Climate change and growing human populations will put pressure on water systems everywhere. In a large city like Sydney, supplying 4.3 million people with fresh water, and carrying away their wastes, is already a complex task. As the climate changes, and the population grows, we’ll rely more on a variety of water sources, including dams, desalination and recycled wastewater. No matter where it comes from, water is water and it’s up to us all to make the most of every drop. In Sydney every person uses about 300 litres of water per day for a range of purposes. This situation presents huge opportunities for us to develop innovative water technologies.
The Managed Water Cycle
The managed water cycle involves people and industry, catchments, rivers, dams, reservoirs, freshwater pipes, water filtration plants, wastewater pipes, water recycling plants, and stormwater drainage and recycling.
What happens to drinking water?
Before water gets to our homes it undergoes a series of processes to remove impurities and make it healthy to drink. In Sydney, water filtration plants treat water that’s come from dams and rivers, and one desalination plant extracts fresh water from sea water. Water is pumped straight into the pipe network or to a reservoir where is is held or needed in your home.
Sydney’s dam supply is one of the largest in the world. Dams store water from rivers and from rain as it runs off hills in a water catchment. There are five catchments and 21 dams within the Sydney, Blue Mountains and Illawarra regions. The Sydney Catchment Authority manages these and supplies water to Sydney Water for treatment and distribution.
Water filtration plants
Dam water is treated at water filtration plants to improve its quality and meet health guidelines. The water is filtered to remove particles, disinfected and fluoride is added. This makes it safe to drink. There are nine water filtration plants in Sydney Water’s network. The largest plant at Prospect treats more than 80% of Sydney’s water. Treated water is sent to reservoirs where it’s stored until it’s needed.
Some reservoirs look like tanks, others like small dams. They’re usually located on hills so water can flow downhill to homes and businesses. This reduces the electricity needed for pumping. Water gets to your home through a network of about 21,000 km of water mains, 263 reservoirs and 162 pumping stations. Today’s water pipes are usually made of concrete or plastic, which are more flexible and less prone to cracking.
A desalination plant turns seawater into drinking water. Desalination is important because it does not rely on rainfall. It currently provides 15% of Sydney’s water needs. Seawater is pumped from the ocean and pushed through very fine filters under high pressure so only fresh water is left. This process is called reverse osmosis. The water is then treated to the same quality as dam water, making it safe to drink. Sydney’s desalination plant is powered by 100% renewable energy from a 67-turbine Capital Wind Farm at Bungendore, NSW.
Water from the desalination plant is mixed with water from dams before being delivered to households and businesses.
Sydney has 21 000 km of water mains that carry fresh water. Weather conditions can cause soil to expand and contract, causing cracks and leaks in pipes. Ageing pipes, accidental damage and sudden changes in water pressure can also cause leaks. All large cities, especially those that have grown over hundreds of years, have the same problem. Technicians use acoustic and electronic equipment to find and repair hidden leaks. Replacing old pipes, reducing pipe pressure and placing meters on the pipe system to detect leaks also helps.
Constant testing and monitoring of the drinking water supply is very important. Keeping contaminants out of drinking water catchments, and removing those that get in, keeps our water supply safe. Water is tested for up to 70 characteristics at every stage of the supply system and at 650 customers’ taps. Water quality testing in Sydney currently meets or exceeds international standards of safety and acceptability. This testing schedule shows where and how frequently water is tested.
Testing for Acid
The pH of water is the measure of its acidity or alkalinity. A neutral solution has a PH of 7. The pH scale ranges from 0 to 14, with lower numbers indicating higher acidity, and higher numbers indicating alkalinity. The best pH for fresh water is near neutral at 6.5 to 8.2. Acid comes from rocks, decaying plants or urban pollution. Alkalinity comes from detergents and soaps.
Testing for micro-organisms
It is possible for micro-organisms to be carried from the catchment into dams. Filtration and disinfection removes them, but water is routinely tested for bacteria and other micro-organisms to be certain that the water supply is safe for everyone to drink.
Esherichia coli (E. coli) is a very common bacteria found in the guts of warm-blooded animals. These bacteria can survive for brief periods outside the body so can be used as an indicator of faecal contamination in water. Most E. coli are harmless but some types can cause stomach upsets. They are removed from the water by filtration and disinfection (such as chlorine or chloramine).
Cryptosporidium is a micro-organism that occurs in the guts of infected warm-blooded animals, and can enter the water supply through contact with infected droppings. It can cause diarrhoea. The body’s immune system must fight it off, which it usually does in 1-2 weeks. Cryptosporidium is removed from drinking water in the filtration process.
Blue-green algae (cyanobacteria) include a range of single-celled bacteria that can multiply rapidly to form large groups called an ‘algal bloom.’ They flourish in water that is still, warm and rich with nutrients like phosphorus. Blure-green algae can produce harmful toxins. The cells are removed by water filtration, and the toxins are destroyed by chlorine disinfection.
Giardia is a single-celled microbe known as a protozoan. It lives in the guts of infected warm-blooded animals, and reproduces via egg-like cysts that pass out in their poo. Water contaminated with Giardia can result in abdominal pain, diarrhoea, nausea and tiredness. Giardia is removed by filtration and destroyed by chlorine disinfection.
Checking for water insects
Insects can be good indicators of water pollution so they are monitored regularly. Some insects (macroinvertebrates) can live in polluted water. Others are more sensitive and cannot survive. This makes them very good indicators for the health of a waterway. If they’re absent, it’s likely there’s a problem. These insects are graded according to their sensitivity to pollution.
Once water passes through our homes and industries it becomes part of the waste water stream. In Sydney, waste water is treated as a valuable resource and cleansed for multiple purposes.
Treating waste water
Sydney Water operates wastewater treatment plants that clean water from homes and businesses. The plants produce highly treated water that can be returned to the ocean or recycled for use in industry, irrigation or for non-drinking purposes in homes.
Water recycling plants take cleaned wastewater from wastewater treatment plants and clean it further so it can be reused. How much it’s treated depends on what it’s going to be used for. More than 19 000 homes in the Rouse Hill area of Sydney use recycled water to flush toilets, water gardens and wash cars. This is one of the largest residential recycling schemes in Australia.
Stormwater is rainwater that washes over roads and parks picking up dirt, oil, litter, fertilisers, and heavy metals. Because it contacts these things, stormwater is really hard to clean. Many authorities use litter traps, wetlands and sedimentation basins to improve the quality of the water on its way to rivers and the ocean. Stormwater is also captured, treated and reused for non-drinking purposes like cleaning streets, flushing toilets and watering local sportsgrounds. There are 70 stormwater projects across greater Sydney that save about 1.3 billion litres of fresh water a year.
Look for purple taps
Wastewater and stormwater are both recycled and delivered for use in homes and businesses via special lilac-coloured pipes. In areas where recycled water is used, new houses have ordinary taps for freshwater and lilac ones for non-drinking purposes.
Planning for the future
Sydney Water is working with the Bureau of Meteorology and other water authorities to create the country’s first national database of water information. The database will create a valuable nation-wide view of rainfall patterns, water stores and usage that will help water authorities make informed decisions on water policies and infrastructure. It will help with long term planning and improve the Bureau’s ability to forecast and provide warnings about droughts and floods.
The history of Sydney’s managed water supply
Erratic rainfall and growing populations have been the two driving forces in the development of Sydney’s water supply. They will no doubt continue to drive innovations in water treatment and use in future years.