PFAS TREATABILITY, DESIGN & TREATMENT SYSTEMS

MOBILE PFAS TREATMENT SYSTEMS & OPERATION

Remtech Engineers specializes in the treatment of forever chemicals Polyfluoroalkyl Substances (PFAS) present in wastewater, stormwater, groundwater, landfill leachates, carpet manufacturer discharges, septic sludges and wastewater from other industrial sources. Determining PFAS treatment or disposal options requires Waste Characterization, Treatment Methods & Goals, State and Local Permits, Pilot Testing Demonstrating Treatment Efficacy, and Full-Scale Design - Deployment - Operation, and Discharge Efficacy Testing. One of the most economical disposal outlets is to pretreat wastewater that the local Publicly Owned Treatment Works (POTW) will accept which will be presented herein.

A PFAS CASE HISTORY TREATING 80,000 GALLONS OF FIRE FIGHTING RUNOFF WATER IS PRESENTED HERE.

A SECOND PFAS CASE HISTORY TREATING 440,000 GALLONS OF FIRE FIGHTING RUNOFF WATER IS PRESENTED HERE.

PFAS Waste Characterization & Preparation

To effectively treat contaminated liquid waste streams, the source and characterization must be known.  Representative samples need to be collected and analyzed for these parameters:

✦ pH - Method:  (SM-4500+)

✦ VOCs - Method:  8260D GC/MS

✦ Organochlorine Pest - SW846 8081B

✦ Herbicides - SW846 8151A (GC)

✦ Metals (ICP) - EPA 200.7 Rev 4.4  

✦ Total Hardness - SM 2340B-2011

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

✦ Oil & Grease - HEM (1664A)

✦ TSS - (SM 2540D-2015)

✦ COD (SM 5220D-2011)

✦ TOC (SM 5310 B-2011)

✦ PFAS - EPA Method 1633  

PFAS is commonly associated with AFFF foam (that fire departments are phasing out) from stormwater fire fighting runoff. Foam generation during treatment needs to be addressed.  Fire fighting runoff contains resins, solids, particulates, and volatile chemicals in elevated concentrations that need to be reduced prior to treating PFAS chemicals.  In addition, the disposal outlet needs to be identified whether it is a POTW, deep well injection, or incineration.  The concentration of PFAS chemicals present and permitted outlet acceptance concentrations (Treatment Goals) determines the potential treatment or disposal strategy.

PFAS Treatment Methods and Goals

Environmental releases from fires are known to produce toxic vapor clouds, contaminated runoff from firefighting operations, partially burnt chemicals and residues, heavy resins, and fire extinguishing agents. Past treatment unit operations used by Remtech on contaminated chemical plant fire runoff water included flow/concentration equalization, aeration, sedimentation, filtration, granular activated carbon (GAC) filtration, and sometimes powdered activated carbon (PAC) addition at self-flocculating dosages of 1,000 mg/l combined with bentonite.

Remtech’s treatment train design is based on the following documented PFAS treatability information:

▶︎ Complex organics, dissolved organic carbon (DOC), surfactants, suspended solids, TOC, and COD interfere with and compete for GAC and PAC absorption sites for PFAS and therefore, needs to be removed first

▶︎ Aeration/foam fractionation is an effective pretreatment to remove some PFAS analytes and to enhance post treatment with carbon or ion exchange filtration

▶ ︎Foam fractionation produces extremely high concentrations of toxic vapors mists that requires mist treatment

▶ Soluble PFAS analytes on particulates can be desorbed and transferred to the aqueous phase by aeration mixing for treatment

▶ ︎Particulate matter needs to be removed prior to filtration to reduce carbon column backwashing that decreases PFAS removal efficiencies by channeling of bed media

▶ ︎PFAS removal efficiencies may increase with decreasing pH in the 3 to 7 range

▶ ︎Aqueous and vapor phase coal-based GAC effectively removes PFAS and can be regenerated for reuse

Two of the preferred PFAS coal based GACs are Calgon F400M and General Carbon 12 X 40PF.  General Carbon GAC is used by Remtech since this vendor claimed that their product outperformed Calgon carbon for PFAS removal.

PFAS Permit Application and Approvals

Pilot tests are needed to confirm the treatment technology that will meet the acceptance criteria of the receiving facility. One of the most economical disposal outlets is to pretreat wastewater that the local POTW will accept.  The PFAS concentration acceptance criteria typically range from 200 ng/l to below detection limits. The results of pilot tests are submitted to State regulatory authorities and the local POTW to demonstrate the efficacy of the treatment process to be permitted and used. Permitting temporary mobile PFAS treatment systems as a Temporary Pilot Treatment Facility designed and operated under direct supervision of a Professional Engineer frequently eliminates the requirement of having a licensed wastewater treatment operator.

PFAS Pilot Plant Design & Setup

Pilot plant testing apparatus needs to be Teflon free to prevent introduction of PFAS analytes.The volume of wastewater for pilot tests needs to be determined and the sample volume required for testing selected analytes needs to be considered. A minimum of at least 50 gallons is generally required. Pilot scale reactor sizes for aeration, clarification, and filtration needs to be determined. If GAC is used carbon bed contact times range from 10 to 30 minutes with two to three columns in series. Carbon regeneration times also need to be determined. Regeneration of spend PFAS filtration media is still allowed by EPA and is an economically method of media recycling.

Design of Mobile or Full-Scale PFAS Treatment System

Pilot results are scaled up to determine the full-scale treatment system based on the volume of wastewater and treatment time.  The results from the Pilot Test(s) and Full-Scale design are submitted for approval by the local POTW and State permitting authorities. Approvals generally require a specified flowrate and time of operation to ensure efficacy of treatment.

PFAS Mobile or Full-Scale Treatment System Deployment and Operation

The full-scale system is setup and media is prepared and vessels hydrostatically tested. Initial treatment discharges are generally stored in a frac tank to confirm treatment efficacy to meet treatment goals.  Additional testing may be required during the treatment period.  Remtech has found that correlating COD lab data with a field COD testing meter can assist in determining trends in reducing PFAS concentrations to Treatment Goals to minimize lab testing costs and associated turn around times.