Changes

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</ul></div>Beyond the supplying and processing guarantees, the Ministry for the Ecological Transition and the Demographic Challenge, together with the Ministry of Health, followed the recommendations from the European Union on the systematic surveillance of SARS-CoV-2 (EU, 2021) by launching an early-warning system based on monitoring the virus in urban wastewater (VATar COVID-19). As a result, traces of the genetic material of the virus in urban wastewater were detected and could be linked to COVID-19 cases. For this reason, the presence of coronavirus in wastewater is regarded as an early epidemiological indicator that may help anticipate, detect and monitor the spread of the disease and any possible spikes in incidence, alongside the traditional monitoring of patients with COVID-19. This coronavirus monitoring task involves analysing data from wastewater processing plants in all Spanish river basin districts, prioritising those containing effluents from hospitals, tourist areas and airports. The reclaimed water used in municipalities with insufficient processing and stretches of rivers, lakes and reservoirs used for bathing were also analysed to study the possible effects of the virus in these types of waters (Ministry for the Ecological Transition and the Demographic Challenge, 2021).

The presence of coronavirus in wastewater was first confirmed in the week starting on 19 July 2020, as shown on the map on the ''[[:File:Trends in wastewater pollution by SARS-CoV-2|Trends in wastewater pollution by SARS-CoV-2]]''. Results are quantified as genomic copies of SARS-CoV-2 per litre (cg/l) and then transformed to a logarithmic scale (log10 cg/l). For twelve weeks after this date (until 10 October 2020), there were significant weekly increases in the presence of the virus in wastewater in all cities (over +1 logarithmic unit), although the timing of the peaks differs. The peaks in Barcelona (weeks 8 and 11), Valladolid (weeks 5 and 9) and Oviedo (weeks 4 and 9) are remarkable. Interestingly, however, the results from Málaga did not register an increase of the virus in its wastewater until week 10. It is important to note that the Ministries responsible warn that point-in-time data are subject to variations in environmental conditions or changes in sampling times and shall, therefore, be taken into consideration with some caution. However, it is relevant to look at how the weekly trends correlate with the evolution of the health situation.

Data on water consumption during lockdown and the subsequent downscaling phases are also interesting. These figures show the decline in economic activity in line with data on electricity, petrol, diesel and natural gas consumption. The graphs show the evolution of water consumption by households and by the industry in the city of Seville (Sevilla) from January to July 2019 and 2020, as per the data provided by Seville Metropolitan Water Supply and Sanitation Company (EMASESA). Figures show that water consumption by households rose slightly from February 2020 and peaked at 2,700,000 m³ in March, simultaneous to the state of alarm and lockdown. Conversely, there was a significant drop in industrial consumption, which fell by 40% in April and May 2020. The data on hourly water consumption by households reveal no differences in the breakdown by daytime and night-time, whereas some changes related to different day and night-time tariffs may be detected in figures on water consumption by the industry.

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