Energy and Carbon Balance in Wastewater Treatment Plants

Abstract

This dissertation explores energy balances and GHG emissions in WWTP, focusing on estimating the latter and understanding the roles both variables play in advancing decarbonisation and energy neutrality efforts. The primary objectives are to evaluate the applicability of existing GHG quantification tools for WWTP, equipping utilities with the means to assess their own CF, identify GHG emission hotspots, and implement targeted reduction strategies. Additionally, this research establishes a national baseline for Portuguese wastewater services, analysing energy consumption and autonomy and GHG emissions using data from a representative sample of bulk and retail operators. To achieve these goals, two tools (ECAM and the Svenskt Vatten's tool) were applied to two case studies (Serzedelo II and Quinta da Bomba), with national baseline values also quantified using the selected tools' methodologies. Key findings suggest that, while these tools may not provide exact values, they are effective in estimating the relative contributions of different activities to the overall CF of a plant. The study highlights the need to deepen understanding of GHG emissions in Portuguese wastewater services and their connection to energy consumption and self-sufficiency. By offering insights into GHG estimation and energy management, this research provides a foundation for regulators and stakeholders to make informed decisions, supporting a more sustainable future for WWTP. Ultimately, it sets the stage for a standardised national approach to the assessment of the climate impact of these utilities, fostering accountability and proactive GHG management.