CALCULATION OF GREENHOUSE GAS EMISSIONS FROM BIOLOGICAL WASTEWATER TREATMENT FACILITIES OPERATING UNDER THE AO SCHEME

Biological wastewater treatment at municipal wastewater treatment plants (WWTPs) is essential for protecting environmental and public health. However, these processes also generate greenhouse gas (GHG) emissions, particularly carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Globally, water supply and sanitation systems account for about 2.8% of total GHG emissions, underscoring their importance in climate mitigation efforts. In Ukraine, outdated treatment technologies aggravate the problem: around 99% of WWTPs lack effective nitrogen removal, leading to elevated N₂O emissions — a gas with a global warming potential nearly 300 times higher than CO₂. Additionally, insufficient treatment may result in excess pollutants in effluents, contributing to secondary GHG emissions in receiving waters — a factor often underestimated due to limited data. This study quantitatively assesses CO₂ and N₂O emissions from a full-scale municipal WWTP in Germany operating with an anaerobic-oxidative (AO) biological treatment configuration. Objectives include evaluating removal efficiencies for organic matter and nitrogen compounds, calculating GHG emissions during treatment and post-discharge phases, and comparing the results with those from a conventional non-zoned WWTP in Lviv, Ukraine. The AO system showed high removal efficiency for organic pollutants (96.5% COD, 98.8% BOD) and approximately 90% ammonia removal. However, total nitrogen removal was below 70%, indicating denitrification limitations. N₂O was the dominant climate-impacting gas, with CO₂-equivalent emissions from N₂O exceeding those of CO₂ by 1.5 times during treatment and nearly doubling after discharge due to elevated nitrate levels. Compared to the traditional plant, the AO-based WWTP demonstrated approximately 2.5 times lower GHG emissions during treatment and almost 350 times lower emissions after effluent discharge. These results highlight the potential of AO technology to significantly reduce GHG emissions and support the integration of advanced treatment configurations in WWTP modernization strategies for climate change mitigation and sustainable water resource management.