Study Finds Soil May Filter Antibiotics From Treated Wastewater

A new study from researchers at Penn State, published in the journal Environmental Quality, found that soil may be a natural filter that can act as a tertiary treatment for wastewater, preventing antibiotics and other emerging contaminants from damaging groundwater. The researchers investigated the infiltration of three antibiotics–sulfamethoxazole, ofloxacin and trimethoprim–in soil and groundwater on a test area known as the Living Filter. The Living Filter is a 50-year-old wastewater reuse system that uses treated effluent to irrigate farm and forest land surround Penn State, according to a news release by Penn State.

In the study, researchers collected soil samples from the Living Filter that had not received irrigation for seven months and then compared it to different period of irrigation exposure with treated effluent and groundwater samples. Overall, the team found that while ofloxacin remained in the soil for long periods of time, sulfamethoxazole and trimethoprim may not remain after effluent irrigation ends.

“Given that antibiotics interacted with the soil profile and groundwater concentrations were frequently more than a 1,000-fold lower than effluent, the soil profile appears to be an adequate tertiary treatment for wastewater treatment plant effluent,” said Lead Researcher Alison Franklin. “That would lead to improved water quality and protection of human health.”

The study suggests that soil may be a cost-effective way for wastewater treatment plants to meet a rising demand to treat emerging contaminants and antibiotics that are difficult to remove. While treatment effectiveness may vary based on soil quality and type, the findings point to soil infiltration as a potential low-cost solution.

“There is a lot of research looking at what can be done at wastewater treatment plants to improve their capabilities to remove emerging contaminant, but the solutions are expensive to implement and may be under 100% effective,” Franklin said. “So, our work suggest that, especially with water shortages, we could reuse water and purify it as it goes down into the soil profile before it reaches the groundwater system.”