The Costa do Estoril sewerage system is one of the largest separate systems ever built in Portugal. Because of the quality of the environment in the region and the high level of touristic use, special care was given, in its design, to sulphide calculations.

This paper describes the application to the Costa do Estoril sewerage system of an integrated computer model for forecasting sulphides and hydrogen sulphide gas build-up along sewer atmospheres. The empirical sulphide prediction equations have been calibrated with experimental results obtained under a research project carried out in a gravity tributary and in a rising main located near the Costa do Estoril zone. The hydrogen sulphide gas concentrations along the main trunk line have been predicted according to an mathematical model described by Matos and Sousa.

The results of the model have been considered to be adequate for identifying critical reaches and for predicting the effects of corrective and preventive measures on the overall behaviour of the system.