Grantee Research Project Results

Final Report: Removal of PFAS chemicals from Wastewater and Sewage using Novel Hydrothermal Liquefaction Process

EPA Contract Number: 68HERC24C0012
Title: Removal of PFAS chemicals from Wastewater and Sewage using Novel Hydrothermal Liquefaction Process
Investigators: Thomas, Amelia
Small Business: River Otter Renewables, Inc
EPA Contact: Richards, April
Phase: I
Project Period: November 1, 2023 through May 30, 2024
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2024) RFA Text |  Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , PFAS Treatment , Water Treatment

Description:

Per- and polyfluoroalkyl substances (PFAS), known as 'forever chemicals' due to their extreme resistance to natural degradation, are increasingly regulated in wastewater and sewage sludges. PFAS chemicals can accumulate in soil and contaminate water systems when sludge is used as fertilizer on farms or after sludge deposition in landfills. PFAS chemicals can transfer to crops, livestock, and subsequently into the human food chain, raising the risks of potential health impacts such as cancer, cardiac, and liver disease.

This phase I SBIR proposal aimed to demonstrate a novel River Otter waste-to-fuel technology, Radical Initiated Hydrothermal Liquefaction (RI-HTL) as an effective PFAS destructive technology during conversion of sewage sludge into biocrude, a precursor to renewable transportation fuels, such as diesel or sustainable aviation fuel. The goals of this phase I SBIR project were to validate initial PFAS removal data from sewage sludge using RI-HTL, optimize the RI-HTL process for PFAS removal with sustained biocrude oil yield, and design a concept model continuous flow reactor for RI-HTL use at scale.

Summary/Accomplishments (Outputs/Outcomes):

This phase I SBIR research confirmed initial data for PFAS destruction from sewage sludge during the RI-HTL process using Pace Analytics, an independent commercial laboratory. This data supported the superiority of RI-HTL over HTL for reduction in PFAS diversity and PFAS removal from our two most essential target products, the process water (aqueous phase) and the solid waste (char). These two substrates demonstrated greater than 99% removal of PFAS. The process water data reported non-detectable (ND) levels of 39 out of 40 PFAS chemicals as quantified by US EPA Method 1633.

Process optimization exploring different reaction times and temperatures for the RI-HTL protocol identified a time and temperature sweet spot for over 99% PFAS removal efficiency from process water in as little as ten (10) minutes. Multiple sewage lots were tested validating RI-HTL robustness. A preliminary concept design for an RI-HTL continuous flow reactor was created, analyzed for risks by a world-renowned design firm, and updated based on the provided risk assessment for future feasibility studies.

Conclusions:

This phase I SBIR research verified initial data for PFAS destruction from sewage sludge using River Otter’s novel radical-initiated hydrothermal liquefaction (RI-HTL) process. RI-HTL resulted in over 99% removal of PFAS chemicals from process water and char, the most important impacts for our wastewater treatment facility customers. Process optimization demonstrated a powerful PFAS removal and biocrude yield increase with a shortened reaction time of only 10 minutes.

We believe this data supports the submission of a phase II SBIR application to the EPA to further develop the RI-HTL process. In our phase II study, we intend to further define our key operational parameters for a commercial system in terms of process heating rate and temperature as well as reaction time to determine if time periods below 10 minutes are viable for PFAS destruction during biocrude production.

The water and wastewater treatment industry, currently valued at $340 billion, is projected to grow to over $536 billion by 2030. (statista.com) With landfills nearing capacity and sludge land application restrictions increasing due to PFAS contamination, alternative methods are needed to manage the over 3 million dry metric tons of domestic sludge produced annually. (EPA.gov/biosolids) The RI-HTL process, pioneered by Worcester Polytechnic Institute (WPI) and licensed to River Otter, stands out as a promising solution for renewable fuel generation, waste recycling, and PFAS remediation.

The River Otter initiative could be a game-changer in managing sewage sludge and tackling PFAS pollution by turning waste into renewable energy. The RI-HTL process promises substantial savings for wastewater treatment plants by cutting down on the need for natural gas, electricity, and chemicals typically used in sludge drying. This method stands out against current PFAS disposal techniques, such as incineration or gasification, which require substantial sludge drying.

We offer a compelling advantage by combining PFAS remediation with energy generation. The RI-HTL process not only disposes of PFAS-contaminated sludge waste, it creates renewable fuel like renewable diesel and sustainable aviation fuel. These alternatives to fossil fuels aim to serve major fuel consumers, including trucking, shipping, and airlines. With River Otter’s novel technology, fuel production could occur wherever people produce waste, breaking free from the constraints of natural oil reserves and providing new avenues of energy independence.