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Do stressed septic systems mar our environment?

New study investigates heavy rains, increased use with potential negative impacts

 

The year began with record-breaking rainfall across Georgia, followed by a pandemic forcing millions to work and learn in their homes.

For residents with septic systems, it was a lot to process. Literally.

Now, a new study by a researcher at the University of Georgia Warnell School of Forestry and Natural Resources aims to uncover just how much stress excess rain and an increase in home water use has on septic systems. Rebecca Abney, an assistant professor of forest and disturbed soils, aims to understand how increased use changed the chemistry of the surrounding soil and water leaching from the system.

“The big issues are phosphorous leaching out, and sometimes nitrogen. So, that can be a source of runoff and pollution, which is really bad for aquatic systems,” says Abney. “More than 20% of the United States is on a septic system, and globally it’s bigger. So, it’s potentially a huge source of pollution that we’re not accounting for.”

In a septic system, water drains into a tank buried in the ground. Its job is to hold solids long enough to settle to the bottom, forming a sludge, while oil and grease float to the top. Its design keeps the solids and scum in the tank, but it allows the liquid wastewater to drain into a nearby drainfield in the soil. The soil naturally treats and disperses wastewater, removing harmful bacteria, and ultimately the water percolates down to groundwater.

But when the drainfield is saturated by rain, or more water is discharged from the home, that’s when problems potentially bubble up.

“We want to know how the increase in water use is changing the soil chemistry and the water in your soil, and could that lead to increased pollutant runoff?” says Abney. “It can also lead to changes in septic system functioning, which could lead to failure and bigger changes in the soil composure in the septic leach field.”

For her study, Abney is installing sampling equipment called a lysimeter, which resembles a small pole sticking out of the ground, in two places in subjects’ yards. One is installed in the leachfield and one outside it. Water samples will be taken regularly, as well as separate soil samples to be analyzed for their content.

Abney has recruited participants for the first round of the study and is now looking for homeowners to participate in the second round. The study pays to have participants’ septic tanks pumped; masks and social distancing will be observed throughout participants’ time in the study. For more information and to apply to be a study participant, visit https://forms.gle/gjVq93n3xxqGCtCy5.

The study is funded by the National Science Foundation under its Rapid Response Research grant program.

“The plan is to have the septic tank pumped in the middle of the study and see if it changes the soil water quality,” she adds. “We’re looking at changes and functioning of the system—how is this increased stress changing the chemistry of the soil and the soil water that’s leaching out of the system.”

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