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biogas production and also any effect that adding waste will
have on the production of biosolids, which are extracted from the
treatment process and provided to farmers for fertiliser.
‘The research will enable us to determine exactly the correct
amounts of different types of food waste to be added in a variety
of mixtures to maximise energy production, and to ensure that
there are no downsides to the process.
‘Once products and methodologies are tested and proven, we will
be able to roll out the processes at our other wastewater treatment
plants, accepting a range of additional food waste products.
‘Sydney Water’s wastewater treatment plants are the bio-
generators of the future, where waste is being turned into a
valuable resource,’ says Bustamante.
Sydney Water’s Bondi Sewage Treatment Plant produces around
13 per cent more electricity than it consumes each year, allowing
the return of electricity to the grid. Sydney Water is also currently
trialling the use of fruit and vegetable waste at its Cronulla
Wastewater Treatment Plant.
Sydney Water also extracts more that 180,000 tonnes of biosolids
from the wastewater treatment process, which is provided to New
South Wales farmers each year to fertilise animal feed crops and
condition the soil.
Sydney Water currently generates around 20 per cent of its total
energy needs across its network. It also exports six gigawatt hours
to the electricity grid over a year.
Across all of its wastewater treatment facilities, Sydney Water
is producing enough energy onsite to power more than 11,000
homes each year, reducing greenhouse gas emissions by more
than 70,000 tonnes per year, which is the equivalent of keeping
17,500 cars off the road for one year.
Further future production of green energy is expected based on
the innovative research work at Shellharbour and other projects.
Professor Long Nghiem, from the University of Wollongong’s
Faculty of Engineering and Information Sciences, says, ‘There is a
great deal of interest worldwide in harnessing the ability to recover
energy and nutrients from wastewater, which could turn treatment
plants into biorefineries’.
Laboratory-scale anaerobic digesters are being used to determine
the effectiveness of different organic wastes for co-digestion.
Experiments are being performed to determine the optimum
mixing ratio for co-digestion. The effects of temperature and
location within the digester are also being investigated.
A pilot plant with two 1000-litre digesters has been installed at
the Shellharbour Wastewater Treatment Plant. The pilot plant can
be remotely controlled via a smartphone. It has all the functionality
of a full-scale plant. The laboratory-scale experiments are being
repeated in the pilot plant to determine scale effects.
The pilot plant will allow the impact on downstream processes
to be evaluated. This will include examining biosolids odour,
dewaterability and bulk material handling ability.
The impact of co-digestion on biosolid odour is also being
investigated, as increasing odour formation creates a negative
The University of Wollongong and Sydney Water have developed
a proof-of-concept technique to regulate micro-aeration within
the anaerobic digester to control hydrogen sulphide formation
in biogas. This technique has the potential to reduce odours
and corrosion (which could significantly reduce cogeneration
maintenance costs) without any significant capital investment
and ongoing material cost. The pilot plant will be used to further
validate this technique and to determine its scalability.
The University of Wollongong has recently developed a forward
osmosis (FO)–membrane distillation (MD) technique to recover
phosphorus in the form of struvite from the sludge centrate.
Reducing downstream nutrient flows is important for the plant’s
performance. This technique will be further refined and developed
for practical use with assessment of factors such as fouling
control and the use of different extracting compounds.
A smart and interactive dashboard will be developed to allow the
research results to be easily implemented in the field.
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