Advanced wastewater treatment (AWT) technologies are now considered to target urban micropollutants (MPs) before discharge into receiving water bodies and to comply with specific criteria for reuse. Extra energy and/or resources are necessary to achieve the elimination of MPs. Using the Life Cycle Assessment framework, this study assesses net environmental efficiencies for two AWTs (i) ozone systems (air-fed and pure oxygen-fed) and (ii) granular activated carbon filter. Sixty-five MPs with proven removal efficiency values and toxicity and/or ecotoxicity potentials were included in this study building on results from recent research. Consolidated Life Cycle Inventories with data quality and uncertainty characterization were produced with an emphasis on operational inputs. Results show that the direct water quality benefits obtained from AWT are outweighed by greater increases in indirect impacts from energy and resource demands. Future research should include water quality aspects not currently captured in life cycle impact assessment, such as endocrine disruption and whole-effluent toxicity, in order to assess the complete policy implications of MP removal strategies.

Decentralised wastewater management (DWM) systems are deployed in areas where the topography does not allow for gravity flow to a centralised system, or requires a complex and expensive pumping station network. Also, DWM systems are often the only option in rural areas where there are no sewage transport networks. This paper aims at addressing the question of the degree to which DWM systems can be considered as viable alternatives from an environmental point of view using the Life Cycle Assessment (LCA) methodology. First, the environmental sustainability is investigated to identify environmental hotspots in two (nature-based and engineered) onsite DWM systems. Second, DWM scenarios are compared against centralised wastewater management (CWM) scenarios using a whole-systems approach. Finally the boundary conditions under which a given DWM scenario performs better than a CWM scenario are discussed. Results show CWM scenarios were less sustainable than DWM scenarios on the resources endpoint due to their sewer infrastructures, however CWM scenarios performed better than DWM scenarios on the ecosystems quality endpoint due to their well-managed air emissions and discharges. While on human health no clear conclusion could be drawn. Finally, for relatively few households (subject of the study in rural areas) CWM scenarios did not score superior performances compared to DWM scenarios on all three endpoint indicators. Yet for a greater number of households it was impossible to decide in favour of decentralisation because of a lack of favourable consensus on all three endpoint indicators.

Sewage systems are a vital part of the urban infrastructure in most cities. They provide drainage, which protects public health, prevents the flooding of property and protects the water environment around urban areas. On some occasions sewers will overflow into the water environment during heavy rain potentially causing unacceptable impacts from releases of untreated sewage into the environment. In typical Life Cycle Assessment (LCA) studies of urban wastewater systems (UWS), average dry-weather conditions are modelled while wet-weather flows from UWS, presenting a high temporal variability, are not currently accounted for. In this context, the loads from several storm events could be important contributors to the impact categories freshwater eutrophication and ecotoxicity. In this study we investigated the contributions of these wet-weather-induced discharges relative to average dry-weather conditions in the life cycle inventory for UWS. In collaboration with the Paris public sanitation service (SIAAP) and Observatory of Urban Pollutants (OPUR) program researchers, this work aimed at identifying and comparing contributing flows from the UWS in the Paris area by a selection of routine wastewater parameters and priority pollutants. This collected data is organized according to archetypal weather days during a reference year. Then, for each archetypal weather day and its associated flows to the receiving river waters (Seine), the parameters of pollutant loads (statistical distribution of concentrations and volumes) were determined. The resulting inventory flows (i.e. the potential loads from the UWS) were used as LCA input data to assess the associated impacts. This allowed investigating the relative importance of episodic wet-weather versus "continuous" dry-weather loads with a probabilistic approach to account for pollutant variability within the urban flows. The analysis at the scale of one year showed that storm events are significant contributors to the impacts of freshwater eutrophication and ecotoxicity compared to those arising from treated effluents. At the rain event scale the wet-weather contributions to these impacts are even more significant, accounting for example for up to 62% of the total impact on freshwater ecotoxicity. This also allowed investigating and discussing the ecotoxicity contribution of each class of pollutants among the broad range of inventoried substances. Finally, with such significant contributions of pollutant loads and associated impacts from wet-weather events, further research is required to better include temporally-differentiated emissions when evaluating eutrophication and ecotoxicity. This will provide a better understanding of how the performance of an UWS system affects the receiving environment for given local weather conditions.

