Michigan PFAS MCL Compliance Treatment Decision Guide

Why this matters

Michigan enacted some of the strictest PFAS drinking water standards in the country in August 2020, codified at Mich. Admin. Code R 325.10604f. The state set Maximum Contaminant Levels (MCLs) for seven PFAS compounds, lower than the EPA's 2024 federal MCL for several. Residential and small-system water treatment contractors in Michigan have to know which compounds trigger which limits, which point-of-use (POU) and point-of-entry (POE) technologies are NSF/ANSI 53 or 58 certified for PFAS reduction, and the documentation EGLE expects when a homeowner installs a treatment system in response to a positive test. This guide is the field reference for Michigan residential PFAS treatment.

The Michigan MCLs

Mich. Admin. Code R 325.10604f sets these MCLs (effective August 2020):

ppt = parts per trillion (nanograms per liter).

For Michigan systems, both the state and federal MCL apply where federal is more stringent (PFOA, PFOS, PFHxS, GenX as of 2024). The 2024 EPA Hazard Index for the four short-chain PFAS (PFHxS, PFNA, GenX, PFBS) also applies.

Who must comply

The MCLs apply to all Community Water Supplies and Nontransient Noncommunity Water Supplies. Private residential wells (single-family, no public service) are not subject to the MCL but are subject to:

• Mandatory disclosure on real-estate transfer if a known contamination plume is on file (per the EGLE PFAS-impacted sites database).
• Health advisory levels through the Michigan Department of Health and Human Services if a positive test results.

For a residential well-water contractor, the practical rule is: treat to or below the MCL even though the homeowner is not legally required to, because that is the only defensible level if a future buyer tests the well.

Approved testing methodology

Only EPA Method 537.1, 533, or 1633 results are recognized by EGLE for compliance purposes. The lab must be Michigan-accredited under the Drinking Water Laboratory Certification Program. Samples must be collected per the lab's chain-of-custody protocol, typically in 250 mL HDPE bottles with no preservative for non-public-water tests.

Field collection notes:

• No PTFE-lined sample bottle caps (PFAS contamination of the sample).
• No sample collection while wearing GoreTex outerwear, anti-perspirant, or sunscreen (all common PFAS sources).
• Cold-side tap, flushed 5 minutes minimum.
• Lab turnaround typically 10-15 business days.

Treatment technologies certified for PFAS

Two NSF/ANSI standards address PFAS reduction:

• NSF/ANSI 53-2023 - PFOA and PFOS reduction certification for filtration systems (activated carbon, ion exchange).
• NSF/ANSI 58-2023 - Reverse osmosis system certification, with optional PFOA/PFOS reduction claim.

Always check the specific compound list on the system's certification page (typically at the NSF Listings website by manufacturer / model). A system certified for "PFOA / PFOS reduction" does NOT necessarily reduce GenX, PFNA, or other short-chain compounds. For the broader Michigan compound list, look for NSF/ANSI 53 certifications with the "Total PFAS" claim or NSF/ANSI 58 with extended PFAS testing.

POU vs POE - the cost-versus-coverage choice

Point-of-Use (POU)

• Under-sink RO system (NSF/ANSI 58 certified for PFAS): treats the kitchen tap and refrigerator water dispenser.
• Carbon filter on the kitchen tap (NSF/ANSI 53 certified): less effective on RO-rejecting compounds but easier maintenance.
• Practical install: $400-$1500 hardware, 50-100 gallons per day treated.

POU does not treat shower, bath, laundry, or outside-tap water. For Michigan's chronic-exposure focus, the primary route of ingestion exposure is the kitchen tap, so POU at the sink covers the highest-risk use.

Point-of-Entry (POE)

• Whole-house granular activated carbon (GAC) tank, dual-stage if needed for high contamination.
• Whole-house ion exchange (anion resin) for short-chain PFAS that GAC handles poorly.
• Practical install: $3000-$10000 hardware, treats every fixture.

POE is the right answer when:

• The PFAS concentration is well above the MCL (state-confirmed plume sites in the I-69 corridor, Wurtsmith, Wolverine Worldwide).
• The homeowner has dermal-exposure concern (children bathing, pregnancy).
• A real-estate transfer is pending and the buyer requires whole-house remediation.

Combined GAC + anion exchange treatment train

For high-contamination sites in Michigan, the recommended residential POE configuration is:

1. Sediment pre-filter (5 micron) to protect downstream media.
2. GAC tank (1.5-2.0 cubic ft virgin coconut shell or coal-based GAC, like Calgon F600 or Norit GAC 1240). GAC reduces long-chain PFAS (PFOA, PFOS, PFNA) reliably.
3. Anion exchange (AIX) tank (Purolite PFA694E or similar PFAS-selective resin). AIX captures short-chain PFAS (PFBS, PFHxA, GenX) that GAC breaks through quickly.
4. Polish stage - second GAC tank as backup.
5. Annual sampling to confirm breakthrough has not occurred.

Media exhaustion: GAC for residential POE typically lasts 12-36 months depending on PFAS load and feed flow. AIX may last 24-60 months. Replacement is the contractor's responsibility under most service contracts; spent media disposal must follow Michigan PFAS waste guidance (treat as universal waste; do not landfill without confirmation of acceptance).

Documentation EGLE expects

For a non-public residential install in an EGLE-identified plume area, document:

• Pre-treatment sample result (EPA 537.1 or 533).
• System make, model, and NSF/ANSI 53 or 58 listing with PFAS certification.
• Installation date.
• Post-installation sample confirming treated water is below the MCL.
• Annual sampling and media replacement log.

Homeowners in plume areas may qualify for state-funded treatment under the EGLE PFAS Action Response program; the contractor's documentation packet is part of the reimbursement file.

References

• Michigan Administrative Code R 325.10604f - Maximum Contaminant Levels for PFAS
• Michigan Drinking Water Laboratory Certification Program, EGLE 2024 Manual
• US EPA 40 CFR Part 141 - 2024 PFAS National Primary Drinking Water Regulation
• NSF/ANSI 53-2023 - Drinking Water Treatment Units - Health Effects
• NSF/ANSI 58-2023 - Reverse Osmosis Drinking Water Treatment Systems
• EPA Method 537.1 Rev 2.0 (2020) - Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography / Tandem Mass Spectrometry
• WQA PFAS Treatment Technical Application Bulletin (2024)