Grantee Research Project Results

Electro-Assisted Wastewater Nutrient Recovery

EPA Grant Number: SV840417
Title: Electro-Assisted Wastewater Nutrient Recovery
Investigators: Tarpeh, William A , Dong, Hang , Kogler, Anna , Clark, Brandon , Chow, William
Current Investigators: Tarpeh, William A , Dong, Hang , Kogler, Anna , Clark, Brandon , Chow, William , Apraku, Edward
Institution: Stanford University
EPA Project Officer: Page, Angela
Phase: II
Project Period: February 1, 2023 through January 31, 2025
Project Amount: $100,000
RFA: 17th Annual P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2022) Recipients Lists
Research Category: P3 Awards

Description:

Nitrogen (N) and phosphorus (P) are critical elements for human society and environmental ecosystems. Both elements exist in multiple forms as pollutants in some settings and valuable products in others. Anthropogenic influences on the N and P cycles have led to harmful algal blooms, unsustainable energy consumption, and runaway greenhouse gas emissions. Meanwhile, both N and P are essential macronutrients in fertilizers that are currently obtained via energy-intensive N-fixation (Haber-Bosch process that consumes ~ 1% global energy to convert N₂ to NH₃) and unsustainable P mining. Agricultural fertilizer runoff discharges excessive N and P into aquatic systems, causing harmful algal blooms. The primary technical challenge we address is engineering selective separations to capture and recover dilute N and P from polluted waters (wastewater plant effluent and impaired surface waters). We address this technical challenge with selective adsorbents because they can capture dilute pollutants and are amenable to regeneration that replaces chemical inputs with electricity to recover nutrients on site, particularly in remote, rural, and disadvantaged communities. In addition to advancing recovery technologies, we plan to leverage this project as an educational tool by involving undergraduate researchers in laboratory investigations, undergraduate students in classroom demonstrations, and the broader public (with an emphasis on underrepresented minority audiences) in field-scale validation and facility tours. Integrating our research, education, and outreach efforts will inspire future environmental researchers; enhance classroom education with real-world exposure to wastewater treatment; and enhance sustainability awareness among diverse stakeholders.

Approach:

The overarching goal of the proposed work is to develop and demonstrate a self-sustaining selective nutrient capture and recovery unit. Conventional nutrient removal techniques (e.g., biological oxidation, membranes) accomplish desalination or removal of dissolved carbon and nitrogen, but their limited selectivity reduces recovered product purity. We expand on these approaches with selective recovery techniques that maximize economic value by recovering nutrients as pure products. To achieve this goal, we aim to develop selective adsorbents for removal and recovery of N and P. Commercial P-selective adsorbents already exist; we supplement them with novel N-selective materials. After adsorbent exhaustion, regeneration is required to elute the captured nutrients for recovery. Existing regeneration methods require strong acid, base, or brine that are energy-intensive, hazardous, and challenging to transport. To achieve self-sustaining operation, we develop and demonstrate an electro-assisted regeneration approach to replace chemical inputs with electricity to extract value-added products on site, particularly in remote, rural, and disadvantaged communities. The objectives of this proposal in Phase I were: (O1) to design and demonstrate deployable, durable, and selective nano-adsorbents; (O2) to develop a novel on-site electrochemical regeneration and recovery process for the nano-adsorbents to enable pure fertilizer production with minimal chemical inputs and transportation; and (O3) to validate field performance of electro-assisted nutrient recovery at the pilot scale. Our proposed research synergistically combines molecular level design, lab-scale development, and field demonstration to advance people, prosperity, and the planet.

Expected Results:

In Phase I, we developed and demonstrated a N-selective adsorbent using transition metal-loaded polymeric cation exchange resins (O1); achieved electro-assisted regeneration for P-selective adsorbents and established proof-of-concept for electro-regenerating the new N-selective adsorbent (O2); and validated the adsorbent and electro-assisted regeneration in a scaled-up system using real wastewater from Codiga Resource Recovery Center (CR2C, O3). The Phase I progress has demonstrated the feasibility of N and P recovery using selective adsorbents and electro-assisted regeneration, which laid the foundation to advance them into a mature technology in Phase II. The overarching goal of our proposed work in Phase II is to advance the nutrient-selective adsorbent and the electro-assisted regeneration (developed in Phase I) into an intensified self-sustaining device for nutrient capture and recovery. We concentrate on process intensification, or combining multiple unit processes to minimize inputs and emissions, to further advance our mission of realizing resource-efficient water treatment that benefits people, prosperity, and the planet.

Publications and Presentations:

Publications have been submitted on this project: View all 3 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

Selective separation, N-selective adsrobent, electro-assisted regeneration, nutrient recovery

Progress and Final Reports:

2023 Progress Report

Final

P3 Phase I:

Electro-Assisted Wastewater Nutrient Recovery  | Final Report