This study aims to propose a holistic, life cycle assessment (LCA) of urban wastewater systems (UWS) based on a comprehensive inventory including detailed construction and operation of sewer systems and wastewater treatment plants (WWTPs). For the first time, the inventory of sewers infrastructure construction includes piping materials and aggregates, manholes, connections, civil works and road rehabilitation. The operation stage comprises energy consumption in pumping stations together with air emissions of methane and hydrogen sulphide, and water emissions from sewer leaks. Using a real case study, this LCA aims to quantify the contributions of sewer systems to the total environmental impacts of the UWS. The results show that the construction of sewer infrastructures has an environmental impact (on half of the 18 studied impact categories) larger than both the construction and operation of the WWTP. This study highlights the importance of including the construction and operation of sewer systems in the environmental assessment of centralised versus decentralised options for UWS.

Environmental impact assessment models are readily available for the assessment of pollution-related impacts in life cycle assessment (LCA). These models have led to an increased focus on water pollution issues resulting in numerous LCA studies. Recently, there have been significant developments in methods assessing freshwater use. These improvements widen the scope for the assessment of wastewater treatment (WWT) technologies, now allowing us to apprehend, for the first time, a combination of operational (energy and chemicals use), qualitative (environmental pollution) and quantitative (water deprivation) issues in wastewater treatment. This enables us to address the following question: Is water consumption during wastewater treatment environmentally significant compared to other impacts? To answer this question, a standard life cycle inventory (LCI) was performed with a focus on consumptive water uses at plant level, where several WWT technologies were operating, in different climatic conditions. The impacts of water consumption were assessed by integrating regionalized characterization factors for water deprivation within an existing life cycle impact assessment (LCIA) method. Results at the midpoint level, show that water deprivation impacts are highly variable in relation to the chosen WWT technology (water volume used) and of WWTP location (local water scarcity). At the endpoint level, water deprivation impacts on ecosystem quality and on the resource damage categories are significant for WWT technologies with great water uses in water-scarce areas. Therefore, our study shows the consideration of water consumption-related impacts is essential and underlines the need for a greater understanding of the water consumption impacts caused by WWT systems. This knowledge will help water managers better mitigate local water deprivation impacts, especially in selecting WWT technologies suitable for arid and semi-arid areas.

La dernière décennie a vu l’analyse du cycle de vie (ACV) s’imposer comme cadre méthodologique de référence pour l’évaluation quantitative des impacts environnementaux d’un produit ou d’un système de production. Bien que déjà largement utilisés dans les sphères économiques (éco-conception, responsabilité sociale des entreprises) et politiques (éco-étiquetages), le cadre méthodologique et les outils de l’ACV sont toujours un vaste objet d’étude pour la communauté scientifique. Cet article décrit un grand nombre des fronts de sciences de cette communauté et la manière dont le pôle de recherche français ELSA les aborde.

During the last two decades, Life Cycle Assessment (LCA) has been increasingly used in the agri-food sector with a shift from focused applications in industrial eco-design to a broader range of products. In France, publications of LCA studies on agricultural feedstock started in the late 90s focusing on bioenergy production. With environmental assessment close to become a prerequisite in most sectors, the number of LCA practitioners in France has rapidly increased with a diversification of actors, such as researchers, consultants or governmental agencies. Research actors in LCA work in research institutes such as INRA1, CIRAD2 or IRSTEA3. The collaboration platform ELSA4, created in 2008, brings together numerous actors from these institutes in Montpellier as well as researchers form the universities Supagro and Les Mines of Ales. It is currently the biggest French team on LCA of agro-bioprocesses. Experts on industrial eco-design, agricultural and social sciences work together on several projects that aim to both provide expertise and develop knowledge on LCA. Activities within ELSA also consist in disseminate scientific knowledge on LCA or industrial ecology through Ph.D. thesis supervision, educational and vocational training. Lately, scientists within the team have been working specifically on four scientific challenges: 1) modeling the complex agro-bioprocesses, 2) dealing with uncertainty in LCA, 3) building causal chains related to specific environmental or social impacts, and 4) refining life cycle inventories (LCIs). Further information on ELSA and possible collaboration ways can be found under www.elsa-lca.org. Researchers from CIRAD actively contribute to activities within ELSA. They are particularly involved in researches dealing with tropical crops. Specific challenges in the tropics concern notably methodological developments and data collection to better account for very diverse cropping systems such as perennials or agro-forestry cropping systems. (Resume d'auteur)

