ENVIRONMENT AND ENERGY
There are natural limits to the assimilative
capacity of ecosystems, beyond which they
are threatened and can no longer perform
a purifying role. Once the concentration
of contaminants in runoff reaches critical
thresholds, there is a risk of abrupt and
irreversible environmental change.
Constructed wetlands and pond systems are
recognised as a reliable wastewater treatment
technology. In these systems, the planted
vegetation greatly increases the surface
contact area, which helps remove contaminants
along the filter bed consisting usually of a
combination of sand and gravel.
PLANNED USE OF WASTEWATER
FOR ECOSYSTEM SERVICES
Water reclamation and reuse are no longer
a luxury but a must, particularly in water-
scarce countries, where many cities and
environmental agencies already use partially
treated wastewater to create artificial lakes
or wetlands, recharge depleted groundwater,
restore natural wetlands or irrigate golf courses,
parks and gardens. In addition to landscape
irrigation, reclaimed water has been used to
manage natural wetlands in Spain and Mexico
to make sure that water levels are maintained
even in periods of drought.
The planned use of treated and partially
treated wastewater for ecosystem services
is relatively recent. It can increase resource
efficiency and provide benefits to
ecosystems through:
• Reducing freshwater abstraction.
• Recycling and reusing essential nutrients,
thereby reducing the fertiliser use and
GHG emissions.
• Minimising water pollution and maintaining
the quality of the river water at a sufficient
level for fisheries and other aquatic
ecosystems to thrive.
• Recharging depleted aquifers for
various beneficial uses, such as indirect
potable reuse (IPD).
Although valuation of treated wastewater use
for ecosystem services reveals favourable
environmental and economic benefits,
functional markets for many of the ecosystem
services are currently embryonic or non-
existent. Given the degradation of natural
habitats for water birds, constructed wetlands
provide a legitimate alternative.
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OPERATIONAL AND POLICY ASPECTS
Reducing pollution caused by untreated
wastewater discharges and increasing the use
of treated wastewater requires concerted efforts,
which need to be done through integrated, full-
life cycle ecosystem management and resource
efficiency objectives. Policies and approaches
that recognise wastewater as a resource and
highlight the strong linkage between ecosystem
services and human well-being are also required.
The implementation of ambient water quality
standards is key to the prevention of negative
environmental impacts and the conservation of
natural ecosystems. Ambient standards refer
to the capacity of natural ecosystems to absorb
or assimilate environmental pollution. They are
measured as the maximum allowable amount
of a substance in a water body, given as a
concentration. Since the ambient standards can be
set at differential levels for varying locations, it is
possible to use them to reduce the total maximum
load and protect valuable ecosystems in a way that
would not be possible using emission controls.
Although ambient water quality standards often
exist in national legislation, they do not exist
for all substances and all places. When they do
exist, the capacity to effectively enforce them
is often lacking, especially (but not only) in
developing countries.
CONSTRUCTED WETLANDS
FOR WASTEWATER TREATMENT IN
INDIANA, USA, AS A CASE STUDY
In Washington, Indiana, combined
sewer overflows (CSOs) were regularly
contaminating local waterways. The
city constructed an artificial wetland to
process wastewater, which saved the
city over USD26-million compared to the
estimated cost of building a conventional
treatment system, as well as saving
USD1.6-million annually in operational
costs. Water discharged from the
constructed wetland system has exceeded
the water quality standards for the city’s
wastewater treatment plant, and wildlife
has returned to the local waterways since
the system’s construction. PA
Water reclamation
and reuse are no longer
a luxury but a must.
May 2018 Volume 24 I Number 3
May 2018 Volume 24 I Number 3