###### Abstract
\begin{table}
\begin{tabular}{l l c} \hline \hline  & **Parameter** & **Unit** & **Value** \\ \hline \multicolumn{3}{l}{Physical properties} \\ \(\bullet\) & density & g/L & 502.2 \\ \(\bullet\) & humidity & \% & 79.5 (69.1 *) \\ \(\bullet\) & dry matter (DM) & g/L & 391.3 \\ \(\bullet\) & volatile substances & g/L & 371.7 \\ \(\bullet\) & volatile substances / dry matter & - & 0.95 (85.3 *) \\ \multicolumn{3}{l}{Ingredients} \\ \(\bullet\) & grains (with dimensions below 10 mm) & \% DM & 61.1 \\ \(\bullet\) & vegetables (less than 30 mm) & \% DM & 29.7 \\ \(\bullet\) & meat (less than 20 mm) & \% DM & 9.2 \\ \multicolumn{3}{l}{elementary analysis} \\ carbon, C & \% DM & 51.4 (46.78 *) \\ hydrogen, H & \% DM & 6.1 \\ oxygen, O & \% DM & 38.9 \\ nitrogen, N & \% DM & 3.5 (3.16 *) \\ phosphorus, P & \% DM & 0.52 * \\ sulfur, S & \% DM & 0.1 \\ C/N & & 14.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of food waste (data from Korea [17]; * data from USA [18]). \begin{table}
\begin{tabular}{c c} \hline \hline
**Restaurant Type** & **Fat Concentration (mg/L)** \\ \hline Chicken fryer & 120–6500 \\ Chinese & 76–1300 \\ Mexican & 96–1040 \\ Pub & 130–706 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of food waste [18]. data on the ratio of organic compounds and nitrogen compounds (C/N) in the catering waste. This ratio exceeds the value of 14, which proves that the waste could serve as a source of carbon in denitrification and dephosphatation processes for wastewater that is poor in organic compounds. This means that the surplus of the organic substrate present in the waste that exceeds the needs of denittifying bacteria (C/N ratio should range from 1 to 5) can be exploited in the dephosphatation process [28]. It is obvious that food waste from restaurants, bars, cafeterias, etc. should be collected. Strict law enforcement and the construction of an effective system are required for its collection. Due to the content of organic substances, it can be used after being fermented in VFA (Volatile Fatty Acid) generators as an external carbon source in the processes of denitrification and dephosphatation. The next rational solution is fermentation with sewage sludge, which would increase the quantity of biogas and the revenues of WWTPs [29]. Another solution could be the discharge of food waste to a biogas plant. As a result of the COVID-19 pandemic, restaurants, bars, hotels, and other gastronomic and accommodation businesses were closed many times in 2020 and 2021, limiting the production of meals and ground restaurant food waste. This affected the concentration of municipal wastewater. Studies on the quality of wastewater in the period before, during, and after the pandemic allowed the determination of the scale of the impact of restaurant wastewater on the quality of urban wastewater, especially in tourist towns. The aim of this study was to demonstrate the influence of pandemic lockdowns on wastewater quality, because of the discharge of less food waste into sewage pipes, and to determine the scale of the environmental problem of discharging food waste from restaurants to municipal sewage systems. The scope of the present study included determination of the load of catering waste discharged to the wastewater treatment plant, determination of the increase in sewage concentration resulting from the discharge of fragmented food waste, and determination of the scale of the increase in pollutant loads of organic compounds, suspended solids, and biogenes. In addition, the amount of methane that could be generated via anaerobic digestion from catering waste and the consumption of electricity in WWTPs for aerobic neutralization of organic compounds from food waste ground in FWDs were estimated.