COVID-19 Wastewater Testing FAQs

Last Updated: 15 Apr 2021 11:54am


A wastewater testing program has been established in Tasmania as part of our active surveillance for COVID-19. The Tasmanian Wastewater Testing Program will collect samples of untreated sewage (wastewater) from sites across the State.

Wastewater is all the used water coming from buildings that passes through the sewage system and includes water from toilets, showers and baths, basins and sinks, and laundries.

Many pathogens (‘germs’) are present within wastewater. There has been routine monitoring for some infectious disease pathogens in wastewater, such as poliovirus, performed around the world for many years.

It is possible to detect the presence of fragments of the virus that causes COVID-19 in wastewater (these are called ‘viral fragments’).

Knowing where these viral fragments are provides clues to the geographical areas people are in, or have recently been in, whilst shedding the virus.

When someone is sick with a virus, their bodies release virus particles, which are then shed into the environment. This process is called viral shedding.

For people who have, or have recently had, COVID-19, the virus is shed in respiratory secretions (snot, mucus, phlegm) when they talk, cough, sneeze or even when they breathe out. The virus can also be shed in a person’s faeces (poo) too.

It can take many weeks for someone to stop shedding the virus and they can continue to shed the virus even when they are no longer infectious to others.

When the virus is shed in faeces it can be flushed down the toilet or respiratory secretions can be washed off hands or skin and passed down the basin, shower or bath. When the virus enters the wastewater system, it breaks apart into ‘viral fragments’ and it is these fragments which are tested for in the Tasmanian Wastewater Testing Program.

To detect viral fragments in wastewater, untreated sewage – meaning sewage that has not yet entered a wastewater treatment facility (known in Tasmanian as Sewage Treatment Plants or STPs) - is collected. These samples are transported to a laboratory and tested for viral fragments. This is a specialised test with only a small number of laboratories able to perform the test. Tasmania’s samples will be sent to the Australian Water Quality Centre (AWQC) in South Australia for testing. Work is underway to establish a testing service in Tasmania. The Tasmanian Department of Health is working closely with a number of organisations locally and other jurisdictions to ensure a high standard of timely testing can be performed.

It is not completely understood how long the viral fragments persist in untreated sewage but it is known that their survival depends on a variety of conditions, including the temperature, other pathogens, and the amount of organic matter available. It is important to note that the virus that causes COVID-19 is easily inactivated (‘killed’) by detergents which are also present in sewage (from hand washing at basins, dish washing, etc.).

Sampling sites are selected by the Department of Health based on many factors including population size, location and ability to access samples. The wastewater testing program is adaptive and the main aim is to provide the most useful data in the context of the Tasmanian COVID-19 response.

How often will samples be collected and tested?

Samples will be collected on either a weekly or monthly basis. Testing of samples will occur on a weekly basis. It can take up to 7 days from when a sample is taken to receive initial laboratory results.

Results will be published on the Coronavirus Website each week at coronavirus.tas.gov.au.

In the event of a positive test, the Department of Health will provide advice to impacted communities and stakeholders through a range of channels, so everyone is aware of what the result means and what they need to do in response.

A positive result from wastewater sampling means that fragments of the virus that causes COVID-19 have been identified on testing. This result may be due to:

  • A person or people with COVID-19 being in the infectious phase of the illness.
  • A person or people who are no longer infectious but who are continuing to shed the virus.
    • The person or people whose waste contributed to the positive result may be local or visitors. They may no longer be in the area, so a positive result does not necessarily mean there are cases of COVID-19 in the community.

An inconclusive result occurs when there is a very weak detection of viral fragments that cannot be confirmed by further analysis. This is most likely due to someone continuing to shed the virus who has previously had COVID-19 and is no longer infectious. An inconclusive result is less likely to require a Public Health response, unless there are other reasons to believe COVID-19 might be present in the local community.

A negative result from wastewater sampling means that there have not been any viral fragments of the SARS-CoV-2 virus found in testing that particular sample.

What does an inconclusive result mean?

An inconclusive result occurs when there is a very weak detection of viral fragments that cannot be confirmed by further analysis. This is most likely due to someone continuing to shed the virus who has previously had COVID-19 and is no longer infectious. An inconclusive result is less likely to require a Public Health response, unless there are other reasons to believe COVID-19 might be present in the local community.

If  fragments of the virus that causes COVID-19 are detected, the next steps will depend on whether the detection is consistent with recent clinical testing results in that area and the current context in Tasmania.

Steps may include

  • Listing the results on the Coronavirus website
  • public health messaging to encourage testing for COVID-19 and reminders about hygiene practices and other precautions.
  • Increasing testing capacity in the area affected

The Response Team will liaise with key stakeholders - such as councils, businesses, schools, medical practitioners - in impacted areas to support the Public Health response.

No matter where you are in Tasmania, it is important that anyone with symptoms of COVID-19, even if mild, gets tested.

The Tasmanian Department of Health is overseeing the wastewater testing program. A Response Team will be set up to guide the public health response if a positive wastewater detection occurs. This team will include representatives from Tasmania’s Public Health Service, the Department of Health Environmental Health Unit and Tasmanian Health Services.

Tasmania is joining a number of other Australian States and Territories who are all participating in the national ColoSSoS project (Collaboration on Sewage Surveillance for SARS-CoV-2) which is coordinated by Water Research Australia. This project brings together health departments, water utilities, laboratories, and researchers from Australia and New Zealand to share knowledge and experiences from this evolving field. There are also a number of similar active wastewater monitoring programs in countries around the world.

No. Wastewater is treated to kill a variety of microorganisms, including viruses, before it is returned to the environment. There is no evidence that the virus causing COVID-19 can be spread through wastewater, either before or after treatment. The viral fragments themselves are not infectious.

Wastewater testing and results do not reflect the quality of your local water supply.