Grantee Research Project Results
2022 Progress Report: Phosphorus Removal to Oligotrophic Levels: Innovating Three High-Flow Water Technologies using Reactive Filtration, Biochar Adsorption, and Nanobubble-Enhanced Biomimetic Separations
EPA Grant Number: R840087Title: Phosphorus Removal to Oligotrophic Levels: Innovating Three High-Flow Water Technologies using Reactive Filtration, Biochar Adsorption, and Nanobubble-Enhanced Biomimetic Separations
Investigators: Möller, Gregory , Strawn, Daniel , Baker, Martin
Institution: University of Idaho
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, 2021 through August 31,2022
Project Amount: $999,996
RFA: Approaches to Reduce Nutrient Loadings for Harmful Algal Blooms Management (2020) RFA Text | Recipients Lists
Research Category: Water , Harmful Algal Blooms , Waste Reduction and Pollution Prevention , Water Quality
Objective:
The objectives are 1) life cycle assessment (LCA) and technological economic analysis (TEA) of reactive filtration water treatment systems; 2) advancing a novel biochar water treatment process for phosphorus adsorption onto biochar for removal and recovery from wastewater effluents; and 3) development of an advanced, high-flow particle separations technology based on biological and natural processes for removal of nutrients from treated waters.
Progress Summary:
Life cycle assessment of a municipal wastewater facility achieving ultralow phosphorus removals.
Dual upflow reactive filtration by a slowly moving sand bed with continuously renewed, hydrous ferric oxide-coated sand is used for removing polluting substances and for meeting the ultralow 0.05 mg/l total phosphorus discharge permit limits at a 1.2 million liters per day (0.32 million gallons per day) water resource recovery facility in Plummer, Idaho, in the United States. A life cycle assessment (LCA) of this reactive filtration installation was carried out to assess the environmental hotspots in the system and analyze alternative system configurations with a focus on CO2 equivalent (CO2e) global warming potential, freshwater and marine eutrophication, and mineral resource scarcity. “What if” scenarios with alternative inputs for the energy, metal salts, and air compressor optimization show trade-offs between the impact categories. Key results that show a comparative reduction of global warming potential include the use of Fe versus Al metal salts, the use of renewable energy, and the energy efficiency benefit of optimizing process inputs, such as compressor air pressure, to match operational demand. The LCA shows a 2 × 10−2 kg CO2e footprint per cubic meter of water, with 47% from housing concrete, and an overall freshwater eutrophication impact reduced by 99% versus no treatment. The use of renewable hydropower energy at this site isolates construction concrete as a target for lowering the CO2e footprint.
Reactivity of biochar for phosphorus removal and recycling in water treatment.
Use of biochar to remove phosphorus (P) from wastewater has tremendous potential to reduce P loading into surface waters that degrade water quality and is also a promising technology for recycling P as a soil fertilizer. Use of biochar in wastewater treatment requires knowledge of P reaction processes as well as understanding the availability of the recovered P. In this research, P sorption behavior and reaction products on three different biochars and an activated carbon were studied, including unmodified and iron-modified biochar. Sorption isotherms at pH 6.5 showed that a biochar produced from feedstock from a magnesium-enriched cow manure anaerobic digest solid had the greatest sorption capacity (2300 mg/kg), followed by the activated carbon (1500 mg/kg), and the two biochars produced from woody biomass (0-300 mg/kg). Modifying the biochar with 2% Fe, by mass, increased sorption capacities of the woody biomass biochars (1200 mg/kg to 2000 mg/kg) and the activated carbon (2300 mg/kg) but decreased sorption capacity of the anaerobic digest biochar (1700 mg/kg). Molecular analysis of the biochars using P K-edge X-ray absorption near edge (XANES) spectroscopy indicated that, except for one of the biochars, calcium phosphate minerals such as hydroxyapatite were the predominant species on the biochars. However, Fe modification promoted P sorption on sites similar to sorption sites on iron oxide minerals, which may be a ternary iron-oxygen-phosphorus bond on the Fe-modified biochars. Phosphorus desorption from unmodified woody feedstock biochars in a stirred-flow reactor was more available (greater than 80% to 30% of total P released) than in the biochar produced from the anaerobically digested cow manure (less than 1%). Iron modification of the woody feedstock biochar decreased P release be 0% to 3% of its total P content, but increased P desorption to ~3% of total P in the anaerobic digest feedstock biochar. Results provide fundamental information needed to advance utilization of biochar in wastewater treatment processes and as an enhanced efficiency fertilizer in soils.
