Urban Wastewater Mapping Using Sentinel-2 Data

Wastewater treatment plants (WWTPs) account for roughly 1–2% of global greenhouse gas emissions. During the treatment process, gases such as carbon dioxide (CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>), methane (CH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>), and nitrous oxide (N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O) are emitted into the atmosphere. This issue becomes particularly concerning for WWTPs situated in urban areas, where high population densities result in large volumes of wastewater that must be treated daily. The increased load can overwhelm treatment capacities, leading to inefficiencies in pollutant removal. This study highlights the enhanced usefulness of the Sentinel-2 (S2) data for mapping wastewater in urban WWTPs and monitoring their discharge into surrounding water bodies. Specifically, the proposed method relies on adapted algorithms designed to address the reflectance spectrum, considering atmospheric interactions. In comparison to the matched filtering results, derived from the classification of the same image using the extracted reflectance spectrum, the method has demonstrated its effectiveness in monitoring and analyzing the spatial distribution and flow of wastewater. This approach is a crucial step in understanding and addressing environmental risks, especially in densely populated urban areas where WWTPs are vital for wastewater management and ecosystem protection.