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Emerging Contaminants and Your Onsite Wastewater Treatment System

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When installed, operated, and maintained correctly, septic systems should not pollute groundwater or cause any danger to the drinking water supply. But the unfortunate fact is that pollutants and contaminants do make their way out of septic systems and into groundwater all the same. And this isn’t always to do with poor installation or maintenance — if a septic owner is putting things down their toilets and drains that aren’t meant to be treated by a septic system, these things become all the more likely to get into the groundwater. This is one of the reasons why making sure everyone knows the Three Ps of septic systems is so important! (That’s pee, poop, and toilet paper, of course).

A 2017 study in the journal Environmental Science & Technology showed that American septic systems are regularly depositing pharmaceuticals, consumer product chemicals, and other hazardous chemicals into the environment. Due to their presence in consumer and industrial products throughout society, such chemicals — often called contaminants of emerging concern or emerging contaminants — find their way into bodies and supplies of water in numerous ways, not just through septic systems. They can not only threaten public health by contaminating a human drinking water supply, but cause environmental problems for ecosystems and organisms as well. For instance, the feminization of male fish and fertility issues in other animals have been strongly linked to emerging contaminants.

This 2017 study suggests that besides emphasizing the need to avoid putting pollutants into a septic system, the best way to protect groundwater from septic contamination is keeping septic systems away from the aquifers and wells that supply drinking water. But, of course, many septic systems already exist in such a range and other solutions for preventing them from discharging too many emerging contaminants are needed.

While any chemical going into a septic system that isn’t one of the Three Ps is a contamination risk and absolutely should not enter a septic tank, some chemicals or contaminants will naturally be more of a cause for alarm than others. Right now, the pollutants society is likely most concerned about at large are PFAS compounds and microplastics, both of which have been found coming out of septic systems.

Though PFAS (Per- and polyfluoroalkyl substances, also commonly known as forever chemicals) have become a high-profile concern in more recent years, PFAS have been one of the most frequently detected compounds in drinking water wells since at least 2016, contamination which has been linked to septic systems.  

For more information on protecting groundwater from failing septic systems and forever chemicals, check out this article on the subject from SCS Engineers.

As for microplastics, the impossibly tiny bits of degraded plastic have been found everywhere from clouds to likely into human brains, and some believe septic tanks are the primary source of microplastics found in underwater drinking water reservoirs. The issue of microplastics in its totality certainly cannot primarily be blamed on septic systems, but figuring out how to decrease their presence in as many sources as possible is critical.

Another consideration with microplastics in septic systems isn’t just the environmental contamination — the buildup of solids in the system can also cause issues for the operation of the system. In fact, a 2015 Pumper Magazine article refers to microplastics as “tiny terrorists” in septic systems.

More to the point, microplastics are a type of solid that “remain[s] suspended are small rough to move readily through the screen and into the soil treatment area. If these solids are small pieces of organic material, they will break down or be consumed in the soil. However, if they are inert particles such as … plastics or other synthetic materials, they will not break down in the soil environment and will plug the soil pores, permanently reducing the ability of the soil to accept septic tank effluent. There is no fix when this happens other than replacement.”

Solutions to protect septic systems and the groundwater reservoirs they feed into from microplastics are hard to come by, short of emphasizing to septic owners the necessity of keeping everything but the Three Ps out of their systems and that they should try to buy fewer products containing microplastics to begin with.

PFAS Treatment: What We Know in 2023

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PFAS (formally known as per- and polyfluoroalkyl substances) are widely used, long lasting chemicals that break down very slowly over time. They break down so slowly that they end up in water, air, fish, and soil all over the world, and trace amounts have even been detected in human blood. Scientific studies have shown that exposure to some PFAS in the environment may be linked to harmful health effects in humans and animals, but we do not know to what extent they may affect us.

PFAS possess chemical properties that mean traditional drinking water treatment technologies are not able to remove them. Researchers have been working on a variety of treatment technologies to determine which methods work best to remove PFAS from drinking water. Some of the most successful methods include: activated carbon adsorption, ion exchange resins, and high-pressure membranes. 

Granular activated carbon (GAC) adsorption: GAC has been shown to effectively remove PFAS from drinking water when it is used in a flow through filter mode after particulates have already been removed. According to EPA researcher Thomas Speth, this method can be extremely effective “depending on the type of carbon used, the depth of the bed of carbon, flow rate of the water, the specific PFAS you need to remove, temperature, and the degree and type of organic matter as well as other contaminants, or constituents, in the water.”

Ion exchange resins: Negatively charged ions of PFAS are attracted to positively charged anion resins. Anion exchange resins (AER) have proved to have a high capacity for many PFAS; but this method can be more expensive than GAC. The most promising version of this method is an AER in a single use mode, followed by incineration of the resin. This technology has no contaminant waste stream to treat or dispose due to the lack of need for resin regeneration.

