Formatted Title
Removal of PFAS from Bilge and Oily Wastewater
Background/Objectives
At many maritime ports, current practices dictate that bilge and oily wastewaters transferred from vessels to collection barges need to be sampled for the presence of per- and polyfluoroalkyl substances (PFAS). Because the turn around time to analyze bilge and oily wastewater samples is up to 35 days, barges are placed offline, which disturbs normal operations at ports. Once the analytical results from samples come back, if they indicate the presence of PFAS such as perfluorooctane sulfonate (PFOS) and/or perfluorooctanoic acid (PFOA), treatment must be contracted for the treatment and/or disposal of bilge and oily wastewater and the decontamination of the barge. The latter actions result in considerable costs. Therefore, there is a critical need for prompt and cost-effective methodologies and technologies capable of detecting and treating PFAS in bilge and oily wastewater.
Approach/Activities
This project consists of two tasks. In Task 1 several bilge and oily wastewater samples will be collected and analyzed for PFAS after separation of the water and oil phases. In Task 2 water separated from the oil will be treated using an enhanced contact electrical discharge plasma reactor (ECo-PRe™). This plasma technology uses electricity to convert water into a mixture of highly reactive species (i.e., plasma) that rapidly and non-selectively degrade a broad spectrum of PFAS including PFOA, PFOS, and shorter-chain PFAS. The plasma reactor can simultaneously oxidize and reduce organics by producing a mixture of OH radicals and aqueous electrons, the latter of which act as strong reducing agents and are the key species in removing PFAS and other non-oxidizable compounds. Additionally, the plasma process requires no chemical additions and produces no residual waste, although in some applications surfactants are added to enhance short and ultrashort chain removal. The ECo-PRe™ uses multipoint high voltage electrodes for the generation of plasma. Gas diffusers are positioned on the bottom of the reactor and argon gas is continuously pumped through the diffusers producing bubbles and forming a layer of foam on the liquid surface. This foam concentrates PFAS and enhances the contact between the liquid and the plasma, exposing the PFAS at the interface to reactive species in the plasma.
Results/Lessons Learned
All of the bilge and oily wastewater samples contained significant amounts of PFAS in both the oil and water phases. The concentration of EPA Method 1633 PFAS in the water phase varied between 0.4 and 3.9 µg/L and in the oil phase between 0.34 and 18.4 µg/L. On average 60% of the PFAS were in the oil phase, although in one sample 75% of the PFAS were in the water phase. In the majority of the samples PFOS had the highest concentration (0.042 to 0.41 in water and 0.061 to 11.6 µg/L in the oil phase). Of the Method 1633 precursors only 6:2 FTS was found in every sample. PFPeA was the most commonly found short-chain compound (BDL to 0.083 in water and 0.006 to 0.011 µg/L in the oil phase). Laboratory based plasma treatment is currently underway and a field deployment is planned for Spring 2024. An overview of the bilge and oily wastewater characterization, plasma technology and results from the bench scale and field campaigns will be discussed in this presentation.