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Water Pollution

Overview

Up until the early 1990's, the main source of pollution at Sydney's beaches was effluent discharged from the North Head, Bondi and Malabar wastewater treatment plants. Together, these plants discharged approximately one billion litres of primary treated sewage to Sydney's coastal waters each day. Between 1990 and 1992, deep ocean outfalls were built to discharge the sewage three to five kilometres off shore. Since then, the condition of Sydney's ocean beaches has improved dramatically.

The main cause of beach pollution in Sydney is now stormwater, which can carry pollutants washed from the catchment and overflows from the sewerage system. Bypasses from sewage treatment plants may also affect beach water quality.

People's activities at the beach can also cause localised beach pollution. Plastic litter, food scraps and fishing waste left by beach users can impact on beach amenity for a considerable time, particularly at busy times of year. Although local councils frequently collect rubbish and debris using mechanical rakes at popular beaches during summer, it is beyond the resources of most councils to 'tidy-up' after everybody and at every recreational beach in a municipality.

Wastewater from recreational boats, bilge flushing from coastal ships and other forms of dumping of ships' waste can also be a source of pollution of coastal waterways.

Compared to other countries water quality at Australian beaches is generally good. Information collected by the Beachwatch Program over the last 18 years shows that Sydney's beaches are now safe for swimming most of the time.

Stormwater

In urban areas, natural small creeks and drainage lines have been replaced with networks of canals and pipes. These networks are called the stormwater system which is designed to prevent flooding in urban areas and transport rainwater to larger creeks which then flows to our harbours and beaches.

When rain falls it can transport contaminants into the stormwater system. These pollutants include street litter, dog droppings, cigarette butts, leaf litter, oil and silt. Near the beach stormwater may be discharged directly onto the beach. Unlike sewage, stormwater is not treated. In some cases it's filtered through traps, usually located at the end of the pipe system, but it still flows directly from streets and gutters into our rivers, the harbour and the ocean.

In Australia, the stormwater system is separate to the sewerage system. However, sewage can enter the stormwater system when sewers become blocked or during wet weather when the sewerage system may overflow.

More information on stormwater can be found on the Office of Environment and Heritage website.

Sewage Overflows

Beneath Sydney is a vast (about 22,000 km) underground sewerage network, which transports wastewater from homes, businesses and industry to Sydney's wastewater treatment plants. Similar networks are found under most urban areas in Australia.

Overflows from the sewerage system can occur in dry weather due to blockages in the system caused by tree root intrusion or debris. Overflows can also occur during sustained periods of heavy rain when stormwater can enter the sewerage system through illegal connections and damaged pipes causing the capacity of the pipes to be exceeded.

To avoid raw sewage backing up into people's homes when the system is under pressure, overflow points have been installed to divert excess flows from the sewer into the stormwater system or directly into creeks. Dry weather sewage overflows tend to be smaller in volume but can result in significant localised contamination and associated increased health risks. Wet weather sewage overflows tend to be larger in volume, and even though the sewage is diluted by stormwater, can still result in widespread pollution of ocean and harbour beaches.

Under EPA licence, Sydney Water is required to notify the Office of Environment and Heritage of any sewage overflows which affect water quality. This information is also reported on the Sydney Water website. When Beachwatch receives a notification of an overflow in the vicinity of recreational waters, this is reported in the daily bulletin's website.

For more information on sewage overflows visit the Sydney Water website.

If you see an overflow, please phone Sydney Water on 13 20 90.

Wastewater Treatment Plants

 

Wastewater treatment plants collect sewage, remove solids and treat wastewater before its release to the environment. Treatment classifications range from 'primary' treatment which involves removing solids from liquid waste to 'tertiary', the highest level, which involves removal of solids, dissolved and suspended organic and inorganic solids, inorganic compounds, and substances such as the plant nutrients nitrogen and phosphorus. Disinfection, to kill pathogens, can also be added to all levels of treatment.

 

There are five coastal wastewater treatment plants in the Sydney region (Warriewood, North Head, Bondi, Malabar and Cronulla), four in the Illawarra region (Wollongong, Shellharbour, Bombo and Gerroa) and three in the Hunter region (Burwood Beach, Boulder Bay and Belmont). The largest of the coastal plants are located at North Head, Bondi and Malabar. Together, these three plants treat approximately 75 per cent of Sydney's sewage, discharging into the ocean through deep ocean outfalls.

More information on wastewater treatment plants and treatment processes can be found on the Sydney Water Corporation and Hunter Water Corporation websites.

Wastewater Treatment Plant Bypasses

Bypasses from wastewater treatment plants occur when sewage is discharged to the receiving water either without treatment or with only partial treatment. Bypasses can occur in dry weather due to a mechanical or electrical failure at the plant. Wet weather bypasses can occur when the capacity of the plant is exceeded owing to large volumes of stormwater in the sewage system. Bypasses can cause localised beach pollution.

Under EPA licence, Sydney Water is required to notify OEH of bypasses from its wastewater treatment plants. This information is also reported on the Sydney Water website. When Beachwatch receives notification of a bypass in the Sydney region, this information is included on the daily bulletin. In the Illawarra, this information is distributed as a media release.