Update COVID-19 Sewage research

When the coronavirus first reached the news at the end of last year, the microbiologists at KWR Water Research Institute started developing a measurement method to monitor sewage water. It was clear to them that sewage water would be a vital place to measure the presence of RNA traces of the virus, which would come from the faeces of infected people. When the hotspot appeared in Italy, we began collecting samples in several wastewater treatment plants (WWTPs) in the Netherlands in order to test the method.

We analysed the wastewater at a series of treatment plants in the Netherlands: large ones (Amsterdam-West), obvious ones (airport Schiphol) and peripheral ones (Terschelling, about which more below). In early February we found no traces, but, in the following measurement series, on 5 March, the first indications appeared. These became even more evident in the samples taken on 16 March. On Monday, 24 March, we put our sewage research results online.

Rapidly sharing research method with the world

Even before COVID-19 patients appeared, the sewage data (first from Amersfoort and then, last week, from Terschelling) made it clear that the virus was present in the population. Under normal circumstances, the validation (and subsequent publication) of the method used by the KWR researchers would require a lot more measurements and data than we were able to produce in such a short period of time. Because we recognise the great importance of sharing knowledge, and given the huge interest of the broad national and international scientific community, we published the experimental method in a scientific journal as quickly as possible. That happened on Monday, 30 March. On Friday, 3 April, Nature reported our research.

Testing above- and underground

On Sunday, 29 March, we sent our research proposal to the National Coronavirus Crisis Team (situated in the Ministry of Infrastructure and Water Management) to take measurements at all wastewater treatment plants in the Netherlands over a long period. On 1 April, it transpired that RIVM (National Institute for Public Health and the Environment) had also taken measurements at WWTPs during the same period that we had. The two independent studies – fortunately – reached the same conclusion: yes, RNA traces of the coronavirus were indeed present in the wastewater. And, no, no traces were found in the treated wastewater that we had analysed. In its sewage research (including the monitoring of drug use), KWR works closely with the Dutch Water Authorities (and their association) – which, after all, are in charge of the wastewater treatment plants – and with their research institute, STOWA; KWR also shares its research results with RIVM.

We are happy to work together with RIVM. The sewage data collected by KWR help provide a better understanding of the spread of the virus and constitute a valuable complement to RIVM’s measurements; both above-ground (the number of registered COVID-19 patients), and underground (the circulation of the virus among the entire population, including people who are not tested).

What does sewage tell us about the coronavirus?

When someone, for instance a nurse in a hospital, is tested for the coronavirus, the test method used is the same one that KWR researchers use in their sewage analysis. Above-ground, one test is required for one person. In the case of sewage, one test is sufficient to determine whether an entire population is infected with the coronavirus. The advantage of this method is that it is very specific and sensitive. We test whether the virus is circulating in a city or municipality, not who is or who is not infected within that population.

The significance of sewage research is that if it is done regularly over a long period (we have a weekly frequency in mind, in a large and representative number, for instance, in a hotspot or even where no corona patients have been reported), we can determine whether the coronavirus is slowly disappearing in the population (‘flattening of the curve’) and whether – presumably in the winter – it is returning. In early February, we noted that the sewage flashed ‘red’ before patients above-ground showed any signs of the coronavirus.

Safety above all

Two safety risks had to be quickly excluded.

As an additional precaution (but also for scientific purposes), in the case of two WWTPs we also tested the plant’s clean effluent, which is discharged into surface water (usually a river). We found no traces of the coronavirus in the effluent. This means that there are no traces of coronavirus in river water.

1 – Safe working conditions at WWTPs

The second important safety risk concerns the employees at the wastewater treatment plants. Are they adequately protected against the coronavirus in the inflowing dirty sewage water? The association of the Dutch Water Authorities and STOWA consulted early on with RIVM and agreed that the risk that WWTP employees run of becoming infected with COVID-19 through contact with the sewage water (aerosols) was very low. In this regard, STOWA’s website contains the following safety prescription:

When working with wastewater, employees are required to take the protective measures described in the Occupational Health and Safety Catalogue of the Water Authorities (part 5) ‘Handling biological agents’  (in Dutch). Best practices for the health protection of employees in the area of sanitary facilities must be followed, including the use of appropriate personal protection equipment (protective clothing, gloves, boots, protective glasses, mask and/or FFP3 respirator face mask). In addition, employees must pay strict attention to hand hygiene, and not touch their eyes, nose or mouth with unwashed hands. This is consistent with the general hygiene recommendations on protecting oneself again the flu and colds, such as hand washing.

NB. These requirements have not been changed since the detection of SARS-CoV2 in sewage water.

2- Drinking water is safe

On the basis of the knowledge built up by KWR researchers over recent years about viruses in water, we know that drinking water in the Netherlands is well protected against viruses that are known to be waterborne, such as the Adeno-, Noro- and Enterovirus. We have let the drinking water utilities, and their branch association Vewin, know that drinking water is very well protected against all viruses,

Drinking water utilities that produce their water from surface water sources have all have set up multiple disinfection barriers for the purpose of removing bacteria, viruses and protozoa. These disinfection methods are safeguarded by the Analysis of Microbial Safety of Drinking Water. Groundwater is well protected in the subsurface against all microbial contaminants, including viruses. Lastly, the strict hygiene regulations covering the installation of pipes and work on the distribution networks ensure that the drinking water sector is well protected against all microbial contaminants.


International attention

It is often said that the coronavirus knows no borders. All countries in the world are facing the pandemic. This means that water scientists all over the planet – and also all professionals working in the wastewater sector – are doing their utmost to find methods to monitor the coronavirus. Because it is not feasible to test every individual for the coronavirus, sewage water monitoring provides a tool to determine the ‘situation’ of populations (a province, a city), and gives managers (the cabinet, or a municipal council) a basis upon which to take possible additional precautionary measures or, at some point, decide on an ‘intelligent’ lifting of the lockdown.

Comparing sewage data with patient data

As a result of the drugs in wastewater research that KWR has been conducting for almost ten years, we know what a specific volume of pure cocaine found in a city’s sewage water represents in terms of street value ‘lines of coke’. Similarly, we also want to know what a specific volume of coronavirus traces in the sewage represents in terms of the number of infected individuals in a city. We also want to further characterise the viruses that we find in sewage water, so as to compare them with types that are present in the population. To this end, we share our results with RIVM and also with the Erasmus MC.


Video – 01:17
What we learn about the Corona virus through waste water research