Quantifizierungen von Grundwassereintritten in städtische Abwassersysteme mittels stabiler Isotope

Infiltration of groundwater into sewer systems increases the costs for wastewater treatment plant operators. This study explores groundwater infiltration to urban sewer systems in the city of Nuremberg (Germany). Measurements of stable isotopes at the water works, storage tanks, groundwater, and the sewage network were carried out to define input end members for mass balance calculations. Only minor differences in oxygen stable isotopes (δ¹⁸O_H2O) were found between most sewer and drinking water samples which ranged around (??9.5?±?0.1) ‰. One exception was water from a water works at Genderkingen that is situated about 80 km south of Nuremberg. Here, drinking water from bank filtrate of the Lech River had more negative δ¹⁸O_H2O values of ??11.4?‰. This difference of 1.5?‰ revealed maximum possible groundwater contributions of 41?% by mass balance calculations. To obtain more accurate results, we suggest testing the use of deuterium-enriched water (D₂O) added to the sewer system.