Wastewater surveillance enables wide-area monitoring

Wastewater surveillance allows the authorities to detect the presence of the Covid-19 virus at a location. This can then be followed up with clinical tests.

Some 95 locations islandwide currently have their wastewater surveyed, including the four water reclamation plants, workers' dormitories, nursing homes and hostels.

The National Environment Agency (NEA) said: "Monitoring is carried out at the water reclamation plants to provide situational awareness of the Covid-19 situation in Singapore, while wastewater sample collection at high-density-population (locations)... provides an additional surveillance indicator for Covid-19, in addition to clinical testing regimes."

It said the frequency of sample collection varies from site to site and depends on the purpose of surveillance.

NEA said that at the National University of Singapore, it collaborated with the university and provided inputs on the wastewater testing protocol and interpretation of the sample results.

NEA will continue to support NUS in the interpretation of the results as tests are conducted on the samples, said the agency.

Samples are collected by autosamplers, programmed to collect them as required. They are then transferred to the laboratory and processed.

As an example, NEA cited workers' dormitories where clusters had been reported.

A zero reading for viral material in the wastewater gave added assurance that these dormitories remained free of Covid-19. But if any was detected, swab tests were carried out on workers to facilitate detection and isolation of cases.

"The passive, wide-area surveillance capability of wastewater sampling therefore enables us to unobtrusively monitor for Covid-19, in conjunction with community clinical tests," said NEA.