Grantee Research Project Results

2024 Progress Report: Three-way removal of per- and polyfluoroalkyl substances from high-strength landfill leachate utilizing simultaneous foaming and humic acid precipitation during pH adjustment

EPA Grant Number: SU840582
Title: Three-way removal of per- and polyfluoroalkyl substances from high-strength landfill leachate utilizing simultaneous foaming and humic acid precipitation during pH adjustment
Investigators: Iskander, Syeed Md , Saha, Biraj , Yadav, Himani , Khan, Md Tanbir
Institution: North Dakota State University Main Campus
EPA Project Officer: Ludwig-Monty, Sarah
Phase: I
Project Period: August 1, 2023 through July 31, 2025
Project Period Covered by this Report: August 1, 2023 through July 31,2024
Project Amount: $24,982
RFA: 19th Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet Request for Applications (RFA) (2022) RFA Text |  Recipients Lists
Research Category: Urban Air Toxics , Heavy Metal Contamination of Soil/Water , P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources

Objective:

The objectives of this project are to:

Objective 1. Evaluate the effect of simple pH adjustment on PFAS removal due to humic acid precipitation and foaming at low pH, 

Objective 2. Evaluate the performance of a membrane electrochemical reactor to remove PFAS in precipitated humic acid and foam at low pH in the anode chamber

Objective 3. Evaluate preliminary treatments of coalesced foam, humic acids, and the remaining fraction of leachate for PFAS destruction.

Progress Summary:

PFAS are among the most concerning contaminants in landfill leachate, and their treatment is challenging due to the complex matrix effect of the leachate. In this study, we leveraged the surfactant properties of PFAS to separate them into foam using a membrane electrochemical reactor (MER). The MER was designed with a cation exchange membrane placed between the anode and cathode compartments, each containing a platinum-coated titanium electrode. The anode chamber held 500 mL of leachate (pH = 6.2, COD = 16.2 g L⁻¹), while the cathode chamber contained 350 mL of 100 mM NaCl solution. At a current density of 0.01 A cm⁻², the leachate pH decreased from 6.2 to 2.0 within 7 hours. Foam was generated at low pH due to the conversion of bicarbonate species to carbon dioxide within the leachate. After 7 hours, only 21% of the total PFAS remained in the defoamed leachate, indicating that the majority of PFAS were effectively isolated in the foam. Specifically, short-chain PFAS (C≤6), such as 43% PFBA, 71% PFPeA, 80% PFHxA, and 51% PFBS, migrated into the foam after MER treatment. For comparison, we investigated a simple pH adjustment technique to fractionate PFAS into foam and settled solids. This technique effectively separated PFAS, capturing 67% in the settled solid and 19% in the foam. The addition of 0.1 M sodium bicarbonate during pH adjustment increased foam volume, leading to a 43% separation of PFAS into the foam. The separation of PFAS with solids was likely due to the complexation of PFAS with leachate humic acids, which precipitate at low pH. The results of this study suggest that fractionating PFAS into foam and settled solids may offer a practical approach that could be strategically combined with high-energy PFAS-destructive treatment technologies. 

Future Activities:

The study shows that simple pH adjustment effectively separates 86% of total PFAS from landfill leachate, with 67% captured in settled solids and 19% in foam. Adding 0.1 M NaHCO₃ before pH adjustment improved PFAS separation in foam to 43%. With only 14% of PFAS remaining in the defoamed leachate, this method demonstrates a practical and efficient approach for PFAS removal. 

This study also demonstrates the effectiveness of the membrane electrochemical reactor in isolating PFAS into foam under low pH conditions, resulting in a significant reduction of PFAS concentrations in the leachate. After 7 hours of treatment, 81.7% of the total PFAS were successfully removed from the leachate and captured in the foam, highlighting the reactor's potential for efficient PFAS separation in foam. 

Future research should investigate leachate's chemical properties—particularly ionic concentrations and the degree of humification—that affect PFAS removal in different fractions. Dissolved ions in leachate can stabilize foam, promoting PFAS capture and removal during foaming. Meanwhile, humic acid complexes with PFAS, ensuring removal by precipitation at low pH (~2.0). A deeper understanding of these factors will be critical to optimizing PFAS treatment in an MER.

The MER system needs to be demonstrated in pilot-scale and a detailed technoeconomic analysis needs to be conducted to facilitate the real-world application for leachate PFAS management. 

Removing PFAS from leachate helps reduce pollutant loads in water bodies, lowers healthcare expenses tied to PFAS-related conditions, and opens revenue opportunities by recovering ammonia for fertilizer. These outcomes will directly bolster economic prosperity by improving water treatment efficiency and supporting agricultural productivity. Safer water fosters healthier communities, enhances environmental justice by alleviating pollution burdens on vulnerable groups, and preserves local ecosystems. Altogether, these achievements embody a holistic commitment to people, prosperity, and the planet.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this project

Supplemental Keywords:

Leachate concentrate, Forever chemicals, Recalcitrant organics, Thermal destruction, Surfactant property

Progress and Final Reports:

Original Abstract

Final