Grantee Research Project Results

Electrochemical process for recovering nitrogen and phosphorus from source-separated urine to reduce nutrient loads to domestic wastewater treatment plants

EPA Grant Number: SU841129
Title: Electrochemical process for recovering nitrogen and phosphorus from source-separated urine to reduce nutrient loads to domestic wastewater treatment plants
Investigators: Popat, Sudeep
Institution: Clemson University
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: March 1, 2025 through February 28, 2027
Project Amount: $75,000
RFA: 21st Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity, and the Planet Phase I (2024) RFA Text
Research Category: Groundwater, Contaminant Fate and Transport , Groundwater, Contaminants, Treatment , Health Effects , Pollution Prevention/Sustainable Development , Harmful Algal Blooms , Clean Water , Waste Reduction and Pollution Prevention , Groundwater, Organic Contaminants, Treatment, Modeling , Water Quality , Human Health , Water , Land and Waste Management , P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Challenge Area - Sustainable and Healthy Communities , Sustainable and Healthy Communities , Environment , Water Treatment

Description:

For this research project, we propose that a team of undergraduate students, guided by the P.I. and a graduate student, develop a novel approach of concomitant stabilization of fresh source-separated urine with preferential struvite precipitation using a sacrificial Mg anode and carbon-based gas-diffusion cathode. The proposed research for this project will be divided into four tasks. Tasks 1 and 3 will be related to experimental work performed by two teams of four undergraduate students, primarily during two summer semesters. The experimental work will focus on the proof-of-concept, followed by pilot-scale design and operation. Tasks 2 and 4 will be integrated into a Capstone Design class that the P.I., Dr. Popat, teaches every spring semester.

Objective:

Human urine contains most of the nitrogen (N) and phosphorus (P) that is received bycentralized wastewater treatment plants (WWTPs), both of which, if released into receiving water bodies, rapidly degrade water quality through algal blooms and eutrophication. Conventional approaches to removing these compounds from municipal wastewater rely on biological processes and are energy-intensive and operationally sensitive. Undiluted source-separated urine could provide an opportunity to remove N and P in more efficient ways, but source-separated urine is an ephemeral medium; through the activity of the urease enzyme released by several microorganisms, urea is rapidly degraded to a putrid liquid that deposits hard-to-remove scaling on plumbing fixtures. We propose the development and design of an electrochemical process: to 1) prevent the transformation of fresh source-separated urine to the putrid liquid that results from urea hydrolysis and microbial growth, 2) stabilize and precipitate the recoverable nutrients, N and P, from urine in a form that may be recovered for recycling in agriculture, and 3) reduce N and P released to the environment degrading quality of natural water bodies. The electrochemical process described in this proposal can precipitate most of the P in source-separated urine as struvite and prevent microbial growth and hydrolysis of urea through the electrosynthesis of hydrogen peroxide in situ in source-separated urine. The remaining N in source-separated urine, urea, may be processed further and recovered as an N-rich fertilizer.

Expected Results:

The project is designed to provide results across several scales relevant to developing electrochemical processes for treating source-separated urine. For example, Task 1 will provide results on the rates and extent of stabilization of synthetic urine and struvite precipitation that will feed into the other tasks that focus more on designing and evaluating a larger-scale system. Task 2 will lead to the development of CAD drawings and a cost-benefit analysis for a pilot-scale system that could be built and operated at a single restroom scale. Task 3 will focus on the operational aspects of the pilot-scale system and will provide valuable data that can be used for later projects and collaborations with commercialization partners to devise experiments with real urine. Finally, Task 4 will lead to comprehensive data on the environmental benefits of our proposed approach and implementation scenarios that can be made possible through economic benefits. A successful development, design, and demonstration project as proposed here would provide a necessary incentive to focus more on source-separation systems in new infrastructure, whether in the rural U.S. or the urban areas, as technological solutions such as what we propose here lead to pollution prevention, as well as energy and resource recovery benefits to the U.S.

Supplemental Keywords:

wastewater, nutrients, pollution prevention, waste reduction, waste minimization, technology, physics, engineering, innovative, water, agriculture