Introduction
The EPA's proposed Sixth Contaminant Candidate List (CCL 6) represents a watershed moment in drinking water regulation. For the first time, microplastics — along with several pharmaceutical compounds and other emerging contaminants — have been placed squarely in the regulatory pipeline. While enforceable Maximum Contaminant Levels (MCLs) for microplastics are likely five to ten years away, the inclusion on CCL 6 sends an unmistakable signal: utilities that begin preparing their monitoring infrastructure now will have significant advantages when compliance deadlines arrive.
The CCL process follows a well-established trajectory. After listing, EPA conducts regulatory determinations to decide whether national primary drinking water regulations are warranted. If a determination is positive, the agency moves through proposed rulemaking, public comment, and final rule publication. Utilities that already have baseline monitoring data, proven analytical methods, and operational familiarity with the required instrumentation will be far better positioned than those scrambling to build capacity under deadline pressure.
What Are Microplastics and Why Do They Matter?
Microplastics are synthetic polymer particles smaller than 5 millimeters in diameter. They originate from the degradation of larger plastic products, industrial processes, synthetic textiles, tire wear, and personal care products. Research has detected microplastics in virtually every freshwater source tested, including treated drinking water.
The health implications of microplastic ingestion are still being studied, but growing evidence suggests potential concerns related to chemical leaching from polymer additives, physical irritation of gastrointestinal tissues, and the capacity of microplastic particles to serve as vectors for other contaminants including heavy metals, pesticides, and pathogenic bacteria. These concerns are driving regulatory attention worldwide, with the European Union, Canada, and several US states already advancing monitoring frameworks.
For Mid-Atlantic utilities drawing from the Delaware River, Schuylkill River, Chesapeake Bay tributaries, and other surface water sources, microplastics contamination is particularly relevant given the density of urban and industrial land use in these watersheds.
The CCL 6 Regulatory Pathway
Understanding the regulatory timeline helps utilities plan their instrumentation investments appropriately. The CCL listing triggers a structured process. EPA will evaluate available occurrence data, health effects research, and analytical method capabilities. If the agency determines that regulation is warranted — meaning the contaminant may have adverse health effects, is known or substantially likely to occur in public water systems, and regulation presents a meaningful opportunity to reduce risk — rulemaking begins.
Historical precedents suggest this process takes 8-15 years from CCL listing to enforceable MCL. However, several factors may accelerate the timeline for microplastics, including intense public and Congressional interest, advancing analytical methods, and growing international regulatory momentum. Utilities should plan for the possibility that monitoring requirements — even if not tied to enforceable MCLs — could emerge within 3-5 years through unregulated contaminant monitoring rules or state-level initiatives.
Current Monitoring Technologies and Analytical Methods
Microplastics monitoring in drinking water requires a multi-step analytical process that combines sample collection, particle isolation, identification, and quantification.
Filtration-based sampling is the foundation. Water samples are passed through cascading filters — typically stainless steel mesh sieves — to isolate particles by size fraction. The most commonly used size cutoffs are 1 micrometer, 10 micrometers, and 100 micrometers. Sample volumes range from 100 liters to 1,000 liters depending on expected particle density and analytical sensitivity requirements.
Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy are the primary identification methods. FTIR microscopy can identify polymer type for particles as small as 10-20 micrometers by matching their infrared absorption spectra against reference libraries. Raman spectroscopy achieves even finer resolution, identifying particles down to 1 micrometer. Both methods can distinguish between polymer types — polyethylene, polypropylene, polystyrene, PET, nylon, and others — providing compositional data that regulators will likely require.
For utilities considering early adoption, several key instrumentation decisions must be addressed. Sampling infrastructure needs include dedicated sample taps at source water intake, post-treatment, and distribution system locations. Filtration and preparation equipment must handle the volumes required for statistically meaningful results. Analytical instruments — whether owned or accessed through laboratory partnerships — need to meet emerging method specifications.
Surrogate Monitoring Strategies
While direct microplastics analysis requires specialized equipment and expertise, several readily deployable surrogate monitoring approaches can provide valuable operational data. Particle counters installed at key treatment stages — raw water intake, post-coagulation, post-filtration, and finished water — can track total particle removal efficiency across size ranges that overlap with microplastics. Online turbidity analyzers with enhanced sensitivity can serve as continuous indicators of treatment barrier performance.
Membrane integrity monitoring for utilities using microfiltration or ultrafiltration provides direct evidence of barrier effectiveness against particles in the microplastics size range. Pressure decay tests, diffusive airflow tests, and online particle counting downstream of membrane systems all contribute to a comprehensive removal verification strategy.
These surrogate approaches generate data that demonstrates treatment effectiveness against microplastics-sized particles, even before specific microplastics regulations are finalized. This data will be valuable for regulatory compliance demonstrations, public communication, and capital planning.
How Emergent Energy Can Help
At Emergent Energy, we help utilities prepare for emerging contaminant monitoring requirements through a phased, practical approach. Our services include assessment of existing treatment barriers and monitoring infrastructure for microplastics removal capability, specification and installation of particle counters, turbidity analyzers, and membrane integrity monitoring equipment at strategic process points, SCADA integration for continuous data collection and trend analysis, and coordination with analytical laboratories for baseline microplastics sampling campaigns.
We work with utilities to build monitoring capacity incrementally — starting with surrogate measurements that provide immediate operational value and progressing to direct analytical capabilities as methods standardize and regulatory requirements crystallize. As a COSTARS contract holder, we can streamline procurement for Pennsylvania public water systems investing in emerging contaminant readiness.
Contact our team at 215-645-7141 or visit emergentenergy.us/contact to discuss how your utility can begin preparing for microplastics and emerging contaminant monitoring requirements.