Over the past decades in Europe, man-made ecosystem s such as constructed wetland systems have been successfully harnessed to treat sewage and other pollutants in waste waters. This work present s a comparative Life Cycle Assessment (LCA) study between (i) a 2-stage vertic al Reed Bed Filter, and (ii) a conventional activated sludge system, both designed following usual French guidelines in domestic sewage treatment. The first LCA applicability challenge is to get an equilibrated mass balance between wastewa ter inputs in Nitrogen, Phosphorus, Carbon and systems outputs. The second LCA challenge overcome in this work is to provide grounds for comparison in t erms of treatment efficiency between the two systems. Results show the poor effi ciency of vertical Reed Bed Filters in removing nitrates, organic nitrogen and phosphates which highlight the need to pursue other avenues in the all important r eduction of eutrophication in waterways.

Urban expansion is a multifaceted concept which has several direct or indirect environmental effects. This work intends to use Life Cycle Assessment (LCA), to assess the effect of urban expansion on sewer infrastructure for small and medium communities (1000-5000 inhabitants). This effect is discussed in relation to land topography and population density in terms of urban planning issues. The LCA results confirm the huge contribution of the sewer on the entire footprint of the sanitation system. They highlight the environmental effect of urban sprawl on the sewer itself for all impact categories except eutrophication which is mainly linked to the efficiency of the wastewater treatment plant (WWTP). It finally advocates for scientific research perspectives and associated assessment tools to compare centralized sewerage systems to clusters of wastewater treatment units especially on uneven land and/or existing sprawled suburbs.

L'article presente l'application de l'Analyse du Cycle de Vie (ACV) a un systeme d'assainissement complet, incluant le reseau d'egout. Il presente d'abord les hypotheses retenues pour l'ACV concernant les deux systemes de traitement des eaux usees ayant tous les deux la meme charge nominale quotidienne de la DBO 5 et associes au meme reseau d'egouts. Ces systemes correspondent respectivement a (i) un filtre plante de roseaux a lit vertical pour lequelle un inventaire detaille des flux emis et des ressources consommees a ete elabore et (ii) une STEP a « boues activees » boues » issue de la base de donnees d'ACV Ecoinvent LCI. Les resultats d'ACV soulignent l'importance de l'eutrophisation qui peut facilement s'expliquer par la suppression incomplete de l'azote total et du phosphore total dans un VFCW. De facon plus surprenante, l'impact du reseau semble considerable. Enfin, l'article analyse l'applicabilite et les limites de l'ACV pour les systemes de traitement des eaux usees. / The article presents the application of Life Cycle Assessment (LCA) to a complete sanitation system including the sewer network. It first describes the LCA hypothesis which concerns two types of waste water-treatment plant with the same daily nominal load in BOD5 and associated to the same sewer network derived from the Life Cycle Inventory (LCI) database Ecoinvent. The two wastewater treatment systems compared are (i) a Vertical Flow Constructed Wetlands (VFCW) for which a detailed inventory was elaborated and (ii) an activated sludge stemming from the LCI database Ecoinvent. LCA scores of VFCW highlight the importance of eutrophication which can be easily explained by the incomplete removal of total N and total P in a VFCW. In a more surprising way, the impact of the network seems considerable. Finally, the article analyses the applicability and limitations of LCA for wastewater treatment with regard to water quality and the needed improvements of water status in LCA.