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

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Systems Analysis of Zaragoza UWS Guillermo Penagos The Municipality of Zaragoza is responsible for water planning and management in the city. They own and operate facilities for drinking water supply, sewers and wastewater treatment plants. During the last decade Zaragoza has carried out several important projects concerning water management. In 1993 a WWTP providing tertiary treatment was built. At the same time sewerage system began expanding and nowadays almost all industrial discharges -with two special exceptions that will be further discussed in this report- are connected to sewers. In 1997 the city started a project called “Zaragoza water saving city”, consisting of education programs to encourage rational water use at households and industries by means of water saving devices and improving consumption habits. The municipality committed within this project to a rational use of water for landscaping. In 2005 this project managed to considerably reduce water demand and it was selected by Habitat UN as one of the 100 successful projects concerning urban sustainability worldwide. Currently municipality is using tariffs for water supply and WWT services as an instrument to punish excessive consumption as well as to reward saving. In the year 2000 both national and regional government approved a project aimed to shift the tap water source from the Ebro to the Aragon River regulated in “Yesa” reservoir in the Pyrenees, where water quality is more suitable for human consumption than in the Ebro River. In 2002 municipality initiated a seven years project aimed to improve water supply for Zaragoza. This project consists on (1) upgrading the DWTP, (2) replacing, upgrading or taking out of work existing tanks and pumping stations and (3) replacing a considerable percentage of the pipeline network. Total investment for this project is around 82 million euro. As result of all these efforts Zaragoza’s water withdrawal has significantly decreased. 3.2 General Approach A systems approach is used here to analyze the Urban Water System of Zaragoza by means of Life Cycle Analysis (LCA). The procedure usually comprises four steeps: (1) goal and system definition, (2) life cycle inventory (3) impact assessment and (4) 16
Systems Analysis of Zaragoza UWS Guillermo Penagos interpretation (U.S EPA, 2006; Ayers and Ayers, 2002). For the present work the step 3 was not carried out and interpretation is made from the life cycle inventory. 3.2.1 Developing flow diagram First step to define system boundaries is developing a flow diagram showing the processes to be evaluated. In the present work the aim is to analyze all the major processes for the urban water system: water withdrawal, water treatment and distribution, water use, wastewater transportation and wastewater treatment. Along these processes a water balance is made and major flows and stocks of chemical products, nutrients and heavy metals are considered. The direct and indirect consumptions of energy (transportation of chemical products and sludge) are also considered, as well as direct (sewage sludge treatment and disposal) and indirect atmospheric emissions (derived from energy consumption). 3.2.2 Time horizon An assessment of sustainability should ideally extend over a time horizon of several decades (Lundin and Morrison, 2002). However due to time and data constraints, the time period considered here is six years, which considers major investments on improving the technical performance of the water system. 3.2.3 Data collection Data collection for this M Sc research lasted from November the 8 th up to December the 29 th . As starting point staff from the Local Agenda 21 Office provided some reports concerning water management in Zaragoza as well as specific features of the Urban Water System and its evolution during the last decade. Most time was devoted to carefully review those reports in order to fully understand the sustainability issues that have been already identified by the municipality as well as other issues, probably neglected so far and which might be interesting for the SWITCH project. Recent data necessary to perform mass and energy balances are partially available in different electronic formats such as notepad, pdf, word, excel, etc. Historical data are 17
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