growth of various algal species, including fast-growing ones like Synechococcus elongatus, toxin-producing Microcystis aeruginosa, and natural algal consortia from local ponds. The mineral-hydrogel composites hindered algal growth by removing nutrients from complex wastewater matrices. Additionally, we tested 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.
To predict microbial growth under different nutrient and environmental conditions, we developed a MATLAB-based platform called MAGMA (Micro-Algae Growth Modeling Application). When the platform is fully developed, it can be useful for uncovering HAB dynamics and toxin production.
Future Activities:
We will examine the PEI core-shell mineral hydrogel for nitrate and phosphate removal to provide dual functionality. Also, in a scaled-up system we will collect replicate data for algal growth prevention with treated wastewater by mineral hydrogels. This knowledge will be captured by algal growth models and HAB simulations. Lastly, we will systematically evaluate and model the nutrient removal ability of the mineral-hydrogel composites, to support their scaled up application in complex aqueous matrices. Utilizing all experimental data, we will finalize the algal growth and nutrient consumption kinetic model. Additionally, we are developing technical solutions for preventing HA
Journal Articles:
No journal articles submitted with this report: View all 7 publications for this projectSupplemental Keywords:
Harmful Algal Blooms, Hydrogels, Calcium Phosphate, Nitrogen, Composites, Phosphate, Calcium Silicate Hydrate, Nitrate, CyanotoxinRelevant Websites:
Environmental NanoChemistry Laboratory 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.