Author(s)

G. Genon & M. Vaccarono

Abstract

The city of Turin collects urban wastewater and sends it to an important treatment plant and from there it is discharged into the river Po. Some problems arise from the fact that wastewater flow rate corresponds to 6–8 m 3 /s, and this flow rate, which is normally high enough to guarantee a good degree of mixing, can be reduced in some periods of the year at the connection point to approximately the same previously mentioned numerical value because of the withdrawal of water to a plant where it is used for hydroelectric production. These aspects have been evaluated in different periods, before and after insertion of a specific section for the removal of biological nitrogen. Some evaluations have been performed on the basis of regular monitoring data concerning the plant effluent characteristics and the quality of the river; a statistical analysis was performed of the correlation of the two data sets, while taking different hydrological aspects of the river into account. A modellistic approach, which is useful to define the capacity of the river for removing the emitted nitrogen, has also been studied. As a final result it was, on the one hand, possible to verify the effective improvement in quality of the river in connection with the increased efficiency due to the treatment and, on the other, to verify the heavy limit on the quality of the river water due to the low dilution ratio at the connection point. Keywords: river quality, nitric nitrogen, denitrification, treatment plant, Po River, nitrogen removal, model, first order kinetics. 1 Introduction Most of the contamination of the Po River, downstream to the city of Turin, is caused by discharges from the municipal treatment plant which is managed by

Keywords

river quality, nitric nitrogen, denitrification, treatment plant, Po River, nitrogen removal, model, first order kinetics.