High-pressure membranes: Research shows that membranes, such as nanofiltration or reverse osmosis, are typically more than 90 percent effective at removing a wide range of PFAS. However, these methods generate a large volume of high-strength waste stream which can be difficult to treat or dispose of for a water system. This technology may be better suited for a homeowner since it would generate a much smaller volume of waste.

PFAS Resources:

  • Drinking Water Treatability Database
    • The Drinking Water Treatability Database (TDB) can be used to identify effective drinking water treatment processes, to plan for future treatment plant upgrades, to provide information to first responders for spills/ emergencies, and to recognize research needs.
  • PFAS Analytic Tools hub
    • This page contains location-specific information related to PFAS manufacture, release, and occurrence in the environment as well as facilities potentially handling PFAS.
  • CWA Analytical Methods for Per- and Polyfluorinated Alkyl Substances (PFAS)
    • This page contains information regarding the EPA’s development of new analytical methods to test for PFAS compounds in wastewater, as well as other environmental media.

Free PFAS Resources for Drinking Water and Wastewater Operators


Per- and polyfluoroalkyl substances, also known as PFAS, have garnered a great deal of attention over the past decade. In 2016 the U.S. EPA established a health advisory level of 70 parts per trillion for combined PFOA and PFOS. Listed below are a collection of free resources on PFAS contamination in drinking water and wastewater facility and what can be done about it. 

PFAS Factsheet

NACWA, 2019

The is a 4-page factsheet that provides background information on per- and polyfluoroalkyl substances (PFAS), their prevalence, human health impacts, and how water and wastewater utilities are impacted by receiving PFAS contamination.

Laboratory Testing Guidelines for Per- and Polyfluoroalkyl Substances (PFAS) for Public Drinking Water Supplies

NH Department of Environmental Services, 2020

This is a 6-page factsheet that provides the recommended guidelines for testing for PFAS in water samples collected from private wells or public water systems. 

Mapping Guide for Per- and Polyfluoroalkyl Substances (PFAS) Source Water Assessments

ASDWA, 2020

The is a 23-page manual that guides utilities in the development of a source water assessment (SWA) to evaluate the susceptibility of drinking water to PFAS contamination through GIS data. The guide includes a description of potential data sources for your assessment.

Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water; Health Issues

Michigan Department of Environment, Great Lakes, and Energy, 2019

This is a 2-page document that provides an overview of the health issues with PFAS, the Lifetime Health Advisory (LHA) level, and what is being done about it.

Perfluoroalkyl Substances (PFAS) and Health

Minnesota Department of Health, 2021

This is a 4-page factsheet that provides an overview of information on Perfluoroalkyl Substances (PFAS) in drinking water, with an emphasis on topics related to Minnesota. 

PFAS Action Plan
Iowa Department of Natural Resources, 2020

This is a 12-page document that outlines the initial steps the DNR will be taking to determine the extent of PFAS contamination in the state of Iowa. 

2021 DW Workshop Session 2b – Source and Treatment I: Per-and Polyfluoroalkyl Substances (PFAS)

U.S. EPA, 2021

This is a 2-hour recording is from the 18th Annual EPA Drinking Water Workshop that provides in-depth information and training on solutions and strategies for handling small drinking water system challenges with a focus on monitoring, distribution, source, and treatment topics related to PFAS. 

2019 State of the Water Industry Report

AWWA, 2019

This is a 51-page full report from the American Water Works Association on the 2019 State of the Water Industry details optimism in the industry and pressing issues that water systems across North America are concerned about. 

A Clean Water Utility's Guide to Considering Source Identification, Pretreatment, and Sampling Protocols for PFAS
NACWA, 2019
The is a 12-page guide from the National Association of Clean Water Agencies that outlines source identification and pretreatment considerations for per- and polyfluoroalkyl substances (PFAS) in wastewater. The guide includes sampling plans and protocols to reference while the EPA continues to evaluate PFAS.

Communicating with Industry on PFAS Contamination
ASDWA, 2020
This 4-page factsheet describes the toxicology of per- and polyfluoroalkyl substance (PFAS) chemicals and their history in industrial manufacturing.

PFAS – Background and Updates for the Water Industry
Robinson & Cole LLP, 2018
This is a 31-slide presentation, presented during CWWA's 2019 Fall Conference, which provides introductory information on what PFAS is, sources of PFAS, the health effects due to PFAS exposure, the challenges laboratories face with PFAS analysis, and currently used methods to remove PFAS.

EPA Tools and Resources Webinar: Treating Contaminants of Emerging Concern
U.S. EPA, 2019 
This is a webinar on treatment technologies for three contaminants of emerging concern (CECs)- PFAS, cyanotoxins, and perchlorate- with an emphasis on determining cost-effective solutions for small systems. 

Proactive Treatment Solutions for PFAS Groundwater Contamination
Jacobs, 2019
This is a 27- slide presentation from May 2019 that explains PFAS chemicals are, where they are found, their health concerns, current regulations, and sampling and detection methods.