SPS Abstracts

Session 1: Feast or Famine: P Sustainability in Agriculture

  • Redistribution of soil phosphorus fractions due to the use of cover crops in a soybean monoculture crop sequence
    Ana Paula Giannini, National Institute of Agricultural Technology (INTA)

    Sustaining biomass production in the future and avoiding negative impacts on the environment, requires improving current phosphorus (P) management strategies. The aim of this study was to evaluate the effect of including cover crops (CC) in soybean monoculture on total, organic, inorganic, and extractable P (TP, OP, IP, and Pe, respectively) and soil organic carbon (SOC), yield and aerial dry matter after four and eight years in a typical Argiudol from the Argentina rolling pampa. In a 31-year trial under no tillage was carried, where a crop rotation with or without CC (60% oats; 40% vetch) was evaluated. A 12 kg of P ha-1 year-1 was applied at soybean sowing. Soil samples were taken at 0-5, 5-10, 10-20 and 20-30 cm. There were no differences in soybean yield between treatments over the time. The CC increased TP by 10 and 21% at 0-5 cm and 9 and 18% at 5-10 cm, after four and eight years, respectively. The additional carbon input from CC progressively increased the SOC stock, which was correlated with TP at 0-30 cm (p<0.01). The OP did not differ between treatments. The OP issued from the CC, particularly from vetch, would provide fast recycling organic fractions to the soil, that are mineralized increasing IP, delivering it in synchrony with the requirements of the commercial crop. The IP correlated with Pe (p<0.01). This technology leads to maintain soybean yields without resorting only to increased phosphorus fertilizer doses, improving soil quality in the medium term.

  • Long-term effects of continuous cover crop species management on phosphorus dynamics in a mollisol
    Adebukola O. Dada, Soil Health Institute

    Cover crops (CC) reduce soil phosphorus (P) losses by decreasing the soil available pool through biomass production during the non-growing season. The potential of CC to recycle biomass P into the soil while redistributing the soil P fractions can be affected by CC specie and the duration of management. Therefore, this study aimed at determining the effect of long-term CC species management on the labile, moderately labile, and non-labile P fractions at the soil surface. Soil samples were collected from long-term managed field with cereal rye Secale cereal L. (CR), annual ryegrass Lolium multiflorum (AR), oats/radish, Raphanus sativus L/Avena sativa (OR) and control (CN) having no CC at 0 – 2 and 2 – 4 cm depth. Sequential fractionation method was used to separate the soil P into different pools based on their degree of solubility. Long-term CC species management significantly affected the soil inorganic P.

  • Phosphorus distribution and speciation at micro-scale in a long-term cultivated Brazilian Oxisol
    Leonardus Vergütz, Mohammed VI Polytechnic University

    Phosphate rock contains calcium-phosphorus species (e.g., hydroxyapatite) that are a source of P to crops after their solubilization and diffusion in the soil. However, the phosphate anion can be fixed on Fe and Al clay mineral surfaces and become unavailable to plants. To understand these changes, we used synchrotron-based microprobe techniques (μXRF and μXANES) to assess P speciation in a 1-μm spatial resolution in the interface of a fertilizer grain in the soil. An undisturbed soil sample was taken from a long-term experiment conducted in Brazilian Cerrado (Oxisol). We sampled the topsoil (0-5 cm) in a plot cropped for 21 years under no-tillage system and continuously fertilized with phosphate rock (100 kg/ha/yr P2O5). The sample was fixed in a P-free organic resin and was mapped by μXRF to assess the distribution of Al, P, and Si. Then, P K-edge μXANES spectra were collected in a transect from P hotspots (fertilizer) to the bulk soil. In the P hotspots, hydroxyapatite (P-HAp) confirmed the location of the fertilizer grain. In the soil/fertilizer interface we found P-HAp transforming to dicalcium phosphate (P-Ca, 5-17%) and P adsorbed on gibbsite (P-Al, 32-44%). Inside the soil aggregate, further from the fertilizer, P adsorbed on ferrihydrite (P-Fe) was also found (18-47%). The results showed short distance range transformations of P into less available species (P-Fe and P-Al). Our methodology allowed us to better understand the mechanisms controlling the fate of P from the fertilizers in tropical soils. This knowledge is useful to improve P fertilization efficiency for crops.

  • Microbial activity and P uptake by cover crops exploring legacy P  in the long-term in Brazil
    Paulo S. Pavinato, University of São Paulo – ESALQ/USP

    We evaluated the microbial activity and its relationship with P cycling by cover crops in three scenery exploring Legacy P after 12 crop seasons in Brazil. The trial was conducted from 2009 to 2020, with soybean and corn as cash crops and six cover crops in the off-season (vetch – Vicia sativa, white lupin – Lupinus albus, fodder radish – Raphanus sativus, ryegrass – Lolium multiflorum, black oat – Avena strigosa, rye – Secale cereale). They were cultivated with three phosphate sources (rock phosphate as input of 1078 kg ha-1 of total P, single superphosphate as input of 335 kg ha-1 of total P, and control without P input. Both phosphate sources added 35 kg ha-1 of soluble P annually between 2009 and 2015, being suppressed in the last five seasons for exploration of the legacy P. It was determined in soil samples the C and P of microbial biomass (MBC and MBP), acid phosphatase, β-glucosidase and P resin, besides P uptake by cover crops. More soil available P by fertilizers addition strongly increased the MBC (r2: 0.75, p: 0.001), MBP (r2: 0.84, p: 0.001) and plant P uptake (r2: 0.87, p: 0.001), otherwise phosphatase (r2: -0.31, p: 0.02) and β-glycosidase (r2: 0.21, p: 0.049) activities were not affected by P addition. Only RP increased substantially the availability of P in the soil after 12 years (P-RTA), as a residual effect of the high amount added.

  • Role of soil minerals on organic phosphorus availability and phosphorus uptake by plants
    AMADOU Issifou, UniLaSalle

    Organic Phosphorus (OP) represents a significant fraction of the total P pool in soils. With the increasing use of organic resources to substitute mineral P fertilizers and the need to recover P from the soil, it is pivotal to gain insight into the interactions between various OP forms and soil minerals and their consequences on P availability.  Here, we aim at elucidating the extent to which OP compounds adsorbed onto major soil minerals may be available to plants. Ryegrass (Lolium multiflorum) plants were grown in RHIZOtest devices in the presence of OP (myo-inositol hexakisphosphate (IHP), glycerophosphate (GLY) and glucose-6-phosphate (G6P) and inorganic P (IP) compounds that were previously adsorbed onto Fe and Al oxyhydroxides (goethite and gibbsite, respectively) and clay minerals (montmorillonite and kaolinite). Phosphorus availability and P uptake were then determined through rhizosphere and plant characterization. Irrespective of the type of mineral, ryegrass was able to take up about 3-18% of adsorbed OP compounds. The magnitude of availability and uptake depended on the OP compounds and the type of soil minerals. The potential availability of OP adsorbed by different minerals was strongly mediated by mineral-OP interaction types and properties. The P uptake increased in the following order: kaolinite-OP << gibbsite-OP ≤ goethite OP << montmorillonite-OP. Phosphorus uptake from adsorbed OP compounds showed contrasting pattern compared to adsorbed IP and depended on available P in the rhizosphere and not necessarily on the binding strength of OPs to the mineral surface.

