CAREER: Next generation onsite wastewater treatment system for nitrogen management

Millions of households in the United States and worldwide rely on onsite systems for wastewater treatment and disposal. Conventional onsite wastewater treatment systems (OWTS) consist typically of septic tanks connected to leach fields to enable the transport and disposal of liquid effluents in the surrounding soils via networks of drainage pipes. OWTS are predominantly designed to provide primary treatment during which organic wastes and suspended solids in household sewage settle to the bottom of septic tanks where they are partially degraded by microorganisms.

Because OWTS are not designed to effectively remove nutrients, the liquid effluents of septic tanks are among the largest sources of nitrogen (N) pollution for shallow groundwater aquifers as they leak into the surrounding subsurface soils. The overarching goal of this CAREER project is to explore the development and validation of the next generation of biofiltration systems for nitrogen (N) removal from OWTS.

To advance this goal, the Principal Investigator proposes to test the hypothesis that biofiltration systems based on the integration of anaerobic ammonium oxidation (anammox) microbiomes with sorbents such as biochar could provide efficient and cost-effective solutions for N removal from the liquid effluents of septic tanks. The successful completion of this project will benefit society through the generation of new fundamental knowledge to support the development and deployment of more efficient and sustainable solutions to manage and mitigate N pollution from households and other facilities that are not connected to centralized wastewater treatment systems.

Additional benefits to society will be achieved through student education and training including the mentoring of one graduate student and one undergraduate student at Stony Brook University.

Soil-based biofiltration systems have emerged as promising add-on modules to onsite wastewater treatment systems for the removal of nitrogen (N) from the effluents of septic tanks. However, current soil biofilters require a large footprint and an external carbon source (e.g., woodchips) to stimulate and support the growth and metabolic activity of denitrifying microorganisms.

This CAREER project will explore the development of novel soil biofilters for N removal based on a hybrid physical/chemical and biological treatment process that integrates biochar sorbents with anaerobic ammonium oxidation (anammox) microbiomes. The proposed research builds upon the results of previous investigations that have established that anammox microbiomes play a critical role in the conversion of N compounds to dinitrogen (N2) gas in soils, wetlands, and marine/freshwater sediments.

The specific objectives of the research are to: 1) investigate the partial denitrification/anammox (PDN/An) of N compounds in model biofiltration units using biochar as sorbents and microbiome carriers; 2) evaluate the effects of operational changes and environmental parameters on the efficiency of PDN/An biofiltration units and, 3) investigate and optimize the operation of a modular biofiltration system for efficient N removal and evaluate the system’s long-term performance using molecular tools and kinetic modeling. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge to advance the development and implementation of more efficient soil-based biofilters for removing N from the liquid effluents of onsite wastewater treatment systems.

To implement the educational and outreach activities of this CAREER project, the Principal Investigator (PI) proposes to leverage existing programs and resources at Stony Brook University (SBU) to develop and deliver new learning opportunities in environmental engineering (EE) for K-12, undergraduate, and graduate students with a focus on engaging female students. The proposed education and outreach activities will include 1) a one-week summer program to provide Long Island middle school students (7-9th Grade) with hands-on learning activities in engineering and technology and 2) a 10-week outreach program during the academic year to host 5-10 female students and introduce them to the science and engineering of soil-based biofiltration systems for onsite wastewater treatment.

In addition, the PI plans to develop and host a monthly environmental engineering seminar designed to expose SBU students to a broad range of perspectives and expertise to increase their breadth and depth of knowledge in EE

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.