Topic Area: 4b. Innovative Treatment Technologies for PFAS Ex Situ

Formatted Title:

PFAS Waste Concentration Followed by Destruction and Stabilization

Background/Objectives:

Landfill leachate has a very complex water chemistry and the characteristics of leachates vary significantly. Consequently, landfill leachate is one of the most challenging types of water to treat for per- and polyfluoroalkyl substances (PFAS). Foam fractionation (FF), which utilizes the ability of PFAS to form and partition to foam/bubbles, appears at present to be the most efficient technology to remove PFAS from landfill leachate. A comprehensive FF pilot study was conducted on landfill leachate to study PFAS removal efficiencies, ancillary air emissions, and foamate (waste concentrate) management strategy.

Approach/Activities:

The comprehensive pilot study consisted of multiple phases and steps to obtain the robust removal efficiency data and (to our knowledge) many first-of-its-kind measurements/results:

The first step was to obtain extensive PFAS and chemical profiling under different flow conditions, which were mainly affected by precipitation rates.
The FF pilot study was conducted in two phases. During the first phase, 12 different conditions (air/water ratios and residence times) and four surfactants were tested. PFAS profiling and chemical characterization included influent leachate, effluent after each of the three treatment stages, and primary foamate. Both 1633 and 8421 methods were applied to analyze PFAS. In addition, a first-of-its-kind of air monitoring was conducted to measure PFAS, volatile organic compound (VOC), odorous compounds (ammonia and sulfide), and greenhouse gases (GHG) during four tests. The sorption efficiency of activated carbon for different PFAS including fluorotelomer alcohols (FTOH) was measured. During the second phase, one condition that showed most optimal PFAS removal was selected for testing. The test generated sufficient primary foamate and then secondary foamate to allow various follow-up tests. The PFAS profiling, chemical characterizations, and air monitoring were undertaken during the primary and secondary foamate generation steps.
Stabilization testing of the secondary foamate was conducted using cementitious materials and various sorption media. Toxicity Characteristic Leaching Procedure (TCLP) was tested for all 14 test conditions (various dosages of cements and sorption media) and the four conditions that showed the most optimal results and reasonable reagent costs were selected for Leaching Environmental Assessment Framework (LEAF) 1315 testing.
Destructive testing of the waste concentrates (primary and secondary foamate) was explored via hydrothermal alkaline treatment (HALT) and electrooxidation (EO). The goal was not to achieve complete PFAS destruction, but rather to allow the treated concentrate to be cycled back to the influent of the FF system.

Ronald St. Michel

Affiliation

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(Group 1, Poster Board #15) PFAS Waste Concentration Followed by Destruction and Stabilization