10.4122/1.1000001281 Zawilski, M. Trends in the combined sewerage development in the past and their importance for the present infrastructure DTU Library, Technical University of Denmark (DTU) 2005 Combined sewerage history upgrading combined sewer overflows storage tanks Technical University of Lodz, Department of Environmental Engineering en Conference presentation 10.4122/1.1000001282 text/xml 1 A short story of the combined sewerage system origin and developing is presented. The system introduced as a modern solution about 150 years ago allowed for improvement of life conditions in many European cities. Designed for big flows, according to design storms and constructed in densely built-up urban areas, it reveals serious problems today. Increasing ratio of the sealed surfaces connected to the combined sewerage needs an urgent action in order to upgrade the whole system to meet the present regulations. An upgrade plan for a combined system has been elaborated in Lodz, Poland to be implemented in next few years. Technical problems connected with implementation of the plan in the present city infrastructure are discussed.