Researchers at the Spanish National Research Council (CSIC) and the University of Valencia have developed a molecular analysis system that can alert to the circulation of the coronavirus SARS-CoV-2 (which causes the Covid-19 disease) in a community, based on the study of wastewater. The analysis system, which could prove useful as an epidemiological surveillance method, has been tested at six wastewater treatment plants in the Region of Murcia and a further three WWTPs in the metropolitan area of Valencia. The studies carried out have demonstrated that the disinfection treatments applied at the plants are effective in eliminating the virus.
The new analysis system has been developed by researchers at two CSIC centres and a joint University of Valencia and CSIC centre. In Valencia, the studies have been carried out by researchers at the Institute of Agrochemistry and Food Technology (IATA-CSIC), led by Gloria Sánchez and Walter Randazzo, and at the Institute for Integrative Systems Biology (I2SysBio), a joint CSIC and University of Valencia research centre, led by Pilar Domingo-Calap and Rafael Sanjuán. The studies in the Region of Murcia have been carried out by the IATA team of Sánchez and Randazzo, along with a team led by Ana Allende and Pilar Truchado from the Segura Centre for Edaphology and Applied Biology (CEBAS-CSIC).
In the Region of Murcia, the study was implemented by the Entidad de Saneamiento y Depuración de Aguas Residuales en la Región de Murcia (ESAMUR), which is responsible for wastewater treatment in the region, in collaboration with the IATA-CSIC and CEBAS-CSIC research teams. “The research teams have been taking samples since March 12. Since then, over 60 samples from different points of the six WWTPs in the region have been analysed, including plant effluent and the effluent from secondary treatment. The aim was, first of all, to determine if the SARS-CoV-2 coronavirus was present in the wastewater and, then, to test the effectiveness of the disinfection treatments implemented at the WWTPs”, explains Ana Allende, a researcher from the CEBAS-CSIC.
In Valencia, these studies have been carried out in cooperation with the Pinedo 1 and 2, and Quart-Benàger WWTPs, which belong to the Department of Agriculture, Rural Development, Climate Emergency and Ecological Transition of the Regional Government of Valencia. The researchers are analysing more WWTPs in the Autonomous Community of Valencia, as well as samples taken on different dates prior to the first patients testing positive for Covid-19 in Spain. “The goal is to establish this type of analysis as an epidemiological surveillance method. Detecting changes in the presence of the genetic material of the virus in urban wastewater over time will give us information on the prevalence of the virus in the population and its progression”, points out Pilar Domingo-Calap, a researcher from the I2SysBio team.
In carrying out the study, the researchers implemented methods that had been previously optimised by the IATA-CSIC for the detection of foodborne viruses. “The results obtained to date with molecular techniques, using samples from last week, show concentrations of approximately 100,000 copies of genetic material of the virus per litre of wastewater”, explains Gloria Sánchez, from the IATA-CSIC research team. These levels are comparable to those obtained in the United States. Recent studies carried out in the Netherlands and China have also detected the presence of SARS-CoV-2 in wastewater. The study has demonstrated that the disinfection treatment carried out at the WWTPs eliminates the virus.