Wastewater treatment plants continually encounter new challenges, such as enhancing effluent quality, meeting discharge standards, and optimizing energy consumption, operating costs, and minimizing greenhouse gas emissions.
In her doctoral thesis, Tuğba Sapmaz Wikström explored the production of volatile fatty acids (VFAs) from organic waste, such as pulp from paper mills or sewage sludge, using membrane bioreactors. The studies have shown promising results on how VFAs, mainly acetic acid, butyric acid and propionic acid, can serve as a more environmentally and economically sustainable carbon source for denitrification. Denitrification is a crucial process aimed at purifying wastewater from nitrate, as an excess of nitrate in water bodies can lead to eutrophication, algae growth, and oxygen depletion for other organisms.

“It was genuinely exciting to see that waste-derived VFAs could offer a sustainable solution against the most used carbon source: fossil-derived methanol or expensive ethanol. This was great news to address the challenges of carbon source provision in nitrogen removal within wastewater treatment plants anywhere in the world that used biological nitrogen removal process,” said Tuğba Sapmaz Wikström.

In her studies, she also identified methods such as ion exchange and nanofiltration—techniques used in water treatment—to purify and enhance the carbon content in waste-derived VFAs. This, in turn, can further improve their performance in nitrogen removal.

Caffeine and late nights in the lab

What has it been like to pursue a doctorate? Tuğba humorously describes the time as a vortex of caffeine, late nights in the lab, and existential crises. However, she adds more seriously that there were many moments of joy when the work flowed smoothly, and the puzzle pieces began to fall into place. 

“It has been a wild journey, but I wouldn’t want to exchange it for anything else. Working on a topic with the potential to address pressing issues like the carbon footprint in wastewater treatment, particularly regarding one of the major contributors of greenhouse gas emissions – fossil derived chemical consumption with a replacement of waste-derived volatile fatty acids, has been motivating and has fueled my passion for research and innovation”, concludes Tuğba Sapmaz Wikström. 

Tuğba Sapmaz Wikström conducted her dissertation work as part of the project Sustainable biorefineries by developing VFA platform. On 15 March, she defended her thesis titled “Unlocking Sustainability in Wastewater Denitrification through Waste-Derived Volatile Fatty Acids” and receives a double-degree from both University of Borås and Istanbul Technical University (ITU). Her supervisors were Mohammad Taherzadeh, co-supervisor Amir Mahboubi Soufiani, University of Borås, and co-supervisor Derya Yuksel Imer, ITU.

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Tuğba Sapmaz Wikström researcher profile page

The doctoral thesis Unlocking Sustainability in Wastewater Denitrification through Waste-Derived Volatile Fatty Acids

The project Sustainable biorefineries by developing VFA platform

More research from the Swedish Centre for Resource Recovery