CAREER: Enabling sustainable phosphorus recovery through integration of classical nucleation theory and particle population balance modeling

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

The utilization of phosphorus fertilizers has been critical to maximizing crop yields in agriculture and farming to feed a growing world population. Unfortunately, the release of excess phosphorus (P) from agricultural runoffs and municipal wastewater treatment plants (WWTPs) has also led to a widespread nutrient enrichment in surface water systems, a process commonly referred to as eutrophication. In P-limited surface water systems, eutrophication causes a decrease in water quality, oxygen depletion, a loss of aquatic biota, and the occurrence of harmful algal blooms that adversely impact communities that rely on surface water systems for drinking water, fishing, recreational activities, and tourism. To meet a growing demand of P fertilizers while protecting critical water resources and ecosystems, a growing number of municipal WWTs have installed additional treatment trains to recover struvite, a magnesium ammonium phosphate hexahydrate mineral that can be used as a slow-release fertilizer in agriculture and farming. However, the lack of a fundamental understanding of struvite crystal growth and precipitation in wastewater has led to uneven performances of struvite recovery reactors and a growing skepticism about the viability of P-fertilizer recovery in municipal wastewater treatment plants (WWTPs).The overarching goal of this CAREER project is to advance the fundamental understanding of struvite crystals growth and recovery in wastewater with the specific aim of developing and validating modeling tools that could be used by engineers and practitioners to tune and control the growth, precipitation, and recovery of valuable P mineral fertilizers from WWTPs. The successful completion of this project will benefit society through the generation of new fundamental knowledge to advance the development of a circular phosphorus economy between urban population centers and rural food production regions. Additional benefits to society will be achieved through education and training including the mentoring of a graduate student and an undergraduate student at the University of Illinois at Urbana-Champaign (UIUC). The establishment of circular phosphorus (P) flows between urban population centers and rural food production regions has emerged as a critical sustainability challenge of the 21st century. To address this challenge, the recovery of the mineral P-fertilizer struvite (MgNH4PO4•6H2O) from municipal wastewater is increasingly being evaluated and implemented in the United States and worldwide. This CAREER project will lay the scientific and technological foundations for the development of next generation technologies to recover P-fertilizers from municipal wastewater. The specific objectives of the research are to: 1) Evaluate and quantify the impact of environmental conditions on struvite nucleation rates and energetics on model inorganic and organic substrates to elucidate mechanisms of crystal formation using classical nucleation theory and advanced analytical tools including ex-situ atomic force microscopy (AFM) and grazing incidence small angle x-ray scattering (GISAXS); 2) Develop, calibrate, and validate a dynamic particle population balance model for struvite growth in recovery reactors; and 3) integrate the struvite particle population balance model within an open-source plant-wide modeling framework with the ultimate goal of establishing design criteria and operational guidelines for struvite recovery in WWTPs. The successful completion of this project has the potential for transformative impact through the development of new fundamental knowledge and modeling tools to advance the design and implementation of next generation processes and technologies to recover P-based mineral fertilizers from municipal wastewater. To implement the educational and training goals of this CAREER project, the Principal Investigator (PI) proposes to pilot an environmental engineering/science summer camp with hands-on learning activities that will focus on broadening participation in STEM higher education through the recruitment and retention of high school students in Urbana-Champaign. In addition, the PI plans to develop and pilot a professional mentor network for undergraduate and graduate students that are enrolled in the UIUC Department of Civil and Environmental Engineering (CEE) in collaboration with the department’s “Advancement, Communications, and Alumni Relations” team. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.