Systems Analysis of Zaragoza Urban Water - SWITCH - Managing ...

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Systems Analysis of Zaragoza UWS Guillermo Penagos There is a need of information tools that serve to evaluate this complexity and search for alternatives that make the concept of sustainability fully operational for the Urban Water System. Initial interest of researchers and decision makers in this regard was to produce ad hoc Indicators for Sustainable Development (Lundin and Morrison, 2002) A large number of indicators are used by water and waste water organizations to assess their technical performance. Such indicators may differ between different organizations and different countries. The results are large amounts of data, difficult to understand and to interpret. Besides only few of those indicators have been developed to quantify sustainability. There is still a need for a limited number of sustainability indicators for urban water systems (Lundin, 1999). One of the main problems of quantifying sustainability is the lack of a structured methodology to develop indicators, with the consequent risk that such indicators would be ineffective and, possibly detrimental in promoting sustainability objectives (Lundin and Morrison, 2002). Therefore, recent studies have based on Systems Analysis Approach and have used techniques related to the concept of industrial ecology, such as Material Flow Analysis and Life Cycle Assessment. When properly followed, those techniques have proven to be quite effective to evaluate environmental performance of Urban Water Systems. Some authors have concluded that such techniques are needed as a basis for all other studies concerning Urban Water Systems because the flows, the major sources and the fate of water and its major constituents such as nutrients, pathogens and harmful chemicals, must be clear for all alternative management strategies (Ahlman, 2006; Benedetti et al., 2005; Lindqvist and Malmborg, 2004). LCA analysis is suggested to be a comprehensive technique to assess environmental sustainability of UWS. The term “Life cycle” referes to the major activities in the course of a product lifespan from its manufacture, use and maintenance, to its final disposal, including the raw material acquisition required to manufacture the product. Impacts related to outputs will be emissions to different environmental compartments (Lundin and Morrison, 2002). The main advantage of LCA is that it can contribute to evaluate the impacts upon different environmental compartments, preventing the implementation of management 10
Systems Analysis of Zaragoza UWS Guillermo Penagos options that, in the search for mitigation, end up by shifting pollution from one place to another. This is the trade-off of for instance, the alternative of nutrient recycling from wastewater treatment sludge, which will protect the receiving water body, but can constitute a further risk for arable land protection, since such sludge may content not just nutrients, but also heavy metals, being also a further risk for food security (Malmqvist & Palmquist, 2005). During the last decade there have been many research works using LCA to assess urban water systems. One of the major problems faced by this technique is the definition of system boundaries. Many choices can be made in terms of time horizon, geographic borders as well as functional boundaries. Results will be very much affected by such choices, being often not comparable. For instance most studies have focused on either water supply or on WWT systems. Crettaz et al. (1997) evaluated different alternatives for alternatives drinking water distribution and treatment as well as wastewater treatment. They also assessed on-site alternatives such as rainwater storage, sewage separation and water-saving toilets. Authors found that rainwater use was not favorable in terms of energy consumption and also it would lead to a higher contamination of heavy metals to water and soils. Roeleveld et al. (1997) performed an LCA of different conventional wastewater treatment methods in at a national level in the Netherlands. The authors concluded that to improve the sustainability, the discharge of emissions should be reduced from the effluent. Energy use, construction and the use of chemicals were considered less important as compared to the operation of the system. Matsuhashi et al. (1997) compared different sludge treatment processes: landfilling, incineration, ozonation and composting. One conclusion the authors draw was that when sludge is used to improve soil fertility, the benefit should be compared with an LCA for production and use of chemical fertilizer. Neumayr et al. (1997) compared six different alternatives for sludge recycling strategies. Authors found that energy consumption, foil fuels used for transportation and direct 11
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