Biomimetic crossflow filtration with wave minimal surface geometry for particulate biochar water treatment
Wave minimal surfaces (WMSs) are mathematically defined structures that are commonly observed in nature. Their unique properties have allowed researchers to harness their potential for engineering applications. Since WMSs can be represented by mathematical equations, the geometry can be parametrized and studied using computational fluid dynamics (CFD) for particle separation. Low energy particle separation in water treatment can yield low-carbon footprint technology approaches such as biochar water treatment where removal and recovery of adsorbed N and P on biochar can address water pollution, climate change and food security. The objective of this work was to demonstrate the capability of WMS as a crossflow filtration system to remove particulates in water. For this purpose, we used CFD to optimize WMS geometry and studied the performance of the 3D-Printed (3DP) optimized WMS using experimental fluid dynamics (EFD) in a water tunnel. CFD studies quantified planar vorticity, fluid filtrate flux, and particle behavior of WMS. For inflow velocities of 0.2-0.4 m/s, CFD results showed that a reverse wave filter design with convex shape leading-edge, angle of incidence of 90o, and maximum width of n=1.0 captured 15-25% of upstream velocity at the filter port. CFD analysis showed more than 95% separation efficiency at velocities and pressures of 0.2-0.32 m/s and 5-35 kPa, respectively. Particle Image Velocimetry (PIV) was used for EFD fluid flow measurements with an optimized wave minimal surface (OMWS). Comparison of OMWS CFD and PIV velocity fields showed good agreement with a root-mean-square error of less than 10%. Particle size analysis showed that the 3DP OMWS could filter particle sizes ranging from 1-30 µm with at least 50% particle count reduction in the filtrate. Thus, we successfully demonstrated a novel framework for analyzing a crossflow water filtration system from conceptual design to initial benchtop experiments using iterative CFD, 3DP, and EFD.
Biochar water treatment field pilot-scale studies.
Two weeks of field pilot trials of biochar water treatment at a municipal wastewater facility and at high-flow agricultural field drains showed excellent phosphorus removals at pilot process scale flows over two weeks of operations. Treating about 10 gpm (0.63 L/sec) of the discharge outfall at the wastewater facility was 48,000-gal total (181,440 L/sec) and with agricultural field drainage at 5 gpm (0.32 L/Sec) was 24,000-gal total (90,720 L), we demonstrated 96% and 89% TP removals respectively with field optimized treatment protocols. Moreover, the municipal wastewater data showed about 95-99+% destructive removals for a range of chemicals of emerging concern such as pharmaceuticals and hormones.
Future Activities:
- Continued biochar water treatment process modification, characterization, and enrichment process with protocol development targeting phosphorus adsorption to develop a mechanistic understanding of biochar modification process impacts at a bench scale and in pilot processes.
- Continued greenhouse trials with recovered nutrient-loaded biochar materials.
- Biochar enrichment reactive filtration field pilot-scale trials of process and equipment testing in preparation for YR3 field trials at impacted areas, and watershed source pilot-process reactive-filtration biochar water treatment.
- Sustainability surveys development and coordination for AL, MN, and MA reactive filtration site visits are ongoing with site travel expected in 2023.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 8 publications | 6 publications in selected types | All 6 journal articles |
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Type | Citation | ||
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Yu P, Baker M, Crump A, Vogler M, Strawn D, Moller G. Biochar integrated reactive filtration of wastewater for P removal and recovery, micropollutant catalytic oxidation, and negative CO2e: process operation and mechanism. Water Environmental Research 2023;95(9):e10926. |
R840087 (2022) R840087 (2023) |
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Supplemental Keywords:
Biochar, reactive filtration, biomimicry, water treatment, nutrients, phosphorusRelevant Websites:
Department of Soil and Water Systems 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.