Pine bark–modified purification material in the treatment units, i.e., columns. A column is like an industrial coffee filter, in which pine bark efficiently removes pharmaceutical residues from wastewater. Credit: Mahdiyeh Mohammadzadeh / University of Oulu

Researchers at the University of Oulu, Finland, have developed a pine-bark–based water-treatment medium that efficiently removes antibiotics as well as residues of blood-pressure and antidepressant medicines from wastewater treatment plant effluent. A new doctoral thesis reports promising results with a simple and low-cost method in which pine bark was modified with iron.

Pharmaceuticals enter wastewater from human use, hospitals and industry. Wastewater treatment plants purify municipal and industrial effluents and discharge treated water to receiving waters. However, current methods do not remove all pharmaceuticals, and the compounds reaching the environment can accelerate antibiotic resistance. The EU’s updated Urban Wastewater Directive (2024) calls for more effective removal of micropollutants, which requires new solutions and investments.

"Our results offer a concrete, circular-economy-based option to this challenge," says University of Oulu Doctoral Researcher Mahdiyeh Mohammadzadeh. She conducted trials at Oulu’s Taskila wastewater treatment plant in the post-treatment effluent, where pharmaceutical residues are low yet environmentally meaningful. The dissertation and defense on January 23, 2026, at 12 noon, are available online.

Pine bark contains abundant polyphenolic compounds that enable modification of the material. When modified with magnetite (iron oxide), the material is easy to separate after treatment. Using the modified pine bark and combination materials, the research removed antibiotics (such as trimethoprim), antidepressants (venlafaxine), painkillers (ketoprofen), blood-pressure medicines (losartan) and other commonly used pharmaceuticals.

Magnetite-modified pine bark is easy to separate from wastewater. Credit: Mahdiyeh Mohammadzadeh / University of Oulu

In a four-month pilot, removal efficiencies were typically in the tens of percent and, depending on the compound, exceeded 90% at best; for example, trimethoprim ~99.7% and venlafaxine ~93.7%. The work also developed cobalt–magnetite bionanocomposites that, for example, effectively degraded the antibiotic levofloxacin.

While activated carbon or ozonation can be very effective, pine bark is clearly more affordable. "Its wide availability as a side stream of the forest industry in the boreal forest zone supports sustainable use," Mohammadzadeh notes. "I hope wastewater treatment plants and the forest sector will explore collaboration opportunities."

Professor at Chemical Process Engineering Unit and thesis supervisor Tiina Leiviskä considers the piloting results encouraging. "Producing a solid purification medium from pine bark is cost-effective because high temperatures are not required and the modification is simple. The material can also be used to remove other contaminants."

Mohammadzadeh also highlights everyday practices: "Everyone has the opportunity to influence the state of the environment. At home, never flush antibiotics into the sewer or throw them into mixed waste. In Finland, unused medicines can be returned to a pharmacy."

At the University of Oulu, researchers are also studying other natural materials such as spruce bark tannins, from which materials have been developed to remove turbidity from industrial wastewater.

Citation: Pine bark removes pharmaceutical residues from wastewater—an affordable way to keep antibiotics out of nature (2026, January 21) retrieved 21 January 2026 from https://phys.org/news/2026-01-bark-pharmaceutical-residues-wastewater-antibiotics.html

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