  • Improving phosphorus use efficiency by chickpea crop using electromagnetic induction, soil properties, and crop yield data under semi-arid conditions
    Mohamed Chtouki, Liege uneiversity Gembloux Agro Bio Tech

    Under arid and semi-arid conditions, the agricultural sector faces many challenges related to the use of water and mineral resources for crop production and food security for an exponentially growing population. The impact of climate changes on water resources availability and soil quality is more and more emphasized under the Mediterranean basin, mostly characterized by drought and extreme weather conditions. The present study aims to investigate how electromagnetic induction technique and soil mapping combined to crop yield data can be used in crop modeling for the optimization of phosphorus use efficiency in semi-arid conditions. The study was conducted in 2-years agronomical experiments of 2.5 ha chickpea grown under drip fertigation regime. Soil spatial variability was first assessed by the measurement of soil apparent electrical conductivity (ECa) using the CMD Mini-Explorer sensor, then soil physicochemical properties were evaluated based on an oriented soil sampling scheme to explore other soil spatial variabilities influencing chickpea yield and quality. Data from the first agronomic experiment were used in geostatistical, multiple linear regression, and fuzzy c-means unsupervised classification algorithms to properly identify P drip fertigation management zones (MZs). The identified Mzs were verified by the one-way variance analysis for the studied soil and plant attributes, revealing that the first MZ1 presents a high grain yield, high soil P content and low ECa. The low fertility MZ2 was located in the south part of the studied site and presents a low chickpea grain yield due to the low P content and the high ECa. By conducting a second agronomic experiment using the concept of P variable rate drip.

  • Biodegradable polymer nanocomposites for controlled release and targeted delivery of phosphorus during crop growth
    Nubia Zuverza-Mena, The Connecticut Agricultural Experiment Station

    Phosphorus is an essential nutrient for plant growth. However, the availability of phosphorus in soil is limited by complexation with organic matter and phosphorus adsorption to inorganic minerals. When phosphorus is applied as a fertilizer, the low use efficiency of phosphorus can cause run-off and negatively impact aquatic environments. To reduce the environmental impact of P containing fertilizers, we are developing a number of controlled release and biodegradable biopolymer nanocomposites made from polyhydroxyalkanoate (PHA), cellulose, lignin, starch, and other similar materials as part of the NSF Center for Sustainable Nanotechnology and a separate but related USDA AFRI award. In initial greenhouse studies with tomato, polymer nanocomposites (PNCs) containing polyhydroxyalkanoate (PHA) and calcium phosphate nanoparticles were shown to produce equivalent tomato vegetive growth and fruit quality as compared to conventional phosphorus amendments but exhibited a 90% reduction in nutrient loss from the soil. We are currently embedding phosphorus containing materials such as amorphous calcium phosphate nanoparticles, hydroxyapatite nanoparticles, hydroxyapatite microparticles, as well as conventional calcium phosphate monobasic and calcium phosphate dibasic salts, into the polymeric matrices. We are also incorporating select micronutrients into these materials. We are using this strategy to study both polymer type and phosphorus source/size on crop growth and nutrient loss from soil under soil column, greenhouse and field conditions. Our studies show that tunable nanocomposites can effectively and efficiently deliver phosphorus while dramatically reducing the environmental impact of P-ru

  •  Assessing the Efficiency of Soil Moisture Sensors to Measure Phosphorus Transport
    Zoe Stroobosscher, University of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Education Center

    Precision irrigation technologies, such as in-field soil moisture sensors, can provide detailed semi-real time information on the movement of water in the soil, changes in soil temperature (ST), and electrical conductivity (EC). These on-farm technologies could increase water use efficiency more than 40%. However, growers are not taking full advantage of all the information available from these sensors. The incorporation of EC and ST on top of soil moisture could provide growers with the appropriate tools to manage both irrigation and fertigation plans. In this study, we 1) determine the minimum ortho-phosphate concentration that can be captured indirectly by using EC, SM, and ST real-time data, and 2) evaluate if commercial SMSs are able to capture the movement of ortho-phosphates applied through fertigation. SMSs were installed in soil cores that represented the field soil layers of a representative soil in south Florida with high salinity levels and contrasted with pure sand cores. Two pre-made mixes with phosphate concentrations of 0, 10 and 100 ppm were applied into the cores uniformly and the movement of phosphorous was evaluated after 24 hours post-application. The results obtained from the SMS readings were contrasted with those obtained by soil lab test. Preliminary results show that the SMSs are able to provide readings.

  • Avoiding Phosphorus Losses while Optimizing Yield: Fertilizer Recommendation Support Tool (FRST)
    Sarah E. Lyons, North Carolina State University

    Avoiding build-up of phosphorus (P) in agricultural soils is the best way to control nonpoint source losses, while optimizing agricultural yields.  Soil testing is an important tool to this end but often soil test correlation and calibration work has been siloed across boundaries, such as states or small countries, leading to very different recommendations for the same soil and cropping systems. The Fertilizer Recommendation Support Tool or FRST is an initiative to reduce cross boundary differences in soil test recommendations for P and potassium across state boundaries.  Land grant faculty from 38 institutions, as well as USDA agency personnel and not-for-profit organizations, are working in an intentional fashion to gain agreement on the components or soil test correlation and calibration: minimum dataset identification for research trials, relative yield definition, critical soil test correlation model selection, and ultimately the decision tool. The overall goal of FRST is to advance the accuracy of soil-test-based fertilizer recommendations by developing a database and decision tool from which recommendations can be scientifically developed and defended as best management practices by forming a community of practice. FRST has already begun to meet many of its objectives, as documented at the FRST website: soiltestfrst.org.

  • Transformation of Soluble Phosphate within Manure to a Less Soluble Calcium Phosphate Solid
    Tian Zhao, McGill University

    Manure has a long history as an effective fertilizer, as it is rich in nutrients. However, due to the nutrient imbalance between the plants’ needs and intensive agricultural activities, excess soluble P from manure can flow into natural waters and cause eutrophication.

    This project aims to solve this problem by decreasing the soluble phosphate in manure, therefore, reducing the P run-off risk of manure application. The cementitious phase in recycled concrete contains hydraulic lime, a source of calcium and alkalinity. Soluble P in a manure-water-waste cement mixture likely forms amorphous calcium phosphate (ACP) under alkaline conditions. ACP has lower phosphate solubility than manure and can be considered a slow-release phosphate fertilizer or an alternative to phosphate rock as a P fertilizer raw material. Crushed cement powder separated from recycled concrete was mixed in different ratios with diluted manure slurry. Preliminary results showed a significant reduction of soluble phosphate concentration with cement treatment. Design of Experiment (DoE) determined two optimal cement treatment groups. The inorganic apatite-type phosphate fraction increased with cement treatment suggesting Ca-P solids formation. Cement-treated manure showed a lower phosphate fertilizer efficiency and phosphate solubility than mineral P fertilizer in a pot test. Between the 8 groups in the pot test, the soil pH ranged from 6.4-6.9 except for a cement-only control (7.4). Waste cement treatment of manure has a high potential to reduce the P run-off risk while providing sufficient crop nutrients.


