water Article Combining Process Modelling and LCA to Assess the Environmental Impacts of Wastewater Treatment Innovations Aleš Paulu 1, * , Jan Bartá ˇ cek 2 , Markéta Šerešová 1 and Vladimír Koˇ cí 1   Citation: Paulu, A.; Bartᡠcek, J.; Šerešová, M.; Koˇ cí, V. Combining Process Modelling and LCA to Assess the Environmental Impacts of Wastewater Treatment Innovations. Water 2021, 13, 1246. https:// doi.org/10.3390/w13091246 Academic Editors: Montse Meneses and Jorgelina Pasqualino Received: 3 April 2021 Accepted: 27 April 2021 Published: 29 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Environmental Chemistry, Faculty of Environmental Technology, University of Chemistry and Technology Prague, Technická 5, 160 00 Prague, Czech Republic; Marketa.Seresova@vscht.cz (M.Š.); Vlad.Koci@vscht.cz (V.K.) 2 Department of Water Technology and Environmental Engineering, Faculty of Environmental Technology, University of Chemistry and Technology Prague, Technická 5, 160 00 Prague, Czech Republic; jan.bartacek@vscht.cz * Correspondence: paulua@vscht.cz Abstract: Alternative wastewater treatment (WWT) technologies with lower environmental impacts seem to be the way forward in the pursuit of sustainable wastewater treatment plants (WWTPs). Process modelling of material and energy flows together with life-cycle assessment (LCA) can help to better understand these impacts and show the right direction for their development. Here, we apply this combined approach to three scenarios: conventional WWT; conventional WWT + chemically enhanced primary treatment (CEPT); conventional WWT + CEPT + side stream partial nitritation/anammox (PN/A). For each scenario, equations were developed to calculate chemical oxygen demand and nitrogen flow (solid and dissolved form) through the WWTP and to estimate the energy demands of its unit operations. LCA showed that the main environmental impact categories for all scenarios were global warming potential (GWP), eutrophication potential (EP) and marine aquatic eco-toxicity potential (MAETP). Compared with conventional WWT, CEPT and CEPT combined with PN/A resulted in a higher sum of normalized and weighed environmental indicators, by 19.5% and 16.4%, respectively (20.0% and 18.3% including biogenic carbon). Interestingly, the environmentally positive features of the alternative scenarios were often traded-off against other increased negative impacts. This suggests that further development is needed to consider these technologies a sustainable alternative. Keywords: life cycle; anammox; nitritation; CEPT; impact; trade-off 1. Introduction Sustainability, as a concept is the necessary response to today’s crises resulting from the current approach to continued economic growth. Good water quality is an integral part of the modern world and, for urban systems, wastewater treatment plants (WWTPs) are of vital significance [1,2]. Current methods of wastewater treatment (WWT) are very efficient in pollutant removal from sewage, thus generating water fit for reuse. However, WWT itself generates emissions and concentrates pollutants into sewage sludge, an unavoidable by-product [3]. Environmentally important are also the emissions of greenhouse gases (GHGs) that are produced both directly at WWTPs and indirectly during the production of energy needed to run the plant [4]. When developing new WWT technologies, in addition to process efficiency and economic benefits, the environmental performance of these technologies, i.e., the sum of all environmental impacts, must be considered to ensure the sustainability of these technologies in the future. To analyze environmental performance, it is necessary to choose a tool that can comprehensively describe all environmental impacts associated with the process, including all inputs and outputs. Life-cycle assessment (LCA) is such a tool, as it can assess the environmental impacts of processes, products and services throughout their Water 2021, 13, 1246. https://doi.org/10.3390/w13091246 https://www.mdpi.com/journal/water