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Reed beds are often included in both centralised and
decentralised treatment systems.
1970s, anaerobic digestion became the
preferred method to treat wastewater and
sludge, on account of the reduced amount
of energy available.
The 1980s and 1990s saw an increased
interest in nutrient removal, mainly in the
developed world, as nutrient discharge
had led to the eutrophication of water
bodies in many regions of the world.
During the same period, significant
advances were made in the use of more
natural treatment systems, such as waste
stabilisation ponds and reed bed systems.
These types of systems offer efficient
reduction in pathogens with low capital
and operational costs. Indeed, even in
developed economies, they find a use in
small-community treatment systems.
The most recent trends have seen treatment
systems that address the reduction of GHG
emissions. In parallel, much research was
undertaken, particularly in the developing
regions of the world, on systems that focused
on reducing the bacteriological hazards.
SEWER MINING AND COMPONENT
SEPARATION
Active direct use of wastewater and the
nutrients it contains has often been driven
by necessity, but its use for recreation or
other purposes has been documented in
many developed regions. New technologies
are emerging that allow for the upgrading
of wastewater treatment plants to ‘factories’
in which the incoming materials are
deconstructed to units such as ammonia,
carbon dioxide and clean minerals.
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ENVIRONMENT AND ENERGY
This is followed by a highly intensive and
efficient microbial re-synthesis process
where the used nitrogen is harvested as
microbial protein (at efficiencies close
to 100%), which can be used for animal
feed and food purposes. Another new
approach has been proposed in which the
used water is subjected to a procedure
that allows the uptake of its organics and
inorganics materials into fish biomass.
The fish are harvested and processed
to become a source of feed or food. The
remaining water can be used for irrigation
or discharged.
Indeed, the organics and inorganics present
in the incoming used water are removed to a
large extent in the form of the harvested fish.
The key features of both of these concepts
for treating wastewater is that they do not
follow the route of destroying the nutritive
value which is present in the used water.
On the contrary, they add a form of
renewable energy to allow aerobic
microbes to upgrade the nutrients to
microbial cells growing in flocs, and
they harvest the latter by fish grazing
on them. In the latter case, biomass is
then processed to become of further
use as feed or food. Concerning the
isolation and separation of useful
wastewater components, it is likely that
urine collection and use will become an
increasingly important component of
ecological wastewater management,
as it contains 88% of the nitrogen and
66% of the phosphorus found in
human waste. PA
August 2018 Volume 24 I Number 6