  • Faisalabad- Pakistan, Phosphorus uptake efficiency and recycling affected by phosphorus enriched poultry-compost amendment during wheat (Triticum aestivum L.) cultivation
    Imran Ashraf, University of Agriculture

    Low phosphorus (P) use efficiency is a major reason of low wheat yield around the globe especially in the developing countries like Pakistan. A study was conducted to investigate the impact of phosphorus enriched poultry compost on P use efficiency and recycling in wheat (Triticum aestivum L.). Wheat was cultivated in calcareous soil of central Punjab region of Pakistan where phosphorus was applied as inorganic fertilizers, poultry manure and poultry manure enriched with inorganic phosphorus.  Inorganic sources of phosphorus were diammonium phosphate (DAP), single super phosphate (SSP), and rock phosphate along with control (only soil indigenous P). Organic source of phosphorus included poultry compost and poultry manure enriched with inorganic phosphorus. After harvest, the effects of compost and P fertilizers on various parameters were significant. Shoot length, root length, root diameter, number of leaves per plant, shoot fresh weight, shoot dry weight, root fresh weight and root dry weight of wheat were recorded higher in compost treatment (where compost was applied). After harvesting of the crop, plant height, spike length, number of spikelets per spike, number of grains per spike, 1000-grain weight, grain yield and biological yield were recorded. Soil p kinetics were determined after every two week. It was concluded that that phosphorus uptake efficiency and recycling was enhanced where poultry manure enriched with inorganic phosphorus was applied along with improvements in the soil health.


Session 2: Quantifying Phosphorus Flows and Impacts for Sustainable Nutrient Management

  • Bioavailability of legacy phosphorus in a long-term cultivated Brazilian Cerrado Oxisol under different tillage systems and fertilization managements
    Elton Eduardo Novais Alves, Mohammed VI Polytechnic University

Cerrado croplands represent 60% of the Brazilian agricultural production. The continuous fertilization result in the buildup of P in the soil (known as legacy P), which might be available to future crops. We aimed to assess the bioavailability of legacy P in a long-term experiment testing two soil management systems (conventional-CT and no-tillage-NT), two P sources (triple superphosphate-TSP and phosphate rock-PR, 35 kg/ha/yr of P), and two methods of application (sowing furrow-F and broadcasted-B). The site, a Brazilian Cerrado Oxisol, has been continuously cultivated for 25 years, of which 17 years received continuous fertilization and the last 8 years no fertilization. We sampled the experiment after 17 (2011) and 25 (2019) years of continuous cultivation and compared the P fractions and P species across all treatments. After 8 years without fertilization, the total P content in the topsoil decreased under NT and CT (-197 and -123 mg/kg). Furthermore, regardless of the application method, NT increased the labile P in 2011 (125 vs 34 mg/kg, NT vs CT) and in 2019 (27 vs 14 mg/kg). In the NT, the mod-labile and labile P fractions decreased (-96 and -80 mg/kg), and in the CT non-labile fraction decreased (-59 mg/kg). P-Fe and P-Al are the main species across all treatments and increased over time (77% in 2011 and 88% in 2019). P-Ca and organic-P species were depleted under CT but were still found in NT after 8 years without fertilization. Overall, NT showed a higher bioavailability of legacy P with PR as a phosphorus source.

  • Sustainable Phosphorus Management  across Systems and Spatial Scales
    Tan Zou, University of Maryland Center for Environmental Science

“Applying phosphorus (P) in agriculture supports crop and animal production. However, poor management of nutrients from field to fork leads to environmental problems.

Progress has been made toward nutrient reduction goals for the Chesapeake Bay watershed through improved on-farm management strategies. However, progress brought by advanced on-farm practices is limited, and little attention has been paid to key stakeholders and strategies beyond the farm and to connecting these systems, which may also play crucial roles in sustainable nutrient management. To that end, we introduce a novel nutrient management framework, CAFE, to connect nutrient management across the Cropping system, Animal-crop system, Food system, and Ecosystem. Here we apply CAFE to the Chesapeake Bay watershed as a case study.

We quantified the P budgets and P use efficiencies (PUEs) for four CAFE systems and multiple spatial scales (e.g., county scale) through 1985-2019. We found that in 2019, more than 60% of all counties in the watershed had P surplus (a measure of potential P loss) beyond crop farms larger than cropland P surplus, with more P potentially lost at animal production and food processing and retail. We also analyzed the relationships between P budgets and potential drivers. We found that, for example, Animal-crop system PUE decreased as agricultural production increased, and a larger ecosystem surplus was found in counties with a larger population. The CAFE framework offers promise for finding P losses beyond croplands that could be mitigation targets.”

  • Quantifying and Mapping P-Flows in the Economy of Ontario, Canada
    Edgar Martín Hernández, Université Laval

“One of three recommendations from the 2018 report published by the National Nutrient Recovery and Reuse Forum [1] was to study the phosphorus flows in and out of Canadian economies. Environment and Climate Change Canada sponsored a report, recently published by Pollution Probe, that estimated the agricultural, urban, and industrial flows in, out, and around the Canadian province of Ontario and their spatial distribution within the province [2].

Three academic groups estimated P-flows through the economic sectors of Ontario. The BioEngine group at Université Laval estimated the magnitude and interconnections between agricultural P-flows using open data sources.  The University of Waterloo group calculated the reported and estimated the unreported P-releases by manufacturing and wastewater treatment sectors using public databases and scaling-up factors. McGill University researchers estimated the  P-flows through selected industrial sectors, including forestry, steel production, metal treatment, food and beverage processing, aquaculture and pet food processing.

Phosphorus recovery and recycling opportunities have been identified, determining the flows to which future efforts should be devoted for the management of P. These mainly belong to the agricultural sector, including manure (30.5 kt/year) and slaughterhouse waste (3.7 kt/year), although significant amounts of P are also found in food and organic waste, including municipal wastewater (6.4 kt/year). A number of technologies at commercial or pilot stage for recovering P from these flows are discussed, and although P-recovery technologies for other industries are not as advanced, this should not prevent stakeholders in seeking P-recovery solutions for other industries.

[1] https://www.iisd.org/sites/default/files/meterial/nutrient-recovery-reusecanada.pdf

[2] https://www.pollutionprobe.org/mapping-phosphorus-flows-in-the-ontario-economy/”

  • Phosphorus legacies and saltwater incursion constrain recovery of water quality benefits in a restored coastal wetland
    Marcelo Ardon, North Carolina State University

Coastal wetland restoration is being used as a climate change mitigation tool and to decrease excess nutrient loading to sensitive estuarine systems. In coastal areas with a history of agricultural practices, the interactions between fertilizer legacies, changes in storm magnitude, and increasing frequency and duration of saltwater incursion events could limit the recovery of water quality benefits from wetland restoration. Here, we use fourteen years of weekly surface water samples from a coastal restored wetland, a mature forested wetland, and an agricultural field to examine patterns in phosphorus export. Our study period included six drought events (Palmer Drought Severity Index less than -2) and five major hurricanes (higher than category 3). We found that initial flooding lead to the release of legacy phosphorus from soils. Both droughts and storms led to increases in the release of nitrogen and phosphorus from all three land-uses, but the magnitude of storm-driven pulses in the restored wetland has declined since the initial reflooding. Our results suggest that elevated P release after reflooding of coastal wetlands is an important, but temporary problem, which is exacerbated by saltwater release of legacy fertilizer. An improved understanding of the vulnerability of fertilizer legacies in coastal areas to increasing extreme events is needed to inform large-scale coastal wetland restoration efforts.

