PFAS TREATMENT OF CHEMICAL FIRE RUNOFF WATER

Abstract

To avoid costly transport and disposal of Polyfluoroalkyl Substances (PFAS) runoff water from a chemical plant fire by deep well injection or incineration, on-site pre-treatment and final treatment by the Publicly Owned Treatment Works (POTW) was evaluated as a disposal option for the impacted water.

Remtech conducted pilot treatability tests on 440,000 gallons of fire runoff water that was contained in twenty-two frac tanks from a chemical plant fire that was extinguished with (AFFF) foam. Samples were collected and independent treatment efficacy laboratory (Eurofins) analysis reported by Keith Cole, Ramboll Americas Engineering Solutions, Inc.1,2 Pilot tests and design specifications were prepared by Mark Ryckman, Remtech Engineers.3 PFAS concentrations ranged from 253,649 ng/l to 13,185,500 ng/l in six of the 22 frac tanks. Waste from all 22 tanks were equalized/blended to reduce the wide range of concentrations and treated through a pilot treatment train consisting of screening, equalization, sedimentation, fine bubble aeration, sand filtration, and three-stage liquid Granular Activated Carbon Filtration (GAC).

By aeration 27.97% of PFAS was removed, and 99.99% were removed by all unit operations. The treatment method demonstrated that both long and short chain PFAS analytes were effectively removed. Powdered Activated Carbon (PAC) dosed at a self-flocculating 1,000 mg/l concentration was considered as a treatment option that removed 34.50% of PFAS following 48 hours of clarification. This treatment method was ruled out. To reduce the laboratory testing frequencies and costs, correlation curves with a field COD meter (REALTECH BOD/COD Field Meter) were developed with laboratory data to predict PFAS concentrations approaching EPA target PFAS treatment values.

Background

Remtech developed a mobile treatment system design to treat runoff water from a chemical plant fire that had total PFAS concentrations ranging from 253,649 ng/l to 13,185,500 ng/l in 6 of 22 frac tanks. Household products, fragrances, sports drinks, tapes, and road-paving materials were manufactured from processed pine tree stumps into resins, rosins, waxes, and gums at the treatment plant. To avoid costly transport and disposal of the wastewater, on-site pre-treatment and final treatment by the Publicly Owned Treatment Works (POTW) was assessed as an option for the impacted water. Pilot/bench-scale tests were evaluated to properly design a full-scale wastewater treatment system.4

PFAS Waste Characterization & Preparation

Initial samples were collected from six (6) of the 22 frac tanks and tested for PFAS (using EPA Method 533) and general chemistry analytes. The results are presented in Tables 1a and 1b. Herbicides, heavy metals, mercury, and organochlorine pesticides were also tested on the initial 6 frac tank samples. These analytes were below pretreatment requirements of the Publicly Owned Treatment Works (POTW) and were not run on Pilot Runs 1 and 2. EPA methods employed for PFAS and General Chemistry analyses are summarized below:

     ✦ pH - Method:  (SM-4500-+)

     ✦ VOCs - Method:  8260D GC/MS

     ✦ Organochlorine Pesticides - Method: SW846 8081B

     ✦ Herbicides - Method: SW846 8151A (GC)

     ✦ Metals (ICP) - Total Recoverable - Method: EPA 200.7

     ✦ Total Hardness (as CaCO3) - Method: SM 2340B-2011

     ✦ Mercury (CVAA) - Method: EPA 245.1-1994 R3.0

     ✦ Oil & Grease - HEM (1664A)

     ✦ Total Suspended Solids - (SM 2540D-2015)

     ✦ Chemical Oxygen Demand (SM 5220D-2011)

     ✦ Total Organic Carbon TOC (SM 5310 B-2011)

     ✦ PFAS - EPA Method 533 was used for first 6 frac tanks

     ✦ PFAS - EPA Method 1633 was used for pilot testing. 5

The frac tanks contained a floating layer of resins/oils, a suspension of suspended solids, and settled solids. Samples from individual frac tanks had highly variable pHs (ranging from 4.25 to 11.96), general chemistry analytes and PFAS concentrations that required equalization. Results of initial testing are presented in Tables 1a & 1b.

Due to the wide variation of analyte concentrations, one-gallon samples from all 22 frac tanks were collected and a 22-gallon equalized composite sample was prepared for pilot testing. This resulted in significantly lower analyte concentrations. The “Raw Equalized” sample is depicted in the “blue highlighted” portions of Tables 1a & 1b and Table 2. The equalized raw wastewater had a pH of 10.1