History of wastewater treatment in Sydney
Sydney is located where it is today basically because of Captain Phillips’ discovery of what he thought was a viable water source for the new colony — the Tank Stream.
For thousands of years the stream was also a place of cultural significance to the Gadigal, the original traditional owners of the Sydney Cove area. The Tank Stream provided Aboriginal people with an important source of fresh water, food and resources for stone tools.
It took less than 40 years for the early settlers to pollute the Tank Stream so badly that by 1826 the colony was forced to find an alternative water supply. The settlers then used the Tank Stream as a drain and a sewer and in 1860 the pollution became so bad that the Tank Stream was covered in stone and the city grew up above it.
Until the late 1800s, Sydney’s sewage was largely discharged straight into its harbour. At that time, the Botany Sewage Farm (later to become Malar Treatment Plan) and Bondi Outfall System were commenced to remove sewage from the growing city. The third part of the large ocean treatment and disposal system came with the construction of the North Head system between 1916 and 1930. Over this period, sections of Sydney’s North Shore were sewered, providing for cleaner and safer local environments and providing marked property value uplift.
The three major wastewater ocean systems of Malabar, North Head and Bondi saw extensive sewage collection systems constructed. Today these systems collect and transfer almost 80% of Sydney’s sewage from as far west as Blacktown and as far southwest as Campbelltown to the coast for treatment and disposal.
Only half of Sydney’s households were connected to the sewer by the Second World War. This resulted in massive wastewater system investment in the second half of the 1900s.
The Hawkesbury-Nepean catchment in Sydney’s west saw a high number of intensive treatment plants built and modified to process sewage to remove nitrogen and phosphorus. Described as tertiary treatment, such plants required large footprints as well as high energy demand to meet stringent local discharge licence requirements.
As late as the 1950s the cliff-face discharge of sewage at Bondi, Malabar and North Head saw: poor beach water quality for swimmers, grease on the beaches, a significant visual impact of sewage, contaminants in seafood caught in the area and negative impacts on the near shore environment.
The state of Sydney’s coastline was unacceptable and the public demanded action.
In the early 1960s a submarine sewage outfalls concept was proposed, with a new Trade Waste Policy developed in the early 1970s.
Deep Ocean Outfalls were commissioned at Malabar, North Head and Bondi to ensure that Sydney’s beaches became some of the cleanest in the world. Malabar was the first to be commissioned in September 1990, followed by North Head and Bondi at a total cost to investigate, design, construct and commission of $310 million.
At the time, the hydraulic design of the Sydney Outfalls represented the leading edge of development for high dilution, self-cleansing and essentially maintenance-free outfall facilities.
Prior to the commissioning of the deep ocean outfalls, near the old cliff-face outfalls, values of faecal coliforms were commonly in the range 10,000–10,000,000 colony forming units (cfu)/100 mL. After the decommissioning of these old outfalls, median values fell to less than 10 cfu/100 mL.
Long-term monitoring has shown no evidence of any measurable environmental impacts from the deep ocean outfall discharges or of any build-up of metal concentrations in ocean sediments near the deep ocean outfalls.
A recent Deloitte Access Economics Report to assess both the economic and social value generated from improvements in water quality as a result of the deep ocean outfalls showed that:
- The Deepwater Ocean Outfall program delivered by Sydney Water 25 years ago has provided $2 billion of social value to Sydney residents attributed to the improved coastal beach water quality.
- The total value of Sydney’s coastal beaches to its residents is around $1.3 billion per annum, of which $130 million is attributable to water quality.
- The net value add associated with beach water quality is worth around $332 million per year to the NSW economy through domestic and international tourism and the provision of 3500 jobs.
- The health benefits associated with beach water quality due to the avoidance of illness of beach users is estimated at $140 million per year from avoided absenteeism, calculated from an estimated 180,000 sick days saved per year.
- In terms of biodiversity, the study suggests that changes in wastewater management, including the establishment of the Deep Ocean Outfall Program, have had a net positive impact on the biodiversity of marine communities along Sydney’s coastline, although this is difficult to quantify.
- In terms of brand value, the study found that beaches ranked in the top three when visitors think of Sydney — alongside Sydney Harbour and the Sydney Opera House.
Today, Sydney Water operates 30 wastewater treatment and water recycling plants that treat over 1.5 billion litres of wastewater every day. There are over 25,000 km of wastewater pipes in Sydney Water’s wastewater network.
The water recycling plants treat wastewater, which can then be safely used to water gardens, golf courses and parks, flush toilets, wash cars and fight fires. The recycled water can also be used for some industrial purposes and to supplement river flow in the Hawkesbury-Nepean River. This saves water stored in dams for drinking and keeps the river healthy.
Sydney Water has invested hundreds of millions of dollars in the recent past into its wastewater treatment plants to reduce odour for local residents and to improve environmental outcomes.
Environmental advances
Sydney Water extracts over 170,000 tonnes of biosolids fertiliser from the wastewater treatment process each year, which is provided to NSW farmers to improve soil condition and to fertilise animal feed crops.
Treatment of sewage creates methane gas, and through a process called anaerobic co-digestion, the obtained methane is used as fuel to heat anaerobic digesters and to produce electricity to power the plant. The entire process occurs in a contained system to eliminate any odours.
This creates a number of benefits by taking pressure off the electricity network and by reducing greenhouse gas emissions.
Sydney Water currently generates more than 20% of its total energy needs across its network. It also exports eight gigawatt hours (GWh) to the electricity grid over a year — which would power around 1000 homes.
Sydney Water is producing on-site across all its wastewater treatment facilities enough energy to power over 11,000 homes each year, reducing greenhouse gas emissions by over 70,000 tonnes a year — the equivalent of keeping 17,500 cars off the road for a year.
Sydney Water is aiming to keep its total electricity purchases below 1998 levels, even though it is servicing an increasing population and providing higher treatment standards.
Sydney Water’s Bondi Wastewater Treatment Plant now produces 13% more electricity than it consumes each year, allowing the return of electricity to the grid.
Innovation
Sydney Water is also currently trialling the use of other organic waste products to further increase the ability to produce additional power and to reduce landfill and costs for third-party stakeholders.
A trial is being conducted to use fruit and vegetable waste at its Cronulla Wastewater Treatment Plant, and in collaboration with the University of Wollongong, an innovative research project is being undertaken at the Shellharbour Wastewater Treatment Plant, investigating other food waste sources which can be used to generate additional renewable energy production.
“The first stage of the project is using waste from beverage production, so we are basically turning beer, wine and soft drink waste into power,” at Sydney Water Principal Scientist, Treatment Dr Heri Bustamante said.
“Adding food waste like beverage waste to the wastewater treatment process provides a number of benefits:
- More power is able to be generated by the co-digestion process through additional biogas production.
- Food waste is diverted away from landfill.
- Greenhouse emissions are reduced.
- Producing green energy at the treatment plant keeps the operation costs of the treatment plant lower, which in turn puts downward pressure on water bills for customers.
“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,” Dr Bustamante said.
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Provision of wastewater infrastructure has been the real backbone that has supported the healthy growth of all large cities over the millennia.
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