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

Systems Analysis of Zaragoza UWS
Guillermo Penagos
3.2.4.3 CO 2 Emissions from electricity consumption
Raw data concerning energy consumption of the DWTP and the WWTPs were provided
by the Local Agenda 21 Office at Zaragoza. The derived CO 2 emissions were calculated
regarding the electric energy sources in Spain provided by Ministerio de Industria,
Turismo y Comercio de España (2007) referred in figure 9. Emission factors from
European Commission (1995) were used (for raw data and calculations refer to annex
8).
3.2.4.4 CO 2 production from sludge
Wastewater sludge emits CO 2 as a function of the OM concentration. Raw data
regarding wastewater sludge production at the WWTPs were provided by the Local
Agenda 21 Office at Zaragoza municipality. COD content in the sludge was calculated
from the mass balance between inflow and outflow load at each facility. Multiplication
factors from Levlin (2005) were used to calculate TOC content and CO 2 :
TOC = 40% of COD
CO 2 = 3.66*TOC
3.2.5 Scenario analysis
Based on the collected data, an exercise for Scenario Analysis is presented following the
methodology suggested by Assimacopoulos (2007) in which the main drivers for change
and sustainability are identified by means of a problem tree analysis. Drivers are
qualitatively discriminated under the criteria of importance and uncertainty. Possible
scenarios resulting from the combination of drivers considered as more important and
more uncertain are set. Finally strategies to cope with such scenarios are suggested.
The aim of the strategies is to adapt the system to reach a sustainability vision.
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