With millions of people across the country under stay-at-home orders, home wastewater systems are getting more use.
For many Americans that means increased use of septic tanks. The number of homes with on-site sewage treatment has been rising in this country, raising concerns from some environmentalists.
Across the U.S., about 25% of people use septic tanks, says Sara Heger, a researcher at the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. The prevalence of septic tanks varies state to state, but homebuilders report that number is increasing, she says.
“We don't have fabulous data about this because the last time this question was really addressed nationwide was in the 1990 census,” she says. “They are planning to currently add that question back.”
More people are moving further away from cities into rural areas and deeper into suburbs that don't have the infrastructure for town sewage systems. Extending sewers into rural areas is expensive, Heger says.
A lot of people live within an hour of a large city and in many instances, there’s no way to affordably extend a wastewater treatment plant that far, she says. Plus, a lot of the land that could easily connect these residents to a plant has already been developed.
“Very often it's a less costly option to treat your wastewater closer to where you're collecting it,” she says.
Septic tanks create miniature wastewater plants in people’s backyards and the treatment is comparable, she says. But with a septic tank, the property owner is responsible for the cost and maintenance.
Many older septic systems aren’t up to today’s standards, Heger says. These legacy systems can impact surface waters, she says, or the top layer of a body of water.
In areas with freshwater, older systems leak phosphorus into lakes, rivers and streams, she says. For coastal regions, she says improper treatment of nitrogen from septic tanks can cause algal blooms. Wastewater systems have contributed to blooms on Lake Erie and in the Gulf of Mexico in recent years.
Different municipalities across the U.S. use varied methods of tracking home wastewater systems and management requirements, she says.
A septic system is comprised of a tank and a soil drain field that helps treat the wastewater, she says. These drain fields are designed above the water table, she says, which is the barrier between a soil surface and where groundwater saturates.
In different parts of the country, the groundwater can be shallow or deep. This makes septic systems vulnerable to sea-level rise, Heger says.
“We are designing our systems to be above even that shallow groundwater,” she says. “So if sea level rises and it impacts where groundwater is, that could negatively impact septic systems.”
Some areas of the U.S. are underserved on wastewater treatment like in the South and in Heger’s home state of Minnesota, which has progressive environmental regulations, she says.
Improperly treated sewage spreads sickness, she says, which has given the issue of wastewater treatment more recent attention.
“We still have communities and even individual homeowners that don't have appropriate wastewater treatment,” she says. “It's a very large public health issue. It's not just an environmental one.”
This segment aired on May 15, 2020.