There is evidence that could survive in the water for days. The last few months, sewage water testing has been used to track down Coronavirus in Europe: The scientists working on that field think that the wastewater testing could be crucial to detecting a second wave or local spikes of SARS-CoV-2 in a very early stage.
Even though the virus is already dead by the time it gets to the wastewater treatment plant, it can still be detected in the sewage: they test for the genetic signal of the virus (RNA) which is correlated with the presence of the virus. It can’t be used by the sanitary authorities as a key information in the decision process, but it can be used as a supplement information, providing an early warning.
In Germany, some wastewater treatment plants are equipped with automated sampling extractors taking samples 365 days a year for testing the sewage coming into those plants. This sampling tests allow scientists to determine the concentration of the virus in the wastewater and conclude how high could be the level of the infection within a community. When things are normal, the level drops. If there is a second wave, the level rises, and it can be observed weeks before the first clinical cases emerge. The sampling can even be optimized so different areas, or regions can be monitored. In addition to that, it is possible to rebuild the timeline and determine when a virus has started circulating within a community. For instance, in Northern Italy, the SARS-CoV-2 was found in the wastewater since December 2019, weeks before the first clinical diagnosed case.
It is important to underline though that there is no evidence of Coronavirus oral transmission from the sewage or sense of a threshold level that would be of concern.
Source: DW News https://www.youtube.com/watch?v=DqemeEFBceU&t=186s