Monitoring beach water quality

Find out how Beachwatch collects and tests water samples.

We monitor recreational water quality at swimming sites along the New South Wales coast to assess the level of faecal pollution. In urban areas, the main source of faecal pollution is human sewage. When sewage is detected the water may not be safe for swimming.

Samples of beach water in an esky on a bed of ice, with icebricks
Taking beach water quality samples from the water

 

We collect water samples in a way to avoid contamination (aseptic sampling).  We:

  • use sterile sample jars
  • don’t remove the lid of the jar until the sample is collected
  • fill the jar in a sweeping motion away from the sampler
  • replace the lid tightly, immediately after sample collection, ensuring there our fingers do not touch inside the jar

After water samples are collected, they are stored on ice in an esky to prevent bacterial die-off or growth, and delivered to the laboratory generally within 6 hours of collection.

Water samples are collected when the swimming site is in use, so sampling frequency and period varies between swimming locations.

  • At ocean beaches in the Sydney, Hunter, Central Coast and Illawarra regions samples are collected every 6 days throughout the year
  • At harbour beaches in Sydney (Sydney Harbour, Pittwater, Botany Bay, Georges River and Port Hacking) samples are collect every 6 days throughout the summer swimming season (October to April) and reduced to monthly surveillance sampling during Winter (May to September)
  • At beaches along the NSW coastline monitored under the Beachwatch Partnership Program samples are generally only collected during the summer swimming season.

We test water samples for a bacteria called enterococci. Enterococci is found in the intestines of warm blooded animals and excreted in faeces and rarely present in unpolluted waters. The bacteria is found in very high numbers in raw sewage which makes it a good indicator of sewage pollution.

Studies have shown a strong relationship between elevated levels of enterococci and illness rates in swimmers. It’s important to note that enterococci doesn’t cause illness, but its presence means there’s sewage in the water and, therefore, possibly pathogens, which do cause illness.

Indicator organisms are used to test for sewage pollution because:

  • they are easily detectable by simple laboratory tests
  • they are generally not present in unpolluted waters
  • results are available relatively quickly.

The National health and Medical Research Council (2008) Guidelines for Managing Risks in Recreational Waters recommend enterococci as the single preferred indicator organism for the detection of faecal pollution. Prior to 2009, we also tested for the bacterial indicator faecal coliforms . While this bacteria is also present in high numbers in raw sewage, it dies off more rapidly than enterococci in marine waters and has been found to correlate poorly with illness rates in swimmers.

While pathogens are the organisms that cause illness, we don't test for these organisms directly for a number of reasons:

  • Pathogens in sewage are generally present in lower numbers than the indicator organism (enterococci), which means large volumes of water need to be collected for testing.
  • The laboratory procedures are generally more complex, more expensive and take longer.
  • There are many pathogens that could be present in sewage, making it very difficult to choose which pathogen(s) to test for.

The water samples are tested for the bacteria, enterococci, in the laboratory. The laboratory uses a procedure called membrane filtration, which follows the Australian standards (AS/NZS 4276.9:2007).

Bacteria in petri dishesThe procedure involves:

  • filtering a precise volume of the water sample through a very fine membrane to capture any bacteria present in the sample
  • placing the membrane on a special gel which promotes the growth of the indicator bacteria (enterococci)
  • incubating the membrane for 24 to 48 hours during which the bacteria grows and multiplies many times, forming individual colonies that can be seen by the naked eye
  • the laboratory counts the number of colonies to determine the number of bacteria present (in the volume of sample filtered). If the plate is too crowded to count, another diluted water sample is analysed.
  • the results are reported as colony forming units per 100 millilitres of sample (cfu/100ml), and are generally available within 26 hours.

Because it takes time to grow the colonies, laboratory results are not used in the daily pollution forecasts, but are used for all other reporting.

The laboratories used in our Beachwatch and Beachwatch Partnership programs are included in a quality assurance program, and their performance is reported in our Annual State of the Beaches Report.

Confidence in our program

Our quality assurance program ensures that the information collected and reported by Beachwatch and our partners is accurate and reliable.

Our quality assurance program