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ABSTRACT The EU FP6 NEPTUNE project is related to the EU Water Framework Directive and the main goal is to develop new and optimize existing waste water.

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Presentation on theme: "ABSTRACT The EU FP6 NEPTUNE project is related to the EU Water Framework Directive and the main goal is to develop new and optimize existing waste water."— Presentation transcript:

1 ABSTRACT The EU FP6 NEPTUNE project is related to the EU Water Framework Directive and the main goal is to develop new and optimize existing waste water treatment technologies (WWTT) and sludge handling methods for municipal waste water. Besides nutrients, a special focus area is micropollutants (e.g. pharmaceuticals, heavy metals and endocrine disrupters). As part of this work a holistic based prioritisation among technologies and optimisations is to be done. Tools for this prioritisation include life cycle assessment (LCA) and cost/efficiency. As novel approaches, potential ecotoxicity impact from a high number of micropollutants and the potential impact from pathogens are to be included. In total more that 20 different waste water and sludge treatment technologies are to be assessed. This paper will present the first preliminary LCA results from running existing life cycle impact assessment (LCIA) methodology on some of the WWTTs. METHODOLOGY A comprehensive theoretical framework for carrying out LCAs of WWTTs has been developed and streamlined for use in NEPTUNE (www.eu- neptune.org). This framework is based on EDIP 1997 and models process-, wastewater- and sludge-specific burdens of WWTTs as illustrated in figure 1 (Hansen 2008, Larsen et al. 2006). Note that on this figure, only wastewater-specific burdens are schematized and sludge- specific burdens should be considered in the same way. To illustrate possible applications of the methodology, preliminary results from the first two case studies are presented on this poster, based on data from the EcoInvent database and NEPTUNE data. Each case study will be assessed through the concept of “environmental efficiency”. Environmental efficiency is assessed by comparing the environmental impacts induced by the physical inputs necessary to run the WWTP (in yellow on figure 1) to the potential environmental impacts of the water emissions (in blue on figure 1) avoided by the treatment process (i.e. impact of influent minus impact of effluent).www.eu- neptune.org CASE STUDY 1: REFERENCE WWTP The plant modelled in this case study and illustrated in figure 2 represents a capacity- based average of Swiss municipal wastewater treatment plants (WWTPs) as modelled by Doka (2003) for use with the EcoInvent database. As such, the model is very comprehensive: its physical inventory includes all infrastructure and operating inputs necessary to run the WWTP, along with the corresponding disposal processes. Also, more than 30 parameters including organic matter, nutrients, heavy metals and other inorganic substances in the water are tracked throughout the system and are accounted for in terms of their fate in air, water and solid media. This case study is here used as a reference example showing a rather comprehensive LCA of a given combination of WWTTs. CASE STUDY 1: INTERPRETATION Figure 3 shows the environmental efficiency profile of the reference WWTP. Note: avoided impacts refer to the difference between the environmental impact potentials resulting from releasing raw wastewater directly into the environment without treatment, and the impact potentials from emissions to air, water and soil stemming from the substances in the wastewater and their fate after going through the reference WWTP. Induced impacts refer to the impact potentials resulting from constructing, operating and disposing of the WWTP. From this figure, we may conclude that the environmental efficiency of the reference WWTP is close to a 2:1 ratio, meaning that for every environmental impact induced by this WWTT train, 2 times more impacts are actually avoided thereby making it a viable WWTT train for treating water containing the inventoried substances/parameters. CASE STUDY 2: WWTP WITH(OUT) PRIMARY SETTLING In the second case study, two similar WWTPs with and without primary settler are compared, based on preliminary NEPTUNE data. Figure 4 shows a WWTP identical to the reference WWTP. Figure 5 shows a similar system, except without primary settler. The two WWTPs are compared exclusively on the basis of their energy consumption and generation patterns as well as on their capacity to remove total nitrogen in the water. On the two figures, processes differing within those parameters (energy and nitrogen) are highlighted in grey while differences in energy consumption and nitrogen removal are highlighted in green (positive for the environment) and orange (negative for the environment). Differences in the infrastructure inventory and other parameters are disregarded in the comparison. CASE STUDY 2: INTERPRETATION Based on figure 4 and 5, a comparative energy and nitrogen balance may be carried out, resulting in the following conclusions per functional unit (m3 waste water): The WWTP with primary settler releases 4 g tot-N more. The WWTP without primary settling consumes kWh more. Therefore, we may compare both systems by comparing the impact associated with nitrogen removal vs. electricity consumption, as illustrated in figure 6. Since electricity may be generated by different means with different associated environmental impacts, figure 6 presents electricity grid mixes corresponding to European countries illustrating the range of electricity sources available in Europe: Norway: electricity is supplied mainly from hydro-power, resulting in generally lower emissions to the environment. Poland: electricity generation is based mainly on coal power and as such, results in high emissions to the environment. From this data, figure 6 and disregarding all parameters except nitrogen removal (assuming nitrogen limited recipients) and energy balances (average electricity approach), we may conclude the following: WWTPs without primary settling achieve a better nutrient removal rate although they require more energy to operate because of the higher loads handled in the biological step To select one system over the other based on nutrient removal vs. energy balance, the national profile of electricity generation technologies is important: For countries with relatively clean electricity (e.g. Switzerland), a WWTP without primary settling may be a better option. For countries with electricity based primarily on fossil fuel (e.g. Poland), a standard WWTP with primary settling should be preferred. Treated water to river or lake Energy Primary settler Anaerobic digestion Incineration SLUDGE INCINERATION Sludge heater Raw sewage input Primary settler sludge Recirculation of digestion effluent Grit removal Secondary settler Activated sludge Excess activated sludge Biogas Digester sludge Phosphate precipitation Dewatering Raw sludge Chemical sludge Activated sludge aeration (Anaerobic denitrification) REFERENCES Doka G (2003). Part IV: Life cycle inventory of wastewater treatment. Life cycle inventories of waste treatment services – EcoInvent report No. 13. Swiss Center for Life Cycle Inventories, Switzerland Hansen PA (2008). A conceptual framework for life cycle assessment of wastewater treatment systems – Master thesis, DTU Management, LCA Group, Technical University of Denmark Larsen HF, Hauschild M, Wenzel H, Almemark M (2007). Homogeneous LCA methodology agreed on by NEPTUNE and INNOWATECH – Deliverable D4.1. EC Project “NEPTUNE”, contract No.: ACKNOWLEDGEMENT This study was part of the EU Neptune project (Contract No , SUSTDEV II.3.2), which was financially supported by grants obtained from the EU Commission within the Energy, Global Change and Ecosystems Program of the Sixth Framework (FP Global-4). Corresponding author: Henrik Fred Larsen Figure 2: Reference: typical 3-stage WWTP based on Doka (2003) Sustainable treatment of municipal wastewater Peter Augusto Hansen & Henrik Fred Larsen (DTU Management, Technical University of Denmark - Lyngby, Denmark) Figure 1: Framework diagram Figure 5: WWTP without primary settler Biogas El Water Sludge El Heat 1 m 3 WW Activated sludge Dewatering Co-generation of Heat and Power Effluent El Heat El Heat Ashes Slag kWh kWh kWh Mesophilic Anaerobic Digestion Secondary Settling Incineration Figure 4: WWTP with primary settler Biogas El Water Sludge El Heat 1 m 3 WW Activated sludge Dewatering Co-generation of Heat and Power El Heat El Heat Ashes Slag + 4 g tot-N kWh Mesophilic Anaerobic Digestion Secondary Settling Incineration Primary Settling


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