Biosolids Corner For Keystone Water Quality Manager April May June 2023 Issue                                                    By Diane Garvey and Lynne Reamer

What you need to know before monitoring for PFAS in biosolids.

At this writing, EPA Method 1633 is going through multi-lab validation. It was expected to be finalized by the end of 2022. That date was moved back to spring 2023 and postponed again to late 2023. Maybe multi-lab validation is not going so well?

At a November 2022 Webinar hosted by the Virginia Biosolids Council there was a presentation by the Loudoun County Sanitation Authority, DBA Loudoun Water. They monitored biosolids using the draft EPA Method 1633. One single biosolids composite sample was split and sent to 3 different labs for analysis of PFAS. The results varied wildly.

An erroneous result, showing a high concentration could be a burden on a utility for years.

Until this method is finalized, it is not recommended to test for PFAS in biosolids. Oh, and by the way, the labs were so backlogged that it took over 6 months to get the results.

One Lab that is PADEP accredited to test for PFOA in non-potable water was sending out sampling supplies to WRRFs that wanted to test, however, they supplied no sampling instructions. Sampling methodology is extremely important in the accuracy of the results because PFAS are in so many products and we are testing to such low levels that it would be easy to contaminate a sample.

Synopsis of Guidance for Sampling Biosolids for PFAS Analysis

Source; Michigan Department of Environment, Great Lakes, and Energy (EGLE)

This sampling guidance covers the collection of biosolids and sludge PFAS samples and contains

methods to prevent cross-contamination that can occur from:

• Field clothing and personal protective equipment

• Personal care products

• Food packaging

• Sampling equipment

• Equipment decontamination

• Sample collection and handling

• Sample shipment


Personal Care Products (PCP):
It is recommended that personal hygiene and PCPs (e.g., cosmetics, shampoo and other hair products, sunscreens, dental floss, etc.) not be used prior to and on the day(s) of sampling because the presence of PFAS in these products has been documented.

  • Do not handle or apply PCPs in the sampling area.
  • Do not handle or apply PCPs while wearing Personal Protective Equipment (PPE) that will be present during sampling.
  • If it is necessary to apply a PCP, move to the staging area and remove PPE if applying PCPs becomes necessary. Wash hands thoroughly after the handling or application of PCPs and, when finished, put on a fresh pair of powderless nitrile gloves.

Food Packaging:
Prewrapped food or snacks (such as candy bars, microwave popcorn, etc.) must not be in the sampling and staging area during sampling due to PFAS contamination of the packaging. When staff requires a break to eat or drink, they should remove their gloves, coveralls, and any other PPE, if worn, in the staging area and move to the designated area for food and beverage consumption. When finished, staff should wash their hands and put on a fresh pair of powderless nitrile gloves at the staging area before returning to the sampling area.

  • Do not handle, consume, or otherwise interact with prewrapped food or snacks, carry-out food, fast food, or other food items while on site during sampling.

Sampling Equipment:
Any item that will directly contact the biosolids and/or sludge, including various biosolids or sludge samplers (such as trowels and spoons), bowls, tubing, sample bottles, etc. These items should be known to be PFAS-free prior to use.

Any item that will not directly contact biosolids or sludge, including Global Positioning System receivers, notebooks, and clipboards. Every effort should be made to ensure these items are PFAS-free. Be aware, the surface of some of this field equipment or the containers in which they are kept may contain PFAS. Care should be taken to prevent cross-contamination in these cases.

  • As of this writing do not use items that contain PTFE (trademarks Teflon® and Hostaflon®), PVDF (trademark Kynar®),  PCTFE (trademark Neoflon®), FEP (trademarks Teflon® FEP, Hostaflon® FEP, and Neoflon® FEP), and ETFE. These items are frequently found in hose and pipelining; tubing; cables and wires; and films/coatings on aluminum, galvanized steel, aluminized steel, valves, seals, and gaskets
  • Do not use low-density polyethylene (LDPE) for any items that will come into direct contact with the sample media. LDPE can be found in many items, such as plastic bags, tubing, and containers, including some sample bottles
  • Items containing LDPE (e.g., Ziploc® storage bags) that do not come into direct contact with the sample media and do not introduce cross-contamination with samples may be used
  • Use materials that are either made of high-density polyethylene (HDPE), stainless steel, polypropylene, silicone, or acetate
  • Store tubing, dippers, or trowels in a clean location free of dust and fibers

Sampling Equipment:

  • Stainless steel trowels and spoons, as well as glass, HDPE, or stainless-steel bowls, could be used to collect and homogenize biosolids samples

Equipment Decontamination:
Field sampling equipment used at multiple sites or sampling locations can become highly contaminated with PFAS. Decontamination procedures should be implemented to prevent cross contamination, especially between individual sample locations. For items that will come into direct contact with the sample

  • Do not use Decon® 90.
  • Laboratory supplied PFAS-free deionized water is preferred for decontamination.
  • Alconox®, Liquinox®, and Citranox® may be used for equipment decontamination.
  • Sampling equipment can be scrubbed using a polyethylene or PVC brush to remove


  • Decontamination procedures should include triple rinsing with PFAS-free water.
  • Commercially available deionized water in an HDPE container may be used for decontamination purposes if the water and container are known to be PFAS-free.
  • Municipal drinking water may be used for decontamination purposes if it is known to be PFAS free.
  • Do not put equipment away without decontaminating it.
  • Decontaminate sampling equipment after sampling at each location and at the end of the workday.

