WATER IS REQUIRED to produce nearly all forms of energy. At the same time, electricity is needed to provide drinking water and treat wastewater. Recognizing rising water-energy nexus pressures, a range of water utilities around the world are developing innovative solutions to reduce these pressures.

2. EXPRESS WATERAugust, 201852
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WATER IS REQUIRED to
produce nearly all forms of
energy. At the same time, elec-
tricity is needed to provide
drinking water and treat
wastewater. Recognizing ris-
ing water-energy nexus pres-
sures, a range of water utili-
ties around the world are
developing innovative solu-
tions to reduce these pres-
sures.
Melbourne Water has
hydro-electric power stations
operating throughout its sup-
ply network, generating
renewable energy from the
flow and pressure of moving
water, with the electricity
being fed back into the grid.
In addition to the nine
existing power stations, five
additional mini-hydro plants
were commissioned in 2016-
2017. The plants were deliv-
ered in pre-assembled, self-
contained units and provide
simple, weather-resistant
power delivery solutions that
can be brought online quickly.
In total, the 14 hydro-electric
power stations can generate
up to 69,5000-megawatt
hours of electricity per year.
By operating these power
stations, Melbourne Water
prevents over 75,800 tons of
carbon dioxide emissions each
year, which is equivalent to
the emissions of over 14,000
households or taking more
than 29,000 cars off the road.
Meanwhile, at Melbourne
Water’s Western Treatment
Plant, which serves 1.6 million
people in the central, north-
ern, and western suburbs of
Melbourne, sewage is consid-
ered more than a waste prod-
uct, with the utility generating
electricity by combusting bio-
gas that is captured under
covers that are placed over
the sewage treatment lagoons.
The Western Treatment
Plant uses biogas to meet
nearly all its electricity needs
with 71,500-megawatt hours
of renewable energy generat-
ed each year, which prevents
87,000 tons of carbon dioxide
being emitted through the
burning of fossil fuels. At
times the treatment plant gen-
erates excess renewable ener-
gy which is exported to the
electricity grid to offset usage
at the utility’s other sites.
Athens Water Supply and
Sewerage Company (EYDAP)
has launched an ambitious
program of renewable energy
utilization with the objective
of contributing to the opti-
mization of the energy bal-
ance across the country and
society and exploring the pos-
sibility of expanding to new
profitable business.
Along the aqueduct system
that brings raw water into the
Athens area for treatment,
there are existing energy-dis-
sipation works (small water-
falls along the aqueduct).
EYDAP is in process of con-
verting these energy dissipa-
tion works into energy pro-
duction plants, therefore tak-
ing advantage of the aque-
ducts’ hydropower potential.
These energy production
plants consist of temporarily
redirected water flowing
through a turbine that con-
verts the hydraulic energy
potential into electricity by
use of a generator. The water
then re-joins the aqueduct at a
lower elevation and continues
its flow to the water treatment
plant.
To date, EYDAP has con-
structed six small hydropower
plants along its aqueducts
located in Kirfi (760 kW),
Elikona (650 kW), Kartala
Kihairona (1,200 kW), Mandra
(630 kW), Evinos Dam (820
kW), and Klidi (590 kW).
San Antonio Water System
(SAWS) is harnessing
methane gas generated during
the wastewater treatment
process as a renewable energy
source. The biogas - which is
60% methane - is a by-product
of the anaerobic digestion
process from biosolids, with
SAWS producing around
140,000 tons of biosolids per
annum. SAWS has partnered
with Ameresco, Inc., a nation-
al energy company that focus-
es on renewable energy.
Since 2010, Ameresco has
processed more than 1.5 mil-
lion standard cubic feet of bio-
gas a day and delivered a min-
imum of 900,000 cubic feet of
natural gas each day to the
nearby commercial pipeline to
sell on the open market.
Economically, SAWS receive
around $200,000 in annual
royalties from the sale of the
biogas, reducing the costs of
SAWS operations and keeping
rates affordable, while envi-
ronmentally the harnessing of
biogas instead of flaring
reduces 19,739 tonnes of car-
bon dioxide each year.
Scottish Water Horizons -
a commercial subsidiary of
Scottish Water - has teamed
up with SHARC Energy
Systems to establish a joint
venture to expand and accel-
erate the deployment of
wastewater heat recovery sys-
tems across Scotland.
Scottish Water Horizons will
provide commercial funding
for the projects while SHARC
Energy Systems will provide
the design, build, and opera-
tional expertise for the green
energy installations.
The Scottish Government
is supporting the scheme too
by providing 50% capital sup-
port through its Low Carbon
Infrastructure Transition
Programme.
The SHARC heat recovery
technology, which took six
years of research and develop-
ment, extracts the natural
warmth found within the
wastewater network, which
sits at around 21 degrees
Celsius by a) Using a patented
system to separate solids and
liquids within the wastewater
stream via a unique clog-proof
mechanical filtration system,
b) Directing the filtered
wastewater through a heat
exchanger to extract the natu-
ral heat, and c) Using a heat
pump to boost the tempera-
ture even further (to around
60 degrees Celsius) before
transferring the heat for heat-
ing of buildings and hot water
systems (done under a heat
supply agreement).
Commercial, private, and pub-
lic customers who sign up
with the innovative heat sys-
tem do not pay any up-front
investment costs. Instead, the
customer signs up to a long-
term heat supply agreement
with all the design, installa-
tion, and supply of equipment
costs.
In a joint project between
Hamburg Wasser and
Eisenbahnbauverein Harburg
(EBV), around 220 housing
units of a residential complex
of the housing cooperative in
Hastedtstraße were retrofit-
ted to enable heat from waste-
water to warm their water
and night storage heaters. In
this, residual heat from waste-
water is captured and an
exchanger transfers it to the
heating center of the residen-
tial district. From there, the
heat is transferred to a buffer
storage ready for use by the
housing units. During peak
times, any additional heat
required is generated from a
modern gas heater.
Meanwhile, in Hamburg’s
Stellingen district, Hamburg
Wasser makes use of the fact
that its groundwater has a
constant temperature of
around 9 degrees Celsius
throughout the year by trans-
ferring this natural cold to a
cooling system that is con-
nected to the neighboring
Arctic Ocean of the
Hagenbeck Zoo. This ensures
that the polar bears and pen-
guins stay cool in the summer
.
Robert Brears is the author
of Urban Water Security,
Founder of Mitidaption, and
Our Future Water."
@Mitidaption
By Robert C. Brears