MODERNISATION PROBLEMS OF THE SEWERAGE INFRASTRUCTURE IN A LARGE POLISH CITY

摘要

The combined sewerage system has been implemented in many European cities at the end of the 19th and in the beginning of the 20th century. It seemed to be advantageous to drain all kinds of sewage out of the city centre. In addition, urban rivers were simultaneously channelised as "unnecessary" watercourses inside the urban environment and were incorporated into the sewerage infrastructure as transport elements for disposal of stormwater and overflow wastewater. In the course of time, residential, commercial and industrial areas continued to develop within the city boundaries. Non-sealed (pervious) surfaces gradually disappeared, and the sealed impervious surfaces became larger and larger and smoother. As a consequence, the basic combined sewerage system revealed its shortcomings. Urban floods appeared more frequently, combined storm overflows also operate too frequently and wastewater treatment plants are overloaded during wet weather periods. At present, the City of Lodz, situated in central Poland, is a typical example of such problems.