Life Cycle Assessment of Municipal Wastewater Treatment Processes Regarding Energy Production from the Sludge Line

Abstract

The efficient and timely removal of organic matter and nutrients from water used in normal municipal functions is considered to be the main task of wastewater treatment plants (WWTPs). Therefore, these facilities are considered to be essential units that are required to avoid pollution of the water environment and decrease the possibility of triggering eutrophication. Even though these benefits are undeniable, they remain at odds with the high energy demand of wastewater treatment and sludge processes. As a consequence, WWTPs have various environmental impacts, which can be estimated and categorized using Life Cycle Assessment (LCA) analysis. In this study, a municipal WWTP based in Poznań, Poland, was examined using the method defined in ISO 14040. ReCiPe Endpoint and Midpoint (v1.11), in a hierarchical approach, were used to evaluate the environmental impacts regarding 18 different categories. All calculations were conducted using a detailed database from 2019, which describes each chosen facility. It was found that the energy component, related to the wastewater treatment process demand and electricity production, is the main determinant of the sum of the environmental impact indicators in light of the modelled energy mix. Therefore, it determines the entire process as an environmentally friendly activity.

What can we learn from decarbonization of the energy sector?

“…It is likely that additional GHG emissions are attributable to the water and wastewater treatment sector from onsite natural gas combustion, however no data could be found to quantify this emissions source. Offsite manufacturing of chemicals used for water and wastewater treatment have also been hypothesized to contribute significantly to the sector's life cycle GHG footprint, but estimates of this quantity in the literature vary widely (Kyung et al, 2015;Szulc et al, 2021). Combustion of fossil fuel across the entire energy sector in the US emits 5300 MMT of CO 2 .…”

Beyond the Black Box of Life Cycle Assessment in the Wastewater Treatment Plants: Which Help from the Bioassays?

“…Within the field of wastewater treatment plants (WWTPs), the PEF/OEF can be leveraged to identify the best alternatives to adopt in an upgrade scenario or to establish the best operation decision from an environmental footprint standpoint. Furthermore, this methodology can be applied to estimate the overall environmental impact in terms of both direct impacts and indirect impacts [10][11][12][13][14][15][16][17][18][19][20][21][22]. The direct impacts are linked to effluents and other emissions, whereas the indirect impacts are linked to energy and resources consumed.…”

Life Cycle Assessment (LCA) of the Use of Metallurgical Process Gas for Heat and Electricity, Combined with Salt Removal from Discarded Water

“…Life Cycle Assessment analysis is used in many similar projects, which were considered by [12,13]. The authors of the study [13] developed an environmental analysis of the operating treatment plant using ReCiPe, which allowed them to identify points that can be improved in the technology.…”

“…Life Cycle Assessment analysis is used in many similar projects, which were considered by [12,13]. The authors of the study [13] developed an environmental analysis of the operating treatment plant using ReCiPe, which allowed them to identify points that can be improved in the technology. Skoczko et al [14] compared two wastewater treatment technologies in analogous industrial plants, thanks to which a more advantageous solution was specified.…”

“…It can also be added that not only renewable sources can be a source of electricity, but also thanks to the single use of various possibilities, it is possible to reduce the negative environmental impact of the coal sector, which is the basic source of energy in Poland. Research on the assessment of technological solutions increasing energy efficiency in sewage treatment plants was carried out, among others, by [12][13][14]. The results allowed for the selection of the optimal solution, or the identification of weak points in the technology.…”