Sydney Water’s Lower South Creek Treatment Program was awarded the highest design sustainability rating ever achieved for an Australian water infrastructure project by the Infrastructure Sustainability Council of Australia (ISCA). The high score was given to its $450 million program of upgrades to three treatment facilities in Riverstone, St Marys and Quakers Hill involving two Australian-first technology innovations and two NSW-first process innovations.
The upgrades aim to improve the quality and reliability of Sydney Water’s Riverstone, St Marys and Quakers Hill treatment facilities in order to cater for growth in the area.
Sydney’s North West is predicted to grow by an additional third of a million people by 2040, which is equivalent to the population of Newcastle, NSW’s seventh largest city.
The program involves the adoption of several new technologies that will help make water treatment more sustainable, cost efficient and effective for Sydney Water.
It’s these innovations that are set to achieve a 42 per cent reduction in whole-of-life greenhouse gas emissions that earned the program the “excellent” design rating of 69.7 points from ISCA, the highest ever for a water project.
The program received a full ten out of ten score for innovation from ISCA, with two of the innovation points awarded for exceeding the benchmarks for energy and carbon reduction, and renewable energy supply.
So far, a major upgrade to the Riverstone Wastewater Treatment Plant has been completed which increased the capacity of the plant by more than three times, from 4ML per day to 14ML per day (megalitre = one million litres).
Upgrades to the Quakers Hill and St Marys Water Recycling Plants (WRP) are currently underway and are set to be completed in 2021.
It’s these two upgrades, plus a repurposed 12.5km transfer pipeline between the two plants, that were the scope for the Infrastructure Sustainability (IS) Design Rating.
A spokesperson for Sydney Water said the repurposed 12.5km transfer pipeline will allow the utility to centralise biosolid treatment at St Marys WRP, which is in an industrial area.
“This will reduce the noise and traffic impacts at Quakers Hill WRP, which is located in a predominately residential area.
We will also capture biogas through cogeneration to create renewable energy, this will reduce our electricity use and Sydney Water’s carbon footprint,” the spokesperson said.
When all three treatment facilities are fully operational by 2022, Sydney Water will have helped enhance the waterway health along South Creek and its tributaries, contributing to the sustainability and liveability of these fast-growing communities.
Implementing innovative Australian-first technologies
This program of works included the implementation of numerous sustainable innovations that will not only benefit these three treatment plants, but will also provide guidance for the rest of Sydney Water’s treatment facilities, as well as other water utilities.
There are two Australian-first technology/process innovations being implemented on the project: Mechanical Primary Sedimentation (MPS) Screens and the transfer of biosolids sludge through a pipeline for consolidated biosolids processing at St Marys.
Mechanical Primary Sedimentation (MPS) Screens
This is an emerging technology that delivers reduced power consumption and greenhouse gas emissions due to reduced aeration requirements in the bioreactor.
Pre-sedimentation takes place in a much smaller footprint, using few materials, odour control is more efficient, and the process is cost- effective.
Solids harvested in the MPS are anaerobically digested, producing biogas which can then be captured and converted into energy to offset operational energy demand.
Transfer of biosolids sludge through a pipeline for consolidated biosolids processing
The solid waste produced at the Quakers Hill WRP will be transported via an existing effluent pipeline to St Marys WRP, to provide the scale to beneficially recover the energy contained in the sludge.
This delivers reduced power consumption and costs, and a significant reduction in greenhouse gas emissions due to reduced aeration requirements of the anaerobic digester, as well as biogas production enabling energy recovery.
It is anticipated the energy recovery enabled by the anaerobic digester will allow for 70-90 per cent self-supply of electricity at St Marys, which is approximately 115,358GJ/year of biogas generating 13.3GWh of electricity.
There are also two process innovations being implemented on the project that are a first for New South Wales: Nereda Anaerobic Granulated Sludge (AGS) process and the Thermal Hydrolysis Process (THP). Nereda Anaerobic Granulated Sludge (AGS) process
The Nereda AGS process is fully automated, easy to operate with no moving parts, has low energy consumption and a small footprint. Clarifiers are not required for the AGS process – treated effluent is decanted after a very short settling period.
