Emerging Contaminants and Your Onsite Wastewater Treatment System

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.