Excellence in Research: Delineating the characteristics, transformation and water quality impacts of landfill leachate induced dissolved organic nitrogen

In the United States, the discharge of excess nitrogen into surface water bodies (e.g., lakes, rivers, and estuaries) is causing pervasive and vexing environmental problems ranging from harmful algal blooms (HABs) to complete eutrophication that negatively impact water quality nationwide. Current research on nitrogen (N) water pollution has primarily focused on inorganic nitrogen (e.g. nitrate).

Dissolved organic nitrogen (DON), while often a large fraction of the nitrogen from wastewater plant effluents, has been historically overlooked. Recent studies by the Principal Investigators of this project and others suggest that landfill leachates are significant sources of DON with comparable N mass flows as wastewater effluents and agricultural runoffs.

The goals of this research are to characterize DON from landfill leachates, evaluate its eutrophication potential, and its removal efficiency in wastewater treatment plants using biological nutrient removal processes. The successful completion of this project will benefit society through the development of new fundamental knowledge that could be used to inform nitrogen removal during wastewater treatment as well as water quality managers interested in mitigating HABs.

Further benefits to society will be achieved through stakeholder/public outreach and student education/training including the mentoring of one doctoral student and an ungraduate student enrolled at an HBCU (North Carolina A&T State University).

Current research on nitrogen (N) pollution in surface water bodies has focused primarily on inorganic nitrogen, i.e., nitrate from agricultural runoff and wasterwater plant effluents. However, there is growing evidence that dissolved organic nitrogen (DON) from landfill leachates is a significant source of N pollution. DON from landfill leachates has been shown to consist of two broad classes of compounds 1) proteinaceous DON and 2) humic substances (HS) derived DON.

These two fractions have different molecular compositions with distinctly different behaviors during algal growth stimulation and N removal in wastewater treatment plants using biological nutrient removal (BNR) processes. The overarching goal of this research is to comprehensively investigate the occurrence, characteristics of DON from landfill leachates, its degradation and transformation patterns in various BNR process scenarios/configurations, and its impacts on harmful algal blooms.

To advance this goal, the Principal Investigators of this project propose to carry out an integrated experimental program structured around three specific objectives: 1) Correlate occurrence and composition of DON with landfill characteristics (e.g., age and stabilization stage), 2) Elucidate the degradation, transformation, and removal of landfill leachate induced DON in conventional and short-cut BNR processes, and (3) Evaluate the impacts of landfill leachate induced DON on harmful algal bloom dynamics. These specific objectives will be accomplished by coupling state-of-the-art DON characterization studies with laboratory scale BRN experiments and field DON leachate collections followed by bioassays of algal growth and stimulation.

The successful completion of the proposed research could provide new data and fundamental knowledge to guide the mitigation of water pollution and HABs by DON.

This award is jointly funded by the Environmental Engineering and Evironmental Sustainability programs of the NSF/ENG/CBET Division and the Broadening Participation in Engineering program of the NSF/ENG/EEC Division.

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.