Just as water ends its journey, so we also visited ZOV - Zagreb Wastewater, a company dealing with wastewater treatment in the city of Zagreb. Mrs. Astrid Werbolle introduced us to the plant's working methods and the use of purified water. We found out that water analyzes show how much and what kind of medicine residents use, when there are more patients with COVID-19, how settled sludge is used and energy is obtained by burning it.