Periodic Reporting for period 2 - P-TRAP (Diffuse phosphorus input to surface waters - new concepts in removal, recycling andmanagement (P-TRAP))
Período documentado: 2021-03-01 hasta 2023-08-31
P-TRAP focused on:
• P retention in agricultural areas with tile drainage by using filter systems based on iron(Fe)-containing by-products from water treatment or by taking profit from the natural Fe dynamics.
• Converting the P-loaded Fe-materials into P-containing Fe minerals and test their suitability as fertilizers.
• Improving the quality of lake waters by adding Fe-containing by-products
• Determining the mechanisms and rates of Fe mineral formations and constrain the consequence for P uptake and release by these minerals..
P-TRAP aligned with Sustainable Development Goals (SDGs), including SDG 2 (Zero Hunger) by addressing the role of P in food production and SDG 15 (Life on Land) by conserving terrestrial ecosystems. It also supported SDG 12 (Responsible Consumption and Production) by emphasizing circular economy principles for sustainable P management.
a) Retaining and Recovering P in Agricultural Drainage Systems:
Understanding P reservoirs in drained agricultural areas is the prerequisite for the development of mitigation measures. P budgets and fluxes were studied on a representative farm, revealing significant P reservoirs in topsoil that are slowly leaching into lower layers. Field experiments on adjusting groundwater levels with hydraulic measures revealed the risk of enhanced P export when ground water levels reach the topsoil. Various systems for removing dissolved P using Fe-containing by-products were explored. The possibility of using P-loaded materials as fertilizers or converting them into marketable fertilizers through microbial processes, like bio-vivianite, was investigated at laboratory scale. To test the suitability of vivianite and P-loaded Fe minerals as fertilizers, pot experiments were conducted using a variety of soils, crops and cultivation techniques.
b) P Binding in Lake Sediment:
The objective was to stabilize P in lake sediments using Fe-containing by-products from water treatment. Field tests at two sites showed that Fe addition can effectively reduce P release into the water from sediments. However, care must be taken to maintain the right P to Fe ratio to avoid unintended consequences, such as increased P flux during anoxic conditions.
c) Fe Mineral Transformation:
Laboratory experiments aimed to understand Fe mineral transformations and their kinetics in various systems, including soils, sediments, drainage systems, and bioreactors. Advanced techniques were used to characterize the interactions between Fe and P in detail. This work informed modeling for predicting P-containing Fe phases' behavior across different contexts. Fe-containing by-products from water treatment were studied for reactivity, particularly in P binding and sediment treatments. Results included the influence of silicic acid and cations on recrystallization rates and P release and the formation and dissolution of vivianite, a phosphate mineral. Mathematical models were developed to predict P release under various conditions.
Overall, this research provided critical insights into complex Fe-P interactions in different environments, contributing to the understanding and application of P-TRAP technologies.
It was demonstrated, that Fe oxides can be transformed into the phosphate mineral vivianite through microbial reactions when sufficient P is introduced. The efficiency of vivianite and Fe phosphates as P fertilizers showed varying results depending on factors such as grain size and preparation of the materials. Promising results were obtained with vivianite as a P fertilizer when it is applied to slightly acidic soils, which are submersed in water, such as rice paddies. This opens the door to P recovery, potentially reducing the dependence on mined phosphorus. The mechanisms and rates for the dissolution, precipitation and transformation of multiple Fe minerals were established, creating the basis to develop quantitative models for designing and evaluating innovative approaches developed within P-TRAP. Beyond its scientific contributions, P-TRAP has fostered collaborations among research groups, consulting firms, governmental stakeholders, and fertiliser companies in Europe. This has provided early-stage researchers with opportunities to develop academic and non-academic skills and expand their professional networks, facilitating career advancement within and beyond academia.