Page 31 - Chemical Technology

Chemical Technology • January 2013 29
water treatment
The Greek philosopher Pindar said that the best of
all things is water. Throughout human history the
need for water has always been appreciated. It is
present everywhere, and without water, life will cease.
Water is constantly in motion, passing from one state
to another and from one location to another. Whether
the water is in motion or stationary, it invariably contains
extraneous materials, some due to natural causes, but
others because of human activities (Biswas, 2008).
Future business depends on water resources. Every
operation depends on and impacts water resources. Some
use it to process raw materials and manufacture goods.
Some use it for cooling and cleaning. For others, it is a cen-
tral ingredient in the goods they produce or it is required to
consume the product that is sold.
However, the sustainability of water resources is
increasingly under pressure. Globally, availability of
freshwater is steadily decreasing (UN, 2006). This trend
will continue as the world’s population grows, emerging
economies increase consumption levels and climate
change unfolds. Industries and businesses recognize
the water challenge, but to respond effectively they
need tools and standards to move toward more sustain-
able practices.
One such tool to address the effective use of water
is Water Footprinting. Water Footprint can be used to
calculate the total amount of water that is consumed both
directly and indirectly. Its use is aimed first at quantifying,
then at reducing the consumption of water across a prod-
uct, process or service.
Origin of Water Footprinting
The Water Footprint concept was introduced in 2002 by
Arjen Hoekstra as a measure of water use. Co-operation
between global leading institutions in the field has led
to the establishment of the Water Footprint Network in
2008. The network aims to co-ordinate efforts to further
develop and disseminate knowledge on water footprint
concepts, methods and tools. Interest in Water Footprint-
ing is rooted in the recognition that impacts on freshwa-
ter systems can ultimately be linked to human consump-
tion. Issues such as water shortage and pollution can
be better understood and addressed by considering the
production process and the supply chain as a whole.
Water Footprinting concept
Water Footprinting is a method developed to determine
the amount of freshwater used in the whole supply chain
of producing a product or service (Hoekstra, 2011). The
water footprint method explores both direct1 and indirect2
water usage of a product, service or process. This makes
Water Footprinting
by S Dhlamini, T Mkhonza, EL Haggard, A Osman, CM Sheridan and KG Harding, all of the School of
Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg, South Africa,
and F Crundwell and A Osman, both of CM Solutions, Johannesburg, South Africa
it different from other water usage quantification concepts
such as the virtual water concept and the water withdrawal
concept, which only explore direct water use. Through focus-
ing on both direct and indirect water use, the water footprint
method gives valuable information on water usage which
could be used to make informed decisions in water man-
agement plans. A Water Footprint can be performed for a
variety of entities including countries, products, river basins
and commodities. Country and river basin footprints focus
on policy formation, whereas product and commodity water
footprints focus on understanding water-related risks in the
supply chain and the management thereof. The approach
used for a Water Footprint Assessment differs depending
on the intended use. For example, the private sector is often
interested in understanding water dependencies in the
supply chain of its products in order to help understand the
risks involved in production and distribution.
Water Footprint assessment
A sequence of four steps is involved in determining a
Water Footprint Assessment. These four steps, shown in
Figure 1, are (1) setting goals and scope, (2) performing
an account of the water footprint, (3) completing a sustain-
ability assessment and (4) a response formulation. Each of
these steps is discussed below.
1 Direct water: Consumption and pollution associated with the water used by the consumer or producer.
2 Indirect water: Consumption and pollution associated with the production of the goods and services
consumed by the consumer or the inputs used by the producer.
Setting goals and scope
Any investigation requires a decision on what to include
and what to exclude from the investigation. For Water
Footprinting, these decisions are made explicit, and
include factors such as:
• The purpose of the water assessment
• The type of water footprint to be conducted
◦ for a process step, a product, consumer, group of con-
sumers, within a geographically delineated area, for a
business, a business sector, or humanity as a whole
• Decide which type of water to consider for the water
footprint accounting
◦ blue and/or grey and/or green (see below for definitions),
◦ direct and/or indirect water, and
◦ internal and/or external.
• Choose a time period for the investigation
• Determine a system boundary (where the analysis
should be truncated)
Figure 1: The four steps of a Water Footprint Assessment