  • Mapping Animal Feeding Operations in the United States: Improvements Seen with Parcel Data
    Arghajeet Saha, Arizona State University

Increased demand for livestock products associated with rapid industrialization and vertical expansion has increased the size of animal feeding operations (AFOs) and concentration of manure in regional systems around the US. Some concentrated areas of AFOs generate the same amount of nutrient waste that is released by cities. As a result, identifying the location of AFOs is essential to implementing nutrient control plans for water quality restoration. However, the locations of a significant amount of AFOs are unknown to the public due to limitations of federal and state level regulations. The existing measures to map AFOs in the US employ manual assessment, aerial imagery, and LiDAR and NDVI data. However, these methods are labor-intensive, computationally complex, prone to human errors, and often not applicable across large spatial or temporal scales. Using machine learning (ML) to predict AFO locations reduces the constraints of the previous methods. Our existing work on ML uses publicly available socioeconomic and remote sensing data to determine AFO locations with up to 93.6% accuracy in 1-km raster resolution. With the availability of parcel data, the accuracy of prediction can be increased since parcel data covers individual property boundaries and has more realistic resolution than the square-shaped, randomly applied, 1-km raster grids. Existing urban development and land use studies have indicated such improvement in mapping accuracy and land cover classification with the pre-defined parcel boundaries. This presentation aims to show the advances of parcel-level ML applications to locate AFOs in comparison with the raster-grid level predictions.

  • National trend assessment of total phosphorus concentration and load using a continental-scale deep learning model
    Wei Zhi, Penn State University

Phosphorus is a vital element for human life and agricultural production yet excess phosphorus has led to global issues of water quality degradation. A national trend analysis of total phosphorus (TP) concentration and load is important but currently lacking to assess our past nutrient management efforts due to large data gaps over the past decades, especially since there is a limited number of TP gages in the early 1980s and 1990s. In this work, we overcome this limitation by training a continental-scale deep learning TP model with 426 basins to reconstruct the continuous historical record of daily TP concentration and load from 1980 to 2020. Results show the deep learning model achieved a state-of-the-art continental-scale performance with a median Nash–Sutcliffe Efficiency of 0.68. The long-term trend analysis showed that 40% of basins are improving in TP concentration, especially in the East and West, while the Midwest is showing significant regional deterioration. The spatial pattern of TP load is much more spatially heterogeneous than that of TP concentration, exhibiting a larger disparity between the West and the East with the dominant TP export in the East. The small TP load in the West is due to its drier condition and less streamflow. A break-down analysis showed that 23% of improving basins with lower TP concentration, however, are stable in TP load trends. This suggests that streamflows in these improving basins are increasing, indicating that the climate-induced change in precipitation might mask our nutrient management efforts in reducing TP load.

  • Estimating spatial and temporal variability of Phosphorus hydrologic losses across the contiguous United States
    Kimia Karimi, North Carolina State University

The removal/loss pathway of nutrients from different sources in aquatic ecosystems are important for informing nutrient management. These hydrologic losses of nutrients are vital components in many hydrological models, and have a wide range of spatial and temporal variability. While many nutrient sources have been characterized, some nutrient budgets do not account for hydrologic losses, especially at larger scales. We estimate Phosphorus (P) losses in 166 watersheds across the US at the approximate scale of the 4-digit Hydrologic Unit Code (HUC 4) subregions from 1997-2017. P loadings in these watersheds are obtained using weighted regressions of concentrations (and loads) on time, discharge, and season. Our results show that areal P loss varies greatly across time and space. The average P loss in larger watersheds range from 0.2 to 120 kg/km2/yr. On average, the largest areal P losses occur in Mid-Atlantic and Great Lakes. We will also explore the effect of different fluxes of P inventories coupled with climatic factors on the spatial and temporal variability of P losses.

  • Dynamic Modeling of phosphorus flows using Modelica language
    Saad Benjelloun, Mohammed VI Polytechnic University

To investigate the possibilities for a more sustainable use of phosphorus it is necessary to have a complete picture of the phosphorus flows in the global markets. To our knowledge, most of the phosphorus transport models, if not all, are static. This means that the models give a clear and detailed representation of phosphorus flows at a given time, but do not allow predictions to be made.

Based on substance flow analysis (SFA), we have set the goal of building a dynamic model of the Phosphorus market that has the capacity to capture the temporal evolution. The core foundation is a “dynamic systems modeling” of P flow, based on the Modelica language.

Therefore, the phosphorus supply-demand chain is divided into several subsystems, including agricultural subsystems (arable, grazing, intensive livestock) and non-agricultural subsystems (food industry, non-food industry, feed industry, household, waste management, environment).

Quantification of the various phosphorus flows between the subsystems was based on various data sources. This analysis was made for the 2000-2019 period for Morocco (or the Netherlands) and will be implemented for other geographical regions.

On the one hand, this dynamic modeling can be used to look backward and assess past developments and events, while on the other hand it can also be applied to the future in order to evaluate and compare respective scenarios, through a “what if” approach.

Examples of assessments, and options for a more sustainable use of Phosphorus, particularly the analysis of recycling ins and outs, will be discussed.

  • Linking global terrestrial and ocean biogeochemistry with process-based, coupled freshwater algae-nutrient-solid dynamics
    Minjin Lee, Princeton University

Estimating global river solids, nitrogen (N), and phosphorus (P), in both quantity and composition, is necessary for understanding the development and persistence of many HABs and hypoxic events. This requires a comprehensive freshwater model that can resolve intertwined algae, solid, and nutrient dynamics, yet previous global watershed models do not mechanistically resolve instream biogeochemical processes. We develop a global, spatially explicit, process-based, Freshwater Algae, Nutrient, and Solid cycling and Yields (FANSY) model and incorporate it within the NOAA/GFDL Land Model LM3. The resulting model, LM3-FANSY, explicitly resolves interactions between algae, N, P, and solid dynamics in rivers and lakes at 1-degree and 30-minute resolution. Simulated solids, N, and P in multiple forms (particulate/dissolved, organic/inorganic) agree well with measurement-based yields (kg/km2/yr), loads (kt/yr), and concentrations (mg/l) across world major rivers. Furthermore, simulated global river suspended solid, N, and P loads to the coastal ocean are consistent with published ranges. River N loads are estimated to be approximately equally distributed among forms with particulate organic, dissolved organic, and dissolved inorganic N accounting for 37%, 34%, and 30% respectively. For river P load estimates, particulate P, which includes both organic and sorbed inorganic forms, is the most abundant form (58%), followed by dissolved inorganic and organic P (32% and 10%). LM3-FANSY can serve as a baseline for linking global terrestrial and ocean biogeochemistry in next generation Earth System Models aimed at understanding the effects of terrestrial perturbations on coastal eutrophication under multi-decadal socioeconomic and climate change projections, where novel conditions challenge empirical approaches.

