Unraveling the impact of COVID-19 lockdowns on Canadian municipal sewage†

The COVID-19 pandemic and resulting lockdowns have had significant impacts on various aspects of society, including municipal sewage. This study investigates changes in Canadian municipal sewage during COVID-19 lockdowns by examining influent flow rates at two wastewater treatment plants in Ontario, Canada. A thorough comparison of weekly patterns and daily average flow rates before and during lockdowns was conducted. The observed influent flow rates were also compared with predicted no-lockdown scenario data, which were generated by random forest models. The results showed that weekly patterns of influent flow exhibited differences before and during lockdowns, with the disappearance of a lag between weekdays and weekends in the morning and a less pronounced trend of lower influent flow rates on Friday and Saturday nights. There is less variability of influent flow rate during lockdowns compared to before lockdowns. Additionally, both plants experienced a decrease in influent flow rates during the lockdowns, and a spike in influent flow rates after the easing of provincial emergency state. These findings suggest that lockdown measures had an impact on water usage patterns in the region, leading to a decrease in the volume of sewage produced. This knowledge is beneficial for wastewater simulations and can be used to improve wastewater management strategies and inform policy decisions during times of crisis in the future.