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

磷肥的利用对于最大限度地提高农业和农业产量以养活不断增长的世界人口至关重要。不幸的是，农业径流和城市污水处理厂（WWTPs）释放的过量磷(P)也导致地表水系统中广泛的营养物质富集，这一过程通常被称为富营养化。在磷含量有限的地表水系统中，富营养化导致水质下降、氧气消耗、水生生物群丧失以及有害藻华的发生，对依赖地表水系统饮用水、捕鱼、娱乐活动和旅游的社区产生不利影响。为了满足对磷肥不断增长的需求，同时保护关键的水资源和生态系统，越来越多的市政污水处理厂安装了额外的处理装置来回收鸟粪石，鸟粪石是一种六水磷酸铵镁矿物，可作为农业和农业中的缓释肥料。然而，由于对鸟粪石晶体在废水中的生长和沉淀缺乏基本的了解，导致鸟粪石回收反应器的性能不均匀，人们对城市污水处理厂（WWTPs）磷肥回收的可行性越来越怀疑。本CAREER项目的总体目标是促进对废水中鸟粪石晶体生长和回收的基本理解，具体目标是开发和验证建模工具，这些工具可以被工程师和从业者用来调节和控制污水处理厂中有价值的磷矿物肥料的生长、沉淀和回收。该项目的成功完成将通过产生新的基础知识来促进城市人口中心和农村粮食生产区之间循环磷经济的发展，从而造福社会。通过教育和培训，包括伊利诺伊大学厄巴纳-香槟分校（UIUC）的一名研究生和一名本科生的指导，将为社会带来额外的好处。在城市人口中心和农村粮食生产区之间建立磷循环流动已成为21世纪可持续性的重大挑战。为了应对这一挑战，从城市污水中回收矿物磷肥鸟粪石（MgNH4PO4•6H2O）在美国和世界各地越来越多地被评估和实施。该CAREER项目将为开发从城市污水中回收磷肥的下一代技术奠定科技基础。本研究的具体目标是：1)利用经典成核理论和先进的分析工具，包括非原位原子力显微镜（AFM）和掠射小角x射线散射（GISAXS），评估和量化环境条件对鸟粪石在模型无机和有机基质上的成核速率和能量学的影响，阐明晶体形成机制；2)开发、校准和验证回收反应器中鸟粪石生长的动态粒子群平衡模型；3)将鸟粪石粒子种群平衡模型整合到一个全厂范围的开源建模框架中，最终目标是建立污水处理厂鸟粪石回收的设计标准和操作指南。通过开发新的基础知识和建模工具，推动从城市废水中回收磷基矿物肥料的下一代工艺和技术的设计和实施，该项目的成功完成有可能产生变革性影响。为了实现这个职业项目的教育和培训目标，首席研究员（PI）建议试点一个环境工程/科学夏令营，其中包括实践学习活动，重点是通过招募和保留厄巴纳-香槟市边缘化和代表性不足群体的高中生，扩大STEM高等教育的参与。此外，PI计划与土木与环境工程系的“发展、沟通和校友关系”团队合作，为就读于该学院的本科生和研究生开发和试点一个专业导师网络。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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 from marginalized and underrepresented groups 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.