  • OK, but what about nitrogen? The importance of N:P stoichiometry in the food-water system
    Jim Elser, Arizona State University

Much attention is rightfully focussed on phosphorus due to its sizable impacts on water quality and its central role in the food system as a component of agricultural fertilizer and feed supplements. However, nitrogen also has impacts on aquatic ecosystems and is essential for fertilizers. However, P cycling and sustainability are often studied and managed independently from N. This is unfortunate as this separation of approaches means that often management decisions lead to highly imbalanced N:P stoichiometry at global, regional, and ecological scales. This talk will document the impacts of N:P imbalance, discuss its various causes, and highlight the need for connecting N management to P management to achieve planetary nutrient sustainability.

  • Re-Envisioning the Phosphorus Mass Flow Diagram for Convergent Research
    Rebecca Muenich, Arizona State University

Convergent boundary objects (CBO) provide a commonality among which researchers from various disciplines can communicate and develop new learning opportunities through the object’s inherent flexibility of interpretation. Within the STEPS (Science and Technologies for Phosphorus Sustainability) Center, convergent research is an overarching goal to integrate researchers from disciplines such as education and economics to materials engineering and limnology. Generalized and specific phosphorus mass flow diagrams have served as one such CBO since the conception of the STEPS Center. These diagrams describe the estimated flow of phosphorus in and moving between certain pools. Mass flow diagrams originated from engineering disciplines and are commonly used to quantify and analyze process flows for chemicals and other elements, from materials to end product scales. While seemingly straightforward in their simplicity, the spatiotemporal variations, myriad assumptions, lack of boundary systems and limited socio-economic influences in these diagrams has led to considerable debate, discussion, and research across disciplines within the Center. In this presentation we will describe different disciplinary perspectives of the P-flow diagram as a CBO, including potential to re-envision the flow diagram as a dynamic CBO with boundaries defined by complex socio-environmental systems. This exercise of re-imagining phosphorus mass flow diagrams has already led to new ideas and convergence activity and should facilitate future research efforts around pathways to sustainable phosphorus management.

Session 3: AnthroPocene – Urban P and Human Impacts

  • The drivers of intention to use a web-based water quality monitoring tool in a western Nebraska community
    Anni Poetzl, University of Nebraska – Lincoln

    Human behavior plays an integral role in water resources management, and tools that facilitate knowledge transfer such as web-based water quality databases receiving real-time data from local, in-situ sensors can provide a basis of communication and inquiry among resource managers and stakeholders. Surveys were distributed to identify the antecedents of intention to adopt a free, web-based water quality monitoring tools with moderators including stakeholder type (producer v. urban). Survey results were analyzed (N=171) and results suggest that the perceived performance expectancy (β=0.44,  p < 0), the expectancy of the tool to address the individual’s water quality interests, significantly predicts intention. When personal norm, the strength of an individual’s feeling of obligation toward protecting and monitoring local surface waters, is moderated by gender (β=-0.13 (males, N=51); β =0.36(females, N=19), p<0.01), it also significantly predicts intention, yet the moderator of stakeholder type had no significant effect on behavioral intention to adopt a tool. These findings can inform areas of growth to increase adoption of management tools and ultimately increase participation in water resources management.

  • Accelerating Water Quality Restoration with In-lake Management
    Scott Shuler, EutroPHIX – A Division of SePRO Corporation

    Water Quality in the United States is significantly impaired for phosphorus pollution with greater than 48,000 lakes exceeding phosphorus standards.  Increased eutrophication drives an increased frequency and severity of harmful algal blooms (HABs).  As the primary limiting nutrient for productivity of freshwater systems, a single pound of phosphorus can drive the growth and standing crop of up to 500 pounds of algae. HABs can cause acute water quality issues, toxin production, taste and odor issues, aesthetic impacts, as well as impacts to recreational uses and property values. Harmful algal toxins can have significant acute impacts to pets, wildlife, and human health. The Clean Water Act has worked to improve the condition of lakes since it was enacted in 1972 and has significantly reduced point source pollution over the last 50 years. Additional efforts are needed for improving watersheds and curtailing non-point source pollution. A relatively small effort has been made for in-lake water quality improvement. Given the investment needed to restore watersheds and the time required for implementation and positive water quality impacts at the lake level – additional in-lake management should be considered to accelerate water quality improvement. Phosphorus mitigation at the lake level is a viable management strategy to restore waterbodies and improve designated uses.

  • Developing a source tracking framework for the fate and transformation of nitrogen and phosphorous throughout a coastal estuary: Piney Point as a case study
    Amanda R. Chappel, University of Florida

    Spills and releases of high-nutrient wastewater have become chronic stressors on nearshore environments. In April 2021, a structural failure at the Piney Point phosphogypsum stack prompted the controlled release of approximately 814 million liters of phosphorus (P)- and nitrogen (N)-rich effluent into Tampa Bay, Florida. Here we use source-specific tracers to track the fate and transformation of nutrients released from this event. By measuring the stable isotope composition of nitrogen and carbon in particulate organic matter (del15N and del13C POM) and the oxygen isotope ratio of phosphate (del18OPO4), we seek to evaluate the biogeochemical transformations of N and P after this event. Four monitoring sites were established to complement the Tampa Bay Estuary Program’s seagrass monitoring transects. Multiparameter water quality sondes were deployed at each site and biweekly collection of nutrients and phytoplankton composition were coupled with stable isotope analyses. Following the discharge, localized increases in total phosphorus, orthophosphate, total nitrogen, and ammonia were seen. Preliminary data showed the del15N and del13C values of POM were within range of known end member values for phytoplankton with a high affinity for ammonia (-7 to -13 ‰ and -18 to -22 ‰, respectively), which was the dominant nitrogen species present in the stack discharge. The isotopic composition of POM agrees with the corresponding microscopy results, which identified diatoms as a predominate phytoplankton group in samples collected following the outfall event. These findings corroborate other research that has shown an increase in localized diatom growth soon after the initial discharge into the bay.

  • Controlling long-term phosphorus retention by iron amendments in anoxic lake sediments: Transformation of redox-sensitive to redox-stable iron-bound phosphorus and competing effects
    Lena Heinrich, University of Potsdam, Leibniz-Insitute of Freshwater Ecology and Inland Fisheries, Technische Universität Berlin, Brandenburg University of Technology Cottbus – Senftenberg

    The ferrous iron mineral vivianite binds phosphorus in anoxic lake sediments. To control vivianite formation as a new internal lake management approach for nutrient retention, we investigated its biogeochemical formation and competing effects. Anoxic laboratory experiments in sediments demonstrated that ferric iron hydroxide with adsorbed phosphorus acts as a precursor of vivianite. According to sequential extraction and X-ray diffraction within 40 days, 70% of the redox-sensitive iron-bound phosphorus was transformed into redox-stable phosphorus in the form of vivianite. This shows that the precursor can be immobilized within anoxic lake stratification periods. For phosphorus retention in anoxic iron-poor lake sediments, this offers the possibility to initiate the formation of the precursor by adding iron. Furthermore, a field study on two lakes to which iron was added showed that in both lakes the iron was retained in the sediments, but only in one lake vivianite formation increased phosphorus storage. In contrast, the binding of sulfur as iron sulfides prevented phosphorus binding in the second field study. Pore water analyses and modeling of sulfate concentrations in the water column and sulfur fluxes at the sediment-water interface of both lakes showed that the significantly higher sulfate reduction rate was responsible for the failure of long-term phosphorus retention after the iron addition. Thus, for the management of phosphorus retention in anoxic lake sediments by iron dosing, the competing process of iron sulfide formation needs to be considered for the whole management period. This can be achieved for example by applying additional iron.

