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ENVIRONMENT AND ENERGY
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Table 1: Examples of
negative impacts of
untreated wastewater
on human health,
the environment, and
productive activities
Wastewater
treatment can
allow for the
separation
of water
and other
constituents,
which can
then be reused
or disposed of.
2. The removal of contaminants from wastewater
streams.
Operational systems (including collection infrastructure)
and treatment processes that remove various
constituents of wastewater (i.e. contaminants) so that it
can be safely used or returned to the water cycle with
minimal environmental impacts. There are several types
and levels of wastewater treatment, the choice of which
is dependent on the nature of the contaminants, the
pollution load and the anticipated end use of the effluent.
3. The use of wastewater (i.e. water reuse)
Safe use of treated or untreated wastewater under
controlled conditions for beneficial purposes. Historically
used primarily for irrigation, wastewater treatment
technologies have now advanced to allow for the use of
treated wastewater for other uses, provided that the level
of treatment and the quality of the effluent are ‘fit for
purpose’.
4. The recovery of useful by-products
Various constituents of wastewater can be extracted,
either directly (e.g. heat, nutrients, organic matter and
metals) or via supplementary transformation processes
(e.g. biogas from sludge or biofuels from microalgae).
There is a growing number of potentially cost-effective
opportunities for extracting useful materials from
wastewater, such as nitrogen and phosphorus, that
can be transformed into fertiliser.
An additional role of the wastewater management cycle
is to mitigate any negative impacts on human health, the
economy and the environment. When taking into account
the multiple benefits of improved wastewater management,
several of these processes can be considered cost-effective,
thus adding value across the wastewater management cycle
November 2017 Volume 23 I Number 9
while supporting the further development of water supply and
sanitation systems.
Based on the assumption that it is possible to align water
quality requirements with water use locations, multiple
use systems with cascading reuse of water from higher to
lower water quality can make water reuse more affordable
than providing extensive water treatment at each point of
abstraction along a river basin (UNEP, 2015c).
WASTEWATER AS A RESOURCE: SEIZING THE
OPPORTUNITIES
In practice, the goal is to go beyond mere pollution
abatement and to seek to gain value from wastewater, if
for no other reason, as an additional means of paying for
wastewater management and for enhancing the economic
sustainability of the system.
However, wastewater management is already an important
part of several different resource cycles and is well
positioned to play a central rol