Volatile halocarbons in a drinking water supply system: forecasting contamination values and estimating health risk.

The network, which supplies drinking water to the city of Milan, has a number of sampling points, where the concentrations of several contaminants are periodically measured. From the time series of total volatile halocarbon (VHC) concentration values (in the ppb range) autoregressive models can be obtained for each sampling point. A suitable figure of merit is minimized, which depends on the backcast error and on the model order. The best model is then applied to predicting concentration one time step e.g., one year, forward. The experimental data pertain to the years 1981 to 1992. Predicted values are compared with the measured ones. The results obtained in 1991 contributed to avert a major emergency situation in Milan. Population exposure and the related health risk, based on the proportional dosage-response model, were also estimated. The excess casualty figure for Milan was computed. The method and the procedures described herewith may be used by public authorities to manage drinking water resources, whenever detailed models of the aquifer and of the network are not applicable.