  • Controlling Drinking Water Pipe Corrosion Using Less Phosphorus
    David Linville,  Aqua Smart Inc.

    The allowable levels of phosphorus discharged into the environment continue to be reduced. In some locations within the US, permissible levels are below 0.10 mg / l. Many wastewater treatment plants are already struggling to meet these reduced discharge requirements, and face significant capital expenditures to modernize plants or change unit operations to maintain compliance. As much as 35% of the existing wastewater phosphorus load comes from drinking water corrosion control additives. One of the anticipated effects of the upcoming lead and copper rule revisions is a significant increase in both the overall use, and concentration, of these additives, such as phosphoric acid. This is likely to have a dramatic effect on the amount of phosphorus added to the water supply, which will need to be removed by wastewater treatment plants.

    A novel chemical additive was developed which controls lead corrosion, often better than phosphoric acid, using up to 75% less phosphorus. Several studies were performed to demonstrate the effectiveness of the additive. Real-world performance, as measured by 90th percentile reported lead data, on 39 systems which began using, or continuously used, the additive since 2003 was studied. Systems which switched to the additive experienced a reduction in lead results from an average of 5.2 ug / l to 2.7 ug / l. Additional lab studies were performed, including soaked coupon tests, lead solder pipe loop tests, and harvested lead pipe tests. All demonstrate superior ability to control lead corrosion compared to phosphoric acid, using less phosphorus.

  • Electrochemical stabilization and resource recovery from source-separated urine
    Philip Arve, Clemson University

    Urine represents a small fraction of the total volume of a typical domestic wastewater stream, but contributes over half of the nitrogen (N) and phosphorus (P). Source separation of urine presents an opportunity to allow direct treatment of this highly concentrated waste stream, with potential recovery of N and P. Source separation of urine is not without its own operational difficulties; flushless urinals often have issues such as foul odors and clogging. This is in part due to the hydrolysis of urea by the urease enzyme which converts urea to ammonia. The hydrolysis of urea by urease can be irreversibly inhibited by hydrogen peroxide (H2O2) at relatively low concentrations. We previously showed that electrochemically synthesized in-situ H2O2 can stabilize source-separated urine when fed to the cathode chamber, though previous reactor designs relied on a Nafion membrane separating the anode and cathode chambers to prevent the anodic consumption of H2O2. We have now developed an electrochemical cell that relies on a sacrificial magnesium (Mg) anode to prevent anodic H2O2 consumption, thus allowing eliminating the need for a membrane. Mg was chosen for its low redox potential which would also avoid chlorine production, and to provide Mg ions for the precipitation of struvite (NH4MgPO4·6H2O) for P recovery. This way dissolved Mg is recovered along with P in a useful form. We will present our results demonstrating this new electrochemical cell, along with the proof-of-concept of concomitant struvite precipitation and urea stabilization from source-separated urine.

  • Evaluating the diversity of metal cations in microbial polyphosphate granules and their role in enhanced biological phosphorus removal processes at wastewater treatment facilities
    Jessica Deaver, North Carolina State University

    Enhanced biological phosphorus removal (EBPR) processes utilized in wastewater treatment minimize phosphorus in effluents discharged to natural waters preventing eutrophication. EBPR depends on polyphosphate accumulating organisms (PAOs) that can store inorganic phosphate as polyphosphate. Priming PAOs with an anaerobic zone prior to aeration stimulates PAO phosphate uptake to remove phosphorus from wastewater. Wastewater treatment utilities often report unstable phosphorus removal and factors affecting EBPR instability remain unclear. One potential factor is the available metal cations serving as counterions to negatively charged orthophosphate ions comprising polyphosphate granules. Previous studies demonstrated linkages between EBPR stability and cations Mg2+, Ca2+, K+, and Na+ in bench-scale and full-scale studies. Using scanning transmission electron microscopy/energy dispersive x-ray spectroscopy (STEM/EDS) on samples from full-scale facilities, our preliminary results show a larger cation diversity in the granules than previously reported. We found several heavy metal cations, notably Al3+, Pb2+, Ba2+, and Fe3+, and, in many cases, an absence of previously reported cations. Our work aims to understand if certain counterion(s) associated with polyphosphate granules yield more stable phosphorus removal and if the counterions utilized are specific to PAO species or strains present. We are using Nanopore 16S rRNA gene sequencing to elucidate microbial communities present and STEM/EDS to understand polyphosphate granule composition. To support field-scale observations, we are using bench-scale experiments to probe the influence of metal cation identity on phosphate uptake and release by PAO enrichment cultures. Outcomes of this work will help inform EBPR processes at wastewater treatment utilities to improve phosphorus removal stability.

  • Iron enhanced biowaste to recover lost phosphate and its potential application as a slow-release fertilizer for agriculture
    Chandra mouli Tummala, Wayne State University

    Direct application of phosphate fertilizer in agricultural fields can lead to >15% loss of total phosphate via agriculture runoff. Runoff containing excess phosphate fertilizer can create eutrophication in receiving waters, which has been linked to low dissolved oxygen, toxic compounds, and other problems. Slow-release phosphate fertilizers can be a potential solution to prevent this loss. . In this study we have coated iron onto the surface of waste pistachio and walnut shells to synthesize biowaste adsorbent material, which has been shown to recover the phosphates from the water system. We have conducted laboratory scale experiments to understand the phosphate uptake capacity, kinetics and demonstrate its potential slow-release application as an agricultural fertilizer. XRD analysis have shown the iron coating process led to the formation of hematite particles on the surface of the waste nutshells. Batch studies have shown both iron coated shells follow pseudo second order kinetics and agree with the Freundlich isotherm model. Column studies have shown that the maximum uptake capacity of the ron coated pistachio and walnut shells is 12.63 mg/g and 9.25 mg/g, respectively. Experiments to validate the slow release of phosphorus under soil-relevant conditions are in progress to determine if this biodegradable waste material can be used as potential slow-release fertilizers in the agricultural fields.

  • Competition for Phosphorus from the Battery Industry
    Linda Gaines, Argonne National Laboratory

    The world-wide rush towards electrification, especially in the transportation sector, has led to rapid growth in the demand for several key battery elements, most notably lithium, cobalt, and nickel. But tightening supply and technological developments will lead to increased battery demand for other elements as well. One battery cathode chemistry that is gaining broad acceptance is lithium iron phosphate (LFP) due to its latent manufacturing capacity in China, improvement in energy density, and reduced risk of fire relative to other cathode chemistries. The current impact on the phosphorus market is negligible, but the future potential may be quite significant. There is also the possibility of synergistic effects between the battery and agricultural markets via runoff recovery and recycling. This presentation will discuss the potential impacts of increasing LFP production on total the phosphorus market.

