Impact of Pandemic COVID-19 on Air Quality at a Combustion Plant and Adjacent Areas

Following the emergence of the infectious disease COVID-19, caused by the coronavirus SARS-Cov-2, the WHO (World Health Organization) declared a pandemic in March 2020. The pandemic has affected people’s health, social behaviour, and the economy around the world. It has also had an indirect impact on the environment, including atmospheric air quality, related to changes in the levels of pollutant emissions and the amounts of greenhouse gases released into the atmosphere. The observed changes have, in part, been a consequence of restrictions on human movement, which has translated into an increase in water consumption, and consequently into an increase in the volume of wastewater. As a result, a new type of incoming load has appeared in sewage treatment plants. Municipal sewage sludge (MSS) is a waste product from the wastewater treatment process, containing substances that are hazardous to both the environment and humans (bacteria, pathogens, viruses). To dispose of these contaminants, MSS is thermally processed in specially designed installations. Thermal recycling technology is based on a fluidized bed, in which MSS is rapidly transformed at a temperature of at least 750 °C. Organic compounds are oxidized, gasified, and combusted. The exhaust fumes are emitted into the atmosphere. They also carry a load of pollutants, which can affect the air quality both on site and in the surroundings of the treatment plant. This paper presents measurements of air pollutant emissions and pollutant concentrations provided by the Group Sewage Treatment Plant in Łódź Itd. Łódź is a city located in Poland, in central Eastern Europe. The research covers the area of the wastewater treatment plant and its immediate surroundings within a radius of about 1.5 km. The data show the influence of the pandemic restrictions on the concentrations of gaseous substances, bacteria, fungi, and particulate matter on the state of air quality. Increased emissions of NOx (by 86%), PM10 (by 50%), HCl (by 37%), and SO2 (by 16%) were observed compared to the pre-COVID-19 period.