Sample Collection and Handling:

  • Dust and fibers must be kept out of sample bottles.
  • The sample cap should never be placed directly on the ground during sampling. If sampling staff must set the sample bottle cap down during sample collection and a second member of the sampling crew (wearing a fresh pair of powderless nitrile gloves) is not available, set the cap on a clean surface (cotton sheeting, HDPE sheeting, triple rinsed cooler lid, etc.).
  • Do not sample without powderless nitrile gloves.
  • Regular/thick size markers (Sharpie® or otherwise) are to be avoided as they may contain PFAS. Fine and Ultra-Fine Point Sharpie® markers are acceptable for labels.
  • Ballpoint pens may be used when labeling sample containers. If ballpoint pens do not write on the sample container labels, preprinted labels from the laboratory may be used.
  • Hands should be well washed and gloved.
  • Use HDPE or polypropylene sample bottles with Teflon®-free caps, provided by the laboratory.
  • Commercially bought sample bottles used with automatic sampling equipment should be decontaminated prior to sampling and equipment blank samples should be collected using laboratory provided PFAS-free water.
  • Bottles should only be opened immediately prior to sampling.
  • Bottles should be capped immediately after collecting the sample.
  • Samples should be double-bagged using LDPE (e.g., Ziploc® storage bags) resealable storage bags.
  • In the absence of a United States Environmental Protection Agency (USEPA) approved method, staff should contact the laboratory performing the sample analysis to obtain values for thermal preservation and holding time consistent with the analytical method to be used. At a minimum, samples should be placed on ice within 15 minutes of collection and chilled to a temperature of ≤42.8°F (6°C). This temperature should be maintained during collection and through transit to the laboratory.
  • Glass bottles or containers may be used if they are known to be PFAS-free; however, PFAS has been found to adsorb to glass, especially when the sample is in contact with the glass for a long period of time (e.g., being stored in a glass container). If the sample comes into direct contact with the glass for a short period of time (e.g., using a glass container to collect the sample and then transferring the sample to a non-glass sample bottle), the adsorption is minimal.
  • If the site-specific information is available, sampling should be conducted from the least to the most contaminated location.
  • Powderless nitrile gloves should be changed any time there is an opportunity for cross contamination during sampling.


Sample Preparation, Analytical Methods, and Reporting:
Draft EPA Method 1633 is currently undergoing multi-laboratory validation as part of the Clean Water Act (CWA) method approval process. When a final PFAS analytical method for wastewater is published in 40 CFR Part 136, this method will be required for sampling conducted under the CWA, including National Pollutant Discharge Elimination (NPDES) permits. Until EPA Method 1633 is approved, an isotope dilution method (sometimes referred to as Method 537 modified) or ASTM Method D7968 may be used.

All biosolids and sludge samples, including those with low solids content, should be analyzed as solids and must be reported on a dry weight basis. The dry weight analysis (i.e., moisture content) must be performed on the samples as received, not on centrifuged solids when centrifugation is performed. The entire sample is recommended to be extracted and analyzed, even if the solids are separated by centrifugation as part of the sample preparation. Sufficient sample mass should be extracted to achieve a reporting limit of 2 µg/kg (ppb) or less for PFOS. Also, the percent solids should be determined and reported on the as received biosolids.

Sample Shipment:

  • Regular ice should be used to cool and maintain the sample at or below 42.8°F (6°C).
  • Chemical or blue ice may be used if it is known to be PFAS-free and it is absolutely certain that the sample is cooled and maintained at or below 42.8°F (6°C) during collection and through transit to the laboratory.
  • Check the cooler periodically to ensure samples are well iced and at the proper temperature.
  • Refresh with regular ice, if needed, double-bagged in LDPE (e.g., Ziploc® storage bags) resealable storage bags, if needed.
  • Chain of Custody and other forms should be single-bagged in LDPE (e.g., Ziploc® storage bags) resealable storage bags and taped to the inside of the cooler lid.
  • The cooler should be taped closed with a custody seal and shipped by overnight courier.
  • Samples should be shipped as soon as possible (e.g., overnight) to ensure the samples arrive within the analytical holding time specified by the lab.





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