Session 4: Emerging Technologies for the Analysis and Transformation of Phosphorus

  • Unrevealed Roles of Polyphosphate-accumulating organisms and missing PolyP in global P cycling
    April Gu, Cornell University

    PolyP is likely ubiquitous and more abundant in nature than it has been recognized. Polyphosphate accumulating bacteria have received significant attention for their role in wastewater treatment systems. The frequent detection of PolyP with the biological origin at relatively high abundances indicates the significance of PAOs in the P cycle. Poly-P’s ubiquity in nature has been mainly attributed to microbial activities, as abiotic generation requires extreme temperatures and pressures rarely seen in nature. Owing to their unique physiology, they sequester phosphorus in excess of their cellular needs and adapt to oscillating redox conditions. In this presentation, we first review current knowledge on PAOs, with a focus on bacteria, in terms of their phylogenetic identities and metabolic pathways. We then examine both genetic and phenotypic methods for PAO detection and their associated strength and limitations. We further discuss the evidence that suggests the ubiquitous presence of PAOs in nature and point out the unrevealed roles of the PAOs in phosphorus storage and supply in the rhizosphere of soil, in eutrophication in water bodies and sediments, and in global carbon and nutrients cycling, which warrant future investigation. The biological component of most global P cycling models is based on a presumed C/N/P ratio of cells, whereas PolyP storage and degradation alters the C/N/P ratio and influences the fate and transformation of P species that can be rather significant. We argue that polyphosphates accumulating bacteria likely play an important but yet to be explored role in phosphorus release and storage in soils, eutrophic water resources, and global nutrient and carbon cycles.

  • The case for phosphorus recovery from downstream wastewater effluent
    Oded Nir, Ben Gurion University of the Negev

In the current paradigm of phosphorus (P) removal and recovery from wastewater, most of the P mass is directed towards the sludge, and then extracted from the separated sludge stream by different methods. Some notable routes are biological P removal, and recovery of struvite or vivianite from anaerobic digested sludge liquids, and acid leaching of P from sludge ash. A different, complementary approach allows P to flow uninterruptedly to the treated effluent, extracting high-purity P downstream. This approach has significant advantages such as (1) Saving costs associated with upstream nutrient removal; i.e. aeration and chemicals addition (2) Avoiding high- P in the sludge – increasing P recovery yield, (3) avoiding the need for P separation from high organic content in the sludge, (4) minimizing both organic and inorganic contaminants, (5) allowing flexibility in reusing the treated effluent for agriculture.The challenge downstream P recovery is the relatively low P concentrations in the effluent, similar to the untreated wastewater. Nevertheless, this technical issue can be effectively addressed through research and development. This talk will discuss the benefits of making effluents the primary targets for nutrient removal and recovery. Moreover, It will present practical low-cost processes for obtaining high-purity and high value P from effluents by integrating membrane separation, sorption, and crystallization.

  • Use of phosphate organomineral associated with solubilizing microorganisms in maize cultivated in Brazil
    Flavia Cristina dos Santos, Embrapa Maize and Sorghum

The phosphorus (P) availability in the soil can be increased managing phosphate fertilization and using P-solubilizing microorganisms (PSM). This work aimed to evaluate the use of organomineral phosphate associated with PSM in maize. The field experiment was carried out at Embrapa Maize and Sorghum (Sete Lagoas-MG, Brazil), in a Oxisol, with a very clayey texture, with medium to adequate P content (4.0 mg dm-3 of P Mehlich 1), for two consecutive seasons. The design was a randomized block with 5 replicates, 2×3 + 6 additional treatments. Two sources of P, 1- organomineral based on chicken litter (CL) with Bayovar reactive rock phosphate associated with two MSP (B. thuringiensis and B. subtilis) and 2- triple superphosphate (TSP), and 3 doses of P2O5 (60, 120 and 180 kg ha-1), plus the treatments: a) CL with MSP, b) CL without MSP, c) Bayovar with MSP, d) Bayovar without MSP, e) organomineral dose 180 without MSP and f) control (without P and MSP). For both seasons, maize yield was the same for organomineral and TSP treatments. However, the yield for maize grown with organomineral 180 with MSP weighed 894 kg ha-1 more, in the sum of the two seasons, than without MSP. Moreover, for the first season, the N, P and K extraction was higher in the treatment with organomineral compared to TSP and available P in the soil (Mehlich 3) was higher in the presence of MSP, compared to Bayovar treatments. These results showed the potential of alternative P sources associated with MSP.

  • Bioavailability and Crop Uptake of Phosphorus from Three Different RhizoMAP Formulations
    Aaron Waltz; Phospholutions, Inc.

Controlled-release phosphorus (P) fertilizers are considered to provide P to soil at rates that are more synchronized to varying crop nutrient requirements during the growing season compared to conventional quick-release P fertilizers. A replicated greenhouse experiment in which corn (Zea mays L.) was cultivated in a sandy soil over a twelve-week period, was conducted to monitor the solubilization and plant acquisition of RhizoMAP-derived P compared to Monoammonium Phosphate (MAP)-derived P. We evaluated three distinct chemical formulations of RhizoMAP, namely: 1) 1:1.5 RhizoMAP; 2) 1:2 RhizoMAP; and 3) 1:4 RhizoMAP, against MAP. All three RhizoMAP formulations were produced in an industrial process that involves the co-granulation of powdered RhizoSorb® and MAP at specified component ratios (RhizoSorb®: P2O5) creating controlled-release P fertilizers. Phosphorus fertilizers were applied at a dose equivalent to 100, 75, 50, and 0% of the recommended P rate, and P fertilizer solubility was determined by recovering soil solution using lysimeters. The shoot and root P concentrations were measured at different corn growth stages to evaluate plant P acquisition patterns in the different treatments. The highest soil solution P concentrations were observed in the 100% MAP treatment where concentrations peaked at week 1 and then progressively declined to near background levels after six weeks (mean 0.45 ± 0.05 mg P L-1). From this point onwards, RhizoMAP treatments maintained the most stable and highest P levels in solution. In general, all treatments accumulated more P from the soil than in the 0P control treatment (p < 0.05). The shoot and root P content and total plant P were found to be similar between 100% MAP treatment and all the RhizoMAP treatments (there was no significant difference observed between the three RhizoMAP formulations), despite a 25% and 50% reduction in P applied. These results support the use of RhizoMAP as a sustainable controlled-release P fertilizer for crop growth. Further research is needed to evaluate the effectiveness of RhizoMAP in long-term field experiments.

  • Why Nature chose phosphates and how phosphorus research can be inspired by Nature
    Baile Wu, Arizona State University

Phosphate plays a central role in life: a basic component of ATP, phospholipid, and DNA. For these reasons, phosphorus is conceived as an essential and unreplaceable element of life. Therefore Nature has evolved many biochemical processes involved phosphate, for example, protein dephosphorylation via phosphatase and phosphate transport through phosphate binding protein. But why Nature chose phosphate? How phosphorus research can be inspired by Nature? In this talk, I will first explain the unique properties of phosphate that make it selected by evolution for biochemical transformations: high acidity, high stability, and electrostatic effects. Then I will introduce two basic phosphorus transformation processes that can be inspired by Nature. The first one is organic phosphorus hydrolysis. By mimicking the function of phosphatase, we developed a series of materials including metal (hydr)oxide, carbon materials, and polymers to hydrolyze organic phosphorus into inorganic phosphate. Such materials platform can find applications in phosphorus geochemical cycling, total phosphorus removal and recovery from waste streams, and bio-related phosphorus sensing. The second process is inorganic phosphate adsorption. Inspired by the mechanisms used by phosphate binding protein, we summarized the most fundamental aspects of selective phosphate adsorption processes. Based on the differences in acid–base properties, geometric shapes, and metal complexing abilities, selective adsorption of phosphate over other competing anions can be achieved through hydrogen bonding, shape complementarity, and inner-sphere complexation. We developed iron-, zirconium-, lanthanum-, and cerium-based materials and investigated their performance for selective removal of phosphate through batch/pilot-scale experiments, advanced materials characterization and theoretical calculations.

