Corporate Water Accounting: An Analysis of Methods and Tools for ...

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VI. Accounting for Industrial Effluent
and Water Quality
Though water quantity receives much of
the focus in the context of corporate water
management practices and accounting, water
quality is equally important to businesses
both in terms of risk and impacts. Untreated
or insufficiently treated water can lead to
increased incidence of disease, damaged
ecosystems, and the inability of the company
and other users to use such water. Thus,
companies have just as great a stake in accounting
for—and addressing —their risk and
impacts associated with water quality as they
do for water quantity issues.
As discussed, accounting for water use/
quantity can be quite complex and requires
meshing a number of different factors in order
to be credible and meaningful. That said,
accounting for industrial effluent and related
impacts on water resources is arguably even
more complex and problematic. This complexity
is due to many factors, including the
various different types of pollutants coming
from industrial facilities and agriculture (e.g.,
phosphates, nitrates, mercury, lead, oils,
sulfur, petrochemicals, undiluted corrosives,
and hard metals, just to name a few); the
interactions among pollutants; the variety of
ways water quality can be compromised (i.e.,
contaminant loads, temperature, odor, turbidity),
and the various approaches to accounting
for the resulting impacts to ecosystems
and communities.
Measurable water quality characteristics
can be grouped into three broad categories:
• Physical characteristics (e.g., temperature,
turbidity/light penetration, and flow
velocity),
• Chemical characteristics (e.g., pH, salinity,
dissolved oxygen, nitrate, phosphate,
biological oxygen demand [BOD], toxics,
chemical oxygen demand [COD]); and
• Biological characteristics (e.g. abundance of
coliform bacteria, zooplankton, and other
organisms that serve as an indicator of
ecosystem health).
Companies aiming to account for their water
pollution and its effects on water quality
must determine a range of factors including
the volume of wastewater they discharge,
the types and loads of pollutants within that
wastewater, the short- and long-term effects
of those pollutants on receiving waterways,
and the impacts of those changes on human
health, human access to safe water, and ecosystem
function.
Dilution Water and
the Gray Water Footprint
Definition and Objectives
Water footprints deal with industrial effluents
and water quality exclusively within
the “gray water” component. The gray WF is
calculated as the volume of water that is required
to dilute pollutants to such an extent
that the quality of the water remains above
agreed water quality standards. Whether this
water is discharged back to surface or groundwater,
it is considered “used” because it is
unavailable for human use due to the fact
that it is functioning in-stream as a dilution
medium. For this reason, the gray WF is a
theoretical volume, rather than a real volume
as compared to the blue and green WF.
The methodology for determining the
gray WF is perhaps the least developed of
the three WF components. In fact, many
corporate WF studies to date do not include a
gray water component. Those that do include
gray water have done so in different ways.
However, they all utilize some permutation
of the same basic equation that uses one
water quality regulatory standard to calculate
how much water is needed to dilute pollution
to acceptable levels. Because companies
almost always release more than one pollutant
(and typically dozens) to waterways, the
methodology requires the company to select
the pollutant with the highest required dilution
volume. In theory, this dilution volume
will then be sufficient for all other pollutants
discharged. This method also requires the
company to identify the most appropriate
regulatory standard for the relevant pollutant
and location of the discharge.
At the time of this writing, the authors
were unaware of if and how the WF Decision
Support System would address the gray WF
on a watershed basis.