Unlocking sustainability in wastewater denitrification through waste-derived volatile fatty acids

Abstract

In the studies performed, the effectiveness of food waste-derived VFAs (AD-VFA) was investigated in the post-denitrification process in comparison with synthetic VFA and methanol as carbon sources. Acetic acid had the highest rate of disappearance among single tested VFAs with a denitrification rate of 0.44 g NOx-N removed/m2/day, indicating a preferential utilization pattern. While AD-VFA had a denitrification rate of 0.61 mg NOx-N removed/m2/day, sVFA had a rate of 0.57 mg NOx-N removed/m2/day, indicating that impurities in AD-VFA did not play substantial role in denitrification. AD-VFA proved to be promising carbon source alternative for denitrification in wastewater treatment plants. In the continuation study, although solely added AD-VFAPPL as a carbon source had a slower denitrification capability (0.56 ± 0.13 mg NOx-N removed/m2/day) than methanol (1.04 ± 0.46 mg NOx-N removed/m2/day), up to 50% of the methanol can be replaced by waste-derived AD- VFAPPL and achieve comparable performance (1.08 ± 0.07 mg NOx-N removed/m2/day) with the pure methanol. This proves that the co-addition of VFAs together with methanol can fully compete with pure methanol in performance. This integration emerges as a sustainable approach, attaining parallel denitrification performance while reducing reliance on fossil-derived sources. This proves that the co-addition of VFAs together with methanol can fully compete with pure methanol in performance, providing a promising opportunity for wastewater treatment plants to potentially reduce their carbon footprint and become more sustainable in practice while benefiting from recovered nutrients from waste. xxi In conclusion, this thesis reimagines WWTPs as places that recover valuable resources, going beyond only wastewater treatment. Bridging VFA generation with value-added usage holds the potential to strengthen biorefineries and promote environmentally friendly wastewater solutions.