  • Applications of the oxygen isotope ratio of phosphate to identify phosphorus sources in agricultural areas
    Shin-Ah Lee, North Carolina State University

Identifying the origin of phosphorus (P) is essential to understanding the cycling of nutrients in natural environments, and for applying targeted management strategies to reduce excess P in the environment. The stable oxygen isotope ratio of phosphate (δ18OPO4) has been applied as a tracer to understand the source and processing of P in soil and water ecosystems. We aim to determine seasonal changes in the source of P and the contributions of each primary source between pre-fertilization and post-fertilization in an agricultural area. For this study, we collected soil samples at the Tidewater Research Station, Plymouth, NC in January, March, and June 2022 and water samples from the surrounding area. Potential endmembers were also sampled including swine lagoon liquid, treated wastewater effluent, and fertilizer. To measure the oxygen isotope ratio of phosphate, we applied the silver phosphate (Ag3PO4) method (Jaisi and Blake, 2014) to extract and purify phosphate. The concentrations of nutrients (total phosphorus, nitrate, ammonium, and total Kjeldahl nitrogen) and organic matter were measured for water and soil samples. Additionally, the stable isotope values of carbon (δ13C) and nitrogen (δ15N) of particulate organic matter, as well as deuterium (δD) and oxygen (δ18O) isotopes of water were also measured. Preliminary results indicate that the δ13C values of endmembers are distinct and range from -11.01 ‰ to -30.16 ‰. This study suggests that a multi-stable isotope framework may be useful to discriminate the source of phosphorus in agricultural systems, and this information can be used to control and regulate P management.

  • Towards environmental remediation systems based on phosphorus-binding agents
    Alexey Gulyuk, North Carolina State University

Currently, the problem of reusing available natural resources and, particularly, removing various chemical pollutants from water sources is a problem that receives a lot of attention. There are research concepts exploring designed agents with high affinity to bunding with organic and inorganic compounds. Such agent can serve as a foundation for protein-based systems that will allow to capture, remove and recover pollutants like Phosphorus, which is a widely-used in soil fertilizers that ends up in groundwater. In our project we work on developing protocols for Molecular Dynamics (MD) simulations of solvent and protein-based systems that form stable bound with agents like phosphates or PFOS. Derived concepts open paths for applying the most effective compounds and agents in industry or agriculture.

  • Efficient removal of organophosphorus compounds by adsorption on metal hydroxides/oxides nanostructures
    Gayani Pathiraja, Joint School of Nanoscience and Nanoengineering

The excessive concentration of phosphorus in the aquatic environment leads to eutrophication that is a serious environmental threat worldwide. Therefore, several efforts have been made to remove or degrade the organophosphorus compounds from the wastewater. Among different physical, chemical, and biological approaches, absorption is a popular cost-effective and simple process, and it can be applied to remove different toxic pollutants. By selecting absorbent materials with higher surface area, higher binding affinity and abundance, the higher efficiency of removal can be achieved in the wastewater treatment plants. In this study, one-dimensional (1D) metal hydroxide/oxide nanostructures like Cu(OH)2 nanowires as an adsorbent was used to adsorb phosphate functional groups in the organophosphorus compounds with high selectivity. This crystal surface energy induced adsorption of organophosphorus compounds on to copper hydroxide nanocrystals facilitate the efficient removal of organophosphorus compounds in the water. The respective UV-Visible, Fourier transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopies confirm the adsorption of organophosphorus compounds on to Cu(OH)2 nanowires. The scanning transmission electron microscopy- energy-dispersive X-ray spectroscopy (STEM/EDX) elemental maps also support the adsorption process. This novel cost-effective phosphate removal method could serve as a cheap and effective way of selective removal of phosphates by fine tuning the crystal facet energy of metal hydroxide/oxide nanocrystals to treat wastewater effluents.

  • Exploration of low energy hydrophobicity-exploitative flotation process to selectively separate P-rich biomass from anaerobic digestate
    Bailee Maija Johnson, McGill University

The influent to the City of Ottawa municipal wastewater treatment plant (ROPEC) controls the effluent phosphorus concentration by adding iron (III) chloride to precipitate dissolved inorganic phosphates in its recycled activated sludge. Aluminum hydroxides from the upstream potable water plant are also a sewage component that adsorb and precipitate phosphate. The final ROPEC anaerobic digestion effluent composition is approximately 2% solid biosolids and contains many iron and aluminum inorganic phosphates with limited bioavailability. After dewatering, these biosolids are distributed for land application.The current method of dewatering is centrifugation, an energy intensive separation process. The mining/mineral processing industry uses a lower energy separation and concentration process called “flotation”. Flotation is a selective physical process which separates minerals by exploiting their different hydrophobicity (repulsion to water) values. The potential to use flotation to selectively dewater primarily the phosphorus-rich biomass – by enriching the froth layer with P at the top of the flotation process separately from the inorganic phosphate salts collected at the bottom of the flotation process – motivates this project.Preliminary dewatering flotation experiments were conducted with a model organism (Saccharomyces cerevisiae) and a Partridge-Smith microflotation tube. Preliminary spectroscopy measurements indicate hydrophobicity is increased in the flotation product in the froth layer. Preliminary flotation tests also showed the potential for total phosphorus concentration in the froth layer. Subsequent tests will explore flotation in an anaerobic environment using purple phototrophic bacteria, a facultative anaerobic capable of accumulating phosphorus as polyphosphate, and whose biomass could serve as a possible agricultural fertilizer.

  • Prayon Ecophos Loop Process : An innovative process for phosphorus recovery out of sewage sludge ashes
    Hubert Halleux, Prayon

Prayon is the market leader in phosphate processes through its Prayon Technologies division and high-quality phosphate production, with four plants in Europe and the United States. The portfolio of technologies offered by Prayon covers almost all phosphate markets and aims to answer the challenges of the modern phosphate industry such as depletion of high-grade phosphate rock, environmental concerns linked to the production and use of phosphate, as well as the challenging phosphate market.

In this context, phosphate recovery from waste products – secondary sources- is necessary. Therefore, Prayon is very active in these aspects of the industry by developing and proposing several technologies, as well as using secondary phosphates in its facilities.

One of the technologies proposed by Prayon is the production of phosphoric acid from sewage sludge ash. This process initiated by Ecophos, has been further developed and validated since the acquisition of Ecophos’s technology portfolio by Prayon in 2019. The phosphoric acid quality obtained meets Prayon’s standards for technical applications such as phosphate salts and soluble fertilizers.

The presentation will focus on this technology through key results obtained during pilot tests performed in 2021 at Prayon’s pilot and semi-industrial plant at Technophos in Bulgaria.