Overall system analysis
Two methods can be used to calculatewater footprint: the chain
summation approach and the stepwise accumulative approach
(Herath et al., 2011; WWF-UK, 2009). The chain summation
approach is primarily used for production systems with only one
product output. The water footprint associated with the various
steps in the production system can be entirely attributed to the
product that results from a system. The stepwise accumulative
approach is a general water footprint calculation method based on
the water footprint of the final steps in the production of final and
necessary products and on the water footprint calculation in the
processing steps. The production chain of the iron and steel industry
is complex and includes ore smelting refining, continuous casting,
rolling, and other processes carried out in numerous workshops
with extensive water and energy consumption in every link. Fig. 1
shows the iron and steel production processes. The water discharged by each workshop undergoes substantial recovery or
flows into other production workshops. Most large iron and steel
factories have their own wastewater treatment facilities. Both
footprinting methods require detailed information and an extensive
amount of supporting data, which may be confidential, especially in
the heavy industry. This makes it difficult to calculate the industry's
water footprint and promote better water management practices.
In this work, an overall system analysis is performed to assess
water footprint. In the process of calculating thewater footprint, we
consider direct WC, energy consumption, and local water environmental
effects, to better understand the effects of the iron and
steel industry onwater resources. This method is mainly focused on
thewater footprint of the production process in the selected factory
and therefore does not require long-term analysis and an extensive
amount of data. Given these features, the proposed method can be
applied in other industries.