Therefore, substantially less concrete is used in construction, the footprint is much smaller, and the construction costs are substantially lower.
The AGS process also uses about 25-30 per cent less energy and a conventional membrane type bioreactor, delivering significant greenhouse gas reduction for the project.
The material savings compared to its base case will also result in about 25 per cent saving on concrete and steel. Quakers Hill WRP will have the largest installation of an AGS reactor in Australia, and the first in NSW.
Thermal Hydrolysis Process (THP)
This is a proven technology using steam or heat to break down biomass material prior to anaerobic digestion.
The sustainability benefits include enhanced energy recovery (increased biogas production), reduced sludge quantities and a reduced digester volume.
A drier cake and higher-grade biosolids would also be utilised closer to site, reducing transport costs.
The reduced volumes of biosolids transported for disposal is a significant sustainability benefit of the THP.
In addition, the THP results in a pathogen-free and stabilised biosolids product that can be applied directly to land with potential for further drying to fertiliser or biofuel pellets.
It also eliminates odour problems associated with the treatment of organic materials. With THP at St Marys, biosolids can potentially be reused within the Sydney basin, which would significantly reduce transportation.
Cutting down emissions and energy consumption
The Sydney Water spokesperson said the four innovative wastewater process technologies described will deliver significant energy and carbon savings for Sydney Water, and help pave the way to a more sustainable water services industry.
Energy and carbon forecast modelling for the project estimates that the Lower South Creek Treatment Program will achieve a reduction of 870,000 tonnes or 42 per cent of total greenhouse gas emissions during construction and across its 50 years’ operation.
This reduction includes embodied CO2 emissions from construction materials and treatment chemicals.
On-site renewable energy use is a core objective of the Lower South Creek Treatment Strategy, with the consolidated solids processing at St Marys implemented to allow for anaerobic digestion and energy recovery through a cogeneration plant.
With on-site thermal energy recovery and electricity generation, the project is able to self-supply more than 70 per cent of its electricity demand.
It was these outcomes that helped achieve the program’s IS rating, which is more impressive considering the IS rating was initially undertaken for this project only as a benchmarking exercise.
“The IS rating was an opportunity to benchmark Sydney Water’s sustainability performance with the wider industry.
This demonstrated our planning and design processes are robust. We identified and considered options, challenged thinking and past practices, and have ultimately adopted innovative wastewater treatment technologies that are more sustainable,” the spokesperson said.
“We are continually striving to find better ways of working so our customers are guaranteed world-class water and wastewater services.
Sydney Water will continue to monitor the cumulative effect these improvements have on our environment and the added benefit to our customers.”
What the highest rating ever achieved means for the wider water sector
The Lower South Creek Program is Sydney Water’s first project to trial the Infrastructure Sustainability Council of Australia’s IS Rating tool and certification process.
This process has provided independent third-party assurance of sustainability outcomes in the delivery of the project.
Ainsley Simpson, CEO of Infrastructure Sustainability Council of Australia, said, “This is the highest IS rating ever achieved for a water infrastructure project and includes numerous innovations and sustainable outcomes which other water utilities can follow and learn from. A tremendous achievement for Sydney Water.”
Sydney Water said it is focused on providing world-class water services to the Greater Sydney region while striving to minimise its impact on the environment, a feat achieved by continually challenging current processes and exploring new ways of operating.
“In order to do so, it’s important we continue to adapt and evolve, benchmark our current processes against the wider infrastructure industry and identify areas for further improvement, so we can gain insight into how things can be done differently,” the spokesperson said.
“This project demonstrates the benefits that can be achieved for an operator, the community and the environment when standard approaches are challenged, and new technologies and ways of thinking are embraced.
The project has proven how the investigation of opportunities in the feasibility and concept phase allows for thorough investigations to be undertaken to identify and implement the best solutions available on the market.”