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From manhole to sampling bottle: How wastewater helps indicate presence of COVID-19 in foreign worker dormitories

From manhole to sampling bottle: How wastewater helps indicate presence of COVID-19 in foreign worker dormitories

A team from the National Environmental Agency's (NEA) Environmental Health Institute demonstrates how wastewater samples are collected. (Photo: Jeremy Long)

SINGAPORE: It takes two keys and as many members of the team to prise open the hefty manhole cover. Sometimes, more hands are required.

Clad in their personal protective equipment - waterproof boots, two layers of clothes, N95 masks, face shields and double layers of gloves - the team from the National Environmental Agency's (NEA) Environmental Health Institute is searching for clues which could potentially point to the presence of the COVID-19 virus in a dormitory metres away from where they stand.

Part of a pilot programme launched by the NEA and supported by the National Water Agency PUB and Home Team Science and Technology Agency (HTX), this sampling of wastewater is used to support monitoring and management of COVID-19 transmission among workers living in dormitories. 

"Monitoring wastewater for COVID-19 allows us to understand the situation in the community (where it is) being sampled," said Dr Judith Wong, a research scientist at the Environmental Health Institute, on Wednesday (Jul 22).

READ: More wastewater testing under way in Singapore to tackle COVID-19; pilot launched at foreign worker dormitories

"We know that infected persons shed the virus in stool and wastewater receives stool as well as other respiratory discharges such as sputum and nasal aspirates. 

"So monitoring wastewater for the virus allows a non-invasive approach to understand the COVID-19 situation and this is independent of clinical testing regimes as well as the health-seeking behaviour of a population."

Upon lifting the manhole cover, the team inserts a rubber sampler tubing which will  typically help collect between 200 to 800ml of wastewater. This wastewater is pumped into an autosampler. 

The autosampler is programmed to collect the samples over a period of time and after the samples have been collected, the team will transfer them into sampling bottles which will be transported to the laboratory for testing.

The entire process can take between 30 minutes to up to three hours depending on factors such as whether the site designated for the extraction of the sample is suitable.

Samples will be then processed in the laboratory and testing is done to detect whether SARS-CoV-2 material is present in wastewater. SARS-CoV-2 is the virus that causes COVID-19.

The methodology for wastewater sampling and testing for COVID-19 was developed by the Environmental Health Institute, with scientific input from the Singapore Centre for Environmental Life Sciences at the Nanyang Technological University, Singapore-Massachusetts Institute of Technology Alliance for Research and Technology and the National University of Singapore.

"This methodology has been used to support the national effort in infection control and prevention of COVID-19," explained Dr Wong. 

"It is used to complement the existing swab strategy at the dormitories. For example, when we monitor the virus signals in the dormitories ... we are able to understand or not whether infection control measures have been effectively carried out."

After the samples have been collected, the team will transfer the wastewater into sampling bottles which will be transported to a laboratory for testing. (Photo: Jeremy Long)

In a dormitory with no known transmission of the virus, if no virus signals are detected in the wastewater, this provides an "added assurance" that the dormitory is clear from infections, Dr Wong added. 

"However, if virus signals are detected in this dormitory, it will then prompt appropriate follow-up measures such as swab testing of the population to allow us to identify the infected migrant worker," said Dr Wong. 

"Thereafter, it will allow appropriate medical care to be given and also for the case to be isolated to prevent future transmission."


As a group, migrant workers living in dormitories in Singapore have been the hardest-hit by COVID-19, making up the vast majority of the 48,744 confirmed cases as of Jul 22. 

The pilot programme began in April and has since been expanded to more than 30 dormitories so far. About 20 personnel are deployed in various roles ranging from collecting samples to working in the laboratories, said Dr Wong.

A team which typically consists two to three personnel are deployed to between six and eight sites per day. 

Manholes selected by the team need to be located away from the public, not along a main road or a pedestrian walkway, and need to contain the wastewater from the community that scientists plan to test.

"It's quite exhausting, it's quite hot. We go through the heat, the weather, even the tiredness of opening the manholes and so on," said Dr Wong. 

"But our team is really motivated by the positive contributions that it can bring to the community." 

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Source: CNA/mt(rw)


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